【摘要】 石墨烯是由sp2杂化碳原子组成的具有蜂窝状结构的二维原子晶体.石墨烯的共价化学修饰是石墨烯研究领域的一个新的热点,也是石墨烯材料的表面改性和能带调控、以及合成新型二维石墨烯衍生物的重要途径.完整的二维蜂窝结构和离域大π键使得石墨烯的化学性质非常稳定,难以通过常规的化学反应获得高效的表面修饰,这是石墨烯共价化学的主要挑战.近年来,我们发展了一系列基于光化学原理的石墨烯共价修饰方法,利用光化学过程产生的活性自由基实现了石墨烯的高效共价加成和氧化反应,为石墨烯的光化学能带工程奠定了理论和实验基础.本文将以这些研究成果为主线,系统地阐述石墨烯的光化学修饰方法及其二维反应特性,并对该领域的未来发展趋势和所面临的挑战进行简要的展望.更多还原

【Abstract】 Graphene, a two-dimensional(2D) atomic crystal composed of single-layer hexagonal mesh of carbon atoms, is one of the most exciting materials being investigated today. Graphene chemistry, the covalent functionalization of graphene as a giant molecule, provides a promising approach to controllably engineer graphene’s band structure, create novel graphene derivatives and tailor the interfacial characteristics. One of the great challenges for graphene functionalization originates from its strong chemical stability, thus highly reactive chemical species are needed as the reactants. In recent years, we have been working on the photo-induced free radicals-based photochemistry of graphene, targeting the efficient graphene functionalization for its band structure engineering. Various photochemical modification methods have been developed, such as photochemical chlorination, photochemical methylation, photocatalytic oxidation and bifacially asymmetric functionalization of graphene. The homogeneous and nondestructive photochlorination of graphene could remove the conducting π-bands and open up a band gap in graphene. TiO2-based photocatalytic oxidation of graphene could realize photochemical tailoring of graphene, including ribbon cutting, arbitrary patterning on any substrate, layer-by-layer thinning, and localized graphene to graphene oxidation conversion. Using photochemical reaction of graphene as a probe, we have investigated the dimension effects on graphene chemistry, including the thickness, stacking order, single- and double-side, and edge dependent reactivity in graphene. After two-step functionalization of graphene, we have fabricated the thinnest Janus disc named Janus graphene, which comprises two kinds of decorations separated by the one-atom-thick carbon layer. It is found that chemical decorations on one side are capable of affecting both chemical reactivity and wettability of the opposite side, indicative of communication between the two grafted decorations separated by a single-layer graphene. In this review, we select several typical examples to demonstrate such kinds of photochemical graphene engineering and its intrinsic 2D reaction characteristics, together with a brief discussion on the future directions, challenges and opportunities in this research area.更多还原