Owing to their plasmonic properties nanoparticles of gold and silver find broad range of applications extending from diagnostics to molecular detection, photothermal and microwave-based therapies, and nanotoxicology. Colloidal silver nanoparticles also find applications in antimicrobial coatings, electronics and photovoltaics, and surface enhanced Raman spectroscopy (SERS) whereas the colloidal gold nanoparticles find applications in lateral flow assays (immunochromatographic assays) and as TEM labels and size standards.
Our gold nanoshells are surface plasmon resonant (SPR) nanoparticles consisting of a nanoscale silica core surrounded by an ultra-thin gold shell. By changing the ratio of the core diameter and the shell thickness the absorption and scattering properties of the nanoshells can be tuned across the visible and near-IR (NIR) regions. For these shells the increase in the size of the silica core, and decrease in the thickness of the gold shell causes the plasmon resonance to shift toward the NIR region. This class of plasmonic nanoparticles has a wide variety of applications, including uses in optical filters, sensing and cancer therapy. To increase the steric stability our gold nanoshells are coated with PVP (40 kD polyvinylpyrrolidone).