Poly(amidoamine)-G5 dendrimers/noble metal gold hybrid nanoparticles prepared by γ-ray irradiation

In the absence of a chemical reductant and other protective reagents, noble metal gold hybrid nanoparticles are successfully prepared by ⁶⁰Co γ-ray irradiation using fifth-generation poly(amidoamine) dendrimer with surface amine-terminated group as polymeric template. The zerovalent gold is of spherical structure and the particle size is on nanometer scale range of 3-12 nm. The size distribution of gold nanoparticles displays multidispersity. The results of FTIR show that interactions between dendrimer template and gold nanoparticle exist in intra-molecule and inter-molecule of fifth-generation poly(amidoamine) dendrimer.     

Adsorptive separation and photocatalytic degradation of methylene blue dye on titanate nanotube powders prepared by hydrothermal process using metal Ti particles as a precursor

Titanate nanotube powders (TNTPs) with the twofold removal ability, i.e. adsorptive separation and photocatalytic degradation, are synthesized under hydrothermal conditions using metal Ti particles as a precursor in the concentrated alkaline solution, and their morphology, structure, adsorptive and photocatalytic properties are investigated. Under hydrothermal conditions, the titanate nanotubes (TNTs) with pore diameter of 3-4 nm are produced on the surface of metal Ti particles, and stacked together to form three-dimensional (3D) network with porous structure. The TNTPs synthesized in the autoclave at 130 °C for 24 h exhibits a maximum adsorption capability of about 197 mg g⁻¹ in the neutral methylene blue (MB) solution (40 mg L⁻¹) within 90 min, the adsorption process can be described by pseudo second-order kinetics model. Especially, in comparison with the adsorptive and the photocatalytic processes are performed in turn, about 50 min can be saved through synchronously utilizing the double removal ability of TNTPs when the removal ratio of MB approaches 95% in MB solution (40 mg L⁻¹) at a solid-liquid (S/L) ratio of 1:8 under ultraviolet (UV) light irradiation. These 3D TNTPs with the twofold removal properties and easier separation ability for recycling use show promising prospect for the treatment of dye pollutants from wastewaters in future industrial application.     

Fourier transform infrared spectroscopy characterization of AlN thin films grown on sacrificial silicon oxide layers via metal organic vapor phase epitaxy

Aluminum nitride (AlN) films were grown using metal organic vapor phase epitaxy techniques on Si (111) substrates patterned with silicon oxide (SiO_x) stripes and the vibrational properties of these films were investigated by Fourier transform infrared (FTIR) techniques. The grown films contained a predominantly wurtzite AlN phase. The AlN film on SiO_x was prone to corrosion when subjected to wet etching in buffered hydrofluoric acid solution thereby changing the material properties of the AlN film on SiO_x. The change in the material properties of the AlN films on SiO_x can be gauged from the decrease in the relative integrated areas under the A1 (TO) and E1 (TO) modes of the AlN film. The analysis shows that FTIR is a viable tool for investigating the material properties of AlN thin film structures with lateral dimensions as low as 100 μm.     

Fabrication of a room-temperature NO2 gas sensor based on WO3 films and WO3/MWCNT nanocomposite films by combining polyol process with metal organic decomposition method

Polyol process was combined with metal organic decomposition (MOD) method to fabricate a room-temperature NO₂ gas sensor based on a tungsten oxide (WO₃) film and another a nanocomposite film of WO₃/multi-walled carbon nanotubes (WO₃/MWCNTs). X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the structure and morphology of the fabricated films. Comparative gas sensing results indicated that the sensor that was based on the WO₃/MWCNT nanocomposite film exhibited a much higher sensitivity than that based on a WO₃ film in detecting NO₂ gas at room temperature. Microstructural observations revealed that MWCNTs were embedded in the WO₃ matrix. Therefore, a model of potential barriers to electronic conduction in the composite material was used to suggest that the high sensitivity is associated with the stretching of the two depletion layers at the surface of the WO₃ film and at the interface of the WO₃ film and the MWCNTs when detected gases are adsorbed at room temperature. The sensor that is based on a nanocomposite film of WO₃/MWCNT exhibited a strong response in detecting very low concentrations of NO₂ gas at room temperature and is practical because of the ease of its fabrication.     

Formation process of silver nanoparticles in DTAB/SDBS/PVP aqueous solution

Silver nanoparticles were prepared from the nitrate silver solution in dodecyl trimethyl ammonium bromide (DTAB)/sodium dodecylbenzenesulfonate (SDBS)/polyvinyl pyrrolidone (PVP) complex solution with hydrazine as the reductant. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV–Vis spectroscopic analysis were conducted to investigate the role of anionic–cationic surfactants on the growth process of silver particles. The results showed that, before the formation of spherical silver nanoparticles, the cube and then tetrakaidecahedrons of AgBr were initially formed. It is concluded that the selective interaction of bow-like electric double-layer structure of anionic–cationic surfactants with certain crystallographic planes of crystals dominated the morphology evolvement of the reaction products. In addition; the PVP coverage finally encouraged the formation of well-dispersed spherical silver nanoparticles.     

Sharp cubic and octahedral morphologies of poly(vinylpyrrolidone)-stabilised platinum nanoparticles by polyol method in ethylene glycol: their nucleation,growth and formation mechanisms

Pt nanoparticles (NPs) were synthesised by a modified polyol method with the addition of silver nitrate. The results showed that the specific shapes of Pt NPs were influenced by the relevant factors, which are the contents of silver nitrate, synthetic time and temperature. A small content of silver nitrate has played an important role in determining their final shapes of platinum NPs. We observed that Pt NPs in the forms of very sharp shapes such as Pt cubes, octahedrons, cuboctahedrons and tetrahedrons have been obtained. In addition, the shape growth mechanisms and formation of Pt NPs have been studied. They exist in both cubic and octahedral shapes. Importantly, Pt nanocrystals can grow into main cubic and octahedral shapes for a short time less than 15?min. Moreover, Pt nanocrystals can also grow into different shapes from cubic and octahedral into spherical ones for several hours. Especially, they exhibited interesting shapes of multiple-branched Pt nanostructures because of their overgrowth and aggregations. Clearly, large cubic and octahedral Pt NPs of 160?nm diameter were observed. The growth and formation of large cubic and octahedral Pt NPs were due to the aggregation of Pt clusters or initial Pt seeds, even small Pt nanocrystals.     

制备工艺对锌铝氧化物(ZAO)粉末红外发射率的影响

采用液相共沉淀法制备了ZAO掺杂半导体粉末材料,系统研究了制备工艺对ZAO粉末红外发射率的影响.借助于TG-DTA、XRD、SEM对材料的热处理温度,晶体结构及表面形貌进行了考察,利用IR-2双波段发射率测量仪对ZAO粉末材料的红外发射率进行了测试.研究结果表明:当反应物终点pH值为8.5、反应时间为2.5h、煅烧温度为800℃,煅烧时间为2h、Al2O3的掺杂量为3%时所得的ZAO粉末的红外发射率最低;ZAO掺杂半导体粉末的晶体结构为ZnO的铅锌矿结构;粒子形状近似为椭圆形,平均粒径为5～10μm;在中红外(3～5μm)和远红外(8～14μm)波段均具有较低的红外发射率.     

Sacrificial seed mediated synthesis of copper nanopots by a modified polyol process

A novel modified polyol process has been developed for the synthesis of hollow copper nanopots. Cobalt hydrazine complex was employed for the preparation of cobalt nanoparticles (NPs), which in turn acted as sacrificial seeds for the production of Cu nanopots and nanocups. The reduction of Cu²⁺ to Cu⁰ was observed by the colour change from bluish green to dark brownish red. The reaction was followed with the help of a UV–Vis spectrometer. A surface plasmon band at 558?nm indicated the formation of Cu NPs. Chemical characterisation was carried out using inductively coupled plasma optical emission spectrometer and Leco gas analysers, CS-444 and TC-600. Crystal structure was obtained by carrying out X-ray diffraction studies and it showed a face centred cubic structure. Particle size and morphology were obtained from scanning electron microscope. On average, copper nanopots of size 72?nm could be obtained using this method.     

Study on thermodynamics and oxidation mechanism of ethylene glycol in the preparation of nanometer nickel powders

Nanometer nickel powders have been prepared using the polyol method with NaOH, Ni(NO₃)₂·6H₂O, ethylene glycol (EG), and polyvinylpyrrolidone (PVP) as raw materials. The thermodynamics of the reaction system was studied, and the E–pH diagram of Ni–EG–H₂O was plotted. The oxidation products of EG were predicted from the E–pH diagram, and CO₃²⁻ in alkaline solutions was identified as the product through the IR spectrum and CaCO₃ sediment. Field-emission scanning electron micrograph (FE-SEM) showed that spherical nanometer nickel powders were obtained.     

多元醇法制备CoNi纳米粒子的形成机制,尺寸控制及磁性能

采用多元醇法在150～190℃合成了CoNi合金纳米粒子,利用SEM-EDX,XRD和VSM对所制备的CoNi纳米粒子形貌、成分、结构以及磁性能进行了研究,并进一步探讨了形核剂K2PtCl4对CoNi纳米粒子形貌及磁性能的影响。结果表明,在180℃用多元醇法制备的Co40Ni60(inat%)纳米粒子为FCC结构,Co2+要易于Ni2+被还原,导致最初10min内合成的CoNi纳米粒子中含有约78%(原子分数)Co,表现为高饱和磁化强度和高矫顽力,随着反应时间的延长,CoNi纳米粒子的Co含量、饱和磁化强度及矫顽力逐步下降。在150～190℃范围内,随着反应温度的提高,Ni2+的被还原能力增强,高温下合成的CoNi纳米粒子具有较低的饱和磁化强度和较小的矫顽力。形核剂K2PtCl4的加入,并不影响CoNi合金纳米粒子的成分和晶体结构。但是,随着形核剂浓度的增加,CoNi纳米粒子平均直径明显减小,其矫顽力有所增大。通过设计形核剂的浓度,CoNi纳米粒子的直径可以在96～580nm范围内任意控制。     

Preparation of La1−xSrxMnO3 powders by combustion of poly(ethylene glycol)–metal nitrate gel precursors

La1–xSrxMnO3 powders were prepared by auto-ignited combustion of poly(ethylene glycol) (PEG)–metal–nitrate gel precursors. The thermal behaviour of the precursors strongly depends on the ratio of PEG to metal nitrate, which is closely related to the ratio of fuel to oxidizer. The burning behaviour in a furnace was successfully explained by valence concepts normally encountered in propellant chemistry. The formation of a pure perovskite phase was significantly influenced by the homogeneity of the gel precursor. Perovskite structured oxides were formed through two different paths, one of which was direct formation from the burning of a gel precursor and the other was a subsequent structural evolution by heat treatment after burning. The formation procedure of the perovskite and the morphology of powders could be explained in terms of the burning behaviour of the precursor and the role of organic residue.     

气相催化裂解法制备微米级螺旋形炭纤维的研究

以商用乙炔为碳源，镍板为催化剂，含硫化合物为助催化剂，通过气相催化裂解法（VCC）制得了微米级螺旋形炭纤维。通过对影响微螺旋形炭纤维生长因素研究。发现将镍板直立放置于石英管中，可以提高螺旋形炭纤维的收率。同时发现反应温度为710℃～800℃，C2H2/H2=1：3。含硫化合物的流量为1.0mL/min～1.2mL/min时，有利于规整螺旋纤维的生成，通过调节N2的流量，可以获得螺径不同的炭纤维。气体总流量约200mL/min时可制得螺径约4μm的规整炭纤维；气体总流量约150mL/min时可获得螺径约20μm的炭纤维。利用扫描电子显微镜（SEM）考察了螺旋纤维的微观形貌，发现所得的纤维几乎为双螺旋，同时在螺旋纤维生长的先端常观察到由弯曲纳米级纤维形成的绒状物。     

乙二醇稳定的NaBH4还原法制备纳米Pt/C催化剂

分别采用乙二醇(EG)和H2O为溶剂,通过NaBH4还原法在酸性pH≤2和碱性pH≥12条件下制备了铂担裁量为20%(质量分数)的Pt/C催化剂,利用TEM、CV及LSV等方法对催化剂进行了表征与测试,考察了EG在NaBH4还原法中对铂纳米颗粒的稳定作用.结果表明,EG作溶剂、碱性pH≥12时,通过NaBH4还原法制备得到了平均粒径约2.5nm、粒径分布窄、在碳裁体上分散均匀的Pt/C催化荆;该催化剂的电化学比表面为74.4m2/g Pt,0.8V vs NHE时通过LSV得到的单位质量铂对甲醇电催化氧化的电流密度为229.1mA/mg Pt,分别是相同条件下H2O作溶剂时制备得到的Pt/C催化剂的5.倍和5.3倍.     

Composite Ag/C:H:N films prepared by planar magnetron deposition

Composite Ag/C:H:N films were deposited by means of an unbalanced magnetron operated in a gas mixture of nitrogen and n-hexane. Composition of the films was controlled by electric power delivered to the magnetron and by ratio of nitrogen and n-hexane in the working gas mixture. The films were characterized using transmission electron microscopy, by the absorption spectra in visible and near infrared regions and by Fourier transform infrared spectroscopy. Immediately after film deposition and without breaking vacuum (in situ) corresponding vibration infrared spectra were scanned and their evolution during ageing of the films was monitored. Wettability as determined from water contact angle was improved with raising nitrogen contents, i.e. with increasing the electric power and the ratio of nitrogen/n-hexane in the working gas mixture. The increased wettability is likely caused by presence of NH_x groups in Ag/C:H:N films. The incorporation of nitrogen effectively prevents the formation of carboxylate groups on the silver inclusions surfaces during the aging in the open air. In addition, the oxidation mechanism of the polymer matrix is modified.     

Controllable growth of dendrite-like CuO nanostructures by ethylene glycol assisted hydrothermal process

The dendrite-like CuO nanostructures, consisting of a rod-like main stem and some rod-like sub-branches, have been synthesized by a simple ethylene glycol (EG) assisted hydrothermal method. The X-ray diffraction (XRD) and the selected area electron diffraction (SAED) patterns indicate that the dendrite-like CuO nanostructures are of monoclinic phase and the individual branch of CuO is single crystalline in nature. The effects of the growth conditions such as temperature and pH value on the morphology and structures of CuO have also been investigated. It is indicated that different temperature and pH value result in the morphology and structure evolution of CuO. Moreover, a possible mechanism for the morphology and structures evolution of CuO has been primarily presented.     

Synthesis of silver nanoparticles in a polyvinylpyrrolidone (PVP) paste, and their optical properties in a film and in ethylene glycol

Silver nanoparticles were synthesized in a paste of polyvinylpyrrolidone formed after mixing PVP with acetone and a small volume of aqueous silver nitrate under magnetic stirring. A film made with the material was characterized by UV-vis spectroscopy. The obtained spectrum shows a single peak at 438 nm, arising from the surface plasmon absorption of silver colloids. This result clearly indicates that silver nanoparticles are embedded in PVP. When the pre-treated PVP-Ag colloid is dissolved in ethylene glycol, the UV-vis spectrum of the resulting dispersion shows an absorption peak at 433 nm, whose maximum absorption blue shifts to 416 nm after 18 days of agitation. The silver nanoparticles have an average particle size of 4.12 nm. Because the IR band assigned to the carbonyl group of the PVP shifts to longer wavelengths, the interaction of this polymer with silver nanoparticles seems to take place through the carbonyl oxygen.     

Characterization of carbon thin films prepared by the thermal decomposition of spin coated polyacrylonitrile layers containing metal acetates

Polyacrylonitrile (PAN) layers were cast from dimethyl-formamide solutions onto quartz substrates by spin coating and subsequently annealed at up to 1000 °C in N₂ atmosphere. Carbonization was catalyzed by nickel or cobalt added to the solution as acetate salts. The synthesized films were approx. 970 nm thick and were characterized by Raman and infrared spectroscopy as well as thermogravimetric and electrical conductance measurements. We discuss the effects of carbonization temperature and metal concentration on the morphology, composition and electrical properties of the formed carbon layer. Increasing the amount of catalyst and the pyrolysis temperature was beneficial for the process and resulted in carbonaceous films with a higher degree of structural order as evidenced by the decreasing Raman I_D/I_G ratio and the increasing electrical conductivity of the films. Cobalt is a better catalyst for PAN carbonization than nickel as far as the structure of the product film is concerned.     

静电纺丝法制备金纳米粒子/PVP复合纳米纤维

采用水合肼还原一定浓度氯金酸溶液的方法,在聚乙烯吡咯烷酮(PVP)作保护剂的乙醇/水溶液中,成功制备出粒度较小,且高度分散的金溶胶,紫外吸收光谱证实了溶液中金纳米粒子的存在.采用静电纺丝技术制备了AuNs/PVP复合纳米纤维.采用扫描电镜(SEM)和X射线衍射(XRD)等分析手段对纤维的表面形貌等进行了表征.由扫描电镜...