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Preview: Journal of Bioluminescence and Chemiluminescence


Wiley Online Library : Luminescence

Published: 2017-09-01T00:00:00-05:00


Development of an optical sensor for chlortetracycline detection based on the fluorescence quenching of l-tryptophan


A simple and selective spectrofluorimetric method for the detection of chlortetracycline (CTC) was studied. In pH 7.4 buffer medium l-tryptophan (l-Trp), applied as the fluorescence probe, interacted with CTC resulting in fluorescence quenching of the probe. CTC was detected with maximum excitation and emission wavelengths at λex/λem = 275/350 nm. Notably, quenching of fluorescence intensities was positively proportional to the CTC concentration over the range of 0.65–30 μmol L−1 and the limit of detection was 0.2 μmol L−1. Effect of temperature shown in Stern−Volmer plots, absorption spectra and fluorescence lifetime determination, indicated that fluorescence quenching of l-Trp by CTC was mainly by static quenching. The proposed study used practical samples analysis satisfactorily.

A selective and sensitive fluorescent sensor for cysteine detection based on bi-8-carboxamidoquinoline derivative and Cu2+ complex


In this paper, a novel fluorescent sensor 1 for selective and sensitive detection of cysteine was developed based on a complex between bi-8-carboxamidoquinoline derivative ligand (L) and Cu2+. The interaction of Cu2+ with the ligand causes a dramatic fluorescence quenching most likely due to its high affinity towards Cu2+ and a ligand–metal charge transfer (LMCT) process. The in situ generated L–Cu2 complex was utilized as a chemosensing ensemble for cysteine. In the presence of cysteine, the fluorophore, L, was released from L–Cu2 complex because of the strong affinity of cysteine to Cu2+ via the Cu–S bond, leading to the fluorescence recovery of the ligand. The proposed displacement mechanism was confirmed by the results of mass spectrometry (MS) study. Under optimized conditions, the recovered fluorescence intensity is linear with cysteine concentrations in the range 1 × 10−6 mol/l to 8 × 10−6 mol/l. The detection limit for cysteine is 1.92 × 10−7 mol/l. Furthermore, the established method showed a highly sensitive and selective response to cysteine among the 20 fundamental α-amino acids used as the building blocks of proteins, after Ni2+ was used as a masking agent to eliminate the interference of His. The proposed sensor is applicable in monitoring cysteine in practical samples with good recovery rate.

Evaluation of chemical chaperones based on the monitoring of Bip promoter activity and visualization of extracellular vesicles by real-time bioluminescence imaging


It is known that endoplasmic reticulum (ER) stress in cells and extracellular vesicles (EVs) plays a significant role in cancer cells, therefore the evaluation of compounds that can regulate ER stress and EV secretion would be a suitable system for further screening and development of new drugs. In this study, we evaluated chemical chaperones derived from natural products based on monitoring Bip/GRP78 promoter activity during cancer cell growth, at the level of the single cell, by a bioluminescence microscopy system that had several advantages compared with fluorescence imaging. It was found that several chemical chaperones, such as ferulic acid (FA), silybin, and rutin, affected the activity. We visualized EVs from cancer cells using bioluminescence imaging and showed that several EVs could be observed when using CD63 fused with NanoLuc luciferase, which has a much smaller molecular weight and higher intensity than conventional firefly luciferase. We then examined the effects of the chemical chaperones on EVs from cancer cells by bioluminescence imaging and quantified the expression of CD63 in these EVs. It was found that the chemical chaperones examined in this study affected CD63 levels in EVs. These results showed that imaging at the level of the single cell using bioluminescence is a powerful tool and could be used to evaluate chemical chaperones and EVs from cancer cells. This approach may produce new information in this field when taken together with conventional and classical methods.

In situ biosensor for detection miRNA in living cells based on carbon nitride nanosheets with catalytic hairpin assembly amplification


In this study, an ultrasensitive fluorescence turn-on assay for in situ sensing of intracellular microRNA (miRNA) was developed utilizing a carbon nitride nanosheet (CNNS) and a catalytic hairpin assembly (CHA). The CHA showed favourable signal amplification for low-level biomarkers, and CNNS was an excellent candidate as a fluorescence quencher and gene vector. Moreover, the hairpin DNA of CHA could be adsorbed onto the surface of CNNS. An enzyme-free fluorescence biosensor for ultrasensitive sensing of intracellular miRNA in cells based on CHA and CNNS was designed. When faced with target miRNA, the fluorescence was recovered due to the miRNA, which could trigger cycling of CHA circuits, leading to the production of a marked enhanced fluorescence signal. Compared with traditional methods, the proposed method is convenient, with low cytotoxicity, and high specificity and ultrasensitivity. It has promising potential for detection low-level biomarkers.

Boron and nitrogen co-doped carbon dots as a sensitive fluorescent probe for the detection of curcumin


In this present study, a fluorescent probe was developed to detect curcumin, which is derived from the rhizomes of the turmeric. We used a simple and economical way to synthesize boron and nitrogen co-doped carbon dots (BNCDs) by microwave heating. The maximum emission wavelength of the BNCDs was 450 nm at an excitation wavelength of 360 nm. The as-prepared BNCDs were characterized by multiple analytical techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and infrared spectroscopy. The synthesized carbon nanoparticles had an average particle diameter of 4.23 nm. The BNCDs exhibited high sensitivity to the detection of curcumin at ambient conditions. The changes of BNCDs fluorescent intensity show a good linear relationship with the curcumin concentrations in the range 0.2–12.5 μM. This proposed method has been successfully applied to detect the curcumin in urine samples with the recoveries of 96.5–105.5%.

Comparison of molecular interactions of Ag2Te and CdTe quantum dots with human serum albumin by spectroscopic approaches


Ag2Te quantum dots (QDs) have attracted great attention in biological applications due to their superior photoluminescence qualities and good biocompatibility, but their potential biotoxicity at a molecular biology level has been rarely discussed. In order to better understand the basic behavior of Ag2Te QDs in biological systems and compare their biotoxicity to cadmium-containing QDs, a series of spectroscopic measurements was applied to reveal the molecular interactions of Ag2Te QDs and CdTe QDs with human serum albumin (HSA). Ag2Te QDs and CdTe QDs statically quenched the intrinsic fluorescence of HSA by electrostatic interactions, but Ag2Te QDs exhibited weaker quenching ability and weaker binding ability compared with CdTe QDs. Electrostatic interactions were the main binding forces and Sudlow's site I was the primary binding site during these binding interactions. Furthermore, micro-environmental and conformational variations of HSA were induced by their binding interactions with two QDs. Ag2Te QDs caused less secondary structural and conformational change in HSA, illustrating the lower potential biotoxicity risk of Ag2Te QDs. Our results systematically indicated the molecular binding mechanism of Ag2Te QDs with HSA, which provided important information for possible toxicity risk of these cadmium-free QDs to human health.

Enhancement of the luminescence properties of Sr3(PO4)2:Dy3+,Li+ white-light-emitting phosphors by charge compensator Li+ co-doping


Sr3(PO4)2:Dy3+,Li+ phosphors were prepared using a simple high temperature solid method for luminescence enhancement. The structures of the as-prepared samples agreed well with the standard phase of Sr3(PO4)2, even when Dy3+ and Li+ were introduced. Under ultraviolet excitation at 350 nm, the Sr3(PO4)2:Dy3+ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the 4F9/2  6H15/2 and 4F9/2  6H13/2 transitions of Dy3+ ions, respectively. A white light was fabricated using these two emissions from the Sr3(PO4)2:Dy3+ phosphors. The luminescence properties of Sr3(PO4)2:Dy3+,Li+ phosphors, including emission intensity and decay time, were improved remarkably with the addition of Li+ as the charge compensator, which would promote their application in near-ultraviolet excited white-light-emitting diodes.

Redox luminescence switch based on Mn2+-doped NaYF4:Yb,Er upconversion nanorods


An redox luminescence switch was developed for the sensing of glutathione (GSH), l-cysteine (Cys) or l-ascorbic acid (AA) based on redox reaction. The Mn2+-doped NaYF4:Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn2+ could be oxidized to MnO2 by KMnO4. Subsequently, when the AA, GSH or Cys was added into the MnO2 modified upconversion nanosystem, which could reduced MnO2 to Mn2+ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500–3.375 mM (R2 = 0.99) for AA, 0.6250–11.88 mM (R2 = 0.99) for GSH and 0.6250–9.375 mM (R2 = 0.99) for Cys, respectively.

Rapid and sensitive colorimetric detection of ascorbic acid in food based on the intrinsic oxidase-like activity of MnO2 nanosheets


In this paper, we report a colorimetric sensor for the rapid, selective detection of ascorbic acid (AA) in aqueous solutions. Single-layered MnO2 nanosheets were established as an artificial oxidase; consequently colorless 3,3´,5,5´-tetramethylbenzidine (TMB) was oxidized to a blue product (oxTMB), with increase in absorbance at 650 nm. The absorbance of the reaction system decreased after introduction AA, which reduced MnO2 into Mn2+. Under optimum conditions, a detection limit of 62.81 nM for AA in aqueous solutions could be achieved. The linear response range for AA was 0.25–30 μM with a correlation coefficient of 0.996. Importantly, the MnO2 nanosheet–TMB chromogenic reaction exhibited great selectivity as there was no interference from other metal ions, amino acids and small biological molecules. The proposed colorimetric sensing of AA could be applied for fruit, juice and pharmaceutical samples. Moreover, the proposed sensor showed satisfying performance, including low cost, easy preparation, rapid detection, and good biocompatibility.

Terbium (III) coordination polymer–copper (II) compound as fluorescent probe for time-resolved fluorescence ‘turn-on’ detection of hydrogen sulfide


With recognition of the biological importance of hydrogen sulfide (H2S), we present a simple and effective fluorescent probe for H2S using a Tb3+ coordination polymer–Cu2+ compound (DPA/Tb/G–Cu2+). Dipicolinic acid (DPA) and guanosine (G) can coordinate with Tb3+ to form a macromolecular coordination polymer (DPA/Tb/G). DPA/Tb/G specifically binds to Cu2+ in the presence of coexisting cations, and obvious fluorescence quenching is observed. The quenched fluorescence can be exclusively recovered upon the addition of sulfide, which is measured in the mode of time-resolved fluorescence. The fluorescence intensities of the DPA/Tb/G–Cu2+ compound enhance linearly with increasing sulfide concentrations from 1 to 30 μM. The detection limit for sulfide in aqueous solution is estimated to be 0.3 μM (at 3σ). The DPA/Tb/G–Cu2+ compound was successfully applied to sense H2S in human serum samples and exhibited a satisfactory result. It displays some desirable properties, such as fast detection procedure, high selectivity and excellent sensitivity. This method is very promising to be utilized for practical detection of H2S in biological and environmental samples.

Silica-modified luminescent LaPO4:Eu@LaPO4@SiO2 core/shell nanorods: Synthesis, structural and luminescent properties


Monoclinic-type tetragonal LaPO4:Eu (core) and LaPO4:Eu@LaPO4 (core/shell) nanorods (NRs) were successfully prepared using a urea-based co-precipitation process under ambient conditions. An amorphous silica layer was coated around the luminescent core/shell NRs via the sol–gel process to improve their solubility and colloidal stability in aqueous and non-aqueous media. The prepared nano-products were systematically characterized by X-ray diffraction pattern, transmission electron microscopy, energy dispersive X-ray analysis, and FTIR, UV/Vis, and photoluminescence spectroscopy to examine their phase purity, crystal phase, surface chemistry, solubility and luminescence characteristics. The length and diameter of the nano-products were in the range 80–120 nm and 10–15 nm, respectively. High solubility of the silica-modified core/shell/Si NRs was found for the aqueous medium. The luminescent core NRs exhibited characteristic excitation and emission transitions in the visible region that were greatly affected by surface growth of insulating LaPO4 and silica layers due to the multiphonon relaxation rate. Our luminescence spectral results clearly show a distinct difference in intensities for core, core/shell, and core/shell/Si NRs. Highly luminescent NRs with good solubility could be useful candidates for a variety of photonic-based biomedical applications.

Preliminary results on the photoluminescence and optically stimulated luminescence in Cu-doped and Ag-doped ZnB2X4 (B = Li, Na, K: X = Cl, Br) compounds


Photoluminescence, and optically stimulated luminescence in ZnB2X4 (B; Li,Na,K: X; Cl,Br) compounds doped with Cu+ or Ag+ were studied. Double humped emission bands attributable to the activators were observed in all the samples. The observed photoluminescence of Cu+ and Ag+ could be identified with 3d94s13d10 and 4d95s15d10 transitions respectively. The longer wavelength band (400–500 nm range) could be attributed to the Cu+ or Ag+ ion replacing alkali ion at the octahedral alkali site whereas short wavelength band (340–400 nm range) is attributed to a Cu or Ag ion at tetrahedral zinc site. The short wavelength band was found to be intense compared with long wavelength and gave an indication that most of the Cu or Ag ions prefered a tetrahedral Zn site compared with the octahedral alkali site. All the samples exhibit optically stimulated luminescence (OSL). The sensitivity was found to be lattice dependent. The lowest sensitivity of about 1% compared with Al2O3:C was observed in lithium lattices whereas highest the sensitivity of about 290% was observed in the case of Cu-doped ZnNa2Br4.

Synthesis, density functional theory calculations and luminescence of lanthanide complexes with 2,6-bis[(3-methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand


A pyridine-diacylhydrazone Schiff base ligand, L = 2,6-bis[(3-methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X-ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO3)2]NO3.xH2O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra-red (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO3)2]+ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT-IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.

A sensitive surface-enhanced Raman scattering method for chondroitin sulfate with Victoria blue 4R molecular probes in nanogold sol substrate


Using silver nanoparticles (AgNPs) as the nanocatalyst, l-cysteine rapidly reduced HAuCl4 to make a stable gold nanoparticle sol (Ag/AuNP) that had a high surface-enhanced Raman scattering (SERS) activity in the presence of Victoria blue 4R (VB4r) molecular probes. Under the selected conditions, chondroitin sulfate (Chs) reacted with the VB4r probes to form associated complexes that caused the SERS effect to decrease to 1618 cm−1. The decreased SERS intensity was linear to the Chs concentration in the range 3.1–500 ng/ml, with a detection limit of 1.0 ng/ml Chs. Accordingly, we established a simple and sensitive SERS quantitative analysis method to determine Chs in real samples, with a relative standard deviation of 1.47–3.16% and a recovery rate of 97.6–104.2%.

Effect of erbium ion concentration on structural and luminescence properties of lead borosilicate glasses for fiber amplifiers


This investigation reports, the effect of the concentration of erbium and lead ions on the physical, structural and optical properties of lead borosilicate glasses. These glasses were synthesized by the melt quench method. In the synthesis, the concentration of the erbium (Er3+) ion was varied in the order of 0.0, 0.1, 0.5, 1.0 and 2.0 mol% and lead (Pb2+) ion was varied in the order of 30, 29.9, 29.5, 29 and 28 mol%. The glasses were analyzed using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV–vis–NIR spectroscopy. From XRD, the amorphous nature of lead borosilicate glasses was confirmed. The functional groups which were present in the glasses have been identified by analyzing the FT-IR spectrum. From the absorption spectra, the oscillator strengths as well as the Judd–Ofelt (JO) intensity parameters were determined and compared with other hosts. The JO intensity parameters were further used to calculate certain radiative properties for the excited luminescent levels of Er3+ ion. From emission spectra, full width at half maxima (FWHM), stimulated emission cross-sections (σe) and certain lasing parameters were evaluated and compared with reference host glasses. The lifetimes of 4I13/2 excited level of Er3+ ion have also been recorded and analyzed. The calculated and experimental lifetimes were compared in terms of quantum efficiencies. From the photoluminescence analysis, the erbium doped lead borosilicate glasses well suited for optical fiber amplifiers are discussed.

Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers


A novel ratiometric fluorescence nanosensor for superoxide anion (O2•−) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb3+ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O2•−. The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O2•− demonstrated high sensitivity and selectivity with a wide linear response range (14 nM–10 μM) and a low detection limit (4.7 nM).

Luminescent properties of single-phase Ba2-x-1.5y-1.5zP2O7:xEu2+,yCe3+, zTb3+ phosphors for white light-emitting diode


A series of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors was synthesized via a co-precipitation method, then their crystal structure, quantum efficiency and luminescent properties were analyzed by XRD and FL, respectively. The results showed that these phosphors not only presented the excitation characteristics of Ba2P2O7:xEu2+,zTb3+, but also exhibited that of the Ba2P2O7:yCe3+,zTb3+ phosphor. Meanwhile, the tri-doped phosphor showed a stronger absorption around 320 nm in contrast with the Eu2+/Ce3+:Tb3+ co-doped phosphor. Not only can energy transfer from Ce3+Eu2+ be observed; the energy transfer mechanism from Eu2+ to Tb3+ is discussed in the tri-doped system. Ce3+ affects the luminescence properties of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors just as the sensitizer whereas Eu2+ is considered both as the sensitizer and the activator. The chromaticity coordinates of tri-doped phosphors excited at 320 nm stayed steadily in the bluish-white light region,and the emitted color and color temperature (CCT) of these phosphors could be tuned by adjusting the relative contents of Eu2+, Ce3+ and Tb3+. Hence, the single phase Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors may be considered as potential candidates for white light-emitting diodes.

Improved sensitivity of firefly luminescent intermediate-based protein interaction assay using Ser 440 mutant with lower adenylation activity


Protein–protein interaction assays are important in various fields including molecular biology, diagnostics, and drug screening. We recently designed a novel protein–protein interaction assay, the firefly luminescent intermediate-based protein interaction assay (FlimPIA), that exploited the unique reaction mechanism of firefly luciferase (Fluc). Using two mutant Flucs, each impaired with one of the two half-reactions, namely adenylation and subsequent oxidative luminescent steps, FlimPIA detects the proximity of the two proteins tethered to the mutant Flucs. Here, we found that introducing a mutation into a residue in the hinge region (S440) of the mutant with lowered adenylation activity (‘Acceptor’ Fluc) further improved the response of FlimPIA by lowering the residual adenylation activity. Mutants with bulkier residues showed greater inhibition, probably due to increased steric hindrance at the adenylation conformation. As a result, the FlimPIA with S440 L acceptor showed the best signal/background ratio for the detection of rapamycin-induced FKBP12–FRB interactions.

Investigation of the interaction of aurantio-obtusin with human serum albumin by spectroscopic and molecular docking methods


The interaction between human serum albumin (HSA) and aurantio-obtusin was investigated by spectroscopic techniques combined with molecular docking. The Stern–Volmer quenching constants (KSV) decreased from 8.56 × 105 M−1 to 5.13 × 105 M−1 with a rise in temperatures from 289 to 310 K, indicating that aurantio-obtusin produced a static quenching of the intrinsic fluorescence of HSA. Time-resolved fluorescence studies proved again that the static quenching mechanism was involved in the interaction. The sign and magnitude of the enthalpy change as well as the entropy change suggested involvement of hydrogen bonding and hydrophobic interaction in aurantio-obtusin–HSA complex formation. Aurantio-obtusin binding to HSA produced significant alterations in secondary structures of HSA, as revealed from the time-resolved fluorescence, Fourier transform infrared (FT-IR) spectroscopy, three-dimensional (3D) fluorescence and circular dichroism (CD) spectral results. Molecular docking study and site marker competitive experiment confirmed aurantio-obtusin bound to HSA at site I (subdomain IIA).

Preparation of carbon dot-based ratiometric fluorescent probes for cellular imaging from Curcuma longa


This work derived biocompatible and stable probes based on fluorescent nanoparticles (FNPs) from a natural source, Curcuma longa. The multi-color fluorescence emissions from carbonized Curcuma longa (C-FNPs) obtained through defined dehydration conditions are soluble in water and have a small particle size (~17 nm). The surface passivation with polyethylene glycol (PEG) capped with amine groups in FNPs (P-FNPs) generated a probe with a higher quantum yield and longer fluorescence lifetime than obtained with C-FNPs. The X-ray photoelectron spectroscopy and X-ray diffraction spectra confirmed the associated chemical moieties of C-FNPs and P-FNPs. Furthermore, the prepared material showed non-toxic effects with almost 100% cell viability, even at high concentrations. In conclusion, fluorescence sensors from natural sources may be useful for numerous biomedical research applications.

Characterization of a highly Al3+-selective fluorescence probe based on naphthalimide-Schiff base and its application to practical water samples


A new fluorescent Al3+-probe, N-allyl-4-[3,3′-((2-aminoethyl)azanediyl)-bis(N´-(2-hydroxybenzylidene)propanehy-drazide)]-1,8-naphthalimide (L), was designed and synthesized based on 1,8-naphthalimide. The probe L contains 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X-ray. L emission at 526 nm increased on addition of Al3+ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al3+ in ethanol/Tris–HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R2) of 0.99 was observed in the concentration range 2–10 μM. The binding constant and the detection limit of L for Al3+ were calculated to 2.6 × 104 M−1 and 0.34 μM, respectively. The results of experiments that including Job plot, ultraviolet–visible (UV–Vis) light titration, fluorescence titration, ESI-MS and 1H NMR titration, indicated a 1:1 stoichiometric complex between L and Al3+. L was highly effective in monitoring Al3+ in real-life Yellow River and tap water samples.

An electrochemiluminescent method for glutamate measurement in small microdialysate samples in asphyxiated young rats


Glutamate (Glu) quantification has been performed by a combination of intracerebral microdialysis through which the samples are obtained and analyzed by high performance liquid chromatography (HPLC); its measurement requires a large expenditure of time (15–30 min per sample) and special training. Therefore, an alternative method is presented here, based on the electrochemiluminescence produced by the use of an enzymatic reactor, containing glutamate-oxidase, mixed and incubated with microdialysate from dorsal striatum (DS) and prefrontal cortex (PFC) of young rats asphyxiated during the neonatal period, under a global asphyxia model in order to test this method. Using this approach, we found high extracellular Glu concentration in the DS of asphyxiated animals, but only during K+ stimulation, while in the PFC, only a delay in the rise of Glu after K+ stimulation was observed, without any difference in extracellular Glu content when compared with controls. This new method permitted a fast measurement of Glu in brain dialysate samples, it significantly reduces the cost of the analysis per sample, since only a single device and pump are needed without using columns and high pressure inside the system or complex hardware and software to control pumps, detector, fraction collector or any other peripheral used in HPLC.

A rhodamine-triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging


A rhodamine-based fluorescent chemodosimeter rhodamine hydrazide-triazole (RHT) tethered with a triazole moiety was developed for Cu2+ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu2+ among other metal ions. The addition of Cu2+ triggered a fluorescence emission of RHT by 384-fold (Φ = 0.33) based on a ring-opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu2+ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu2+ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu2+ in Chang liver cells by confocal fluorescence microscopy.

Investigation on the pH-independent photoluminescence emission from carbon dots impregnated on polymer matrix


Highly luminescent, polymer nanocomposite films based on poly(vinyl alcohol) (PVA), and monodispersed carbon dots (C-dots) derived from multiwalled carbon nanotubes (MWCNTs), as coatings on substrates as well as free standing ones are obtained via solution-based techniques. The synthesized films exhibit pH-independent photoluminescence (PL) emission, which is an advantageous property compared with the pH-dependent photoluminescence intensity variations, generally observed for the C-dots dispersed in aqueous solution. The synthesized C-dots and the nanocomposite films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), ultraviolet (UV) − visible spectroscopy and photoluminescence spectroscopy (PL) techniques. The TEM image provides clear evidence for the formation of C-dots of almost uniform shape and average size of about 8 nm, homogeneously dispersed in aqueous medium. The strong anchoring of C-dots within the polymer matrix can be confirmed from the XRD results. The FTIR spectral studies conclusively establish the presence of oxygen functional groups on the surfaces of the C-dots. The photoluminescence (PL) emission spectra of the nanocomposite films are broad, covering most part of the visible region. The PL spectra do not show any luminescence intensity variations, when the pH of the medium is changed from 1 to 11. The pH-independent luminescence, shown by these films offers ample scope for using them as coatings for designing diagnostic and imaging tools in bio medical applications. The non-toxic nature of these nanocomposite films has been established on the basis of cytotoxicity studies.

An OFF–ON–OFF type fluorescent probe based on a naphthalene derivative for Al3+ and F− ions and its biological application


A novel fluorescent probe-based naphthalene Schiff, 1-(C2-glucosyl-ylimino-methyl)-naphthalene-2-ol (L) was synthesized by coupling d-glucosamine hydrochloride with 2-hydroxy-1-naphthaldehyde. It exhibited excellent selectivity and highly sensitivity for Al3+ in ethanol with a strong fluorescence response, while other common metal ions such as Pb2+, Mg2+, Cu2+, Co2+, Ni2+, Cd2+, Fe2+, Mn2+, Hg2+, Li+, Na+, K+, Fe3+, Cr3+, Zn2+, Ag+, Ba2+ and Ca2+ did not cause the same fluorescence response. The probe selectively bound Al3+ with a binding constant (Ka) of 5.748 × 103 M−1 and a lowest detection limit (LOD) of 4.08 nM. Moreover, the study found that the fluorescence of the L − Al3+ complex could be quenched after addition of F− in the same medium, while other anions, including Cl−, Br−, I−, NO2−, NO3−, ClO4−, CO32−, HCO3−, SO42−, HSO4−, CH3COO−, PO43−, HPO42−, S2− and S2O32− had nearly no influence on probe behaviour. Binding of the [L − Al3+] complex to a F− anion was established by different fluorescence titration studies, with a detection limit of 3.2 nM in ethanol. The fluorescent probe was also successfully applied in the imaging detection of Al3+ and F− in living cells.

Zero and second-derivative synchronous fluorescence spectroscopy for the quantification of two non-classical β-lactams in pharmaceutical vials: Application to stability studies


The formation of metal chelates with various ligands may lead to the production of fluorescent chelates or enhance the fluorescence of the chelating agent. This paper describes two sensitive, selective and computer-solved methods, namely, zero order (SF) and second-derivative synchronous spectrofluorimetry (SDSFS) for nano-quantitation of two carbapenems; meropenem (MP) and ertapenem (EP). The methods are based on the chelation of MP with Tb3+ and EP with Zr4+ in buffered organic medium at pH 4.0 to produce fluorescent chelates. In the zero order method, the relative synchronous fluorescence intensity is measured at 327.0 nm at Δλ = 70.0 and 100.0 nm for MP and EP, respectively. The second method utilizes a second-derivative technique to enhance the method selectivity and emphasize a stability-indicating approach. The peak amplitudes (2D) of the second-derivative synchronous spectra were estimated to be 333.06 and 330.06 nm for MP and EP, respectively. The proposed synchronous spectrofluorimetric methods were validated according to the International Conference on Harmonization (ICH) guidelines and applied successfully for the analysis of MP and EP in pure forms, pharmaceutical vials and in synthetic mixtures with different degradants of both drugs. Under optimum conditions, the mole-ratio method was applied and the co-ordination ratios of MP–Tb3+ and EP–Zr4+chelates were found to be 1:1 and 1:3. The formation constants for the chelation complexes were evaluated using the Benesi–Hildebrand's equation; the free energy change (ΔG) was also calculated. The results indicated that EP–Zr4+ was more stable than the MP–Tb3+ chelate. Moreover, the developed methods were found to be selective and inexpensive for quantitative determination of both drugs in quality control laboratories at nano-levels.

A novel colorimetric fluorescence sensor for Fe3+ based on quinoline Schiff base


A novel fluorescent sensor bearing a quinoline and an anisidine moiety has been developed for highly selective detection of Fe3+, which shows photo-induced electron transfer (PET) behavior induced by Fe3+. Binding of Fe3+ to the sensor induced the electron of C = N group transfer from quinoline to iron, the result exhibits fluorescent enhancement. With the features of easy synthesis, simple structural skeleton and excellent sensing ability, the newly synthesized chemosensor also applied as a highly selective fluorescent probe in complex samples containing various competitive metal ions. The probe could fulfill various needs in biological and environmental fields.

A dual discrimination mode for improved specificity towards let-7a detection via a single-base mutated padlock probe-based exponential rolling circle amplification


MicroRNA (miRNA) family members are usually highly homologous sequences, and it is a challenging task to selectively detect one miRNA member from other family members in medical diagnosis. Here, we describe the design of a dual discrimination mode for improved specificity towards let-7a detection over the other members of the let-7 family, in which an intentional base mutation was introduced into the padlock probe of an exponential rolling circle amplification. The inherent discrimination power of the padlock probe and the introduced base mutation constituted a dual discrimination mode, which provided enhanced specificity for let-7a, even over single-base mismatched family sequences. Furthermore, the assay enabled the quantitative detection of let-7a in a dynamic range from 200 amol to 100 fmol. This technique has also been successfully applied to real small RNA samples extracted from human lung cancers. For the first time, through intentionally mutating one base on the padlock probe of the exponential rolling circle amplification (RCA), we improved the discrimination capability for let-7 family members, while maintaining adequate sensitivity. Overall, this dual discrimination mode and the high amplification strategy have the potential to be extended to other short, but highly homologous, miRNA sequences.

Life prediction for a vacuum fluorescent display based on two improved models using the three-parameter Weibull right approximation method


To obtain precise life information for vacuum fluorescent displays (VFDs), luminance degradation data for VFDs were collected from a group of normal life tests. Instead of exponential function, the three-parameter Weibull right approximation method (TPWRAM) was applied to describe the luminance degradation path of optoelectronic products, and two improved models were established. One of these models calculated the average life by fitting average luminance degradation data, and the other model obtained VFD life by combining the approximation method with luminance degradation test data from each individual sample. The results indicated that the test design under normal working stress was appropriate, and the selection of censored test data was simple. The two models improved by TPWRAM both revealed the luminance decaying law for VFD, and the pseudo failure time was accurately extrapolated. It was further confirmed by comparing relative error that using the second model gave a more accurate prediction of VFD life. The improved models in this study can provide technical references for researchers and manufacturers in aspects of life prediction methodology for its development.

Enhanced green emissions of Er3+/Yb3+ co-doped Gd2(MoO4)3 by co-excited up-conversion processes


Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio-imaging, photovoltaics and temperature sensing. The green emissions of Gd2(MoO4)3:Er3+/Yb3+ powder upon co-excitation with 980 and 808 nm lasers were investigated in this paper. Distinct enhancement of green emissions was observed compared with single laser excitation. Based on the energy level structure of Er3+, the enhancement mechanism was discussed. Moreover, the result of temperature-dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co-excited up-conversion processes. In addition, the same enhancement of green emissions was also observed in Gd2(MoO4)3:Er3+ powder and NaYF4:Er3+/Yb3+ powder.

Selective spectrofluorimetric method for determination of Lisinopril in pharmaceutical preparations and in presence of hydrochlorothiazide: Application to content uniformity testing


A novel sensitive and cost-effective spectrofluorimetric method has been developed and validated for determination of lisinopril (an angiotensin converting enzyme inhibitor) in its pure form and pharmaceutical preparations. The method is based on the reaction of the drug with ninhydrin and phenylacetaldehyde in buffered medium (pH 7.0) to form a highly fluorescent product measured at 460 nm after excitation at 390 nm. Different experimental parameters were optimized and calibration curve was constructed. The fluorescence-concentration relationship was linear in the range of 0.15–4.0 μg mL−1. The calculated Limit of detection (LOD) and Limit of quantitation (LOQ) were 0.04 and 0.12 μg mL−1, respectively. The method was successfully applied for the analysis of pharmaceutical preparations containing the studied drug either alone or co-formulated with hydrochlorothiazide. The obtained results were in agreement with those of the reported method in respect to accuracy and precession. Moreover, the method was applied content uniformity testing according to United States Pharmacopeia (USP) guidelines.

‘Turn-on’ fluorescent chemosensors based on naphthaldehyde-2-pyridinehydrazone compounds for the detection of zinc ion in water at neutral pH


A series of naphthaldehyde-2-pyridinehydrazone derivatives were discovered to display interesting ‘turn-on’ fluorescence response to Zn2+ in 99% water/DMSO (v/v) at pH 7.0. Mechanism study indicated that different substituent groups in the naphthaldehyde moiety exhibited significant influence on the detection of Zn2+. The electron rich group resulted in longer fluorescence wavelengths but smaller fluorescence enhancement for Zn2+. Among these compounds, 1 showed the highest fluorescence enhancement of 19-fold with the lowest detection limit of 0.17 μmol/L toward Zn2+. The corresponding linear range was at least from 0.6 to 6.0 μmol/L. Significantly, 1 showed an excellent selectivity toward Zn2+ over other metal ions including Cd2+.

Design and synthesis of the BODIPY–BSA complex for biological applications


A quinoxaline-functionalized styryl–BODIPY derivative (S1) was synthesized by microwave-assisted Knoevenagel condensation. It exhibited fluorescence enhancement upon micro-encapsulation into the hydrophobic cavity of bovine serum albumin (BSA). The S1–BSA complex was characterized systematically using ultraviolet (UV)–visible absorption, fluorescence emission, kinetics, circular dichroism and time-resolved lifetime measurements. The binding nature of BSA towards S1 was strong, and was found to be stable over a period of days. The studies showed that the S1–BSA complex could be used as a new biomaterial for fluorescence-based high-throughput assay for kinase enzymes.

The luminescence properties of Sr2–1.5x−1.5yP2O7:xDy3+,yCe3+ phosphor for near-UV-based white LEDs synthesized by a chemical co-precipitation method


A series of Sr2P2O7:Dy3+, Sr2P2O7:Ce3+ and Sr2P2O7:Dy3+,Ce3+ phosphors was synthesized via the one-step calcination process for the precursors prepared by co-precipitation methods. The phases, morphology, quantum efficiency and photoluminescence properties of the obtained phosphors were characterized systematically. These results show that the near-spherical particles prepared through calcining the precursors by means of ammonium dibasic phosphate co-precipitation (method 3) have the smallest particle size and strongest emission intensity among the three methods in the paper. With Dy3+ concentration increasing in Sr2P2O7:Dy3+ phosphors, the luminescence intensity first increases, reaches maximum, and then decreases. A similar trend was followed by Sr2P2O7:Ce3+ with Ce3+concentration increasing. A successful attempt was made to initiate the energy transfer mechanism from Ce3+ to Dy3+ in the host lattice and an overlap between the emission band of Ce3+ and the excitation band of Dy3+ indicated that the Ce3+  Dy3+ energy transfer may indeed exist. It is clear that the photoluminescence intensity of Dy3+ as well as the quantum efficiency of the phosphor can be enhanced markedly by co-doping Ce3+. Sr2P2O7:Dy3+,Ce3+ has its (CIE) chromaticity coordinates in the bluish-white-light region, near the standard illuminant D65. The CIE 1913 chromaticity coordinates of Sr2P2O7:Dy3+ phosphors fall in the white-light region, and are adjacent to the ideal white-light coordinates. In addition, the colour temperature and colour tone of Sr2P2O7:Dy3+ could be adjusted by changing the relative concentration of Dy3+. In short, Sr2P2O7:Dy3+ can be a promising single-phased white-light emitting phosphor for near-UV (NUV) w-LEDs.

Fluorescence sensing of dichlorvos pesticide by the luminescent Tb(III)-3-ally-salicylohydrazide probe


A fluorescent probe was developed and characterized, it consisted of terbium(III) with 3-ally-salicylohydrazide in ethanol, in which the 1:2 [Tb3+:S1] molar ratio was the best stoichiometric ratio for the probe. The ligand 3-ally-salicylohydrazide (S1) was synthesized, then was confirmed by IR, CHN, LC–MS and 1H NMR. The sensitivity of the probe's fluorescence spectra towards the presence of eight organophosphorus pesticides in ethanolic solution was studied, in which the probe showed marked sensitivity towards dichlorvos pesticide. A tangible enhancement of the probe's fluorescence intensity was observed as a consequence of the gradual addition of dichlorvos pesticide. The calculated limit of detection (LOD) was 1.183 μM and limit of quantitation (LOQ) was 3.94 μM. Further characterization of the nature of forces acting in the interaction of the probe with dichlorvos was performed by calculation of binding constants at different temperatures according to the Benesi − Hildebrand equation, and the thermodynamic parameters ΔH, ΔS and ΔG. In order to assess the analytical applicability of the method, the influence of various potentially interfering anion and cations that naturally occur in water and soil were calculated.

Synthesis and luminescence of novel near-infrared emitting BaZrSi3O9:Cr3+ phosphors


The BaZrSi3O9:Cr3+ phosphors were prepared by a high temperature solid state method. Their structures were confirmed with XRD and their luminescence properties were investigated. Under excitation at 455 nm, BaZrSi3O9:Cr3+ phosphors exhibited a broad near infrared emission band peaked at 800 nm, which was assigned to the 4T24A2 transition of Cr3+. The near infrared emission intensity reached a maximum at Cr3+ concentration of 0.7%. There was a concentration quenching phenomenon of Cr3+ in BaZrSi3O9 matrix and the corresponding concentration quenching mechanism was investigated. With efficient near infrared emission in the range of 700–1000 nm, BaZrSi3O9:Cr3+ phosphors may find applications in solar energy conversion.

A selective colorimetric chemosensor for Fe3+


Two simple colorimetric receptors PS and PP (thiophene and pyridine appended derivative) were prepared and their cation sensing properties were investigated. Receptors PS and PP displayed a selective colorimetric change (from colorless to orange) upon binding to Fe3+ in MeOH solution. The association constants for receptors PS–Fe3+ and PP–Fe3+ in MeOH were determined to be 1.15 × 106 and 4.31 × 106 M−1, respectively, using Hill plots. The detection limits of PS and PP were 490.7 ppm and 393.7 ppm, respectively.

Fluorescent carbon nanoparticles obtained from charcoal via green methods and their application for sensing Fe3+ in an aqueous medium


Two green methods (microwave and hydrothermal) were employed for the preparation of water dispersible fluorescent carbon nanoparticles (CNPs) from activated charcoal. Microwave and hydrothermally synthesized carbon nanoparticles, (MW-CNPs) and (HT-CNPs), respectively were characterized by microscopic and spectroscopic techniques. A detailed study of their fluorescence characteristics was made. MW-CNPs and HT-CNPs were tested for metal ion selectivity in aqueous medium. MW-CNPs showed selectivity for Fe3+ among the tested metal ions and important studies such as for interference, linear range and limit of detection were carried out. The application of MW-CNPs for detection of Fe3+ in water was demonstrated.

Dual-labeled chemiluminescence enzyme immunoassay for simultaneous measurement of total prostate specific antigen (TPSA) and free prostate specific antigen (FPSA)


The specificity for early diagnostic of prostate-specific antigen (PSA) is low because the current technology mostly allows the detection of only one biomarker at one time. In this work, a dual-labeled chemiluminescence enzyme immunoassay (CLEIA) for simultaneous measurement of total PSA (TPSA) and free PSA (FPSA) was proposed. Anti-PSA McAb (Mab1) was immobilized on a microplate as the solid phase, horseradish peroxidase (HRP)-labeled anti-TPSA monoclonal antibody (McAb2) and alkaline phosphatase (ALP)-labeled anti-FPSA McAb3 were used as detection antibodies. Two chemiluminescence reactions of HRP with luminol and ALP with 4-methoxy-4-(3-phosphate-phenyl)-spiro-(1,2-dioxetane-3,2′-adamantane) (AMPPD) were used as the signal detecting system. Based on a sandwich model, the amount of FPSA and TPSA could be determined simultaneously. The effects of several physico-chemical parameters were studied and optimized. Cross-reactivities of six common tumor markers in serum were studied. The proposed method presented the sensitivity of 0.03 ng ml−1 and 0.05 ng ml−1 for FPSA and TPSA respectively, with low cross-reactivities. Compared with the results from commercial chemiluminescent kits there was good correlation, indicating that this established method could be used to simultaneously to measure the concentrations of FPSA and TPSA in one serum sample and also could greatly facilitate the early diagnosis for PCa in clinical practice.

Contribution to the reduction-induced fluorescence enhancement of natural organic matter: Aromatic ketones outweigh quinones


This work involves the comparison of the fluorescence excitation − emission matrices of different low-molecular-weight carbonyl compounds and natural organic matter (NOM). The aim is to determine if quinone or aromatic ketone groups are more responsible for the reduction-induced fluorescence enhancement of NOM. After reduction, the aromatic ketones showed a significantly greater fluorescence change than the quinones, proving that the former play a more important role. Further analysis of the fluorescence of the NOM samples after re-oxidization by oxygen with a Cu2+ catalyst, provided additional reliable evidence in support of the dominant role of aromatic ketones in the fluorescence change. This work demonstrates that aromatic ketone moieties should be given more attention when considering the physicochemical properties of NOM and related environmental processes.

Eu3+-doped polystyrene and polyvinylidene fluoride nanofibers made by electrospinning for photoluminescent fabric designing


Eu3+-doped polystyrene and polyvinylidene fluoride (PVDF/Eu3+ and PS/Eu3+) nanofibers were made using electrospinning. These fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDX) and photoluminescence (PL). Spectral analysis of PVDF/Eu3+ and PS/Eu3+ nanofibers was based on their emission spectra. A bright red emission was noticed from Eu3+ that was assigned to the hypersensitive 5D0  7F2 transition. The enhanced intensity ratios of 5D0  7F2 to 5D0  7F1 transitions in the nanofibers indicated a more polarized chemical environment for the Eu3+ ions and greater hypersensitivity for the 5D0  7F2 transition, which showed the potential for application in various polymer optoelectronic devices. The Eu3+-doped polymer (PVDF/Eu3+ and PS/Eu3+) nanofibers are suitable for the photoluminescent white light fabric design of smart textiles. This paper focuses on the potential application of smart fabrics to address challenges in human life.

A simply synthesized biphenyl substituted piperidin-4-one for the fluorescence chemosensing of Cd2+


Ion-induced change in fluorescence is a straight-forward method for detection of toxic metal ions showing immediate response. Cadmium ions are toxic to the environment. We report in this paper a piperidine-4-one-based fluorescent chemosensor of Cd2+ ions, designed and synthesized by a simple method. The compound is characterized using infra-red (IR) and 1H–NMR spectral techniques. The chemosensor showed Cd2+ ion selectivity and sensitivity in aqueous solution. The stoichiometry and the binding constants were determined using fluorescence spectroscopy. Piperidine-4-one shows a 1:1 stoichiometric binding to Cd2+. The limit of detection of Cd2+ was reported.

Carbazole–azine based fluorescence ‘off–on’ sensor for selective detection of Cu2+ and its live cell imaging


A new carbazole–azine based fluorescent sensor was synthesized and characterized. The selectivity of the sensor for Cu2+ over other counter ions in a dimethyl sulfoxide/H2O mixture was shown through enhancement in fluorescence – an off to on transformation. The specificity of the probe towards Cu2+ was evident in ultraviolet/visible, fluorescence, Fourier transform infrared and mass studies. Application of the probe in the cell imaging and cytotoxicity of living cells is illustrated.

Photoluminescence, cathodoluminescence and thermal stability of Sm3+-activated Sr3La(VO4)3 red-emitting phosphors


A series of Sm3+-activated Sr3La(VO4)3 phosphors were synthesized by a facile sol-gel method. X-ray diffraction patterns and photoluminescence (PL)/cathodoluminescence (CL) spectra as well as PL decay curves were employed to characterize the obtained samples. Upon 402 nm light excitation, the characteristic emissions of Sm3+ ions corresponding to 4G5/26HJ transitions were observed in all the as-prepared products. The PL emission intensity was increased with increase in Sm3+ ion concentration, while concentration quenching occurred when the doping concentration was over 4 mol%. The non-radiative energy transfer mechanism for concentration quenching of Sm3+ ions was dominated by dipole–dipole interaction and the critical distance was around 21.59 Å. Furthermore, temperature-dependent PL emission spectra revealed that the obtained phosphors possessed good thermal stability with an activation energy of 0.19 eV. In addition, the CL spectra of the samples were almost the same as the PL spectra, and the CL emission intensity showed a tendency to increase with increase in accelerating voltage and filament current. These results suggest that the Sm3+-activated Sr3La(VO4)3 phosphors with good color coordinates, high color purity and superior thermal stability may be a potential candidate for applications in white light-emitting diodes and field-emission displays as red-emitting phosphors.

Chemiluminescence selectivity enhancement in the on-chip Ru(bpy)32+ system: The potential role of buffer type and pH in the determination of hydrochlorothiazide in combined formulations and human plasma


A simple and highly selective on-chip Ru(bpy)32+–oxidant chemiluminescence (CL) approach for estimation of a diuretic drug, hydrochlorothiazide (HCZ), in biological fluids was realized in the presence of other fixed-dose combination drugs by manipulating simultaneously the method of active species (Ru(bpy)33+) production and type of carrier buffer with pH used for the CL reaction. Chemical oxidation processes involved in the Ru(bpy)32+–Ce(IV) CL system have been successfully miniaturised in this study using a microfabricated device to generate Ru(bpy)33+ instantaneously. The proposed system was then screened using HCZ and other drugs in the presence of various buffers and pH to explore the difference in CL emission. Ammonium formate buffer (0.15 M) at pH 4.5 exhibited excellent selectivity towards HCZ when Ru(bpy)33+ was produced by chemical oxidation using Ce(IV). The newly developed conditions do not involve any kind of prior separation or isolation procedure to remove other combination therapy drugs in formulation and biological samples. The method under fully optimised conditions exhibited wide linearity over the concentration range 0.5–1000 ng ml−1 and low detection and quantification limits of 0.13 and 0.47 ng ml−1 respectively for HCZ. Acceptable levels of recoveries were obtained for HCZ from human plasma using the proposed method (98.9–100.8%) in the presence of other antihypertensive combination therapy drugs. This study postulates that such miniaturised devices may find applications especially for on-site analysis, such as doping control examinations.

Spectroscopic and molecular docking study on the structure–affinity relationship and mechanism in the interaction of genistein and its derivatives with bovine serum albumin


In this paper, the interaction of genistein (GEN) and its four derivatives (GEN1–4) with bovine serum albumin (BSA) were investigated by ultraviolet–visible absorption spectra, fluorescence, synchronous fluorescence, three-dimensional fluorescence spectroscopy, circular dichroism and molecular docking techniques. The experimental results showed that the intrinsic fluorescence of BSA was quenched by genisteins and was due to the formation of a genisteins–BSA complex. The quenching constant, binding constants, binding sites, intermolecular distances and thermodynamic properties were calculated at 298 K, 306 K and 310 K. Site marker competitive experiments indicated that the binding site of genisteins to BSA was mainly located in subdomain IIA. The conformational investigation showed that the presence of 0020 genisteins led to changes in the secondary structure of BSA and induced the slight unfolding of protein polypeptides, which confirmed some micro-environmental and conformational changes of BSA molecules. Furthermore, the binding affinity decreased in the order GEN1 > GEN > GEN4 > GEN3 > GEN2, which revealed that different type and position of substituents of genistein significantly influenced the affinity of compounds to BSA. The number of hydroxyl groups on the ring A was the most important factor because increasing the hydroxyl groups on ring A clearly enhanced the binding affinity. However, trifluoromethylation did not much affect the affinity, alkylation, esterification and difluoromethylation slightly enhanced the binding affinity. The results obtained herein will provide valuable information about the pharmacokinetics at a molecular level and be a useful guideline for the further design of much more suitable genistein derivatives.

Structural and luminescent studies of erbium-doped CaZrO3 green-emitting nanophosphors


Erbium (Er) (0.5, 1.0 and 1.5 wt%)-doped CaZrO3 nanophosphors were synthesized by the sol–gel method using poly(vinyl alcohol) as the chelating agent. Their structural and photoluminescence properties were studied using X-ray diffraction (XRD), field emission scanning electron microscopy–energy dispersive spectroscopy (FESEM-EDS), transmission electron microscopy (TEM), photoluminescence and Fourier transform infrared spectroscopy (FTIR). The XRD patterns of the samples confirm that nanoscale crystallite sizes. Agglomeration of the samples was observed using field emission scanning electron microscopy images. Energy dispersive spectroscopy measurements confirmed the existence of Ca, Zr, O and Er in the samples. Average particle sizes for the samples were calculated from transmission electron microscopy images. FTIR spectra clearly show characteristic absorption bands related to the metal oxides, as well as some other organic molecules. The photoluminescence spectra show bands in the green region. The Commission International de l'Eclairage coordinates were calculated and found to be in green region.

Spectral investigations on Eu3+,Sm3+-doped and Sm3+/Eu3+ co-doped potassium-fluoro-phosphate glass emitting intense orange-red for lighting applications


Potassium fluoro-phosphate (KFP) glass singly doped with different concentrations of europium (Eu3+) or samarium (Sm3+) or co-doped (Sm3+/Eu3+) was prepared, and their luminescence spectra were investigated. The phase composition of the product was verified by X-ray diffraction analysis. Optical transition properties of Eu3+ in the studied potassium phosphate glass were evaluated in the framework of the Judd–Ofelt theory. The radiative transition rates (AR), fluorescence branching ratios (β), stimulated emission cross-sections (σe) and lifetimes (τexp) for certain transitions or levels were evaluated. Red emission of Eu3+ was exhibited mainly by the 5D07F2 transition located at 612 nm. Concentration quenching and energy transfer were observed from fluorescence spectra and decay curves, respectively. It was found that the lifetimes of the 5D0 level increased with increase in concentration and then decreased. By co-doping with Sm3+, energy transfer from Sm3+ to Eu3+ occurred and contributed to the enhancement in emission intensity. Intense orange-red light emission was obtained upon sensitizing with Sm3+ in KFP glass. This approach shows significant promise for use in reddish-orange lighting applications. The optimized properties of the Sm3+/Eu3+ co-doped potassium phosphate glass might be promising for optical materials.

One-pot synthesis of fluorescent nitrogen-doped carbon dots with good biocompatibility for cell labeling


Here we report an easy and economical hydrothermal carbonization approach to synthesize the fluorescent nitrogen-doped carbon dots (N-CDs) that was developed using citric acid and triethanolamine as the precursors. The synthesis conditions were optimized to obtain the N-CDs with superior fluorescence performances. The as-prepared N-CDs are monodispersed sphere nanoparticles with good water solubility, and exhibited strong fluorescence, favourable photostability and excitation wavelength-dependent behavior. Furthermore, the in vitro cytotoxicity and cellular labeling of N-CDs were investigated using the rat glomerular mesangial cells. The results showed the N-CDs have more inconspicuous cytotoxicity and better biosafety in comparison with ZnSe quantum dots, although both targeted the cells successfully. Considering their admirable photostability, low toxicity and good compatibility, the as-obtained N-CDs could have potential applications in biosensors, cellular imaging, and other fields.

A tricorn-rhodamine fluorescent chemosensor for detection of Co2+ ions


A novel chemosensor TrisRh based on tris(2-aminoethyl)amine and rhodamine 6G is designed and synthesized as a fluorescence turn-on probe for Co2+ ions that is paramagnetic with a property of quenching fluorescence. Rhodamine spirolactam forms are nonfluorescent, whereas, ring-opening of corresponding spirocyclic induced by Co2+ results in strong fluorescence emission. Upon the addition of Co2+ ions, TrisRh can display significant enhancements in absorbance and fluorescence intensity as well as evident colorific transformation, which can be perceived by the naked eye. The association stoichiometry of TrisRh to Co2+ ions was inferred to be 1:1 through Job's plot and electrospray ionization mass spectrometry analysis. The binding model was speculated from Fourier transform infrared spectra and 1H–nuclear magnetic resonance technologies. Significantly, the limit of detection was determined to be as low as 1.22 nmol. Furthermore, TrisRh can exhibit robust anti-jamming ability against other interference metal ions.

Resonance Rayleigh scattering methods for the determination of chitosan with Congo red as probe


Two methods were presented for the sensitive and selective determination of chitosan (CTS) with Congo red (CR) as probe based on resonance Rayleigh scattering (RRS) intensities in health products. In weakly acidic buffer solution, the binding of CTS to CR, could result in the enhancement of the RRS intensities. Moreover, after adding OP emulsifier (octyl-phenyl polyoxyethylene ether) to the system, the RRS intensities showed more significantly enhancement. The maximum RRS signals for the CTS–CR system and the CTS–CR–OP system were located at 380 nm and 376 nm, respectively. Under optimum experimental conditions, the increased RRS intensities (ΔI) of these two systems were linear to CTS concentration in the range of 0.40–8.00 μg/ml and 0.05–1.00 μg/ml. Their limits of detection (LOD) were 44.81 ng/ml and 6.99 ng/ml, which indicated that the latter system was more sensitive than the former. In this work, the optimum conditions and the effects of some foreign substances on the determination were studied. In addition, the effect of the molecular weight of CTS and the reasons for the enhancement of resonance light scattering were discussed. Finally, these two methods were applied to the determination of chitosan in health products with satisfactory results.

A switch-off fluorescence probe towards Pb(II) and cu(II) ions based on a calix[4]pyrrole bearing amino-quinoline group


A new fluorescence receptor calix[4]pyrrole-N-(quinoline-8-yl) acetamide (CAMQ) containing a pyrrolic ring connected via the meso-position was synthesized, purified and characterized by elemental analysis, NMR and mass spectroscopy. This compound was examined for its fluorescence properties towards different metal ions e.g. Ag(I), Hg(II), Co(II), Ca(II), Ni(II), Zn(II), Cr(II), Ba(II), Fe(II), Cu(II), Pb(II)and Mg(II) ions by spectrophotometry and spectrofluorometry. It was concluded that the compound (CAMQ) possessed significantly enhanced selectivity for Pb(II) and Cu(II) ions in dimethyl sulfoxide (DMSO) even at very low concentrations (1 μM). It exhibit ‘turn-on’ fluorescence when exposed to Pb(II) and Cu(II) and did so in preference to other metal ions. The binding constants, stoichiometry and quantum yields have been determined. The quenching mechanism was assessed using the Stern–Volmer equation and was also discussed.

A colorimetric and fluorescent chemosensor for selective detection of Cu2+ based on a new diarylethene with a benzophenone hydrazone unit


A new photochromic diarylethene based on benzophenone hydrazone has been synthesized. Its photochromic and fluorescent properties changed upon alternating irradiation with UV/Vis light and adding Cu2+/EDTA in methanol, which showed that the diarylethene could be served as a colorimetric and fluorescent chemosensor for selective detection of Cu2+ based on internal charge transfer processes. The colorimetric and turn-off fluorescent selective detection of Cu2+ was attributed to the 2:1 complex of the diarylethene and Cu2+. The binding constant (Ka) was 1.53 × 104 L mol−1 and the limit of detection of the diarylethene for Cu2+ was calculated to be 1.45 × 10−6 mol L−1. In addition, the metal-responsive photochromic behavior of diarylethene was applied successfully to the construction of a molecular logic circuit.

Effect of cooling rate on the microstructure and luminescence properties of Sr2MgSi2O7:Eu2+,Dy3+ materials


Sr2MgSi2O7:Eu2+,Dy3+ long afterglow materials were prepared by a high-temperature solid-state reaction method with different cooling rates. The cooling rate had a slight effect on X-ray diffraction patterns and photoluminescence performance, but significantly modified the grain boundaries and long afterglow properties of the Sr2MgSi2O7:Eu2+,Dy3+ materials. When the cooling rate was 1°C/min, grains remained intact with clear grain boundaries. As the cooling rate increased from 1°C/min to 5°C/min, some grain boundaries became indistinguishable. The afterglow properties were optimized, presenting best performance at the cooling rate of 3°C/min. The trap state was investigated and illustrated through thermoluminescence curves. The depths of the traps of all the samples were unchanged, whereas densities changed to a large extent, leading to different afterglow properties. The retrapping process is discussed based on the afterglow curves.

A new Schiff base as a turn-off fluorescent sensor for Cu2+ and its photophysical properties


A new Schiff base receptor 1 was synthesized and its photophysical properties were investigated by absorption, emission and excitation techniques. Furthermore, its chromogenic and fluorogenic sensing abilities towards various metal ions were examined. Receptor 1 selectively detects Cu2+ ion through fluorescence quenching and detection was not inhibited in the presence of other metal ions. From fluorescence titration, the limit of detection of receptor 1 as a fluorescent ‘turn-off’ sensor for the analysis of Cu2+ was estimated to be 0.35 μM.

Photoluminescence properties of Ca2Al2O5:RE3+ (RE = Eu, Dy and Tb) phosphors for solid state lighting


Ca2Al2O5:Eu3+, Ca2Al2O5:Dy3+ and Ca2Al2O5:Tb3+ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X-ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca2Al2O5:Eu3+ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to 5D0  7F1 and 5D0  7F2 transitions. Dy3+-doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca2Al2O5:Tb3+ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu3+ and Dy3+phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate-based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies.

A combined spectroscopic and TDDFT investigation of the solute-solvent interactions of two coumarin derivatives


The UV/Vis absorption and fluorescence characteristics of 3-cyano-7-hydroxycoumarin [CHC] and 7-amino-4-methyl-3-coumarinylacetic acid [AMCA-H] were studied at room temperature in several neat solvents and binary solvent mixtures of 1,4-dioxane/acetonitrile. The effects of solvent on the spectral properties are analyzed using single and multi-parameter solvent polarity scales. Both general solute/solvent interactions and hydrogen bond interactions are operative in these systems. The solvation of CHC and AMCA-H dyes in 1,4-dioxane/acetonitrile solvent mixtures has been studied. The solutes CHC and AMCA-H are preferentially solvated by acetonitrile and a synergistic effect is observed for both molecules in dioxane/acetonitrile solvent mixtures. In addition, using the solvatochromic method the ground- and the excited-state dipole moments of both the dyes were calculated. The ground- and excited-state dipole moments, absorption and emission maxima and HOMO–LUMO gap were also estimated theoretically using B3LYP/6–311+ G (d,p) level of theory in the gaseous phase, dioxane and acetonitrile solvents. Furthermore, changes in dipole moment values were also calculated using the variation of Stokes shift with the molecular–microscopic empirical solvent polarity parameter ( ETN). The observed excited-state dipole moments are larger than their ground-state counterparts, indicating a substantial redistribution of the electron densities in a more dipolar excited state for both coumarins investigated.

Paramecium caudatum as a source of nitric oxide: Chemiluminescent detection based on Bluestar® Forensic reagent connected with microdialysis


Nitric oxide (NO) chemistry inside the body is the most interesting part of its behavior. NO is involved in controlling blood pressure, and in transmitting nerve signals and a variety of other signaling processes. To explain the behavior of NO, it is necessary to determine its immediate concentration or observe time-dependent changes in its concentration. In Paramecium caudatum, NO is formed by calcium-dependent nNOS (NOS1)-like protein, which is distributed in the cytoplasm. NO synthesis affects the ciliary beat and consequent motility of cells and blocked NO synthesis reduces the ability of cells to move. The possibility of online coupling of microdialysis (of P. caudatum solution) with NO detection is demonstrated. Direct measurement of NO is carried out using dilute Bluestar® Forensic reagent (luminol–H2O2 system; one of the NO detections is based upon the chemiluminescent reaction between NO and the luminol–H2O2 system, which is specifically reactive to NO). The effect of a nitric oxide synthase inhibitor, NG-nitro-l-arginine methyl ester was observed. NO production was inhibited and the movement of P. caudatum was restricted. These effects were time dependent and after a specific time were reversed.

BSA–AuNPs@Tb–AMP metal–organic frameworks for ratiometric fluorescence detection of DPA and Hg2+


An easy and effective strategy for synthesizing a ratiometric fluorescent nanosensor has been demonstrated in this work. Novel fluorescent BSA–AuNPs@Tb–AMP (BSA, bovine serum albumin; AMP, adenosine 5′-monophosphate; AuNPs, Au nanoparticles) metal–organic framework (MOF) nanostructures were synthesized by encapsulating BSA–AuNPs into Tb–AMP MOFs for the detection of 2,6-pyridinedicarboxylic acid (DPA) and Hg2+. DPA could strongly co-ordinate with Tb3+ to replace water molecules from the Tb3+ center and accordingly enhanced the fluorescence of Tb–AMP MOFs. The fluorescence of BSA–AuNPs at 405 nm remained constant. While the fluorescence of BSA–AuNPs at 635 nm was quenched after Hg2+ was added, the fluorescence of Tb–AMP MOFs remained constant. Accordingly, a ratiometric fluorescence nanosensor was constructed for detection of DPA and Hg2+. The ratiometric nanosensor exhibited good selectivity to DPA over other substances. The F545/F405 linearly increased with increase of DPA concentration in the range of 50 nM to 10 μM with a detection limit as low as 17.4 nM. F635/F405 increased linearly with increase of Hg2+ concentration ranging from 50 nM to 1 μM with a detection limit as low as 20.9 nM. Additionally, the nanosensor could be successfully applied for the determination of DPA and Hg2+ in running water.

Spectrofluorimetric determination of atenolol from human urine using high-affinity molecularly imprinted solid-phase extraction sorbent


This study presents a novel, sensitive and selective molecularly imprinted solid-phase extraction (MISPE)–spectrofluorimetric method for the removal and determination of atenolol from human urine. Molecularly imprinted and non-imprinted polymers were synthesized thermally using a radical chain polymerization technique and used as solid-phase extraction sorbents. Acrylic acid ethylene glycol dimethacrylate, dibenzoyl peroxide and dichloroethane were used as a functional monomer, cross-linker, initiator and porogen, respectively. The calibration curve was in the range of 0.10–2.0 μg/ml for the developed method. Limit of detection and limit of quantification values were 0.032 and 0.099 μg/ml, respectively. Owing to the selectivity of the MISPE technique and the sensitivity of spectrofluorimetry, trace levels of atenolol have been successfully determined from both organic and aqueous media. Relatively high imprinting factor (4.18) and recovery results (74.5–75.3%) were obtained. In addition, intra- and interday precision values were 0.38–1.03% and 0.47–2.05%, respectively, proving the precision of the proposed method. Thus, a selective, sensitive and simple MISPE–spectrofluorimetric method has been developed and applied to the direct determination of atenolol from human urine.

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Synthesis and luminescence characterization of Y2BaZnO5:RE (RE = Eu3+, Tb3+, Pr3+ and Sm3+) phosphors


Modified synthesis and luminescence of Y2BaZnO5 phosphors activated with the rare earths (RE) Eu3+, Tb3+, Pr3+ and Sm3+ are reported. RE2BaZnO5 phosphors have attracted attention because of their interesting magnetic and optical properties; and are usually prepared using a two-step solid-state reaction. In the first step, carbonates or similar precursors are thoroughly mixed and heated at 900°C to decompose them to oxides. To eliminate the unwanted phases like BaRE2O4, the resulting powders are reheated at 1100°C for a long time. We prepared Y2BaZnO5 phosphors activated with various activators by replacing the first step with combustion synthesis. The photoluminescence results are presented. The photoluminescence results for Eu3+, Tb3+ and Pr3+ are in good agreement with the literature. However, photoluminescence emission from Sm3+ has not been documented previously. The excitation spectrum of Eu3+ is dominated by a charge transfer band around 261 nm, and an additional band around 238 nm is always present, irrespective of the type of activator. The presence of this band for all these different types of activators was interpreted as host absorption.

Synthesis and luminescence properties of CaSnO3:Bi3+ blue phosphor and the emission improvement by Li+ ion


CaSnO3:Bi3+ blue-emitting phosphor was synthesized using a high-temperature solid-state reaction method in air. The crystal structures and luminescence properties were investigated. A broad emission band peaking at ~448 nm upon excitation at 262 and 308 nm was observed in the range 330–680 nm at room temperature due to 3P1  1S0 transition of the Bi3+ ion. The chromaticity coordinate was (0.1786, 0.1665). The optimal Bi3+ ion concentration was ~0.6 mol% in CaSnO3:Bi3+ phosphor. The emission spectrum of CaSnO3:Bi3+ phosphor showed a blue-shift with increasing temperature from 50 to 300 K due to the influence of temperature on the electron transition of the Bi3+ ion. The emission intensity of CaSnO3:Bi3+ phosphor may be increased ~1.45 times by co-doping Li+ ions as a charge compensator and fluxing agent. The luminescence mechanism is explained by a configurational coordinate diagram of Bi3+ ion in CaSnO3:Bi3+ phosphor.

Sol–gel synthesis and luminescence property of Sr4Al2O7:Re3+,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors for white LEDs


Sr4Al2O7:Eu3+ and Sr4Al2O7:Dy3+ phosphors with alkali metal substitution were prepared using a sol–gel method. The effects of a charge compensator R on the structure and luminescence of Sr4Al2O7:Re3+,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors were investigated in detail. Upon heating to 1400°C, the structure of the prepared samples was that of the standard phase of Sr4Al2O7. Under ultraviolet excitation, all Sr4Al2O7:Eu3+,R+ samples exhibited several narrow emission peaks ranging from 550 to 700 nm due to the 4f  4f transition of Eu3+ ions. All Sr4Al2O7:Dy3+,R+ phosphors showed two emission peaks at 492 and 582 nm, due to the 4F9/2  6H15/2 and 4F9/2  6H13/2 transitions of Dy3+ ions, respectively. The luminescence intensity of Sr4Al2O7:Re3+,R+ (Re = Eu and Dy; R = Li, Na and K) phosphors improved markedly upon the addition of charge compensators, promoting their application in white light-emitting diodes with a near-ultraviolet chip.

Fluorescence-based sensor for selective and sensitive detection of amoxicillin (Amox) in aqueous medium: Application to pharmaceutical and biomedical analysis


We here for the first time demonstrate an analytical approach for the highly selective and sensitive detection of amoxicillin (Amox) in aqueous medium based on the fluorescence quenching of quantum dots (QDs). The change in fluorescence intensity of mercaptopropionic acid-capped cadmium sulphide (MPA-CdS) QDs is attributed to the increasing concentration of Amox. The results show that the fluorescence quenching of QDs by Amox takes place through both static and dynamic types of quenching mechanism. The fluorescence quenching of QDs with increase in concentration of Amox shows the linear range between 5 μg ml−1 and 30 μg ml−1 and the limit of detection (LOD) is 5.19 μg ml−1. There is no interference of excipients, which are commonly present in pharmaceutical formulation and urine samples. For the practical application approach, the developed method has been successfully applied for the determination of Amox in pharmaceutical formulations and urine samples with acceptable results.

Identification and characterization of the Luc2-type luciferase in the Japanese firefly, Luciola parvula, involved in a dim luminescence in immobile stages


Nocturnal Japanese fireflies, Luciola parvula, emit from their lanterns a yellow light, one of the most red-shifted colors found among fireflies. Previously, we isolated and characterized two different types of luciferase gene, Luc1 and Luc2, from the fireflies Luciola cruciata and Luciola lateralis; Luc1 is responsible for the green–yellow luminescence of larval and adult lanterns, whereas Luc2 is responsible for the dim greenish glow of eggs and pupal bodies. The biological role of firefly lanterns in adults is related to sexual communication, but why the eggs and pupae glow remains uncertain. In this study, we isolated the gene Luc2 from L. parvula, and compared its expression profiles and enzymatic characteristics with those of Luc1. A semi-quantitative reverse transcription polymerase chain reaction showed that Luc1 was predominantly expressed in larvae, prepupae, pupae and adults, whereas Luc2 was expressed in eggs, prepupae, pupae and adult females. Enzymatic analyses showed that the luminescent color of Luc1 matches the visual sensitivity of L. parvula eyes, whereas that of Luc2 is very different from it. These results suggest that the biological role of Luc2 expressed in immobile stages is not intraspecific communication.

Molecular recognition and binding of beta-lactamase II from Bacillus cereus with penicillin V and sulbactam by spectroscopic analysis in combination with docking simulation


The molecular recognition and binding interaction of beta-lactamase II from Bacillus cereus (Bc II) with penicillin V (PV) and sulbactam (Sul) at 277 K were studied by spectroscopic analysis and molecular docking. The results showed that a non-fluorescence static complex was separately formed between Bc II and two ligands, the molecular ratio of Bc II to PV or Sul was both 1:1 in the binding and the binding constants were 2.00 × 106 and 3.98 × 105 (L/mol), respectively. The negative free energy changes and apparent activation energies indicated that both the binding processes were spontaneous. Molecular docking showed that in the binding process, the whole Sul molecule entered into the binding pocket of Bc II while only part of the whole PV molecule entered into the pocket due to a long side chain, and electrostatic interactions were the major contribution to the binding processes. In addition, a weak conformational change of Bc II was also observed in the molecular recognition and binding process of Bc II with PV or Sul. This study may provide some valuable information for exploring the recognition and binding of proteins with ligands in the binding process and for the design of novel super-antibiotics.

Probing the mechanism of interaction of metoprolol succinate with human serum albumin by spectroscopic and molecular docking analysis


In the present work, the mechanism of the interaction between a β1 receptor blocker, metoprolol succinate (MS) and human serum albumin (HSA) under physiological conditions was investigated by spectroscopic techniques, namely fluorescence, Fourier transform infra-red spectroscopy (FT-IR), fluorescence lifetime decay and circular dichroism (CD) as well as molecular docking and cyclic voltammetric methods. The fluorescence and lifetime decay results indicated that MS quenched the intrinsic intensity of HSA through a static quenching mechanism. The Stern–Volmer quenching constants and binding constants for the MS–HSA system at 293, 298 and 303 K were obtained from the Stern–Volmer plot. Thermodynamic parameters for the interaction of MS with HSA were evaluated; negative values of entropy change (ΔG°) indicated the spontaneity of the MS and HSA interaction. Thermodynamic parameters such as negative ΔH° and positive ΔS° values revealed that hydrogen bonding and hydrophobic forces played a major role in MS–HSA interaction and stabilized the complex. The binding site for MS in HSA was identified by competitive site probe experiments and molecular docking studies. These results indicated that MS was bound to HSA at Sudlow's site I. The efficiency of energy transfer and the distance between the donor (HSA) and acceptor (MS) was calculated based on the theory of Fosters' resonance energy transfer (FRET). Three-dimensional fluorescence spectra and CD results revealed that the binding of MS to HSA resulted in an obvious change in the conformation of HSA. Cyclic voltammograms of the MS–HSA system also confirmed the interaction between MS and HSA. Furthermore, the effects of metal ions on the binding of MS to HSA were also studied.

Synthesis and luminescence properties of blue-emitting phosphor Ca12Al14O32F2:Eu2+ for white light-emitting diode


A blue-emitting phosphor Ca12Al14O32F2:Eu2+ was synthesized using a high-temperature solid-state reaction under a reductive atmosphere. The X-ray diffraction measurements indicate that a pure phase Ca12Al14O32F2:Eu2+ can be obtained for low doping concentration of Eu2+. The phosphor has a strong absorption in the range 270–420 nm with a maximum at ~340 nm and blue emission in the range 400–500 nm with chromatic coordination of (0.152, 0.045). The optimal doping concentration is ~0.24. In addition, the luminescence properties of the as-synthesized phosphor were evaluated by comparison with those of Ca12Al14O32Cl2:Eu2+ and the commercially available phosphor BaMgAl10O17:Eu2+. The emission intensity of Ca12Al14O32F2:Eu2+ was ~72% that of BaMgAl10O17:Eu2+ under excitation at λ = 375 nm. The results indicate that Ca12Al14O32F2:Eu2+ has potential application as a near-UV-convertible blue phosphor for white light-emitting diodes.

Insights into the discrepant luminescence for BaSiO3:Eu2+ phosphors prepared by solid-state reaction and precipitation reaction methods


Two synthesis routes, solid-state reaction and precipitation reaction, were employed to prepare BaSiO3:Eu2+ phosphors in this study. Discrepancies in the luminescence green emission at 505 nm for the solid-state reaction method sample and in the yellow emission at 570 nm for the sample prepared by the precipitation reaction method, were observed respectively. A detail investigation about the discrepant luminescence of BaSiO3:Eu2+ phosphors was performed by evaluation of X-ray diffraction (XRD), photoluminescence (PL)/photoluminescence excitation (PLE), decay time and thermal quenching properties. The results showed that the yellow emission was generated from the BaSiO3:Eu2+ phosphor, while the green emission was ascribed to a small amount of Ba2SiO4:Eu2+ compound that was present in the solid-state reaction sample. This work clarifies the luminescence properties of Eu2+ ions in BaSiO3 and Ba2SiO4 hosts.

Graphite oxide-dispersed CdTe quantum dots nanocomposite for flexible display luminescent membranes


A quantum dot (QD) dispersant material was prepared using graphite oxide (GO). Luminescent films were prepared using polyvinyl alcohol as the polymer matrix. First, water-soluble CdTe QDs were prepared by wet chemistry and GO was synthesized using a modified Hummers method. X-Ray diffraction tests showed that the GO reflection peak [001] was 11.9°, which indicates that the d-spacing is 0.7431 nm; atomic force microscopy showed a GO thickness of 200 nm. Fourier transform infrared spectra showed vibrations at 1624 cm−1 for the carbonyl groups, and 3260 cm−1 for the GO samples; the -C–O vibration was at 1320 cm−1 and -COOH, −OH vibrations were at 950 cm−1. Fluorescent tests showed that pH had an impact on the QD colloidal stability. GO was neutralized before use as the host media for the GO/QDs nanocomposite. The results proved that the resultant nanocomposite is promising for use in brightness enhancement films in flexible displays.

Polymer composite fluorescent hydrogel film based on nitrogen-doped carbon dots and their application in the detection of Hg2+ ions


A simple microwave-assisted solvothermal method was used to prepare fluorescent nitrogen-doped carbon dots (N-CDs) with high fluorescence quantum yield (79.63%) using citric acid and N-(2-hydroxyethyl)ethylenediamine as starting materials. The PVAm-g-N-CDs grafted products were synthesized by amide bond formation between the carboxylic groups of N-CDs and amine groups of polyvinylamine (PVAm). Fluorescent hydrogel films (PVAm-g-N-CDs/PAM) were synthesized by interpenetration polymer network polymerization of PVAm-g-N-CDs and acrylamide (AM). When used for ion detection, we found that the fluorescence of the hydrogel films was clearly quenched by addition of Hg2+. Repeatability tests on using the hydrogel films for Hg2+ detection showed that they could be applied at least three times. The PVAm-g-N-CDs/PAM could serve as an effective fluorescent sensing platform for sensitive detection of Hg2+ ions with a detection limit of 0.089 μmol/L. This work may offer a new approach for developing recoverable and sensitive N-CDs-based sensors for biological and environmental applications.

Binding of hydroxylated polybrominated diphenyl ethers with human serum albumin: Spectroscopic characterization and molecular modeling


Three hydroxylated polybrominated diphenyl ethers (OH-PBDEs), 3-OH-BDE-47, 5-OH-BDE-47, and 6-OH-BDE-47, were selected to investigate the interactions between OH-PBDEs with human serum albumin (HSA) under physiological conditions. The observed fluorescence quenching can be attributed to the formation of complexes between HSA and OH-PBDEs. The thermodynamic parameters at different temperatures indicate that the binding was caused by hydrophobic forces and hydrogen bonds. Molecular modeling and three-dimensional fluorescence spectrum showed conformational and microenvironmental changes in HSA. Circular dichroism analysis showed that the addition of OH-PBDEs changed the conformation of HSA with a minor reduction in α-helix content and increase in β-sheet content. Furthermore, binding distance r between the donor (HSA) and acceptor (three OH-PBDEs) calculated using Förster's nonradiative energy transfer theory was <7 nm; therefore, the quenching mechanisms for the binding between HSA and OH-PBDEs involve static quenching and energy transfer. Combined with molecular dynamics simulations, the binding free energies (ΔGbind) were calculated using molecular mechanics/Poisson − Boltzmann surface area method, and the crucial residues in HSA were identified.

Deciphering the intercalative binding modes of benzoyl peroxide with calf thymus DNA


The binding of benzoyl peroxide (BPO), a flour brightener, with calf thymus DNA (ctDNA) was predicted by molecular simulation, and this were confirmed using multi-spectroscopic techniques and a chemometrics algorithm. The molecular docking result showed that BPO could insert into the base pairs of ctDNA, and the adenine bases were the preferential binding sites which were validated by the analysis of Fourier transform infrared spectra. The mode of binding of BPO with ctDNA was an intercalation as supported by the results from ctDNA melting and viscosity measurements, iodide quenching effects and competitive binding investigations. The circular dichroism and DNA cleavage assays indicated that BPO induced a conformational change from B-like DNA structure towards to A-like form, but did not lead to significant damage in the DNA. The complexation was driven mainly by hydrogen bonds and hydrophobic interactions. Moreover, the ultraviolet–visible (UV–vis) spectroscopic data matrix was resolved by a multivariate curve resolution–alternating least–squares algorithm. The equilibrium concentration profiles for the components (BPO, ctDNA and BPO–ctDNA complex) were extracted from the highly overlapping composite response to quantitatively monitor the BPO–ctDNA interaction. This study has provided insights into the mechanism of the interaction of BPO with ctDNA and potential hazards of the food additive.

Enhanced photoluminescence of the Ca0.8Zn0.2TiO3:0.05% Pr3+ phosphor by optimized hydrothermal conditions


The red-emitting phosphor Ca0.8Zn0.2TiO3:Pr3+ was synthesized using an ethylene glycol (EG)-assisted hydrothermal method. The effects of additional amounts of and order of adding EG, plus hydrothermal temperature, time, and pH on the composition, morphology and optical properties of the titanate phosphors were studied. The crystalline phases of the titanate phosphors were confirmed to be constituted of a series of co-existing CaTiO3, Zn2TiO4 and Ca2Zn4Ti16O38 compounds in various proportions that were visualized using an X-ray diffractometer (XRD). The optical properties of the phosphors were studied using photoluminescence spectra and UV–visible spectroscopy. The results show that the impurities Zn2TiO4:Pr3+ and Ca2Zn4Ti16O38:Pr3+ significantly contributed to the enhancement of an absorption band around 380 nm. The optimum Ca0.8Zn0.2TiO3:Pr3+ phosphor consisting of appropriate amounts of CaTiO3, Ca2Zn4Ti16O38 and Zn2TiO4 in three phases was achieved by controlling the hydrothermal conditions, and the obtained red phosphor exhibited the highest red emission (1D2  3H4 transition of Pr3+) with an ideal chromaticity coordinate located at (x = 0.667, y = 0.332) under 380 nm excitation.

Characterization of a novel allergenic protein from the octocoral Scleronephthya gracillima (Kuekenthal) that corresponds to a new GFP-like family named Akane


Certain marine organisms have been known to cause allergic reactions among occupational fishermen. We have previously reported that bronchial asthma among the workers engaged in spiny lobster fishing in Japan was caused by octocorals such as Dendronephthya sp. and Scleronephthya gracillima (previously named Alcyonium gracillimum). Now we have found another octocoral, Scleronephthya gracillima (Kuekenthal), which causes the allergic disease in fishermen. The octocoral was characterized as a new green fluorescent protein (GFP)-like family. The new allergen has a molecular mass of 27 kDa in 1D and 2D SDS-PAGE under reduced conditions. The 27 kDa component was determined to be an allergen by western blotting, ECL immune staining method and absorption of patient sera with the antigen. Furthermore, the combination of analysis with LC-ESI-MS/MS and MASCOT search in the NCBInr database concluded the 27 kDa component had the sequence YPADI/LPDYFK, and that the 22 kDa component had the sequence QSFPEGFSWER, which both matched a GFP-like protein in Acropora aculeus and in Montastraea annularis. Further analysis by MALDI-TOF/MS/MS and MASCOT search in the NCBInr database of all 27 kDa eight spot components from 2D SDS-PAGE indicated that the sequence QSFPEGFSWER also matched as GFP-like protein in Lobophyllia hemprichii and Scleractinia sp. To our knowledge, this is the first report of the new allergenic protein that corresponds to a new GFP-like protein named Akane, and which has fluorescent emissions in the red and green part of the spectra at 628 nm and 508 nm, respectively.

Comparison and analysis on the serum-binding characteristics of aspirin–zinc complex and aspirin


This study was designed to compare the protein-binding characteristics of aspirin–zinc complex (AZN) with those of aspirin itself. AZN was synthesized and interacted with a model transport protein, human serum albumin (HSA). Three-dimensional fluorescence, ultraviolet–visible and circular dichroism (CD) spectra were used to characterize the interaction of AZN with HSA under physiological conditions. The interaction mechanism was explored using a fluorescence quenching method and thermodynamic calculation. The binding site and binding locality of AZN on HSA were demonstrated using a fluorescence probe technique and Förster non-radiation energy transfer theory. Synchronous fluorescence and CD spectra were employed to reveal the effect of AZN on the native conformation of the protein. The HSA-binding results for AZN were compared with those for aspirin under consistent experimental conditions, and indicated that aspirin acts as a guide in AZN when binding to Sudlow's site I, in subdomain IIA of the HSA molecule. Moreover, compared with aspirin, AZN showed greater observed binding constants with, but smaller changes in the α-helicity of, HSA, which proved that AZN might be easier to transport and have less toxicity in vivo.

Tunable luminescence and energy transfer in Ca3SiO4Cl2:Ce3+,Li+,Mn2+,Eu2+ phosphors


A series of color-tunable Ca3–2x-y-zSiO4Cl2 (CSC):xCe3+,xLi+,yMn2+,zEu2+ phosphors with low temperature phase structure was synthesized via the sol–gel method. An energy transfer process from Ce3+ to Mn2+ in CSC:0.01Ce3+,0.01Li+,yMn2+ (y = 0.03–0.09) and the mechanism was verified to be an electric dipole–dipole interaction. The Ce3+ and Mn2+ emission intensities were greatly enhanced by co-doping Eu2+ ions into CSC:0.01Ce3+,0.01Li+,0.07Mn2+ phosphors due to competitive energy transfers from Eu2+/Ce3+ to Mn2+, and Ce3+ to Eu2+. Under 332 nm excitation, CSC:0.01Ce3+,0.01Li+,0.07Mn2+,zEu2+ (z = 0.0005–0.002) exhibited tunable emission colors from green to white with coexisting orange, green and violet-blue emissions. These phosphors could have potential application in white light-emitting diodes.

One-step synthesis of nitrogen, boron co-doped fluorescent carbon nanoparticles for glucose detection


Heteroatom-doped carbon nanoparticles (CNPs) have attracted considerable attention due to an effective improvement in their intrinsic properties. Here, a facile and simple synthesis of nitrogen, boron co-doped carbon nanoparticles (NB-CNPs) from a sole precursor, 3-aminophenylboronic acid, was performed via a one-step solid-phase approach. Because of the presence of boronic acid, NB-CNPs can be used directly as a fluorescent probe for glucose. Based on a boronic acid-triggered specific reaction, we developed a simple NB-CNP probe without surface modification for the detection of glucose. When glucose was introduced, the fluorescence of NB-CNPs was suppressed through a surface-quenching states mechanism. Obvious fluorescence quenching allowed the highly sensitive determination of glucose with a limit of detection of 1.8 μM. Moreover, the proposed method has been successfully used to detect glucose in urine from people with diabetes, suggesting potential application in sensing glucose.

A highly sensitive detection of chloramphenicol based on chemiluminescence immunoassays with the cheap functionalized Fe3O4@SiO2 magnetic nanoparticles


A strategy has been applied to chloramphenicol (CAP) detection with chemiluminescence immunoassays (CLIA) based on cheap functionalized Fe3O4@SiO2 magnetic nanoparticles (Fe–MNPs). The strategy that bovine serum albumin (BSA) was immobilized on cheap functionalized Fe–MNPs and that the CAP molecules were then immobilized on BSA, avoided the long process of dialysis for preparation of the BSA-CAP conjugates. The samples were detected for both methods that utilized two different kinds of functionalized Fe–MNPs (amine-functionalized Fe3O4@SiO2 and carboxylic acid-functionalized Fe3O4@SiO2). The sensitivities and limits of detection (LODs) of the two methods were obtained and compared based on inhibition curves. The 50% inhibition concentrations (IC50) values of the two methods were about 0.024 ng ml−1 and 0.046 ng ml−1 respectively and LODs were approximately 0.0002 ng ml−1 and 0.001 ng ml−1 respectively. These methods were much more sensitive than that of any traditional enzyme-linked immunosorbent assay (ELISA) previously reported. Therefore, such chemiluminescence methods could be easily adapted for small molecule detection in a variety of foods using Fe–MNPs.

Copper nanocluster-enhanced luminol chemiluminescence for high-selectivity sensing of tryptophan and phenylalanine


A remarkable method for the highly sensitive detection of phenylalanine and tryptophan based on a chemiluminescence (CL) assay was reported. It was found that fluorescent copper nanoclusters capped with cysteine (Cys-CuNCs) strongly enhance the weak CL signal resulting from the reaction between luminol and H2O2. Of the amino acids tested, phenylalanine and tryptophan could enhance the above CL system sensitively. Under optimum conditions, this method was satisfactorily described by a linear calibration curve over a range of 1.0 × 10−6 to 2.7 × 10−5 M for phenylalanine and 1.0 × 10−7 to 3.0 × 10−5 M for tryptophan, respectively. The effect of various parameters such as Cys-CuNC concentration, H2O2 concentration and pH on the intensity of the CL system were also studied. The main experimental advantage of the proposed method was its selectivity for two amino acids compared with others. To evaluate the applicability of the method to the analysis of a real biological sample it was used to determine tryptophan and phenylalanine in human serum and remarkable results were obtained.

A highly selective colorimetric and fluorescent dual-modal probe for the rapid determination of fluoride anions


In this work, 4-(p-hydroxybenzylidenehydrazino)-N-butyl-1,8-naphthalimide (1) has been designed and synthesized as a colorimetric and fluorescent dual-modal probe for F−. Compound 1 immediately detected inorganic fluoride salts using UV/vis absorption and fluorescence spectroscopy methods, and served as a ‘naked-eye’ indicator for F− with high selectivity and sensitivity. Both the absorption and fluorescence spectra show excellent linearity with the concentration of F−. Real-life applications demonstrated that our proposed analytical system provided a satisfactory method for the determination of F−. In addition, the reaction mechanism of deprotonation was confirmed by 1H NMR.

Binding of fluphenazine with human serum albumin in the presence of rutin and quercetin: An evaluation of food-drug interaction by spectroscopic techniques


The interactions between human serum albumin (HSA) and fluphenazine (FPZ) in the presence or absence of rutin or quercetin were studied by fluorescence, absorption and circular dichroism (CD) spectroscopy and molecular modeling. The results showed that the fluorescence quenching mechanism was static quenching by the formation of an HSA–FPZ complex. Entropy change (ΔS0) and enthalpy change (ΔH0) values were 68.42 J/(mol⋅K) and −4.637 kJ/mol, respectively, which indicated that hydrophobic interactions and hydrogen bonds played major roles in the acting forces. The interaction process was spontaneous because the Gibbs free energy change (ΔG0) values were negative. The results of competitive experiments demonstrated that FPZ was mainly located within HSA site I (sub-domain IIA). Molecular docking results were in agreement with the experimental conclusions of the thermodynamic parameters and competition experiments. Competitive binding to HSA between flavonoids and FPZ decreased the association constants and increased the binding distances of FPZ binding to HSA. The results of absorption, synchronous fluorescence, three-dimensional fluorescence, and CD spectra showed that the binding of FPZ to HSA caused conformational changes in HSA and simultaneous effects of FPZ and flavonoids induced further HSA conformational changes.

Utility of Hantzsch reaction for development of highly sensitive spectrofluorimetric method for determination of alfuzosin and terazosin in bulk, dosage forms and human plasma


A highly sensitive, cheap, simple and accurate spectrofluorimetric method has been developed and validated for the determination of alfuzosin hydrochloride and terazosin hydrochloride in their pharmaceutical dosage forms and in human plasma. The developed method is based on the reaction of the primary amine moiety in the studied drugs with acetylacetone and formaldehyde according to the Hantzsch reaction, producing yellow fluorescent products that can be measured spectrofluorimetrically at 480 nm after excitation at 415 nm. Different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The fluorescence–concentration plots of alfuzosin and terazosin were rectilinear over a concentration range of 70–900 ng ml−1, with quantitation limits 27.1 and 32.2 ng ml−1 for alfuzosin and terazosin, respectively. The proposed method was validated according to ICH guidelines and successfully applied to the analysis of the investigated drugs in dosage forms, content uniformity test and spiked human plasma with high accuracy.

A comparison between the larval eyes of the dimly luminescent Keroplatus nipponicus and the brightly luminescent Arachnocampa luminosa (Diptera; Keroplatidae)


Larvae of the weakly blue-luminescent fungus gnat Keroplatus nipponicus possess on either side of their heads a small black stemmatal eye with a plano-convex lens approximately 25 μm in diameter. In total, 12–14 retinula cells give rise to a centrally fused rhabdom of up to 8 μm in diameter. The rhabdom's constituent microvilli, approximately 70 nm in width, are roughly orthogonally oriented, a requirement for polarization sensitivity. Screening pigment granules are abundant in the retinula cells and measure at least 1 μm in diameter. In comparison with the stemmatal eye of the brightly luminescent Arachnocampa luminosa, that of K. nipponicus is considerably smaller with a poorer developed lens and a rhabdom that is less voluminous, but possesses wider microvilli. Although the larval eye of K. nipponicus can be expected to be functional, as the larvae react to light with a behavioural response, the eyes are probably mainly involved in the detection of ambient light levels and not, as in A. luminosa, also in responding to the luminescence of nearby conspecifics.

Determination of fluvoxamine maleate in human urine and human serum using alkaline KMnO4–rhodamine B chemiluminescence


The flow-injection chemiluminescence (FI-CL) behavior of a gold nanocluster (Au NC)–enhanced rhodamine B–KMnO4 system was studied under alkaline conditions for the first time. In the present study, the as-prepared bovine serum albumin-stabilized Au NCs showed excellent stability and reproducibility. The addition of trace levels of fluvoxamine maleate (Flu) led to an obvious decline in CL intensity in the rhodamine B–KMnO4–Au NCs system, which could be used for quantitative detection of Flu. Under optimized conditions, the proposed CL system exhibited a favorable analytical performance for Flu determination in the range 2 to 100 μg ml−1. The detection limit for Flu measurement was 0.021 μg ml−1. Moreover, this newly developed system revealed outstanding selectivity for Flu detection when compared with a multitude of other species, such as the usual ions, uric acid and a section of hydroxy compounds. Additionally, CL spectra, UV–visible spectroscopes and fluorescence spectra were measured in order to determine the possible reaction mechanism. This approach could be used to detect Flu in human urine and human serum samples with the desired recoveries and could have promising application under physiological conditions.

Tunable emission from LiBaBO3:Eu3+;Bi3+ phosphor for solid-state lighting


Europium (Eu3+) and bismuth (Bi3+) co-activated LiBaBO3 powder phosphors were synthesized by a solid-state reaction and the structure, particle morphology, optical and photoluminescent properties were investigated. X-Ray diffraction patterns of the LiBaBO3 phosphors crystallized in a pure monoclinic phase, i.e. there were no secondary phases due to either incidental impurities or undecomposed starting materials. Scanning electron microscopy images showed that the powders were made up of fluffy needle-like particles that were randomly aligned. The band-gap of the LiBaBO3 host was estimated to be 3.33 eV from the UV/vis absorption data. Blue emission was observed from the LiBaBO3 host, which is ascribed to self-activation of the host matrix. In addition, greenish-blue (493 nm) and red (613 nm) emissions were observed from europium-doped samples and were attributed to the emissions of Eu2+ and Eu3+, respectively. Furthermore, after codoping with Bi3+, the emission intensity of Eu3+ located at 613 nm was significantly enhanced. From the Commission Internationale de I′Eclairage (CIE) color coordinates, white emission was observed from LiBa1–xBO3:xEu3+ (x = 0.020 and 0.025) phosphor powders with color coordinates of x = 0.368, y = 0.378 and x = 0.376, y = 0.366, respectively.

Glutathione-stabilized Cu nanocluster-based fluorescent probe for sensitive and selective detection of Hg2+ in water


In this paper, an innovative and facile one-pot method for synthesizing water-soluble and stable fluorescent Cu nanoclusters (CuNCs), in which glutathione (GSH) served as protecting ligand and ascorbic acid (AA) as reducing agent was reported. The resultant CuNCs emitted blue-green fluorescence at 440 nm, with a quantum yield (QD) of about 3.08%. In addition, the prepared CuNCs exhibited excellent properties such as good water solubility, photostability and high stability toward high ionic strength. On the basis of the selective quenching of Hg2+ on CuNCs fluorescence, which may be the result of Hg2+ ion-induced aggregation of the CuNCs, the CuNCs was used for the selective and sensitive determination of Hg2+ in aqueous solution. The proposed analytical strategy permitted detection of Hg2+ in a linear range of 4 × 10−8 to 6 × 10−5 M, with a detection limit of 2.2 × 10−8 M. Eventually, the practicability of this sensing approach was confirmed by its successful application to assay Hg2+ in tap water, Lotus lake water and river water samples with the quantitative spike recoveries ranging from 96.9% to 105.4%.

Theoretical insights into the effect of pH values on oxidation processes in the emission of firefly luciferin in aqueous solution


To elucidate the emission process of firefly d-luciferin oxidation across the pH range of 7–9, we identified the emission process by comparison of the potential and free-energy profiles for the formation of the firefly substrate and emitter, including intermediate molecules such as d-luciferyl adenylate, 4-membered dioxetanone, and their deprotonated chemical species. From these relative free energies, it is observed that the oxidation pathway changes from d-luciferin deprotonated d-luciferyl adenylate deprotonated 4-membered dioxetanone oxyluciferin to deprotonated d-luciferin deprotonated d-luciferyl adenylate deprotonated 4-membered dioxetanone oxyluciferin with increasing pH value. This indicates that deprotonation on 6′OH occurs during the formation of dioxetanone at pH 7–8, whereas luciferin in the reactant has a 6′OH-deprotonated form at pH 9.

A highly sensitive sensor for ethyl acetate by changing fluorescent colour of lanthanide complex


A lanthanide complex, namely, [La2(L-DBTA)3 (CH3OH)2(H2O)2]∙2H2O has been synthesized using a simple reaction of L-O,O´-dibenzoyl tartaric acid with LaCl3∙6H2O under ambient temperature. The luminescence spectrum in the solid state at room temperature revealed that the complex exhibited blue-light emission that originated from ligand. In addition, the lanthanide complex is developed as a fluorescent probe for sensing small molecules. Luminescence studies reveal that the lanthanide complex could detect ethyl acetate sensitively through fluorescence colour change from blue to yellow. Furthermore, the complex exhibited appealing features including high sensitivity and an ultrafast response.