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

提出的研究旨在加深对两种强大的合成方法的理解。首先，将挑战改良气凝胶工艺（MAP）。已遇到的显著溶剂效应将被科学地评估。在水解步骤中建立的平衡将通过所使用的金属离子（例如镁（2+）vs锌2+）的刘易斯酸度的变化来探测。还将评估脱水程序（真空与气体流动）的变化。本文将氧化锌（ZnO）、二氧化锆（ZrO2）、氧化镁（MgO）和氧化钙（CaO）作为模型。在这项工作的第二阶段，将用精心制定的标准化程序评估不同晶体形状的吸附行为。晶体形状对纳米晶固结的影响也将被研究。第二种合成方法，溶剂化金属原子/分子分散（气相沉积到冷溶剂中，然后控制聚集）将被分析。在这项工作中，选定的硫化物、硒化物和卤化物（硫化锌（ZnS）、硫化镉（CdS_）、硒化镉（CdSe）、硫化铅（PbS）、氟化锂（LiF）、氟化镁（MgF2）、氯化镁（MgCl2）和硫化锡（SnS））的纳米晶体将被研究。潜在的主题将是开发对这些强大的可扩展综合方法的理解和可预测性。此外，广泛的技术，创造性输入的机会和结果展示的机会将为实验室环境中的学生提供出色的培训，而实验室环境一直接受并鼓励高度多样化的男女组合。越来越多的证据表明，普通的类矿物物质，当以非常小的晶体形式（纳米晶体）产生时，与较大的晶体相比，具有非常不同的形状。这种差异对这些细粉状物质吸附有毒化学物质的能力有深远的影响。事实上，纳米晶体在吸附和解毒许多空气污染物、有毒工业化学品、化学战剂和细菌方面表现得非常出色。然而，生产这些有用的纳米晶体的方法在本质上大多是“炼金术”。通过研究不同的溶剂、温度、试剂浓度和其他关键特征，我们需要更好地了解这两种重要的合成方法。这项工作的基本主题将是为这些有趣和有用的纳米晶体材料的可扩展生产发展科学的理解和可预测性。此外，广泛的科学技术，创造性投入的机会，以及展示科学发现的机会，将使学生在一向鼓励男女高度多样化的实验室环境中得到良好的训练。

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.