High-Resolution Nanoelectrochemistry

化学反应涉及将一个电子从金属转移到吸附在其表面的分子，这是化学中最重要的一些反应，因为它们构成了从催化到传感的各种应用的基础。然而，对这些电化学反应的研究是具有挑战性的。例如，催化反应可能涉及多个电子的转移，而反应效率可能高度依赖于分子吸附物附近金属原子的局部排列。传统的电化学技术对整个金属电极进行采样，其中可能包含大量纳米级的金属特征，因此很难在局部金属结构和化学活性之间建立明确的联系。在这项由化学系化学结构动力学和机理(CSDM-A)计划资助的项目中，纽约城市大学皇后学院的迈克尔·米尔金教授正在推进纳米电化学方法，并利用它们来研究金属纳米颗粒和纳米棒表面发生的催化反应。与传统的电化学技术不同，米尔金教授和他的学生使用的扫描电化学显微镜(SECM)方法可以监测仅有10纳米宽的表面区域，或者说大约相当于30个金原子。这种高空间分辨率使该团队不仅可以表征单个粒子，还可以表征同一粒子的不同部分。他们的结果可能会对从超灵敏探测器的开发到能量转换和存储的催化等领域产生广泛的影响。该项目还为研究生和本科生提供了培训机会，他们正在获得界面电化学、生物分析化学和纳米科学方面的多学科研究经验。纳米电化学技术，如稳态伏安法、SECM和纳米粒子碰撞，与高分辨率隧道电子显微镜和有限元模拟相结合，研究在纳米尺度上影响电化学事件检测的基本过程。该项目正在研究微观碳腔中的电化学过程，电子在金属纳米颗粒和电极之间的长距离转移，以及催化活性金属纳米棒周围表面反应性的空间变化。通过两种方法研究了单个纳米颗粒与纳米电极之间的相互作用。在第一种方法中，SECM纳米针尖被带到单个纳米粒子的隧道距离内，并检测隧道电流，而第二种方法在纳米粒子与电极碰撞时监测电子隧道效应。主要目标是为复杂纳米电化学系统的机械研究和可视化开发实验和理论框架。该奖项反映了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。

Chemical reactions that involve the transfer of an electron from a metal to a molecule adsorbed to its surface are some of the most important in chemistry, as they form the basis for applications ranging from catalysis to sensing. The study of these electrochemical reactions is challenging, however. Catalytic reactions for example can involve the transfer of multiple electrons, and reaction efficiency can be highly dependent on the local arrangement of metal atoms near the molecular adsorbate. Traditional electrochemistry techniques sample the entire metal electrode, which can contain a vast number of nanoscale metallic features, making it difficult to draw clear connections between the local metal structure and the chemical activity. In this project funded by the Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division, Professor Michael Mirkin of the City University of New York, Queens College is advancing nanoelectrochemical methods and using them to study catalytic reactions taking place on the surfaces of metallic nanoparticles and nanorods. Unlike traditional electrochemistry techniques, the scanning electrochemical microscopy (SECM) method used by Professor Mirkin and his students can monitor a region of the surface that is only 10 nm across, or about the equivalent of 30 gold atoms. This high spatial resolution enables the team to characterize not just individual particles, but different sections of the same particle. Their results could have broad implications for fields ranging from the development of ultrasensitive detectors, to catalysis for energy conversion and storage. The project is also providing training opportunities for graduate and undergraduate students, who are getting multidisciplinary research experience in interfacial electrochemistry, bioanalytical chemistry and nanoscience.Nanoelectrochemical techniques, such as steady-state voltammetry, SECM, and nanoparticle collisions, are combined with high-resolution tunneling electron microscopy and finite-element simulations to study the fundamental processes that impact the detection of electrochemical events on nanometer length scales. The project is investigating electrochemical processes in microscopic carbon cavities, long-distance transfer of electrons between metal nanoparticles and electrodes, and spatial variations in surface reactivity around catalytically active metallic nanorods. The interactions between single nanoparticles and nanoelectrodes are investigated by two approaches. In the first, the SECM nanotip is brought to within the tunneling distance of a single nanoparticle, and the tunneling current is detected, while the second approach monitors electron tunneling as nanoparticles collide with the electrode. The main objective is to develop the experimental and theoretical framework for mechanistic studies and visualization of complex nanoelectrochemical systems.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.