Ricardo Baez-Cruz^{1, 2,}, Erik Beristain-Montiel^3,

Using soft acids as reducing agents in synthesizing metallic nanoparticles have constituted a clear framework for achieving selected morphological properties with minimal toxicity. The system's complexity and the many variables involved represent a challenge for experimental studies desiring to design reproducible synthesis protocols. In this work, we explore the exclusion of any stabilizing agent to synthesize, in an aqueous solution, non-spherical gold nanoparticles (AuNPs) via Microwave-assisted synthesis, and instead, we employed pH control over reducing agent L-Ascorbic acid (AH₂). The use of AH₂ presents a direct approach that allows an understanding of the role of soft acids in synthesizing metallic nanoparticles. The results indicate that AuNPs synthesized at pH ≥ 10 exhibit relatively different morphologies than those obtained at higher pH values. The AuNPs were characterized via Transmission electron Microscopy and UV-Vis Spectroscopy. Our simulations reveal the plasmon distribution according to particle shape. The experimental analysis suggests that the pH variation mechanism over the reduction agent correlates with AuNPs geometry. These results indicate that pH is an applicable parameter for controlling the nanoparticle's geometry and extend the possibility of exploring computational studies on the impact of acids adsorbed on gold colloidal surfaces.

gold nanoparticles, wet-synthesis, L-Ascorbic acid, TEM, BEM