Preparation of porous polyimide/in‐situ reduced graphene oxide composite films for electromagnetic interference shielding

Herein we report an easy and efficient approach to prepare lightweight porous polyimide (PI)/reduced graphene oxide (RGO) composite films. First, porous poly (amic acid) (PAA)/graphene oxide (GO) composite films were prepared via non‐solvent induced phase separation (NIPS) process. Afterwards PAA was converted into PI through thermal imidization and simultaneously GO dispersed in PAA matrix was in situ thermally reduced to RGO. The GO undergoing the same thermal treatment process as thermal imidization was characterized with thermogravimetric analysis, Raman spectra, X‐ray photoelectron spectroscopy and X‐ray diffraction to demonstrate that GO was in situ reduced during thermal imidization process. The resultant porous PI/RGO composite film (500‐µm thickness), which was prepared from pristine PAA/GO composite with 8 wt% GO, exhibited effective electrical conductivity of 0.015 S m^?1 and excellent specific shielding efficiency value of 693 dB cm² g^?1. In addition, the thermal stability of the porous PI/RGO composite films was also dramatically enhanced. Compared with that of porous PI film, the 5% weight loss temperature of the composite film mentioned above was improved from 525°C to 538°C. Moreover, tensile test showed that the composite film mentioned above possessed a tensile strength of 6.97 MPa and Young's modulus of 545 MPa, respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了269.33 F·g^-1和350.13 F·cm^-3的高质量和体积比电容,并在10.0 A·g^-1时仍能达到215.88 F·g^-1和280.62 F·cm^-3(其初始值的80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了 269.33 F·g^-1和 350.13 F·cm^-3的高质量和体积比电容,并在 10.0 A·g^-1时仍能达到 215.88 F·g^-1和 280.62 F·cm^-3(其初始值的 80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和 12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

Synthesis of iron oxide cubes/reduced graphene oxide composite and its enhanced lithium storage performance

Fe₃O₄ is considered as a promising electrode material for lithium-ion batteries(LIBs) due to its low cost and high theoretical capacity(928 mAh/g).Nevertheless,the huge volume expansion and poor conductivity seriously hamper its practical applications.In this study,we use a facile hydrothermal reaction together with a post heat treatment to construct the three-dimensional heterostructured composite(Fe₃O₄/rGO) inwhich reduced graphene oxide sheets wraped the Fe₃O₄ submicron cubes as the conductive network.The electric conduction and electrode kinetics of lithium ion insertion/extraction reaction of the composite is enhanced due to the assist of conductive rGO,and thus the Listorage performance is obviously improved.The composite exhibits a reversible charge capacity of772.1 mAh/g at the current density of 0.1 A/g,and the capacity retention reaches 70.3% after400 cycles at0.5 A/g,demonstrating obviously higher specific capacity and rate capability over the Fe₃O₄ submicron cubes without rGO,and much superior cycling stability to the parent Fe_2 O_3 submicron cubes without rGO.On the other hand,as a synergic conductive carbon support,the flexible rGO plays an important role in buffering the large volume change during the repeated discharge/charge cycling.     

Self-assembled reduced graphene oxide/sulfur composite encapsulated by polyaniline for enhanced electrochemistry performance

Reduced graphene oxide/sulfur/polyaniline (referred to RGO/S/PANI) composite was self-assembled through in situ synthesis and used to investigate the electrochemical properties of lithium/sulfur cells. The RGO/S/PANI composite possessed 809.3/801.9 mAh g^?1 of initial charge/discharge capacities, higher than 588.3/588.2 mAh g^?1 for reduced graphene oxide/sulfur (referred to RGO/S) and 681.4/669.9 mAh g^?1 for sulfur/polyaniline (referred to S/PANI) at similar conditions. The RGO/S/PANI composite obtained 400 mAh g^?1 at 2 C and good reversible capacities of 605.5 and 600.8 mAh g^?1 at 100th charge/discharge cycle at 0.1 C, in comparison with low electrochemical performance of RGO/S and S/PANI. The improved properties could be attributed to the collaboration of RGO and PANI. Co-generation of RGO and sulfur acted as seeds for their depositions, stimulated their uniform distributions, and restricted the agglomeration of sulfur particles in situ synthesis. Polyaniline coated RGO/S and stabilized the nanostructure of RGO/S/PANI in repeated charge/discharge cycles. In addition, RGO and PANI provided many electron channels to enhance sulfur conductivity and sufficient void space for sulfur swelling during charge/discharge cycles.     

Efficient removal of chlorophenols from water with a magnetic reduced graphene oxide composite

A magnetic reduced graphene oxide composite (MRGO) was successfully prepared by a simple and green method. MRGO was then used as an adsorbent and found to exhibit enhanced removal efficiency for various chlorophenols (CPs) from water compared with its precursors, graphene oxide (GO) and reduced graphene oxide. The CPs were o-chlorophenol, p-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. Among them, 2,4,6-trichlorophenol, which exhibited the lowest water solubility and highest molecular weight, most easily bound to MRGO. The preferential interactions between MRGO and CPs were hydrophobic interactions (π-π stacking and hydrophobic effect). This result was confirmed by the equilibrium adsorption behavior in which isotherms were all well described by Freudlich model, indicating heterogeneous and multilayer adsorption. Therefore, CP adsorption was more favored under neutral and acidic conditions, and the decreased removal efficiency of MRGO at higher pH levels was due to the improved hydrophilicity of CPs for deprotonation effect. Moreover, MRGO showed fast removal of each CP, achieving adsorption equilibrium within 10.0 min, presented efficient separation from water under an external magnetic field, and was easily regenerated using dilute NaOH aqueous solution after reaching saturated adsorption. Adsorption capacity of the regenerated MRGO had almost no loss until after five cycles. In summary, MRGO was an efficient adsorbent for the removal of various CPs and had considerable application potential in water treatment.     

Oxygen doping modulating thermal-activated charge transport of reduced graphene oxide for high performance temperature sensors

Graphene and its derivatives have sparked intense research interest in wearable temperature sensing due to their excellent electric properties, mechanical flexibility, and good biocompatibility. Despite these advantages, the weak temperature dependence of charge transport makes them difficult to achieve a highly sensitive temperature response, which is one of the remaining bottlenecks in the progress towards practical applications. Unfortunately, detailed knowledge about the key factors of the charge transport temperature dependence in this material that determines the critical performance of electrical sensors is very limited up to now. Here, we reveal that oxygen absorption on the ultrathin reduced graphene oxide (RGO) films (∼3 nm) can significantly increase their conductance activation energy over 200% and thus greatly improve the temperature dependence of thermal-activated charge transport. Further investigations suggest that oxygen introduces the deep acceptor states, distributed at an energy level ∼0.175 eV from the valence-band maximum, which allows a highly temperature-dependent impurity ionization process and the resulting vast holes release in a wide temperature range. Remarkably, our temperature sensors based on oxygen-doped ultrathin RGO films show a high sensitivity with temperature conductive coefficient of 14.58% K⁻¹, which is one order of magnitude higher than the reported CNT or graphene-based devices. Moreover, the ultrathin thickness and high thermal conductivity of RGO film allow an ultrafast response time of ∼86 ms, which represents the best level of temperature sensors based on soft materials. Profiting from these advantages, our sensors show good capacity to identify the slight temperature difference of human body, monitor respiratory rate, and detect the environmental temperature. This work not only represents substantial performance advances in temperature sensing, but also provides a new approach to modulate the charge transport temperature dependence, which could be benefited to both device design and fundamental research.     

A nickel oxide nanoflakes/reduced graphene oxide composite and its high-performance lithium-storage properties

Journal of Solid State Electrochemistry - Since conventional graphite-based anode possesses a low capacity, seeking for high-capacity anode candidates becomes significant for constructing emerging...     

Defluoridation in aqueous solution by a composite of reduced graphene oxide decorated with cuprous oxide via sonochemical

The World Health Organization (WHO) has recommended the fluoride level in drinking water (1.5 mg/L) and defluoridation of water is an essential to remove of fluoride from contaminated water. Hence, the effective and rapid adsorbent Cuprous oxide-reduced graphene oxide (Cu₂O-RGO) composite was developed to overwhelm this concern. Sonochemical approach was adopted for the synthesis of desirable composite which was further characterized by XRD, FTIR, SEM, and EDS. The optimized composite (30 mg) shown the significant adsorption capacity of 34 mg/g of F⁻ solution (pH = 9), 70% removal of F⁻ solution from real experiment and Freundlich model was fitted than Langmuir and Temkin isotherms. The experimental results corroborate that adsorbent is the most effective for removal of fluoride from its polluted water.     

石墨烯/还原氧化石墨烯/聚苯胺复合材料的制备及在超级电容器中的应用

本研究以低成本、易规模化的亲水性石墨烯/氧化石墨烯为前驱体,通过原位聚合的方法制备石墨烯/氧化石墨烯/聚苯胺复合材料,经过化学还原后制备得到石墨烯/还原氧化石墨烯/聚苯胺复合材料.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和傅里叶红外变化光谱仪(FT-IR)对制备的材料进行了结构和形貌的表征.运用循环伏安法...     

Facile synthesis of polyaniline/TiO2/graphene oxide composite for high performance supercapacitors

The polyaniline/TiO₂/graphene oxide (PANI/TiO₂/GO) composite, as a novel supercapacitor material, is synthesized by in situ hydrolyzation of tetrabutyl titanate and polymerization of aniline monomer in the presence of graphene oxide. The morphology, composition and structure of the composites as-obtained are characterized by SEM, TEM, XRD and TGA. The electrochemical property and impedance of the composites are studied by cyclic voltammetry and Nyquist plot, respectively. The results show that the introduction of the GO and TiO₂ enhanced the electrode conductivity and stability, and then improved the supercapacitive behavior of PANI/TiO₂/GO composite. Significantly, the electrochemical measurement results show that the PANI/TiO₂/GO composite has a high specific capacitance (1020 F g⁻¹ at 2 mV s⁻¹, 430 F g⁻¹ at 1 A g⁻¹) and long cycle life (over 1000 times).     

Ultrasmall reduced graphene oxide with high near-infrared absorbance for photothermal therapy

We developed nanosized, reduced graphene oxide (nano-rGO) sheets with high near-infrared (NIR) light absorbance and biocompatibility for potential photothermal therapy. The single-layered nano-rGO sheets were ～20 nm in average lateral dimension, functionalized noncovalently by amphiphilic PEGylated polymer chains to render stability in biological solutions and exhibited 6-fold higher NIR absorption than nonreduced, covalently PEGylated nano-GO. Attaching a targeting peptide bearing the Arg-Gly-Asp (RGD) motif to nano-rGO afforded selective cellular uptake in U87MG cancer cells and highly effective photoablation of cells in vitro. In the absence of any NIR irradiation, nano-rGO exhibited little toxicity in vitro at concentrations well above the doses needed for photothermal heating. This work established nano-rGO as a novel photothermal agent due to its small size, high photothermal efficiency, and low cost as compared to other NIR photothermal agents including gold nanomaterials and carbon nanotubes.     

A novel octadecylsilane functionalized graphene oxide/silica composite stationary phase for high performance liquid chromatography

An octadecylsilane functionalized graphene oxide/silica stationary phase was fabricated by assembling graphene oxide onto the silica particles through an amide bond and subsequent immobilization of octadecylsilane. The chromatographic properties of the stationary phase were investigated by reversed-phase chromatography with alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenolic compounds as the analytes. All the compounds achieved good separation on the column. The comparison between a C18 commercial column and the new stationary phase indicated that the existence of π-electron system of graphene oxide allows π-π interaction between analyte and octadecylsilane functionalized graphene oxide/silica stationary phase except for hydrophobic interaction, while only hydrophobic interaction presented between analyte and C18 commercial column. This suggests that some analytes can be better separated on the octadecylsilane functionalized graphene oxide/silica column.     

三维二硫化钼/还原氧化石墨烯气凝胶用作宏观可见光催化剂

近年来,光催化技术在解决环境污染和能源短缺方面展现出巨大潜力.二硫化钼(MoS2)作为一种二维层状光催化材料受到广泛关注.MoS2具有可调的带隙(1.2–1.9 eV)、低的成本和高的存储量,是一种可替代铂的理想助催化剂.然而,MoS2本身光催化活性较低.理论和实验已经证明,MoS2只有暴露的边缘具有催化活性,并且MoS2的光生电子-空穴对容易复合,导致其光催化效率低.增加暴露的活性边缘以及有效分离电子-空穴对是提高MoS2光催化活性的关键.而石墨烯气凝胶是一种理想的催化剂载体,其高比表面积和高空隙率可以有效提高催化剂利用率.同时,其高导电性可以促进光生电子-空穴对分离.因此,将MoS2负载到石墨烯气凝胶上制备宏观可回收光催化材料具有广阔的应用前景.然而,目前尚未见到有关MoS2/石墨烯气凝胶光催化产氢以及还原Cr(VI)的报道.本文以钼酸铵为钼源,硫脲为硫源和还原剂,同时加入氧化石墨烯及其还原剂氨水,通过一步水热法制备出二硫化钼/还原氧化石墨烯(MoS2/RGO)水凝胶.最后通过冷冻干燥得到MoS2/RGO气凝胶.经光催化测试发现其产氢达到38.9μmol/g,光还原Cr(VI)达到92%,明显高于MoS2粉体.采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)、紫外-可见-近红外吸收光谱(UV-Vis-NIR)及红外光谱(FTIR)等手段研究了其光催化性能提高的原因.XRD测试显示,过量的NH4+离子插入到MoS2层与层之间增加了(002)面的晶面间距;SEM观察到在形成气凝胶后,MoS2从粉末的片状转变成花状,这是因为氧化石墨烯上的含氧官能团促进MoS2成核同时限制其生长导致的;TEM观察到MoS2上存在大量的脱节和扭曲,这是由于过量硫脲阻碍了MoS2晶体的取向生长而产生缺陷;XPS发现,除了形成MoS2之外,还形成了MoO2,同时大量的暴露边缘导致不饱和硫产生;FTIR表明MoS2与RGO之间通过氢键链接在一起;UV-Vis-NIR吸收光谱显示,MoS2/RGO气凝胶在可见光区具有很强的吸收,这是黑色的RGO以及光在花状结构的不断反射共同作用导致的.综合以上结果,我们提出了MoS2/RGO光催化性能增强的机理.首先,三维的气凝胶网状结构以及花状结构的MoS2所带来的高比表面积(599.7 m2/g)使得材料对H+和Cr(VI)吸附量增加;其次,黑色的RGO以及入射光在花状结构层片间的不断反射增加了MoS2/RGO气凝胶对可见光的吸收;最后,RGO本身的高导电性促进了光生电子-空穴有效分离,电子通过RGO快速转移到材料表面参与光催化反应.因此,将MoS2负载在RGO上可提高光催化效率.另外,低密度的MoS2/RGO气凝胶(56.1 mg/cm3)可以有效吸附有机溶剂且容易回收.综上所述,本文制备的MoS2/RGO气凝胶光催化材料在环境与能源方面表现出潜在的应用前景.     

Biocompatible reduced graphene oxide prepared by using dextran as a multifunctional reducing agent

A large-scale, cost-effective, and environmentally friendly synthetic strategy for biocompatible reduced graphene oxide (RGO) by using dextran as a reducing and stabilization agent has been developed. Dextran-coated RGO (D-RGO) was readily soluble in water with high biocompatibility.     

Transition metal ions-doped polyaniline/graphene oxide nanostructure as high performance electrode for supercapacitor applications

Journal of Solid State Electrochemistry - Polyaniline/graphene oxide (PANI/GO) co-doped with Zn2+ and Fe3+ was synthesized via a simple and low cost one-step chronoamperometry method on stainless...     

Dopamine sensor based on a glassy carbon electrode modified with a reduced graphene oxide and palladium nanoparticles composite

We report on a sensitive electrochemical sensor for dopamine (DA) based on a glassy carbon electrode that was modified with a nanocomposite containing electrochemically reduced graphene oxide (RGO) and palladium nanoparticles (Pd-NPs). The composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical impendence spectroscopy. The electrode can oxidize DA at lower potential (234 mV vs Ag/AgCl) than electrodes modified with RGO or Pd-NPs only. The response of the sensor to DA is linear in the 1–150 μM concentration range, and the detection limit is 0.233 μM. The sensor was applied to the determination of DA in commercial DA injection solutions.

Freestanding reduced graphene oxide/sodium vanadate composite films for flexible aqueous zinc-ion batteries

With the booming development of portable and wearable electronic devices, flexible energy storage devices have attracted great attention. Among various energy storage devices, aqueous zinc ion batteries(ZIBs) are one of the promising candidates due to their low cost, good safety, high energy and power densities. However, the conventional cathodes of aqueous ZIBs were often prepared by mixing active materials with binders and conductive additives and then coating them onto current collectors. The resultant cathodes often suffer from unsatisfied flexibility. Herein, we fabricated freestanding reduced graphene oxide/NaV_3O_8·1.5H_2O(RGO/NVO) composite films with interlinked multilayered architecture by a vacuum filtrating process. Such composite films exhibit excellent mechanical property and high electronic conductivity. Owing to unique architecture, they display a high capacity of 410 mA h g~(-1) and excellent cycling performance up to 2000 cycles with a high capacity retention of 94%. Moreover, RGO/NVO composite films can directly serve as the cathodes of flexible aqueous ZIBs. As a proof of concept,flexible ZIBs were assembled based on the composite films. Impressively, they exhibit stable performance at different bending states, demonstrating great potential application in flexible energy storage devices.     

Mechanically flexible reduced graphene oxide/carbon composite films for high-performance quasi-solid-state lithium-ion capacitors

Practical applications of diverse flexible wearable electronics require electrochemical energy storage(EES) devices with multiple configurations. Moreover, to fabricate flexible EES devices with high energy density and stability, organic integration from electrode design to device assembly is required. To address these challenges, a free-standing reduced graphene oxide(rGO)/carbon film with a unique sandwich structure has been designed via the assistance of vacuum-assistant filtration for lithiu...