Synthesis Of Hierarchical Structure Micro/Nano Oxides And Their Gas Sensing Properties

The controlled synthesis of ZnO and TiO₂ hierarchical nanostructures through liquid-phase chemical route is investigated in this thesis.The synthesis,formation mechanism and properties are investigated in detail.The thesis mainly focuses on the architecture and properties of novel hierarchical structure of nano-oxides,to illustrate the relationship between hierarchical structure of oxides and their gas sensing properties.1.TiO₂ spheres and TiO₂ fibers were prepared by an aqueous system and electrospinning method,respectively.Heterostructural Ag-TiO₂ spheres and fibers were manipulated by in situ reduction and growth.The gas-sensing properties of the materials to vapor were measured.The results indicated that the Ti O₂ fibers thick film sensors exhibit good sensing property than the TiO₂ spheres.Ag nanoparticles greatly enhanced the sensitivity,selectivity and response characteristic of TiO₂ materials to the tested gases.2.Unprecedented hierarchical ZnO flowers assembled by spider web-like nanostructures,which stepwisely constructed from 0D nanoparticles by chemical bath deposition combined with subsequent calcination.The preservation of the araneose flower-like ZnO hierarchical nanostructures mainly depends on the morphology of the precursors determined by the structure of mixed ZnO and BZA.The ZnO sensing film is fabricated by in situ chemical bath deposition and the sensor exhibits ultrahigh response to ethanol vapor with low detection limit（0.1μL/L）,and ultrafast response and recovery characteristics to 100 ppm ethanol（1 and 10 s）.3.The NiO/ZnO hierarchical heterostructure were constructed by hydrothermal deposition method.The sensing film is fabricated by in situ deposition and the sensor exhibits ultrahigh sensitivity and selectivity to NO with low detection limit（0.001μL/L）.The gas selectivity was explained by the catalytic effect of nanosheet NiO and the extension of the electron depletion layer via the formation of p-n junctions.