石墨烯表界面化学修饰及其功能调控

石墨烯属于碳纳米材料家族中的一员,是一种单层的二维原子晶体,具有高硬度、高导热性、高载流子迁移率等诸多优良特性,被认为是新一代电子学器件的重要基础材料.近年来我们课题组利用石墨烯的这些优良特性在其表界面化学修饰及其功能调控方面开展了一系列研究工作.我们对石墨烯表界面进行了共价或非共价化学修饰,在一定程度上打开了石墨烯的带隙,并发展了具有传感功能的石墨烯器件.我们还制备了基于石墨烯的纳米电极,发展了新一代分子电子器件的普适性制备方法,实现了单分子器件的功能化.展望未来,以石墨烯为代表的碳基纳米材料将继续在纳电子器件研究领域发挥重要作用.     

基于单壁碳纳米管的功能分子电子器件研究

单壁碳纳米管具有完美的一维纳米结构、良好的导电性和电子弹道输运特性, 被认为是新一代电子学器件的重要基础材料. 作者介绍了两种构筑基于单壁碳纳米管的功能化场效应晶体管的策略, 使用纳米刻蚀法可以制备稳定的功能化单分子器件, 使用表面化学修饰法则提供了发展新型纳米传感器件的简易途径. 针对分子与电极间的非欧姆接触问题, 作者着重介绍了制备羧基功能化单壁碳纳米管点电极的普适性方法, 并将导电分子通过酰胺键共价嵌入碳纳米管电极之间, 从而制备稳定的单分子电子器件. 这一体系为发展无需标记、高选择性的快速单分子检测方法提供了机会, 在实际的工业应用及基础科学研究中都具有广阔的应用前景.     

自组装单分子膜功能器件

分子尺度电子学是利用单个分子或分子单层组装体作为活性单元来实现电子学功能的一门前沿科学领域.基于自组装单分子膜(SAMs)的分子器件在分子电子学的实用化道路上具有很大的发展潜力与应用前景.目前,SAMs功能器件的研究仍处于起步阶段,其性能还有很大提升空间.本文首先评述了SAMs器件的构筑方法,针对直接蒸镀金属顶电极会对SAMs造成破坏的问题,介绍了3类软接触电极,包括液态金属、导电高分子和石墨烯顶电极;然后以固态光开关器件为例介绍了近年来功能器件上的一些新进展,分子优化设计对于提升器件响应活性具有重要意义;同时总结了共轭聚合物SAMs器件的制备方法和性能,通过合理的结构设计,共轭聚合物能进行电荷的长程输运,并有望提供比小分子更优异的光电功能;最后讨论和展望了未来的发展方向.     

介电层上石墨烯的制备

石墨烯因其优异而独特的性能,自发现以来便受到了广泛的关注.为了实现石墨烯的进一步应用,可控制备大面积、高质量的石墨烯便成为研究人员需要首先攻克的难题.利用传统方法在金属基底上催化生长的石墨烯,需要先转移到介电层上才能进行后续的器件构筑.与之相比,介电层表面上直接生长石墨烯后,就可直接利用目前的硅加工工艺制备器件,从而避免因转移而引起的污染、破损,进而有望得到高质量、无污染的石墨烯样品.介绍了近年来介电层上直接生长石墨烯的研究进展,其中包括在各种传统介电层材料和新型六方氮化硼薄膜上制备石墨烯的各种方法.总结展望了介电层表面石墨烯制备的主要挑战及发展方向.     

基于喷墨打印石墨烯透明导电薄膜研究进展

随着柔性电子产品的应用日渐广泛,采用喷墨打印技术制备大面积柔性电子产品的技术引起了人们的关注。石墨烯由于具有优异的光学和机械性能,成为制备透明导电薄膜的理想材料。石墨烯可以通过物理或化学方法制备得到。而喷墨打印技术因具有成本低廉、操作简单等优点成为制备大面积柔性电子产品的方法之一。本文首先对石墨烯的性质和制备方法进行了简述,然后分别阐述了喷墨打印墨水条件和喷墨打印图案化控制,最后总结了透明导电薄膜的应用进展以及发展趋势。     

碳基纳米电极在分子器件中的应用

在器件微小化的发展趋势下,以单个或少数几个分子为主体的分子器件开辟了一条将“自下而上”的化学合成、组装与“自上而下”的微纳加工技术有机结合的研究新思路。如何有效构筑新型的功能化分子器件,使之有利于实现与硅基电子器件的互补集成,是该领域发展亟需解决的关键问题,这就需要相应地发展新的材料和方法来构筑器件。碳纳米管和石墨烯这2种新型碳家族纳米材料,由于其独具魅力的结构和性质自被发现以来便在全世界范围内掀起了研究热潮,可以作为一种良好的电极材料应用于分子器件的构筑和发展。主要简述了分子器件的发展概况,特别是碳纳米管和石墨烯作为电极材料在分子器件中的应用基础研究。     

喷墨打印高精度图案研究进展

近年来, 功能材料的图案化及其在高性能光电器件的应用研究受到了广泛关注. 与传统图案化方法相比, 喷墨打印技术更容易实现大面积复杂图案的直接书写和复合功能材料的图案化, 且制备简便, 成本低廉, 使其成为最受关注的图案化方法之一. 综述了近年来喷墨打印制备高精度图案的研究进展. 包括通过优化墨滴的化学组成、调控基材的化学或物理结构以及改进喷墨设备等方法以提高喷墨打印分辨率; 以及通过控制液滴内部的毛细流动和三相接触线的移动抑制喷墨液滴的“咖啡环”效应, 以实现均质打印. 文章最后展望了喷墨打印制备高精度图案的研究发展方向. 这些工作对于实现高性能器件的制备具有重要意义.     

基于石墨烯修饰电极的电化学生物传感

石墨烯是一种具有单原子厚度的二维碳纳米材料,具有大的比表面积、高的导电性和室温电子迁移率,以及优异的机械力学性能.石墨烯还具有电化学窗口宽,电化学稳定性好,电荷传递电阻小,电催化活性高和电子转移速率快等电化学特性.化学修饰石墨烯,特别是氧化石墨烯(GO)和还原氧化石墨烯(rGO),可以被宏量、廉价地制备出来.它们具有可加工性能,可以被组装、加工或复合成具有可控组成和微结构的宏观电极材料.因此,石墨烯及其化学修饰衍生物是用于电化学生物传感的独特而诱人的电极材料.例如,GO是一种化学修饰石墨烯,也是石墨烯的重要前驱体;其边缘具有大量的羧基可用于共价固定酶,从而能实现酶电极的生物检测.在GO上的不可逆蛋白吸附也可以促进蛋白质的直接电子转移以提高其电化学检测性能.但是,GO大量的含氧官能团破坏了石墨烯本征的共轭结构,降低了其电学性能并限制了其实际应用.GO可以通过化学、电化学、热还原等技术转化成rGO,从而能部分修复其共轭结构,提高其导电性与传感性能.另一方面,石墨烯是一种零带隙材料;原子掺杂可以调控其能带结构,提高其电催化性能.石墨烯材料也常常需要通过与其它功能材料的复合进一步改善其可分散与可加工性能,提高其电催化活性和电化学选择性.本文综述了本征石墨烯(包括GO,rGO和掺杂石墨烯)以及石墨烯与生物分子、高分子、离子液体、金属或金属氧化物纳米粒子等复合材料修饰电极在检测各种生物分子方面的研究进展,并对该研究领域进行了展望.     

通过构象诱导电感耦合机制光可逆调控有机场效应晶体管的性能

将有机场效应晶体管用于传感和开关实际应用的主要阻碍之一是其破坏性传感机制产生的一系列问题. 这里我们报道了一种智能的系统, 用光致变色分子螺吡喃(SP)和聚甲基丙烯酸甲酯(PMMA)结合作为栅介电材料, 得到的器件能以一种无损的方式, 通过光可逆调控器件的导电性能. 当螺吡喃分子发生可逆的光学异构时, 器件的电容和导电性随之发生显著而可逆的变化. 这种构象诱导电感耦合的作用机理提供了一种制备功能器件的新方法, 可以推广为利用其它刺激响应型分子来制备特定功能器件的普适性方法.     

有机光伏研究进展

以有机半导体材料为活性层的有机太阳能电池,可通过印刷制备大面积柔性器件,具有成本低、多彩、半透明等特点,是一种极具发展前景的光伏技术.研究者们多年来致力于设计高性能光伏材料,优化器件界面,改善活性层微观形貌,开发新型器件结构,探究器件工作机理等,目前实验室制备的小面积有机太阳能电池的能量转换效率已经超过18%.另外,面向有机光伏产业化,在制备大面积柔性器件、降低器件成本、提高器件寿命以及探究光伏建筑一体化和室内光伏等潜在应用方面的研究也取得了重要进展,在国际上处于领跑地位.中国科学家在有机光伏领域做出了诸多开创性和引领性的工作.本文首先对有机太阳能电池的背景进行简单介绍,接着按照分子工程、器件工程、器件物理和应用探索四个方面综述有机光伏领域的重要研究进展,最后对有机光伏所面临的机遇与挑战进行展望.     

Deformation of single‐walled carbon nanotubes by interaction with graphene: A first‐principles study

The interaction between single‐walled carbon nanotubes (SWNTs) and graphene were studied with first‐principles calculations. Both SWNTs and single‐layer graphene (SLG) or double‐layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper‐layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs. © 2015 Wiley Periodicals, Inc.     

Unique photoemission from single-layer graphene on a SiO2 layer by a substrate charging effect

Single-layer graphene (SLG) shows an anomalously large surface charging effect during scanning photoelectron microscopy (SPEM), which is distinguished from bi-layer graphene (BLG). The different behaviour is believed due to a different screening effect for SLG and BLG.     

Degradation of Single‐Layer and Few‐Layer Graphene by Neutrophil Myeloperoxidase

Biodegradability of graphene is one of the fundamental parameters determining the fate of this material in vivo. Two types of aqueous dispersible graphene, corresponding to single‐layer (SLG) and few‐layer graphene (FLG), devoid of either chemical functionalization or stabilizing surfactants, were subjected to biodegradation by human myeloperoxidase (hMPO) mediated catalysis. Graphene biodegradation was also studied in the presence of activated, degranulating human neutrophils. The degradation of both FLG and SLG sheets was confirmed by Raman spectroscopy and electron microscopy analyses, leading to the conclusion that highly dispersed pristine graphene is not biopersistent.     

Densely packed overlayer of iron phthalocyanine molecules grown on single-layer graphene

The FePc molecules form a series of order superstructures on single-layer graphene grown on Ru(0001) with increasing molecular coverage.     

Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction(ORR) electro-catalysts in MFCs. The rod-like carbon nanotubes(CNTs)were formed on the Fe–N/SLG sheets after a carbonization process. The maximum power density of1210 ± 23 m W·m~(-2) obtained with Fe–N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst(1080 ± 20 mW ·m~(-2)) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe–N/SLG was 3.91 ± 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electrochemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene(HCG, a kind of multilayer graphene) and high activity graphene(HAG, a kind of GO) under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs.The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe–N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst.It demonstrates that this kind of Fe–N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs.     

Effects of molecular adsorption on the electronic structure of single-layer graphene

The interaction of small molecules (CCl(4), CS(2), H(2)O, and acetone) with single-layer graphene (SLG) has been studied under steady-state conditions using infrared multiple-internal-reflection spectroscopy. Adsorption results in a broad and intense absorption band, spanning the ～200 to 500 meV range, which is attributed to electronic excitation. This effect, which has not previously been reported for SLG, has been further investigated using dispersion-corrected density functional theory to model the adsorption of H(2)O on SLG supported on an SiO(2) substrate. However, the ideal and defect-free model does not reproduce the observed adsorption-induced electronic transition. This and other observations suggest that the effect is extrinsic, possibly the result of an adsorption-induced change in the in-plane strain, with important differences arising between species that form liquid-like layers under steady-state conditions and those that do not. Furthermore, the C-H stretching modes of CH(2) groups, incorporated in the SLG as defects, undergo nonadiabatic coupling to the electronic transition. This leads to pronounced antiresonance effects in the line shapes, which are analyzed quantitatively. These results are useful in understanding environmental effects on graphene electronic structure and in demonstrating the use of the vibrational spectroscopy of H-containing defects in characterizing SLG structure.     

Quantification of the surface diffusion of tripodal binding motifs on graphene using scanning electrochemical microscopy

The surface diffusion of a cobalt bis-terpyridine, Co(tpy)(2)-containing tripodal compound (1·2PF(6)), designed to noncovalently adsorb to graphene through three pyrene moieties, has been studied by scanning electrochemical microscopy (SECM) on single-layer graphene (SLG). An initial boundary approach was designed in which picoliter droplets (radii ~15-50 μm) of the tripodal compound were deposited on an SLG electrode, yielding microspots in which a monolayer of the tripodal molecules is initially confined. The time evolution of the electrochemical activity of these spots was detected at the aqueous phosphate buffer/SLG interface by SECM, in both generation/collection (G/C) and feedback modes. The tripodal compound microspots exhibit differential reactivity with respect to the underlying graphene substrate in two different electrochemical processes. For example, during the oxygen reduction reaction, adsorbed 1·2PF(6) tripodal molecules generate more H(2)O(2) than the bare graphene surface. This product was detected with spatial and temporal resolution using the SECM tip. The tripodal compound also mediates the oxidation of a Fe(II) species, generated at the SECM tip, under conditions in which SLG shows slow interfacial charge transfer. In each case, SECM images, obtained at increasing times, show a gradual decrease in the electrochemical response due to radial diffusion of the adsorbed molecules outward from the microspots onto the unfunctionalized areas of the SLG surface. This response was fit to a simple surface diffusion model, which yielded excellent agreement between the two experiments for the effective diffusion coefficients: D(eff) = 1.6 (±0.9) × 10(-9) cm(2)/s and D(eff) = 1.5 (±0.6) × 10(-9) cm(2)/s for G/C and feedback modes, respectively. Control experiments ruled out alternative explanations for the observed behavior, such as deactivation of the Co(II/III) species or of the SLG, and verified that the molecules do not diffuse when confined to obstructed areas. The noncovalent nature of the surface functionalization, together with the surface reactivity and mobility of these molecules, provides a means to couple the superior electronic properties of graphene to compounds with enhanced electrochemical performance, a key step toward developing dynamic electrode surfaces for sensing, electrocatalysis, and electronic applications.     

Can a Procedure for the Growth of Single-layer Graphene on Copper be used in Different Chemical Vapor Deposition Reactors?

In the last decade, catalytic chemical vapor deposition (CVD) has been intensively explored for the growth of single-layer graphene (SLG). Despite the scattering of guidelines and procedures, variables such as the surface texture/chemistry of catalyst metal foils, carbon feedstock, and growth process parameters have been well-scrutinized. Still, questions remain on how best to standardize the growth procedure. The possible correlation of procedures between different CVD setups is an example. Here, two thermal CVD reactors were explored to grow graphene on Cu foil. The design of these setups was entirely distinct, one being a “showerhead” cold-wall type, whereas the other represented the popular “tubular” hot-wall type. Upon standardizing the Cu foil surface, it was possible to develop a procedure for cm²-scale SLG growth that differed only by the carrier gas flow rate used in the two reactors.     

Patterned growth of oriented 2D covalent organic framework thin films on single-layer graphene

Two-dimensional covalent organic frameworks (COFs) are polymer networks that organize molecular building blocks into porous, layered structures of interest for organic optoelectronic and energy storage devices. Current synthetic methods produce these materials as either insoluble, microcrystalline powders or as oriented thin films on various substrates, including single-layer graphene (SLG). Under these conditions, COF thin films form on both the graphene-coated and bare regions of the substrate, suggesting uncontrolled nucleation processes that occur either in solution or nonselectively on different surfaces. Here, we describe modified polymerization conditions that provide COF films selectively on SLG. This finding enables COF films to be grown on lithographically patterned SLG substrates, which provide insight into the uniformity of film growth across the substrate and factors relevant to their nucleation and growth. The ability to grow COF films selectively on lithographically patterned SLG will facilitate their integration into devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 378–384     

Single layer graphene: an alternative electrode material for ferroelectric liquid crystal based displays

We made comparative investigations on indium tin oxide (ITO) and single-layer graphene (SLG)-coated glass substrate as electrodes, specially for ferroelectric liquid crystal (FLC)-based system. We experimentally examined the comparative behaviour of important electro-optical FLC parameters for ITO- and SLG-based sample cells. The parameters are observed to be almost similar for both the cells. Interestingly, the value of threshold voltage is observed lower in SLG-based cell in comparison to that of conventional ITO/ITO cell. The presented results will definitely add a step to prove the suitability of graphene to be used as transparent electrodes in FLC-based display devices.