Properties of shells and cores of fatty metal nanoparticles by means of electrochemical analysis

通过电化学分析研究脂肪金属纳米粒子的壳和核的性质

基本信息

批准号：
16550070
负责人：
CHEN Jingyuan
金额：
$ 2.37万
依托单位：
University of Fukui
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

项目摘要

The nanoparticles composed of a silver stearate-shell and a silver-core became metallic bulk silver by heating at temperature (340℃) lower than the melting point of silver metal (960℃). The nanoparticles decreased the mass by 20%, which was equivalent to the amount of the stearate shell. The low temperature metallization resulted from the thermal decomposition of the shell of silver stearate into silvers. It involved two steps. The first, occurring at 250℃, was the decomposition into porous silver particles through the first order reaction with an activation energy of 111 kJ mol^<-1>. The second, occurring at 340℃, was structure change from the porous particles into the silver bulk crystals.Spectroscopic, chemical, thermal, and voltammetric analyses on six kinds of alkylcarboxylates-stabilized silver nanoparticles 4.7nm in diameter were carried out with an aim to reveal the effect of alkylcarboxylates on the optical, thermal, geometric, and electrochemical properties of the nanoparticl … More es. These nanoparticles are composed of silver atoms and silver alkylcarboxylates having even numbers, m, of carbon atoms from 8 to 18. As a measure of the structure of the nanoparticles, the ratio of the number silver atoms (n_<Ag>) to that of alkylcarboxylates (n_s) per nanoparticle was evaluated by means of titration through chemical oxidation, voltammetric currents, and thermal gravimetric analysis. It increased with an increase in m and ranged from 1.3 to 9.8. Properties of the nanoparticle have been exhibited in absorbance of the UV-vis spectra at the point of the proportionality to n_<Ag>, voltammetric currents of which values were close to the theoretical values at the diffusion of particle itself, and the m-independent kinetic energy of the thermal decomposition and the overpotential of the reduction.Palladium spherical particles 0.23μm in diameter were synthesized by reducing palladium acetate with hydrazine in the presence of surfactant, aiming at exhibiting both easy separation by filtration and easy dispersion for a catalyst. The particles in the suspension were sedimented slowly but not aggregated. The suspension showed voltammetric redox waves. The anodic wave was ascribed to the oxidation of Pd to Pd^<2+>, whereas the cathodic one was to the reduction of the palladium acetate moiety to Pd. The current ratio of the anodic peak to the cathodic peak, 4:1, was close to the ratios by the partial chemical oxidation with permanganate and by the thermogravimetry, suggesting the composition of 80% palladium metal and 20% palladium acetate in the molar ratio. Heating of the palladium particles yielded palladium metal at 300℃. The particle catalyzed the reduction of methylene blue with hydrazine. The reaction rate was of the first-order with respect to methylene blue. The rate constant was proportional to the geometrical surface area of the palladium particle, suggesting a surface catalysis. Less

由银酸银壳和银核组成的纳米颗粒通过在温度（340℃）的加热（340℃）（960℃）的温度下加热（340℃），成为金属块。纳米颗粒将质量降低20％，相当于硬脂酸壳的量。低温金属化是由硬脂酸酯壳的热分解导致的。它涉及两个步骤。首先发生在250℃时，是通过一阶反应分解为多孔银颗粒，其活化能为111 kj mol^<-1>。 The second, occurring at 340℃, was structure change from the porous particles into the silver bulk crystals.Spectroscopic, chemical, thermal, and voltammetric analyses on six kinds of alkylcarboxylates-stabilized silver nanoparticles 4.7nm in diameter were carried out with an aim to reveal the effect of alkylcarboxylates on the optical, thermal, geometric, and纳米属性的电化学特性…更多。这些纳米颗粒由银原子和烷基羧酸盐组成，具有8至18的碳原子的数量，均匀数，是纳米颗粒的结构，数量银原子（N_ <ag>）的比率是通过滴定和滴定的剂量，并通过化学效率进行了评估，该数量银原子（N_ <ag>）与含量的含量（N_S）的比率。重量分析。它随着M的增加而增加，范围为1.3至9.8。纳米颗粒的特性已在与N_ <ag>比例的点吸收中吸收UV-VIS光谱，该值的伏安电流接近粒子本身的扩散和MM独立的动能的理论值接近于粒子本身的扩散和热分解的MM独立动能。通过在存在生存的情况下用氢嗪减少乙酸盐来合成，旨在表现出易于通过过滤和催化剂易于分散的易于分离。悬浮液中的颗粒被缓慢而不是聚集。悬浮液显示伏安氧化还原波。将阳极波分配给PD氧化为Pd^<2+>，而阴极的氧化是将乙酸钯部分的还原为PD。阳极峰与阴极峰4：1的电流比通过氧化剂和热重测定法接近比率，表明80％钯金属的组成和20％乙酸盐的组成。钯颗粒的加热在300°时产生钯金属。颗粒用氢嗪催化亚甲基蓝的还原。相对于亚甲基蓝的反应速率是一阶。速率常数与钯颗粒的几何表面积成正比，表明表面催化。较少的