Abushammala Hatem, Mao Jia
Environmental Health and Safety Program, College of Health Sciences, Abu Dhabi University, Abu Dhabi P.O. Box 59911, United Arab Emirates.
Fraunhofer Institute for Wood Research (WKI), Bienroder Weg 54E, 38108 Braunschweig, Germany.
Nanomaterials (Basel). 2023 Feb 20;13(4):782. doi: 10.3390/nano13040782.
Electronic waste (e-waste) is the fastest growing waste stream and its negative impact on the environment and human health is major because of the toxicity and non-biodegradability of its constituents. For their biodegradability and nontoxicity, bio-based materials have been proposed as potential material candidates in the field of electronics. Among these, cellulose nanocrystals (CNCs) have many interesting properties including biodegradability, high mechanical strength, and possibility to functionalize. In terms of electrical properties, CNCs are electrically insulated, limiting their potential in electronics. This work aims to build up a poly(o-toluidine)-like shell around the CNCs to render them conductive. For this goal, the surface of the CNCs was carbamated using 2,4-toluene diisocyanate through the para-isocyanates and the ortho-isocyanates were later hydrolyzed to amine groups using HCl-acidified dimethylsulfoxide. The resultant o-toluidine-like molecules on the CNC surface were then polymerized using ammonium persulfate to form an electrically conductive shell around each CNC. The resultant CNCs were then characterized for their chemical, morphological, and electrical properties. Fourier-transform infrared analysis of the CNCs at each stage confirmed the expected chemical changes upon carbamation, hydrolysis, and polymerization and X-ray diffraction confirmed the permanence of the native crystalline structure of the CNCs. The atomic force microscopy images showed that the obtained CNCs were on average slightly thicker than the original ones, possibly due to the growth of the poly(o-toluidine) shell around them. Finally, using the four-point method, the obtained CNCs were electrically conductive with a conductivity of 0.46 S/cm. Such novel electrically conductive CNCs should have great potential in a wide range of applications including electronics, sensing, and medicine.
电子废弃物（电子垃圾）是增长最快的废物流，由于其成分的毒性和不可生物降解性，它对环境和人类健康的负面影响很大。基于生物可降解性和无毒特性，生物基材料已被提议作为电子领域潜在的材料候选物。其中，纤维素纳米晶体（CNCs）具有许多有趣的特性，包括生物可降解性、高机械强度以及功能化的可能性。就电学性能而言，CNCs是电绝缘的，这限制了它们在电子领域的潜力。这项工作旨在在CNCs周围构建一层聚邻甲苯胺类外壳，使其具有导电性。为了实现这一目标，使用2,4-甲苯二异氰酸酯通过对异氰酸酯对CNCs的表面进行氨基甲酰化，随后使用盐酸酸化的二甲基亚砜将邻异氰酸酯水解为胺基。然后使用过硫酸铵将CNC表面生成的类邻甲苯胺分子聚合，在每个CNC周围形成导电外壳。然后对所得的CNCs进行化学、形态和电学性能表征。对每个阶段的CNCs进行傅里叶变换红外分析，证实了氨基甲酰化、水解和聚合后预期的化学变化，X射线衍射证实了CNCs天然晶体结构的持久性。原子力显微镜图像显示，所获得的CNCs平均比原始的略厚，这可能是由于其周围聚邻甲苯胺外壳的生长。最后，使用四点法，所获得的CNCs具有导电性，电导率为0.46 S/cm。这种新型的导电CNCs在包括电子、传感和医学在内的广泛应用中应该具有巨大的潜力。
