Preparation of ce(IV)-O and Ce(IV)-La-O containing nanolayers on the silica surface by ionic layering

The growth kinetics of Ce(IV)-O-containing layers produced by ionic layering were studied as a function of the concentration and pH of the reaction solutions and rinsing liquids, process duration, and number of layering cycles. Conditions were established for the formation of nanolayers through chemical reactions in the adsorption layer. The layers were characterized by UV/visible and Fourier-transform IR spectroscopies, xray photoelectron spectroscopy, chemical analysis, and ellipsometry. The results indicate the formation of cerium(IV) hydroperoxide layers. The layer thickness can be controlled to within 1 nm by adjusting the number of layering cycles. The effect of heating in air on the composition of the layers was examined. Using the same conditions as in the synthesis of the Ce(IV)-O-containing layers, Ce(IV)-La-O-containing layers were synthesized.     

Enhanced graphitic domains of unreduced graphene oxide and the interplay of hydration behaviour and catalytic activity

Previous studies indicate that the properties of graphene oxide (GO) can be significantly improved by enhancing its graphitic domain size through thermal diffusion and clustering of functional groups. Remarkably, this transition takes place below the decomposition temperature of the functional groups and thus allows fine tuning of graphitic domains without compromising with the functionality of GO. By studying the transformation of GO under mild thermal treatment, we directly observe this size enhancement of graphitic domains from originally ≤40 nm² to >200 nm² through an extensive transmission electron microscopy (TEM) study. Additionally, we confirm the integrity of the functional groups during this process by a comprehensive chemical analysis. A closer look into the process confirms the theoretical predicted relevance for the room temperature stability of GO and the development of the composition of functional groups is explained with reaction pathways from theoretical calculations. We further investigate the influence of enlarged graphitic domains on the hydration behaviour of GO and the catalytic performance of single atom catalysts supported by GO. Additionally, we show that the sheet resistance of GO is reduced by several orders of magnitude during the mild thermal annealing process.     

A new “fluoride” synthesis route for successive ionic layer deposition of the ZnxZr(OH)yFz·nH2O nanolayers

It was for the fist time shown that hydroxo-fluoride nanolayers with the general formula M_xZr(OH)_yF_z·nH₂O can be synthesized by the successive ionic layer deposition method using soluble complexes of metal fluorides as reagents. By an example of the Zn_xZr(OH)_yF_z·nH₂O nanolayers on silicon surfaces, the effect of pH, the reagent concentration, and the number of the deposition cycles was examined. The composition and structure of these layers were determined by X-ray photoelectron and FTIR transmission spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), while the growth kinetics was evaluated by ellipsometry.     

Highly wrinkled cross-linked graphene oxide membranes for biological and charge-storage applications

Inspired by the amphiphilicity of graphene oxide (GO), the surface of water is used as a template for the assembly of a GO film. Methacrylate-functionalized GO sheets can be cross-linked instantaneously at the water-air interface to form a highly wrinkled membrane spreading over an extended area. The multiple covalent linkages amongst the GO sheets enhances the in-plane stiffness of the film compared to noncovalently bonded GO films. The highly convoluted GO membrane can be used in two applications: the promoting of spontaneous stem-cell differentiation towards bone cell lineage without any chemical inducers, and for supercapacitor electrodes. Due to reduced van der Waals restacking, capacitance values up to 211 F g(-1) can be obtained. The scalable and inexpensive nature of this assembly route enables the engineering of membranes for applications in regenerative medicine and energy-storage devices where secondary structures like nanotopography and porosity are important performance enhancers.     

Layer-by-layer deposition of polyelectrolyte nanolayers on natural fibres: cotton

The layer-by-layer (LbL) deposition of poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) over cotton fibres is reported. Cotton fibres offer unique challenges to the deposition of nanolayers because of their unique cross section as well as the chemical heterogeneity of their surface. Cationic cotton substrates were produced by using 2,3-epoxypropyltrimethylammonium chloride. Attenuated total reflectance FTIR, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were used to validate the presence of the nanolayers as well as to corroborate their self-organized structure. TEM images indicated conformal and uniform coating of the cotton fibres. XPS spectral data were found to be in quantitative agreement with previous published work that studied the LbL deposition of PSS and PAH over synthetic substrates.     

聚丙烯酰胺/氧化石墨纳米复合材料的研究

氧化石墨具有良好的层状结构，其层间具有丰富的官能团，能与有机聚合物形成插层纳米复合材料进而改善材料的性能．采用层离吸收-原位聚合法制备了聚丙烯酰胺／氧化石墨纳米复合材料，并采用XRD、HREM及DSC等对其结构和性能进行了表征。结果表明，聚丙烯酰胺与氧化石墨两者之间存在着较强的相互作用，材料的玻璃化转变温度得到提高，层离吸收-原位聚合法是获得聚丙烯酰胺／氧化石墨层纳米复合材料的有效途径，聚丙烯酰胺在氧化石墨中存在着多种排列方式，不同层间距(1．6nm和2．8nm)的聚丙烯酰胺／氧化石墨纳米复合结构同时存在。     

Intracellular Imaging with a Graphene‐Based Fluorescent Probe

Graphene is an increasingly important nanomaterial that has shown great promise in the area of nanotechnology. In this study, fluorescein‐functionalized graphene oxide (GO) is synthesized via a polyethylene glycol (PEG) bridge and its application in intracellular imaging is explored. GO is an oxide form of graphene that provides an ideal platform to prepare graphene‐based functional nanomaterials via chemical modification. The PEG bridge was introduced to prevent GO‐induced quenching of conjugated fluorescein. The fluorescein–PEG–GO conjugate thus prepared exhibits excellent pH‐tunable fluorescent properties and, more significantly, can be efficiently taken up by cells and serve as a fluorescent nanoprobe for intracellular imaging.     

Preparation and photocatalytic performance of CuO/GO heterojunction nanocomposite

Recently, solar photocatalytic technology has proved to be an effective way to solve the problems of environmental pollution and energy shortage due to its green environmental protection and fast degradation rate. In this paper, a simple microwave hydrothermal method is used to prepare a novel CuO/GO heterojunction composite photocatalyst, and its chemical composition, microstructure, physicochemical properties, photothermal conversion, and photocatalytic properties are studied. The results show that the addition of GO in the CuO/GO nanocomposite photocatalyst not only effectively reduces the agglomeration of CuO nanoparticles but also makes it exhibit better photocatalytic activity than pure nano-CuO. The degradation rate of MB increased by 39.48% at 120 min of light, and as high as 94.1% at 180 min, mainly due to the construction of heterojunction at the interface and the synergistic promotion effect of light and heat. The internal mechanism of light and heat synergistic catalysis is revealed. This paper not only proposes a low-cost and efficient CuO/GO light-heat composite photocatalyst but also provides new ideas for subsequent researchers to design and prepare nanocomposite photocatalysts.

     

石墨烯/氰酸酯-环氧树脂复合材料的制备和性能

为优化石墨烯/氰酸酯(CE)复合材料的制备工艺并提高其韧性,制备了对苯二胺(PPD)功能化的氧化石墨烯(GO-PPD),分别以GO和GO-PPD为添加物,以CE和环氧树脂(质量比为7:3)共混物为基体树脂制备了GO/CE-环氧树脂和GO-PPD/CE-环氧树脂复合材料。采用红外和拉曼光谱表征GO和GO-PPD的结构,并研究了二者在溶剂中的溶解性。GO-PPD在乙醇等低沸点和低毒性的有机溶剂中表现出稳定的溶解性,与GO相比,GO-PPD明显改善了复合材料制备的工艺性。性能研究表明,GO和GO-PPD的加入均会降低基体树脂的固化温度,明显提高其力学性能和热性能,使基体树脂的介电常数和介电损耗显著增大,但仍然基本保持良好的耐湿热性和耐腐蚀性。石墨烯表面的化学性质影响石墨烯/CE-环氧树脂复合材料的综合性能,与GO相比,GO-PPD的加入能更明显提高复合材料的力学性能和耐热性。     

High-resolution separation of graphene oxide by capillary electrophoresis

Separation and purification of graphene oxide (GO) prepared from chemical oxidation of flake graphite and ultrasonication by capillary electrophoresis (CE) was demonstrated. CE showed the ability to provide high-resolution separations of GO fractionations with baseline separation. The GO fractionations after CE were collected for Raman spectroscopy, atomic force microscopy, and transmission electron microscopy characterizations. GO nanoparticles (unexfoliated GO) or stacked GO sheets migrated toward the anode, while the thin-layer GO sheets migrated toward the cathode. Therefore, CE has to be performed twice with a reversed electric field to achieve a full separation of GO. This separation method was suggested to be based on the surface charge of the GO sheets, and a separation model was proposed. This study might be valuable for fabrication of GO or graphene micro- or nanodevices with controlled thickness.     

Composite Microgels Created by Complexation between Polyvinyl Alcohol and Graphene Oxide in Compressed Double‐Emulsion Drops

Microgels, microparticles made of hydrogels, show fast diffusion kinetics and high reconfigurability while maintaining the advantages of hydrogels, being useful for various applications. Here, presented is a new microfluidic strategy for producing polymer‐graphene oxide (GO) composite microgels without chemical cues or a temperature swing for gelation. As a main component of microgels, polymers that are able to form hydrogen bonds, such as polyvinyl alcohol (PVA), are used. In the mixture of PVA and GO, GO is tethered by PVA through hydrogen bonding. When the mixture is rapidly concentrated in the core of double‐emulsion drops by osmotic‐pressure‐driven water pumping, PVA‐tethered GO sheets form a nematic phase with a planar alignment. In addition, the GO sheets are linked by additional hydrogen bonds, leading to a sol–gel transition. Therefore, the PVA–GO composite remains undissolved when it is directly exposed to water by oil‐shell rupture. These composite microgels can be also produced using poly(ethylene oxide) or poly(acrylic acid), instead of PVA. In addition, the microgels can be functionalized by incorporating other polymers in the presence of the hydrogel‐forming polymers. It is shown that the multicomponent microgels made from a mixture of polyacrylamide, PVA, and GO show an excellent adsorption capacity for impurities.     

Janus Graphene Liquid Crystalline Fiber with Tunable Properties Enabled by Ultrafast Flash Reduction

Flash photothermal treatment via Xenon lamp with a broad wavelength spectrum can effectively remove oxygen functionalities and restore sp² domains at graphitic carbon materials. The chemical composition and relevant structure formation of flash reduced graphene oxide liquid crystal (GOLC) fibers are investigated in accordance with flash irradiation conditions. Owing to the spatial controllability of reduction level via anisotropic flash irradiation, the mechanical properties and electrical conductivity of graphene fibers can be delicately counterbalanced to attain desired properties. High sensitivity humidity sensors can be fabricated from the flash reduced fibers demonstrating notably higher sensitivity over the thermally reduced counterparts. This ultrafast flash reduction holds great promise for multidimensional macroscopic GO based structures, enabling a wide range of potential applications, including textile electronics and wearable sensors.     

Effect of a magnetron-sputtered MnO<Subscript>2</Subscript> layer on the thermal oxidation kinetics of InP and the composition and morphology of the resultant films

It has been shown in the process of optimization of approaches to effective control over the formation of functional nanofilms on III–V semiconductors that the surface modification of InP with magnetronsputtered MnO₂ nanolayers (25 nm thick) results in an oxygen transfer mechanism of the thermal oxidation of the semiconductor. The advantages of this approach are a higher rate of the increase in film thickness in comparison with stimulator-free oxidation, rapid chemical binding of indium, blocking of indium diffusion into the film, and accelerated phosphate formation. Changes in the composition of the films in comparison with those produced by stimulator-free oxidation lead to a considerable improvement in their surface quality (the roughness height does not exceed 20 nm and the average grain size is 55 nm).     

The synthesis by successive ionic layer deposition of SnMo0.6Oy·nH2O nanolayers on silica

The conditions for the layer-by-layer synthesis by the method of the successive ionic layer deposition of Sn(IV)Mo(VI,V)_0.6O_y·nH₂O nanolayers on a silica surface were determined for the first time. The nanolayer thickness was controlled by the number of successive cycles. The composition and structure of these films were determined using Fourier transform infrared and UV/Vis transmission spectroscopy, X-ray photoelectron spectroscopy, X-ray difraction, and electron microprobe. It was found that under heating up to 200 °C, molecular water and hydroxyl groups are removed from the nanolayers, the bonds Mo---O---Mo and Sn---O---Mo are formed, and Mo(V) is oxidized to Mo(VI).     

碳纤维-氧化石墨烯/环氧树脂复合材料的制备及表征

采用改进的Hummers法制备了五种具有不同氧化程度的氧化石墨烯（GO）。借助元素分析、X射线光电子能谱及FTIR红外光谱测试对所制备GO的组成及结构衍变进行了表征。利用光学显微镜对不同GO在固化剂异佛尔酮二胺（IPDA）中的分散状态进行观察,并将分散效果最佳的GO试样用于改性碳纤维/环氧树脂（CF/EP）复合材料。结果表明,随着氧化剂用量及反应时间的增加,GO的氧化程度也随之增加。在氧化程度较低时,GO表面官能团主要以羰基、羧基和酚羟基为主。随着氧化程度的不断提高,GO表面官能团主要为醚、环氧和醇羟基结构。GO在IPDA中的分散状态与其氧化程度密切相关,氧化程度最低和最高的GO均出现明显的聚集现象。另外,GO表面在分散过程中可被IPDA化学改性。在EP基体中加入分散效果最佳的GO（0.2wt%）后,与CF/EP复合材料相比,CF-GO/EP复合材料的弯曲强度、层间剪切强度和Ⅱ型层间断裂韧性分别提高了14%、17%和14%。     

Preparation and chemical reduction of laurylamine-intercalated graphite oxide

Laurylamine-intercalated graphite oxide (GO) is prepared by ultrasonic in the presence of a small amount of hexane and then chemically reduced by hydrazine. The interlayer spacing of laurylamine-intercalated GO reaches a maximum when the molar ratio of laurylamine and GO is 1.384. Three types of laurylamine in GO are identified in the intercalated compounds: hydrogen-bonded neutral amines, hydrogen-bonded protonated amines, and ionically bound protonated amines. Modified graphene colloidal suspension is obtained by chemical reduction of laurylamine-intercalated GO in dimethyl formamide (DMF). Furthermore, a possible chemical reduction mechanism is put forward to explain the hydrazine reduction process.     

Chemically Derived Graphene Oxide: Towards Large‐Area Thin‐Film Electronics and Optoelectronics

Chemically derived graphene oxide (GO) possesses a unique set of properties arising from oxygen functional groups that are introduced during chemical exfoliation of graphite. Large‐area thin‐film deposition of GO, enabled by its solubility in a variety of solvents, offers a route towards GO‐based thin‐film electronics and optoelectronics. The electrical and optical properties of GO are strongly dependent on its chemical and atomic structure and are tunable over a wide range via chemical engineering. In this Review, the fundamental structure and properties of GO‐based thin films are discussed in relation to their potential applications in electronics and optoelectronics.     

氧化石墨烯/H2O2可见光催化性能影响因素

为了研究氧化石墨烯/H₂O₂可见光催化处理含难降解有机物废水影响因素,用改进的Hummers法制备了氧化石墨烯(GO),通过扫描电镜(SEM)、电子能谱(EDS)、拉曼光谱对GO的微观形貌、成分及结构进行了表征.以甲基橙(MO)为难降解有机物代表,通过改变光照、pH值以及GO的量探究了不同条件对GO/H₂O₂复合试剂降解甲基橙的光催化效果.研究表明：GO/H₂O₂复合试剂可以通过光催化产生羟基自由基降解污染物,通过改变光照、pH值及GO的量增加自由基含量可提升催化效果; 采用GO/H₂O₂复合试剂比单独使用H₂O₂在48 h内对甲基橙的降解率可提高79.09%(pH=2).用改良的Hummers法制备GO成本较低,采用GO/H₂O₂复合试剂光催化降解甲基橙时,GO用量较少,且不产生危险废弃物,为实际应用中处理难降解有机物污水提供了一个绿色环保、节能高效的思路.     

Interfacial,fire retardancy,and thermal stability evaluation of graphite oxide (GO)-phenolic composites with different GO particle sizes

Mechanical and thermal properties of graphite oxide (GO)-phenolic composites were evaluated for different sizes of GO. Tensile tests on the composites with larger sizes of GO particles typically exhibited better mechanical properties. After ageing tests at 200 °C a decline in the mechanical properties of GO-phenolic composites was observed but this decline was less than that for neat phenolic resin. This was attributed to the GO absorbing thermal energy and thereby reducing damage to the molecular chain in the resin. The ageing tests, also suggested that the wettability of specimens improved with the addition of GO, which might be attributed to microvoid formation on specimen’s surface during the elapsed time at the elevated temperature. The chemical structures of neat phenolic resin was relatively easily broken-up by thermal damage, whereas GO-phenolic composites exhibited better thermal stability in both thermal analysis and flame retardant testing. The GO particles exhibited reinforcing effects that served to protect chemical bonding in the phenolic resin. It appears, therefore, that GO composites may be good candidates for us as heat and flame resisting materials, for various applications.     

Nanoscale Multilayered ZrAlN/ZrB2 Coatings Synthesized by Magnetron Sputtering

Multilayered ZrAlN/ZrB2 coatings containing alternating bilayer periods were synthesized by dc magnetron sputtering technique. The intensities of ZrN （111） or ZrN （200） textures in the structure of the nanolayers depended on the bilayer period as well as N2 gas partial pressure during deposition. Nanoindentation testing showed that hardness and internal stress of the nanolayers varied with the bilayer period and crystallographic orientation in the coatings. The hardness of the nanolayers with bilayer periods of 3-6 nm was enhanced （-27%） over the rule-of-mixture value. A low percent of N2 in processing gas was proved to be benefitial to the synthesis of high hard nanoscale multilayered coatings.