Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA.
Acc Chem Res. 2010 Sep 21;43(9):1205-15. doi: 10.1021/ar100011f.
Many emerging fields such as biotechnology and renewable energy require functionalized surfaces that are "smart" and highly stable. Surface modification schemes developed previously have often been limited to simple molecules or have been based on weakly bound layers that have limited stability. In this Account, we report on recent developments enabling the preparation of molecular and biomolecular interfaces that exhibit high selectivity and unprecedented stability on a range of covalent materials including diamond, vertically aligned carbon nanofibers, silicon, and metal oxides. One particularly successful pathway to ultrastable interfaces involves the photochemical grafting of organic alkenes to the surfaces. Bifunctional alkenes with a suitable functional group at the distal end can directly impart functionality and can serve as attachment points for linking complex structures such as DNA and proteins. The successful application of photochemical grafting to a surprisingly wide range of materials has motivated researchers to better understand the underlying photochemical reaction mechanisms. The resulting studies using experimental and computational methods have provided fundamental insights into the electronic structure of the molecules and the surface control photochemical reactivity. Such investigations have revealed the important role of a previously unrecognized process, photoelectron emission, in initiating photochemical grafting of alkenes to surfaces. Molecular and biomolecular interfaces formed on diamond and other covalent materials are leading to novel types of molecular electronic interfaces. For example, electrical, optical, or electromechanical structures that convert biological information directly into analytical signals allow for direct label-free detection of DNA and proteins. Because of the preferential adherence of molecules to graphitic edge-plane sites, the grafting of redox-active species to vertically aligned carbon nanofibers leads to good electrochemical activity. Therefore researchers could graft electrocatalytic materials to carbon nanofibers to develop new types of selective electrocatalytic interfaces. Extending this chemistry to include metal oxides such as TiO(2) may lead to highly specific and efficient chemical reactions and new materials with useful applications in photovoltaic and photocatalytic energy conversion.
许多新兴领域，如生物技术和可再生能源，都需要功能化的表面，这些表面既“智能”又高度稳定。以前开发的表面修饰方案往往局限于简单的分子，或者基于结合力较弱的层，其稳定性有限。在本报告中，我们介绍了最近的一些进展，这些进展使得能够制备在一系列共价材料（包括金刚石、垂直排列的碳纳米纤维、硅和金属氧化物）上表现出高选择性和前所未有的稳定性的分子和生物分子界面。一种特别成功的制备超稳定界面的方法涉及到有机烯烃的光化学接枝到表面。在远端具有合适官能团的双官能烯烃可以直接赋予功能，并可以作为连接复杂结构（如 DNA 和蛋白质）的连接点。光化学接枝在广泛的材料上的成功应用促使研究人员更好地理解其潜在的光化学反应机制。使用实验和计算方法进行的研究为分子的电子结构和表面控制光化学反应性提供了基本的见解。这些研究揭示了一个以前未被认识到的过程——光电子发射在引发烯烃向表面的光化学接枝中的重要作用。在金刚石和其他共价材料上形成的分子和生物分子界面正在导致新型分子电子界面的出现。例如，将生物信息直接转化为分析信号的电、光或机电结构允许对 DNA 和蛋白质进行直接无标记检测。由于分子优先附着在石墨边缘平面位，因此将氧化还原活性物质接枝到垂直排列的碳纳米纤维上会导致良好的电化学活性。因此，研究人员可以将电催化材料接枝到碳纳米纤维上，以开发新型的选择性电催化界面。将这种化学扩展到包括 TiO(2) 等金属氧化物可能会导致高度特异性和高效的化学反应以及具有有用应用的新型材料，如在光伏和光催化能量转换方面。
