Cs0.33WO3 nanoparticles show excellent near-infrared photothermal conversion property. Plasmonic nanomaterials could exhibit special absorption via the excitation of surface plasmon, and the maximum absorption band was highly sensitive to the particle’s size, shape, local environment, and the coupling between near nanoparticles. Furthermore, under optical illumination, they could convert the absorbed photon energy into heat energy in approximately 1 ps and then transfer the heat to the surrounding media in tens of picoseconds. Such an efficient light-to-heat conversion property made them become useful as nanoheaters and therefore gain more and more attention in the past decade. The NIR photothermal conversion property of the resulting Cs0.33WO3 powder after grinding for various times was studied to demonstrate the excellent NIR photothermal conversion property of Cs0.33WO3 nanoparticles.

 

Photothermal therapy is an attractive therapy technique using photosensitizers to generate heat from light absorption and then kill the cancer cells. To avoid the nonspecific heating of healthy cells and allow deeper penetration into tissues, near-infrared (NIR) light is usually utilized. Cs0.33WO3 NIR photothermal conversion property in the aqueous dispersions was examined at a fixed particle concentration of 0.008 wt%. For the samples before grinding and after grinding for 1 and 2 h, 5 wt.% of PEG 6000 was added to avoid the occurrence of precipitation. The blank solution with 5 wt.% of PEG 6000 in deionized water was also investigated for comparison. 

The picture shows the variation of mean hydrodynamic diameter of Cs0.33WO3 powder with grinding time. It was obvious that the mean hydrodynamic diameter of Cs0.33WO3 powder decreased quickly from about 1,310 nm to about 50 nm within 3 h, revealing that the size of Cs0.33WO3 powder could be reduced to nanoscale efficiently by the bead milling process. Inset a indicates the hydrodynamic diameter distributions of Cs0.33WO3 powder after grinding for 1, 2, and 3 h. Inset b shows the photographs for the aqueous dispersions of Cs0.33WO3 powder before and after grinding for 3 h.

 

Hexagonal Cs0.33WO3 nanoparticles with a mean hydrodynamic diameter of about 50 nm can be prepared successfully in an aqueous solution of pH 8 by bead milling. They possessed excellent NIR photothermal conversion property and stability. With decreasing particle size or increasing particle concentration, the NIR photothermal conversion-induced temperature increase is enhanced. Such a nanomaterial not only could be used in the transparent solar heat-shielding filters, but also is useful for the development of NIR-triggered photothermal conversion materials in biomedicine.