N掺杂石墨烯负载Pt-Sn催化剂的制备及电催化性能研究

氮掺杂石墨烯负载Pt在直接乙醇燃料电池（DEFCs）中表现出较好的性能。Pt的高成本极大地限制了DEFCs的商业化应用。因此,采用一系列不同浓度水合肼还原氧化石墨烯的简单方法,合成了氮掺杂石墨烯负载Pt-Sn （Pt-Sn/G-N）。研究了Pt-Sn/G-N催化剂纳米粒子的均匀分散对乙醇氧化的电催化活性影响。通过控制不同的氮含量,进一步研究了Pt和Sn金属颗粒最适宜协同效应的比例。结果表明：当氧化石墨烯与水合肼的质量比为1∶7时,催化剂的Pt和Sn负载均最大,Pt与Sn的比值为1.41,Pt/Sn合金的平均粒径最小（1.8 nm）。此外,与其他催化剂相比,Pt-Sn/G-N （1∶7）具有最高的电催化活性,稳定性好,抗CO中毒能力强。即Pt-Sn/G-N （1∶7）的Pt与Sn实现了催化协同作用,为Pt-Sn催化剂在直接乙醇燃料电池（DEFCs）中的应用提供了更多的途径。     

高电活性石墨烯/聚苯胺纳米复合材料的制备和表征

采用了一种简单有效地方法制备了高电活性的石墨烯/聚苯胺复合材料。首先,将苯胺在氧化石墨烯（GO）的水性分散液中氧化聚合,制备了氧化石墨烯/聚苯胺（GO/PANI）,再将GO/PANI与水合肼反应,制得还原-氧化石墨烯/聚苯胺（R（GO/PANI））。利用透射电子显微镜（TEM）,热失重分析（TGA）和循环伏安法（CV）对GO/PANI和R（GO/PANI的形貌,热稳定性和电化学性能进行了分析研究。结果表明,GO表面存PANI,且R（GO/PANI）的热稳定性和电活性都明显高于GO/PANI。     

石墨烯/TiO2复合材料的制备及其光催化性能的研究

本实验以细鳞片石墨为原料,采用Hummers法制备氧化石墨,经超声波振荡得到氧化石墨烯,加入水合肼回流制得石墨烯材料。采用溶胶-凝胶法制备锐钛矿型TiO2及石墨烯/TiO2复合材料。在紫外光照射下,分别以石墨烯/TiO2复合材料及锐钛矿型TiO2为催化剂,在甲基橙溶液中进行光催化降解,结果显示,石墨烯/TiO2光催化性能明显高于相同条件下的锐钛矿型TiO2。     

Synthesis and characterisation of hydrophilic and organophilic graphene nanosheets

Hydrophilic graphene nanosheets were rapidly synthesized by reacting graphene oxide nanosheets with poly(sodium 4-styrene sulfonate) and simultaneously reducing by hydrazine hydrate under hydrothermal conditions. Organophilic graphene nanosheets were prepared by reacting with octadecylamine and reduction by hydroquinone through a reflux process. Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy measurements confirmed the attachment of organic molecules to the graphene nanosheets to achieve hydrophilic and organophilic affinity. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy analysis indicated that the crystal structure of the graphene nanosheets was maintained intact after chemical functionalisation.     

Conversion of pencil graphite to graphene/polypyrrole nanofiber composite electrodes and its doping effect on the supercapacitive properties

Graphene platelets were synthesized from pencil flake graphite and commercial graphite by chemical method. The chemical method involved modified Hummer's method to synthesize graphene oxide (GO) and the use of hydrazine monohydrate to reduce GO to reduced graphene oxide (rGO). rGO were further reduced using rapid microwave treatment in presence of little amount of hydrazine monohydrate to graphene platelets. Chemically modified graphene/polypyrrole (PPy) nanofiber composites were prepared by in situ anodic electropolymerization of pyrrole monomer in the presence of graphene on stainless steel substrate. The morphology, composition, and electronic structure of the composites together with PPy fibers, graphene oxide (GO), rGO, and graphene were characterized using X‐ray diffraction (XRD), laser‐Raman, and scanning electron microscopic (SEM) methods. From SEM, it was observed that chemically modified graphene formed as a uniform nanocomposite with the PPy fibers absorbed on the graphene surface and/or filled between the graphene sheets. Such uniform structure together with the observed high conductivities afforded high specific capacitance and good cycling stability during the charge–discharge process when used as supercapacitor electrodes. A specific capacitance of supercapacitor was as high as 304 F g^?1 at a current density of 2 mA cm^?1 was achieved over a PPy‐doped graphene composite. POLYM. ENG. SCI., 55:2118–2126, 2015. © 2014 Society of Plastics Engineers     

A graphene nanoribbon network and its biosensing application

Graphene oxide nanoribbons (GONRs) have been prepared by chemically unzipping multiwalled carbon nanotubes (MWCNTs). Thin-film networks of GONRs were fabricated by spray-coating, followed by a chemical or thermal reduction to form reduced graphene oxide nanoribbons (rGONRs). Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) characterizations indicate that the thermal reduction in the presence of ethanol vapor effectively restores the graphitic structure of the GONR as compared to chemical reduction with hydrazine vapor. Electrical measurements under a liquid-gate configuration demonstrates that rGONR network field-effect transistors exhibit much higher on/off ratios than a network of microsized reduced graphene oxides (rGOs) or a continuous film of single-layered pristine or chemical vapor deposited (CVD) graphene. Furthermore, we demonstrated the potential applications of rGONR networks for biosensing, specifically, the real-time and sensitive detection of adenosine triphosphate (ATP) molecules.     

Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide

Reduction of a colloidal suspension of exfoliated graphene oxide sheets in water with hydrazine hydrate results in their aggregation and subsequent formation of a high-surface-area carbon material which consists of thin graphene-based sheets. The reduced material was characterized by elemental analysis, thermo-gravimetric analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, NMR spectroscopy, Raman spectroscopy, and by electrical conductivity measurements.     

石墨烯量子点的制备及应用

石墨烯量子点(GQDs)作为石墨烯家族的最新一员,除了继承石墨烯的优异性能,还因量子限制效应和边界效应而显现出一系列新的特性,引起了化学、物理、材料和生物等各领域科研工作者的广泛关注。GQDs的制备方法通常分自上而下和自下而上的方法。对其各种制备方法和应用分别进行了介绍,并结合各种应用对GQDs的要求给出了制备方法的建议。指出了GQDs研究中存在的问题及发展方向。     

Mechanical,thermal, and rheological properties of graphene‐based polypropylene nanocomposites prepared by melt mixing

In this article, we describe the fabrication by melt mixing of graphene‐polypropylene nanocomposites and present the effect of graphene addition on some selected properties of polypropylene (PP). The graphene nanosheets (GNs) used as nano‐reinforcing agents were obtained through chemical reduction of graphene oxide by hydrazine hydrate. GNs were characterized and successfully dispersed into PP matrix to produce PP/GNs nanocomposites. The effects of GNs content on thermal, mechanical, and rheological properties were reported, and the obtained results were discussed in terms of morphology and state of dispersion and distribution of the GNs within the polymer matrix. Characterization by scanning electron microscopy and X‐ray diffraction of the nanocomposites has shown a relatively good dispersion of GNs in the polymer matrix, with the presence of only few aggregates. Increasing GNs content resulted in a significant increase in both mechanical and thermal properties with only few percent of GNs loading. Rheological behavior of the PP/GNs nanocomposites showed a Maxwellian‐like behavior for low GNs concentrations and a viscoelastic solid‐like behavior for GNs content exceeding the concentration of the percolation threshold. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

厄他培南合成用钯炭催化剂制备及性能评价

以乙醇改性活性炭为载体,采用沉积-沉淀法制备10%Pd/C催化剂,考察不同还原剂对厄他培南收率及废Pd/C催化剂Pd回收率的影响。结果表明,采用硼氢化钠和水合肼还原催化剂,废Pd/C催化剂的Pd回收率大于90%,明显高于甲酸和甲醛还原的催化剂,但水合肼还原催化剂的厄他培南收率较低。     

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.     

Graphene quantum dots prepared from chemical exfoliation of multiwall carbon nanotubes: An efficient photocatalyst promoter

We report here a facile preparation of graphene quantum dots (GQDs) by chemical exfoliation of multiwall carbon nanotubes (MWCNTs) using a modified hummers' method. The resultant GQD samples possess strong electronic property, revealing great potential for photocatalyst design. As an efficient promoter, GQDs/P25 nanocomposites have been successfully prepared by simple wet impregnation and subsequent thermal annealing at 200 °C. In the tests of photocatalytic degradation of organic dyes under visible-light irradiation, the GQDs promoted P25 samples which shows much higher photocatalytic activity compared to the pure P25, indicating the crucial roles of GQDs.     

Hydrazine-reduction of graphite- and graphene oxide

We prepared hydrazine-reduced materials from both graphite oxide (GO) particles, which were not exfoliated, and completely exfoliated individual graphene oxide platelets, and then analyzed their chemical and structural properties by elemental analysis, XPS, TGA, XRD, and SEM. Both reduced materials showed distinctly different chemical and structural properties from one another. While hydrazine reduction of graphene oxide platelets produced agglomerates of exfoliated platelets, the reduction of GO particles produced particles that were not exfoliated. The degree of chemical reduction of reduced GO particles was lower than that of reduced graphene oxide and the BET surface area of reduced GO was much lower than that of reduced graphene oxide.     

石墨烯负载纳米银的制备及其对H2O2的电化学检测

采用改进的Hummers法制备了氧化石墨烯（GO）,然后以水合肼作为还原剂,并控制反应的pH=10来制备还原氧化石墨烯（RGO）。采用化学还原法,以石墨烯为载体,以乙酰丙酮银为前体,以硼氢化锂四氢呋喃溶液为还原剂将银离子还原,制备了石墨烯负载纳米银复合材料。通过X 射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）和透射电子显微镜（TEM）等表征方法证明了石墨烯上负载的银纳米颗粒结晶良好、尺寸均一、分布均匀,其中银纳米颗粒直径约为8nm。通过循环伏安和计时电流技术对石墨烯负载纳米银复合材料进行电化学测试,结果表明,石墨烯负载纳米银复合材料对过氧化氢的还原具有良好的电催化活性。以此复合纳米结构构建的过氧化氢传感器测试过氧化氢浓度的线性范围为0.1～62.3mmol/L（R=0.990）,检出限为0.017mmol/L（S/N=3）,响应时间小于2s。     

Cellular distribution and cytotoxicity of graphene quantum dots with different functional groups

Graphene quantum dots (GQDs) have been developed as promising optical probes for bioimaging due to their excellent photoluminescent properties. Additionally, the fluorescence spectrum and quantum yield of GQDs are highly dependent on the surface functional groups on the carbon sheets. However, the distribution and cytotoxicity of GQDs functionalized with different chemical groups have not been specifically investigated. Herein, the cytotoxicity of three kinds of GQDs with different modified groups (NH₂, COOH, and CO-N (CH₃)₂, respectively) in human A549 lung carcinoma cells and human neural glioma C6 cells was investigated using thiazoyl blue colorimetric (MTT) assay and trypan blue assay. The cellular apoptosis or necrosis was then evaluated by flow cytometry analysis. It was demonstrated that the three modified GQDs showed good biocompatibility even when the concentration reached 200 μg/mL. The Raman spectra of cells treated with GQDs with different functional groups also showed no distinct changes, affording molecular level evidence for the biocompatibility of the three kinds of GQDs. The cellular distribution of the three modified GQDs was observed using a fluorescence microscope. The data revealed that GQDs randomly dispersed in the cytoplasm but not diffused into nucleus. Therefore, GQDs with different functional groups have low cytotoxicity and excellent biocompatibility regardless of chemical modification, offering good prospects for bioimaging and other biomedical applications.     

Fe-Al复合催化合成邻氯苯胺

研究了Fe-Al复合催化剂催化水合肼选择性还原硝基制备邻氯苯胺的条件。结果表明:Fe-Al复合催化剂催化水合肼还原硝基的选择性≥99%;还原反应的温度为70℃,物料比为n(邻氯硝基苯)∶n(水合肼)=1.0∶1.8,邻氯苯胺的收率为92.91%,ω(邻氯苯胺)≥99.5%。在工业上具有更广泛的应用价值。     

Microwave irradiation synthesis and characterization of RGO‐AgNPs/polystyrene nanocomposites

Polystyrene and reduced graphene oxide/silver (PSTY/RGO/AgNPs) nanocomposites were prepared via an in situ bulk polymerization method using two different preparation techniques. In the first approach, a mixture of silver nitrate, hydrazine hydrate, and polystyrene containing graphene oxide (PSTY/GO) were reduced by microwave irradiation (MWI) to obtain R‐(PSTY‐GO)/AgNPs nanocomposites. In the second approach, a mixture of the (RGO/AgNPs) nanocomposite, which was produced via MWI, and STY monomers were polymerized using an in situ bulk polymerization method to obtain PSTY‐RGO/AgNPs nanocomposites. The two nanocomposites were compared and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, high‐resolution transmission electron microscopy, Differential scanning calorimetry, and thermogravimetric analysis. The results indicate that the nanocomposites obtained using the first approach, which involved MWI, exhibited a better morphology and dispersion with enhanced thermal stability compared to the nanocomposites prepared without MWI. POLYM. COMPOS., 35:2318–2323, 2014. © 2014 Society of Plastics Engineers     

TiO_2/SiO_2复合纳米纤维的GQDs改性及其对甲醛的可见光催化降解性能

采用静电纺丝法合成了TiO_2/SiO_2柔性复合纳米纤维膜,而后对其进行石墨烯量子点(GQDs)改性,制备了GQDs/TiO_2-SiO_2复合纳米纤维,其中GQDs用水热法合成。用X射线衍射仪(XRD)、电子万能材料试验机、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)对其物相组成、力学性能、微观形貌以及光催化性能进行了表征。结果表明:尺寸在7 nm~15 nm之间的GQDs松散沉积在直径为200 nm~400 nm的TiO_2/SiO_2纳米纤维上,纤维连续性好,复合薄膜有较好的力学性能;TiO_2的结晶较好,为锐钛矿相;GQDs复合后将TiO_2的本征吸收从390 nm左右延伸到了420 nm左右,拓宽了TiO_2的吸收范围。在可见光催化降解中,初始浓度为0.32 mg/m~3的甲醛气体110 min后的降解效率达到70%。     

Blue and green luminescence of reduced graphene oxide quantum dots

We report on a new method for synthesising strongly blue and green photoluminescent graphene quantum dots (GQDs). Graphene was prepared by a new feasible method using an intensive cavitation field in a pressurised ultrasonic batch reactor. The prepared graphene was quantitatively converted to graphene oxide using our modified, safer Hummer’s method. Graphene oxide was characterised by microscopic (AFM and TEM) and spectral (infrared and Raman) methods, and the thermal stability of graphene oxide was determined using thermal analysis (DTA-TG). GQDs were prepared by a one-pot reaction, refluxing graphene oxide in different solvents (ethylene glycol, polyethylene glycol, dimethylformamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone) at atmospheric pressure. The synthesised GQDs were characterised by infrared, UV–Vis absorption and photoluminescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and AFM microscopy.     

Preparation of Ag/reduced graphene oxide reinforced copper matrix composites through spark plasma sintering: An investigation of microstructure and mechanical properties

The reduced graphene oxide (rGO) decorated with Ag nanoparticles was synthesized by the chemical reduction of graphene oxide in an aqueous solution containing AgNO₃, in the presence of hydrazine hydrate as a reducing agent. The reduction of graphene oxide was confirmed by FT-IR and raman spectroscopy analyses. The x-ray diffraction pattern and UV–visible investigations demonstrated the formation of Ag particles on the surface of rGO sheets. After successful decoration, the Ag/rGO nano-composite was used as the reinforcement in the copper matrix composite. Cu–Ag/rGO composites with different percentages of Ag/rGO (0.4, 0.8, 1.6 and 3.2 vol%.) were prepared by mechanical milling and spark plasma sintering (SPS). The effects of the Ag/rGO content on the consolidation process, micro-hardness, bending strength and also, fracture surface of the prepared samples were then investigated. The three-point bending strength of the sintered samples was increased from 285 to 472 MPa by the addition 0.8 vol%. of Ag/rGO, as compared to the pure Cu. Moreover, increasing the reinforcement content to the 3.2 vol%. Ag/rGO led to decreasing the bending strength to 433 MPa. The highest micro-hardness (81 Hv) was obtained for the composite sample containing the 1.6 vol%. Ag/rGO. By increasing Ag/r-GO as the reinforcement (3.2 vol%.), the Vickers hardness was decreased to 69 Hv. Also, investigation of the fracture surface morphology showed transformation of fracture mechanism from plastic changes to brittle ones by raising the Ag/rGO content volume from 0.8 to 1.6 vol %.