Structure, stability and catalytic activity of chemically synthesized Pt, Au, and Au-Pt nanoparticles

Small (1-5 nm) metallic nanoparticles of Pt, Au, and Au/Pt of different nominal compositions in colloidal form were synthesized by a chemical reduction method using polymer (PVP) as protecting agent. Analytical techniques like HREM and UV-vis spectroscopy have been used to characterize the morphology and structural properties of these small particles. Theoretical simulations based on molecular dynamical have been used to interpret the experimental structural results and analyze the macroscopic properties like stability and catalytic selectivity of these nanoparticles based on the morphology and atomic distribution in the clusters.     

Preparation and catalytic activity of Ni/CNTs nanocomposites using microwave irradiation heating method

Ni nanoparticles supported on carbon nanotubes were prepared by microwave-assisted heating hydrazine reduction in ethylene glycol. The Ni/CNTs nanocomposites by microwave-irradiation method (MIM-Ni/CNTs) were characterized by XRD, SEM, EDS and BET. The results indicated that MIM-Ni/CNTs had compact coating, high nickel loading and large BET surface area. The catalytic activity of obtained products on the thermal decomposition of ammonium perchlorate (AP) was carried out by DTA. The burning rate of the propellant modified by MIM-Ni/CNTs was measured by strand burner method. Moreover, the experimental results showed that the obtained products could play a catalytic role in the thermal decomposition of AP and combustion of AP-based propellant.     

凹凸棒土负载CeO2-La2O3复合材料制备表征及催化性能

以凹凸棒土(ATP)为载体, 以Ce(NO₃)₃·6H₂O和La(NO₃)₃·6H₂O为原料, 以C₆H₁₂N₄(HMT)为沉淀剂, 采用均相沉淀法制备了不同铈镧比的CeO₂-La₂O₃/ATP(Ce:La=9:1~3:7, 摩尔比, 下同)复合材料。用TG-DSC、 TEM、 XRD和FTIR对所制备复合材料的微观结构和形貌进行表征, 并分别考察不同铈镧比和H₂O₂添加量对酸性品红模拟废水脱色降解的影响。结果表明, 当Ce:La=5:5时, CeO₂-La₂O₃固溶体颗粒均匀分布在ATP表面, 颗粒尺寸为5~10 nm。随着铈镧摩尔比的增加, 酸性品红的降解率呈先增后减的趋势, 且当Ce:La=5:5、 H₂O₂为10 mL、 酸性品红浓度为100 mg/L时, 降解效果最好, 300 min后的最大降解率达82%。     

Au-Pt纳米颗粒/石墨烯-纤维素微纤维复合电极的制备与电化学性能

石墨烯和金属纳米是优异的导电纳米材料,为构建具有高效活性表面积的电化学传感界面,以玻碳电极作为导电基底,采用滴涂法结合一步电沉积成功制备了Au-Pt纳米颗粒/还原氧化石墨烯-纤维素微纤维(Au-Pt NPs/RGO-CMF)复合材料.SEM、原子力显微镜(AFM)、EDS和拉曼光谱分析表明,Au-Pt纳米颗粒均匀分布在...     

Silver/dendrimer nanocomposites as biomarkers: fabrication, characterization, in vitro toxicity, and intracellular detection

We have synthesized water-soluble, biocompatible, fluorescent, and stable silver/dendrimer nanocomposites that exhibit a potential for in vitro cell labeling. Amino-, hydroxyl-, and carboxyl-terminated ethylenediamine core generation 5 poly(amidoamine) dendrimers were utilized to prepare aqueous silver(I)-dendrimer complexes (with the molar ratio of 25 Ag+ per dendrimer) at the biologic pH of 7.4. Conversion of silver(I)-dendrimer complexes into dendrimer nanocomposites was achieved by irradiating the solutions with UV light to reduce the bound Ag+ cations to zerovalent Ag0 atoms, which were simultaneously trapped in the dendrimer network, resulting in the formation of {(Ag0)25-PAMAM_E5.NH2}, {(Ag0)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} dendrimer nanocomposites (DNC), respectively. The silver-DNCs were characterized by means of UV-vis, fluorescence spectroscopy, dynamic light-scattering, zeta potential measurements, high-resolution transmission electron microscopy, X-ray energy dispersive spectroscopy, and selected area electron diffraction. The cytotoxicity of dendrimers and related silver nanocomposites was evaluated using an XTT colorimetric assay of cellular viability. The cellular uptake of nanoparticles was examined by transmission electron and confocal microscopy. Results indicate that {(Ag0)25-PAMAM_E5.NH2}, {(Ag0-)25-PAMAM_E5.NGly}, and {(Ag0)25-PAMAM_E5.NSAH} form primarily single particles with diameters between 3 and 7 nm. The dendrimer nanocomposites are fluorescent, and their surface charge, cellular internalization, toxicity, and cell labeling capabilities are determined by the surface functionalities of dendrimer templates. The {(Ag0)25-PAMAM_E5.NH2} and {(Ag0)25-PAMAM_E5.NSAH} nanocomposites exhibit potential application as cell biomarkers.     

Synthesis, characterization, and catalytic application of highly ordered mesoporous alumina-carbon nanocomposites

Highly ordered mesoporous carbon-alumina nanocomposites (OMCA) have been synthesized for the first time by a multi-component co-assembly method followed by pyrolysis at high temperatures. In this synthesis, resol phenol-formaldehyde resin (PF resin) and alumina sol were respectively used as the carbon and alumina precursors and triblock copolymer Pluronic F127 as the template. N2-adsorption measurements, X-ray diffraction, and transmission electron microscopy revealed that, with an increase of the alumina content in the nanocomposite from 11 to 48 wt.%, the pore size increased from 2.9 to 5.0 nm while the ordered mesoporous structure was retained. Further increasing the alumina content to 53 wt.% resulted in wormhole-like structures, although the pore size distribution was still narrow. The nanocomposite walls are composed of continuous carbon and amorphous alumina, which allows the ordered mesostructure to be well preserved even after the removal of alumina by HF etching or the removal of carbon by calcination in air. The OMCA nanocomposites exhibited good thermostability below 1000 °C; at higher temperatures the ordered mesostructure partially collapsed, associated with a phase transformation from amorphous alumina into γ-Al₂O₃. OMCA-supported Pt catalysts exhibited excellent performance in the one-pot transformation of cellulose into hexitols thanks to the unique surface properties of the nanocomposite.     

Preparation and characterization of magnetic nanofibrous composite membranes with catalytic activity

Magnetic nanofibrous composite membranes were electrospun from the mixtures of poly(acrylonitrile-co-acrylic acid) (PANCAA) and Fe₃O₄ nanoparticles. Field emission scanning electron microscopy (FESEM) and thermal gravimetric analysis (TGA) were used to characterize the composite membranes. TGA results indicate that the addition of Fe₃O₄ nanoparticles catalyzes the carbonization of PANCAA as well as dramatically increases the carbonization temperature. The intrinsic peroxidase-like activity of Fe₃O₄ nanoparticles was measured by the color reaction of phenol/4-amino antipyrine in the presence of H₂O₂. Under optimal conditions, the electrospun composite membranes show high peroxidase-like catalytic activity and reusability. Taking into account of the potentiality for separation, these as-prepared magnetic nanofibrous composite membranes will be applied in phenolic wastewater treatment.     

Au/LaVO4 Nanocomposite: Preparation, characterization, and catalytic activity for CO oxidation

The size of the gold particles is a very important parameter to get active catalysts. This paper reports a novel colloidal deposition method to prepare Au/LaVO₄ nanocomposite catalyst with monodispersed Au colloids and uniform LaVO₄ nanoplates in nonpolar solvent. Monodispersed Au colloids with tunable size (such as 2, 5, 7, 11, 13, and 16 nm) and LaVO₄ nanocrystals with well-defi ned shapes were pre-synthesized assisted with oleic acid/amine. During the following immobilization process, the particle size and shape of Au and LaVO₄ were nearly preserved. As-prepared Au/LaVO₄ nanocomposite showed high catalytic activity for CO oxidation at room temperature. Since sizes of gold particles were well-defi ned before the immobilization process, size effect of gold particles was easy to be investigated and the results show that 5-nm Au/LaVO₄ nanocomposite has the highest activity for CO oxidation. This synthetic method can be extended further for the preparation of other composite nanomaterials.     

Preparation of platinum nanoparticle and its catalytic activity for toluene oxidation

Colloidal Pt nanoparticles are prepared using H2PtCl6 as a precursor, polyvinylpyrrolidone (PVP: molecular weight = 10,000 and 40,000) and hydrogen as a stabilizing agent and a reducing agent, respectively. The amounts of the precursor and the stabilizing agent and the molecular weight of PVP have an effect on the formation of Pt nanoparticles. Supported Pt catalyst (CSPt) is prepared from colloidal Pt nanoparticles and y-Al2O3. Another supported Pt catalyst (ISPt) is prepared by using the conventional incipient wetness impregnation method with an aqueous H2PtCl6 solution and gamma-Al2O3. The catalytic activities of CSPt and ISPt catalysts are compared for VOC (toluene) oxidation. Transmission Electron Microscopy (TEM), UV-vis, X-ray diffraction (XRD) and temperature programmed reduction (TPR) are used to characterize CSPt and ISPt catalysts. The experimental results reveal that the catalytic activity of CSPt is superior to that of ISPT.     

Keggin结构磷钼钒酸盐纳米催化剂的合成及其催化性能

采用室温固相反应法合成出 H3NiPMo10V2O40·5H2O的纳米催化剂,用元素分析、IR、XRD、TEM等手段确定其组成、结构和性能,同时考察了其用于苯 过氧化氢直接羟化合成苯酚反应的催化活性和机理。结果表明产物仍保持杂多阴离子的 Keggin结构,晶粒尺寸约为 31nm,比表面积为 138m2 ·g-1。在催化苯羟基化的反应中,活性中心是钒的过氧化物,苯酚收率>50%,选择性>98%。     

Green strategy of scaleably synthesizing copper nanocomposites with remarkable catalytic activity for wastewater treatment

The functional copper nanocomposites (Cu NCs) have received increasing attention in the environmen-tal catalysis application for wastewater treatment due to their superior catalytic activity and reactivity.However,overcoming the pH limitations towards the neutral and alkaline wastewater remains a tricky challenge.In this work,we demonstrate a green strategy to synthesize Cu NCs with coexistence of active Cu,Cu2O and ZrO2 by self-propagating combustion of metallic glassy ribbons,which exhibit the extremely superior catalytic performance for degradation reaction,providing full conversion of organic dyes com-pletely to the environmental friendly small species (efficiency ＞ 99％) under acidic,neutral and alkaline conditions.Compared with all other catalysts developed thus far,the novel Cu NCs catalysts with more active sites present much enhanced catalytic capability of degradation efficiency without the use of any chemical reagents for neutral and alkaline organic dye solutions.The possible decomposition pathways of organic dyes for different pH systems were systematically investigated.More importantly,the two kinds of catalytic mechanism related to high reactivity of nanoscale Cu/Cu2O and strong oxidizing capability of activated.OH/·O2-radicals can also be successfully confirmed under different pH conditions.The green synthetic approach can be extended to design the various M-based nanocomposites (M =Fe,Co,Ni,Ag,Pd) as efficient catalysts for the functional applications of many chemical reactions.     

Structural characterization and catalytic activity of Pt dendrimer encapsulated nanoparticles supported over Al2O3 for SCR of NOx

Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.     

Preparation of CuO nanopowders and their catalytic activity in photodegradation of Rhodamine-B

CuO nanopowders have been successfully synthesized in two different morphologies from same precursor using a facile gel to crystalline (reflux) and co-precipitation synthesis routes. SEM and TEM observations indicate that the morphology of the products depends on preparation technology, while XRD shows the formation of CuO nanocrystals with monoclinic crystal system in both cases. A comparison of morphological characterization of CuO nanopowders showed flower-like and aggregated nanoparticles in the form of clusters using reflux and co-precipitation techniques, respectively. Photocatalytic activity of the products in the aqueous solution of Rhodamine-B has been investigated under UV-light for a given time using UV–visible spectroscopy and the mineralization of organic substance was measured by total organic carbon (TOC) analysis. It was observed that the photocatalytic activity in the presence of flower-like CuO nanopowders was higher than that of observed with aggregated nanoparticles. Also the mechanisms for the formation of CuO nanopowders and the obtained results of photocatalytic degradation of Rhodamine-B are discussed.     

核壳型纳米Au@Ag复合材料的制备、催化及光抑菌

以纳米Au为核,在其表面负载Ag合成核壳型纳米Au@Ag复合材料,利用TEM、EDX、UV-Vis对材料进行表征。以甲基橙为目标污染物研究材料的催化加氢活性,并初步探讨其催化机制;用革兰氏阴性菌大肠杆菌(E.coli)和革兰阳性菌金黄色葡萄球菌(S.aureus)为模式菌研究材料的光抑菌活性和抑菌机制。结果表明,相比纳米Ag,纳米Au@Ag在8 min内对甲基橙的降解率为99%以上,加氢产物为对氨基苯磺酸钠和对二氨基苯;抑菌实验证明：相比黑暗环境中,300 W光照下的纳米Au@Ag具有更强的抑菌性能,在浓度为300μg/mL,光照10 min下的抑菌效率更高,并对细菌的迟缓期和对数期的生长阶段作用较为明显,对E.coli的细胞壁破坏较为严重。     

Preparation, structure and properties of uniaxially oriented polyethylene-silver nanocomposites

Uniaxially oriented composites of high-density polyethylene and silver nanoparticles were prepared using solution-casting, melt-extrusion and solid-state drawing techniques. The absorption spectrum in the visible wavelength range of the drawn nanocomposites was observed to strongly depend on the polarisation direction of the incident light. For instance, the nanocomposites appear bright yellow or red when the vibration direction of linearly polarised light is perpendicular or parallel, respectively, to the drawing axis. The optical anisotropy of the drawn nanocomposites originates from uniaxially oriented, pearl-necklace type of arrays of nanoparticles of high aspect ratios. The absorption spectrum of the nanocomposites can be shifted to higher wavelengths using appropriate annealing procedures. The annealing results in an increased size of the primary silver particles, due to Ostwald ripening, and consequently a range of polarisation-dependent colours can be generated in the drawn nanocomposites.     

磁性荧光纳米复合粒子的制备及其表面生物功能化

用化学共沉淀法制备了四氧化三铁(Fe3O4)纳米粒子,Stober法在其表面包裹SiO2并复合荧光标记物FITC,EDC偶联牛血清白蛋白(BSA)。采用扫描电子显微镜(SEM),傅里叶变换红外光谱仪(FT-IR),荧光分析仪,电子能谱(XPS)等对复合粒子进行了表征。结果表明,复合粒子保留了FITC的荧光特性、Fe3O4的磁响应性并成功接枝蛋白分子。生物功能化磁性荧光复合纳米粒子有望广泛应用于细胞标记、荧光追踪、磁性分离等领域。     

Thermally tunable catalytic and optical properties of gold-hydrogel nanocomposites

We have developed a very simple approach for preparing physically embedded gold cores in a temperature-responsive hydrogel polymer nanoparticle under fluorescent light irradiation. The complete encapsulation of the multiple gold core nanoparticles is confirmed by the catalytic reduction of 4-nitrophenol, whose reactivity is significantly retarded above the lower critical solution temperature (LSCT) due to the deswelled polymer structure; its increased hydrophobicity slows the access of hydrophilic reactants to the cores. Since these gold cores are physically embedded in the polymer nanoparticles, further growth of the cores is reliably achieved in situ under light irradiation. Interestingly, the resulting composite nanoparticles exhibit reversible solution color changes as well as absorption bands from the visible to near-IR regions below and above the LSCT.