Interface-engineered S-doped ZnS/ZnO carbon nanocomposites with oxygen vacancies for enhanced 4-nitrophenol detection

Abstract

Zinc sulfide (ZnS) is a semiconductor with a tunable bandgap and strong surface interactions, making it a promising candidate for optical and photonic applications. However, its use in electrochemical sensing remains limited due to its poor electron transport and insufficient affinity for redox-active analytes. To address these limitations, S-doped ZnS/ZnO carbon nanocomposite was synthesized via zinc chloride (ZnCl₂) activation of alkali lignin and subsequent hydrothermal sulfidation to enable the electrochemical detection of toxic 4-Nitrophenol (4-NP). During this process, the in-situ formation of ZnS and partial conversion of zinc oxide (ZnO) generated a strong interfacial coupling between ZnS and ZnO, leading to enhanced electron transport, while sulfur incorporation into the carbon framework not only facilitated 4-NP adsorption but also induced oxygen vacancies in ZnO, enhancing active sites and surface energy and ultimately reducing the charge transfer resistance. Owing to these outstanding properties, the sensor exhibited a low limit of detection, excellent selectivity against various interferences, and long-term stability. The practical applicability of S-doped ZnS/ZnO carbon nanocomposite was also evaluated, where it showed reliable detection of 4-NP concentrations in river water samples. Overall, the in-situ formation of S-doped ZnS/ZnO nanocomposites leverages the synergy between ZnS and ZnO nanoparticles, effectively integrates oxygen-vacancy-rich ZnO with a sulfur-doped carbon network, providing valuable insights for designing efficient electrocatalysts for multiple analyte-sensing applications.