Thin film-based chemical sensors of Carbon Quantum Dots (CQDs)-Dithizone for the specific detection of Lead ions in water resources

Abstract

Abstract Lead (Pb2+) toxicity is one of the scourges that pose hazardous and severe risks to human health and the environment globally. Lead toxicity issues can be addressed primarily by the detection of Pb. Thus, the requirement for accurate sensors for lead detection in environmental samples is tremendously increasing all over the globe. Fluorescence-based detection of lead in water samples can act as a stepping stone towards achieving goals like point-of-care, portable, and on-site detection. In the present study, a selective fluorometric chemical sensor developed from Dithizone and Carbon Quantum dots (CQDs) embedded in the chitosan polymer thin films is evaluated for Pb2+ detection in various natural water resources. The fluorescent chemical sensors were characterized using FTIR, XPS, XRD, TEM, CLSM, UV, and fluorescence spectroscopy. Pb2+ ions were detected employing a fiber optic spectrophotometer (FOS) paired with a reflectance probe. Two river water samples and household tap water samples were evaluated for the presence of Pb2+ ions and spiking studies were carried out to measure the accuracy of detection. The sensing and analytical results indicate that lead detection with the limit of detection of 18.3 nM was possible in the 0-100 µM range of concentration with a 1-minute response time. The spiking of Pb2+ concentration in the various water resources led to an accurate estimation with a maximum error of 1.4%, indicating an interference-free detection of Pb2+. The estimation of Pb2+ based on Micro-plasma Atomic Emission Spectroscopy -was used as a reference method. The results show that the developed fluorescent thin film chemical sensor-(based on Dithizone-CQDs impregnated chitosan thin films coupled with a fiber optic spectrometer device shows tremendous potential for point-of-care and real-time monitoring of Pb2+ ions in real water samples. Keywords: Water pollution, Lead (Pb2+) ions, Chemical sensor, thin films, , Carbon quantum dots (CQDs), Fiber optic spectrometer