新型还原氧化石墨烯/氮化碳复合纳滤膜制备及其性能

高性能石墨烯基复合膜的制备是目前国际研究热点,但是石墨烯基纳滤膜在脱盐中水通量较低,限制其在脱盐中的应用。采用聚多巴胺(PDA)改性聚砜(PSF)膜为基膜,将还原氧化石墨烯(rGO)和超薄氮化碳(uCN)纳米片通过真空抽滤法在基膜表面自组装制备新型还原氧化石墨烯/氮化碳复合纳滤膜。通过场发射扫描电子显微镜、透射电子显微镜、X 射线衍射仪、傅里叶变换红外光谱仪和X射线光电子能谱仪等研究uCN添加对膜结构和形貌的影响,并考察不同uCN添加比例、rGO用量及压力复合纳滤膜性能变化规律。结果显示当在100 mg·L^-1的rGO中添加uCN为20 mg·L^-1时所制备的rGO/uCN复合纳滤膜不仅保持良好盐离子截留率(对Na₂SO₄截留率85.86%,对NaCl截留率30.17%),且水渗透系数是rGO膜的2.15倍(88.50 L·m^-2·h^-1·MPa^-1)。     

Beyond graphene oxides: Emerging 2D molecular sieve membranes for efficient separation☆

Recent decades witnessed the significant progress made in the research field of 2D molecular sieve membranes.In comparison with their 3D counterparts, 2D molecular sieve membranes possessed several unique advantages like significantly reduced membrane thickness(one atom thick in theory) and diversified molecular sieving mechanisms(in-plane pores within nanosheets interlayer galleries between nanosheets). M. Tsapatsis first carried out pioneering work on fabrication of lamellar ZSM-5 membrane. Since then, diverse 2D materials typically including graphene oxides(GOs) have been fabricated into membranes showing promising prospects in energy-efficient gas separation, pervaporation, desalination and nanofiltration. In addition to GOs, other emerging 2D materials, including 2D zeolites, 2D metal–organic frameworks(MOFs), 2 D covalent-organic frameworks(COFs), layered double hydroxides(LDHs), transition metal dichalcogenides(TMDCs), MXenes(typically Ti_3C_2TX), graphitic carbon nitrides(typically g-C_3N_4), hexagonal boron nitride(h-BN) and montmorillonites(MT) are showing intriguing performance in membrane-based separation process. This article summarized the most recent developments in the field of 2D molecular sieve membranes aside from GOs with particular emphasis on their structure–performance relationship and application prospects in industrial separation.     

石墨烯量子点纳滤膜的仿生修饰及稳定性研究

亲水修饰是提高纳滤膜抗污染性能的重要方法。采用氯化胆碱（ChC）对石墨烯量子点（GQDs-TMC）纳滤膜进行后处理仿生修饰,模拟细胞膜上磷酰胆碱的两性离子抗污染表面。红外光谱（FTIR）和表面元素分析（EDS）表明ChC以共价键结合在纳滤膜分离层上。提高反应温度和氯化胆碱溶液浓度,可以增加纳滤膜的仿生修饰程度。ChC的季铵基团与GQDs-TMC纳滤膜分离层羧基基团形成两性离子结构,提高了仿生修饰（GQDs/ChC-TMC）纳滤膜的亲水性,降低了表面电势,提高了对染料分子和二价盐离子的截留率,并且显著增强了抗污染性能。经过酸、碱和氧化剂溶液浸泡处理及高温纳滤膜分离实验,GQDs/ChC-TMC纳滤膜的渗透率和截留率均未发生较大改变,表明仿生纳滤膜具有优异的化学稳定性和耐热稳定性。     

Graphene and graphene oxide and their uses in barrier polymers

Currently, there is great interest in graphene‐based devices and applications because graphene has unique electronic and material properties, which can lead to enhanced material performance. Graphene may be used in a wide variety of potential applications from next‐generation transistors to lightweight and high‐strength polymeric composite materials. Graphene, which has atomic thickness and two‐dimensional sizes in the tens of micrometer range or larger, has also been considered a promising nanomaterial in gas‐ or liquid‐barrier applications because perfect graphene sheets do not allow diffusion of small gases or liquids through its plane. Recent molecular simulations and experiments have demonstrated that graphene and its derivatives can be used for barrier applications. In general, graphene and its derivatives can be applied via two major routes for barrier polymer applications. One is the transfer or coating of few‐layered, ultrathin graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), on polymeric substrates. The other is the incorporation of fully exfoliated GO or rGO nanosheets into the polymeric matrix. In this article, we review the state‐of‐the‐art research on the use of graphene, GO, and rGO for barrier applications, including few‐layered graphene or its derivatives in coated polymeric films and polymer nanocomposites consisting of chemically exfoliated GO and rGO nanosheets, and their gas‐barrier properties. As compared to other nanomaterials being used for barrier applications, the advantages and current limitations are discussed to highlight challenging issues for future research and the potential applications of graphene/polymer, GO/polymer, and rGO/polymer composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39628.     

Exclusive and fast water channels in zwitterionic graphene oxide membrane for efficient water–ethanol separation

Graphene oxide (GO) membranes have shown great prospects as the next-generation membranes to tackle many challenging separation issues. However, the employment of GO membranes remains difficult for the precise separation of molecules with strong coupling effect and small size discrepancy such as water–ethanol. Herein, a new strategy of constructing exclusive and fast water channels in GO membrane was proposed to achieve high-performance water–ethanol separation via the synergy between zwitterion-functionalized GO and hydrophilic polyelectrolyte. The as-formed ordered and stable channels possess high-density ionic hydrophilic groups, which benefit from inhibiting the strong coupling between water and ethanol, facilitating the fast permeation of water molecules while suppressing ethanol molecules. As a result, the ultrathin GO-based membrane acquires exceptionally high separation performance with a flux of 3.23 kg/m² h and water–ethanol separation factor of 2,248 when separating water–ethanol (10 wt%/90 wt%) mixture at 343 K. This work paves a feasible way to construct 2D channels for the high-efficiency separation of strong-coupling mixtures.     

Reduced graphene oxide–gold nanoparticle membrane for water purification

The reduced graphene oxide–gold nanoparticle (rGO–Au NP) membranes are prepared by vacuum filtration method. The sizes of the Au NPs on the surface of the rGO are about 8–10 nm, and the lattice spacing of Au NPs is 0.0241 nm, which is relative to the cubic lattice of the gold crystal. The layer-by-layer stacking structure of rGO–Au NP membrane can be observed clearly by field emission scanning electron microscopy. The water flux of the rGO–Au NP membrane is as high as 204.1 L m^?2 h^?1 bar^?1, and its retention for Rhodamine B (RhB) is as high as 99.79%.     

氧化石墨烯在燃料电池质子交换膜中的应用

保护环境，开发环保型能源，对人类和社会具有重要意义。质子交换膜燃料电池由于其能量转化率高，可实现零排放，近年来引起了电池领域研究者们的兴趣。氧化石墨烯（GO）由于存在活性氧官能团，可以和离子型聚合物进行复合以制备复合质子交换膜。氧化石墨烯类的复合质子交换膜应用于燃料电池时可以提高膜在高温低湿度条件下的质子传导率，降低甲醇渗透率，提高电池的功率密度。本文首先介绍了氧化石墨烯的制备方法，然后从不同的离子型聚合物基质复合质子交换膜的类别出发，详细介绍了氧化石墨烯在Nafion、聚醚醚酮、聚苯并咪唑和壳聚糖等不同种类的离子型聚合物中的应用现状及作用机理，同时对其在质子交换膜的应用方面存在的问题及应用前景做了评论和展望。     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

Janus石墨烯量子点在生物膜中的输运行为：分子动力学模拟

作为纳米载体,石墨烯量子点已广泛应用于生物医药领域,然而对于异质结构的石墨烯量子点细胞膜内化路径研究不足。从空间异质性结构设计出发,构建了一系列不同氧化程度与空间异质分布的Janus石墨烯量子点。基于分子动力学模拟研究了不同结构的Janus石墨烯量子点跨膜输运行为,通过分析跨膜输运过程中的构型变化、分子间作用能量、溶剂可及面积等参数,发现Janus石墨烯量子点跨膜输运行为由亲水-亲油平衡、空间异质分布控制,且呈现外力牵引依赖性变化。本文在分子水平上系统研究了Janus石墨烯量子点与细胞膜相互作用规律,对其结构设计及生物医药应用提供理论指导。     

自支撑石墨烯炭膜的制备及气体分离性能

通过溶剂蒸发法得到聚酰胺酸（PAA）与氧化石墨烯（GO）的复合石墨烯膜,并经600℃炭化制备了具有良好柔韧性的仿贝壳珍珠层结构的自支撑石墨烯炭膜。通过X射线衍射和场发射扫描电镜对薄膜微观结构进行表征,并测试不同PAA固含量制备的石墨烯炭膜对CO₂和CH₄的分离性能。结果表明,炭化后,GO被还原成石墨烯,呈层状堆叠,堆叠的层间填充了空穴和残炭;石墨烯炭膜的CO₂渗透通量和CO₂/CH₄分离理想选择性随PAA加入量增加,CO₂通量最高可达824 barrer,此时CO₂/CH₄理想选择性达38.9。石墨烯层骨架和碳分子筛构成石墨烯炭膜的气体传输通道,本研究成果为柔性自支撑气体分离炭膜的制备开辟了新思路。     

疏水石墨烯膜的制备及其用于膜蒸馏脱盐的研究进展

膜蒸馏技术由于理论截盐率高、操作条件温和及对盐浓度灵敏度低等优势，在脱盐领域中展现出巨大潜力。近年来，人们开始关注石墨烯材料在膜蒸馏脱盐领域中的应用。本文首先概述膜蒸馏技术的基本原理及常用膜材料；接着介绍石墨烯的疏水性质和疏水石墨烯膜的制备；再详细综述石墨烯混合基质膜、石墨烯复合膜及石墨烯纯膜这三类疏水石墨烯膜在膜蒸馏脱盐中的应用；最后总结疏水石墨烯用于膜蒸馏脱盐面临的主要挑战及未来研究方向。     

Easy preparation of ultrathin reduced graphene oxide sheets at a high stirring speed

This work explored the synthesis of rGO sheets from graphene oxide (GO) using hydrazine solvent as reducing agent through chemical reduction. Meanwhile, GO films with a 2D structure were prepared from graphite flakes (starting material with an average flake size of 150 nm) by an Improved Hummer׳s method. Results showed that the chemical oxidation of graphite flakes carried out at room temperature could be used to prepare GO sheets in the initial stage. The conversion of GO into large-area rGO sheets with ~85% of carbon content could then be achieved by chemical reduction. RGO sheets with a lateral dimension of up to ~45 nm were obtained, which indicated the formation of an extremely thin layer of rGO sheets. A high degree of GO reduction was also realized using a high stirring speed (1200 rpm) for 72 h in a mixture of acids and potassium permanganate, resulting in a high carbon content of rGO with a large lateral dimension and area. Overall, our Improved Hummer׳s method with a high stirring speed (1200 rpm) for 72 h provided an easy approach to the preparation of large-area and ultrathin rGO sheets.     

Two-dimensional MXene hollow fiber membrane for divalent ions exclusion from water

Two-dimensional material membranes with fast transport channels and versatile chemical functionality are promising for molecular separation.Herein,for the first time,we reported design and engineering of two-dimensional Ti3C2Tx MXene (called transition metal carbides and nitrides) membranes supported on asymmetric polymeric hollow fiber substrate for water desalination.The membrane morphology,physic-ochemical properties and ions exclusion performance were systematically investigated.The results demonstrated that surface hydrophilicity and electrostatic repulsion and size sieving effect of interlayer channels synergistically endowed the MXene hollow fiber membrane with fast water permeation and efficient rejection of divalent ions during nanofiltration process.     

Luminescent graphene quantum dots fabricated by pulsed laser synthesis

Graphene has been the subject of intense research in recent years due to its unique electrical, optical and mechanical properties. Furthermore, it is expected that quantum dots of graphene would make their way into devices due to their structure and composition which unify graphene and quantum dots properties. Graphene quantum dots (GQDs) are planar nano flakes with a few atomic layers thick and with a higher surface-to-volume ratio than spherical carbon dots (CDs) of the same size. We have developed a pulsed laser synthesis (PLS) method for the synthesis of GQDs that are soluble in water, measure 2–6 nm across, and are about 1–3 layers thick. They show strong intrinsic fluorescence in the visible region. The source of fluorescence can be attributed to various factors, such as: quantum confinement, zigzag edge structure, and surface defects. Confocal microscopy images of bacteria exposed to GQDs show their suitability as biomarkers and nano-probes in high contrast bioimaging.     

Vertically aligned,polypyrrole encapsulated MoS2/graphene composites for high-rate LIBs anode

Ultrathin MoS₂ nanosheets were vertically anchored on the reduced graphene oxide (MoS₂/rGO) via hydrothermal method. To further engineering the surface conductivity, ultrathin polypyrrol (PPy) layer was coated on the MoS₂/rGO composite via in situ polymerization to form a bi-continuous conductive network with a sandwich-like structure. The graphene nanosheets and the PPy coating can facilitate the electrons transfer rate, while the ultrathin MoS₂ nanosheets can enhance the utilization efficiency of the active materials. The obtained MoS₂/rGO-10 composite exhibits high reversible specific capacity (970?mAh?g^?1 at 0.1?A?g^?1) and rate capability (capacity retention of 64% at 3.2?A?g^?1). Moreover, the PPy@MoS₂/rGO hybrids reveal lower specific capacity but better rate capability, and a “trade-off” effect between electrons and ions transfer resistance was observed. This easy-scalable PPy surface conductivity engineering strategy may be applied in the preparation of high-performance LIBs active materials.     

Transport properties of graphene oxide nanofiltration membranes: Electrokinetic modeling and experimental validation

There is a need for developing reliable models for water and solute transport in graphene oxide (GO) membranes for advancing their emerging industrial water processing applications. In this direction, we develop predictive transport models for GO and reduced-GO (rGO) membranes over a wide solute concentration range (0.01–0.5 M) and compositions, based on the extended Nernst–Planck transport equations, Donnan equilibrium condition, and solute adsorption models. Some model parameters are obtained by fitting experimental permeation data for water and unary (single-component) aqueous solutions. The model is validated by predicting experimental permeation behavior in binary solutions, which display very different characteristics. Sensitivity analysis of salt rejections as a function of membrane design parameters (pore size and membrane charge density) allows us to infer design targets to achieve high salt rejections. Such models will be useful in accelerating structure-separation property relationships of GO membranes and for separation process design and optimization.     

Near-UV-emitting graphene quantum dots from graphene hydrogels

We report a novel method to prepare graphene quantum dots (GQDs) from graphene hydrogels. Graphene hydrogels were prepared using a hydrothermal technique, and GQDs were released from the hydrogels on immersion of the hydrogels in low-polarity organic solvents. This method did not require additional treatments such as the centrifugation, filtration and dialysis typical of the general hydrothermal method. These GQDs were observed to fluoresce, with their strongest emission in the near-UV region, at ∼347 nm. Moreover, these GQDs, when in their pure state, formed a highly viscous liquid insoluble in water due to their lack of many oxygen-containing functional groups.     

Cu2ZnSnS4 nanocrystals and graphene quantum dots for photovoltaics

Semiconductor quantum dots exhibit great potential for applications in next generation high efficiency, low cost solar cells because of their unique optoelectronic properties. Cu(2)ZnSnS(4) (CZTS) nanocrystals and graphene quantum dots (GQDs) have recently received much attention as building blocks for use in solar energy conversion due to their outstanding properties and advantageous characteristics, including high optical absorptivity, tunable bandgap, and earth abundant chemical composition. In this Feature Article, recent advances in the synthesis and utilization of CZTS nanocrystals and colloidal GQDs for photovoltaics are highlighted, followed by an outlook on the future research efforts in these areas.     

掺杂石墨烯的ZnO复合材料研究进展

ZnO是一种低成本且应用广泛的材料,石墨烯具有较大的比表面积以及优良的吸附、光电等特性,易于与ZnO结合,可提高ZnO的性能.掺杂石墨烯的ZnO基材料在气体检测、抗菌表面涂层、发光二极管、透明导电电极和光催化等方面都有着应用性.本文概述了近几年来石墨烯掺杂ZnO材料作为导电薄膜、传感器、光催化剂等在光电子、生物医疗、环...     

Ionic liquid‐modified graphene/poly(vinyl alcohol) composite with enhanced properties

How to preserve the structure integrity of graphene while enhance its dispersion and compatibility in matrix attracts the attention of researchers in graphene/polymer nanocomposite field. In this paper, methacryloxyethyltrimethyl ammonium chloride (DMC), a kind of ionic liquids, was first used to non‐covalently functionalize graphene in the process of graphene oxide (GO) reduction. The as‐modified graphene (DMC‐rGO) was further incorporated into poly(vinyl alcohol) (PVA) matrix by solution casting technique to fabricate DMC‐rGO/PVA composites. The structure and properties of the obtained DMC‐rGO were investigated by X‐ray diffraction analysis (XRD), X‐ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscope (TEM), Atomic force microscopy (AFM), and Raman test. The results showed that graphene could be successfully modified by DMC through ionic–π interaction and the structure integrity of the graphene could be reserved by this non‐covalently approach. Furthermore, after co‐reduction process, some hydroxyl groups were introduced into DMC‐rGO. In virtue of these intrinsic properties of DMC‐rGO, the fabricated DMC‐rGO/PVA composites exhibit considerable enhancements in mechanical properties and remarkable improvements in thermal stability, as well as the enhancement in electrical conductivity at low DMC‐rGO loading. This simple modification approach gives a new opportunity to improve the performances of graphene/polymer composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45006.