Noble metal (gold, silver and platinum) nanoparticles are emerging as key optically active nanomaterials for catalysis, plasmonic, sensing, and medical applications. An important property of metallic nanoparticles is their action in response to light irradiation in which collective oscillation of conduction electrons results in the localized surface plasmon resonance (LSPR) property. LSPR property of nanoparticles mainly depends on the size, shape, and surrounding dielectric environment. Controlling the geometry of nanoparticles is a major challenge because this thermodynamically or kinetically driven process strongly depends on the concentration of metal ion precursor, type and concentration of the capping ligand, the nature of the reducing agents, and reaction temperature, which strongly influence nuclei formation and crystallinity character of seeds. Therefore, in order to produce nanoparticles of a specific shape, precise control over the reduction process and an acute understanding of the nucleation and growth steps are extremely important. We present herein, the growth mechanism of gold nanoprisms (GNPs) via a homogeneous nucleation process for the first time. We investigated GNP formation from the reduction of Et<sub>3</sub>PAuCl by poly(methylhydrosiloxane) (PMHS) in the presence of a stabilizing ligand, trioctylamine (TOA). The present study provides the following advantages in investigating the nucleation and growth mechanism of the anisotropic nanostructures over previously reported methodologies; (1) the reaction mixture generates seed particles at the beginning of the reduction process, therefore direct evidence of the nature of the seed particles in the process of GNPs formation is presented. (2) The slow reduction process and step-wise growth of GNPs were analyzed by UV-visible spectroscopy and TEM in a time resolved manner and provided valuable information regarding the nucleation and growth processes at the early stages of GNP formation. We also investigated the role of reducing and stabilizing agents on the overall shape of the nanoparticles.

Homogeneous nucleation-driven formation of gold nanoprisms: A real time spectroscopic and microscopic investigation

255th National Meeting (2018)

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