Collaborative Research: New Routes for the Preparation and Characterization of Functionally-Graded and Mesoporous Silica Thin Films

堪萨斯州立大学的Daniel A.Higgins教授和弗吉尼亚联邦大学的Maryanne M.Collinson教授得到了分析和表面化学计划的支持，以探索新型介孔薄膜的合成和性质。含有成分梯度的薄膜和表面的制备是当代科学感兴趣的话题。这种“功能梯度”材料结合了极性、孔隙率和离子中心密度的梯度，可用作分离的固定相、用于化学或生物传感器的吸收/吸附层、作为调节细胞表面黏附、指导神经元生长、甚至驱动液体传输的手段。在这项合作提案中，正在研究一种独特的方法，利用溶胶-凝胶化学和现代电化学沉积技术来创建包含厚度、孔隙率和成分梯度的二氧化硅薄膜。这些材料的内在复杂性和多变性启发了单分子成像和光谱学(SMS)的使用，以获得纳米级和分子级的详细信息。将开发SMS方法，以获得关于孔大小和微环境极性沿梯度变化的信息。除了这些新的功能梯度材料外，还将制备因干燥或溶液性质变化而表现出可逆收缩的介孔材料，并在单孔水平上对其进行表征。表现出可逆收缩和膨胀的材料可能有助于污染物的捕获和隔离以及药物、杀虫剂和化肥的受控释放。新的单分子荧光共振能量转移(FRET)方法将被用来监测这些具有纳米级灵敏度的材料的孔径变化。在堪萨斯州立大学和弗吉尼亚联邦大学参加这项研究的学生将获得在合成、材料科学和单分子光谱学方面不同寻常的广泛经验。参与这项研究的所有参与者都将受益于该计划提供的全面教育，方法是在每周的网络会议上分享知识、数据和材料，并定期对合作实验室进行现场访问。

Professor Daniel A. Higgins of Kansas State University and Professor Maryanne M. Collinson of Virginia Commonwealth University are supported by the Analytical and Surface Chemistry Program to explore the synthesis and properties of novel mesoporous films. The preparation of films and surfaces incorporating compositional gradients is a topic of contemporary scientific interest. Such "functionally graded" materials incorporating gradients in polarity, porosity, and ionic site density have potential applications as stationary phases for separations, as absorbent/adsorbent layers for use in chemical or biological sensors, and as a means to regulate surface adhesion of cells, to direct the growth of neurons, and even to drive the transport of liquids. In this collaborative proposal, a unique approach is being studied for creating silica films that incorporate gradients in thickness, porosity, and composition using sol-gel chemistry and contemporary electrochemical deposition techniques. The inherent complexity and the variable nature of these materials inspired the use of single molecule imaging and spectroscopy (SMS) to obtain detailed information at the nanoscale and molecular level. SMS methods will be developed to obtain information on variations in pore size and microenvironment polarity along the gradients. In addition to these new functionally graded materials, mesoporous materials that exhibit reversible shrinkage in response to drying or changes in solution properties will also be made and characterized at the single pore level. Materials that exhibit reversible shrinking and expansion are potentially useful for the capture and sequestration of pollutants and for the controlled release of drugs, pesticides and fertilizers. Novel single-molecule fluorescence resonance energy transfer (FRET) methods will be used to monitor pore size variations in these materials with nanometer-scale sensitivity. Students participating in this research at Kansas State and Virginia Commonwealth will receive an unusually broad experience in synthesis, materials science and single molecule spectroscopy. All the participants involved in this research will benefit from the comprehensive education provided by this program via the sharing of knowledge, data and materials in weekly web conferences and periodic site visits to the collaborating laboratories.