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

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.