Study on the Structure and Vibrational Spectra of Functionalized Au Nanoparticles: Theoretical and Experimental Results

Structural and spectral characteristics of functionalized Au nanoparticles have been studied by electron microscopy, vibrational spectroscopy and quantum chemical methods. Gold nanoparticles were synthesized through a microwave induced reaction, starting with a two phase system using 1-dodecanethiol as passivating agent. The nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field (HAADF) detector. The main structures of the nanoparticles were fcc-like and icosahedrons. Density functional theory (DFT) calculations, optimized geometries and vibrational spectra, have been carried out using 6-31G* basis sets and B3LYP functional. The experimental and theoretical infrared spectra of the functionalized Au nanoparticles show the main absorption peaks from 1-dodecanethiol, C-H stretch from CH2 at 2917, 2848 and from CH3 at 2954 and 2872 cm-1, C-H from-CH2 deformation at 1467 and from CH3 at 1376 cm-1. Infrared spectra of octanethiol and gold nanoparticles functionalized with octanethiol were also obtained. These nanostructures can be used in applications such as diagnostics, biosensing, therapeutics, and drug delivery.