【作者】 刘博；

【导师】 孙润仓； 王小英；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2012， 博士

【摘要】 纳米银溶胶颗粒（Ag NP）是目前使用最广泛的纳米产品原料之一，其最常用的制备方法是化学还原法，然而所用的化学稳定剂与还原剂在一定程度上对人体或环境都有危害，且其难以与Ag NP彻底分离，这限制了Ag NP在医学及生物催化等领域的应用。因此，寻找绿色还原剂及稳定剂，开发简单、高效的Ag NP制备方法是纳米金属工业急需解决的问题之一。天然高分子壳聚糖是具有多羟基的大分子，由于分子间和分子内氢键的作用形成了分子水平上的独立空间，为纳米粒子的成长提供了良好的模板。蒙脱土等层状硅酸盐因层状空间的限域效应素有二维“纳米反应器”之称，被认为是纳米颗粒理想的稳定载体。壳聚糖基层状硅酸盐（CLS）纳米复合材料是壳聚糖或其衍生物在外力驱动下插层进入层状硅酸盐的层间而获得的结合了壳聚糖和无机硅酸盐优异性能的杂化材料。目前关于CLS纳米复合材料的研究甚多，但还未见关于以其为载体制备金属纳米颗粒的报道。本文采用高效快速的微波辐射法制备了壳聚糖衍生物和有机层状硅酸盐、CLS纳米复合材料和剥离型的含纳米银CLS纳米复合材料；并探讨了插层机制、抗菌机理及多功能化的应用。本文主要研究内容及结论如下：1.水溶性壳聚糖衍生物的微波辐射法快速制备及其性能研究（1）快速制备不同取代度的壳聚糖衍生物微波辐射条件下，在水相中快速制备壳聚糖水溶性衍生物——壳聚糖季铵盐（QCS）、羧甲基壳聚糖季铵盐（QCMC）和羧甲基壳低聚糖季铵盐（QCMCO）。微波辐射法可以在短时间内快速得到与传统加热法结构一致且取代度更高的QCS。通过改变微波时间、功率和改性剂用量，可以控制QCMC中羧甲基和季铵基的取代度，在最适宜条件下，羧甲基取代度（DSCM）和季铵基取代度（DSQ）最高分别为82%和48%。（2）壳聚糖衍生物的性能研究制备的QCS有诱导CaCO3悬浊液絮凝的能力，其絮凝行为与取代度成正比，与分子量成反比，QCS的最佳絮凝浓度为6mg/L。QCMCO具有良好的抗氧化性，且与其浓度成正比，与DSCM和DSQ密切相关，当其浓度仅为5mg/mL时，·OH的清除率最高可达到63.6%，Fe²⁺螯合能力最高为81.98%。2.微波辐射法快速制备有机蒙脱土并研究其吸附性能在微波辐射条件下，利用新型双链阳离子表面活性剂烷基Gemini和酯基季铵盐作为改性剂快速地制备大层间距的Gemini-蒙脱土（GMMT）和酯基蒙脱土（EMMT）。Gemini和酯基季铵盐的饱和插层量分别为0.5CEC和0.8CEC，有机蒙脱土GMMT和EMMT的最大层间距分别为2.31nm和2.41nm。此外，微波辐射法得到的GMMT层间距（2.31nm）大于传统加热法得到GMMT（2.23nm）。Gemini与MMT之间以静电作用连接，通过插层、插层-吸附和吸附等三种方式结合；然而，即使酯基季铵盐插层饱和，其依然可以通过吸附的方式与MMT结合，同时EMMT的层间距保持不变。GMMT和EMMT的表面均为疏水性、结构粗糙蓬松，因此两者均有卓越的吸附能力。GMMT对甲基橙的吸附随Gemini分子链长的增加而增强，最高实际吸附量为48mg/g；EMMT对TCS的吸附遵循Langmuir吸附等温模型，最高理论吸附量达133mg/g。3.分子参数对CLS纳米复合材料结构与性能的影响研究（1）壳聚糖衍生物含量对插层过程的影响DSCM和DSQ分别为56.3%和74.6%、分子量为2.9×105的QCMC与OMMT插层复合时，羧甲基壳聚糖季铵盐/有机蒙脱土（QCOM）纳米复合材料的层间距与QCMC的含量成正比。DSCM和DSQ分别为88%和75%、分子量为2×104的QCMCO与有机累托石（OREC）插层复合时，羧甲基壳低聚糖季铵盐/有机累托石（QCOOR）纳米复合材料的层间距随着QCMCO的含量的增加而呈先升后降的趋势。（2）取代度对插层过程的影响由分子量为2.6×105³.0×105的QCMC获得的QCOM纳米复合材料中，高的DSQ可以促进插层反应的进行，增加QCOM纳米复合材料的层间距：当DSCM约为30%，DSQ从29.6%增加到73.9%时，QCOM纳米复合材料的层间距从3.70nm增加到4.50nm。但是，QCOM纳米复合材料的层间距随着DSCM的增加而先升后降：当DSQ约为30%，DSCM从30.4%增加到85.2%时，QCOM纳米复合材料的层间距从3.70nm增加到4.22nm再降到3.79nm。由分子量为8×103².0×104的QCMCO获得的QCOOR纳米复合材料中，增加DSCM有利于插层反应的进行，可以得到更大层间距的纳米复合材料。当DSQ约为45%，DSCM从23%增加到91%时，QCOOR纳米复合材料的层间距从4.37nm增加到4.78nm；但是DSQ对QCOOR纳米复合材料层间距影响较小。（3）剥离型CLS纳米复合材料的制备对于分子量为2.6×105³.0×105的QCMC，当DSCM和DSQ分别为53.6%和41.3%，且QCMC与OMMT质量比为8:1时，可以得到剥离型的QCOM纳米复合材料；对于分子量为8×103².0×104的QCMCO，当DSCM和DSQ分别为88%和75%时，且QCMCO与OREC质量比为4:1，可以得到剥离型的QCOOR纳米复合材料；分子量为8.28×104、DSCM和DSQ分别为72%和80%的QCMC，在与REC的质量比不小于4:1时，可以得到剥离型的羧甲基壳聚糖季铵盐/累托石（QCR）纳米复合材料。4. CLS纳米复合材料的性能研究（1）CLS纳米复合材料的絮凝行为壳聚糖季铵盐/有机蒙脱土（QOM）纳米复合材料耦合了QCS和OMMT的优异性能，具有良好的絮凝性，在用量仅仅为0.005mg/L时，QOM纳米复合材料对CaCO3悬浮液的絮凝效率大于70%，仅是阳离子淀粉等传统絮凝剂用量的千分之一。（2）CLS纳米复合交联微球的控释行为羧甲基壳聚糖季铵盐/有机蒙脱土（QCOM）纳米复合材料与海藻酸钠交联微球（AQCOM）的溶胀行为和控释行为受OMMT影响显著。随着QCOM纳米复合材料中QCMC与OMMT的质量比从1:1增加到8:1，交联微球的溶胀率从44%增加到197%；增加QCMC的含量和QCOM纳米复合材料的层间距有助于提高AQCOM交联微球的包封率；适量OMMT对于药物控释有积极的效果，但是当OMMT的含量过高时，会降低交联微球的控释能力。此外，豚鼠的主动皮肤过敏实验表明，AQCOM交联微球不会引起过敏反应，是一种安全的药物载体。（3）CLS纳米复合材料的抗菌性能与QCMCO相比，与累托石（REC）插层复合后的羧甲基壳低聚糖季铵盐/累托石（QCOR）纳米复合材料的抗菌性提高。经过QCOR纳米复合材料处理过后的革兰氏阳性菌和革兰氏阴性菌的细菌表面出现塌陷和变形、细菌细胞壁破裂有细胞内容物渗出，而真菌的孢子破裂，正常生理活动受到抑制。此外，QCOR纳米复合材料对革兰氏阳性菌的抑制效果优于革兰氏阴性菌和真菌。5.载银的CLS纳米复合材料的结构组装与抗菌机理研究（1）用Tollens试剂法制备壳聚糖基纳米银复合材料利用羧甲基和季铵基的还原能力，在微波辐射条件下快速地获得粒径均一、单分散的球形Ag NP，升高反应温度或延长反应时间均有利于Ag NP的生成。羧甲基壳聚糖（CMC）、QCS和QCMC制备Ag NP的活化能分别为69.7、62.8和103.7kJ/mol。与羧甲基相比，季铵基更利于Ag NP的制备，CMC-Ag、QCS-Ag和QCMC-Ag的含银量分别是0.67‰、4.85‰和5.57‰，Ag NP粒径主要分布在60⁸0nm、40⁶0nm和5¹2nm范围内。FT-IR和NMR证明，在反应过程中壳聚糖分子链结构保持完整并且羧甲基和季铵基不能完全反应用于制备Ag NP，残留的壳聚糖衍生物可能形成网状结构包裹生成的纳米银颗粒并防止其团聚。通过TEM观察，Ag NP主要为球形，有少量方形和棒状。此外，壳聚糖基纳米银复合材料的热稳定性均高于壳聚糖衍生物。（2）载银CLS纳米复合材料的组装机制初始QCS与Ag+比例从100mg:0.1mmol增加到100mg:1mmol时，载银壳聚糖季铵盐/蒙脱土（QMAg）纳米复合材料和载银壳聚糖季铵盐/有机蒙脱土（QOMAg）纳米复合材料中银的含量分别从0.07‰增加到14.14‰、0.61‰增加到33.21‰；层状硅酸盐用量从5mg提高到20mg时，载银羧甲基壳聚糖季铵盐/累托石（QCRAg）纳米复合材料和载银羧甲基壳聚糖季铵盐/有机累托石（QCORAg）纳米复合材料中银的含量分别从0.16‰增加到7.75‰、0.91‰增加到12.04‰。有机层状硅酸盐中含有的表面活性剂并没有参与到制备Ag NP的化学反应中，但是可以提高Ag NP的生成量。TEM研究表明，干燥的载银CLS纳米复合材料中Ag NP颗粒依然是球形，保持着良好的分散状态且粒径均一，而且剥离的硅酸盐片层均匀地分布在壳聚糖基体中作为Ag NP的生长模板。载银的CLS纳米复合材料具有良好的热稳定性，且随着Ag+和层状硅酸盐用量的增加而增强。（3）载银的CLS纳米复合材料的抗菌机理抗菌实验结果表明，载银的CLS纳米复合材料具有卓越的抗菌性，且随着Ag NP含量的增加而提高。QMAg和QOMAg纳米复合材料最低抑菌浓度（MIC）分别为0.0005%和0.00001%（wt.），仅是QM和QOM纳米复合材料的1/2000和1/200。其抗菌过程如下：首先，具有大比表面积的MMT具有吸附和固定细菌的作用，QCS与Gemini的疏水基团与细胞壁中脂蛋白、脂多糖和磷脂等亲脂性化合物发生作用，从而更好地吸附和固定细菌；其次，QCS和Gemini中季铵基与细胞表面形成复合物，改变细胞膜的通透性，扰乱细胞膜的正常生理活动；第三，Ag NP可以与细菌细胞壁和细胞质中含S、P的化合物作用，影响细胞的渗透和分裂，从而导致细菌的死亡。更多还原

【Abstract】 Silver nanoparticle （Ag NP） is one of the most widely used nanophase materials, which iscommonly prepared via chemical reduction method. However, the additional reducing andstabilizing agents are harmful to human or enviroment in some extent, and they cannot beseparated completely from Ag NP, which limits its applications in medicine and biocatalysisareas. Therefore, it is urgent to find the green reducing and stabilizing agents and developefficient preparation method of Ag NP for nano metal industry. Chitosan is a naturalbiopolymer with many hydroxyl groups. The intermolecular and intramolecular hydrogenbonds in chitosan result in its independent space on the molecular level, which can provide agood template for the growth of nanoparticles. Due to the confinement effect of the layerspace, layered silicate such as montmorillonite is known as two dimension nano-reactor, andconsidered to be the perfect stability carrier for nanoparticles. Chitosan-based layered silicate（CLS） nanocomposites are synthesized by chitosan or its derivatives intercalation into theinterlayer of layered silicate under an external force, they are hybrid materials which cancombine the excellent capability of chitosan and silicate. At present, CLS nanocompositeshave been studied extensively, however, few researches are about the preparation of metalnanoparticles by using CLS nanocomposites as carrier.The objectives of the present study were to prepare chitosan derivatives, organic layeredsilicate, CLS nanocomposites and exfoliated Ag NP loaded CLS nanocomposites undermicrowave irradiation, and the intercalation mechanisms, antibacterial mechanisms andfunctional applications were investigated. The results are listed as follow:1. Rapid preparation of water-soluble chitosan derivatives xia microwave irradiationmethod and their properties（1） Rapid preparation of chitosan derivatives with various degree of substitutionWater-soluble chitosan derivatives such as quaternized chitosan （QCS）, quaternizedcarboxymethyl chitosan （QCMC） and quaternized carboxymethyl chitosan oligosaccharides（QCMCO） were rapidly prepared under microwave irradiation in the aqueous solution. TheQCS obtained by microwave irradiation method had similar structure and higher degree ofsubstitution （DS） as compared to those obtained by traditional heating method. The degree ofsubstitution of carboxymethyl （DSCM） or quarternary ammonium （DSQ） groups of QCMC canbe controlled by changing the microwave time, microwave power and the dosage of modified agents, the highest DSCMand DSQof82%and48%respectively were obtained in theappropriate conditions.（3） Study on the properties of chitosan derivativesThe obtained QCS could flocculate CaCO3suspension. The flocculation behavior of QCSwas directly proportional to its DS and inversely proportional to the molecular weight, withthe best flocculation concentration of6mg/L.QCMCO had excellent oxidation resistance, which was positively proportional to itsconcentration and closely related to DSCMand DSQ. When the concentration of QCMCO wasonly5mg/mL, the scavenging rate on OH was63.6%, and the Fe²⁺chelating ability was81.98%.2. Rapid preparation of organic montmorillonite by microwave irradiation methodand their adsorption propertiesGemini-MMT （GMMT） and ester-MMT （EMMT） with large layer spacing were quicklyprepared by using new cationic surfactants of Gemini and Esterquat as modifier undermicrowave irradiation condition. With the saturated intercalation dosage of Gemini andEsterquat of0.5CEC and0.8CEC, the largest layer spacing of GMMT and EMMT was2.31nm and2.41nm respectively. In addition, the layer spacing of GMMT obtained by microwaveirradiation method （2.31nm） was larger than that by traditional heating method （2.23nm）.Gemini was connected with MMT by electrostatic interaction, with combination ways ofintercalation, intercalation-adsorption and adsorption. However, even if the intercalation ofEsterquat was saturated, it was still combined with MMT by adsorption with the unchangedlayer spacing.The surface of GMMT and EMMT was hydrophobic, rough and fluffy. Therefore，bothGMMT and EMMT had excellent adsorption ability. The adsorption ability of GMMTincreased with increasing chain length of Gemini molecules, with the maximum actualadsorption capacity of48mg/g. The adsorption process of EMMT for triclosan was followedas the Lange Samuel isothermal adsorption equation, with the maximum theoreticaladsorption capacity of133mg/g.3. The effect of molecular parameters on the structure and properties of CLSnanocomposites （1） The effect of dosage on the intercalation processThe layer spacing of carboxymethyl quaternized chitosan/organic montmorillonite （QCOM）nanocomposites was proportional to the dosage of QCMC, when the DSCMand DSQof QCMCwas56.3%and74.6%respectively and its weight molecular weight （Mw） was2.9×105. Thelayer spacing of carboxymethyl quaternized chitosan oligosaccharide/organic rectorite（QCOOR） nanocomposites showed a firstly raised and then decreased trend with theincreasing dosage of QCMC, which the DSCMand DSQof QCMCO was88%and75%respectively and its Mwwas2×104.（2） The effect of DS on the intercalation processIn the QCOM nanocomposites which obtained by the QCMC with Mwof2.6×105³.0×105,the higher DSQcould promote the intercalation reaction, and extend the layer spacing ofQCOM nanocomposites. For example, when DSCMwas about30%, DSQincreased from29.6%to73.9%, the layer spacing of QCOM nanocomposites increased from3.70nm to4.50nm. But, the layer spacing of QCOM nanocomposites showed firstly increased and thendecreased trend with the increasing DSCMof QCMC. For example, when DSQwas about30%,DSQincreased from30.4%to85.2%, the layer spacing of QCOM nanocomposites increasedfrom3.70nm to4.22nm, and then decreased to3.79nm.In the QCOOR nanocomposites obtained by the QCMCO with Mwof8×103².0×104, theenhancemnt of the DSCMwas benefit for intercalation reaction, and getting larger layerspacing. For example, when DSQwas about45%, DSQincreased from23%to91%, the layerspacing of QCOOR nanocomposites increased from4.37nm to4.78nm. But DSQhad littleimpact on the layer spacing of QCOOR nanocomposites.（3） Preparation of exfoliated CLS nanocompositesThe exfoliated QCOM nanocomposites can be obtained when Mwof QCMC was2.6×105³.0×105, its DSCMand DSQwas53.6%and41.3%respectively, and the mass ratio ofQCMC to OMMT was8:1. But the exfoliated QCOOR nanocomposite was obtained whenMwof QCMCO was8×103².0×104, its DSCMand DSQwas88%and75%respectively, andthe mass ratio of QCMCO to OREC was4:1. Besides, the exfoliated quaternizedcarboxymethyl chitosan/rectorite （QCR） nanocomposite was obtained when Mwof QCMCwas8×103².0×104, its DSCMand DSQwas72%and80%respectively, and the quality ratio of QCMC to REC was above4:1.4. Study on the performance of CLS nanocomposites（1） Flocculation behavior of CLS nanocompositesQuaternized chitosan/organic montmorillonite （QOM） nanocomposites which combined theexcellent performance of QCS and OMMT showed good flocculation capacity. Theflocculation efficiency of QOM nanocomposite on CaCO3suspension was more than70%,when its dosage was0.005mg/L, which was only one-thousandth dosage of the traditionalflocculant such as cationic starch.（2） The controlled-release behavior of CLS crosslinked nanocomposite microsphereThe swelling behavior of quaternized carboxymethyl chitosan/organic montmorillonite（QCOM） nanocomposite （AQCOM） microsphere crosslinked with alginate was significantlyaffected by OMMT. With the mass ratios of QCMC to OMMT increased from1:1to8:1inQCOM nanocomposites, the swelling ratios of AQCOM microspheres was reached from44%to197%. The encapsulation efficiency of AQCOM microspheres increased with increasingcontent of QCMC and the layer spacing of QCOM nanocomposites. An appropriate dosage ofOMMT could be contributed to the controlled-release behavior of AQCOM microspheres, butexcessive levels of OMMT could destroy the behavior. In addition, the in vitro activecutaneous anaphylaxis test was carried out on guinea pigs, which revealed that AQCOMmicrosphere did not cause anaphylaxis.（3） The antibacterial behavior of CLS nanocompositesThe antibacterial activity of quaternized carboxymethyl chitosan oligosaccharides/rectorite（QCOR） nanocomposites was better than that of QCMCO. The Gram-positive bacteria andGram-negative bacteria which treated by QCOR nanocomposite had following phenomenon:the surface was collapse and deformation, the bacterial cell walls even ruptured and the cellcontents seep away, while the fungal spores burst and their normal physiological activity wasinhibited. In addition, the inhibitory effect of QCOR nanocomposite on the Gram-positivebacteria was better than that of Gram-negative bacteria and Fungi.5. Study on the structural assembly and antibacterial mechanism of Ag NP loadedCLS nanocomposites（1） Preparation of Ag NP loaded chitosan-based nanocomposites by Tollen method The spherical Ag NP with uniform size was quickly obtained under microwave irradiationby utilizing the reducing capacity of carboxymethyl groups and quaternary ammonium groups.The elevating reaction temperature or prolonging the reaction time was conducive to theformation of Ag NP. The preparation activation energy of carboxymethyl chitosan （CMC）,QCS and QCMC was69.7,62.8and103.7kJ/mol, respectively. Compared withcarboxymethyl groups, quaternary ammonium groups are more beneficial to prepare Ag NP.The silver content of CMC-Ag, QCS-Ag and QCMC-Ag was0.67‰,4.85‰and5.57‰respectively, and particle size of Ag NPs was mainly in the range of60-80nm,40-60nm and5-12nm, respectively. The results of FT-IR and NMR revealed that not all the carboxymethylgroups and quaternary ammonium groups were reducted for synthesizing Ag NP, and theremaining chitosan chain might form networks to wrap Ag NP and prevent their reunion.TEM micrographs showed that Ag NP was in mainly spherical, and few square or bar form. Inaddition, the thermal stability of Ag NP loaded chitosan-based composites was higher thanthat of chitosan derivatives.（2） The assembly mechanism of Ag NP loaded CLS compositesWhen the mass ratio of initial quaternized chitosan to Ag+increased from100mg:0.1mmol to100mg:1mmol, the silver content in Ag NP loaded quaternizedchitosan/montmorillonite （QMAg） nanocomposites and Ag NP loaded quaternizedchitosan/organic montmorillonite （QOMAg） nanocomposites increased from0.07‰to14.14‰and0.61‰to33.21‰, respectively. And when the dose ratio of clay increased from5mg to20mg, the silver content in Ag NP loaded quaternized carboxymethylchitosan/rectorite （QCRAg） nanocomposites and Ag NP loaded quaternized chitosan/organicrectorite （QCORAg） nanocomposites increased from0.16‰to7.75‰and0.91‰to12.04‰,respectively.The surfactant in the organic clay did not take part in the chemical reaction of Ag NPpreparation, but it could increase the yield of Ag NP. TEM micrographs showed that Ag NPmaintained spherical in drying Ag NP loaded CLS nanocomposites, with uniformity size anddispersion, and the exfoliated silicate layers were evenly distributed in chitosan derivativesmatrix as the growth template of Ag NP. Ag NP loaded CLS nanocomposites showedexcellent thermal stability, which enhanced with increasing amount of Ag+and clay. （3） The antimicrobial mechanism of Ag NP loaded CLS nanocompositesQMAg and QOMAg nanocomposites had excellent antibacterial activity which wasincreased with increasing Ag NP content, and the minimum inhibitory concentration （MIC）was0.0005%and0.00001%（wt.） respectively, which was only1/2000and1/200time thanQM and QOM nanocomposites. The antimicrobial course may be the following: firstly, MMTwith large specific surface area had the capacity of adsorption and immobilization onmictobes, hydrophobic groups in QCS and Gemini can also be associated with the cell wall oflipoprotein, lipopolysaccharide and phospholipids and other lipophilic compounds, whichresulted in better adsorption and immobilization on bacteria; secondly, quaternary ammoniumgroups in QCS and Gemini can form complexes with cell surface, thereby the permeability ofcell membrane was changed, cell membrane of normal physiological activity was disrupted;thirdly, Ag NP can be associated with bacterial cell wall and cytoplasm containing S, Pcompound, which can affect cell infiltration and split, resulting in the death of bacteria.更多还原