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

在低于金属银熔点（960℃）的温度（340℃）下加热，由硬脂酸银壳和银核组成的纳米粒子变成金属块体银。纳米颗粒的质量减少了20%，这相当于硬脂酸酯壳的量。硬脂酸银的壳层在低温下热分解成银，从而实现了金属化。它涉及两个步骤。第一个反应发生在250℃，是通过一级反应分解成多孔银颗粒，活化能为111 kJ mol^<-1>。第二个阶段是在340℃时发生结构变化，即由多孔颗粒转变为块状晶体.本文对六种不同的烷基羧酸盐稳定的直径为4.7nm的银纳米颗粒进行了光谱、化学、热学和伏安分析，旨在揭示烷基羧酸盐对纳米颗粒的光学、热学、几何和电化学性质的影响. ...更多信息 es.这些纳米颗粒由银原子和具有8至18的偶数碳原子m的烷基羧酸银组成。作为纳米颗粒结构的量度，<Ag>通过化学氧化滴定、伏安电流和热重分析来评估每个纳米颗粒的银原子数（n_）与烷基羧酸酯原子数（n_s）的比率。它随着m的增加而增加，范围从1.3到9.8。在<Ag>表面活性剂存在下，用肼还原醋酸钯，制备出了粒径为0.23μm的球形钯粒子，该钯粒子具有易于过滤分离和易于分散的特点。悬浮液中的颗粒缓慢沉降但不聚集。悬浮液显示伏安氧化还原波。阳极波归因于Pd氧化成Pd^&lt;2+&gt;，而阴极波归因于乙酸钯部分还原成Pd。阳极峰与阴极峰的电流比为4：1，与高锰酸盐部分化学氧化法和热重法的比值接近，表明组成为80%钯金属和20%乙酸钯的摩尔比。在300℃下加热钯颗粒得到钯金属。该粒子催化肼还原亚甲基蓝。反应速率是一级相对于亚甲基蓝。反应速率常数与钯粒子的几何表面积成正比，表明钯粒子具有表面催化作用。少

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