摘要

智能材料2021:农业废弃物中可持续纳米材料的新机遇-萨布·托马斯-印度圣雄甘地大学副校长

作者(年代):萨布托马斯

绿色化学始于从自然界中寻找良性方法开发纳米颗粒及其在抗菌、抗氧化和抗肿瘤领域的应用。生物废物是生产具有明确化学成分、大小和形态的典型纳米颗粒的环保起始材料。纤维素、淀粉、甲壳素和壳聚糖是世界上最丰富的生物聚合物。都属于多糖家族，其中纤维素是绿色植物初生细胞壁的重要结构成分之一。纤维素纳米颗粒(纤维、晶体和须)可以从黄麻、椰壳、竹子、菠萝叶、椰壳等农业废弃物中提取。甲壳素是仅次于纤维素的第二丰富的生物聚合物，它是真菌细胞壁的特征成分，节肢动物的外骨骼和甲壳素纳米颗粒(纤维，胡须)可以从虾和蟹壳中提取。壳聚糖是甲壳素的衍生物，由甲壳素去除乙酰基(脱乙酰化)制备而成。淀粉纳米颗粒可以从木薯和马铃薯废料中提取出来。这些纳米颗粒表面存在大量羟基，通过化学修饰(酯化、醚化、TEMPO氧化、羧化、羟基化等)实现功能化，可转化为智能功能性生物材料。这些纳米颗粒的制备包括一系列的化学和机械处理; crushing, grinding, alkali, bleaching and acid treatments. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to investigate the morphology of nanoscale biopolymers. Fourier transform infra-red spectroscopy (FTIR) and x ray diffraction (XRD) are being used to study the functional group changes, crystallographic texture of nanoscale biopolymers respectively. Since large quantities of bio wastes are produced annually, further utilization of cellulose, starch and chitins as functionalized materials is very much desired. The cellulose, starch and chitin nano particles are currently obtained as aqueous suspensions which are used as reinforcing additives for high performance environment-friendly biodegradable polymer materials. These nanocomposites are being used as biomedical composites for drug/gene delivery, nano scaffolds in tissue engineering and cosmetic orthodontics. The reinforcing effect of these nanoparticles results from the formation of a percolating network based on hydrogen bonding forces. The incorporation of these nano particles in several bio-based polymers have been discussed. The role of nano particle dispersion, distribution, interfacial adhesion and orientation on the properties of the ecofriendly bio nanocomposites have been carefully evaluated.