Atomically Defined Photoswitchable Hybrid Nanostructures Built from Functionalized Norbornadienes and Cobalt Oxide Nanoislands on Au(111)

Le résumé fourni par la source

Organic photoswitches on surfaces enable the construction of interfaces that can store solar energy (molecular solar thermal systems, MOST) or change their functional properties in response to light (photoresponsive interfaces). However, many photoswitches show significantly altered photoresponsive behavior when anchored to metallic surfaces. To enable knowledge-based design of light-sensitive interfaces from prefabricated building blocks, it is essential to electronically decouple the light-sensitive unit from the rest of the system, for example by anchoring it to oxide islands that spatially separate the molecule from the catalytic active metal surface. In this work, we investigate the photoswitching behavior of a norbornadiene-based photoswitch, 2-cyano-3-(4-carboxyphenyl)norbornadiene (CNBD), anchored via a carboxylate linker to atomically defined CoO nanoislands on Au(111). Using infrared reflection absorption spectroscopy (IRAS) and scanning tunneling microscopy (STM), we investigate the adsorption and photoconversion behavior of these hybrid systems. CNBD selectively adsorbs on the CoO islands and forms self-organized monolayers (SAMs). Time-resolved photochemical IRAS shows that the activation barrier for the thermal back-conversion of anchored CNBD on the ultrathin CoO islands is comparable to that on thick oxide layers and of the free (non-anchored) molecule. This finding shows that a single Co-O bilayer is sufficient to decouple the CNBD from the underlying catalytically active Au(111). These findings pave the way for the knowledge-based design of photoswitchable nanostructures with atomic precision and predictable light sensitivity.

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