Electrografting of amino-TEMPO on graphene oxide and electrochemically reduced graphene oxide for electrocatalytic applications

4-Amino-2,2,6,6-tetramethyl-1-piperridine N-oxyl (4-amino-TEMPO), an electroactive nitroxide radical, was attached to the surface of graphene oxide (GO) and electrochemically reduced graphene oxide (ERGO) modified glassy carbon electrode by a simple, rapid and green electrografting method. The electroactive interfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The calculated surface coverage for 4-amino-TEMPO is up to 1.55 × 10^− 9 mol·cm^− 2. The modified electroactive interface exhibited excellent electrocatalytic activity towards the electro-oxidation of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂).     

Ultrasonic route synthesis,characterization and electrochemical study of graphene oxide and reduced graphene oxide

Research on Chemical Intermediates - In this study, an efficient route for graphene oxide (GO) and reduced GO (RGO) synthesis was developed by using an ultrasonic probe and bath alternatively. RGO...     

Capillary zone electrophoresis of graphene oxide and chemically converted graphene

The preparation of processable graphene oxide colloids called chemically converted graphene (CCG) involves the following steps: oxidation of graphite to form graphite oxide; exfoliation of graphite oxide to form graphene oxide (GO); and reduction of GO to form CCG. In this work, the exfoliation and reduction steps were monitored by capillary zone electrophoresis (CZE). CZE was performed in fused silica capillaries with UV absorbance at 230 nm (GO) and 270 nm (CCG) using 250 μM tetrapropylammonium hydroxide (pH 10.4). The results indicate that almost complete exfoliation of graphite oxide (0.05 wt%) and higher recovery of CCG were obtained by sonication at 50% power for more than 15 h. CZE is considered a valuable tool for the fractionation and analysis of GO nanoparticles and, hence, for the control of different steps in preparation of CCG.     

氧化石墨烯和石墨烯在催化领域中的应用研究进展

石墨烯具有独特的二维平面结构,其导电性能好,比表面积大,耐酸碱,耐高温.基于石墨烯的优异特性,本文作者从材料的合成和结构等方面对石墨烯基催化剂的研制及其催化性能进行了评述.介绍了石墨烯催化体系的类型和机理,对石墨烯催化中存在的问题进行了简单分析,并对石墨烯在催化领域的应用前景进行了展望.     

Controlling wrinkles and assembly patterns in dried graphene oxide films using lyotropic graphene oxide liquid crystals

We fabricated graphene oxide (GO) films on glass substrates by blade coating a lyotropic GO liquid crystal dispersion. Substrate temperature and blading speed were precisely controlled to manipulate the surface morphologies of GO films. The temperature and blade speed influenced the drying rate of film and the amount GO dispersion supplied. By controlling these parameters, film-thickness modulation and three types of surface wrinkle patterns were selectively achieved. We also plotted the wrinkle patterns diagram as functions of the film fabrication conditions. The films exhibited different optical anisotropies depending on wrinkle patterns. GO films with controlled wrinkles can be used as electrodes for supercapacitor applications owing to the large surface areas.     

Features of the reduction of graphene from graphene oxide

Features of the reduction of graphene from graphene oxide in media containing hydrazine hydrate, ethylene glycol, and hydrogen are studied. X-ray energy dispersive spectroscopy, Raman spectroscopy, and scanning electron microscopy data indicate that this process proceeds through the high-temperature annealing of graphene oxide in a hydrogen environment.     

High-performance graphene oxide electromechanical actuators

Having demonstrated unparalleled actuation stresses and strains, covalently bonded carbon-based nanomaterials are emerging as the actuators of the future. To exploit their full potential, further investigations into the optimum configurations of these new materials are essential. Using first-principle density functional calculations, we examine so-called clamped and unzipped graphene oxide (GO) as potential electromechanical actuator materials. Very high strains are predicted for hole injection into GO, with reversible and irreversible values of up to 6.3% and 28.2%, respectively. The huge 28% irreversible strain is shown to be the result of a change in the atomic structure of GO from a metastable clamped to more stable unzipped configuration. Significantly, this strain generation mechanism makes it possible to hold a constant strain of 23.8% upon removal of the input power, making this material ideal for long-term, low-power switching applications. A unique contraction of unzipped GO upon electron injection is also observed. It is shown that the origin of this unique behavior is the modulation of the structural rippling effect, which is a characteristic feature of GO. With reversible strains and stresses in excess of 5% and 100 GPa, respectively, GO is poised to be an extremely useful material for micro/nanoelectromechanical system actuators.     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

功能化的石墨烯和磁铁掺杂的还原氧化石墨烯对亚甲基蓝的吸附作用

用简单可行的方法合成了功能化的石墨烯(GNSPF6)和磁铁掺杂的还原氧化石墨烯(RGO-Fe3O4),并进一步研究了pH值、接触的时间和温度对它们吸附亚甲基蓝(MB)的影响.结果表明,随着pH值和温度的增加其吸附量也随之变大,从而说明该吸附过程是自发吸热的.因为GNSPF6的吸附过程只用了不到20min的时间,所以它的吸附是高效的.用经典的准一级反应、准二级反应和粒内扩散模型对其吸附过程进行动态分析,从结果可以发现,准二级动力学模型比准一级动力学模型更适用于描述吸附过程.采用传统的Langmuir,Freundlich和L-F吸附等温线模型来模拟分析数据,在20℃时,由Langmuir吸附等温线模型模拟分析得知GNSPF6和RGO-Fe3O4对MB的最大吸附量分别为374.4和118.4mg/g.     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

Photochemical processes in graphene oxide films

Experimentally revealed features of thermal and photochemical deoxidation of graphene oxide (GO) in films are reported. A difference in mechanism between the photoreduction and thermal reduction of GO has been shown. The mechanism of photochemical deoxidation of graphene oxide has been rationalized using the concepts of molecular photochemistry. A new model of photoelimination of molecular oxygen from epoxy groups on graphene nanosheet has been proposed. The photoprocesses lead to growing of π-domains of graphene.     

Fluorescent sensors using DNA-functionalized graphene oxide

In the past few years, graphene oxide (GO) has emerged as a unique platform for developing DNA-based biosensors, given the DNA adsorption and fluorescence-quenching properties of GO. Adsorbed DNA probes can be desorbed from the GO surface in the presence of target analytes, producing a fluorescence signal. In addition to this initial design, many other strategies have been reported, including the use of aptamers, molecular beacons, and DNAzymes as probes, label-free detection, utilization of the intrinsic fluorescence of GO, and the application of covalently linked DNA probes. The potential applications of DNA-functionalized GO range from environmental monitoring and cell imaging to biomedical diagnosis. In this review, we first summarize the fundamental surface interactions between DNA and GO and the related fluorescence-quenching mechanism. Following that, the various sensor design strategies are critically compared. Problems that must be overcome before this technology can reach its full potential are described, and a few future directions are also discussed.     

Geometry-dependent electrochemistry of graphene oxide family

The influence of graphene oxide geometry on electrochemical performance is of great interest, but there are few reports on this subject. Three different members of the graphene oxide family, graphene oxide nanosheets, graphene oxide nanoribbons, and graphene oxide quantum dots were comparatively investigated as electrode materials to systematically study the effect of geometric structure. The results showed that, as the geometric structure varies, the three graphene oxide materials possess different electrical conductivities, various defect densities and oxygen contents, as well as diverse electrode surface chemistry and microstructures, which combine together to result in the distinct electrochemical responses for the modified electrodes, depending on the redox system involved. This work broadens the method of studying the electrochemical performance of many other materials from the perspective of geometry.     

Electrochromatographic performance of graphene and graphene oxide modified silica particles packed capillary columns

Graphene oxide functionalized silica microspheres (GO@SiO₂) were synthesized based on condensation reaction between amino from aminosilica particles and carboxyl groups from GO. Reduction of GO@SiO₂ with hydrazinium hydroxide generated graphene modified silica particles (G@SiO₂). GO@SiO₂ and G@SiO₂ packed capillary columns for capillary electrochromatography were thereafter fabricated by pressure slurry packing with single‐particle frits. GO of 0.3 mg/mL in dispersion solution for GO@SiO₂ synthesis was considered as a compromise between retaining and column efficiency whereas GO@SiO₂ of 20 mg/mL in slurries for column packing was chosen for a homogenous and tight bed. Optimum mobile phases were acquired considering both electroosmotic flow and resolution at an applied voltage of −6 kV as the following: acetonitrile/phosphate buffer (10 mM, pH 7.0), 75:25 (v/v) for polycyclic aromatic hydrocarbons and 50:50 (v/v) for aromatic compounds. A comparison was made between electrochromatographic performances for three PAHs (naphthalene, fluorene and phenanthrene) and three aromatic compounds of various polarities (toluene, aniline and phenol) on bare aminosilica, GO@SiO₂ and G@SiO₂ packed columns, which proved the contribution of alone or combinational actions of solvophobic effect and π‐π electron stacking as well as hydrogen bonds to retaining behaviors by GO@SiO₂ and G@SiO₂. Well over‐run, over‐day and over‐column precisions (retention time: 0.3–1.4, 1.1–3.8 and 2.8–5.2%, respectively; peak area: 2.6–6.5, 4.8–8.3 and 6.5–12.6%, respectively) of GO@SiO₂ packed columns were a powerful proof for good reproducibility. Analytical characteristics of GO@SiO₂ packed capillary columns in CEC analysis of fresh water were evaluated with respect to linearity (R² = 0.9961–0.9989) over the range 0.1 to 100 mg/L and detection limits of 9.5 for naphthalene, 12.6 for fluorene and 16.2 μg/L for phenanthrene. Further application to fresh water increased the visibility of the proposed material, where good spike recoveries in the range 89–96% were offered.     

DNA adsorbed on graphene and graphene oxide: Fundamental interactions,desorption and applications

Interfacing DNA oligonucleotides with graphene-based materials, especially graphene oxide, has produced many new sensors and devices. Since graphene oxide is an excellent fluorescence quencher, fluorescently labeled DNAs (probes) are nearly fully quenched upon adsorption. Addition of the complementary DNA results in probe desorption and fluorescence enhancement. Aside from its analytical applications, this system provides a fascinating topic for biointerface science. DNA can be adsorbed by graphene oxide via π–π stacking and hydrogen bonding, while it must overcome electrostatic repulsion at the same time. The mechanism of DNA-induced probe desorption has also been a topic of extensive discussion. In this article, DNA adsorption and desorption reactions and interactions with graphene oxide and related materials (e.g. graphene) are reviewed based on the current understandings. A few representative applications based on these processes are also described briefly.     

氧化石墨烯的制备及低温还原研究

用化学氧化法制备氧化石墨烯,并用一种新型的低温化学还原方法将其还原。用红外光谱、拉曼光谱、X射线衍射、X射线光电子能谱、扫描电镜、原子力显微镜等多种手段表征氧化石墨烯和还原氧化石墨烯的结构与形貌。结果表明,即使在低温条件下,壳聚糖依然可以还原氧化石墨烯,从而预示,在低温条件下,能够在同一环境下实现氧化石墨烯的还原和石墨烯的应用。     

Protein-directed reduction of graphene oxide and intracellular imaging

We demonstrate a facile, one-step, protein-directed approach to preparing a new functional reduced graphene oxide via simultaneous reduction and surface functionalization of graphene oxide sheets with herceptin and show its potential application as a novel biological imaging agent.     

改性氧化石墨烯膜的制备及其性能研究

为了改善氧化石墨烯(GO)膜的低渗透性和不稳定性,本文采用过氧化氢对GO进行改性后抽滤成膜,并在不同温度下对膜进行热还原。采用超高性能全自动气体吸附仪、透射电镜、扫描电镜、拉曼光谱仪、接触角、X射线衍射等对材料进行结构和形貌表征。分析不同HGO(H_2O_2改性GO)负载量和不同温度热还原对膜水通量和截留率的影响。在优化条件(1mg HGO负载量、120℃还原温度)下制备的膜的水通量(397.8L·m~(-2)·h~(-1)·bar~(-1))和截留率(90%)达到最佳;并且,热还原之后的HGO膜比GO膜和HGO膜有更好的稳定性。