Department of Health Science and Clothing Environment, Faculty of Human Life and Environment, Nara Women's University, Nara 630-8506, Japan.
Langmuir. 2010 Dec 7;26(23):17896-905. doi: 10.1021/la102705h. Epub 2010 Nov 3.
Formation mechanisms of silver (Ag) particles in an aqueous ethanol solution of poly(N-vinyl-2-pyrrolidone) (PVP) by the photoreduction of AgClO(4) were investigated by means of in situ small-angle X-ray scattering (SAXS) measurements. The kinetics of association process (nucleation, growth, and coalescence) of Ag(0) atoms to produce Ag particles was successfully revealed by the quantitative SAXS analysis for the number-average of radius (R(0)), number of particles (n(Ag)), reduced standard deviation (σ(R)/R(0)), and volume fraction (ϕ(Ag)) of Ag particles produced by the photoreduction. The rate of nucleation and growth process during Ag particle formation strongly depend on the initial metal concentration. The time evolution of radius and number of Ag particles indicates that a mechanism of Ag particle formation is composed of different three processes, that is, reduction-nucleation, Ostwald ripening, and particle coalescence. In a rapid reduction-nucleation process, small nuclei or particles (average radius ∼2.5 nm) are produced by an autocatalytic reduction. After the formation of small nuclei or particles proceeds, Ostwald ripening and particle coalescence, predicted by the Lifshitz-Slyozov-Wagner theory (LSW theory), subsequently occur, resulting in the particle growth (average radius ∼11.5 nm).
通过原位小角 X 射线散射（SAXS）测量研究了在聚（N-乙烯基-2-吡咯烷酮）（PVP）的水乙醇溶液中通过 AgClO4 的光还原形成银（Ag）颗粒的形成机制。通过对通过光还原生成的 Ag 颗粒的数均半径（R0）、颗粒数（n（Ag））、还原标准偏差（σ（R）/ R0）和体积分数（φ（Ag））的定量 SAXS 分析，成功揭示了 Ag（0）原子聚集过程（成核、生长和聚结）的动力学。Ag 颗粒形成过程中的成核和生长速率强烈依赖于初始金属浓度。Ag 颗粒半径和数量的时间演化表明，Ag 颗粒形成的机制由不同的三个过程组成，即还原成核、奥斯特瓦尔德熟化和颗粒聚结。在快速还原成核过程中，通过自动催化还原产生小核或颗粒（平均半径约为 2.5nm）。小核或颗粒形成后，随后发生奥斯特瓦尔德熟化和颗粒聚结，导致颗粒生长（平均半径约为 11.5nm），这是由 Lifshitz-Slyozov-Wagner 理论（LSW 理论）预测的。
