Simultaneous ultrasensitive determination of dihydroxybenzene isomers using GC electrodes modified with nitrogen-doped carbon nano-onions

Abstract

Dihydroxybenzenes (DHB) isomers are carcinogenic for humans and harm the environment, which is challenging to trace their lowest possible sensing limit as they coexist in their similar chemical structure and characteristics. This study developed an ultrasensitive and reliable electrochemical scaffold for the individual and sensitive simultaneous determination of DHB isomers. The nitrogen-doped carbon nano-onions (N-CNOs) synthesized in-situ is much less expensive (only 1/80) than the expensive nanodiamond-based process because the synthesis of CNO from nano-diamond requires a high vacuum (10–6 torr) and a high-temperature (1800 °C), whereas the present process requires atmospheric pressure and approximately 1000 °C. The successful self-assembly of N-CNOs on glassy carbon (GC) electrode becomes a single, metal-free, economically, and environmentally benign sensor material for the ultrasensitive and simultaneous determination of DHB isomers. The CNO and N-CNOs were initially synthesized through the in-situ flame-pyrolysis technique possessing a high degree of graphitization, high surface area, excellent surface wettability, and also in high-quantity, adequately characterized using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectral techniques. For the CNO and N-CNOs, the cage-like concentric graphite layers exhibited an intergraphitic layer spacing of 0.34 nm with a diameter range of 30 nm. The novel N-CNO/GC electrode demonstrated approximately 1000-times better electrocatalytic performance and outperformed the Au, Ag, Pd, MOF, conventional carbon allotropes, including their various composites in determining the DHB isomers with the ultrahigh sensitivity and ultralow detection limit. The N-CNO modified electrodes were further exploited in practical applications for assessing the level of DHB isomers in industrial effluents.