Tailored fluorophore design: Enhancing selectivity for cyanide ion sensing in water and food samples, and innovative device development

A rigid fluorophore unit of Julolidine/coumarin fused with an indolium-conjugated system was built for the immediate and effective recognition of cyanide ions in a 90 % aq. DMSO solution. The probes are capable of displaying better sensitivity/selectivity for the cyanide ion over a wide range of other interfering ions. The probe JI showed an instant colorimetric variation, whereas the modified probe JCI showed both colorimetric and fluorimetric variation with cyanide ion. The observed detection limit values indicated excellent sensitivity of the probe to the cyanide ion. HRMS and 1H NMR studies confirmed that the mechanism of detection of CN- is via the nucleophilic attack on the electron-deficient indolium moiety of the molecule. Moreover, the probes are well proficient in selective recognition of cyanide in various real time applications (test strips, electronic sensor kit, food and water sample analysis).

Spontaneous optical response towards cyanide ion in water by a reactive binding site probe

Indolium derivatives bearing diphenyl amine (R1) and dibenzylamine (R2) linked through benzene was designed, synthesized, characterized and its cyanide recognizing abilities are studied in 100% water. The probes were exhibited dual channel properties i.e. both colorimetric and fluorimetric changes for the effective sensing of cyanide ion. The discrete color variation of probes with cyanide ion makes possible as colorimetric sensor and which was seen easily through naked eye. The recognition of cyanide ion is accomplished via the attachment of cyanide ion at the C atom of indolium CN group through nucleophilic addition. Also, the found detection limits of probes (nM range) were much lower than the WHO limit. Besides, the probes were effectively applied to determine cyanide ion in real water samples and thus was confirmed with HPLC method.

Selective chromogenic detection of cyanide in aqueous solution - Spectral, electrochemical and theoretical studies

A bisimidazole ensemble (R) possessing naphthoquinone as signaling unit is synthesized and characterized using ¹H and ¹³C NMR and LC-MS spectral techniques. Anion sensing behaviour of the receptor has been investigated using electronic and fluorescence spectral techniques. The receptor exhibits a striking colour change from yellow to brown selectively with cyanide in aqueous HEPES buffer-DMSO (1:1 v/v) medium with a detection limit of 1 μM. Job's continuous variation method suggests that the stoichiometry of the interaction is 1:2 (R:CN^-). The binding constant for receptor-cyanide complex was found to be 8.7 × 10² M^-1. The mechanism of detection of cyanide occurs via deprotonation of imidazole N-H protons, which is well supported by electrochemical study. DFT based theoretical calculations shows that the energy gap between HOMO and LUMO decreases from 3.3086 (in R) to 1.7799 eV (in R + CN^-), which is responsible for the red-shift observed in the UV-Vis spectrum of R upon addition of cyanide ions. The present quinone-bisimidazole based receptor shows few advantages over similar bisimidazoles reported elsewhere.

A diquinone–imidazole ensemble for selective colorimetric sensing of cyanide in aqueous medium via anion induced NIR absorption

The receptor selectively and sensitively senses cyanide ions in aqueous solution with a striking colour changeviaanion induced NIR absorption (913 nm).