A bifunctional probe for Al3+ and Zn2+ based on diarylethene with an ethylimidazo[2,1-b]thiazole-6-hydrazide unit

A new diarylethene with ethylimidazo[2,1-b]thiazole-6-hydrazide unit was synthesized, and its photochromic and fluorescent behaviors have been systematically investigated by the stimulation of lights and metal ions in methanol. This new diarylethene exhibited high selectivity and sensitivity toward Al³⁺ and Zn²⁺. The addition of Al³⁺ and Zn²⁺ displayed excellent colorimetric response behaviour with the concomitant color change from colorless to yellow, which could be easily observed by the naked eye. Upon addition of Al³⁺, the fluorescence intensity was enhanced by 180–fold and the emission peak of 1O–Al³⁺ blue-shifted by 15?nm accompanied with a color change from colorless to bright blue. In contrast, when stimulated with Zn²⁺, its fluorescence intensity was enhanced by 35–fold and the emission peak of 1O–Zn²⁺ red-shifted by 16?nm with an evident color change from black to bright green. The LOD for Al³⁺ and Zn²⁺ were determined to be 2.97?×?10^?9?mol?L^?1 and 5.98?×?10^?9?mol?L^?1, respectively. Moreover, a logic circuit was constructed with the fluorescence intensity as the output signal responding to the light and chemical species as the inputs.     

Fluorescence Probe Enhanced Spectrofluorimetric Method for the Determination of Prulifloxacin in Pharmaceutical Formulations and Biological Fluids

Abstract

Spectrofluorimetry for the determination of prulifloxacin (PUFX) was developed based on the strong fluorescence of PUFX after adding fluorescence probe yttrium in buffer solution (pH = 6.80), and various factors of influencing fluorescence have been researched. Under the optimum conditions, the liner range was 2.0 × 10^?8 to 9.1 × 10^?6 mol L^?1 and the detection limit was 8.5 × 10^?9 mol L^?1. The relative standard deviation was 2.1% for 11 measurements of 5.0 × 10^?7 mol L^?1 PUFX standard solution. The mechanism of the sensitizing effect of probe was discussed. The method was applied for the determination of PUFX in actual sample; the result obtained was satisfactory.     

2-(2′-Hydroxyphenyl)-4(3H)-quinazolinone derivatives based fluorescent probes for mercury(II) via an intramolecular proton transfer mechanism

2-(2′,5′-Dihydroxy-phenyl)-4(3H)-quinazolinone (DHPQ), a new fluorescent dye that exhibits excited state intramolecular proton transfer (ESIPT) reaction and possesses good photophysical properties, is synthesised and used as fluorescent probe for detection of Hg²⁺. Mercuric ions can be detected and quantitated by measuring the fluorescent intensity decrease of the probe. The decrease of fluorescence intensity of DHPQ upon the addition of Hg²⁺ was attributed to the blocking of ESIPT reactions of DHPQ and quenching its fluorescence. The analytical performance characteristics of the proposed Hg²⁺ probe were investigated. The probe can be applied to the quantification of Hg²⁺ with a concentration range covering from 8.0?×?10^?7 to 2.0?×?10^?4?mol?L^?1, with a working pH range of 5.5–6.5. It shows excellent selectivity for Hg²⁺ over other transition metal cations. The proposed method was testified for the Hg²⁺ assay in river water samples with satisfying recoveries.     

Anodic Stripping Voltammetric Determination of Aurothiomalate in Urine Using a Screen‐Printed Carbon Electrode

This work describes an electroanalytical method for determining gold(I) thiomalate, aurothiomalate, widely used for treatment of reumatoid arthiritis, using a screen‐printed carbon electrode (SPCE). Aurothiomalate (AuTM) was determined indirectly at the same electrode by accumulating it first at ?1.5 V vs. printed carbon. At this potential in the adsorbed state, the AuTM is reduced to Au(0), which is then oxidized at two steps at ?0.22 V and +0.54 V on SPCE. Using optimized conditions of 60 s deposition time, ?1.5 V (vs. printed carbon) accumulation potential, 100 mV s^?1 scan rate, linear calibration graphs can be obtained by monitoring the peak at +0.54 V for AuTM in HCl 0.1 mol L^?1 from 1.43×10^?6 to 1.55×10^?4 mol L^?1. A limit of detection obtained was 6.50×10^?7 mol L^?1, and the relative standard deviation from five measurements of 3.0×10^?5 mol L^?1 AuTM is 4.5%. The method was successfully applied for AuTM determination in human urine sample.     

A novel Hg2+ fluorescence sensor TPE-TSC based on aggregation-induced emission

Abstract

A fluorescent sensor TPE-TSC with aggregation induced emission (AIE) characteristic is synthesized for detecting Hg²⁺ by attaching thiosemicarbazide (TSC) unit into tetraphenylethylene (TPE) group. TPE-TSC exhibits intense green emission in DMSO/H₂O (V:V?=?1:9) solution with the formation of the aggregation. TPE-TSC shows outstanding fluorescence quenching toward Hg²⁺ over other metal ions due to the formation of complex TPE-TSC/Hg²⁺ with a 2:1 binding ratio. The detection limit of TPE-TSC for Hg²⁺ is 1?×?10^?5 mol·L^?1.     

Determination of Er3+ using a highly selective and easy-to-synthesize fluorescent probe based on Rhodamine 6G

A inducible fluorescent ligand 2-(2-(2-amino-ethylamino) ethyl)-3′,6′- bis (ethylamino)-2′, 7′-dimethy-lspiro[isoindoline-1,9′-xanthen]-3-one was synthesized and used as a fluorescent probe to detect Er³⁺. Er³⁺ could induce the structural transformation of the fluorescent ligand, resulting in a sharp fluorescence emission in a buffered solution. The fluorescence intensity of the fluorescent ligand was enhanced quantitatively with an increase in the concentration of erbium ion. The detection limit of Er³⁺ was 3.0 × 10^?10 mol L^?1 (50 ng L^?1) under optimized conditions. The method applied for the determination of Er³⁺ in four alloy samples had achieved satisfactory results.     

A rhodamine hydrazide–4-nitroindole-3-carboxaldehyde based turn on Hg2+ chemosensor: cytoplasmic live cell imaging,logic gate and memory device applications and computational studies

A new, highly sensitive probe L² for the selective detection of Hg²⁺ in organo-aqueous (H₂O:CH₃CN, 1:1, v/v, HEPES buffer, pH 7.2) medium has been synthesized from rhodamine 6G-hydrazide and 4-nitroindole-3-carboxaldehyde. It was thoroughly characterized by physicochemical techniques including single crystal X-ray diffraction studies. The reaction of L² with Hg²⁺ gives a 1:1 stoichiometry resulting in a 146 fold fluorescence enhancement and a binding constant (K_f) of 3?×?10⁴ M^?1. The spirolactam form of the probe is non-fluorescent; however, it shows dual channel (absorbance and fluorescence) recognition of Hg²⁺ via CHEF effect through the opening of the spirolactam ring. The quantum yields of L² (0.00045) and L²-Hg²⁺ (0.29) show the higher stability of complex in the excited state over the free ligand. The 44.5?nM LOD value demonstrates the detection of Hg²⁺ at a very low concentration range. Cell imaging studies show the cytoplasmic recognition of Hg²⁺ by L². Experimental results are comparable with theoretical values obtained by DFT studies. The fluorescence emission of the complex was completely quenched by I^- and from the reversibility studies an advance level INHIBIT logic gate and memory device can be framed.     

Determination of Folic Acid by Adsorptive Stripping Voltammetry at a Lead Film Electrode

An adsorptive stripping voltammetric procedure for the determination of folic acid at an in situ plated lead film electrode was described. Formation of lead film on a glassy carbon substrate and accumulation of folic acid was performed simultaneously from an acetate buffer solution of pH 5.6 at the potential ?0.88 V. The measurements were carried out from aerated solutions. The calibration graph for an accumulation time of 300 s was linear from 2×10^?9 to 5×10^?8 mol L^?1. The detection limit was 7×10^?10 mol L^?1, the relative standard deviation for 2×10^?8 mol L^?1 of folic acid was 3.9%. The proposed procedure was applied to folic acid determinations in pharmaceutical preparations.     

Direct Electroanalytical Determination of Fluvastatin in a Pharmaceutical Dosage Form: Batch and Flow Analysis

Abstract

The reduction of luvastatin (FLV) at a hanging mercury-drop electrode (HMDE) was studied by square-wave adsorptive-stripping voltammetry (SWAdSV). FLV can be accumulated and reduced at the electrode, with a maximum peak current intensity at a potential of approximately ?1.26 V vs. AgCl/Ag, in an aqueous electrolyte solution of pH 5.25. The method shows linearity between peak current intensity and FLV concentration between 1.0 × 10^?8 and 2.7 × 10^?6 mol L^?1. Limits of detection (LOD) and quantification (LOQ) were found to be 9.9 × 10^?9 mol L^?1 and 3.3 × 10^?8 mol L^?1, respectively.

Furthermore, FLV oxidation at a glassy carbon electrode surface was used for its hydrodynamic monitoring by amperometric detection in a flow-injection system. The amperometric signal was linear with FLV concentration over the range 1.0 × 10^?6 to 1.0 × 10^?5 mol L^?1, with an LOD of 2.4 × 10^?7 mol L^?1 and an LOQ of 8.0 × 10^?7 mol L^?1. A sample rate of 50 injections per hour was achieved.

Both methods were validated and showed to be precise and accurate, being satisfactorily applied to the determination of FLV in a commercial pharmaceutical.     

Adsorptive stripping voltammetry of nickel at a bare glassy carbon electrode

A bare glassy carbon electrode is applied to nickel determination by adsorptive stripping voltammetry in the presence of dimethylglyoxime as a complexing agent. A procedure of nickel determination and electrode regeneration was proposed. The calibration graph for Ni(II) for an accumulation time of 120?s was linear from 2?×?10^?9 to 1?×?10^?7?mol?L^?1. The detection limit was 8.2?×?10^?10?mol?L^?1. The relative standard deviation for a solution containing 2?×?10^?8?mol?L^?1 of Ni(II) was 4.1%. The proposed procedure was applied for Ni(II) determination in certified water reference materials.     

Sensitive Determination of Prulifloxacin by Its Fluorescence Enhancement on Terbium(III)–Sodium Dodecylbenzene Sulfonate System

Abstract

A terbium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of prulifloxacin (PUFX). It was found that SDBS significantly enhanced the fluorescence intensity of the PUFX–Tb³⁺ complex (about 13-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 290 nm and 545 nm, pH 8.0, 4.0 × 10^?5 mol L^?1 terbium(III), and 4.0 × 10^?4 mol L^?1 SDBS. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of PUFX over the range 6.0 × 10^?8 to 2.0 × 10^?6mol L^?1 with a correlation coefficient of 0.9991. The detection limit (S/N = 3) was determined as 8.5 × 10^?9 mol L^?1. This method has been successfully applied for the determination of PUFX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range, and good stability. The luminescence mechanism of the system was also discussed in detail. In the fluorescence system of PUFX–Tb³⁺–SDBS, SDBS acted not only as the surfactant but also as the energy donor.     

A multifunctional aggregation-induced emission (AIE)-active fluorescent chemosensor for detection of Zn2+ and Hg2+

An aggregation-induced emission (AIE)-active fluorescent chemosensor based on a tetraphenylethene (TPE) unit has been successfully designed and synthesized. Interestingly, the luminogen could detect Zn²⁺ selectively in a THF solution with the detection limit of 1.24 × 10⁻⁶ mol L⁻¹. Meanwhile, the luminogen could also detect Hg²⁺ selectively in a THF-water mixture with the water content of 90%, and the detection limit was 2.55 × 10⁻⁹ mol L⁻¹. Furthermore, the solid-state mechanochromic fluorescence behavior of the luminogen was investigated systematically. Indeed, the AIE-active luminogen also exhibited reversible mechanofluorochromic phenomenon involving fluorescent color change from blue to green, and powder X-ray diffraction results indicated that the switchable morphology conversion between crystalline and amorphous states was responsible for this mechanochromism phenomenon.     

Selective detection of Zn2+ and Cd2+ ions in water using a host-guest complex between chromone and Q[7]

In this paper, the host-guest interaction of cucurbit[7]uril (Q[7]) and chromone (CMO) has been developed as a fluorescent probe for the highly selective detection of Zn²⁺ and Cd²⁺ in water based on a chelation-enhanced fluorescence (CHEF) mechanism. There was a good linear relationship between the fluorescence intensity of the CMO@Q[7] probe and the concentration of Zn²⁺ or Cd²⁺ in the range of 0–3.0 × 10^–5 mol/L and the detection limit for Zn²⁺ and Cd²⁺ was found to be 2.03 × 10^–6 mol/L and 1.89 × 10^–6 mol/L, respectively. The X-ray crystal structure indicated that different coordination fashions were triggered by Zn²⁺ and Cd²⁺ in the CMO@Q[7] complexes, respectively. However, both metal ions coordinated with the carbonyl oxygen of CMO, which was encapsulated in the cavity of Q[7], thus leading to the enhancement of recognition fluorescence emission of CMO.     

Sensitive and rapid determination of nitric oxide in human serum using microchip capillary electrophoresis with laser-induced fluorescence detection

Microfluidic chip capillary electrophoresis with laser-induced fluorescence detection is employed for direct determination of trace nitric oxide in human blood using diaminorhodamines as the fluorescence probe. Factors influencing the separation and detection processes were systematically studied. Complete and fast separation of the highly fluorescent triazole formed was achieved within 45 s, and the relative standard deviations values of migration time and peak area were less than 3%. The detection limit of NO was 3.0 nmol.L^-1 (at a signal-to-noise ratio of 3) and the liner range was from 1.0?×?10^-8?mol.L^-1 to 3.0?×?10^-6?mol.L^-1. The method has been applied to the determination of NO in serum of healthy persons and patients suffering from diseases, with recoveries varying from 92.65 to 98.43%.     

Selective fluorometry of cytochrome c using glutathione-capped CdTe quantum dots in weakly basic medium

Glutathione-capped CdTe quantum dots (GSH-CdTe QDs) were synthesized in aqueous medium. Their interactions with proteins, especially three heme-containing proteins, were investigated over a broad pH range. At 6.0?<?pH?<?8.0, the fluorescence of the GSH-CdTe QDs can be effectively quenched by cytochrome c (Cyt. c) and hemoglobin, respectively. At pH?>?8.0, only cytochrome c quenched the fluorescence of the GSH-CdTe QDs, and no significant fluorescence changes were observed for hemoglobin or other proteins. Based on the distinct fluorescence response, a novel method has been developed for the selective determination of cytochrome c using GSH-CdTe QDs as the fluorescence probe at pH 9.0. Under optimum conditions, the linear range of the calibration curve is from 3.2?×?10^?8 to 2.4?×?10^?6?mol L^?1 and the detection limit is 3.0?×?10^?9?mol L^?1. The method has been applied to the determination of cytochrome c in three synthetic and real samples, and satisfactory results were obtained with QDs through selecting the proper pH value.     

Phthalocyanine-based fluorescent chemosensor for the sensing of Zn (II) in dimethyl sulfoxide-acetonitrile

A tetra-substituted phthalocyanine based on 4-[2-(4-nitrophenoxy)ethoxy]phthalonitrile carrying nitrophenyl group for the sensing of Zn²⁺ has been prepared and characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR, and MS spectral data. The sensing of Zn²⁺ is based on the fluorescence quenching of Pc. Both absorbance and fluorescence spectra of ZnPc exhibit distinct changes in visible region in response to treatment with Zn²⁺ ion in dimethyl sulfoxide. The fluorescence spectrum of the ligand showed quenching in the intensity of the signal at 688?nm for Zn²⁺. The complex composition of ZnPc was found 1:1 by means of spectrophotometric and spectrofluorimetric titration data. The spectrofluorimetric method showed good sensitivity for Zn²⁺ with linear range and detection limit of 4.0?×?10^?6–4.4?×?10^?5 and 2.4×10^?7?M, respectively.     

A Three‐Photon Active Organic Fluorophore for Deep Tissue Ratiometric Imaging of Intracellular Divalent Zinc

Deep tissue bioimaging with three‐photon (3P) excitation using near‐infrared (NIR) light in the second IR window (1.0–1.4 μm) could provide high resolution images with an improved signal‐to‐noise ratio. Herein, we report a photostable and nontoxic 3P excitable donor‐π‐acceptor system (GMP) having 3P cross‐section (σ₃) of 1.78×10^?80 cm⁶ s² photon^?2 and action cross‐section (σ₃η₃) of 2.31×10^?81 cm⁶ s² photon^?2, which provides ratiometric fluorescence response with divalent zinc ions in aqueous conditions. The probe signals the Zn²⁺ binding at 530 and 600 nm, respectively, upon 1150 nm excitation with enhanced σ₃ of 1.85×10^?80 cm⁶ s² photon^?2 and σ₃η₃ of 3.33×10^?81 cm⁶ s² photon^?2. The application of this probe is demonstrated for ratiometric 3P imaging of Zn²⁺ in vitro using HuH‐7 cell lines. Furthermore, the Zn²⁺ concentration in rat hippocampal slices was imaged at 1150 nm excitation after incubation with GMP, illustrating its potential as a 3P ratiometric probe for deep tissue Zn²⁺ ion imaging.     

A selective colorimetric and fluorescence chemosensing sensor for Cr<Superscript>3+</Superscript> based on a rhodamine base derivative

A rhodamine-conjugated coumarin (L) was used in designing a selective fluorescence chemosensor for the determination of trace amounts of Cr³⁺ ions in acetonitrile–water (MeCN/H₂O (90:10, %v/v) solutions. The intensity of the fluoresce emission of the chemosensor is intensified upon addition of Cr³⁺ ions in MeCN/H₂O (90:10, %v/v) solutions, due to the formation of a selective 1:1 complex between L and Cr³⁺ ions. The fluorescence enhancement versus Cr³⁺ concentration has been found to be linear from 1.0?×?10^?7 to 1.8?×?10^?5 M and a detection limit of 7.5?×?10^?8 M. The proposed fluorescent probe proved to be highly selective towards Cr³⁺ ions as compared to other common metal ions and could be successfully applied to the determination of Cr³⁺ concentrations in some water and wastewater samples.     

A fluorescent di-zinc(II) complex of bis-calix[4]arene conjugate as chemosensing-ensemble for the selective recognition of ATP

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate L has been synthesised and characterised. Conjugate L exhibits high fluorescence enhancement towards Zn²⁺ among the 13 metal ions studied down to a lower detection limit of ～12 ppb. The absorption and visual colour change experiments differentiated the Zn²⁺ from the other metal ions studied. The isolated zinc complex, [Zn₂L] has been used as a chemo-sensing ensemble for the recognition of anions based on their binding affinities towards Zn²⁺. [Zn₂L] was found to be sensitive and selective towards phosphate-bearing species and in particular to adenosine triphosphate (ATP^2 ? ) among the other 20 anions studied as observed based on the changes occurred in the fluorescence intensity. The selectivity of the ATP^2 ?  has been shown on the basis of the changes observed in the emission and absorption spectral studies. The lowest detectable concentration for ATP^2 ?  with the chemo-sensing ensemble [Zn₂L] is 348 ppb in methanol. The fluorescence quenching by the phosphate-based anions has been modelled by molecular mechanics studies and found that the anions possessing two or more phosphate moieties can only bridge between the two zinc centres, and hence those possessing only one phosphate moiety (H₂PO₄^?  and AMP^2 ? ) are ineffective.     

Differential Detection of Zn2+ and Cd2+ Ions by BODIPY‐Based Fluorescent Sensors

Two monostyryl BODIPY derivatives that contain one or two bis(hydroxyamido)amino group(s) as the metal chelator have been prepared. The effects of various metal ions on their electronic absorption and fluorescence properties have been studied in detail in MeCN or in phosphate buffered saline (PBS). The results show that the derivative with two hydroxyamide chains can selectively detect Zn²⁺ ions in MeCN. The compound and ions bind in a 1:1 stoichiometry with an association constant of 2.2(±0.1)×10⁴ M ^?1. The intensity of the fluorescence emission increases remarkably and is substantially blue‐shifted from 624 to 572 nm, owing to the inhibition of intramolecular charge transfer, thus allowing its use as a ratiometric fluorescent sensor for Zn²⁺ ions. The derivative with four hydroxyamide chains behaves differently: It responds selectively toward Cd²⁺ ions in phosphate buffered saline. The compound and ions bind in a 1:2 stoichiometry, with first and second association constants of 4.4(±0.9)×10⁴ M ^?1 and 1.3(±0.1)×10⁴ M ^?1, respectively. Upon the addition of 80 equivalents of Cd²⁺ ions, the fluorescence quantum yield increases 15‐fold. Both of these compounds exhibit differential sensing of Zn²⁺ and Cd²⁺ ions and the associated color changes can be easily seen by the naked eye.