Dual activation mode indanedione-based fluorometric probe for CN− sensing: application in bioimaging, fingerprint imaging, and food sample analysis

Abstract

A new 2-(4-(phenanthren-9-yl)benzylidene)-1H-indene-1,3(2H)-dione (PBI) probe was synthesized and meticulously characterized. The PBI probe demonstrated selective and sensitive detection of cyanide (CN⁻) among various anions and was studied in a DMSO medium through absorption, emission, and visual colour changes. The Michael addition reaction of CN⁻ to PBI resulted in fluorescence quenching at 530 nm, disrupting the intramolecular charge transfer process. The CN⁻ detection mechanism was confirmed using UV-visible and fluorescence spectroscopy, NMR, and mass analysis experiments, ensuring the thoroughness of our research. Moreover, the molecular orbital interactions between the probe and CN⁻ were studied using DFT calculations. PBI showed a CN⁻ detection limit of 0.107 μM, which correlates to the WHO-permitted standard of 1.9 μM in drinking water. The binding stoichiometry between the probe and CN⁻ was 1 : 1, and the quenching constant value was found to be 1.64 × 10⁵ M⁻¹ from the Stern–Volmer plot. In addition, we extensively studied the application of the probe for CN⁻ sensing in the nematode worm C. elegans, filter paper, food, and water samples, highlighting the potential applications of our research in bioimaging and food analysis.