An additive-free electrosynthesis of gold micro-stars for sensitive electroanalysis of N-Acetyl-L-cysteine compared to conventional gold nanoparticles

Gold star (AuST), which is one of the important anisotropic gold structures, finds applications in catalysis, sensing, and photothermal therapy by virtue of its branches of high aspect ratio. The preparation of AuSTs can prove challenging as it requires stringent reaction condition(s) and solution composition including various chemical additives, which are not suitable for either disposal in the environment or use in health-related studies. Furthermore, these chemical additives often cover the gold surface and hence cause interferences in the applications of AuSTs. In this work, we have reported a proof of concept for preparing AuSTs of monodispersed size on glassy carbon electrodes by developing a simple electrosynthesis method using an aqueous acid solution of chloroauric acid in the absence of any chemical additive, structure-directing or surface-protecting agent. This electrosynthesis strategy was developed by understanding the corresponding electrocrystallization mechanism and designing a suitable potentiostatic pulse strategy. The current response per unit area of the gold content for the oxidation of N-Acetyl-L-cysteine was found to be superior on AuSTs compared to widely used citrate-capped gold nanoparticles (cit-AuNPs) and bare gold.