Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Cracow, Poland.
J Colloid Interface Sci. 2010 May 15;345(2):187-93. doi: 10.1016/j.jcis.2010.01.073. Epub 2010 Feb 1.
Monodisperse silver particles were synthesized according to the method of Creighton et al. by reduction of AgNO(3) solutions with NaBH(4) in the presence of polyvinyl alcohol as the stabilizing agent. Bulk characteristics of silver nanoparticles in aqueous solutions were carried out by measuring their extinction spectrum, fluorescence, diffusion coefficients using the PCS method and the electrophoretic mobilities. The average hydrodynamic diameter of PVA covered silver particles was 44 nm, being fairly independent of ionic strength and pH in the range of 3-9. It was also shown that the hydrodynamic radius did not change within prolonged storage of suspensions (up to 75 days), indicating that the sols were quite stable. A similar value of 45±8 nm was determined from SEM measurements. The electrophoretic mobility measurements showed that the zeta potential of silver nanoparticles was insensitive to pH and decreased with the ionic strength, attaining -45 mV for I=10(-5) M and -25 mV for I=10(-2) M. Additionally, the kinetics of silver particle deposition on mica modified by adsorption of a saturated layer of poly(ethylene imine) (PEI) was studied. Surface concentration was determined directly by counting the number of particles over various surface areas using the atomic force microscopy working in the semicontact mode. The maximum surface concentration for I=10(-3)M was 102 μm(-2), which corresponds to the coverage degree of 16%. The kinetic run and the maximum coverage value was in a good agreement with theoretical predictions stemming from the random sequential adsorption (RSA) model. This kinetic run allowed one to determine the size of Ag core, which was 20 nm and the thickness of the PVA layer, equal to 12 nm.
根据 Creighton 等人的方法，通过在聚乙烯醇作为稳定剂的存在下用硼氢化钠还原硝酸银溶液来合成单分散银颗粒。通过测量其消光光谱、荧光、使用 PCS 方法测量扩散系数和电泳迁移率来研究水溶液中银纳米粒子的体相特性。用聚乙烯醇包覆的银颗粒的平均水动力直径为 44nm，在 3-9 的范围内相当独立于离子强度和 pH。还表明，在悬浮液的长时间储存（长达 75 天）中，水动力学半径没有变化，表明溶胶非常稳定。从 SEM 测量中确定了类似的 45±8nm 值。电泳迁移率测量表明，银纳米粒子的 ζ 电位对 pH 不敏感，并随离子强度降低，对于 I=10(-5)M 达到-45mV，对于 I=10(-2)M 达到-25mV。此外，还研究了通过吸附饱和层聚乙烯亚胺（PEI）来修饰云母的银颗粒的沉积动力学。通过在半接触模式下使用原子力显微镜在不同的表面积上计数颗粒数，直接确定表面浓度。对于 I=10(-3)M，最大表面浓度为 102μm(-2)，这对应于 16%的覆盖率。动力学运行和最大覆盖率与源自随机顺序吸附（RSA）模型的理论预测非常吻合。这种动力学运行允许确定 Ag 核的尺寸，该核的尺寸为 20nm，以及聚乙烯醇层的厚度，等于 12nm。
