Na Chongzheng, Martin Scot T
School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Environ Sci Technol. 2009 Jul 1;43(13):4967-72. doi: 10.1021/es900500k.
Nanostructures grown under natural conditions can modify the layout of adhesion on mineral surfaces. Using force-volume microscopy and a silicon-nitride probe, we measure changes in adhesion when a patchy overgrowth of manganese oxide nanostructures forms on the surface of rhodochrosite. For the most part, the observations show that the adhesive force to the nanostructures is dominated by van-der-Waals attraction. Measurements made across an area of the surface provide a frequency distribution of adhesive forces, and the mode of this distribution is 166 pN at pH 5.0, increasing to a maximum of 692 pN at pH 7.1, followed by a decrease to 275 pN at pH 9.7. At a few sampling locations over some nanostructures, electrostatic repulsion overtakes van-der-Waals attraction and thus results in negative adhesive forces (i.e., repulsion). Local roughness causes this effect. In comparison to the oxide nanostructures, the exposed rhodochrosite substrate has negligible adhesive force with the probe over the same pH range, suggesting both weak van-der-Waals attraction and weak electrostatic repulsion over this pH range. The quantitative mapping of adhesive force applied more generally to the study of other nanostructures can lead to an improved mechanistic understanding of how nanostructure growth influences contaminant immobilization and bacterial attachment.
在自然条件下生长的纳米结构可以改变矿物表面的粘附布局。我们使用力体积显微镜和氮化硅探针，测量当菱锰矿表面形成氧化锰纳米结构的斑块状过度生长时粘附力的变化。在大多数情况下，观察结果表明，对纳米结构的粘附力主要由范德华引力主导。在表面区域进行的测量提供了粘附力的频率分布，该分布的众数在pH 5.0时为166 pN，在pH 7.1时增加到最大值692 pN，随后在pH 9.7时降至275 pN。在一些纳米结构上的几个采样位置，静电排斥超过范德华引力，从而导致负粘附力（即排斥）。局部粗糙度导致了这种效应。与氧化物纳米结构相比，在相同pH范围内，暴露的菱锰矿基底与探针的粘附力可忽略不计，这表明在该pH范围内，范德华引力和静电排斥都很弱。更广泛地将粘附力定量映射应用于其他纳米结构的研究，可以提高对纳米结构生长如何影响污染物固定和细菌附着的机理理解。
