Size and Shape of Small Crystals Affect Surface Chemistry and Consolidation. Rational Synthetic Methods

这项拟议的研究旨在加深对两种强大的合成方法的理解。首先，一种改进的气凝胶工艺(MAP)将受到挑战。将对所遇到的显著的溶剂效应进行科学评估。在水解步骤中建立的平衡将通过所用金属离子(例如，镁(2+)与锌(2+))的Lewis酸度的变化来探索。还将评估脱水程序(真空与气流)的变化。在这项工作中，将以氧化锌、二氧化锆、氧化镁和氧化钙为模型。在这项工作的第二阶段，将通过仔细制定的标准化程序来评估不同晶体形状的吸附行为。还将研究晶体形状对纳米晶固结的影响。第二种合成方法，溶剂化金属原子/分子分散(在冷溶剂中蒸气沉积，然后控制聚集)将被分析。在这项工作中，我们将研究一些硫化物、硒化物和卤化物的纳米晶体(硫化锌、硫化镉、硫化镉、硫化铅、氟化锂、氟化镁、氯化镁和硫化锡)。基本主题将是开发对这些可扩展的强大合成方法的理解和可预测性。此外，广泛的技术、创造性投入和展示结果的机会将使学生在实验室环境中得到极好的培训，实验室环境一直接受并鼓励高度多样化的我和女性的混合。证据表明，当以非常小的晶体形式(纳米晶体)生产时，常见的类似矿物的物质具有与较大晶体相比非常不同的形状。这种差异对这些细粉状物质吸附有毒化学物质的能力产生了深远的影响。事实上，纳米晶体已经被证明在吸附和解毒许多空气污染物方面非常好，有毒的工业化学品、化学战剂和细菌。然而，生产这些有用的纳米晶体的方法本质上大多是“炼金术”。为了通过研究不同的溶剂、温度、试剂浓度和其他关键特征来探索两种重要的合成方法，需要更好的理解。这项工作的基本主题将是发展对这些有趣和有用的纳米晶体材料的可规模生产的科学理解和可预测性。此外，广泛使用的科学技术、创造性投入的机会以及展示科学发现的机会将使学生在实验室环境中得到极好的培训，而实验室环境一直鼓励高度多样化的男女混合。

The proposed research aims to develop a deeper understanding of two powerful synthetic methods. First, a Modified Aerogel Process (MAP) will be challenged. Remarkable solvent effects that have been encountered will be scientifically assessed. Equilibria set up during the hydrolysis step will be probed by changes in the Lewis acidity of metal ions employed (e.g. magnesium (2+) vs zinc 2+)). Changes in dehydration procedures (vacuum vs gas flow) will also be assessed. In this work zinc oxide (ZnO), zirconium dioxide (ZrO2), magnesium oxide (MgO), and calcium oxide (CaO) will serve as models. In a second phase of this work, adsorption behavior of different crystal shapes will be assessed with carefully worked out standardized procedures. The effect of crystal shape on nanocrystal consolidation will also be studied. A second synthetic approach, Solvated Metal Atom/Molecule Dispersion (vapor deposition into cold solvents followed by controlled aggregation) will be analyzed. In this work nanocrystals of selected sulfides, selenides, and halides will be studied (zinc sulfide (ZnS), cadmium sulfide (CdS_, cadmium selinide (CdSe), lead sulfide (PbS), lithium fluoride (LiF), magnesium fluoride (MgF2), magnesium chloride (MgCl2), and tin sulfide (SnS). The underlying theme will be to develop understanding and predictability for these powerful synthetic methods that are scalable. In addition, the broad array to techniques, opportunities for creative input and opportunities for presentation of results will allow excellent training for students in laboratory setting that has always accepted and encouraged a highly diverse mixture of me and women.Evidence is accumulating that common mineral-like substances, when produced in very small crystalline form (nanocrystals), have very different shapes compared to larger crystals. This difference has profound effects on the ability of these fine powdery substances to adsorb toxic chemicals. In fact, nanocrystals have been shown to be extremely good at adsorbing and detoxifying many air pollutants toxic industrial chemicals, chemical warfare agents, and bacteria. However, the methods to produce these useful nanocrystals are mostly "alchemical" in nature. Better understanding is needed in order to probe two important synthetic methods by studying different solvents, temperatures, concentrations of reagents, and other key features. The underlying theme of the work will be to develop scientific understanding and predictability for scalable production of these interesting and useful nanocrystalline materials. In addition, the broad array of scientific techniques to be employed, opportunities for creative input, and opportunities for presentation of scientific findings will allow excellent training of students in a laboratory setting that has always encouraged a highly diverse mixture of men and women.