Synthesis And Properties Of The Novel Bacterial Cellulose Hybrid Nanofiber

This thesis mainly studies the design, synthesis and characterization of the novel bacterial cellulose (BC) based hybrid nanofiber. The relationship between the nanofiber microstructure and properties was investigated. The preliminary application of the hybrid nanofiber was reported. The main content is described below.1. The mechanical spectrum of BC gels during evaporate were measured by the reed-vibration mechanical spectrum for liquids (RMS-L). The physics parameters about the complex resonance frequency and internal friction dependent temperature or time were measured by RMS-L. From the experimental results, we can conclude that the order water, transition-state water and free water present in BC gels.2. In-situ deposition of Pt nanoparticles on bacterial cellulose fiber (BCF) for a fuel cell application was studied. The Pt/BC under different experimental conditions was characterized by using SEM, TEM, EDS, XRD and TG techniques. TEM images and XRD patterns both lead to the observation of spherical metallic platinum nanoparticles with mean diameter of 3-4 nm well impregnated into the BC fibril. TG curves revealed these Pt/BC composite materials had the high thermal stability. The electrosorption of hydrogen was investigated by CV. It was found that Pt/BCF catalysts have high electrocatalytic activity in the hydrogen oxidation reaction. The single cell performance of Pt/BCF was tested at the temperature of 30℃under non-humidified conditions. Preliminary tests on a single cell indicate that renewable BC is a good prospect to be explored as membrane in fuel cell field.3. Ag nanoparticles with an average diameter of 1.5 nm were well dispersed on BC nanofibers via a simple in situ chemical-reduction between AgNO3 and NaBH4 at relatively low temperature. Our proposed growth mechanism indicates that Ag nanoparticles were homogenously anchored onto BC fibers by coordination with BC-containing hydroxyl groups. The bare BCF and as-prepared Ag/BCF hybrid nanofibers were characterized by a range of analytical techniques including TEM, XRD, and UV-vis. The results reveal that Ag nanoparticles were homogeneously precipitated on the BCF surface. The results indicate that Ag/BCF hybrid nanofibers are promising candidate materials for functional antimicrobial agents.4. Pd-Cu nanoparticles were prepared in BCF by immersing BCF in a mixture solution of PdCl2 and CuCl2 in water and followed reduction of absorbed metallic ion inside of BCF to the metallic Pd-Cu nanoparticles using sodium borohydride. The bare BCF and the composites were characterized by a range of analytical techniques including SEM, TEM, XRD, FTIR and XPS. The results reveal that the Pd-Cu nanoparticles were homogeneously precipitated on the BCF surface. The Pd-Cu/BCF was used as a catalyst for water denitrification, which showed that it has high catalytic activity.5. Large quantities of uniform BC nanofibers coated with TiO2 nanoparticles can be easily prepared by surface hydrolysis with molecular precision, resulting in the formation of uniform and well-defined hybrid nanofiber structures. The mechanism of arraying spherical TiO2 nanoparticles on BC nanofibers and forming well-defined, narrow mesopores are discussed in this paper. The BC/TiO2 hybrid nanofibers were used as photocatalyst for methyl orange degradation under UV irradiation, and they showed higher efficiency than that of commercial photocatalyst P25.6. Nanocrystals of CdS were achieved via a simple hydrothermal reaction between CdCl2 and thiourea at relatively low temperature. The prepared BCF and the CdS/BCF hybrid nanofibers were characterized by TEM, XRD, TGA, UV-vis, and XPS. The results reveal that the CdS nanoparticles were homogeneously deposited on the BCF surface and stabilized via coordination effect. The CdS/BCF hybrid nanofibers demonstrated high-efficiency photocatalysis with 82% methyl orange degradation after 90 min irradiation and good recyclability. The results indicate that the CdS/BCF hybrid nanofibers are promising candidate as robust visible light responsive photocatalysts.