On-surface synthesis has attracted intensive attention in recent years due to its tremendous potential in fabrication of novel functional molecules and low-dimensional nanomaterials. In response to the demand for the synthesis of high-quality nanostructures, many efforts have been made to steer the reaction pathway and improve the chemo-/regio-selectivity, typically by smart precursor design and substrate templating effect. However, the precise control of the complex on-surface reactions with multiple pathways still remains challenging because only very few parameters can be tuned in the UHV environment in contrast to the traditional wet chemistry where various catalysts can be employed. In this presentation, I will report three typical coupling reactions, namely Ullman, Glaser and Sonagashira couplings, on the Ag(111) surface by using a single precursor molecule, i.e., 1,1’-biphenyl,4-bromo-4’-ethynyl (BPBE). By utilizing thermal stimuli procedures and kinetic strategies, the reactions of BPBE on Ag(111) can be efficiently steered towards the formation of cis-enediyne trimer, graphdiyne and graphyne nanowires. The reaction products and mechanism can be monitored and understood by the combination of scanning tunneling microscopy (STM), high resolution X-ray photoelectron spectroscopy (HRXPS) and density functional theory (DFT). I will show that the substrate temperature, annealing procedure, reactant concentration, molecular adsorption, desorption and diffusion all play important roles in the control of on-surface reactions. This work provides a fundamental insight of how to steer complex and multipath on-surface reactions towards the selected target products.

On-surface synthesis: strategies towards the targeted products

2019 Spring National Meeting

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