Loading uniform Ag 3 PO 4 nanoparticles on three-dimensional peony-like WO 3 for good stability and excellent selectivity towards NH 3 at room temperature

A heterojunction structure design is a very good method for improving the properties of semiconductors in many research fields. This method is employed in the present study to promote the gas-sensing performance of Ag 3 PO 4 nanocomposites at room temperature (25 °C). A nanocomposite of Ag 3 PO 4 nanoparticles and three-dimensional peony-like WO 3 (WO 3 /Ag 3 PO 4 ) was successfully prepared by the precipitation method. The crystalline phases were analyzed by x-ray diffraction and the microstructure was characterized by scanning electron microscopy and transmission electron microscopy. The chemical bonding states were analyzed by x-ray photoelectron spectroscopy. The gas-sensing performance of WO 3 /Ag 3 PO 4 sensors was systematically explored at room temperature. The composite sensors possessed a higher response and lower detection limit (1 ppm) to NH 3 than those made of a single type of material; this is ascribed to the synergistic effect achieved by the heterojunction structure. Among the different composite sensors tested, gas sensor A5W5 (Ag 3 PO 4 :WO 3 mass ratio of 5:5) displayed the highest response to NH 3 at room temperature. Interestingly, the A5W5 gas sensor exhibited relatively good stability and excellent selectivity to NH 3 . The A5W5 sensor also displayed a relatively good response under high humidity. The gas-sensing mechanism of the WO 3 /Ag 3 PO 4 sensors is explained in detail. Taken together, the as-prepared sensor is highly efficient at detecting NH 3 and could be suitable for practical applications. In addition, this study also provides a new method for developing Ag 3 PO 4 -based sensors in the gas-sensing field.