An Effective Method for Bulk Obtaining Graphene Oxide Solids

We report an effective method for bulk obtaining exfoliated graphene oxide (GO) solids from their aqueous solutions, which were prepared from nature graphite by an oxidation method. Tyndall effect proved that GO solution has a colloidal nature. Different flocculants were used to coagulate GO colloidal, and it was found that NaOH had the most obvious coagulation effect to GO. Transmission electron microscopy, X‐ray diffraction and atomic force microscopy analysis demonstrated that there were a large number of complete few‐layer GO sheets with thickness of about 0.8 nm, and the surfaces were very smooth, almost free of impurities. Liquid state ¹³C NMR and Fourier transformation infrared spectra showed the presence of abundant benzene carboxylic, hydroxyl and epoxide groups in the basal planes of GO. The graphene materials reduced from GO solids had good electrical conductivity. Our work explored a simple and effective route to extract GO from their solution, which is the most important to GO and graphene researches and applications.     

Graphene: Safe or Toxic? The Two Faces of the Medal

Graphene is considered the future revolutionary material. For its development, it is of fundamental importance to evaluate the safety profile and the impact on health. Graphene is part of a bigger family which has been identified as the graphene family nanomaterials (GFNs). Clarifying the existence of multiple graphene forms allows better understanding the differences between the components and eventually correlating their biological effects to the physicochemical characteristics of each structure. Some in vitro and in vivo studies clearly showed no particular risks, while others have indicated that GFNs might become health hazards. This Minireview critically discusses the recent studies on the toxicity of GFNs to provide some perspective on the possible risks to their future development in materials and biomedical sciences.     

三维复合材料CdS@DMSA-GO的原位合成及其光催化性能

通过在石墨烯中引入内消旋-2,3-二巯基琥珀酸(DMSA)构建三维立体结构,原位合成了CdS@DMSA-GO复合材料。实验表明,反应温度对所得材料的结构和性能具有重要的影响。CdS@DMSA-GO-100℃对罗丹明B和刚果红具有最佳的吸附和光催化降解性能,降解效率可达96%以上。自由基捕获实验表明,·O2在催化过程中是主要的活性氧物质。     

Edge-Functionalized Nanographenes

Nanographenes (NGs) have recently emerged as new carbon materials. Their nanoscale size results in a size-dependent quantum confinement effect, opening the band gap by a few eV. This energy gap allows NGs to be applied as optical materials. This property has attracted researchers across multiple scientific fields. The photophysical properties of NGs can be manipulated by introducing organic groups onto their basal planes and/or into their edges. In addition, the integration of organic functional groups into NGs results in NG-based hybrid materials. These features make the post-synthetic modification of NGs an active research area. As obtainable information on chemically functionalized NGs is limited owing to their nonstoichiometry and structural uncertainty, their structural characterization requires a combination of multiple spectroscopic methods. Therefore, information on the characterization procedures of recently published chemically functionalized NGs is of value for advancing the field of NG-based hybrid materials. The present review focuses on the structural characterization of chemically functionalized NGs. It is hoped that this review will help to advance this field.     

Synthesis of monolayer-patched graphene from glucose

Graphene patchwork: A simple synthetic process requiring neither catalyst nor solvent was used to convert glucose directly into polycrystalline carbon sheets having a "patched" multidomain graphene structure with domains 2-15?nm in size. The carbon assemblies exhibit high conductivity, high specific surface area, and an unexpectedly good solution processability.     

Boron Nitride Nanomaterials for Thermal Management Applications

Hexagonal boron nitride nanosheets (BNNs) are analogous to their two‐dimensional carbon counterparts in many materials properties, in particular, ultrahigh thermal conductivity, but also offer some unique attributes, including being electrically insulating, high thermal stability, chemical and oxidation resistance, low color, and high mechanical strength. Significant recent advances in the production of BNNs, understanding of their properties, and the development of polymeric nanocomposites with BNNs for thermally conductive yet electrically insulating materials and systems are highlighted herein. Major opportunities and challenges for further studies in this rapidly advancing field are also discussed.     

Two‐Dimensional‐Material Membranes: A New Family of High‐Performance Separation Membranes

Two‐dimensional (2D) materials of atomic thickness have emerged as nano‐building blocks to develop high‐performance separation membranes that feature unique nanopores and/or nanochannels. These 2D‐material membranes exhibit extraordinary permeation properties, opening a new avenue to ultra‐fast and highly selective membranes for water and gas separation. Summarized in this Minireview are the latest ground‐breaking studies in 2D‐material membranes as nanosheet and laminar membranes, with a focus on starting materials, nanostructures, and transport properties. Challenges and future directions of 2D‐material membranes for wide implementation are discussed briefly.     

Design of Advanced MnO/N‐Gr 3D Walls through Polymer Cross‐Linking for High‐Performance Supercapacitor

Three‐dimensional, vertically aligned MnO/nitrogen‐doped graphene (3D MnO/N‐Gr) walls were prepared through facile solution‐phase synthesis followed by thermal treatment. Polyvinylpyrrolidone (PVP) was strategically added to generate cross‐links to simultaneously form 3D wall structures and to incorporate nitrogen atoms into the graphene network. The unique wall features of the as‐prepared 3D MnO/N‐Gr hybirdes provide a large surface area (91.516 m² g^?1) and allow for rapid diffusion of the ion electrolyte, resulting in a high specific capacitance of 378 F g^?1 at 0.25 A g^?1 and an excellent charge/discharge stability (93.7 % capacity retention after 8000 cycles) in aqueous 1 m Na₂SO₄ solution as electrolyte. Moreover, the symmetric supercapacitors that were rationally designed by using 3D MnO/N‐Gr hybrids exhibit outstanding electrochemical performance in an organic electrolyte with an energy density of 90.6 Wh kg^?1 and a power density of 437.5 W kg^?1.     

Hybrid Hydrogels of Porous Graphene and Nickel Hydroxide as Advanced Supercapacitor Materials

Graphene‐based hydrogels can be used as supercapacitor electrodes because of their excellent conductivity, their large surface area and their high compatibility with electrolytes. Nevertheless, the large aspect ratio of graphene sheets limits the kinetics of processes occurring in the electrode of supercapacitors. In this study, we have introduced in‐plane and out‐of‐plane pores into a graphene–nickel hydroxide (Ni(OH)₂) hybrid hydrogel, which facilitates charge and ion transport in the electrode. Due to its optimised chemistry and architecture, the hybrid electrode demonstrates excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the Ni(OH)₂ in the hybrid contributes a capacitance as high as 3138.5 F g^?1, which is comparable to its theoretical capacitance, suggesting that such structure facilitates effectively charge‐transfer reactions in electrodes. This work provides a facile pathway for tailoring the porosity of graphene‐based materials for improved performances. Moreover, this work has also furthered our understanding in the effect of pore and hydrogel structures on the electrochemical properties of materials.     

Advances in two-dimensional heterostructures by mono-element intercalation underneath epitaxial graphene

Two-dimensional (2D) materials have displayed many remarkable physical properties, including 2D superconductivity, magnetism, and layer-dependent bandgaps. However, it is difficult for a single 2D material to meet complex practical requirements. Heterostructures obtained by vertically stacking different kinds of 2D materials have extensively attracted researchers’ attention because of their rich electronic features. With heterostructures, the constraints of lattice matching can be overcome. Meanwhile, high application potential has been explored for electronic and optoelectronic devices, including tunneling transistors, flexible electronics, and photodetectors. Specifically, graphene-based van der Waals heterostructures (vdWHs) by intercalation are emerging to realize various functional heterostructures-based electronic devices. Intercalating atoms under epitaxial graphene can efficiently decouple graphene from the substrate, and is expected to realize rich novel electronic properties in graphene. In this study, we systematically review the progress of the mono-element intercalation in graphene-based vdWHs, including the intercalation mechanism, intercalation-modified electronic properties, and the practical applications of 2D intercalated heterostructures. This work would inspire edge-cutting ideas in the scientific frontiers of 2D materials.     

Fe3O4/Graphene Composite Anode Material for Fast-Charging Li-Ion Batteries

Composite anode material based on Fe₃O₄ and reduced graphene oxide is prepared by base-catalysed co-precipitation and sonochemical dispersion. Structural and morphological characterizations demonstrate an effective and homogeneous embedding of Fe₃O₄ nanoparticles in the carbonaceous matrix. Electrochemical characterization highlights specific capacities higher than 1000 mAh g⁻¹ at 1C, while a capacity of 980 mAhg⁻¹ is retained at 4C, with outstanding cycling stability. These results demonstrate a synergistic effect by nanosize morphology of Fe₃O₄ and inter-particle conductivity of graphene nanosheets, which also contribute to enhancing the mechanical and cycling stability of the electrode. The outstanding capacity delivered at high rates suggests a possible application of the anode material for high-power systems.     

Macroscopic Graphene Fibers Directly Assembled from CVD‐Grown Fiber‐Shaped Hollow Graphene Tubes

Using a copper wire as the substrate for the CVD growth of a hollow multilayer graphene tube, we prepared a macroscopic porous graphene fiber by removing the copper in an aqueous mixture solution of iron chloride (FeCl₃, 1 M ) and hydrochloric acid (HCl, 3 M ) and continuously drawing the newly released graphene tube out of the liquid. The length of the macroscopic graphene fiber thus produced is determined mainly by the length of the copper wire used. The resultant macroscopic graphene fiber with the integrated graphene structure exhibited a high electrical conductivity (127.3 S cm^?1) and good flexibility over thousands bending cycles, showing great promise as flexible electrodes for wearable optoelectronics and energy devices—exemplified by its use as a flexible conductive wire for lighting a LED and a cathode in a fiber‐shaped dye‐sensitized solar cell (DSSC) with one of the highest energy conversion efficiencies (3.25 %) among fiber‐shaped DSSCs.     

Ultrasonic Preparation of Hierarchical Graphene‐Oxide/TiO2 Composite Microspheres for Efficient Photocatalytic Hydrogen Production

Hierarchical graphene oxide (GO)‐TiO₂ composite microspheres with different GO/TiO₂ mass ratios were successfully prepared by mixing GO and TiO₂ microspheres under ultrasonic conditions. Ultrasonication helped the GO and TiO₂ microsphere to uniformly mix on the microscale. The results showed that the GO‐TiO₂ composites that were prepared by ultrasonic mixing exhibited significantly higher hydrogen‐evolution rates than those that were synthesized by simple mechanical grinding, owing to synergetic effects, including enhanced light absorption and scattering, as well as improved interfacial charge transfer because of the excellent contact between the GO sheets and TiO₂ microspheres. In addition, GO‐TiO₂‐3 (3 wt. % GO) showed the highest hydrogen‐generation rate (305.6 μmol h^?), which was about 13 and 3.3‐times higher than those of TiO₂ microsphere and GO‐P25 (with 3 wt. % GO), respectively. Finally, a tentative mechanism for hydrogen production is proposed and supported by photoluminescence and transient photocurrent measurements. This work highlights the potential applications of GO‐TiO₂ composite microspheres in the field of clean‐energy production.     

Flexible Magnetic Nanoparticles–Reduced Graphene Oxide Composite Membranes Formed by Self‐Assembly in Solution

A facile and robust route for the pre‐synthesized Fe₃O₄ nanoparticles (NPs) exclusively assembled on both sides of reduced graphene oxide (RGO) sheets with tunable density forming two‐dimensional NPs composite membranes is developed in solution. The assembly is driven by electrostatic attraction, and the nanocomposite sheets display considerable mechanical robustness, such as it can sustain supersonic and solvothermal treatments without NPs falling off, also, can freely float in solution and curl into a tube. The obtained two‐dimensional composite grain membranes exhibit superparamagnetic behavior at room temperature but responds astutely to an external magnetic field. In addition, these magnetic composite membranes show an enhanced absorption capability for microwaves. The grain sheets are attractive for biomedical, sensors, environmental applications and electric‐magnetic devices benefited from large surfaces, high magnetization moment, and superparamagnetic properties. The effective integration of oxide nanocrystals on RGO sheets provides a new way to design semiconductor–carbon nanocomposites for nanodevices or catalytic applications.     

A Conductive Hybridization Matrix of RuO2 Two‐Dimensional Nanosheets: A Hybrid‐Type Photocatalyst

A universal methodology to efficiently improve the photocatalyst performance of semiconductors was developed by employing exfoliated RuO₂ two‐dimensional nanosheets as a conducting hybridization matrix. The hybridization with a RuO₂ nanosheet is easily achieved by crystal growth or electrostatically derived anchoring of semiconductor nanocrystals on the RuO₂ nanosheet. An enhanced chemical interaction of inorganic semiconductor with hydrophilic RuO₂ nanosheet is fairly effective in optimizing their photocatalytic activity and photostability by the enhancement of charge separation and charge mobility. The RuO₂‐containing nanohybrids show much better photocatalyst functionalities than do the graphene‐containing ones. The present study clearly demonstrates that hydrophilic RuO₂ nanosheets are superior hybridization matrices, over the widely used hydrophobic graphene nanosheets, for exploring new efficient hybrid‐type photocatalysts.     

石墨烯在复合热电材料中的应用

热电材料是一种可以实现热能与电能之间直接相互转换的功能材料,在温差发电和热电制冷方面具有广阔的应用空间。石墨烯是一种单原子层厚度的二维碳材料,具有特殊的晶体结构和优异的物理化学性质。大量研究表明石墨烯优异的电学性能、超大的比表面积以及多样的边界结构有利于材料电、热性能的协同调控,使其在热电领域有较大的应用潜力。本文结合热电材料的性能特点,从石墨烯的结构与性能入手,综述了石墨烯自身作为热电材料时结构与性能的优化关系,并总结归纳了石墨烯与Bi₂Te₃、CoSb₃等传统无机热电材料以及与导电高分子热电材料构成纳米复合块体和薄膜时,对材料结构与热电性能的影响,并结合现存的问题对石墨烯在热电领域中的应用进行了展望。     

同构MOFs复合氧化石墨烯电极材料构筑高性能超级电容器

在水热条件下一步自组装合成系列同构X-MOF （X₆O （TATB）₄（H⁺）₂·（H₂O）₈·（DMF）₂,X=Zn、Co、Ni; H₃TATB=4,4'',4″-s-triazine-2,4,6-triyl-tribenzoic acid; DMF=N,N-二甲基甲酰胺）和氧化石墨烯（GO）的复合材料（X-MOF@GO）,并探究其作为超级电容器电极材料的电化学性能。通过X射线粉末衍射、X射线光电子能谱和扫描电子显微镜测试证明GO和MOFs复合成功。其中,性能最优的Ni-MOFs@1.5GO （GO的添加量为1.5 mL）的比电容高达694.8 F·g^-1（0.5 A·g^-1）,约是Ni-MOF的2倍。电化学测试结果表明：复合材料X-MOF@1.0GO较其原MOF表现出更大的比电容和更好的倍率性能。在3.5 A·g^-1的电流密度下,1 000次循环充放电后,Ni-MOFs@1.0GO仍保持初始比电容量的81.2%。与活性炭（AC）组装的非对称超级电容器Ni-MOF@1.5GO//AC的性能最优,其功率密度为754.3 W·kg^-1时,能量密度为15.4 Wh·kg^-1,且循环3 000次后比电容保持率约为70.0%,显示出较长的循环寿命。     

基于热电材料的新型传感器研究进展

传感器作为现代智能工业的核心部件之一,凭借其优良的性能,越来越受到关注.本文总结了热电材料在传感器应用方面的研究成果,特别是硅基、碳基、铅基、碲基、贵金属类、有机类以及催化类的热电材料对传感器高灵敏度、高响应值、高稳定性等方面的影响.已有研究表明,通过在微米纳米尺度合成及加工所形成的低维微纳结构的热电材料,能够获得高ZT值和更高的热电性能.这一特性与传感器微型化方向发展一致.低维微纳结构的热电材料未来必将能够拓展传感器的特性和适用领域,促进传感器朝着高精尖模式的发展.     

A Kinetic Model for Exfoliation Kinetics of Layered Materials

Exfoliation of two‐dimensional materials is key to obtaining high‐performance properties. We present a simple kinetic model for exfoliation that is readily solved analytically. Random and irreversible sheet separation is postulated in the presence of highly effective stabilizers. This model appears to quantitatively fit graphene exfoliation data, and it illuminates mechanistic aspects of exfoliation. Thicker sheets exfoliate much faster than trilayer and bilayer sheets. Exfoliation follows highly activated diffusion‐controlled intercalation of stabilizer into inter‐sheet galleries. Application to the most concentrated graphene exfoliation data available supports these assumptions and provides insight for practical treatment regimens.