Turn-On-Fluorescence Sensor and Solid Sensory Chip for Cyanide Detection

Herein, we report the synthesis of a triazole-ferric complex and evaluate its photophysical response at room temperature upon treatment with various anionic species, including SiO₃^2-, ClO₄^-, ClO₂^-, CN^-, Cl^-, ClO^-, ClO₃^-, SO₄^2-, NO₃^2-, CH₃COO^-, F^-, SCN^-, C₂O₄^2- and CO₃^2-. The probe molecule showed distinguishable absorption band pattern when subjected to KCN solution, showing selective behavior when compared with the other anionic species. Notably, non-emissive probe molecule, upon agitation with KCN solution, triggered a significant fluorescence with the emission signal intensity of 1207 a.u. located at 478 nm, when sample was excited at 356 nm. Fluorescence titration analysis of the sensor with incremental additions of cyanide triggered continuous increase in fluorescence band at 478 nm, saturating at 1 equivalent of KCN solution, indicating an equimolar stoichiometric relationship between the probe and CN⁻. The emission titration analysis was conducted to explore the LOD which was 0.321 × 10^- 7 M. This emissive behavior of the probe was due to interaction of ferric ions with cyanide ions, which were initially coordinated to the triazole Schiff base ligand, resulting in departure of fluorescent moiety whose emission had been quenched by the ferric ion. This chemodosimetric sensation of the toxic cyanide ions in the tested sample might be useful for the sensation and eradications of environmental hazards. The practical applicability of probe for the direct visual detection of the cyanide ions from the solution was explored by fabricating the probe over substituted porous silicon surface and this surface upon 10-15 min incubation with cyanide enriched solution triggered the chromogenic change shifting the solution's color from a deep blackish-yellow to a plain yellow.