Politecnico di Milano, Department of Chemistry, Materials and Chemical Engineering "G. Natta" , Via Mancinelli 7, 20131 Milano, Italy.
Department of Chemistry and Biology, Università degli Studi di Salerno , Via Giovanni Paolo II 132, 84084 Fisciano, Salerno, Italy.
Biomacromolecules. 2017 Dec 11;18(12):3978-3991. doi: 10.1021/acs.biomac.7b01026. Epub 2017 Nov 28.
In this work, carbon papers and aerogels based on graphene layers and chitosan were prepared. They were obtained by mixing chitosan (CS) and a high surface area nanosized graphite (HSAG) in water in the presence of acetic acid. HSAG/CS water dispersions were stable for months. High resolution transmission electron microscopy revealed the presence of few graphene layers in water suspensions. Casting or lyophilization of such suspensions led to the preparation of carbon paper and aerogel, respectively. In X-ray spectra of both aerogels and carbon paper, peaks due to regular stacks of graphene layers were not detected: graphene with unaltered sp structure was obtained directly from graphite without the use of any chemical reaction. The composites were demonstrated to be electrically conductive thanks to the graphene. Chitosan thus makes it possible to obtain monolithic carbon aerogels and flexible and free-standing graphene papers directly from a nanosized graphite by avoiding oxidation to graphite oxide and successive reduction. Strong interaction between polycationic chitosan and the aromatic substrate appears to be at the origin of the stability of HSAG/CS adducts. Cation-π interaction is hypothesized, also on the basis of X-ray photoelectron spectroscopy findings. This work paves the way for the easy large-scale preparation of carbon papers through a method that has a low environmental impact and is based on a biosourced polymer, graphene, and water.
在这项工作中，制备了基于石墨烯层和壳聚糖的碳纸和气凝胶。它们是通过在醋酸存在下将壳聚糖（CS）和高比表面积纳米石墨（HSAG）混合在水中制得的。HSAG/CS 水分散体可稳定数月。高分辨率透射电子显微镜显示，水悬浮液中存在少量石墨烯层。这种悬浮液的浇铸或冻干分别导致了碳纸和气凝胶的制备。在气凝胶和气凝胶的 X 射线光谱中，都没有检测到由于石墨烯层的规则堆叠而产生的峰：未经任何化学反应，直接从石墨获得了具有未改变的 sp 结构的石墨烯。由于石墨烯的存在，复合材料表现出导电性。壳聚糖使得可以直接从纳米石墨获得块状碳气凝胶和柔性、独立的石墨烯纸，而无需氧化为氧化石墨和随后的还原。多阳离子壳聚糖与芳族基质之间的强相互作用似乎是 HSAG/CS 加合物稳定的原因。基于 X 射线光电子能谱的发现，还假设存在阳离子-π 相互作用。这项工作为通过一种对环境影响小、基于生物源聚合物、石墨烯和水的方法，轻松大规模制备碳纸铺平了道路。
