Fluorescent (Au@SiO2)SiC Nanohybrids: Influence of Gold Nanoparticle Diameter and SiC Nanoparticle Surface Density

Gold@silica core–shell nanoparticles were prepared with various gold core diameters (ranging from 20 to 150 nm) and silica thicknesses (ranging from 10 to 30 nm). When the gold diameter is increased, the size dispersion became larger, leading to a broader plasmon band. Then, silicon carbide (SiC) nanoparticles were covalently immobilized onto silica to obtain hybrid (Au@SiO₂) SiC nanoparticles. The absorption properties of these hybrid nanoparticles showed that an excess of SiC nanoparticles in the dispersion can be identified by a strong absorption in the UV region. Compared to SiC reference samples, a blue shift of the fluorescence emission, from 582 to 523 nm, was observed, which was previously attributed to the strong surface modification of SiC when immobilized onto silica. Finally, the influence of several elaboration parameters (gold diameter, silica thickness, SiC concentration) on fluorescence enhancement was investigated. It showed that the highest enhancements were obtained with 10 nm silica thickness, low concentration of SiC nanoparticles, and surprisingly, with a 20-nm gold core diameter. This last result could be attributed to the broad plasmon band of big gold colloids. In this case, SiC emission strongly overlapped gold absorption, leading to possible quenching of SiC fluorescence by energy transfer.