基于石墨烯吸附净化材料的研究进展

石墨烯是一种片层状高比表面积碳材料,理论比表面积可达2 630 m2/g,具有非常高的吸附容量、良好的化学稳定性及机械性能等。有关石墨烯的发展和应用已成为当前的热点研究课题之一。详细讨论了石墨烯及其复合物在吸附重金属离子、有机污染物、有毒气体中的研究进展。最后对石墨烯及其复合物在吸附方面中的发展与应用做出了评价,同时对它们在吸附上的应用前景做了展望。     

超声剥离二次膨胀石墨制备石墨烯纳米片

以天然鳞片石墨为原料,氧化插层制备可膨胀石墨,微波热解膨胀后,对膨胀石墨进行二次氧化插层并微波膨胀,采用超声剥离法制备出包含大量少层数碳原子的石墨烯纳米片。采用傅里叶红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)、原子力显微镜(AFM)和拉曼光谱(Raman)对其结构和形貌进行分析。结果表明,氧化插层增大了石墨层间距,膨胀石墨更易于进一步氧化插层引入含氧基团;在微波作用下,石墨内部含氧基团热分解放出气体,进一步增大石墨层间距,甚至部分剥离;对二次膨胀处理的石墨薄片进行超声剥离可得到石墨烯纳米片,大部分石墨烯层数低于5层。     

Clean transfer of graphene on Pt foils mediated by a carbon monoxide intercalation process

Noble metals such as Pt are a perfect substrate for the catalytic growth of monolayer graphene. However, the requirements of the subsequent transfer process are not compatible with the traditional etching method. In this work, we find that the interaction of graphene with Pt foil can be weakened through the intercalation of carbon monoxide （CO） under ambient pressure. This intercalation process occurs on both hexagonal-shape graphene islands and irregular graphene patches on changing the CO partial pressure from 0 to 0.6 MPa, as observed by scanning electron microscopy （SEM）, Raman spectroscopy and X-ray photoemission spectroscopy. We demonstrate that, on a practical timescale, the intercalation ratio is proportional to the partial pressure of CO. Furthermore, we develop a clean transfer method of CO-intercalated graphene with water as a peeling agent. We show that this method enables the transfer of tens of micrometer-scale graphene patches onto SiO2/Si, which are free from metal or oxide particle contamination. This transfer method should be a significant step towards the dean transfer of graphene, as well as the recydable use of noble metal substrates.     

氧化石墨烯对水泥基复合材料自收缩的影响

氧化石墨烯(GO)表面富有大量的含氧基团,具有良好的亲水性,是新型纳米碳材料,会对水泥水化产物的形状及聚集态造成影响。本文将多层GO和水超声分散后形成GO分散液,对不同GO掺量的新拌水泥浆体的自收缩进行测试,并采用氮吸附法对其孔隙结构进行表征。结果表明,掺入GO会增加凝胶孔中的自由水,加快水泥水化速率,增大自收缩,且随着掺量的增加,自收缩会更加明显。由迟滞效应的特征推论出GO使得水泥浆体内部的孔隙呈现狭缝形。根据Kelvin方程的BJH法进行孔分布分析,探索GO对自收缩的调控机理。发现GO有助于细化内部孔径,使水泥浆体内部的大毛细孔向着小毛细孔转变,导致毛细孔压力增加,进而增加了水泥基复合材料的自收缩。     

石墨烯复合材料对水中金属离子的吸附研究进展

石墨烯是一种新型的纳米材料,具有一些独特的物理和化学性质,如高机械强度、良好的导电导热性、比表面积、化学稳定性好等。关于石墨烯的应用涉及到电子、信息、能源、材料、催化和生物医药等多个领域。概述了近年来石墨烯复合材料在水处理过程中对重金属离子的吸附研究,内容有石墨烯复合材料的制备及它们的吸附效果、吸附机理、吸附动力学、热力学,并就今后石墨烯复合材料在水处理过程中的应用进行了展望。     

不同浓度硼掺杂石墨烯吸附多层金原子的第一性原理研究

石墨烯与金属间过高的接触电阻严重影响了其在微纳电子领域的应用,B掺杂可以有效降低石墨烯的接触电阻。利用第一性原理研究了不同浓度B掺杂对石墨烯吸附多层Au原子的影响。首先计算了不同浓度B掺杂石墨烯的结合能,验证了掺杂石墨烯的稳定性;然后对掺杂石墨烯进行了结构优化并在其表面置入多层Au原子,计算了吸附模型的吸附能、赝能隙、局部态密度、电荷密度分布和电荷转移量。B掺杂浓度分别为1.39%,4.17%,6.94%,9.72%,12.50%和15.28%。结果表明:随着B掺杂浓度的提高,石墨烯吸附多层Au原子体系的赝能隙变宽,吸附能增加,结构稳定性得到提升;B原子与Au原子间杂化作用明显,具有较高的电荷密度和电荷转移量,可有效地降低石墨烯与多层Au原子间的接触电阻;但掺杂浓度为15.28%时,由于浓度过高吸附模型中石墨烯几何结构变形过大。     

Polyelectrolyte multilayer electrostatic gating of graphene field-effect transistors

We apply polyelectrolyte multilayer films by consecutive alternate adsorption of positively charged polyallylamine hydrochloride and negatively charged sodium polystyrene sulfonate to the surface of graphene field effect transistors. Oscillations in the Dirac voltage shift with alternating positive and negative layers clearly demonstrate the electrostatic gating effect in this simple model system. A simple electrostatic model accounts well for the sign and magnitude of the Dirac voltage shift. Using this system, we are able to create p-type or n-type graphene at will. This model serves as the basis for understanding the mechanism of charged polymer sensing using graphene devices, a potentially technologically important application of graphene in areas such as DNA sequencing, biomarker assays for cancer detection, and other protein sensing applications.     

Tunable plasmon-induced transparency based on graphene nanoring coupling with graphene nanostrips

We numerically and theoretically demonstrate a plasmon-induced transparency (PIT) at the mid-infrared region with finite-difference time-domain method. The system consists of an optically bright dipole mode and a dark quadrupole mode, which are supported by the graphene nanoring and graphene nanostrips, respectively. The coupling between the two modes introduces transparency window and large group delays. The pronounced PIT resonance can be easily modified by adjusting the geometric parameters and the Fermi level of graphene nanostructure. Our results suggest that the demonstrated PIT effect may be applicated in the slow-light device, active plasmonic switching, and optical sensing.     

Electrochemical actuator based on polypyrrole/sulfonated graphene/graphene tri-layer film

A tri-layer electrochemical actuator was fabricated by the electrodeposition of polypyrrole (PPy) onto a sulfonated graphene (SG)/reduced graphene oxide (RGO) bi-layer film. In this actuator, PPy and RGO were acted as actuation and conductive inert layers, respectively. The SG layer was used to enhance the interfacial interactions. The tri-layer actuator exhibited high and stable actuating performance for over 1000 actuation cycles, and the lifetime of the actuator was tested to be about 5000 cycles. The bending angle of the actuator is larger than 360° and its movement rate was higher than 150° s^− 1 under a driving potential of 1.0 V versus saturated calomel electrode. Furthermore, the low weight density of graphene based supporting layer greatly lowered the energy or charge consuming of the actuator during electrochemical actuation.     

石墨烯及其衍生物在聚合物方面阻燃的研究进展

随着聚合物燃烧事件的不断增多,阻燃引起了人们的关注。石墨烯及其衍生物因优异的阻燃性能成为了阻燃剂的研究热点,对石墨烯及其衍生物在环氧树脂、聚氨酯、聚苯乙烯、聚乙烯和聚对苯二甲酸乙二醇酯方面的阻燃进行了综述。     

Solar cells with graphene and carbon nanotubes on silicon

Graphene and carbon nanotubes (CNTs) represent attractive materials for photovoltaic (PV) devices due to their unique electronic and optical properties. Graphene and single-wall carbon nanotubes (SWNTs) layers can be directly configured as energy conversion materials to fabricate thin-film solar cells, serving as both photogeneration sites and charge carrier collecting/transport layers. SWNTs can be modified into either p-type conductor through chemical doping (like acidic purification) or n-type conductor through polymer functionalisation. The solar cells can be simply made of a semitransparent thin film of graphene (or SWNTs) deposited on a proper type of silicon substrate to create high-density Schottky (or p–n) junctions at the interface. The high aspect ratios and large surface area of these carbon nano-structured materials can benefit exciton dissociation and charge carrier transport thus improving the power conversion efficiency.     

单价选择性均相阳离子交换膜的制备及性能

以2-羟基-3-三甲铵基丙基壳聚糖为改性材料,商品化均相离子交换膜为基膜,电沉积法制备单价选择性阳离子交换膜,并探讨制膜液浓度、电沉积时间和交联环境等制膜条件对改性膜特殊分离性能的影响.用多种分析方法测试膜的相关性能,结果表明,单价选择性阳离子交换膜对一多价离子的分离效果明显,其中静电排斥是解释其分离特性的主要因素..     

热还原石墨烯的制备及其对重金属Pb~(2+)的吸附性

利用瞬时加热还原氧化石墨的方法制备石墨烯,将热还原的石墨烯用于吸附水中的重金属Pb2+,研究接触时间和pH值对吸附的影响。结果表明:pH值很大程度上影响了石墨烯的吸附性能,pH值大于7时吸附量显著增加,并在5min内达到平衡。透射电子显微镜和扫描电子显微镜分析表明石墨烯的片层很薄,层数较少。采用Langmuir和Freundlich吸附等温式拟合实验数据,Langmuir吸附等温式计算出的最大理论吸附量为86.5mg/g,相关系数R2为0.9982,Langmuir常数KL为10.7,与实验结果更接近。表明石墨烯具有超强的吸附能力,以单分子层的化学吸附为主。吸附动力学符合准二级动力学模型。     

聚吡咯/氧化石墨烯复合电极的制备及性能研究

采用直流电电化学制备了聚吡咯和聚吡咯/石墨烯薄膜电极,研究发现聚吡咯/石墨烯复合电极表面产生了很多小孔和一些羊角状的结构,这可能是由于在聚合过程中,聚合围绕石墨烯吸附对甲基苯磺酸根离子形成的球状体所致。而这些小孔和羊角状的结构在电极的充放电过程中为内层聚吡咯提供了离子交换的通道。在循环伏安的测试中,当扫描速率达到1000mV/S时,聚吡咯/石墨烯复合电极的容量依然保持在229F/g,而纯的PPy电极的容量仅保持在112F/g。     

表面活性剂对高浓度石墨烯水分散液制备的影响

分别选取阴离子型、阳离子型和非离子型3种类型表面活性剂,通过紫外可见光谱研究表面活性剂结构和浓度对高压均质-液相剥离法制备的石墨烯水分散液浓度的影响。通过高分辨透射电镜和激光粒度仪对所制备的石墨烯的品质进行分析。结果表明:长的疏水链段、双键和苯环官能团是促进表面活性剂作用发挥的关键结构,表面活性剂最优浓度略高于其临界胶束浓度。在测试范围内,Tween80效果最佳,其最佳作用浓度为0.012mmol·L^-1,所得石墨烯水分散液浓度为564.3mg·L^-1。表面活性剂的结构和浓度对石墨烯的品质无明显影响。     

背栅单层石墨烯场效应晶体管的构建及可靠性研究

采用低压化学气相沉积法(LPCVD)制备了高质量的单层石墨烯薄膜,通过湿法转移将所制备的单层石墨烯无损覆盖到两条平行粘贴在SiO2/Si衬底上的热释放胶带表面,胶带间距约500μm,进而对试样进行加热和切割,获得与SiO2/Si衬底紧密结合的石墨烯条带(约10 000μm×500μm),最后采用掩膜法在石墨烯条带上蒸镀金电极,构建成背栅石墨烯场效应晶体管。该方法简单易行,电学性能测试结果表明,石墨烯与金电极具有良好的欧姆接触,室温下,石墨烯的空穴迁移率约为735cm2/(V·s),且表现出了石墨烯所特有的双极性特征。背栅石墨烯场效应晶体管转移特性曲线表现出了滞回行为,且随着施加栅压的增大,滞回行为越来越显著,展示出高的性能可靠性。     

Scalable arrays of chemical vapor sensors based on DNA-decorated graphene

Arrays of chemical vapor sensors based on graphene field effect transistors functionalized with single-stranded DNA have been demonstrated. Standard photolithographic processing was adapted for use on large-area graphene by including a metal protection layer, which protected the graphene from contamination and enabled fabrication of high quality field-effect transistors （GFETs）. Processed graphene devices had hole mobilities of 1,640 ± 250 cm2.V-1.s-1 and Dirac voltages of 15 ± 10 V under ambient conditions. Atomic force microscopy was used to verify that the graphene surface remained uncontaminated and therefore suitable for controlled chemical functionalization. Single-stranded DNA was chosen as the functionalization layer due to its affinity to a wide range of target molecules and π-π stacking interaction with graphene, which led to minimal degradation of device characteristics. The resulting sensor arrays showed analyte- and DNA sequence-dependent responses down to parts-per-billion concentrations. DNA/GFET sensors were able to differentiate among chemically similar analytes, including a series of carboxylic acids, and structural isomers of carboxylic acids and pinene. Evidence for the important role of electrostatic chemical gating was provided by the observation of understandable differences in the sensor response to two compounds that differed only by the replacement of a （deprotonating） hydroxyl group by a neutral methyl group. Finally, target analytes were detected without loss of sensitivity in a large background of a chemically similar, volatile compound. These results motivate further development of the DNA/graphene sensor family for use in an electronic olfaction system.