Room temperature synthesis of colloidal platinum nanoparticles

Efficient preparation of stable dispersions of platinum nanoparticles from platinous chloride (K₂PtCl₄) was achieved by simultaneous addition of capping polymer material. The size of platinum nanoparticles was controlled by changing the ratio of concentration of capping polymer material to the concentration of platinum cation used. The morphology of colloidal particles were studied by means of UV-visible spectrophotometry and transmission electron microscopy (TEM). Particle size increased with low reagent concentration. The change in absorption spectra with the particle size was observed, i.e. blue shift attributed to decrease in particle size Paper presented at the 5th IUMRS ICA98, October 1998, Bangalore.     

Catalytic activity of hybrid platinum nanoparticle-[C60]fullerene nanowhisker composites for 4-nitrophenol reduction

Abstract

Composites comprising platinum nanoparticles loaded on [C₆₀]fullerene nanowhiskers were prepared by a liquid-liquid interfacial precipitation method. The synthesized platinum nanoparticle-[C₆₀]fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites was confirmed for the reduction of 4-nitrophenol by UV–vis spectroscopy. The reduction of 4-nitrophenol catalyzed by the platinum nanoparticle-[C₆₀]fullerene nanowhisker composites followed the pseudo-first-order reaction rate law.     

Synthesis of core-shell nanostructures of Co3O4@SiO2 with controlled shell thickness (5-20 nm) and hollow shells of silica

Synthesis of uniform silica shell over Co3O4 nanoparticles was carried out using the colloidal solutions of Tergitol and cyclohexane. The shell could be controlled to a thickness of up to 20 nm by varying different parameters such as the amount of tetraethylorthosilicate, concentration of Co3O4 nanoparticles, reaction time and the presence of water and 1-octanol. Control of the amount of water (required for hydrolysis) appears to be the key factor for controlling the shell thickness. The methodology used is suitable to form shell over nanoparticles (present in powder form; synthesized at high temperature) which have high degree of agglomeration. Hollow shells of silica were obtained by the dissolution of the oxide core of Co3O4@SiO2 core-shell nanostructures. The composition of these core-shell nanostructures was confirmed by high-resolution transmission electron microscopy and elemental mapping by energy dispersive X-ray analysis. The hollow shells were characterized by using TEM, EDX and IR. Electron paramagnetic resonance studies of the core-shell nanostructures indicate the presence of free radicals on silica shell due to the presence of dangling bonds in the silica. Increase in the magnetic susceptibility was observed for these core-shell nanostructures.     

Ag3PO4/BigFe4O9复合催化剂的制备及其光催化性能

利用水热法成功地制备得到具有高效光催化活性的Ag3PO4/Bi2Fe4O9复合型光催化剂.使用X-射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对样品进行表征,并以罗丹明B为目标降解物对其光催化性能进行研究.结果表明:样品是由纳米Ag3 PO4颗粒负载在片状四边形的Bi2Fe4O9表面组成的,当Ag3PO4的负载量为4wt％时,复合材料的光催化效果最好,在可见光(波长＞420nm)照射下,1.5h内对100mL浓度为10-5mol.L-1罗丹明B溶液的脱色率可达98.7％.     

Oleic-acid-coated CoFe2O4 nanoparticles synthesized by co-precipitation and hydrothermal synthesis

Oleic-acid-coated CoFe₂O₄ nanoparticles were synthesized by co-precipitation and hydrothermal synthesis. The coprecipitation of the nanoparticles was achieved by the rapid addition of a strong base to an aqueous solution of cations in the presence of the oleic acid surfactant, or without this additive. The nanoparticles were also synthesized by a hydrothermal treatment of suspensions of the precipitates, coprecipitated at room temperature in the presence of the oleic acid, or without it. The influence of the synthesis conditions, such as the valence state of the iron cation in the starting aqueous solution, the temperature of the treatment and the presence of oleic acid, on the particles size was systematically studied. X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed that, although spinel forms at room temperature, a substantial amount of Co was incorporated within the secondary, feroxyhyte-like phase when the iron cation was in the 2+ state. In contrast, when iron was in the 3+ state, the spinel forms at elevated temperatures of approximately 60 °C. The presence of the oleic acid further increased the formation temperature for the stoichiometric spinel. Moreover, the oleic acid impeded the particles’ growth and enabled the preparation of colloidal suspensions of the nanoparticles in non-polar organic solvents. The nanoparticles’ size was successfully controlled by the temperature of the synthesis in the region where superparamagnetism dominates to the region where mono-domain ferrimagnetism dominates the magnetic properties.     

Deposition of platinum nanoparticles on carbon nanotubes by supercritical fluid method

Carbon nanotube-supported platinum nanoparticles with a 5-15 nm diameter size range can be synthesized by hydrogen reduction of platinum(ll) acetylacetonate in methanol modified supercritical carbon dioxide. X-ray photoelectron spectroscopy and X-ray diffraction spectra indicate that the carbon nanotubes contain zero-valent platinum metal and high-resolution transmission electron microscopy images show that the visible lattice fringes of platinum nanoparticles are crystallites. Carbon nanotubes synthesized with 25% by weight of platinum nanoparticles exhibit a higher activity for hydrogenation of benzene compared with a commercial carbon black platinum catalyst. The carbon nanotube-supported platinum nanocatalyst can be reused at least six times for the hydrogenation reaction without losing activity. The carbon nanotube-supported platinum nanoparticles are also highly active for electrochemical oxidation of methanol and for reduction of oxygen suggesting their potential use as a new electrocatalyst for proton exchange membrane fuel cell applications.     

磁性Fe3O4纳米颗粒的可控制备及生长研究

采用热法合成磁性Fe3O4纳米颗粒,通过精细调控实验条件能对其形状和大小进行有效控制。采用X射线衍射仪、透射电镜、振动样品磁强计等对Fe3O4纳米颗粒的成分、形貌及磁性等进行了表征测试。结果表明,Fe3O4纳米颗粒的饱和磁化强度为62.5emu/g。最后探讨了Fe3O4纳米颗粒的合成机理。     

Ferroxidase activity of apoferritin is increased in the presence of platinum nanoparticles

The ferroxidase activity of horse spleen apoferritin (HSAF) is increased by nine-fold in the presence of platinum nanoparticles. HSAF was mixed with varying concentrations of K2PtCl4 followed by a 20-fold concentration of sodium borohydride to afford Pt:HSAF nanoparticle complexes in a ratio of between 1:250 and 1:4000. Typical colour changes, from colourless or pale yellow to brown, occurred that were dependent on the amount of platinum present. These complexes were characterized by UV/vis, inductively coupled plasma optical emission spectroscopy, Fourier transform infrared, transmission electron microscopy and energy dispersive x-ray spectroscopy. Transmission electron microscopy analysis revealed that the size of nanoparticles increased as the molar ratio of platinum to HSAF increased with an average size diameter of 2-6 nm generated with HSAF:platinum molar ratios of 1:250-1:4000. Fourier transform infrared spectroscopy (FTIR) spectra showed no distinct changes in the structure of HSAF but confirmed that the nanoparticles were attached to the protein. The effect of platinum nanoparticles on the ferroxidase activity of HSAF showed a specific activity of 360 ρmol min(-1) mg(-1), (nine-fold increase over the control) at the molar ratio of HSAF:platinum nanoparticles of 1:1000.     

Preparation of nanocomposite materials from mercaptoacetate-modified platinum nanoparticles and a layered nickel hydroxyacetate salt

Nanocomposites were prepared by a very simple route from preformed platinum particles and a nickel layered hydroxide salt (LHS), these compounds being first synthesized separately by the polyol process. The nanoparticles were treated with mercaptoacetate before being brought into contact with the lamellar compound. XPS and IR spectroscopies give clear evidence for interactions between the platinum nanoparticles and the mercaptoacetate species. XRD, TEM and magnetic characterizations show that the structure of the nickel hydroxide layers is retained and that some of the LHS sheets contain incorporated nanoparticles.     

One-pot synthesis of AuPt alloyed nanoparticles by intense x-ray irradiation

We synthesized AuPt alloyed nanoparticles in colloidal solution by a one-pot procedure based on synchrotron x-ray irradiation in the presence of PEG (polyethylene glycol). The exclusive presence of alloyed nanoparticles with fcc structure was confirmed by several different experiments including UV-vis spectroscopy, x-ray diffraction (XRD) and transmission electron microscopy (TEM). The composition of the AuPt alloyed nanoparticles can be varied in a continuous fashion by simply varying the feed ratios of Au and Pt precursors. The nanoparticles exhibited colloidal stability and biocompatibility, important for potential applications.     

硬脂酸修饰LaPO4和Ce/LaPO4纳米微粒的制备及其摩擦学性能

采用共沉淀表面修饰法,制备了硬脂酸修饰LaPO4和Ce/LaPO4纳米微粒,用红外光谱仪、X射线衍射和透射电子显微镜对表面修饰纳米微粒的结构、形貌进行了表征,考察了表面修饰纳米微粒在溶剂中的分散性,利用四球试验机考察了表面修饰纳米微粒的摩擦学性能,并用扫描电镜对钢球磨斑表面形貌进行了分析.结果表明,硬脂酸修饰LaPO4...     

高纯ZnAl_2O_4纳米颗粒的制备及其微结构分析

将机械力化学与超声波化学相结合制备出高纯度、结晶性良好的尖晶石型ZnAl_2O_4纳米颗粒。分析了样品的表面形貌、晶体结构及微观结构。研究结果表明:当焙烧温度为600~900℃时,ZnO与γ-Al_2O_3固相反应制备出高纯度、结晶性良好的尖晶石型ZnAl_2O_4纳米颗粒。随着焙烧温度的升高,材料的致密度增大,结晶度提高,平均孔径依次增大,比表面积明显下降,孔隙率降低。     

静电纺丝法制备PAN/Fe3O4磁性纳米纤维

采用化学共沉淀法制备纳米四氧化三铁,选用曲拉通X-100为分散剂,利用静电纺丝法制备PAN/Fe3O4磁性纳米复合材料。X射线衍射仪(XRD)验证了四氧化三铁在复合纳米纤维中的存在。同时使用扫描电镜(SEM)和透射电镜(TEM)对复合纳米纤维的微观形貌和Fe3O4在纤维中的分布进行了观察,利用热重(TGA)对纳米复合材料的热稳定性进行分析;通过磁性实验分析了纳米复合材料的磁性性能。结果表明,所制备PAN/Fe3O4磁性纳米纤维成型良好,且Fe3O4磁性颗粒在纤维中分散均匀,其与PAN是物理复合。纳米复合材料具有一定磁性,并可由磁性颗粒的加入量进行控制。     

纳米金的制备及在化妆品中的应用初探

采用柠檬酸钠还原氯金酸制备纳米金,利用X射线荧光能谱和透射电子显微镜对产品进行了表征,通过纳米金溶胶及溶胶中含有的柠檬酸钠和保护剂PVP对Hela细胞、CHO细胞的MTT试验,研究了纳米金溶胶及纳米金颗粒对细胞的毒性,结果表明,纳米金溶胶和纳米金颗粒对这两种细胞均没有产生毒性。将纳米金加入到化妆品基础配方中制备得到了稳定的乳状液,为纳米金用于高级化妆品可行性提供部分实验依据。     

Sphere-like kesterite Cu2ZnSnS4 nanoparticles synthesized by a facile solvothermal method

In this paper, sphere-like kesterite Cu₂ZnSnS₄ (CZTS) nanoparticles were successfully synthesized by a facile solvothermal method. The CZTS nanoparticles with diameter range of 100-150 nm were agglomerated by CZTS nanocrystals. The as-obtained CZTS nanoparticles were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission election microscopy (TEM), Energy Dispersive Spectrometry (EDS) and UV-vis spectroscopy. Texture structures with kesterite crystallinity were reflected from the X-ray diffraction of 112, 200 and 312 planes of the CZTS nanoparticles. The UV-vis absorption spectra showed that CZTS nanoparticles had strong absorption in the visible light region. The observed band gap of 1.48 eV matched well with the bulk CZTS material that was optimal for solar cells.     

Cu2ZnSnS4纳米颗粒及其薄膜的制备与表征

采用热注入法,在油胺(OLA)中合成出Cu2ZnSnS4(CZTS)纳米颗粒,并在玻璃衬底上制备了薄膜,研究了不同合成温度对纳米颗粒生成的影响.通过X射线衍射仪、拉曼光谱仪、透射电子显微镜、扫描电子显微镜、紫外可见分光光度计对所得纳米晶材料的结构与成分、颗粒大小与形貌、光吸收谱进行了测试分析.研究结果表明:采用热注入法的最佳合成温度在260℃左右,该温度下生成的多晶CZTS纳米颗粒尺寸约10 nm,分散性良好,光学禁带宽度约1.5 eV.     

反应条件对CoFe2O4颗粒形貌、粒径大小和磁性的影响

以FeSO4（NH4）2SO4、6H2O、CoCl2·6H2O、C6H5Na3O7·2H2O为前驱物,采用水热法合成了钴铁氧体CoFe2O4。用XRD、TEM、VSM分别测试了CoFe2O4颗粒大小、形貌、饱和磁化强度和矫顽力,探讨了反应时间、温度、溶质浓度、酸碱环境对颗粒粒径大小、形貌及其磁性能的影响。结果表明,适度的减短反应时间、降低温度、选取合适的溶质浓度和NaOH溶液浓度,可以得到粒径小、形貌统一的纳米颗粒,并且有助于增大CoFe2O4颗粒的饱和磁化强度。     

Microwave-assisted hydrothermal synthesis and characterizations of PrF3 hollow nanoparticles

PrF₃ hollow nanoparticles were synthesized by the microwave-assisted heating hydrothermal treatment of the corresponding colloidal rare earth fluorides precipitates. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The TEM imaging showed that the PrF₃ nanoparticles prepared in this way had hollow sphere-like morphology with the mean particle size of about 31 nm. XRD showed that the PrF₃ hollow nanoparticles had high purity and high crystallinity.     

超顺磁性纳米Fe3O4的热分解法制备及表征

以单甲氧基聚乙二醇、对甲苯磺酰氯、邻苯二甲酰亚胺钾等为原料,根据盖布瑞尔合成法原理,合成了一端为氨基的单甲醚聚乙二醇(mPEG-NH2)。并以其为还原剂,聚乙二醇(PEG)为溶剂,利用热分解法制备了水分散性的超顺磁性纳米Fe3O4。采用红外光谱(FT-IR)、X射线衍射(XRD)、透射电镜(TEM)、热重分析(TG)、超导量子干涉仪(SQUID)和纳米粒度与Zeta电位分析仪等测试技术对其性能进行表征,实验结果表明,所制得的纳米Fe3O4粒子结晶度高,粒度均匀,分散良好,平均粒径为(12.2±1.6)nm,具有超顺磁性,饱和磁化强度为54 emu/g,在中性水溶液中其表面带正电,Zeta电位为+33 mV。TG测试结果表明,Fe3O4纳米粒子表面有机物的含量约为28%,Fe3O4的产率为57%左右。     

Synthesis and characterization of ZnO/MgO solids prepared by deposition of preformed colloidal ZnO nanoparticles

The ZnO/MgO solids were prepared by colloidal technique which involves the deposition of preformed colloidal ZnO nanoparticles on magnesia. The morphology of ZnO nanoparticles was investigated by transmission electron microscopy and UV-Vis absorption and diffuse reflectance spectroscopy. We found a good agreement between the average radius and the particle size distribution of the ZnO nanoparticles obtained by both methods. It was shown the ability to control the size of the supported ZnO nanoparticles (3.8-4.4nm) by varying pH of the colloidal solution.