Electrochemical Deposition of Silver Nanoparticle Assemblies on Carbon Ultramicroelectrode Arrays

Silver nanoparticle (AgNP) assemblies combined with electrode surfaces have a myriad of applications in electrochemical energy storage and conversion devices, (bio)sensor development, and electrocatalysis. Among various nanoparticle synthesis methods, electrochemical deposition is advantageous due to its ability to control experimental parameters, enabling the formation of low-nanoscale (<50 nm) particles with narrow size distributions. Herein, we report the electrodeposition of AgNPs on a unique electrode platform based on carbon ultramicroelectrode arrays (CUAs), exploring several experimental variables including potential, time, and silver ion concentration. Extensive scanning electron microscopy analysis revealed that more reductive deposition potentials resulted in higher counts of smaller-sized AgNPs. While previous studies have employed planar, macro-sized electrodes with millimolar silver ion concentrations and minute-long times for AgNP electrodeposition, our results demonstrate that lower Ag⁺ concentrations (50-100 μM) and shorter deposition times (15-30 s) are sufficient for successful AgNP formation on CUAs. These findings are attributed to enhanced mass transfer from the radial diffusion of the array-based CUAs. The quantity of deposited Ag was determined to be 1100±200 nmol cm^-2, consistent with AgNP-modified CUA electrocatalytic activity for hydrogen peroxide reduction. This study emphasizes the importance of carefully considering AgNP electrodeposition parameters on unconventional electrode surfaces.