Assembling tungsten oxide hydrate nanocrystal colloids formed by laser ablation in liquid into fast-response electrochromic films.

High-performance electrochromic films based on tungsten oxide hydrate ([WO2(O2)H2O]·1.66H2O) colloidal nanocrystals with fast switching speed were fabricated by laser ablation in a mixture of water and hydrogen peroxide followed by electrophoretic methods. Through electrophoretic deposition, the nanoparticles in the colloids synthesized by laser ablation aggregated onto the FTO coated glass substrate forming a lager cell with a uniform size of around 200nm, which subsequently self-assembled into a porous tungsten oxide hydrate film. By optimizing the electrophoretic time (800s) and voltage (-0.5V), the mesh-like porous tungsten oxide hydrate film achieved a wide optical modulation of 32% at 632nm, fast coloration and bleaching response speed of 7.8 s and 1.7s respectively due to the synergetic effect of the unique atomic structure of [WO2(O2)H2O]·1.66H2O and porous structure with large surface area that facilitates the ion insertion/extraction. Thus the tungsten oxide hydrate can be a promising electrochromic material for practical applications.

Metallic oxide nanocrystals with near-infrared plasmon resonance for efficient, stable and biocompatible photothermal cancer therapy.

Photothermal therapy is regarded as one of the most promising cancer treatment technologies due to its negligible side effects and fast operation. However, its therapeutic efficacy is still limited by the lack of cost-effective photostable and biocompatible therapeutic agents with efficient light absorption in the biological window. Here, taking MoO2 as an example, we propose oxide nanocrystals (NCs), with both a metallic electronic structure and near-infrared (NIR) plasmon resonance, for efficient, stable and biocompatible photothermal cancer therapy. Monoclinic MoO2 NCs with good crystallinity were fabricated through the combination of laser ablation in liquid and solvothermal synthesis. The as-synthesized NCs showed intensive local surface plasmon resonance (LSPR) absorption at 800-1000 nm, the NIR biological window, due to their metallic electronic structure and oxide dielectric function. This unique NIR LSPR characteristic leads to excellent photothermal performance, i.e., the maximum temperature elevation was found to be up to 37.5 °C with a MoO2 NC concentration of 0.05 mg mL-1 under 808 nm laser irradiation. Moreover, MoO2 solution is highly photostable, as it exhibits stable irradiation-induced temperature elevation of about 14.3 °C even after four temperature elevation cycles. As a photothermal therapy agent against 4T1 cancer cells, MoO2 NCs exhibit not only good biocompatibility, but also excellent tumor inhibition effects. The highest inhibition rate was up to 80.45%, and the average tumor volume was 2.73 times smaller than normal growth 14 days after the treatment. The results prove that MoO2 NCs exhibiting NIR LSPR can act as an effective agent for photothermal cancer therapy with great photostability and biocompatibility.