Measuring Hole Transfer across the Single Nanowire/Liquid Interface

半导体纳米线可以比一根头发细几千倍。这些极小的尺寸产生了独特的性能，可用于从发光二极管到太阳能转换设备的各种应用。然而，随着纳米线直径变得越来越小，纳米线表面的缺陷对电荷的捕获和器件性能的降低起着越来越大的作用。在化学系大分子、超分子和纳米化学项目的支持下，马里奥·阿尔普切教授正在研究溶液中纳米线和分子之间的光诱导电子转移。阿尔普切教授正在与他的学生合作，使用极小的电极来检测由单根纳米线吸收光产生的电流。他们的发现可能会对纳米材料在太阳能转换应用中的使用产生重要影响。此外，该项目正在扩大参与范围，通过参与整个内华达州北部的教育项目来招募拉美裔学生，美国和国外的合作激励来自代表性不足群体的学生追求化学职业。阿尔普切教授的研究小组正在开发新的方法来研究纳米线半导体表面的电荷转移。CdSe纳米线连接到超微电极上，用光激发，产生光生电子-空穴对。价带中的空穴可以从纳米线转移到溶液中的分子，或者被捕获在表面缺陷位置，而电子被转移到电极并作为光感应电流被检测到。光电流对电化学势和辐照功率的依赖使得空穴陷阱的贡献和电荷转移的贡献得以分离，而有限元模拟使得能够提取空穴转移出纳米线的速率常数。电化学仪器可以检测单个纳米线的光电流，使该小组能够研究整个结构中纳米线异质性的影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Semiconductor nanowires can be thousands of times thinner than a strand of hair. These extremely small sizes give rise to unique properties that can be harnessed for applications ranging from light emitting diodes to solar energy conversion devices. However, as the wire diameter gets smaller and smaller, defects at the nanowire surfaces, which trap charge and degrade device performance, play an ever-increasing role. With support from the Macromolecular, Supramolecular, and Nanochemistry program in the Division of Chemistry, Professor Mario Alpuche is studying the light-induced transfer of electrons between nanowires and molecules in solution. Working with his students, Professor Alpuche is using extremely small electrodes to detect the electrical current resulting from the absorption of light by a single nanowire. Their discoveries could have important implications for the use of nanomaterials in solar energy conversion applications. In addition, the project is broadening participation by recruiting students of Hispanic descent through engagement with educational programs throughout northern Nevada, and collaborations in the United States and abroad motivate students from underrepresented groups to pursue careers in chemistry.Professor Alpuche's research group is developing new methods to study charge transfer across the nanowire semiconductor surface. CdSe nanowires are attached to ultramicroelectrodes and excited with light, producing photogenerated electron-hole pairs. The hole in the valance band can be transferred from the nanowire to a molecule in solution, or trapped at surface defect sites, while the electron is transferred to the electrode and detected as a photoinduced current. The dependence of photocurrent on electrochemical potential and irradiation power enables a separation of the contribution of hole traps from that of charge transfer, and finite element simulations enable extraction of the rate constant for hole transfer out of the nanowire. The electrochemical instrumentation can detect photocurrent from individual nanowires, allowing the group to study the effects of nanowire heterogeneity across an ensemble of structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.