Microstructure and growth mechanism of multi-layer graphene standing on polycrystalline SiC microspheres

Multi-layer graphene standing on polycrystalline SiC microspheres was prepared by pyrolyzing liquid polysilacarbosilane. The lateral dimension of the multi-layer graphene is ∼100 nm and the average diameter of the microspheres is ∼0.9 μm. The growth of the multi-layer graphene is proposed to be initiated by phase separation of the microspheres, and facilitated with both crystallization inside and chemical vapor deposition outside. This method offers an alternative way to prepare multi-layer graphene on SiC without the need for 4H– or 6H–SiC crystals.     

Synthesis and thermal stability of carbon-supported Ru-Ni core-and-shell nanoparticles

Binary nanoparticles of Ru-Ni supported on a carbon nanolayer and carbon-coated Ru-Ni core-and-shell nanoparticles were synthesized in a single step spray-pyrolysis process. A precursor containing ruthenium chloride and nickel chloride solution mixture was used to deposit Ru-Ni nanoparticles on a carbon nanolayer generated from hexane. Carbon-coated nanoparticles were produced by using ruthenium chloride and nickel chloride solution mixed with methanol and hexane as precursor in the spray-pyrolysis process. A carbon layer that was derived from the thermal decomposition of hexane and methanol forms a protective shell around the binary core-and-shell nanoparticles of Ru-Ni. TEM and EDS spectral graphs confirm the presence of carbon layers encapsulating the Ru-Ni nanoparticles. The encapsulating carbon layers are effective in reducing agglomeration of binary nanoparticles in the spray-pyrolysis process. The carbon-coated binary nanoparticles were subjected to heat treatment at temperatures up to 800 °C, the size and morphology of the nanoparticles before and after heat treatment were compared to examine the thermal stability of the nanoparticles. It was observed that the carbon-coated Ru-Ni nanoparticles exhibit unique thermal stability. EDS, SEM, and TEM data revealed that the morphology of the nanoparticles did not change during the heat treatment.     

Synthesis of stable AuAg bimetallic nanoparticles encapsulated by diblock copolymer micelles

We present a facile method for the preparation of bimetallic AuAg nanoparticles (NPs) with controlled size and composition rendering them ideally suitable for optical and catalytic applications. In analogy to methods for the generation of monometallic Au and Ag NPs, AuAg NPs were prepared inside polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block-copolymer micelles formed in toluene, by loading the P4VP cores of the micelles first with AgNO(3) and then with HAuCl(4). In contrast to the reverse sequence of loading, homogenously bimetallic AuAg particle arrays were achieved after reduction carried out in solution with hydrazine monohydrate as the reducing agent. TEM reveals that stable and spherical NPs can be prepared well separated from one another and with a narrow size distribution with diameters of ～3 nm. The bimetallic NP composition was confirmed by energy-dispersive X-ray spectroscopy (EDX) of single NPs. The atomic ratio of Ag and Au contained in single particles is in good agreement with the relative concentrations of both metals used in the synthesis which was confirmed by atomic absorption spectroscopy. The atomic ratio Au?:?Ag was systematically varied between 3?:?1 and 1?:?3. For all ratios UV-vis spectra showed a single plasmon band. Its wavelength varied from 430 for Au?:?Ag = 1?:?3 to 515 nm for Au?:?Ag = 3?:?1, showing a linear dependence on the relative amount of gold within the range of plasmon wavelengths from monometallic gold (538 nm) to silver (415 nm).     

采用不同方法合成CuS纳米粒子研究

分别采用水热合成法及微乳液法制备了纳米CuS粒子。以醋酸铜和升华硫为原料配成稳定溶液,进行水热合成得到纳米CuS粒子;以表面活性剂十六烷基三甲基溴化铵(CTAB)、有机溶剂正庚烷、水和助表面活性剂正丁醇组成的W/O型微乳体系,在加热状态下合成纳米CuS粒子。并采用UV-VIS、XRD和TEM等分析手段对粉体进行了表征。     

溶剂稳定的铜纳米颗粒的制备

以乙二醇为溶剂、硼氢化钾为还原剂制备了溶剂稳定的铜纳米颗粒.以紫外可见光谱研究了制备铜纳米颗粒的最佳还原剂与硫酸铜之摩尔比,以透射电子显微镜对在最佳条件下制备的铜纳米颗粒进行了表征.实验表明,硼氢化钾与硫酸铜的摩尔比较小更利于制备粒径小、粒径分布窄、团聚程度低的铜纳米颗粒.     

Synthesis and characteristics of carbon encapsulated magnetic nanoparticles produced by a hydrothermal reaction

A novel process to synthesize carbon encapsulated magnetic nanoparticles was developed by heating an aqueous glucose solution containing Fe@Au (Au coated Fe nanoparticles) or Ni nanoparticles at 160–180 °C for 2 h. In comparison with traditional methods, such a hydrothermal approach is not only simple but also able to provide functional groups such as –OH on the surface of carbon sphere. Only pure Fe nanoparticles did not favor the formation of carbon encapsulated magnetic nanoparticles due to the oxidation of Fe nanoparticles by H₂O during the reaction and their surfaces had to be coated by an Au shell in advance. The results of TEM, HRTEM, XRD, XPS and vibration sample magnetometer characterization show that uniform carbon spheres containing some embedded Fe@Au nanoparticles with a saturation of 14.6 emu/g are obtained and the size of a typical product is 200 nm. Carbon encapsulated Ni nanoparticles have been successfully prepared in the same way.     

Synthesis and properties of modified graphite encapsulated iron metal nanoparticles

Graphite encapsulated iron metal nanoparticles (FeGEM) are a core/shell nanostructured material. By introducing various liquid alcohols as carbon source during modified arc-discharge synthesis procedures, we succeeded in raising the yield rate of FeGEM from 10 wt.% to 40–50 wt.%. However, the hydrophobic outer graphite (graphene) shells and the strong magnetic attraction between inner ferromagnetic iron cores can easily lead to rapid agglomeration and precipitation of FeGEM nanoparticles in a polar solvent such as water. As a result, it may impede many potential applications of FeGEM nanoparticles in numerous fields.To overcome the problem, it is necessary to change the hydrophobic surface of FeGEM nanoparticles to a hydrophilic one. In this work, we show that progressive sequential refluxing in nitric acid, thionyl chloride and tetraethylenepentamine (TEPA) can modify FeGEM nanoparticles with different functional groups. After refluxing with nitric acid solution, the grafted FeGEM is able to disperse in polar solvent, such as deionized water or ethanol for over 24 h. Zeta potential analysis and SQUID were used to characterize the grafted FeGEM at the refluxing step, and ultraviolet–visible spectrophotometry was used to measure the suspension ability of modified FeGEM nanoparticles in a colloidal system.     

粒径可控的铜纳米粒子的液相还原法制备

在一定温度的水溶液中,采用铜离子前躯体,水合肼为还原剂,在PVP存在下,进行了粒径、形貌可控的纯铜纳米粒子的合成,获得了粒径在7～70nm的铜纳米粒子.通过X射线衍射仪、紫外一可见分光光度计、透射电子显微镜、扫描电子显微镜和电子衍射等手段对产物测试与表征,证实了上述结果.同时证明,粒径可由奥斯瓦尔德老化过程控制,保护剂可在一定程度上控制粒子形貌.     

Controlled assembly of graphene shells encapsulated gold nanoparticles and their integration with carbon nanotubes

Controlled growth and uniform patterning of graphene/carbon shells encapsulated gold nanoparticles (GNPs) on silicon wafer or on high curvature carbon nanotubes (CNTs) is reported here. This was achieved by utilizing patterned gold nanoparticles with controlled sizes (∼30–600 nm) via gold film dewetting process. Surface-oxidized and patterned nanoparticles were used as sacrificial catalysts for the chemical vapor deposition (CVD) growth of graphene/carbon shells. The shell morphological evolution and thickness as well as surface migration of nanoparticles during the CVD process were studied as a function of the gold nanoparticles size. Reduced surface migration and coalescence was observed for gold nanoparticles after the CVD growth and this was attributed to the initial formation of graphene/carbon shells as well as stable dispersion of the dewetted gold nanoparticles. It is proposed that graphene/carbon shell growth was controlled by Ostwald’s ripening, surface gold oxide, and reducing CVD growth environment. Furthermore, complex heterostructures based on CNTs coated with GNPs were fabricated by dewetting Au films on CNTs and followed by surface oxidation and CVD growth steps. CNTs successfully survived multiple processing steps and selective growth of graphene shells around Au nanoparticles was achieved and studied using microscopic and spectroscopic methods.     

石墨烯导热高分子复合材料的制备、性能与机理

石墨烯是一种具有超大的比表面积、良好的热和化学稳定性、超高的热导率以及易于化学修饰的蜂窝状单层碳材料,已作为填料广泛应用于导热高分子复合材料领域。近年来石墨烯导热高分子材料的研究重点是改善石墨烯在聚合物基体中的界面相容性和分散性能。阐述了近年来石墨烯导热高分子复合材料的制备方法及其热性能,并重点对石墨烯导热高分子复合材料的导热机理进行综述,同时结合研究现状对石墨烯导热高分子复合材料的研究方向进行展望。     

葡萄糖辅助热分解法制备CdS纳米粒子

通过葡萄糖辅助热分解法制备出CdS纳米粒子,对产品进行了表征。在反应过程中葡萄糖可以阻止产物团聚,进而有效地降低产物尺寸。根据前驱体热分解过程的热重分析仪和差热分析仪测试结果,提出了葡萄糖的形貌控制机理。最后研究了葡萄糖加入量和辅助剂种类对产物形貌的影响。     

乙二醇改性聚脲微胶囊相变材料的研制

以硬脂酸丁酯为芯材,吐温80、司班80为乳化分散剂,以单体2,4-甲苯二异氰酸酯和三乙烯四胺反应,并采用乙二醇进行改性形成的聚脲树脂为壳体,采用界面聚合法制备微胶囊相变材料。采用差示扫描量热仪（DSC）、扫描电镜（SEM）、氮气吸脱附测试仪等对微胶囊热性能、表面形态和比表面积进行了分析表征。结果表明,所制备的乙二醇改性微胶囊相变温度为20.5℃,相变潜热为87.75 J/g;平均比表面积0.009 9 m2/g,致密性较好。     

Synthesis of graphene decorated with silver nanoparticles by simultaneous reduction of graphene oxide and silver ions with glucose

A green and efficient approach for the synthesis of graphene decorated with silver nanoparticles is demonstrated by simultaneously reducing both graphene oxide (GO) sheets and silver ions with glucose as the reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as the surface modifier. Different silver-containing materials are obtained by changing the synthesis temperature. The oxygen-containing groups of the substrate influence its decoration with the in situ formed silver nanoparticles. The combination of glucose and a silver–ammonia solution, as well as maintaining a good dispersion of GO by using PVP are crucial for the decoration of graphene with silver nanoparticles. The materials exhibit a distinct surface-enhanced Raman scattering effect.     

Improved thermal stability of oxide-supported naked gold nanoparticles by ligand-assisted pinning

We report a method to improve the thermal stability, up to 900 °C, of bare-metal (naked) gold nanoparticles supported on top of SiO(2) and SrTiO(3) substrates via ligand-assisted pinning. This approach leads to monodisperse naked gold nanoparticles without significant sintering after thermal annealing in air at 900 °C. The ligand-assisted pinning mechanism is described.     

Synthesis of novel copper nanoparticles/ternary polymer blend nanocomposites and their structural,thermal and rheological properties and AC impedance

Copper nanoparticles (Cu NPs)/ternary polymer blend nanocomposites were synthesized via a solution‐casting technique. The nanocomposites were studied for their structural, thermal, rheological and electric properties. Scanning electron micrographs and atomic force micrographs showed no phase separation between the polymers, a narrow size distribution of Cu NPs (in the range 25–43 nm) and good dispersion of Cu NPs in the polymer matrix. Energy‐dispersive X‐ray analysis confirmed the presences of Cu in the matrix. X‐ray diffraction data showed a characteristic face‐centred cubic architecture for Cu unit cell and interaction of the Cu NPs with oxygen‐carrying polymers. Thermogravimetric analysis showed an increase in the degradation temperature (from 254 to 268 °C) and three‐step degradation of the nanocomposites. Rheological analysis showed an increase in the complex viscosities and storage modulus for the nanocomposites. AC impedance studies showed increased ionic conductivities and decreased bulk resistance for the nanocomposites. All these studies suggested interactions between Cu NPs and polymer matrix and the formation of a network structure. © 2017 Society of Chemical Industry     

Substrate-free synthesis of large area, continuous multi-layer graphene film

Large area (∼cm²) multi-layer graphene film is synthesized in the substrate-free vapor phase. The scanning electron microscopy observation reveals that the graphene nanoflakes are either six- or five-sided, and the internal angles between adjacent sides are nearly 120° and 105°, respectively. The nucleation of hexagonal and pentagonal carbon rings leads to carbonaceous nuclei, which grow into six- or five-sided nanoflakes, respectively. A well-ordered and large-area graphene monolayer is formed by the interconnection of these flakes, and stacking of these monolayers results in the formation of a multi-layer graphene film. The creation of hexagonal and pentagonal carbon rings is considered to be important for the easy production of large area multi-layer graphene at large scale.     

Synthesis and thermal stability of carborane-containing phosphazenes

Carborane-substituted polyphosphazenes were prepared by the thermal polymerization of phenyl-carboranyl pentachlorocyclotriphosphazene. Successive isothermal vacuum pyrolyses were conducted on the polymer and examined for structural changes by infrared spectroscopy. The degradation products were ascertained by gas chromatography-mass spectrometric analysis. It was found that the presence of the carborane group improves the thermal stability of the polymer by retarding the ring-chain equilibrium processes of decomposition.     

硅钛弹性体的合成及热稳定性研究

以三甲基三苯基环三硅氧烷为原料,四氯化钛为钛源,一步法合成了不同硅钛比例的硅钛弹性体。采用FT-IR(红外光谱)法、FT-Raman(拉曼光谱)法、NMR(核磁共振波谱)、GPC(凝胶渗透色谱)法对产物进行结构表征,利用DSC(差示扫描量热)法研究了产物的玻璃化转变温度,利用TGA(热重分析)研究了产物的热性能。研究结果表明:随着硅钛比例的升高,产物的玻璃化转变温度降低,但高温固化会使硅钛弹性体的玻璃化转变温度变高;硅钛弹性体TSE20的综合热性能较好,它的初始分解温度为322℃,800℃时的残炭率为50.6%。     

Synthesis,characterization and antimicrobial activity of colloidal copper nanoparticles stabilized by cationic thiol polyurethane surfactants

Metal nanoparticles have attracted considerable interest particularly because of the size dependence of physical and chemical properties and its enormous technological potential. Among different metal nanoparticles, copper nanoparticles have attracted great attention because copper is one of the most key metals in new technology. Chemical methods are used to synthesize copper nanoparticles. Chemical reduction is the most frequently applied method for the preparation of stable, colloidal dispersions in organic solvents. In this paper, the new cationic thiol polyurethane surfactants with different alkyl chain length were synthesized (PQ10, PQ14 and PQ18). The chemical structure of the synthesized surfactants was confirmed using infra-red spectroscopy (IR) and proton nuclear magnetic resonance spectroscopy (¹HNMR). Copper nanoparticles colloidal solution of 40–80 nm diameters was prepared using sodium borohydride in aqueous solution at room temperature as reducing agent. The synthesized surfactants decrease the aggreegation of copper nanoparticles. The nanostructure of the synthesized surfactant with copper nanoparticles with diameters ranging from 31.5 to 10.3 nm was prepared and characterized using ultra violet spectrophotometer (UV), infra-red spectroscopy (IR) and transmission electron microscope (TEM). The results declare formation and stabilization of copper nanoparticle using synthesized cationic surfactants. Antimicrobial activity of the synthesized cationic surfactants and their nanostructure with copper nanoparticles were evaluated against pathogenic bacteria and fungi.