Photoluminescence in nano tungsten oxide is not preferred at room temperature. But why? It is reported that there is light emission in thin WO3 films at liquid nitrogen temperatures. However, the emission disappears at room temperature. So, the photoluminescence in tungsten oxide is not preferred at room temperature.
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While it is also reported that a strong photoluminescence is found in nanostructured crystalline tungsten oxide thin films at room temperature. Two kinds of films --- P films and W films --- are involved in the investigation. Wherein, P films are referred to as the films composed of nanoparticles and W films are referred to as the films composed of nanowires. Under excitation at 256 nm, P films exhibit strong ultraviolet-visible (UV) emission at 355 nm, and W films show two emission peaks at 355 and 475 nm. In contrast, from bulk phase WO3 powder, no photoluminescence was detected under the same excitation conditions.
