Silver nanoparticles modified two-dimensional polarizative PbTiO3 nanoplates with high active plane and improved NH3 sensitivity at low temperature

Two-dimensional (2D) perovskite PbTiO3 is an important ferroelectric material with spontaneous polarization below Curie temperature and readily adsorbs oxygen molecules in the atmosphere, a preliminary step for NH3 response. However, the surface of 2D PbTiO3 lacks enough active adsorption sites for NH3 gas. Here, 2D PbTiO3 nanoplates (NLs) with highly polarized (001) plane was synthesized by a two-step hydrothermal strategy without templates and surfactants, and Ag+ ions on (001) plane were further in-situ reduced by an impregnation method. Specially, the negatively polarized surface (zeta (zeta potential) =-22.3 mV) for (001) plane promoted the reduction of Ag+ ions in AgNO3 solution to Ag0 nanoparticles (NPs). Where, Ag NPs with high density on (001) plane can produce spillover effect, promoting adsorption of O2 in air and subsequent formation of O2-. The response of PbTiO3-based gas sensor to 100 ppm NH3 is 3.6 at room temperature (25 degrees C), while the response is improved by 2.6 times on 1.5 at% Ag/PbTiO3 NLs with Schottky junctions. Even at 15 degrees C, the response reaches to 6. The ammonia sensor based on Ag/PbTiO3 NFs is verified with high sensitivity, fast response-recovery and distinct selectivity at low operating temperature.