About color of nano-tungsten oxide, in the W-O series, exists WO3, WO2.9, WO2.72, WO2. WO3 (yellow) - WO2.90 (blue) - 2.72 (purple) - WO2 (brown) - W (grey black). Namely, Tungsten has
Tungsten Oxide Nanorods: An Efficient Nanoplatform for Tumor CT Imaging and Photothermal Therapy | Scientific Reports
Frontiers | Recent Advances in Tungsten-Oxide-Based Materials and Their Applications