Optimized Ammonia-Sensing Electrode with CeO2/rGO Nano-Composite Coating Synthesized by Focused Laser Ablation in Liquid

Abstract

This study investigated the synthesis of cerium oxide (CeO2) nanoparticles (NPs) and composites with reduced graphene oxide (rGO) for the enhanced electrochemical sensing of ammonia. CeO2 NPs were prepared by the focused laser ablation in liquid (LAL) method, which enabled the production of high-purity, spherical nanoparticles with a uniform dispersion and sizes under 50 nm in a short time. The effects of varying irradiation fluence and time on the nanoparticle size, production yield, and dispersion were systematically studied. The synthesized CeO2 NPs were doped with rGO to form CeO2/rGO composites, which were drop casted to modify the glassy carbon electrodes (GCE). The CeO2/rGO-GCE electrodes exhibited superior electrochemical properties compared with single-component electrodes, which demonstrated the significant potential for ammonia detection, especially at a 4 J/cm2 fluence. The CeO2/rGO composites showed uniformly dispersed CeO2 NPs between the rGO sheets, which enhanced the conductivity, as confirmed by SEM, EDS mapping, and XRD analysis. Cyclic voltammetry data demonstrated superior electrochemical activity of the CeO2/rGO composite electrodes, with the 2rGO/1CeO2 ratio showing the highest current response and sensitivity. The CV response to varying ammonia concentrations exhibited a linear relationship, indicating the electrode’s capability for accurate quantification. These findings highlight the effectiveness of focused laser ablation in enhancing nanoparticle synthesis and the promising synergistic effects of CeO2 and rGO in developing high-performance electrochemical sensors.