Collaborative Research: NIRT: Surface Reactivity of Nanocrystalline Oxides and Oxyhydroxides: Implications for Processes in the Environment

在河流、湖泊、海洋、土壤、沉积物和大气粉尘中发现了由化学风化和生物矿化反应形成的纳米尺度的EAR-0123967EAR-123998EAR-0124036EAR-0124001Crystals。由于其新颖的大小依赖性质，纳米颗粒可能在环境过程中扮演非常重要的角色。然而，具有重要地质意义的纳米材料的反应性随颗粒大小的变化却很少受到关注。离子吸附在纳米晶金属氧化物表面的趋势被预测为与尺寸有关。将在0-150摄氏度的温度范围内对气体和与环境相关的水溶液的吸附进行实验研究。将开发模型来定量解释纳米颗粒和宏观等价物结果之间的差异。如前所述，如果纳米晶体通过定向聚集生长，被吸附的离子(例如，从溶液中吸附到氢氧化铁表面的磷酸盐、砷酸盐和锌)可能会被结合到点缺陷中。这可能代表了一条重要的环境离子隔离途径，与营养物质和污染物的长期命运直接相关。在可控条件下的聚集和吸附的耦合也可能为创造具有技术特性的合成材料提供一种新的方法。将对纳米晶体生长过程中的离子隔离进行实验测试，并通过分子建模和模拟进行探索。旨在测量表面能和吸附能的量热研究将为探索依赖于尺寸的反应性的模型提供数据。这项提案是应“纳米科学与工程”(NSF 00-119)的征集而提交的。

EAR-0123967EAR-123998EAR-0124036EAR-0124001Crystals with nanometer-scale dimensions formed by chemical weathering and biomineralization reactions are found in rivers, lakes, oceans, soils, sediments, and atmospheric dust. Because of their novel size-dependent properties, nanoparticles may play disprotionately large roles in environmental processes. However, the variation of reactivity of geologically important nanomaterials with particle size has received little attention. The tendency of ions to adsorb onto nanocrystalline metal oxide surfaces is predicted to be size-dependent. Adsorption will be studied experimentally over the temperature range of 0 - 150 degrees C in gases and environmentally-relevant aqueous solutions. Models will be developed to quantitatively explain differences between results for nanoparticles and those obtained on macroscopic equivalents. If nanocrystals grow via oriented aggregations, as has been shown previously, adsorbed ions (e.g. phosphate, arsenate, and zinc adsorbed from solution onto iron oxyhydroxide surfaces), may be incorporated into point defects. This may represent an important environmental ion sequestration pathway, with direct relevance to the long-term fate of nutrients and contaminants. Coupling of aggregation and adsorption under controlled conditions may also provide a new approach for creation of synthetic materials with technologically interesting properties. Ion sequestration during nanocystal growth will be tested experimentally and explored via molecular modeling and simulation. Calorimetric studies designed to measure surface and adsorption energies will provide date to be used in models that will explore size-dependent reactivity. This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119).