| Gas-sensing and photocatalytic properties of the semiconductor nanomaterials were chosen as the research topics in this papre. As we know, during the preparation of the nanomaterials, there are many problems. For example, the agglomeration of the nanocrystals is difficult to advoid, and the morphology and size are difficult to control. Here we use intercalation method, hydrothermal process and freeze-drying method to prepare MoO3nanoplates, MoO3nanobelts and hierarchical Ag/AgC1nanomaterials, respectively. The factors influencing the synthesis were investigated. The phase compositions, microstructures and their gas-sensing and photocatalytic properties were characterized. Finally, we discussed the formation mechanisms of α-MoO3nnaocrystals and hierarchical Ag/AgCl nanocrystals. The main results obstained are shown as follows:(1) A highly ordered lamellar molybdate-based inorganic/organic hybrid material was prepared through the reaction between n-octylamine (C8H17NH2) and molybdic acid in absolute ethanol under ambient conditions. After calculating molybdate-based inorganic/organic hybrids at55O℃in air, orthorhombic α-MoO3nanoplates were obstained. The α-MoO3nanoplates obatained have a side-length of1-2μm and a thickness of several nanometers. The results of XRD, FT-IR and TG-DTA show that the molybdate-based inorganic/organic hybrid material is a highly ordered lamellar structure with the layer spacing of2.306(1) nm, and that its composition can be described as (C8H17NH3)2MoO4. The alkyl chains in the [MoO6] layers take on a51°tilt angle along the [MoO6] layers. The results of XRD, SEM, TEM, SAED and HR-TEM show that the obtained MoO3sample consists of single crystal nanoplates. The obstained a-MoO3nanoplate have a highly selective sensing performance to ethanol:the sensitivity is as high as58at300℃for800ppm of ethanol vapor, and the response time is less than15s.(2) MoO3nanobelts with a width of about220nm were prepared through a hydrothermal reaction at180℃for12h, using sodium molybdate (Na2MoO4·2H2O) as the raw material in a nitric acid solution (VHNO3:VH2O=1:5). The gas-sensing performance of the MoO3nanobelts obstained was investigated using volatile organic gases as the targets. The results show that the MoO3nanoribbons obtained have a high sensing selectivity to ethanol at300℃:the sensitivity ranged from6.5to144as the ethanol concentration increased from10to500ppm.(3) A novel and simple freeze-drying route was developed to synthesize hierarchical Ag/AgCl photocatalysts, which have small sizes and high dispersibility. The first step was to form porous PVP-Ag+hybrid compounds, which were then transformed to hierarchical AgCl nanocrystals through a liquid-solid precipitation reaction followed by a partially photoreduction to synthesize hierarchical Ag/AgC1nanocrystals. The PVP-Ag+hybrid precursors and their final Ag/AgC1nanocrystals obtained were characterized by XRD, SEM, TG-DSC, FT-IR, XPS and UV-vis DR spectra. The apperent sizes of Ag/AgCl nanocrystals are156±50nm, and the large Ag/AgCl particles are covered with small Ag/AgCl nanocrystals with a size range of33±12nm. The photocatalytic performance of the as-obtained hierarchical Ag/AgCl nanocrystals was investigated by degrading rhodamine B(RhB), methylene blue(MB) and methyl orange(MO) under visible light(λ≥420nm) and sunlight. The photodegradation rates of RhB (-0.97min-1) was～54times higher than that (～0.018min-1) of TiO2(P25) nanocrystals under the same conditions. Through investigating the influencing factors and possible growth mechanisms of the Ag/AgCl nanocrystals, we found that the PVP molecules and the freeze-drying treatment have a key role in the formation of well-dispersed and hierarchical Ag/AgC1nanocrystals. |
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