基于扫描光镊法的单颗粒光电化学活性成像研究

Conversion of solar energy to chemical bonds, for examples, the splitting of water, is a very promising solution to the emerging global energy crisis. The conversion efficiency is largely determined by the photoelectrochemical activity of nanostructured electrode materials used in cells. Traditionally, evaluating the activities involves depositing a great amount of nanoparticles on an electrode and measuring the response of the ensemble. Ensemble properties are largely influenced by the particle number and special distribution. In-depth understanding is thus suffered from these uncertainties in experiments. Therefore, developing new techniques that can directly reveal optoelectrochemical process on single nanoparticles is rather favorable. Herein, we propose a new approach towards single-particle studies on photoelectrochemical activities using scanning optical tweezers. In our approach, the gold nanoparticle manipulated by the optical tweezer acts as a nanosized plasmonic probe. When the gold nanoparticle is brought into the proximity of the semiconductor nanoparticle which is attached to the electrode, affected by the intense local electric field of the plasmonic gold nanoparticle, the rate of redox reaction in the semiconductor is greatly increased. The optoelectrochemical process can finally be revealed in a microscopic scale. Therefore, studies conducted using the proposed approach will break through size, refraction and detection limits. Systematic study is proposed to be carried out on the optoelectrochemical activities of individual semiconductor nanoparticles in the photolysis of water. It is focused on microscopic optoelectrochemical processes by means of in-situ measurements. Knowledges gained in this study will be of great significance in searching for ideal functional materials for optoelectrochemical applications.

光解水等将光能转换为化学能的方法是彻底解决全球能源危机的一个潜在途径，然而，其转换效率取决于所用纳米电极材料的光电化学活性。传统光电化学活性研究方法是基于对电极上大量颗粒进行的检测，受颗粒数和空间分布的干扰，很难对光电化学行为进行深入研究。因此，开发先进的技术手段对单个颗粒的光电化学过程进行直接测量，是当前亟需解决的问题。为此，我们提出将光镊扫描法用于单颗粒光电化学活性成像研究。我们将光镊俘获的金颗粒作为探针接近工作电极表面的待测颗粒，金颗粒局域表面等离子共振增强使得待测颗粒的氧化还原反应速率得到极大提升，从而得到单颗粒材料在微观尺度上的光电化学活性信息。本项目提出利用光镊扫描法突破传统宏观尺度限制，衍射极限和探测极限，针对光解水反应体系中单个半导体纳米颗粒结构的光电化学活性开展系统性研究，并对其微观光电化学机理过程进行原位研究。研究结果对于寻找理想的光电化学功能材料具有重要意义。

光解水等将光能转换为化学能的方法是彻底解决全球能源危机的一个潜在途径。然而，其转换效率取决于所用纳米电极材料的光电化学活性。传统光电化学活性研究方法是基于对电极上大量颗粒进行的检测，受颗粒数和空间分布的干扰，很难对光电化学行为进行深入研究。因此，开发先进的技术手段对单个颗粒的光电化学过程进行直接测量，是当前亟需解决的问题。为此，本项目提出将光镊扫描法用于单颗粒光电化学活性成像研究。在金属半导体核壳复合结构的构筑方面，本项目完成了二氧化钛，三氧化二铁，四氧化三铁和氧化钌对金纳米棒的直接包覆形成核壳结构；在平台构建方面，本项目完成了光镊步进扫描光电流探测系统；本项目最终利用此系统对金-二氧化钛光解水体系的光电流增强效应进行了原位研究。研究发现，贵金属纳米结构的表面等离激元热效应可以极大提升光解水反应的效率。研究结果对于构建理想的光电化学功能器件具有重要意义。