The self-assembly synthesis of tungsten oxide quantum dots with enhanced optical properties

In the present paper, a one-pot microwave-assisted approach was explored for self-assembly fabrication of ultrafine tungsten oxide (WO3) quantum dots (QDs). The as-obtained WO3 QDs were ultrafine, with a quantum size ranging from 2 to 3 nm. Such ultrafine WO3 QDs exhibited significant thermal/photonic stabilities, which are favorable for blue photoluminescence emission and photochromism properties. The WO3 QDs could be well maintained in ethylene glycol at 120 degrees C for 4 days, without the occurrence of aggregation phenomena. It took about 10 s for the colorless aqueous suspension of WO3 QDs to turn blue under solar-light irradiation. A negligible decrease rate (2.7%) was observed for the relative luminescence emission intensity of WO3 QDs after being irradiated by UV light (365 nm) for 24 hours. Such greatly enhanced photochromism was attributed to both the exposed reactive sites and surface oxygen vacancies of ultrafine WO3 QDs.