Optimizing gold nanoparticles for thin film formation: insights into synthesis and surface functionalization with APTES

This study explores the synthesis of gold nanoparticles (AuNPs) using two different methods and the subsequent use of 3-aminopropyltriethoxysilane (APTES) aiming the formation of thin films on FTO glass substrates. AuNPs synthesized using citrate displayed a larger average diameter (14.9 ± 0.1 nm) and higher polydispersity compared to those synthesized with sodium borohydride and PVA (5.3 ± 0.1 nm). UV-Vis spectroscopy, TEM, DLS, and zeta potential analyses confirmed that nanoparticles synthesized with sodium borohydride and PVA were more stable and uniform, demonstrating the efficacy of PVA as a stabilizing agent. The formation of AuNP thin films was optimized by functionalizing the FTO surface with APTES. Electrochemical impedance spectroscopy (EIS) indicated that 1 % and 120 min for immersion time in APTES significantly enhanced the adhesion and uniformity of the films. The methodology employing sodium borohydride and PVA in a hydroxylation surface proved to be more efficient to produce stable thin films, showing larger impedance reduction and better long-term stability. These observations indicate that the method under investigation may offer a promising avenue for biosensors and optoelectronic devices, given its cost-effectiveness and straightforward implementation.