Multimodal Ion Sensing by Structurally Simple Pyridine-End Oligo p-Phenylenevinylenes for Sustainable Detection of Toxic Industrial Waste

Abstract

Environmental pollution induced by toxic metal ions and harmful chemicals mainly from industrial waste poses a significant threat which urges for their rapid detection before release into the ecosystem above the permissible level. Optical sensors are inexpensive, simple, yet efficient in sensing such toxicants. Herein, we show that structurally simple π-conjugated pyridine-end p-phenylenevinylene oligomers can selectively sense toxic metal ions and anions in solution, supramolecular gels, as well as in solid support. Interaction of Hg2+ at nanomolar concentrations with the linear pyridine-ends via two-site coordination was clearly seen from “naked eye” color changes and fluorometric investigations. The sensitivity as well as selectivity of the oligomers toward Hg2+ was found to be greatly affected by the extent of aromatic conjugation and pK a of the end-pyridine functionalities. Interestingly, one of the oligomers (3) containing an isoniazid moiety renders visual color changes with both Hg2+ and CN– ions through two different binding sites involving two nonidentical sensing pathways which enable this probe for the detection of multiple analytes at the same time. Moreover, these ions (Hg2+/CN–) showed remarkable tuning of the supramolecular assembly (molecular gels) of 3, depicting reversible sol–gel transformation on complementary addition of Hg2+/CN– in proper stoichiometry which could be useful in scavenging toxic ions from industrial wastes. In addition, the low-cost, reusable paper discs coated with the probe molecules show rapid, onsite detection of toxic ions even from the contaminated water samples. Therefore, this highly efficient multimodal sensing of toxic ions by easy-to-synthesize molecular probes could inspire the design of new sensors with varying chromophores for the color-tunable sensing of toxic ions.

Metal-Ion-Responsive Chromogenic Probe for Rapid, On-Location Detection of Foodborne Bacterial Pathogens in Contaminated Food Items

“…Considering this, here, we devised low-cost, reusable paper strips for detection of E. coli (Figure a). , As expected, when the paper strips coated by probe 1 were treated with Cu 2+ , the color of the strips changed from orange to yellow, indicating the binding of the Cu 2+ ion to the carboxylic ends even in the solid state. To ensure the complete saturation of the paper strips with the Cu 2+ ion, the concentration of Cu 2+ in the eluent was varied along with the dipping time.…”

Fluorescent chemosensors based on conjugated polymers with N-heterocyclic moieties: two decades of progress

“…Recently, Bhattacharya and coworkers showed that π-conjugated p-phenylenevinylene oligomers with a pyridine unit as the end group can selectively detect Hg 2+ . 29 Addition of Hg 2+ caused a distinct change in the color of CP-9 solutions from colorless to yellow accompanied by the transformation of the fluorescence from blue to intense yellow. Owing to the interaction of Hg 2+ with the nitrogen-containing pyridine moiety, the polymers can form two-coordination complexes.…”

Recent endeavours in the development of organo chromo-fluorogenic probes towards the targeted detection of the toxic industrial pollutants Cu2+ and CN−: recognition to implementation in sensory device

“…Toxic industrial contaminants such as Cu 2+ and CN − are responsible for inducing pollution and life-threatening ailments owing to their careless release into the environment beyond their permissible limit. 1,2 Therefore, the detection of these water pollutants via molecular recognition is a fascinating and active research area due to the pivotal role exhibited by these ions in biological and industrial processes, pharmaceuticals, and environmental and human sciences. Cu 2+ is an essential d 9 metal ion, playing an indispensable role in various physiological metabolisms.…”