High-yield fabrication of W18O49@TiO2 core–shell nanoparticles: microstructures and optical-thermal properties

In the present study, high-yield W18O49@TiO2 core–shell nanoparticles were prepared by modified plasma arc gas condensation without any catalysts or substrates. All the as-prepared samples were characterized by FEG-SEM, XRD, FEG-STEM, and HAADF analytic techniques. The results of the structural analysis show that the as-prepared nanoparticles presenting a core–shell morphology with an average diameter of 43.5 ± 8.0 nm were composed of non-stoichiometric tungsten oxide (W18O49 phase) as the core (20–40 nm) and rutile-phase TiO2 as the shell with non-uniform thickness (10–20 nm). For the optical properties of the as-prepared W18O49@TiO2 core–shell nanoparticles, Raman spectroscopy and photoluminescence (PL) spectra were used. Compared with pure TiO2 and W18O49 nanocrystals, the experimental results reveal that the defects in the lattice between the core and shell layers induced the board and shifted peaks in Raman spectra. Also, W18O49@TiO2 core–shell nanoparticles exhibited green emission at 483 nm wavelength observed in PL spectrum. Thermal gravimetric analyzer (TGA) results indicate that the TiO2 shell served a stable layer and prevented further oxidation from the atmosphere of the W18O49 core, thereby improving the thermal stability of W18O49 nanoparticles.