Enhanced gas sensing performance based on the fabrication of polycrystalline Ag@TiO₂ core-shell nanowires

This study demonstrates a novel one-dimensional core-shell structure based on the coating of silver nanowires (Ag NWs) with a layer of titanium oxide (TiO₂) nanoparticles. This approach for generating core-shell structures is facile and straightforward, utilizing a sol-gel method followed by the crystallization of TiO₂ using a simple open-air hydrothermal method. The Ag nanowires are ˜10 μm in length and have a diameter of 100 nm, and their TiO₂ polycrystalline shell is 10–15 nm in thickness. These novel structures offer large surface area and high stability, which are qualities that favor gas sensing performance. Gas sensing tests have demonstrated that the generated Ag NWs@TiO₂ core-shell nanocomposites exhibit better sensing properties (response, selectivity, optimized working temperature, minimum concentration, and response and recovery time) when compared to sensors containing pure TiO₂ nanoparticles. The mechanism of sensing enhancement can be attributed to the Schottky barrier that exists at the interface between the Ag NWs and the TiO₂. The Ag core has an excellent conductive property for electronic transfer and further accelerates the oxygen ionization and surface redox reactions. These results may shed light on the design and construction of TiO₂-based nanocomposites for gas sensor applications.