Imaging chemical reactions one molecule at a time

In this article, we focus on demonstrating the utility of scanning probe methods in the imaging of chemical reactions. We first highlight the utility of different imaging methods and highlight their advantages and drawbacks. Subsequently, we select a number of examples to illustrate different surface processes including adsorption, dissociation, diffusion and rotation of adsorbed molecules, formation of reaction intermediates, and conclude with complex reactions. In these examples, we mainly focus on the STM, which is most extensively employed as a method of choice. To limit the complexity of the article we have selected only a few systems for the discussion. In particular, elemental steps in the reactions of water, alcohols, and diols on TiO2(110) surface are utilized to illustrate the power of imaging techniques in our understanding of surface chemistry. We also provide a brief outlook on both current and future challenges in this exciting area of research