Controllable Synthesis And Properties Of Functional Metal Oxides With Micro/Nano Structures

In this dissertation, hydrothermal and precursor route in the presence of various kinds of surfactants were developed to synthesize various functional metal oxides. With the assistance of 0.1M hexadecyl trimethyl ammonium bromide (CTAB), perpendicularly cross-bedded CuO microstructure had been prepared via a precursor-based route. The formation mechanism of this three-dimensional structure was proposed and the gas-sensing properties of the product were researched. Using PEG with different molecular weight as the shape guide, urchin-like copper oxides with core-shell and solid structure were gained by control synthesis. The two products with different morphologies were explored as the electrochemical biosensors and the difference of the performance was analyzed. Using micro-emulsion method, cobalt oxide with three-dimensional structure assembled by nanofilms was synthesized in the water-in-oil system. The details are summarized as follows:1. Cu2(OH)3Br, as the precursor with a bedded structure was prepared by the bihydrolyzation of Cu(CH3COO)2 in 0.1M hexadecyl trimethyl ammonium bromide (CTAB) solution. Taking the advantage of the difference of solubility between Cu(OH)2 and Cu2(OH)3Br, sodium hydroxide was introduced to get the Cu(OH)2 nanorods with perpendicularly cross-bedded structure. Furthermore, using the Cu(OH)2 nanorods with perpendicularly cross-bedded structure as precursor, CuO with almost the same structure was gained by the thermal treatment at 200℃. The gas sensor property investigation showed that the sensitivities to ethanol and acetone of the as-prepared CuO were two times higher than those of CuO particles (about 100 nm in size) in the gas concentration from 50 ppm to 500 ppm. In particular, the linear response to the ethanol could be used as an operating curve to detect the ethanol concentration in this range. The above results of research have been published in the Crystal Growth& Design.2. A one-step PEG-assisted methodology was developed to synthesize urchin-like copper oxide with core-shell and solid structure controlled by the molecular weight of PEG. The experimental results showed that the molecular weight of PEG had deterministic impact on the structure of the final product. When the molecular weight was 20000, it presented a core-shell structure; while the molecular weight was 400, it presented a solid structure. We thought the different structure mainly attributed to the different viscosity and further more different reaction rate and steric hindrance from different chain length. In the research of the electrochemical biosensitivity of the product we found out that the one with core-shell structure exhibited excellent biosensor capability toward H2O2 with a linear response in the concentration ranging from 10μM to 5.55 mM with a response time of less than 5s; while the solid one showed worse linear response toward H2O2 in the concentration ranging from 10μM to 5.55 mM with more deviation in the low concentration. This difference resulted from the different structure as the core-shell structure was better for the transmission of electron than the solid one. The above results of research have been published in the Journal of Physical Chemistry C.3. Using microemulsion as microreactor, in the oil-water system, using kerosene as the oil phase and Span as a surfactant, triethylamine as a cosurfactant, cobalt chloride dissolved in distilled water as aqueous phase, light green cobalt precursor stacked by cross films was synthesized at normal. In the sequent procedures, the precursor was calcined at 400 degrees in the quartz with product maintaining the appearance. As for the surface area and pore size distribution test, the results showed that the surface area was 58m2/g and the pore diameter distribution was narrow, which was concentrated in the 7-8 nm, showing a mesoporous structure.