【作者】 杨加志；

【导师】 杨绪杰； 孙东平；

【作者基本信息】 南京理工大学 ， 材料学， 2011， 博士

【摘要】 本文主要研究了细菌纤维素分子作用域大小,在此基础上设计细菌纤维素一维无机纳米杂化纤维。探讨杂化纤维微观结构对其性能影响并开展杂化纤维的应用研究。主要内容如下：1.采用液体簧振动力学谱方法对细菌纤维素凝胶进行挥发过程中实时检测,测量的物理量是衬底和沉积在衬底上面的待测样品组成的复合系统的共振频率(f)与内耗(Q-1)随时间(t)或温度(T)的变化。实验结果表明：细菌纤维素凝胶系统中的水分子在纤维素分子作用下可分为无序水、过渡态水和有序水,并分析出纤维素分子作用域大小。2.通过细菌纤维素分子模板效应,在细菌纤维素纳米纤维表面进行Pt4+原位化学还原反应,制备出燃料电池用Pt/BCF电催化剂。采用SEM、TEM、XRD对Pt/BCF电催化剂的微观结构进行表针。TEM和XRD分析结果表明：3-4 nm Pt纳米晶均匀分散于细菌纤维素纳米纤维表面。循环伏安法测试表明：Pt/BCF催化活性高达34.8 m2/g。由细菌纤维素膜和杂化纤维组装成燃料电池的输出功率达12.1mW/cm2,显示出细菌纤维素膜在燃料电池领域有较大应用潜力。3.通过细菌纤维素分子模板效应,在细菌纤维素纳米纤维表面进行Ag+原位化学还原反应,制备Ag/BCF饮用水高效杀菌剂。采用SEM、TEM、XRD对Ag/BCF杀菌剂的微观结构进行表针。Ag/BCF的TEM照片显示了1.5 nm银纳米晶均匀的附着在细菌纤维素表面。结合XRD和UV-vis等分析结果,探测出纳米银在细菌纤维素表面生长机制。饮用水的微生物去除实验表明：Ag/BCF杂化纤维素可快速实现饮用水的微生物去除。4.通过细菌纤维素分子模板效应,在细菌纤维素纳米纤维表面进行Pd2+和Cu2+原位化学还原反应,制备Pd-Cu/BCF二元化学脱氮催化剂。采用TEM、XRD、XPS和FTIR等测试手段对Pd-Cu/BCF催化剂的微观结构进行表针。Pd-Cu/BCF杂化纤维的化学脱氮实验和循环使用实验结果显示出Pd-Cu/BCF催化剂具有优异的催化活性和使用寿命。5.采用细菌纤维素的分子印迹效应,实现了TiO2纳米晶在细菌纤维素纳米纤维表面的均匀排布。结合微观测试和氮吸脱附实验结果,阐述并初步证实了TiO2纳米晶在纳米纤维表面的生长机制。通过TiO2/BCF和商业化催化剂P25的光催化性能测试,结果表明TiO2/BCF杂化纤维的光催化性能明显优于P25,显示出TiO2/BCF杂化纤维用于光催化降解有机废水的巨大优势。6.利用细菌纤维素分子配位效应,实现CdS纳米晶在细菌纤维素纳米纤维表面的均匀生长。依据CdS/BCF微观分析结果,阐明了CdS纳米晶在纤维表面的生长机制。CdS/BCF杂化纤维的XRD分析结果表明,CdS纳米晶在细菌纤维素分子力诱导下,实现了立方晶型向六方晶型的低温转变。在可见光激发下测试了CdS/BCF、P25和CdS粉末光催化性能,催化反应速率常数分别为0.012min-1、0.0104 min-1和0.00013 min-1。CdS/BCF杂化纤维循环使用测试表明：其循环使用5次后,依然保持较高的催化活性,显示其具有较大的工业应用潜力。更多还原

【Abstract】 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.更多还原