Bren School of Environmental Science & Management, University of California, Santa Barbara, 3420 Bren Hall, Santa Barbara, California 93106-5131, USA.
Langmuir. 2010 Sep 7;26(17):13995-4003. doi: 10.1021/la1020516.
Engineered nanoparticles are used increasingly in numerous commercial products, leading to concerns over their environmental fate and ecotoxicity. We report the adaptation of colloid probe atomic force microscopy (AFM) to quantitatively determine the adhesive behavior of gold nanoparticles (Au NPs) with mica, chosen as a model for sand, in various water chemistries. Au NP-covered polystyrene (PS) beads were prepared by a combined swelling-heteroaggregation (CSH) technique prior to attachment to tipless AFM cantilevers. Force measurements were performed over a range of solution conditions (pH, ionic strength (IS), and natural organic matter (NOM) content). Plain PS beads with no Au NPs were used as controls. In general, adhesion of Au NP-PS beads to mica were found to increase as IS increased while a rise in pH led to a decrease in adhesion. Plain PS beads were not observed to adhere to mica in any of the experimental solution conditions, and the PS force curves were unaffected by changes in the pH and electrolyte concentrations. In the presence of NOM, pull-off forces for Au NP-PS beads increased in magnitude when NaCl was added. In addition, the experimental approach force curves were not successfully described by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. To reconcile the discrepancy between theory and experiment, an extended DLVO (xDLVO) empirical model was used to account for the contribution of non-DLVO interactions (known collectively as structural forces) between the Au NPs and mica surfaces.
工程纳米粒子在众多商业产品中被越来越多地使用，这引发了人们对它们在环境中的归宿和生态毒性的担忧。我们报告了胶体探针原子力显微镜（AFM）的适应性，用于定量确定金纳米粒子（Au NPs）与云母的粘附行为，云母被选为沙子的模型，在各种水化学条件下进行研究。Au NP 覆盖的聚苯乙烯（PS）珠粒是通过一种联合溶胀-异质聚集（CSH）技术制备的，然后将其附着在无尖端 AFM 悬臂上。在一系列溶液条件（pH 值、离子强度（IS）和天然有机物（NOM）含量）下进行了力测量。使用没有 Au NPs 的普通 PS 珠粒作为对照。一般来说，随着 IS 的增加，Au NP-PS 珠粒与云母的粘附力增加，而 pH 值的升高导致粘附力下降。在任何实验溶液条件下，普通 PS 珠粒都没有观察到与云母粘附，并且 PS 力曲线不受 pH 值和电解质浓度变化的影响。在 NOM 的存在下，当添加 NaCl 时，Au NP-PS 珠粒的脱附力会增加。此外，实验方法的作用力曲线不能用胶体稳定性的经典德加古因-朗道-维尔韦尔-奥弗贝克（DLVO）理论成功描述。为了调和理论与实验之间的差异，使用扩展的 DLVO（xDLVO）经验模型来解释 Au NPs 和云母表面之间的非 DLVO 相互作用（统称为结构力）的贡献。
