纤维素基荧光纳米复合材料制备及性能研究

发布时间：2018-05-17 04:12

本文选题：纳米纤维素 + 荧光纳米晶体　；参考：《上海大学》2015年硕士论文

【摘要】：基于天然生物质的纳米纤维素(NFC),由于具有低密度特性、高长径比、高机械强度、晶体高度有序等结构性能,以及优良的生物相容性和生物可降解性,有望取代石油基聚合物材料应用于透明薄膜,柔性电子,生物医药、组装工程等领域。目前,关于纳米纤维素的制备技术和表面改性等方面的研究成为国内外研究的热点。因此,如何优化纳米纤维素精细分离、形貌结构以及表面基团控制,与功能材料形成有效复合接枝成为制备新型纤维素基纳米复合材料的关键。本文分别采用酸水解法和高压均质法从多种植物中提取制备纳米纤维素,通过不同的改性或组装方式,构筑了基于纳米纤维素的荧光纳米复合材料。1)以蒜皮、麻纤维、海带、浒苔为原料,通过酸水解法制备得到纳米纤维素,研究了酸水解过程中不同处理阶段样品形貌及晶型变化规律,并与高压均质法进行了对比分析。酸水解制得的纳米纤维素形貌呈纤维状,直径为10~50 nm,长度达几微米,长径比大于50,结晶度较高,其中蒜皮的结晶度可达74.2%;酸水解法得到的纳米纤维素具有更好的热稳定性,而高压均质法制得的纳米纤维素具有更高的长径比;采用TEMPO氧化法对纳米纤维素表面羟基羧基化改性,研究表明TEMPO氧化改性在引入羧基的能够同时保持纳米纤维素的形貌结构稳定性。2)以冬瓜汁为原料,通过一步水热法制备了氮掺杂的荧光碳点(CDs),与表面羧基化的NFC复合接枝,制得NFC/CDs纳米复合材料。荧光CDs的直径为4.5~5 nm,表面存在大量羟基、羧基以及含氮官能团,当激发波长为360 nm时,CDs的荧光强度达到峰值,对应的发射波长为448 nm,呈现蓝色荧光,对hep G2细胞无毒害作用,具有良好的细胞相容性及细胞成像特性。NFC/CDs纳米复合材料用于重金属离子Cu2+的检测吸附,经冷冻干燥后的NFC/CDs纳米复合材料具有网状多孔结构,有利于Cu2+的大面积快速吸附,检测浓度极限可达1μM。3)对Na YF4:Yb,Er(UCNPs)进行表面环氧化改性,实现UCNPs与NFC表面羟基的组装接枝,经压滤挤出快速脱水制得具有优异发光性能的NFC/UCNPs复合纳米纸。该荧光纳米纸复合兼具NFC纳米纸的透光性和UCNPs的荧光性能,其透光率与980 nm激光激发下的荧光强度受UCNPs含量影响,荧光强度随UCNPs增加而增强,而透光率降低,纳米纸中NFC/UCNPs构成的异质互穿网状结构有利于荧光纳米纸的光学稳定性。
[Abstract]:Because of its low density, high aspect ratio, high mechanical strength, highly ordered crystal structure, and excellent biocompatibility and biodegradability, the nano-cellulose based on natural biomass has good biocompatibility and biodegradability. It is expected to replace petroleum-based polymer materials in transparent film, flexible electronics, biomedicine, assembly engineering and so on. At present, the research on preparation technology and surface modification of nano-cellulose has become a hot spot at home and abroad. Therefore, how to optimize the fine separation of nano-cellulose, the control of morphology and surface group, and the effective composite grafting with functional materials become the key to the preparation of new cellulosic nanocomposites. Nanocellulose was prepared by acid hydrolysis method and high pressure homogenization method, respectively. The fluorescent nanocomposites based on nano-cellulose were prepared by different modification or assembly methods, such as garlic peel, hemp fiber, kelp, etc. Nanocellulose was prepared by acid hydrolysis method from Enteromorpha enteromorpha. The morphology and crystal morphology of samples in different stages of acid hydrolysis were studied and compared with high pressure homogenization method. The morphology of the nanocellulose prepared by acid hydrolysis is fibrous, the diameter is 10 ~ 50 nm, the length is several microns, the aspect ratio is more than 50, and the crystallinity of garlic peel can reach 74.2, and the nanocellulose obtained by acid hydrolysis has better thermal stability. The nanocellulose prepared by high pressure homogenization method has a higher aspect ratio. The surface hydroxyl carboxylation of nano-cellulose was modified by TEMPO oxidation method. The results showed that when carboxyl group was introduced in TEMPO oxidation modification, the morphology and structure stability of nanocellulose could be maintained at the same time. 2) the nitrogen-doped fluorescent carbon dot (NFC) was prepared by one step hydrothermal method, which was used as raw material to prepare nitrogen-doped carboxylated NFC, which was grafted with carboxylated NFC on the surface. NFC/CDs nanocomposites were prepared. The diameter of fluorescent CDs is 4.5 nm, and there are a large number of hydroxyl groups, carboxyl groups and nitrogen-containing functional groups on the surface. When the excitation wavelength is 360nm, the fluorescence intensity of hep / CDs reaches the peak and the corresponding emission wavelength is 448nm, which shows blue fluorescence and has no toxic effect on hep G2 cells. NFC / CDs nanocomposites have good cellular compatibility and cell imaging properties. NFC / CDs nanocomposites are used for the detection and adsorption of heavy metal ions Cu2. The freeze-dried NFC/CDs nanocomposites have reticular porous structure, which is conducive to the rapid adsorption of Cu2 in a large area. The limit of concentration is 1 渭 M. 3) the surface of NaYF4: YbPs is modified by epoxidation. The NFC/UCNPs composite nanocrystals with excellent luminescent properties are prepared by pressure-filtration extrusion and rapid dehydration after the assembly and grafting of UCNPs and NFC surface hydroxyl groups. The fluorescent nano-paper has both the transmittance of NFC nano-paper and the fluorescence property of UCNPs. Its transmittance and fluorescence intensity excited by 980nm laser are affected by the content of UCNPs. The fluorescence intensity increases with the increase of UCNPs, but the transmittance decreases. The heterogeneous interpenetrating network of NFC/UCNPs in nanocrystalline paper is beneficial to the optical stability of fluorescent nanocrystalline paper.
【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TB33

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