Speaker
Description
Hydrogen-bonded (H-bonded) molecular networks are ubiquitous in nature, appearing in systems such as DNA, proteins, and ice, to name a few. Achieving a comprehensive understanding of chemical reactions within these networks requires spatial resolution at the molecular level, which has been particularly challenging for photochemical studies. In this poster, we present our recent investigation into plasmon-induced localized reactions in two-dimensional H-bonded networks on surfaces using a laser-coupled scanning tunneling microscope (STM). We studied triphenylene-2,6,10-tricarboxylic acid (TTC) molecules, which form honeycomb network structures on Ag(111) at room temperature through hydrogen bonds of carboxylic groups. Our observations revealed that photo-induced deformation of the molecular network was highly localized to a few molecules directly beneath an Ag STM tip under visible laser illumination, with minimal impact on neighboring molecules. In contrast, a PtIr tip which lacks plasmonic activity in the visible range, failed to drive the reaction. This indicates that localized surface plasmon resonances at the STM junction play a critical role in the process. By varying the incident laser wavelength, we further examined the reaction mechanism, identifying it as being mediated by non-thermal electrons (hot electrons) generated by plasmons. This conclusion was corroborated by demonstrating the same reaction could be initiated by non-thermal electrons supplied by the STM tip without laser incidence. Our findings highlight the potential of plasmonic STM tips for precise control over the structure and reactivity of H-bonded assemblies.
