A colorimetric and fluorescent turn-on chemosensor for Zn based on an azobenzene-containing compound

This paper presents a new colorimetric reversible fluorescent turn-on chemosensor molecule for zinc ion based on an azobenzene derivative. The basal fluorescence intensity of the chemosensor molecule is little affected under physiological pH 5-9, whilst the excitation (507 nm) and emission (610 nm) wavelength of the molecular probe for zinc ion is in the visible range.     

A highly selective and sensitive fluorescent chemosensor for Zn^2＋

A new selective Zn^2＋ fluorescent chemosensor, o-vanillin-4-ethoxybenzoylhydrazone （1）, was designed and prepared. Free 1 mainly displayed very weak fluorescence at 480 nm upon excitation at 403 nm. It displayed high selectivity for Zn^2＋ and had a 518- fold fluorescent enhancement upon binding of Zn^2＋, while the other cation ions had only little influence on the fluorescence of 1. Mechanism of enhancement of l＇s fluorescence by Zn^2＋ was briefly discussed.     

A fluorescent and colorimetric chemosensor for selective detection of aluminum in aqueous solution

We have synthesized a new Schiff base 1, which detects Al³⁺ through fluorescence and naked eye in aqueous solution. The sensor 1 exhibited selective and sensitive recognition toward Al³⁺ via significant fluorescence enhancement (31-fold). Moreover, it showed a significant color change from colorless to yellow. The complex formation was proposed to be 1:1 ratio, based on the Job plot, ESI-mass spectrometry analysis, ¹H NMR titration, and IR analysis. The detection limit was 1.00 μM, which is below the WHO acceptable limit (1.85 μM) in drinking water. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA.     

A colorimetric and ratiometric fluorescent chemosensor based on furan-pyrene for selective and sensitive sensing Al3+

A new pyrene derivative BF bearing a furan group was synthesized via a one-step reaction as a colorimetric and ratiometric chemosensor for Al³⁺in ethanol-H₂O (9:1,v/v,pH 7.2,HEPES buffer) solution.This chemosensor could selectively recognize Al³⁺ in the presence of other competing ions.Low limit of detection (LOD) and high association constant revealed its superior sensitivity and binding affinity toward Al³⁺.Besides,the probe BF performed perfectly in a reversibility test using EDTA.The mechanism of the interaction has been confirmed by ¹H NMR titration.Importantly,chemosensor BF has also been utilized to detect Al³⁺ on test paper strips,which showed its potential for practical applications.     

A colorimetric and fluorescent chemosensor for detection of Hg2+ using counterion exchange of cationic polydiacetylene

In this study, a colorimetric and fluorescent chemosensor for mercury ions (Hg²⁺) was developed. Cationic polydiacetylene (PDA) vesicles with a quaternary ammonium cation and iodide as a counterion show a blue-to-red color transition; the color change is accompanied by a fluorescence enhancement in selective response to Hg²⁺ ions because of a perturbation of the ene–yne conjugated backbone induced by counterion exchange. It allows for selective detection of Hg²⁺ with the naked eye and the sensor is used to determine Hg²⁺ concentrations in tap water samples.     

A new rhodamine-based fluorescent chemosensor for mercury in aqueous media

A new fluorescent ‘‘on–off' chemosensor for Hg2+initiated by a derivative of rhodamine B was designed and synthesized. Compound 1 exhibited high sensitivity and selectivity for Hg2+over other commonly coexistent metal ions in aqueous media. Upon the addition of Hg2+, the spirocyclic ring of probe is opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm is observed. The colorimetric and fluorescent response to Hg2+can be conveniently detected by the naked eye, which provides a facile method for visual detection of Hg2+. From the molecular structure and spectral results of 1, an irreversible, hydrolysis, desulfurization reaction mechanism is proposed.     

A novel colorimetric chemosensor based on quinoline for the sequential detection of Fe3+ and PPi in aqueous solution

A novel quinoline-functionalized Schiff-base derivative PY was designed and synthesized. Sensor PY displayed highly selective and sensitive fluorescence enhancement and naked-eye color change to Fe³⁺ in the presence of other competing cations. The mechanisms have been supported by Job’s plot evaluation, FT-MS and theoretical calculations. The in situ generated PY-Fe³⁺ complex solution exhibited a high selectivity toward PPi via Fe³⁺ displacement approach. The detection limits of sensor PY to Fe³⁺ and PY-Fe³⁺ complex to PPi were estimated to be 4.24 × 10^?8 M and 8.18 × 10^?8 M, respectively. This successive recognition feature of sensor PY makes it has a potential utility for Fe³⁺ and PPi detection in aqueous solution. A B3LYP/6-31G(d,p) basis set was employed for optimization of PY and PY-Fe³⁺ complex.     

A simple highly sensitive and selective turn-on fluorescent chemosensor for the recognition of Pb2+

A simple highly sensitive and selective turn-on fluorescent chemosensor L based on bis-Schiff-base for Pb²⁺ ions was synthesized and characterized by spectroscopic techniques. L having high binding affinity towards Pb²⁺ ions of 2.10 × 10⁴ M^?1 selectively detects Pb²⁺ ions with almost no interference among various competitive ions by a 11-fold fluorescent enhancement in CH₃CN/H₂O (95:5, v/v) solution over a wide pH range. Moreover, sensor L displayed a lower detection limit of 3.80 × 10^?7 M, which is low enough for sensing sub-millimolar concentration of Pb²⁺ encountered practically.     

A coumarin-based colorimetric and fluorescent probe for the highly selective detection of Au3+ ions

We develop a novel coumarin-alkyne derivative(NC7-AL), which can specifically react with Au~(3+) and give a colorimetric and fluorescent ‘‘turn-on' response toward Au~(3+). Notably, other alkynophilic metal species such as Au+, Ag+, Pd~(2+), Ni~(2+), Cu~(2+), and Hg~(2+) do not produce an interfering signal. A good linear relationship between emission intensity at 420 nm and Au~(3+) concentration from 0 to 2 equivalent is observed, and the detection limit(3s/k) is estimated to be ca. 3.58 nmol/L. Harnessing the Au~(3+)-induced color change from light yellow to colorless, we find that NC7-AL-based modified TLC plate can be used for convenient naked-eye detection of Au~(3+).     

A colorimetric chemosensor based on new water-soluble PODIPY dye for Hg2+ detection

The phosphorus-containing PODIPY 1 as a chemosensor can detect Hg~(2+) by a color change from pink to violet red without the use of any instrumentation. PODIPY 1 was selective to Hg~(2+)with a remarkable absorption change, and addition of other relevant metal ions caused almost no absorption change. The new PODIPY dye 1 was sensitive to various concentrations of Hg~(2+). The energy gap between the HOMO and LUMO of the metal complex 1–Hg~(2+)is smaller than that of chemosensor 1, which is in good agreement with the red shift in the absorption observed upon treatment of 1 with Hg~(2+). The 1-based test strips were easily fabricated and low-cost, useful in practical and efficient Hg~(2+)test kits.     

A TCF-based colorimetric and fluorescent probe for palladium detection in an aqueous solution

A new fluorescent probe (TCF-AC) that contains 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) skeleton has been developed. Probe TCF-AC exhibits highly selective and sensitive detection toward Pd⁰ in EtOH/H₂O (1:1, v/v, PBS 20?mM, pH?=?7.4) solution with fluorescence “turn on” and colorimetric changes. The Pd⁰ detection by TCF-AC holds some advantages including good anti-interference ability, a relative large Stokes shift (>100?nm), and a low detection limit (7.05?×?10^?7?M). Cell imaging studies demonstrate that TCF-AC is applicable to detect Pd⁰ in living HeLa cells.     

A highly selective fluorescent chemosensor for Pb2+

A new fluorescent sensor based on rhodamine B for Pb2+ was synthesized. The new fluorescent sensor showed an extreme selectivity for Pb2+ over other metal ions examined in acetonitrile. Upon the addition of Pb2+, an overall emission change of 100-fold was observed, and the selectivity was calculated to be 200 times that of Zn2+. The signal transduction occurs via of reversible CHEF (chelation-enhanced fluorescence) with this inherent quenching metal ion.     

A highly selective and colorimetric naked-eye chemosensor for Cu2+

A sample and practical colorimetric naked-eye chemosensor 3-nitro-4-ethylenediamido-nitrobenzene (2) for metal cations was designed and synthesized. It displays high selectivity and sensitivity for Cu2+ by the UV absorption which appeared a new peak at 525 nm and color change from yellow to red by naked-eye in CH3OH/H2O pH 7.6.     

Novel,highly selective detection of Cr(III) in aqueous solution based on a gold nanoparticles colorimetric assay and its application for determining Cr(VI)

A simple, rapid, sensitive and field-portable colorimetric technique for the determination of Cr(III) in aqueous solution based on an aggregation-induced color transition of gold nanoparticles (AuNPs) has been developed. AuNPs were first functionalized with a dithiocarbamate-modified N-benzyl-4-(pyridin-4-ylmethyl)aniline ligand (BP-DTC). Chelation of Cr(III) by several of these ligands, bound to different nanoparticles, led to nanoparticle aggregation in solution. This gave rise to a color change from wine-red to blue that was discernible by the naked eye and an easily measurable alteration in the extinction spectrum of the particles. The method could be used to determine Cr(III) with a detection limit of 31 ppb. Furthermore, selective detection of trace Cr(III) in aqueous solution in the presence of 12 other transition metal ions has been achieved. Toward the goal of practical applications, the sensor has been further evaluated with a view to monitoring Cr(III) in nutritional supplements and the blood of diabetes patients and also applied in the indirect determination of Cr(VI) in waste water.     

Synthesis of organic nanoparticles of naphthalene-thiourea-thiadiazole-linked molecule as highly selective fluorescent and colorimetric sensor for Ag(I)

A novel fluorescent and colorimetric sensor was synthesized by a reprecipitation to probe Ag⁺ ions in water on naphthalene-thiourea-thiadiazole (NTTA) molecular nanocrystals. The fluorescent organic nanoparticles (FONs) allowed a highly sensitive determination of free Ag⁺ ions in aqueous media. The possible mechanism was discussed.     

A tetra-sulfonamide derivative bearing two dansyl groups designed as a new fluoride selective fluorescent chemosensor

A new fluorescent chemosensor based on an acyclic tetra-sulfonamide derivative linked to two dansyl groups has been conveniently synthesized. Its high selective binding ability to fluoride ions over other halide ions was demonstrated by using fluorescence as well as ¹H NMR spectra.     

A highly selective and sensitive fluorescent chemosensor for Hg2+ in neutral buffer aqueous solution

A selective and sensitive fluorescent chemosensor for Hg2+, which was composed of two aminonaphthalimide fluorophores and a receptor of 2,6-bis(aminomethyl)pyridine, was synthesized through the reaction of 2,6-bis(chloromethyl)pyridine and N-[2-(2-hydroxyethoxy)ethyl]-4-piperazino-1,8-naphthalimide. The chemosensor showed an about 17-fold increase in fluorescence quantum yield upon addition of 1 equiv of Hg2+ in neutral buffer aqueous solution, and the other common metal ions did not notably disturb the detection of Hg2+.     

A coumarin based highly selective fluorescent chemosensor for sequential recognition of Cu2+ and PPi

In this study, we have successfully synthesized a new coumarin based fluorescent chemosensor 1, in which tren and quinolone are introduced as receptors for sequential recognition of Cu²⁺ and PPi. The structure of chemosensor 1 was characterized by ¹H NMR, ¹³C NMR and ESI-HR-MS. Sensor 1 showed an obvious “on-off” fluorescence quenching response toward Cu²⁺, and the quenching efficiency reached a maximum of 99.6% with the addition of 20 equiv. of Cu²⁺. The 1-Cu²⁺ complex showed an “off-on” fluorescence enhancement response toward PPi over many competitive anions, especially HPO₄^2? and H₂PO₄^?. The detection limit of sensor 1 was 1.9?×?10^?6?M to Cu²⁺ and 5.96?×?10^?8?M to PPi. In addition, sensor 1 showed a 1:1 binding stoichiometry to Cu²⁺ and sensor 1-Cu²⁺ showed a 2: 1 binding stoichiometry to PPi in CH₃CN/HEPES buffer medium (9:1 v/v, pH?=?7.4). The stable pH range of sensor 1 to Cu²⁺ and 1-Cu²⁺ to PPi was from 4 to 8.     

Dipodal fluorescent chemosensor for Cu and resultant complex as a chemosensor for iodide

A dipodal receptor was synthesized by condensation of isophthalaldehyde and p-toluenesulfonylhydrazide. The receptor was found to be selective for Cu²⁺ recognition in CH₃CN. The resultant Cu²⁺ receptor complex selectively recognized iodide through cation displacement assay in a CH₃CN/H₂O (8:2, v/v) solvent system.     

A new selective phenanthroline-based fluorescent chemosensor for Co

An intramolecular charge transfer (ICT) chromophore 2-(2-pyridine)imidazo [4,5,f]-1,10-phenanthroline (1) has been synthesized and firstly used as a chemosensor with a reversible, ‘on-off’ sensing capability for biologically and environmentally significant Co²⁺ in DMF under buffered conditions. The experiment results also show that the response behavior of 1 to Co²⁺ is pH independent in range of pH 3.0-7.0 and show excellent selectivity for Co²⁺ over other cations.