Hexagonal platelets of NiCo₂O₄ in the inset image are used to detect ozone at sub-ppb level with high performance.

A novel and promising ozone gas sensor based on α-Ag₂WO₄rod-like structures is obtainedviaa microwave-assisted hydrothermal method. The electrical resistance measurements show a good gas sensor performance of nanorods at an operating temperature of 300 °C, especially a fast response and a short recovery time.

We report herein a detailed study on the influence of microwave-assisted hydrothermal (MAH) treatment time on both long and short range structures around Ti atoms of SrTiO₃ powders. Few studies have been carried out on short-order structural properties as well as the relationship between the local order and the SrTiO₃ photocatalytic properties. We use X-ray diffraction to determine the long-range structure, while the local environment around the Ti atom is probed with X-ray absorption spectroscopy and the vibration frequencies are investigated by Raman spectroscopy. The faster crystallization of SrTiO₃ powders provided by the MAH system resulted in large distortions of Ti–O bond lengths which remain unchanged even for a longer MAH treatment time. Despite the long-range structure being associated with ideal TiO₆ clusters, X-ray absorption spectroscopy measurements identified the presence of undercoordinated TiO₅ clusters. Compared with the reference bulk SrTiO₃, the hierarchical SrTiO₃ cube-like shape showed enhanced photocatalytic activity, which was associated with the presence of these TiO₅ clusters. Field emission scanning electron microscopy (FE-SEM) revealed that the superstructures based on a cube-like shape are formed by an assembly process, becoming well defined as a function of MAH treatment time.