Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, Missouri 63130, USA.
Environ Sci Technol. 2010 Nov 1;44(21):8182-9. doi: 10.1021/es101491e.
The early development of nanoparticles at mineral-water interfaces exerts crucial influences on the sequestration and transport of aqueous toxic species originating from both natural and anthropogenic sources. Homogeneous and heterogeneous nucleation often occur simultaneously, making it difficult to sort out whether toxic species are transported as free species, sorbed on nanoparticle surfaces, or trapped between aggregated nanoparticles. Here, using a newly developed X-ray scattering setup, we show how homogeneous nucleation and growth can be quantitatively separated from heterogeneous processes under aqueous conditions in real-time. Under conditions found in acid-mine-drainage (at pH 3.6 and [Fe(3+)] = 10(-4) M), heterogeneous nucleation of iron oxide nanoparticles on quartz dominated homogeneous nucleation by a factor of 192 (by particle volume). The smallest heterogeneously formed nanoparticles had radii of 1.7 ± 0.5 nm, significantly smaller than the size estimated using classical nucleation theory (CNT). Based on the data, the dominant nucleation and growth mechanisms of iron oxide nanoparticles depending on ionic strength were presented. Our findings have implications for the formation and transport of nanoparticles, and thus toxins, in both environmental and biological systems.
在矿泉水界面，纳米颗粒的早期发育对源自天然和人为源的水有毒物种的隔离和传输施加了关键影响。均相成核和异相成核通常同时发生，难以理清有毒物种是作为游离物种、被吸附在纳米颗粒表面还是被困在聚集的纳米颗粒之间进行传输。在这里，我们使用新开发的 X 射线散射装置，实时展示了在水相条件下如何从异质过程中定量分离均相成核和生长。在酸性矿山排水（在 pH 值为 3.6 和 [Fe(3+)]=10(-4) M）的条件下，石英上氧化铁纳米颗粒的异相成核是均相成核的 192 倍（按颗粒体积计）。最小的异质形成的纳米颗粒的半径为 1.7 ± 0.5nm，明显小于使用经典成核理论（CNT）估计的尺寸。基于这些数据，提出了氧化铁纳米颗粒的主导成核和生长机制取决于离子强度。我们的发现对环境和生物系统中纳米颗粒的形成和传输以及因此对毒素的形成和传输具有重要意义。
