Self-assembly behavior of Phenanthroimidazole and Naphthalene Pendant Photoluminescent Ionic Liquid and its implication towards cascade Detection Hg2+ and I- ions

Abstract

Functional ionic liquids (ILs) have been effectively used as probe materials to detect numerous targets, including heavy metal ions. Yet, their application for real-time, visual detection of trace levels of Hg2+ , a key heavy metal contaminant, remains rare. In this study, we have introduced a fluorescent room temperature ionic liquid trihexyltetradecylphosphonium 2-(naphthalen-1-yl)-1H-phenanthro[9,10-d]imidazolate, (BTNP), and its low-dimensional materials (nBTNP) via a reprecipitation approach and characterized them by various spectroscopic and microscopic techniques. The neat BTNP demonstrated potential as a solvent-free fluorescent ink, performing well as a secure writing medium. The nBTNP system served as a highly selective fluorescent chemosensor for detecting mercury ions (Hg2+), achieving detection and quantification limits in the nanomolar range, which compares favorably with previously reported sensors and reflects the probe's high sensitivity towards Hg2+. Utilizing its strong fluorescence response, the system enabled highly sensitive and selective quantification of Hg2+ ions in environmental soil samples. Moreover, the nBTNP-Hg2+ ensemble serves as a promising probe for I- ions detection through fluorescence-based assays. We have additionally demonstrated low-cost test strips for Hg2+ detection. Overall, the present report outlines a practical, robust strategy for designing ILs-mediated fluorescent probes tailored for environmental monitoring.