Ligand-free and size-controlled synthesis of oxygen vacancy-rich WO3-x quantum dots for efficient room-temperature formaldehyde gas sensing

A facile solvothermal decomposition route was developed for the size-adjustable synthesis of nearly monodispersed, monoclinic-phase WO3-x QDs with sizes ranging from 1.3-4.5 nm. These QDs, with a high concentration of oxygen vacancies, have strong quantum confinement effects and can strongly absorb near-infrared (NIR) light. A solid-liquid-solid growth mechanism was proposed to explain the formation of the QDs. Experiments demonstrated that the rich oxygen vacancies and ultrathin grain size imparted these WO3-x QDs with excellent room-temperature formaldehyde sensing properties.