Department of Environmental Engineering , National Cheng Kung University , Tainan City 701 , Taiwan.
USEPA Office of Research and Development, National Exposure Research Laboratory , Athens , Georgia 30605 , United States.
Environ Sci Technol. 2019 Oct 1;53(19):11162-11169. doi: 10.1021/acs.est.9b02115. Epub 2019 Sep 13.
In aerobic natural surface water, a silver ion (Ag) exists in various Ag-Cl complexes because of a strong affinity for a chloride ion (Cl); however, little information is available about the role of the Ag-Cl complex in the formation of silver nanoparticles (AgNPs). This study demonstrates that soluble AgCl species act as a precursor of AgNPs under simulated sunlight irradiation. The AgNP photoproduction increases with Cl levels up to 0.0025 M ([Ag] = 5 × 10 M) and decreases with continued Cl level increase (0.09 to 0.5 M). At [Cl] ≤ 0.0025 M (freshwater systems), photoproduction of AgNP correlates with the formation of AgCl, suggesting that it is the most photoactive species in those systems. Matching the ionic strength of experiments containing various Cl levels indicates that the trend in AgNP photoproduction correlates with Cl concentrations rather than ionic strength-induced effects. The photoproduction of AgNPs is highly pH-dependent, especially at pH > 8.3. The UV and visible light portions of the solar light spectrum are equally important in photoreduction of Ag. Overall, we show evidence that AgCl species irradiated under sunlight conditions contributes to the formation of nanosized silver (Ag) in the environment.
在有氧自然地表水中，由于银离子（Ag）对氯离子（Cl）具有很强的亲和力，因此以各种 Ag-Cl 络合物的形式存在；然而，关于 Ag-Cl 络合物在银纳米颗粒（AgNPs）形成中的作用的信息却很少。本研究表明，在模拟阳光照射下，可溶性 AgCl 物种可作为 AgNPs 的前体。随着 Cl 水平的增加（Ag 的浓度为 5×10-5 M），AgNP 的光生成量增加，当 Cl 水平继续增加（0.09 至 0.5 M）时，AgNP 的光生成量减少。在 [Cl]≤0.0025 M（淡水系统）时，AgNP 的光生成与 AgCl 的形成相关，表明在这些系统中它是最具光活性的物种。与含有不同 Cl 水平的实验的离子强度相匹配表明，AgNP 光生成的趋势与 Cl 浓度相关，而不是与离子强度诱导的效应相关。AgNPs 的光生成高度依赖于 pH 值，尤其是在 pH 值>8.3 时。太阳光光谱的紫外光和可见光部分在 Ag 的光还原中同样重要。总的来说，我们的研究结果表明，在阳光条件下照射的 AgCl 物种有助于环境中纳米级银（Ag）的形成。
