Silica Gels Doped with Gold Nanoparticles: Preparation, Structure and Optical Properties

A novel, one-pot sol-gel preparation scheme leading to reproducible incorporation of 20-40 nm sized gold nanoparticles (AuNPs) in SiO2 gels is developed based on in situ reduction during gelation using chloroauric acid and ascorbic acid. Variation in the preparation conditions affects the chemical composition, optical properties and size distribution of the AuNPs incorporated in the silica gels. Different organic dopants, i.e., oleic acid, acetic acid or dodecanethiol, are applied to modify the final composite material and to control the rate of reduction and growth of the AuNPs in the gels. The synthesized samples are characterized by UV/Vis/NIR spectroscopy, X-ray diffraction, transmission electron microscopy, thermal conductivity measurements and DTA/TG measurements. The optical properties of the obtained composites are explained using Mie theory. The incorporation of AuNPs leads to an increase in the thermal conductivity of the silica gels. The best process method in this contribution is the use of NaOH as a gelation catalyst and oleic acid as an organic modifier, leading to 20 nm AuNPs dispersed in the silica matrix.

Automated summary

A one-pot sol-gel method was developed to incorporate reproducible gold nanoparticles (AuNPs) with sizes of 20-40 nm into SiO2 gels. The AuNPs' chemical composition, optical properties, and size distribution in the gels were affected by variations in the preparation conditions. Organic dopants such as oleic acid, acetic acid, or dodecanethiol were used to modify the composite material and control the reduction and growth rate of the AuNPs in the gels. The synthesized samples were characterized using various methods, including UV/Vis/NIR spectroscopy, X-ray diffraction, transmission electron microscopy, thermal conductivity measurements, and DTA/TG measurements. The incorporation of AuNPs led to an increase in the thermal conductivity of the silica gels. The optimal process involved using NaOH as a gelation catalyst and oleic acid as an organic modifier to disperse 20 nm AuNPs in the silica matrix.