| In recent years, semiconductor nanomaterials have drawn much attention owing to their unique physical properties in the wide application of optical and electronic devices. Bismuth sulfide (Bi2S3) is a highly anisotropic layered structural semiconductor material with a direct bandgap energy of1.3eV. It was widely applied in thermoelectric cooling technology and optoelectronic converter for its good optical and thermoelectric properties. Bi2S3nanomaterial exhibits some novel optical properties, such as blue-shift of absorption wavelength and fluorescence emission, the nonlinear optical response, and enhancement of the oxidation, reduction ability. The bismuth sulfide nanoparticle and self-assembly system have more excellent optoelectronic and catalytic properties, which have a broad application prospects in the light-emitting materials, nonlinear optical materials, photocatalytic materials. The properties of the nanomaterial have a close relationship with their particle size, morphology. Therefore, people are more and more concerned about the especial nanostructures and nano-scale materials with different morphology to understand the relationship between the structure and properties. The controllable synthesis of nanomaterials morphology is the researching priorities in the preparation of nanomaterials.In this thesis, tubular, rod-shaped, flower-like bismuth sulfide nanostructures were successfully prepared using bismuth nitrate (Bi(NO3)3·5H2O) as bismuth source with different sulfur source(Na2S·9H2O, CH3CSNH2, CS(NH2)2, Na2S2O3·5H2O) as reagents, urea as a mineralizing agent in different solvents by hydrothermal method. The influence of various reaction conditions on the nanomaterials morphology was investigated in detail. The optical properties of the bismuth sulfide nanomaterials were also studied. The major contents can be summarized as follows:First:Bismuth sulfide nanotubes were successfully obtained from NaBiS2precursor by hydrothermal method. Tubular-like Bi2S3nanomaterials were prepared using bismuth nitrate (Bi(NO3)3·5H2O) and sodium sulfide (Na2S·9H2O) as reagents in different polylol solvents. The results show that the morphologies of as-prepared samples are influenced by molar ratio of reactants, the kind of solvent, surfactant, reaction temperature and reaction time and other factors. Investigating the samples prepared in glycerol-water mixed solvent at the different reaction time, we propose the formation of Bi2S3nanotubes may be a solid-solution-solid conversion process. The decomposition, crystallization of NaBiS2precursor is the key for the formation of Bi2S3nanotubes under hydrothermal conditions. The optical properties of the bismuth sulfide nanotubes were also studied. UV-visible-near-infrared absorption spectrum shows that Bi2S3nanomaterials have strong absorption of photo with wavelength short than900nm. The Bi2S3nanomaterials have a stronger fluorescence emission peak at the range of red light excitated by the light wavelength of519nm.Second:The small size of the bismuth sulfide nanorods were synthesized using Bi(NO3)3·5H2O as bismuth source, thioacetamide (CH3CSNH2) as sulfur source by hydrothermal method in the different solvent. The morphology and size of the samples were influenced by the proportion of S and Bi, the kind of solvent, surfactant, reaction temperature and reaction time and other factors. Uniform nanorods can be obtained by controlling reaction conditions. The optical properties of bismuth sulfide nanorods were studied. The growth process of small size Bi2S3nanorods was discussed. The Bi2S3nucleis grow along the c-axis preferentially and the single crystal crystal structure of the one-dimensional nanorods were formed during the hydrothermal reaction.Third:1. The urchin-like bismuth sulfide nanomaterials consisted of the nanorods were synthesized by hydrothermal method using Bi(NO3)3-5H2O as bismuth source, thiourea (CS(NH2)2) as sulfur source in the different solvents. The reaction conditions, such as the proportion of S and Bi, solvent, reaction temperature, time et al have great influence on the morphologies and size. The growth process of the urchin-like bismuth sulfide nanomaterials was investigated. A self-assembly mechanism is proposed for the formation of the nanostruture.2. Uniform bismuth sulfide nanoflowers assembled by nanorods were obtained by hydrothermal method using Bi(NO3)3·5H2O as bismuth source, sodium thiosulfate (Na2S2O3-5H2O) as sulfur source. The morphology and size of the sample were influenced by the ratio of S and Bi, the kind of solvent, reaction temperature and reaction time and other factors. The growth process of Bi2S3nanoflowers may be a solid-solution-solid transformation and self-assembly process.The experiment results show that uniform Bi2S3with different morphologies such as tubular, rod-shaped, urchin-like could be prepared by hydrothermal method. The reaction conditions have a great impact on the morphologies and size of Bi2S3nanomaterials. The morphology of the Bi2S3samples could be controlled by adjusting the hydrothermal reaction conditions. The formtion process and mechanism with different morphologies of Bi2S3nanomaterials were analyzed, which has a certain significance on the synthesis of Bi2S3nanomaterials. The results of optical properties show that Bi2S3nanomaterials may have good application in solar photovoltaic materials and near-infrared fluorescent materials. |
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