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应用壳聚糖及其衍生物绿色合成纳米材料
【作者】 彭长兰；
【导师】 徐峰；
【作者基本信息】 陕西师范大学 ， 有机化学， 2008， 硕士
【摘要】 纳米技术是20世纪80年代末期诞生并正在迅速崛起的用原子和分子创制新物质的技术。它不仅包含以观测、分析和研究为主线的基础学科,还包括如纳米颗粒的合成、加工以及具有纳米结构的材料的制造等应用研究。由于材料尺寸纳米化,因而纳米结构粒子表现出一系列奇特的物理、化学性质。金属纳米材料的奇异特性引起了科学家浓厚的研究热情。多糖是各种单糖的缩聚物,是地球上最丰富的可再生天然有机物之一,多糖的相对分子量比较大,大多带有负电荷,由于是一种多羟基的高分子物质,所以可以在分子间通过氢键形成超分子,可以用作模板来引导纳米晶体的生长。以多糖为模板调控无机晶体的生长是近年来一个新的研究方向。利用组成多糖的单糖残基种类差异、连接位置和糖苷键的差异,链内或链间形成氢键的二级结构差异,可以组成具有多样化构象、不同分子质量的多糖模板,从而制备出具有不同结构和独特性能的无机晶体材料。利用生物多糖制备纳米材料具有诸多优点,如多糖资源丰富,可再生,成本低廉;而且制备过程中的化学反应都在水体系中进行,所以可以避免有机溶剂的使用。本研究论文主要包含以下三个方面的内容:第一,多糖在合成纳米金属及金属化合物中的研究概况综述。着重介绍了淀粉、壳聚糖等一类常见高分子多糖在合成纳米材料中的应用。多糖在合成纳米材料的过程中不仅充当稳定剂及保护剂的作用,有些甚至还作为还原剂还原金属离子从而得到纳米金属材料,这就避免了以往纳米材料制备过程中使用有机表面活性剂等高毒害物质,满足绿色合成的要求。应用多糖合成纳米材料是近几年来新兴的研究课题,制备的纳米材料多限于金、银等不活泼的单质金属,铜纳米材料的合成本身就很少见,应用多糖合成的例子未见报道。第二,水相中以氧化还原法制得铜纳米颗粒。其中壳聚糖作为保护剂,抗坏血酸充当还原剂,对壳聚糖的浓度、抗坏血酸与铜离子的浓度比、温度、反应时间四个方面对制备纳米铜颗粒的影响进行了系统研究,获得了制备纳米金属铜的最佳条件:壳聚糖质量分数为0.4%、抗坏血酸与铜离子的浓度比为24、反应温度为80℃、反应时间为4h。对制得的铜纳米粒子利用TEM、XRD、SEM等方法进行了表征。该法具有操作简单,对仪器设备要求低,对环境少污染等优点,且绿色环保地解决了纳米粒子易于团聚的难题。制备出的铜纳米颗粒具有分散性高、粒径均匀、纯度高等优点。第三,以壳聚糖的衍生物-羧甲基壳聚糖为稳定剂和保护剂,在水相中以共沉淀法将醋酸铜中铜离子与硫化钠中硫离子共沉淀得以制备分散性高、粒径均匀、纯度高的硫化铜纳米粒子。通过改变温度可以控制纳米粒子的粒径大小,得到10 nm-45 nm粒径均匀的纳米硫化铜粒子。
【Abstract】 Nanoscience and technology is based on the science of making materials at the size level of nanometer scales.It emerged in the 1980s and has been increasingly developed.It not only includes the basic research subjects such as observation,analysis,but also the preparation,process and synthesis of nanostructure materials.Nanostructure materials exhibit novel physical and chemical properties due to the nanometer scale effect.Polysaccharide is the condensation polymer of saccharide,which is one of the richest renewable natural organic macromolecules in the earth.It usually has large molecular weight and most of them have negative charge.Polyhydroxylated macromolecules present interesting dynamic supramolecular associations facilitated by inter- and intra-molecular hydrogen bonding resulting in molecular level capsules,which can act as templates for nanoparticle growth.Polysaccharide as template for modulated the growth of the inorganic crystals has become a new research topic in recent years.The structure and properties of inorganic crystals can be controlled by various kinds of polysaccharide templates with different conformation and different molecular weight.These polysaccharide templates can be fabricated by adjusting the kinds of monosaccharide residues,changing the positions of linker and indican bond,and changing the second-grade structure by adjusting the hydrogen-bond of intra- or inter-chain,etc.It has many advantages,for example,polysaccharide is readily available,renewable and low costs.Besides,the chemical reaction for the preparation of the nanomaterials using polysaccharide as the template can be carried out in aqueous system and organic solvents can be completely avoided.This thesis consists of three parts:Studying the application of polysaccharides in synthesis of nanomaterials has drawn a great attention in recent years.The process of polysaccharides and its derivatives applied in synthesis of nanomaterials was reviewed in the first part of this thesis,several familiar polysaccharides such as starch and chitosan were emphasized.In the reaction,polysaccharides not only act as stabilizing agent,protecting agent,but also reducing agent,this method can efficiently escaped of some toxic organic chemicals and fulfilled the requirement of green chemistry.So far,polysaccharides were used for synthesis of some inert metal nanoparticle,such as gold and silver,rare for other metal nanoparticle.For copper metal nanoparticle,no report was found due to it is easy oxygenation.In the second part,the method of synthesis of copper nanoparticle in aqueous phase was reported,in which using chitosan as protecting agent,ascorbic acid as reducing agent.Different reaction temperature,reaction time,ratio of ascorbic acid/copper ion(Ⅱ) concentration,and chitosan concentration were explored.The optimum condition is as follows:chitosan concentration is 0.4 wt%,ascorbic acid/copper ion(Ⅱ) concentration ratio 24,reaction time 4h,reaction temperature 80℃.The copper nanoparticle obtained in above process was characterized by TEM, XRD and SEM.The diameter of copper nanoparticle show narrow distribution with highly dispersed.This process is very simple in control and do not need complicated techniques and equipments.In the third part,nano-copper sulfide with highly dispersed and narrow distribution was obtained by co-precipitation.In this process carboxymethyl-chitosan,one of the derivatives of chitosan was used as protecting agent and stability agent.The size of the nanoparticle can be adjusted in the range of 10 to 45nm by altering the reaction temperature.