Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Environ Sci Technol. 2012 Jul 3;46(13):6992-7000. doi: 10.1021/es203732x. Epub 2012 Feb 29.
Sulfidation of metallic nanoparticles such as silver nanoparticles (AgNPs) released to the environment may be an important detoxification mechanism. Two types of AgNPs-an engineered polydisperse and aggregated AgNP powder, and a laboratory-synthesized, relatively monodisperse AgNP aqueous dispersion-were studied. The particles were sulfidized to varying degrees and characterized to determine the effect of initial AgNP polydispersity and aggregation state on AgNP sulfidation, and then exposed to Escherichia coli to determine if the degree of sulfidation of pristine AgNPs affects growth inhibition of bacteria. The extent of sulfidation was found to depend on the HS(-)/Ag ratio. However, for the same reaction times, the more monodisperse particles were fully transformed to Ag(2)S, and the polydisperse, aggregated particles were not fully sulfidized, thus preserving the toxic potential of Ag(0) in the aggregates. A higher Ag(2)S:Ag(0) ratio in the sulfidized nanoparticles resulted in less growth inhibition of E. coli over 6 h of exposure. These results suggest that the initial properties of AgNPs can affect sulfidation products, which in turn affect microbial growth inhibition, and that these properties should be considered in assessing the environmental impact of AgNPs.
金属纳米粒子（如银纳米粒子（AgNPs））的硫化可能是一种重要的解毒机制。研究了两种 AgNPs-一种工程化的多分散和聚集的 AgNP 粉末，以及一种实验室合成的、相对单分散的 AgNP 水基分散体。这些颗粒被硫化到不同程度，并进行了特征化，以确定初始 AgNP 多分散性和聚集状态对 AgNP 硫化的影响，然后暴露于大肠杆菌以确定原始 AgNPs 的硫化程度是否会影响细菌的生长抑制。发现硫化程度取决于 HS（-）/Ag 比。然而，对于相同的反应时间，更单分散的颗粒完全转化为 Ag2S，而多分散的、聚集的颗粒没有完全硫化，因此保留了聚集物中 Ag（0）的毒性潜力。硫化纳米颗粒中 Ag2S:Ag（0）的比值较高，导致大肠杆菌在 6 小时暴露期间的生长抑制较少。这些结果表明，AgNPs 的初始性质可以影响硫化产物，进而影响微生物的生长抑制，在评估 AgNPs 的环境影响时应考虑这些性质。
