氮掺杂石墨烯的p型场效应及其精细调控（英文）

Nitrogen Doped Graphene with a p-Type Field-Effect and Its Fine Modulation

石墨烯因独特的性质和潜在的应用在过去十年受到广泛重视。得益于石墨烯研究的繁荣,氧化石墨烯作为石墨烯的最常见的衍生物,近年来也获得广泛的研究。氧化石墨烯不仅可以通过高温退火还原得到光电性质都类似石墨烯的还原氧化石墨烯,而且因其结构中存在羧基、羰基和羟基等含氧基团,为石墨烯的性能调控提供了可能。常见的做法是通过引入外来原子比如氮原子来调控石墨烯的化学催化和光电性质。然而至今在氮掺杂石墨烯的研究中,氮的类型和所处化学环境对石墨烯电学性能的影响尚不清楚,而这会影响石墨烯后续的电学和催化应用。因此,合成特定类型的氮掺杂石墨烯并研究其对后续应用的影响是必要的。我们通过氧化石墨烯和邻芳基二胺的希夫碱缩合反应成功合成了吡嗪和吡啶氮掺杂石墨烯,研究了氮的类型对石墨烯电学性能的影响。吡嗪氮掺杂的石墨烯表现出弱的n型掺杂,而强吸电子的三氟甲基基团的引入,会让吡嗪氮掺杂的石墨烯由弱n型掺杂转变为明显的p型掺杂。当在吡嗪氮中同时引入吡啶氮时,石墨烯也表现为弱的p型掺杂。因此,石墨烯的性能可以通过控制吸电子基团和掺杂不同类型的氮来实现精细调控,从而为石墨烯的应用提供更多潜在可能。

Functionalized graphene has attracted significant interest over the past decade due to its unique physical properties and potential applications. Graphene oxide(GO), a readily scaled-up product, is a basic material for further functionalization. Using reductive processes, highly conductive reduced graphene oxide(RGO) can be obtained, which exhibits electrical and optical properties analogous to those of graphene. Moreover, due to the presence of oxygencontaining functional groups, its chemical reactivity and electronic properties can be easily tailored by chemical doping with nitrogen. However, developing strategies for doping graphene is challenging and the fundamental roles of the doping atom configuration and its environment on the resulting properties of graphene remain poorly understood. These properties are important for electrical and catalytic applications of graphene. Thus, synthesizing specific configurations of nitrogen-doped graphene and consequently investigating the electrical and catalytic properties of the product is imperative. Herein, we demonstrate an approach that allows for successful production of nitrogen-functionalized RGO using Schiff base condensation between the amino groups in an o-aryl diamine compound and the carbonyl groups in GO. Three typical nitrogen-containing species including o-phenylenediamine(OPD), 2,3-diaminopyridine(23 DAP), and bis(trifluoromethyl)-1,2-diaminobenzene(BTFMDAB) were used for functionalizing the GO samples, and the corresponding RGO derivatives(OPD-RGO, 23 DAP-RGO, and BTF-RGO) were obtained by thermal annealing. Pyrazine nitrogen was successfully introduced into graphitic framework, as confirmed by X-ray diffraction(XRD), Fourier transform infrared(FT-IR) spectra, thermal gravimetric analysis(TGA), Raman, and X-ray photoelectron spectroscopy(XPS). Field-effect transistors(FETs) based on the BTF-RGO exhibited hole-dominated ambipolar field-effect behavior with a Dirac point at a 9 V gate voltage and hole mobilities up to 2.5 times that of RGO. The weak p-type doping effect originated from the strongly electronwithdrawing trifluoromethyl groups. By studying the OPD-RGO and 23 DAP-RGO-based FETs, containing pyrazine nitrogen and mixed pyrazine/pyridine nitrogen, respectively, we found that pyrazine nitrogen provided weak n-type doping effects, while pyridine nitrogen exhibited weak p-type doping effects due to its electron-withdrawing ability. Enhanced p-type doping effect was accompanied by the introduction of groups with stronger electron-withdrawing ability into the graphitic framework. Impressively, pyridine nitrogen in the pyrazine nitrogen-doped RGO yielded a weak p-type doped graphene due to the electron-withdrawing effect of the pyridine nitrogen. Nitrogen-doped graphene can be finely tuned from weak n-type to weak p-type doping by adjusting the electron-withdrawing ability of o-aryl diamine compounds. This study demonstrates the effect of nitrogen configuration and its surrounding environment on the electrical properties of RGOs, providing additional possible applications.