Department of Chemistry, Division of Engineering, Institute for Molecular and Nanoscale Innovation, Brown University, Providence, Rhode Island, USA.
Environ Sci Technol. 2010 Mar 15;44(6):2169-75. doi: 10.1021/es9035557.
Many important aspects of nanosilver behavior are influenced by the ionic activity associated with the particle suspension, including antibacterial potency, eukaryotic toxicity, environmental release, and particle persistence.The present study synthesizes pure, ion-free, citrate-stabilized nanosilver (nAg) colloids as model systems, and measures their time-dependent release of dissolved silver using centrifugal ultrafiltration and atomic absorption spectroscopy. Ion release is shown to be a cooperative oxidation process requiring both dissolved dioxygen and protons. It produces peroxide intermediates, and proceeds to complete reactive dissolution under some conditions. Ion release rates increase with temperature in the range 0-37 °C, and decrease with increasing pH or addition of humic or fulvic acids. Sea salts have only a minor effect on dissolved silver release. Silver nanoparticle surfaces can adsorb Ag(+), so even simple colloids contain three forms of silver: Ag(0) solids, free Ag(+) or its complexes, and surface-adsorbed Ag(+). Both thermodynamic analysis and kinetic measurements indicate that Ag(0) nanoparticles will not be persistent in realistic environmental compartments containing dissolved oxygen. An empirical kinetic law is proposed that reproduces the observed effects of dissolution time, pH, humic/fulvic acid content, and temperature observed here in the low range of nanosilver concentration most relevant for the environment.
许多关于纳米银行为的重要方面都受到与颗粒悬浮液相关的离子活性的影响，包括抗菌效力、真核毒性、环境释放和颗粒持久性。本研究合成了纯净的、无离子的、柠檬酸盐稳定的纳米银（nAg）胶体作为模型系统，并使用离心超滤和原子吸收光谱法测量了其随时间溶解银的释放情况。结果表明，离子释放是一个协同氧化过程，需要溶解的氧气和质子。它产生过氧化物中间体，并在某些条件下继续进行完全反应性溶解。在 0-37°C 的范围内，离子释放速率随温度升高而增加，随 pH 值升高或腐殖酸/富里酸的添加而降低。海盐水对溶解银的释放只有轻微的影响。纳米银颗粒表面可以吸附 Ag(+)，因此即使是简单的胶体也含有三种形式的银：Ag(0)固体、游离的 Ag(+)或其配合物以及表面吸附的 Ag(+)。热力学分析和动力学测量都表明，Ag(0)纳米颗粒在含有溶解氧的实际环境隔室中不会持久存在。提出了一个经验性的动力学定律，该定律再现了在这里观察到的溶解时间、pH 值、腐殖酸/富里酸含量和温度的影响，这在与环境最相关的低纳米银浓度范围内观察到。
