Photogeneration of silver nanoparticles induced by UV radiation and their use as a sensor for the determination of chloride in fuel ethanol using a flow-batch system

Abstract

Photogeneration of silver chloride nanoparticles (AgCl-NPs) in fuel ethanol was used as a sensor for the spectrophotometric determination of chloride. A low-power UV radiation source (germicidal lamp) was placed close to a flow-batch chamber and a 3D-built support for the reaction chamber was used to couple fiber optic cables in the orthogonal direction with the UV-lamp beam, allowing the monitoring of nanoparticle formation in real-time using a spectrophotometer. The nanoparticles were characterized via high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and UV–vis spectroscopy. Most of the particles exhibited a spherical shape with an average diameter of 18 nm. The absorbance maximum was observed at 440 nm and was used for chloride determination in fuel ethanol. Under the optimized working conditions, the system exhibited a linear response from 0.05 to 0.8 mg L−1 chloride, with a limit of detection (95%) and coefficient of variation (n = 8) were estimated to be 12 μg L−1 chloride and 2.2%, respectively. The intra- and inter-day precisions (coefficient of variation) were 2.4% and 2.8%, respectively. This working range (0.05–0.8 mg L−1) for the determination of chloride at low concentrations met the limit required by Brazilian legislation (limit of 1.0 mg kg−1). Analyses of fuel ethanol were performed without sample treatment and the obtained results were compared with those obtained by ion-chromatography. No significant differences were observed between the two methods at the 95% confidence level.