ToF-SIMS study of selective anchoring of Ru(tpy)(2) complexes on zirconium-phosphate functionalized oxide surfaces

Polypyridine-based ruthenium complexes are among the most interesting photoactive molecular systems, in virtue of a number of outstanding (photo)physicochemical properties. To exploit such properties in solid-state applications, such as molecular electronics, optoelectronics, and photovoltaics, tailored experimental strategies are needed for the anchoring of such complexes on surfaces. At the same time, these strategies need to be investigated and validated through precise monitoring of the surface composition. In this contribution, the authors report on the application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) for studying the anchoring onto transparent (semi)conducting fluorine tin-doped oxide of the polypyridinic photoactive RuDT2. This molecule is characterized by an Ru(tpy)(2) core and two free terpyridinic units. The authors' approach involves the use of a surface priming strategy based on the chemistry of zirconium phosphates and phosphonates (ZP-priming) to provide a platform for direct anchoring of RuDT2 molecules at the oxide surface. Onto patterned ZP-fluorine-doped tin oxide (FTO), the authors report selective anchoring of RuDT2 only onto ZP domains, while no binding occurs onto bare FTO areas. The latter were shown to remain available for further functionalization using functional molecules containing phosphonic moieties, and in the authors' case, a phosphonic derivative of rhodamine B (RhB-P) was used. ToF-SIMS imaging was intensively used to monitor each reaction step and confirm the successful laterally resolved and selective adsorption of RuDT2 and RhB-P onto ZP and bare FTO domains, respectively.