This invention details a method for the preparation of spherical, monodisperse SnO2 nanoparticles and more importantly doped tin oxide to give spherical, monodisperse antimony-tin oxide (ATO) and zinctin oxide (ZTO) nanoparticles. The band gap of these tin oxide nanoparticles can be successfully tuned upon antimony- and zinc-doping. These nanoparticles can be very effective in making well controlled systems for photocatalysis, solar cells, optoelectronics, multi-layered devices and treatment of air and water pollutants. Separate discoveries detail unprecedented core-shell nanoparticles (specifically gold nanoparticles (AuNPs) and gold-silver nanoshell (GS-NSs) particles) coated with a doped semiconductor shell (specifically antimony-doped or zinc-doped tin oxide shells (Au@ATO, Au@ZTO, GS-NS@ATO, and GS-NS@ZTO) but envisions other dopants as well (e.g., indium to give indium tin oxide, ITO, shells), as well as the bare SnO2-coated analogs (AuNP@SnO2 and GS-NS@SnO2). The generated plasmonic nanoparticles exhibit a strong optical extinction in the visible region for the AuNP-based particles and in the visible to near-IR region for the GS-NS-based particles. These latter nanoparticles can be used to enhance photocatalytic activity by preventing electron-hole recombination and via their localized surface plasmon resonance (LSPR) to induce charge transfer to photocatalysts in, for example, watersplitting/hydrogen generation and CO2 conversion to fuels. The SnO2-based nanomaterials were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Separately, their optical properties were evaluated by UV-vis spectroscopy, diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy (PL).