Gold-silver alloy nanoparticle formation via spark ablation: the dynamics of material mixing

Binary nanoparticles (BNPs), composed of two distinct materials, offer tailored properties advantageous for various applications, including enhanced catalytic, magnetic, and optical behavior. Among the synthesis methods for BNPs, spark ablation stands out for its capability to produce multicomponent nanostructures with tunable compositions. This study investigates the mixing dynamics of material vapors in spark ablation, a critical step in the process of BNP formation. Using spatially and temporally resolved optical emission spectroscopy (OES), we track the expansion and interaction of gold and silver vapors within the spark gap of a spark discharge generator. The collected data reveal the evolution of the vapor mixing process, complemented by a quantitative model that maps the variation of the gold-to-silver concentration ratio over time and space. We correlate these observations with the composition distribution of synthesized AuAg BNPs, as analyzed by scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectrometry (EDX). Our findings elucidate key factors influencing the compositional variance of BNPs, facilitating the understanding of the role of vapor mixing in achieving well-controlled particle processes via spark ablation.