A simple dual-channel sensor for detecting cyanide in water with high selectivity and sensitivity

Taking advantage of the special nucleophilicity of cyanide, a new simple colorimetric chemosensor has been synthesised. This allows a deprotonation reaction to monitoring the cyanide. With the addition of CN^? to the chemosensor aqueous solution, which could induce a change in the solution colour from yellowish to deep yellow, while no colour change could be observed in the presence of other hackneyed anions, by which CN^? can be distinguished from other anions immediate with the naked eye. At the same time, a fluorescence quenching was implemented upon adding cyanide into the chemosensor aqueous solution. The absorption spectra detection limits of the chemosensor for cyanide was 5.35 × 10^?8 M and the fluorescence spectra detection limit was 2.63 × 10^?8 M. The cyanide test strips based on the chemosensor could serve as a convenient cyanide test kits. Furthermore, the chemosensor was successfully applied to detect cyanide in sprouting potatoes.     

A novel and synthetically facile coumarin-thiophene-derived Schiff base for selective fluorescent detection of cyanide anions in aqueous solution: Synthesis,anion interactions,theoretical study and DNA-binding properties

A colorimetric and fluorescent chemosensor (chemosensor 2) for the detection of cyanide anions in aqueous solution has been designed and synthesized in high yield. The sensing mechanism of the chemosensor was verified via UV–vis, fluorimetric, and NMR titrations, and was theoretically explained using DFT and TD-DFT calculations. The chemosensor could optically discriminate the presence of fluoride ions over other anions by a color change from yellow to red with an enhancement of pink fluorescence in DMSO. However, it showed strong green fluorescence when CN^? was added to a mixture of DMSO/water (6:4 v/v). Thus, the chemosensor can be employed in selective detecting of CN^? besides other interference anions (F^?, AcO^? and H₂PO₄^?) in aqueous solution. Moreover, 2 can be used to detect CN^? at a concentration as low as 0.32?μM, which is lower than the WHO guideline (2.7?μM) for cyanide. A low quantity of CN^? (1.08?μM) can be detected and quantified using the prepared chemosensor. Moreover, the UV–vis and fluorescence spectroscopy studies of the interactions between 2 and dublex DNA revealed intercalative binding of calf thymus DNA to the chemosensor.     

New chemosensory materials based on disubstituted polyacetylene with strong green fluorescence

A new imidazole‐containing disubstituted polyacetylene ( P1 ) with strong green fluorescence was successfully prepared through polymer reaction, which was nearly impossible to be obtained from the direct polymerization of its corresponding monomer. The polymer was soluble in common organic solvents, and its strong green fluorescence could be quenched completely by the Cu²⁺ and Co²⁺ ions, at the concentrations as low as 1.33 and 1.67 × 10⁻⁵ mol/L (0.85 and 0.92 ppm), respectively. Because of the high stability of the complex formed by cyanide and copper ions, the quenched green fluorescence of P1 by copper ions could be turned on upon the addition of trace cyanide (as low as 2.70 × 10⁻⁵ mol/L, 0.70 ppm), making P1 a new sensitive cyanide chemosensor. The results thus provided a new opportunity to develop anion chemosensors based on good cation chemosensors. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8070–8080, 2008     

Selective colorimetric assay of cyanide ions using a thioamide-based probe containing phenol and pyridyl groups

The selective assay of cyanide ions with a thioamide compound (HNPTU) containing phenol and pyridine as a chemosensor is reported using absorbance changes in a buffered aqueous solution (50 mM HEPES, pH 7.4) containing ethanol. Upon treatment with cyanide ions, the colorless solution of HNPTU turned yellow. No significant changes were observed with other comparable anions, such as F⁻, Cl⁻, Br⁻, I⁻, and CH₃COO⁻. The color change of HNPTU upon treatment with CN⁻ was maintained even in the presence of the comparable monovalent anions. The complex stability constant (K_a = 2.6 × 10³) for the stoichiometric 1:1 complexation of HNPTU with cyanide ions was obtained based on absorbance titrations. The interaction of HNPTU with cyanide ions was proposed to be deprotonation, as shown by NMR and Cu(II) treatment experiments.     

A TD‐DFT study on the cyanide‐chemosensing mechanism of 8‐formyl‐7‐hydroxycoumarin

Proton transfer (PT) and excited‐state PT process are proposed to account for the fluorescent sensing mechanism of a cyanide chemosensor, 8‐formyl‐7‐hydroxycoumarin. The time‐dependent density functional theory method has been applied to investigate the ground and the first singlet excited electronic states of this chemosensor as well as its nucleophilic addition product with cyanide, with a view to monitoring their geometries and spectrophotometrical properties. The present theoretical study indicates that phenol proton of the chemosensor transfers to the formyl group along the intramolecular hydrogen bond in the first singlet excited state. Correspondingly, the nucleophilic addition product undergoes a PT process in the ground state, and shows a similar structure in the first singlet excited state. This could explain the observed strong fluorescence upon the addition of the cyanide anion in the relevant fluorescent sensing mechanism. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011     

Facile synthesis of rhodamine-based highly sensitive and fast responsive colorimetric and off-on fluorescent reversible chemosensors for Hg2+: preparation of a fluorescent thin film sensor

Fluorescence-active chemosensors (L1-L4), comprising a rhodamine scaffold and a pseudo azacrown cation-binding subunit, have been proposed and characterized as a fluorescent chemosensor for Hg(2+). An on-off type fluorescent enhancement was observed by the formation of the ring-opened amide form of the rhodamine moiety, which was induced by the interactions between Hg(2+) and the chemosensor. Upon the addition of Hg(2+), an overall emission change of 350-fold was observed, and the selectivity was calculated to be 300 times higher than Cu(2+) for receptors L2-L4. A polymeric thin film can be obtained by doping poly(methyl methacrylate) or PMMA with chemosensor L2. Such a thin film sensor can be used to detect Hg(2+) with high sensitivity and can be recovered using diluted NaOH.     

A highly sensitive and selective chemosensor for cyanide

A highly sensitive and selective cyanide chemosensor based on fused indoline and benzooxazine fragment was reported with fast response. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the oxazine. (1)H NMR and MS studies confirmed the cleavage of C-O bond of oxazine and binding of cyanide to the spiro center of oxazine. The specific reaction results in high selectivity for cyanide ion. Addition of cyanide anion to the oxazine in MeCN/H(2)O solution results in a loss in absorbance at 343 nm and an increase in new absorbance at 411 nm, thus resulting in obvious color changes. Cyanide can be detected down to 1 microM levels in a fast response of less than 30s with no interference of other anionic species. The cyanide detection method should have potential application in a variety of settings requiring rapid and accurate analysis of cyanide anion for drinking and fresh water.     

A green synthesis of a simple chemosensor that could instantly detect cyanide with high selectivity in aqueous solution

A novel and simple cyanide chemosensor 2-(naphthalen-1-ylmethylene)malononitrile(L) was designed and synthesized via a green chemistry method in water without using any catalyst.The chemosensor showed an excellent sensitivity and selectivity for CN in aqueous solution.The detection limit could be as low as 1.6×10~7 moI/L(0.16μmol/L),which is far lower than the WHO guideline of 1.9μmol/L cyanide for drink water.     

A photochromic phenoxyquinone based cyanide ion sensor

We have developed a new chemosensor system for cyanide ion that is based on a photochromic material. We observed that addition of cyanide anion to a UV irradiated solution of a phenoxynaphthacenequinone derivative brought about a significant change in the absorption spectra that enabled detection of cyanide ion in a selective and sensitive manner. A carbanion intermediate was shown to be responsible for the long wavelength absorption band (630-940 nm) that is generated by cyanide addition.     

A highly selective colorimetric and turn-on fluorescent probe for cyanide anion

A new colorimetric and turn-on fluorescence chemosensor was developed for cyanide anion with high selectivity in the presence of other anions in an aqueous THF solution. The sensing mechanism is attributed to the interruption of π-conjugation by a nucleophilic addition of cyanide to the β-position of a dicyanoethylene unit.     

A highly selective and synthetically facile aqueous-phase cyanide probe

Disperse Orange 3 (4-(4-nitrophenylazo)aniline)-based chemosensor 1 has been prepared. This structurally simple receptor displays great selectivity for the cyanide anion over other common inorganic anions in aqueous environment and can detect cyanide in water sample at micromolar concentrations.     

Naked-eye detection of cyanide ions in aqueous media based on an azo-azomethine chemosensor

The optical and colorimetric properties of a new chemosensor 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino)methyl)phenol (L) for cyanide ions were investigated by the naked-eye detection and UV–vis spectroscopy. This receptor reveals visual changes toward CN⁻ anions in aqueous media. No significant color changes were observed upon the addition of any other anions. The cyanide recognition properties of the receptor through proton-transfer were monitored by UV–vis titration and ¹H NMR spectroscopy. The binding constant (K_a) and stoichiometry of the formed host–guest complex were calculated by the Benesi–Hildebrand (B–H) plot and Job's plot method, respectively. The detection limit of the probe towards CN⁻ was 1.03 × 10⁻⁶ mol L⁻¹, which is lower than the maximum value of cyanide (1.9 × 10⁻⁶ mol L⁻¹) permitted by the World Health Organization in drinking water. Thus, this chemosensor was sensitive enough to detect cyanide in aqueous solutions. ¹H NMR experiments were conducted to investigate the nature of interaction between the receptor and CN⁻ anions. Notably, the designed sensor can be applied for the rapid detection of cyanide anions in the basic pH range and also under physiological conditions, for practical purposes for a long duration. The sensing behavior of the receptor was further emphasized by computational studies. Quantum-chemical calculations and molecular studies via Density Functional Theory (DFT) were carried out to supplement the experimental results.     

New imidazole‐functionalized polyfluorene derivatives: convenient postfunctional syntheses,sensitive probes for metal ions and cyanide,and adjustable output signals with diversified fluorescence color

Based on our previous work on the sensitive and selective conjugated fluorescent polymeric sensors toward cyanide, 2,1,3‐benzothiadiazole and 4,7‐bis(thiophen‐2‐yl)‐2,1,3‐benzothiadiazole were incorporated into the polyfluorene backbone to yield three new polymers bearing imidazole moieties in the side chains, with different fluorescence color. The fluorescence could be turned off by Cu²⁺ ions and then recovered on addition of cyanide, making them good cyanide sensors with the detection limit down to 1.9 μM. Moreover, by fully understanding this “turn off–turn on” strategy and using the cooperation of two polymers with different fluorescence color, the emission color of the mixture system of one of the imidazole‐containing polymers and one from the corresponding polymers without imidazole ones, could be adjusted by the concentrations of the added copper and cyanide ions, leading to the output fluorescent signals diversity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Rhodamine-based highly sensitive colorimetric off-on fluorescent chemosensor for Hg2+ in aqueous solution and for live cell imaging

A novel rhodamine-based highly sensitive and selective colorimetric off-on fluorescent chemosensor for Hg(2+) ions is designed and prepared by using the well-known thiospirolactam rhodamine chromophore and furfural hydrazone as signal-reporting groups. The photophysical characterization and Hg(2+)-binding properties of sensor RS1 in neutral N, N-dimethylformamide (DMF) aqueous solution are also investigated. The signal change of the chemosensor is based on a specific metal ion induced reversible ring-opening mechanism of the rhodamine spirolactam. The response of the chemosensor for Hg(2+) ions is instantaneous and reversible. And it successfully exhibits a remarkably "turn on" response toward Hg(2+) over other metal ions (even those that exist in high concentration). Moreover, this sensor is applied for in vivo imaging in Rat Schwann cells to confirm that RS1 can be used as a fluorescent probe for monitoring Hg(2+) in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.     

DDTC-Na-based colorimetric chemosensor for the sensing of cyanide in water

Sodium diethyldithiocarbamate (DDTC-Na) was demonstrated to be a new colorimetric cyanide chemosensor by utilizing an indirect trick. First, some copper ions were added to the colorless aqueous solution of DDTC-Na. Then, the resultant brown solution was studied upon the addition of different anions, including Cl⁻, I⁻, IO₃⁻, SO₄²⁻, NO₂⁻, Br⁻, H₂PO₄⁻, F⁻, SCN⁻, HSO₄⁻, ClO₄⁻ and CN⁻. It was observed by naked eyes that the brown solution changed to colorless immediately after the addition of the trace cyanide, but there were no changes towards other anions, making DDTC-Na a good selective cyanide chemosensor in pure water. Supported by the National Natural Science Foundation of China (Grant Nos. 20674059 & 20402011)     

RAFT方法合成的共聚物荧光探针及其氟离子检测性能

本文基于分子间质子转移和诱导分子内电荷转移（ICT）机理,合成了以萘酰亚胺为发光基团、苯甲酰为F^-检测基团的荧光单体,并采用可逆加成-断裂链转移（RAFT）聚合方法将其与N-异丙基甲基丙烯酰胺（NIPAM）进行共聚,制备了一种可以用于F^-检测的共聚物荧光探针poly（NIPAM_m-co-Nap_n）（简称PNap334）,并分别在二氯甲烷-二甲基亚砜（9/1,V/V）溶液和固体薄膜中考察了聚合物PNap334对F^-的响应。研究发现,聚合物溶液和聚合物膜对F^-均有很好的识别作用,聚合物溶液对F^-的检测限为1.05 μmol/L。     

Rational design of a dual chemosensor for cyanide anion sensing based on dicyanovinyl-substituted benzofurazan

A dicyanovinyl-substituted benzofurazan derivative (C1) was prepared as an efficient ratiometric chemosensor for cyanide anion detection in aqueous acetonitrile solution. Mechanism studies suggested that the nucleophilic addition of cyanide to the α-position of the dicyanovinyl group blocked the ICT progress of C1 and induced remarkable emission and absorption shift.     

A fluorescence chemosensor based on peptidase for detecting nickel(II) with high selectivity and high sensitivity

We report herein a new class of metal ion chemosensors and give the first example of a metal-dependent peptidase chemosensor for metal ions. The chemosensor contains the basic specific Ni(II)-dependent peptide bond hydrolysis sequence (Gly-Ala-Ser-Arg-His-Trp-Lys-Phe-Lys). The substrate was labeled with a fluorophore at the N-terminal and a quencher at the C-terminal Lys side chain. Initially, the MOCAc ((7-methoxycoumarin-4-yl)acetyl-) emission was quenched by the nearby quencher. In the presence of Ni(II), the substrate was irreversibly cleaved at the cleavage site, leading to a 20-fold increase in fluorescence intensity. The chemosensor combines the high selectivity of a peptidase (at least greater than tenfold for Ni(II) over other metal ions) with the high sensitivity of fluorescence detection limit of 50 nM and can be applied for the quantitative detection of Ni(II) over a concentration range of three orders of magnitude. Given this degree of selectivity and sensitivity, our molecular engineering design may prove useful in the future development of other peptidase-based probes for different metal ions in toxicological and environmental monitoring.     

A new "turn-on" naphthalenedimide-based chemosensor for mercury ions with high selectivity: successful utilization of the mechanism of twisted intramolecular charge transfer, near-IR fluorescence, and cell images

For the first time, a new near-IR "turn-on" fluorescent chemosensor with high selectivity for Hg(2+) ions was designed according to the twisted intramolecular charge transfer (TICT) mechanism. The selective fluorescence enhancement effect can be optimized by modulating the solvent systems. And this naphthalenedimide-based sensor with long wavelength absorption and emission can be used to image intracellular Hg(2+) ions in living Hela cells.     

A novel fluorescent epoxy resin for organophosphate pesticide detection

In this work,a novel bisbenzimidazolylpyridine-functionalized fluorescent epoxy resin was synthesized for organophosphate pesticide detection.The epoxy resin was characterized by Fourier-transform infrared spectroscopy(FT-IR),proton nuclear magnetic resonance spectroscopy(~1H NMR),gel permeation chromatography(CPC),differential scanning calorimetry(DSC) and fluorescence spectroscopy.After loading with Eu(Ⅲ) ions,the epoxy resin showed a strong fluorescence emission.The fluorescence emission was observed to be instantaneously quenched when exposed to trace amount of diethyl chlorophosphate in solution.The Stern-Volmer quenching constants K_(sv) for quenching at617 nm was determined to be 0.377 × 10~3 L/mol.This sensitive emission-quenching function and easy processing nature of the polymeric support enable the resin to be a promising chemosensor candidate for the detection of organophosphates.