Nanostructure Design In A Composite System For Gas-sensing Applications

Gas sensors have very important applications in many areas such as environmental protection, food safety, traffic safety, and even in chemical production. However, there are some issues need to be solved for the conventional gas-sensing materials, such as the high working temperature, the low sensitivity and the bad selectivity. At the moment, the modification of semiconductors with noble metals has attracted significant attention. Meanwhile, as a novel two-dimensional carbon material, graphene and reduced graphene oxide (rGO) are expected to be applied in improving gas-sensing performance.In this work, we reported a facile approach for the synthesis of ZnO-Ag hybrids at room temperature. The introduction of only 1 wt% Ag in ZnO-Ag hybrids leads to the impressive enhancement in gas-sensing properties of ZnO. Notably, the ZnO-Ag hybrids can offer gas response value of 884.7 towards 1000 ppm of ethanol (approximately 12.6 times higher than pure ZnO nanorods). Meanwhile, the hybrids exhibit well selectivity and excellent stability, these outstanding properties make it a potential material for developing an excellent gas-sensing sensor towards ethanol.We prepared the ZnO/rGO composite by a one-step solvothermal method, and then we used the aforementioned approach for the synthesis of ZnO-Ag/rGO ternary composite. The obtained product was characterized by means of Transmission Electron Microscope, Scanning Electron Microscope, X-ray Diffraction, X-ray Photoelectron Spectroscopy, Raman Spectroscopy and Infrared Spectroscopy. It is found that the types of solvents and surfactants, the amount of both graphene oxide and Ag nanoparticles are the critical factors for the ZnO-Ag/rGO ternary composite. Moreover, rGO sheets and Ag also optimize the morphology and gas-sensing properties of this ternary composite.Compared with ZnO and SnO2,α-MoO3 has a low optimum working temperature. MoO3/rGO was synthesized by a facile solvothermal method, and the above-prepared product was calcined at 500℃ for 2 h. The results show that MoO3-GO (wt%) is orthorhombic MoO3 with the morphology of nanobelt, and it show enhanced gas-sensing properties to ethanol. For example, it could detect 10 ppm ethanol at 260℃. Also, the sensitivity of MoO3-GO (wt%) is one order of magnitude higher than that of the pure Mo156O3.