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、沉积物和大气尘埃中发现了由化学风化和生物矿化反应形成的纳米尺度晶体。 由于纳米颗粒具有独特的尺寸依赖性，在环境过程中可能发挥着重要的作用。 然而，地质上重要的纳米材料的反应性与粒径的变化很少受到关注。 离子吸附到纳米晶金属氧化物表面上的趋势被预测为尺寸依赖性的。 将在0 - 150摄氏度的温度范围内对气体和与环境有关的水溶液中的吸附进行实验研究。 将开发模型，以定量解释纳米颗粒的结果和宏观等效物获得的结果之间的差异。 如果纳米晶体通过定向聚集体生长，如先前所示，吸附的离子（例如，从溶液吸附到羟基氧化铁表面上的磷酸盐、砷酸盐和锌）可以并入点缺陷中。 这可能是一个重要的环境离子螯合途径，与营养物质和污染物的长期命运直接相关。 在受控条件下的聚集和吸附的耦合也可以提供一种新的方法，用于产生具有技术上有趣的特性的合成材料。 纳米晶体生长过程中的离子螯合将通过实验进行测试，并通过分子建模和模拟进行探索。 量热研究旨在测量表面能和吸附能，将提供数据，用于模型，将探讨大小依赖的反应。 该提案是应“纳米科学与工程”（NSF 00-119）的要求提交的。

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).