Hydrothermal synthesis and in situ surface modification of boehmite nanoparticles in supercritical water

In situ surface modification of boehmite (AlOOH) nanoparticles during hydrothermal synthesis in supercritical water was examined by adding CH₃(CH₂)₄CHO and CH₃(CH₂)₅NH₂ as modifier reagents to the reactants. Changes in surface properties of the nanoparticles by surface modification was observed by FTIR, dispersion in solvents and TEM analyses, which demonstrated that reagents chemically binded onto the surface of the AlOOH nanoparticles. The results of SEM and TEM pictures show that the surface modification affects crystal growth and reduces the particle size and changes the morphology of the particles.     

Synthesis and activation of Pt nanoparticles with controlled size for fuel cell electrocatalysts

Well-dispersed Pt nanoparticles with controlled size and narrow size distribution were prepared by polyalcohol reduction of platinum acetylacetonate, using oleylamine as a capping agent. The particle size was varied from 3.5 nm to 11.5 nm by decreasing the amount of oleylamine added in the synthesis. Size selection of the as-prepared particles by solvent fractionation yielded nearly monodispersed Pt particles. The as-prepared particles were loaded on a carbon support by physical deposition, but showed no electrocatalytic activity due to the oleylamine bound to the particle surface. The particles were activated for electrocatalysis after heating the particles in air at 185 °C for 5 h, conditions that gave no particle-sintering and no oxidation. Cyclic voltammetry showed that the particles after the heat treatment in air were electrocatalytically active for methanol oxidation. The smaller 3.5 nm and 4.0 nm Pt particles had a higher intrinsic activity for methanol oxidation, but a lower tolerance to CO poisoning, compared with 6.0 nm, 9.5 nm and 11.5 nm particles. CO-stripping results suggest that CO is more easily oxidized on larger Pt particles.     

Development of nano indium tin oxide (ITO) grains by alkaline hydrolysis of In(III) and Sn(IV) salts

Indium tin oxide (ITO) nano powders of different compositions (In: Sn = 90: 10, 70: 30 and 50: 50) were prepared by heat treatment (300-450°C) of mixed hydroxides of In(III) and Sn(IV). The hydroxides were obtained by the reaction of aq. NH₃ with mixed aq. solutions of In(NO₃)₃ and SnCl₄. FTIR and TG/DTA studies revealed that powders existed as In(OH)₃H₂O—SnO₃H₂H₂O in the solid state and then they transformed to In₂O₃—SnO₂ via some metastable intermediates after 300°C. Cubic phase of In₂O₃ was identified by XRD for the oxides up to 30% of Sn. Particle size measurements of the solid dispersed in acetone and SEM study for microstructure showed that the oxides were in the nano range (55-75 nm) whereas the size range determined from Debye-Scherrer equation were 11–24 nm.     

Origin of visible photoluminescence from porous silicon as studied by Raman spectroscopy

In this paper we discuss the different models proposed to explain the visible luminescence in porous silicon (PS). We review our recent photoluminescence and Raman studies on PS as a function of different preparation conditions and isochronal thermal annealing. Our results can be explained by a hybrid model which incorporates both nanostructures for quantum confinement and silicon complexes (such as SiH _x and siloxene) and defects at Si/SiO₂ interfaces as luminescent centres.     

Enhancement Effect of Gold Nanoparticles on the Bioactivity of Hydrogen-producing Microbe

1 IntroductionGold nanoparticles have attracted considerable atten-tionin manyfields duetotheir some special properties al-though goldis very popularfor beingchemicallyinert[1-3].For example ,gold nanoparticles as amplificationtags havebeenthe subject of research directed at gene analysis[4]and antibody or antigen detection[5-7]due to the large di-electric constant ,ease of preparation,andits biocompati-bility[8].Nanoparticles in the range of 1-10 nmin diameterwould display electronic structur…     

纳米镓/聚甲基丙烯酸甲酯复合材料的原位超声合成与表征

超声作用于低熔点金属镓,使其超细化为纳米级的镓粒子,并采用无引发剂的乳液聚合方法制备出GA/聚甲基丙烯酸甲酯(PMMA)纳米复合粒子,并分析了其微观结构。结果表明纳米镓的形态和结构因有无表面改性剂而不同;乳液聚合得到的纳米镓复合粒子是核壳结构型,粒子大小为50~80 NM,内核金属镓粒径为30~50 NM,与聚合物存在一定的化学作用。     

Surface modification of starch nanocrystals through ring‐opening polymerization of ε‐caprolactone and investigation of their microstructures

Bionanoparticles of starch obtained by submitting native potato starch granules to acid hydrolysis conditions. The resulted starch nanoparticles were used as core or macro initiator for polymerization of ε‐caprolactone (CL). Starch nanoparticle‐g‐polycaprolactone was synthesized through ring‐opening polymerization (ROP) of CL in the presence of Sn(Oct)₂ as initiator. The detailed microstructure of the resulted copolymer was characterized with NMR spectroscopy. Thermal characteristic of the copolymer was investigated using DSC and TGA. By introducing PCL, the range of melting temperature for starch was increased and degradation of copolymer occurred in a broader region. X‐ray diffraction and TEM micrographs confirmed that there was no alteration of starch crystalline structure and morphology of nanoparticles, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

溶胶-凝胶法制备纳米氧化锡及其性能表征

以SnCl4·5H2O为原料,采用溶胶-凝胶法制备了纳米SnO2粒子,研究了焙烧温度、碱的种类及反应物浓度对纳米SnO2粒子大小和分散状态的影响。采用XRD、TEM、ED等技术对SnO2纳米粒子的性能进行了表征。实验结果表明:用氨水和尿素作为沉淀剂,控制反应结束时pH值为7,在600℃焙烧,制备得到粒子尺寸约为15nm、分散性良好的纳米SnO2粒子。     

Anion Sensing Porphyrin Functionalized Nanoparticles

Disulfide and dithiocarbamate functionalized porphyrins have been synthesized and used as protecting ligands for gold nanoparticle formation either via ligand substitution reactions or by direct synthesis. These nanoparticles have been shown to recognize anions via changes in the absorbance spectrum of the surface adsorbed porphyrin moieties. Association constants, derived from quantitative titrations, indicate a remarkable surface enhancement effect where the surface bound porphyrins bind anions much more strongly than the free receptor in solution.     

Effect of composition on gelation kinetics of unfilled and nanoapatite-filled poly(lactide-ethylene oxide-fumarate) hydrogels

Oscillatory shear rheometry at small strains was used to investigate the effects of composition (concentration of macromer, crosslinker, initiator/accelerator, and filler) on the gel point and ultimate storage modulus of poly(l-lactide-co-ethylene oxide-co-fumarate) (PLEOF) hydrogels. PLEOF in situ polymerizing hydrogels can be used as biodegradable scaffolds for cell encapsulation and tissue regeneration. The time evolution of the viscoelastic properties of the polymerizing mixture during the sol-gel transition was monitored using mechanical rheometry. According to the results, while the ultimate storage modulus linearly increased with the concentration of methylene bisacrylamide (BISAM) crosslinker, the values of the storage and loss moduli at the gel point were insensitive to the concentration of BISAM. Similar behavior was observed for PLEOF hydrogels reinforced with hydroxyapatite nanoparticles.