【作者】 刘鹤；

【导师】 宋湛谦；

【作者基本信息】 中国林业科学研究院 ， 林产化学加工工程， 2011， 博士

【摘要】 纤维素纳米晶体（Cellulose nanocrystals,CNs）是一种新型的生物质基纳米材料,因具有高纯度、高结晶度、高杨氏模量、高强度等特性,加之具有生物材料的轻质、可降解、生物相容及可再生等特性,适于作为高性能复合材料的填充物。纤维素纳米晶体通过对其表面进行化学功能化改性,以及与无机功能化纳米材料复合,被赋予了更多的性能,也使其在众多领域中显现出巨大的应用前景。论文研究了纤维素纳米晶体的制备及其功能化改性,并以制得的纤维素纳米晶体为模板,分别制备了纳米Ag、Ag-Pd合金和Fe₂O₃与纤维素纳米晶体的复合物,对复合物作为高分子材料的多功能填料、DNA电化学生物传感器标记物及水处理吸附材料进行了详细研究。主要创新点如下:采用碱溶胀法对纤维素进行预处理,通过TEMPO/NaClO/NaBr氧化制备了纤维素纳米晶体;以纤维素纳米晶体为模板,制备纤维素纳米晶体与Ag-Pd合金和Fe₂O₃的复合物,并将复合物分别应用于DNA电化学生物传感器标记物及水处理吸附材料。采用硫酸催化水解法,以微晶纤维素（microcrystalline cellulose,MCC）为原料,制备尺寸范围在长100～200 nm,宽10～20 nm的纤维素纳米晶体粒子,纤维素纳米晶体的晶型与原料MCC一致。并用TEMPO/NaClO/NaBr氧化体系对制备的纤维素纳米晶体进行表面羧基化改性,羧基化改性纤维素纳米晶体的晶型同样未发生变化。另外,在非酸体系中,以TEMPO/NaClO/NaBr氧化体系对碱预先溶胀的MCC进行氧化处理,制备了同样形貌及尺寸范围的纤维素纳米晶体粒子。以羧基化改性纤维素纳米晶体（carboxylated cellulose nanocrystals,CCNs）为载体,通过液相化学法制备了CCNs与Ag纳米粒子（Ag nanoparticles,AgNPs）的复合物（CCNs/AgNPs）,并分别与水性聚氨酯（WPU）和聚乙烯醇（PVA）复合制备功能化高分子复合物。分析结果显示WPU/CCNs复合物的玻璃化转变温度和热稳定性随着CCNs添加量的增加而升高,CCNs的添加使得WPU复合膜的拉伸强度出现先升高后降低的趋势,复合物的断裂伸长率降低。与WPU/CCNs复合物不同的是,CCNs的添加使PVA复合物的玻璃化转变温度降低,热稳定性能增强,拉伸强度明显提高。此外,AgNPs的添加使WPU复合物和PVA复合物对大肠杆菌和金黄葡萄球菌表现出良好的抗菌性能。利用纤维素纳米晶体表面的羧基,在乙基-^3-(^3-二甲基氨基丙基)碳二亚胺（EDC）和N-羟基琥珀酰亚胺（NHS）作用下与探针DNA（probe DNA）分子上的-NH2反应生成酰胺键（-CONH-）,使探针DNA与CCNs/AgNPs复合物连接,制备成具有电化学活性的CCNs/AgNPs-probe DNA探针。CCNs/AgNPs-probe DNA探针与目标PAT基因和非互补DNA的电化学检测结果表明,以CCNs/AgNPs作为DNA标记物的电化学生物传感器对PAT基因片段的检测具有很好的选择性,Ag的电化学信号与PAT基因片段浓度在1.0×10^-10 mol/L到1.0×10^-7 mol/L范围内呈良好的线性关系,检测限为2.3×10^-11 mol/L。结果表明,纤维素纳米晶体可用于DNA生物分子固定;CCNs/AgNPs作为DNA电化学生物传感器中探针DNA的标记物,制备的电化学生物传感器可用于PAT基因片段的检测。使用羧基化改性纤维素纳米晶体水分散液作为反应体系,以硼氢化钠为还原剂,采用共还原沉淀法制备了Ag-Pd合金纳米粒子。合金粒子的平均粒径小于AgNPs和钯纳米粒子（Pd nanoparticles,PdNPs）的平均粒径,且随着Ag含量的增加,合金粒子的平均粒径减小。CCNs/Ag-Pd复合物作为标记物与探针DNA结合,经探针DNA与目标DNA发生杂交反应后,可同时产生Ag和Pd的电化学信号,表明CCNs/Ag-Pd复合物可作为标记物用于DNA电化学生物传感器。采用水热法,以纤维素纳米晶体为稳定剂制备了不同形貌的氧化铁纳米粒子。通过TEM、XRD、FT-IR对纤维素纳米晶体与氧化铁纳米粒子（CNs/Fe₂O₃）复合物的形态进行了表征。将制备的CNs/Fe₂O₃复合材料作为吸附材料用于水处理,同时还考察了试剂Fe₂O₃、MCC和纤维素纳米晶体的在水体系中的吸附性能。选取金属阳离子Cd²⁺、Pb²⁺和Ni²⁺,阴离子Cr₂O₇^2-、AsO₄^3-和PO₄^3-作为吸附性能研究对象。结果表明,四种吸附材料对几种离子均有一定的吸附性能。相比于单一的吸附材料,由于纤维素纳米晶体和Fe₂O₃各自吸附性能的协同效应,CNs/Fe₂O₃复合物对于几种离子Pb²⁺、Cd²⁺、Ni²⁺、Cr₂O₇^2-、AsO₄^3-和PO₄^3-均具有很好的吸附性能。更多还原

【Abstract】 Cellelose nanocrystals （CNs） is a kind of new biomass nanomaterilas, which is suit for the application in polymer composites as nanofiller due to its high purity, high crystallite, high Young Modulus and mechanical strength. In addition, CNs also has properties belonging to biomaterials, such as low density, biodegradable, biocompatible and renewable. The chemical modification of CNs and the prepation of hybrid material with CNs and inorganic functional nanomaterials would give more special properties and make CNs show broad applications in many fields.The preparation and chemical modification of cellulose nanocrystals （CNs） were investigated in this paper. Furthermore, the CNs were used as templates to synthesize silver nanoparticles （AgNPs）, Ag-Pd alloy and Fe₂O₃, respectively. The applications of CNs/AgNPs, CNs/Ag-Pd and CNs/Fe₂O₃ composites used as multifunctional fillers for polymers, labels for DNA electrochemical sensor and adsorbing materials for water treatment were investigated. The innovations of this paper are synthesis of CNs by TEMPO/NaClO/NaBr oxidation of alkali treated cellulose; synthesis of CNs/Ag-Pd and CNs/Fe₂O₃ composites materials; applications of the composites as labels of novle electrochemical DNA biosensor and water treatment materials.CNs with size about 100-200 nm in length and 10-20 nm in width was prepared from MCC as raw material by H2SO4 hydrolysis. XRD results show that CNs and MCC are the same crystal phase. Carboxylated cellulose nanocrystals （CCNs） was synthesized from CNs by surface chemical modifications using the TEMPO/NaClO/NaBr （TEMPO, 2,2,6,6-tetramethylpiperidine-1-oxyl radical） oxidation system. The crystal phase of CCNs was the same as the MCC. Furthemore, CNs was prepared from NaOH treated MCC using TEMPO/NaClO/NaBr oxidation system without acid. Morphology of this kind of CNs was the same as the CNs synthesized by H2SO4 hydrolysis.Nanocomposites composed of CCNs and silver nanoparticles （AgNPs） were prepared by liquid phase chemical methods and used as bi-functional nanofillers to blend with waterborne polyurethane （WPU） and polyving akohol （PVA）. The characterizations indicated that glass transition temperatures （Tg） and thermal stability of WPU-based composites increased with increasing CCNs content. Tensile strength of WPU-based films increased significantly with filling, but tensile strength decreased with further addition of CCNs. The elongation at break decreased obviously with increasing CCNs content. In contrast with WPU composites, glass transition temperatures （Tg） of PVA composites decreased and thermal stability increased with increasing CCNs content. Tensile strength of PVA-based films increased significantly with filling CCNs. More importantly, WPU/CCNs/AgNPs and PVA/CCNs/AgNPs composite films showed strong antibacterial activities against E. coli and S. aureus.Grafting of the probe DNA onto the CCNs was carried out via carboxyl groups covalently coupled with the -NH2 moiety of the probe sequence by amide linkage （-CONH-） in the presence of EDC and NHS to prepare CCNs/AgNPs-probe DNA probe. The electrochemistry response of target PAT DNA, noncomplementary sequence and blank measurement illustrated that DNA biosensor with CCNs/AgNPs as the probe DNA label had good selectivity for the PAT gene fragment detection. Signal of silver had a linear relationship with the logarithmic value of the PAT gene fragment concentration ranging from 1.0×10^-10 mol/L to 1.0×10^-7 mol/L and the detection limit was 2.3×10^-11 mol/L. These results indicated that CCNs could be used for immobilization of DNA biomolecular and the CCNs/AgNPs nanocomposites could be used as labels of target DNA for electrical detection of PAT gene fragment.Synthesis of Ag-Pd alloy nanopaticles was carried out with CCNs suspension as reaction system by co-reducing metallic cations using NaBH4. Alloy particles with a size less than monometallic AgNPs and PdNPs were readily prepared and dispersed well. The average size of alloy nanoparticles decreased as the increasing molar ratio of Ag/Pd. After hybridization between target DNA and probe DNA, two signals belong to the Ag and Pd could be detected when the CCNs/Ag-Pd nanocomposites as probe DNA labels. The CCNs/Ag-Pd nanocomposites can be used as labels in DNA electrochemical sensor.Iron oxide nanoparticles with different morphologies were synthesized by hydrothermal reaction in the presence of CNs as stabilizing agent. The composites composed of iron oxide and cellulose were characterised by TEM, XRD and FT-IR. The adsorptive capacities of MCC, CNs, Fe₂O₃ and CNs/Fe₂O₃ composite to Cd²⁺, Pb²⁺, Ni²⁺, Cr₂O₇^2-, AsO₄^3- and PO₄^3- were investigated. Comparing with the monocomponet materials, CNs/Fe₂O₃ composite show better adsorptive capacities to the anions and cations.更多还原