Simple Colorimetric Chemosensor Research Articles

A simple and efficient pyrazole based colorimetric chemosensor for sensing Hg2+, Zn2+, Cu2+ ions and a selective sensing of Hg2+ ions in the presence of Zn2+and Cu2+ ions and its application in real samples

A simple colorimetric chemosensor (E)-4((4-diethylamino)-2-hydroxybenzylidene)amino)-1,5-dimethyl-2-phenyl-1,2, dihydro-3H-pyrazole-3-one (M2) was synthesized and characterized by NMR, Mass spectra, IR and UV spectra, along with solvatochromism. The synthesized compound showed colorimetric sensing towards Hg2+ ion with high selectivity and sensitivity. The UV–Vis absorption spectra studies demonstrated that the proposed sensor could detect Hg2+ directly in acetonitrile solution over other metal ions. In the presence of Hg2+ ion, the probe exhibits instantaneous color change from colorless to yellow as a naked-eye detection. The binding ratio of the probe with metal has been identified to be of 1:1 using Job’s Plot and the obtained limit of detection is 8.83 × 10−8 M. The binding interaction of probe with the Hg2+ is confirmed using 1H NMR titration, ESI mass, and DFT calculation.

Colorimetric detection of iodide ion by a nuclear fast red-based Hg2+ complex in aqueous media

The simple mixture of nuclear fast red (NFR) and Hg2+ containing poly(diallyldimethylammonium chloride) (PDADMAC) was found to be colorimetric detection for iodide ion in aqueous solution via the indicator displacement assay. NFR was complexed with Hg2+ in a 2:1 molar ratio (NFR2-Hg2+) and showed a bathochromic shift in the absorption peak. The addition of iodide ion to NFR2-Hg2+ displayed a hypsochromic shift with change back of color from reddish violet to pink by the restoration of NFR. The detection of iodide ion was not significantly affected by other anions. Therefore, NFR2-Hg2+ containing PDADMAC has been used as a simple colorimetric chemosensor for iodide ion in aqueous solution.

A Schiff base-based ratiometric chemosensor conjugated NBD derivative with the large Stokes shift for formaldehyde detection

A simple colorimetric chemosensor conjugated NBD derivative was synthesized for the detection of formaldehyde (FA) in DMSO/KHP buffer (50% v/v, pH 4.0). Phenylenediamine was designed as a reactive site for FA through the formation of Schiff base. Upon the addition of FA, the color solution of the sensor 1 changed from yellow to deep-purple, observed by naked-eyes. The ratiometric sensor in the presence of FA exhibited an intense absorption band of the red shift from 485 nm to 582 nm. The sensor was highly selective toward FA among other reactive carbonyl species, reactive oxygen species, amino acids, and food additives in 50% DMSO/KHP buffer. The sensor could be utilized in quantitative analysis for FA with the linear relationship in the concentration range of 0–6.5 mM. The product of the sensor and FA was also investigated by 1H NMR, 13C NMR, and HRMS analysis. Furthermore, the paper-based sensor was successfully developed for FA sensing.

Pyrene based chemosensor for carbon dioxide gas – Meticulous investigations and digital image based RGB analysis

A new pyrene Schiff base (KB-4) was synthesized and demonstrated as simple colorimetric chemosensor for carbon dioxide (CO2) gas activated by fluoride anion. The chemical structure of KB-4 was validated through pivotal characterization methods. A combined quantum chemical calculations and spectroscopic techniques were adopted to understand the photophysical properties of KB-4. The sensitivity of KB-4 chemosensor towards various anions is investigated and showed excellent selectivity towards F− anion with a distinct color change. The mechanism of F− anion sensing is due to the complete deprotonation of –NH proton in KB-4 as revealed by 1H NMR titration studies as well as DFT calculations. Subsequently, the in-situ deprotonated KB-4 is employed for CO2 gas sensing. Interestingly, deprotonated KB-4 is responded instantaneously to CO2 gas by exhibiting significant colorimetric and fluorimetric changes with a detection limit of 0.4 ml. Further, digital image based RGB analysis using smartphone is introduced for detection of CO2 gas. The digital images of CO2 gas induced fluorimetric changes are captured using smartphone and the RGB analysis of the images are processed using MATLAB. The intensity variation in the color components as an indicative measure for detection of CO2 gas is demonstrated.

A Saccharide Chemosensor Array Developed Based on an Indicator Displacement Assay Using a Combination of Commercially Available Reagents.

Herein, a very simple colorimetric chemosensor array is reported for saccharides (D-glucose, D-fructose, D-xylose, D-galactose, D-mannose, L-rhamnose, and N-acetyl-D-gluosamine). While various types of chemosensors for saccharides have been investigated extensively to-this-date, tremendous additional efforts are still required on a regular basis for the syntheses of new chemosensors. Complicated syntheses would be a bottleneck, given that artificial receptor-based chemosensing systems are not so popular in comparison to biomaterial-based (e.g., enzyme-based) sensing systems. Toward this end, chemosensor array systems using molecular self-assembled materials can avoid the abovementioned synthetic efforts and achieve simultaneous qualitative and quantitative detection of a number of guest saccharides. Using a practical approach, we focus on an indicator displacement assay (IDA) to fabricate a chemosensor array for colorimetric saccharide sensing. On this basis, 3-nitrophenylboronic acid (3-NPBA) spontaneously reacts with catechol dyes such as alizarin red S (ARS), bromopyrogallol red (BPR), pyrogallol red (PR), and pyrocatechol violet (PV), and yields boronate ester derivatives with color changes. The addition of saccharides into the aqueous solution of the boronate esters induces color recovery owing to the higher binding affinity of 3-NPBA for saccharides, thus resulting in the release of dyes. By employing this system, we have succeeded in discriminating saccharides qualitatively and quantitatively with a classification success rate of 100%. Most importantly, our chemosensor array has been fabricated by only mixing low cost commercially available reagents in situ, which means that complicated synthetic processes are avoided for saccharide sensing. We believe this simple colorimetric assay that uses only commercially available reagents can create new, user-friendly supramolecular sensing pathways for saccharides.

Simple colorimetric chemosensors for detection F- ion based on phenyl urea derivatives

Abstract Colorimetric receptors 1-[2-(4-nitrobenzylideneamino)phenyl]-3-phenylurea (R1) and 1-[2-(2-hydroxy-5-nitrobenzylideneamino)phenyl]-3-phenylurea (R2) were synthesized and characterized by elemental and spectroscopic methods. Anion sensing behaviour of ssynthesized molecules were analyzed that showed a distinct color change only when treated with fluoride ions (F-) in the naked-eye experiment also supported by electronic spectral titration methods. NMR spectral titration method confirms the hydrogen bond formation between F- with OH and NH protons of R2.

A simple colorimetric chemosensor with highly performance for detection of cyanide and copper ions and its practical application in real samples

Two novel and simple azo-based compounds with electron-withdrawing and electron-donating groups (M1 and M2) were synthesized by the diazotization procedure. The synthesized compounds were then applied for detection of important ions in aqueous solutions of acetonitrile. Sensor M1 with electron-withdrawing group (EWG) showed distinct colorimetric responses towards CNˉ (light yellow to red) and Cu2+ (light yellow to dark yellow). Through titration experiment, the detection limit (LOD) of M1 for CNˉ and Cu2+ ions sensing were found to be nano molar (nM) level. Job’s plot based on spectroscopic data showed the complexes formation between M1 and ions has the stoichiometric ratio of 1:1 (M1-CNˉ and M1-Cu2+). In addition, the binding constants for M1 towards CNˉ and Cu2+ were determined using the Benesi-Hildebrand equation. Furthermore, the M1-based test papers strips were successfully used to the rapid detection of CNˉ ions in semi‐aqueous medium. Importantly, sensor M1 was applied to detect CNˉ and Cu2+ in real water samples and apple seeds samples. However, for M2, containing electron-donating group (EDG), no clear color changes were observed in the presence of investigated ions.

A simple colorimetric chemosensor for relay detection of Cu2+ and S2− in aqueous solution

A simple colorimetric chemosensor 1 was developed for the sequential detection of Cu2+ and S2−. Sensor 1 could rapidly detect Cu2+ by an obvious color change from colorless to yellow. The binding mode of 1 to Cu2+ was determined to be a 1:1 complexation stoichiometry through Job plot and ESI-mass spectrometry analyses. The sensing mechanism of Cu2+ by 1 was proposed by theoretical calculations. Importantly, the detection limit for Cu2+ was found to be 0.12 μM, which was much lower than the recommended value (31.5 μM) of the World Health Organization (WHO). Additionally, 1 could detect and quantify Cu2+ in real water samples. Moreover, the resulting 1-Cu2+ complex could be used as a highly selective colorimetric sensor for S2− in the presence of various anions without any interference. The detection limit for S2− was determined to be 1.66 μM, which was much lower than the guideline (14.8 μM) recommended by WHO in fresh water.

Sequential detection of copper(II) and cyanide by a simple colorimetric chemosensor

A simple colorimetric receptor 1 based on the combination of N-(5-nitro-2-pyridyl)-1,2-ethanediamine and 4-(diethylamino)-2-hydroxybenzaldehyde was synthesized for the sequential detection of Cu2+ and CN−. The receptor 1 showed a distinct color change toward Cu2+ from colorless to yellow. The detection limit of 1 for Cu2+ (0.88μM) was much lower than the World Health Organization guideline (31.5μM) as the maximum allowable copper concentration in drinking water. In addition, 1-Cu2+ complex could be used to detect cyanide by showing a color change from yellow to colorless, indicating the recovery of 1 from 1-Cu2+. Furthermore, the sensing mechanism of 1 for Cu2+ was supported by theoretical calculations.

Simple naked-eye colorimetric chemosensors based on Schiff-base for selective sensing of cyanide and fluoride ions

The present work describes the design and synthesis of simple colorimetric chemosensors based on Schiff-base for highly selective sensing of cyanide and fluoride ions. The chemosensor S2, containing an electron withdrawing group (EWG), displayed selective sensing properties for both cyanide and fluoride ions. The interaction of S2 with F– and CN– ions provides remarkable colorimetric responses from yellow to purple, enabling naked-eye sensing without any spectroscopic instrumentation. The mechanism of anion binding with chemosensor S2 showed one-to-one stoichiometry by Job’s plot. The mechanism of interaction between the S2 and CN– ions has been confirmed by the 1H NMR titration experiments. Furthermore, the detection limits of chemosensor S2 towards F– and CN– ions were found to be 3.7 and 1.2 μmol/L, respectively.

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.

Colorimetric detection of Cu2+ by surface coordination complexes of polyethyleneimine-capped Au nanoparticles

A new simple colorimetric chemosensor for sensitive and selective detection of Cu2+ using polyethyleneimine (PEI)-capped Au nanoparticles (PEI/Au NPs) has been developed. PEI/Au NPs are synthesized by using PEI as reducer without adding nanoparticles seeds and stabilizing agent. Copper ions are captured by the amino groups of the PEI/Au NPs to form an absorbent complex at the surface of PEI/Au NPs, resulting in the color of PEI/Au NPs changing from wine red to purple. Under the optimal conditions, the proposed colorimetric sensor is capable of sensitively and specifically detecting Cu2+ with a detection limit of 0.29μM and a linear range of 25–300μM. This method is simple, fast and highly selective for Cu2+ in the presence of high concentrations of other environmentally relevant metal ions because of the great specific coordination between Cu2+ and PEI, which potentially meets the requirement of the detection in real samples. Moreover, addition of EDTA to PEI/Au NPs-Cu2+ recovers the color offering PEI/Au NPs as a promising reversible sensor for practical application.

Simultaneous Detection of F− and CN− by a Simple Colorimetric Chemosensor with High Selectivity

A julolidine–nitroaniline conjugate as a new simple colorimetric chemosensor 1 for the detection of both F− and CN − has been developed. This sensor could simultaneously detect two biologically important anions (F− and CN −) through colorimetric methods over most other competitive anions. It exhibited a distinct color change from yellow to orange upon addition of F− through deprotonation process. In addition, the sensor 1 displayed an obvious color change from yellow to colorless upon binding with CN − through a nucleophilic addition mechanism. Thus, this sensor exhibits a new method to simultaneously assay F− and CN − with different color change in the same solvent environment.

A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN−

A new simple ‘naked eye’ chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN− in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN− over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye.