Fiber-optic thin film chemical sensor of 2,4 dinitro-1-chlorobenzene and carbon quantum dots for the point-of-care detection of hydrazine in water samples†

Abstract

The use of hydrazine in various industrial sectors, especially as a synthetic precursor in pharmaceuticals, coating material for water boilers, and rocket propellant, is increasing globally. Hydrazine is known for its severe toxicity to human health and environmental pollution due to its lower biodegradability and bio-accumulative and toxic nature. The hazardous effect of hydrazine on human health and the ecosystem needs to be urgently addressed. The present study demonstrates the development of a thin film chemical sensor based on 2,4 dinitro-1-chlorobenzene (DNCB) and carbon quantum dots (made from phthalic acid and tri-ethylene diamine (TED)) co-immobilized in chitosan-based thin films for the specific detection of hydrazine. A portable fibre optic spectrometer (FOS) coupled with a reflectance probe was used to sense hydrazine molecules in different water resources such as household water supply and two river water samples. The developed chemical sensor thin films were characterized using various techniques such as XRD, FTIR XPS, TEM, UV spectroscopy, CLSM and fluorescence spectroscopy. The sensing results indicated an estimation of hydrazine in a minimal response time of 1 minute, limit of detection (LOD) of 7 ppb and linear range of 0–100 μM. The results also show high specificity and negligible interference against many probable interfering molecules. The spiked concentrations of hydrazine in various real water samples resulted in an accurate prediction near 100% with a minimal error of 1.2%. The photo-stability of the sensor films was found to be about 120 days. The developed sensor was validated against the HPLC method. The study clearly shows the excellent potential of the developed chemical sensors as a point-of-care tool for the real-time and specific detection of hydrazine in various water matrices using a fiber optic device system.