Chemistry Department, Florida Institute of Technology, 150 West University Boulevard, Melbourne, FL 32901, USA.
Sci Total Environ. 2012 Dec 15;441:277-89. doi: 10.1016/j.scitotenv.2012.09.055. Epub 2012 Nov 17.
The formation and characterization of AgNPs (silver nanoparticles) formed from the reduction of Ag⁺ by SRNOM (Suwannee River natural organic matter) is reported. The images of SRNOM-formed AgNPs and the selected area electron diffraction (SAED) were captured by high resolution transmission electron microscopy (HRTEM). The colloidal and chemical stability of SRNOM- and SRHA (Suwannee River humic acid)-formed AgNPs in different ionic strength solutions of NaCl, KCl, CaCl₂ and MgCl₂ was investigated in an effort to evaluate the key fate and transport processes of these nanoparticles in natural aqueous environments. The aggregation state, stability and sedimentation rate of the AgNPs were monitored by Dynamic Light Scattering (DLS), zeta potential, and UV-vis measurements. The results indicate that both types of AgNPs are very unstable in high ionic strength solutions. Interestingly, the nanoparticles appeared more unstable in divalent cation solutions than in monovalent cation solutions at similar concentrations. Furthermore, the presence of SRNOM and SRHA contributed to the nanoparticle instability at high ionic strength in divalent metallic cation solutions, most likely due to intermolecular bridging with the organic matter. The results clearly suggest that changes in solution chemistry greatly affect nanoparticle long term stability and transport in natural aqueous environments.
本文报道了由 SRNOM（苏湾河天然有机物）还原 Ag⁺形成的 AgNPs（银纳米颗粒）的形成和特性。通过高分辨率透射电子显微镜（HRTEM）捕获了 SRNOM 形成的 AgNPs 的图像和选区电子衍射（SAED）。在 NaCl、KCl、CaCl₂和 MgCl₂不同离子强度溶液中研究了 SRNOM 和 SRHA（苏湾河腐殖酸）形成的 AgNPs 的胶体和化学稳定性，以评估这些纳米颗粒在天然水相环境中的关键归宿和迁移过程。通过动态光散射（DLS）、zeta 电位和紫外-可见测量来监测 AgNPs 的聚集状态、稳定性和沉降速率。结果表明，两种类型的 AgNPs 在高离子强度溶液中都非常不稳定。有趣的是，与类似浓度的单价阳离子溶液相比，纳米颗粒在二价阳离子溶液中似乎更不稳定。此外，SRNOM 和 SRHA 的存在导致在二价金属阳离子溶液中高离子强度下纳米颗粒不稳定，这很可能是由于与有机物的分子间桥接。结果清楚地表明，溶液化学性质的变化极大地影响了纳米颗粒在天然水相环境中的长期稳定性和迁移。
