Obtaining cellulose nanofibers with a uniform width of 15 nm from wood
Obtaining cellulose nanofibers with a uniform width of 15 nm from wood
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DOI：
10.1021/bm700624p
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发表时间：
2007-10-01
影响因子：
6.2
通讯作者：
Yano, Hiroyuki
中科院分区：
文献类型：
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作者：
Abe, Kentaro;Iwamoto, Shinichiro;Yano, Hiroyuki
正如一些综合评论中所述，纳米纤维（通常定义为直径低于 100 nm 的纤维，1, 2）的制造目前备受关注，因为与其他商业纤维相比，纳米纤维具有独特的特性，例如非常大的表面积与体积比 3 以及形成高度多孔的网格 4。因此，这些纳米纤维材料是许多重要应用的主要候选材料，例如纳米复合材料的增强、组织工程支架和过滤介质。 5 已经报道了大量生产这些纳米纤维的合成和制造方法。特别是静电纺丝在过去十年中一直受到广泛关注。众所周知，纳米纤维是自然界产生的，例如肌腱和韧带中的胶原原纤维以及丝素蛋白。在各种天然纳米纤维中，纤维素微纤维是植物细胞壁的主要成分，也是由一些细菌产生的，是地球上最丰富的天然纳米纤维。微纤维的宽度为5至30纳米，6是通过氢键横向堆积长纤维素分子形成的高度结晶材料。由此产生的稳定结构具有出色的机械性能，包括高杨氏模量（沿纵向晶体区域为 138 GPa）7 和非常低的热膨胀系数（沿纵向为 10-7 K-1）。 8 因此，纤维素晶须和原纤维作为纳米复合材料的增强材料具有巨大的潜力，并且最近引起了人们的极大兴趣。 9-13 除了优异的机械性能外，纤维素纳米纤维还被证明是透明树脂的理想增强材料，因为它们的直径小于可见光波长的十分之一，因此不会发生光散射。 14 最近，Yano 等人。使用宽度为 50 nm 的细菌纤维素（以下简称 BC）纳米纤维开发了透明且柔性的纳米复合材料。 15 该复合材料在纤维含量高达 70% 时具有光学透明性，同时具有极低的热膨胀系数和高强度。此外，由于增强体的尺寸效应，各种基体树脂在更广泛的环境温度或折射率分布下可以获得高透明度，16扩大了在光电器件中的潜在应用。由于植物基纤维素纳米纤维有可能被提取成比BC更细的纤维，因此许多研究人员一直在广泛研究从木材和其他植物纤维中提取纳米纤维。在细胞壁中，纤维素纳米纤维嵌入半纤维素和木质素等基质物质中，至此，基质的去除
As described in some comprehensive reviews, the fabrication of nanofibers, generally defined as fibers with a diameter below 100 nm, 1, 2 is presently the subject of much attention because of their unique characteristics such as a very large surface-tovolume ratio3 and the formation of a highly porous mesh4 as compared with other commercial fibers. Therefore, these nanofibrous materials are prime candidates for many momentous applications such as reinforcement in nanocomposites, tissue engineering scaffolds, and filtration media. 5 A large number of synthesis and fabrication methods for producing these nanofibers have already been reported. In particular, electrospinning has been the subject of much attention over the past decade. It is well-known that nanofibers are produced in nature, for example, collagen fibrils in tendons and ligaments and silk fibroin. Among the variety of natural nanofibers, cellulose microfibrils, which are the major constituent of plant cell walls and are also produced by some bacteria, are the most abundant natural nanofiber on earth. The microfibrils, having a width ranging from 5 to 30 nm, 6 are highly crystalline materials formed by laterally packing long cellulose molecules with hydrogen bonding. The resultant stable structure has outstanding mechanical properties, including a high Young’s modulus (138 GPa in the crystal region along the longitudinal direction) 7 and a very low coefficient of thermal expansion (10-7 K-1 along the longitudinal direction). 8 Therefore, cellulose whiskers and fibrils have great potential for use as reinforcement in nanocomposites and have attracted a great deal of interest recently. 9-13 In addition to their exceptional mechanical properties, cellulose nanofibers have been shown to be an ideal reinforcement of transparent resins since they are free from light scattering due to their diameters being less than one-tenth of the visible light wavelength. 14 Recently, Yano et al. developed transparent and flexible nanocomposites using bacterial cellulose (hereafter referred to as BC) nanofibers 50 nm in width. 15 The composites are optically transparent at fiber contents as high as 70% in conjunction with a very low coefficient of thermal expansion and high strength. Furthermore, because of the size effect of the reinforcement, high transparency is obtained against wider distributions of ambient temperatures or refractive indices from various matrix resins, 16 expanding the potential applications in optoelectronic devices.Since plant-based cellulose nanofibers have the potential to be extracted into fibers thinner than BC, many researchers have been extensively studying the extraction of nanofibers from wood and other plant fibers. In cell walls, cellulose nanofibers are embedded in matrix substances such as hemicellulose and lignin, and, up unto this time, the removal of the matrix