Cation-Exchange Synthesis of Cu₂Se Nanobelts and Thermal Conversion to Porous CuO Nanobelts with Highly Selective Sensing toward H₂S

Cu2Se nanobelts have been developed via a facile cation-exchange approach at room temperature, employing ZnSe·0.5N2H4 hybrid nanobelts as the templated precursors. Detailed characterizations demonstrate that the morphologies of the templated precursors are well-preserved in the cation-exchange reaction, because of the spatial confinement effect from the coated layer of poly(vinylpyrrolidone) (PVP) surfactant. Simultaneously, Cu2+ cations diffusing through the coated layer of PVP are in situ reduced to be Cu+ cations by the ligands of N2H4, thereby forming Cu2Se nanobelts with the complete replacement of Zn2+ cations in the templated precursors. After thermal oxidation in air, the obtained Cu2Se nanobelts are further converted into porous CuO nanobelts. Considering that this special morphology processes a large active surface area and is favorable for gas diffusion, gas-sensing properties of porous CuO nanobelts have been explored. The results indicate that porous CuO nanobelts exhibit highly selective sensing toward H2S with a low detection limit less than 10 ppb. Moreover, they also present a good sensing reproducibility. Finally, their sensing mechanism toward H2S has been discussed.