Microwave-assisted Synthesis of Hexagonal Gold Nanoparticles Reduced by Organosilane (3-Mercaptopropyl)trimethoxysilane

Abstract

A novel synthesis of hexagonal gold nanoparticles (Au NPs) via hydrolyzed organosilane (3-mercaptopropyl)trimethoxysilane (MPTMS) using an ultrafast and environmentally friendly method is presented in this study. For the first time, organosilane MPTMS is used for chemical reduction of auric acid under ultrafast microwave irradiation. To the best of our knowledge, the use of organosilane for the synthesis of Au NPs has not been reported. The entire one-step process is convenient, rapid and cost-effective, as well as eco-friendly under alcohol-free aqueous media. Different characterization methods were carried out to investigate the properties of synthesized gold nanoparticles. transmission electron microscopy and scanning electron microscopy were used to investigate the morphology of as-synthesized Au NPs, while X-ray powder diffraction was applied to obtain the crystalline nature. Nuclear magnetic resonance was used to track the hydrolysis of organosilane MPTMS, which is employed for the first time as a reducing agent for the synthesis of Au NPs. The impact from microwave irradiation time and power, as well as the catalytic property of as-synthesized Au NPs, was investigated via ultraviolet–visible spectroscopy. The as-synthesized products include gold nanohexagon and two-dimensional hexagonal gold nanoplatelets, both of which are single-crystal with (1 1 1) planes as basal surfaces. From UV-vis spectra, it is found that the facile water-based fabrication of hexagonal Au NPs began within seconds of microwave irradiation and the size growth increased with the microwave power and time. Moreover, the efficient reduction of 4-nitrophenol to 4-aminophenol in the presence of as-synthesized Au NPs was observed, exhibiting a remarkable catalytic activity. The present simple, rapid and convenient one-step microwave process possess high scalability and useful for future applications such as catalysis, medical, biological, plasmonic sensors and electronics.