Halloysite nanotube composites covered by silver nanoparticles with the average diameters of 5 nm and 9 nm have been studied by methods of optical spectroscopy of reflectance/transmittance and Raman...

Halloysite nanotubes (HNTs) with immobilized gold (Au) and silver (Ag) nanoparticles (NPs) belong to a class of nanocomposite materials whose physical properties and applications depend on the geometry of arrangements of the plasmonic nanoparticles on HNT’ surfaces. We explore HNTs:(Au, Ag)-NPs as potential nano-templates for surface-enhanced Raman scattering (SERS). The structure and plasmonic properties of nanocomposites based on HNTs and Au- and Ag-NPs are studied by means of the transmission electron microscopy and optical spectroscopy. The optical extinction spectra of aqueous suspensions of HNTs:(Au, Ag)-NPs and spatial distributions of the electric fields are simulated, and the simulation results demonstrate the corresponding localized plasmonic resonances and numerous “hot spots” of the electric field nearby those NPs. In vitro experiments reveal an enhancement of the protein SERS in fibroblast cells with added HNTs:Ag-NPs. The observed optical properties and SERS activity of the nanocomposites based on HNTs and plasmonic NPs are promising for their applications in biosensorics and biophotonics.

The optical properties of nanocomposite particles consisting of silicon cores about 100 nm in size with smaller gold nanoparticles deposited on their surface have been studied. An increase in the absorption of light in the nearinfrared region of the spectrum for the obtained nanoparticles is observed in comparison with that for nanoparticles of pure silicon or gold. Experiments on measuring the temperature of aqueous suspensions showed significantly higher rates of photoheating of nanocomposite particles upon irradiation with laser radiation at a wavelength of 810 nm compared to the case of pure silicon nanoparticles. Calculations of the distribution of the electric field showed multiple increases in its strength near nanocomposite particles upon irradiation with light in the visible and near-infrared ranges and also made it possible to find the scattering and absorption contributions to the extinction spectra of nanoparticle suspensions. The observed enhanced photoheating of nanocomposite particles can be used for application in antibacterial treatment and cancer hyperthermia.