Attaching photochemically active ruthenium polypyridyl complex units to amorphous hydrogenated carbon (a-C:H) layers

Amorphous hydrogenated carbon (a-C:H) films are applied 500 nm thick on Si(100) via plasma-enhanced chemical vapor deposition (PECVD) using ethyne. Present plasma conditions enrich the sp(2)-content especially toward the outermost a-C:H layers, which in turn are used to attach a photoactive Ru-polypyridyl complex to the surface. An azo-bridged dinuclear Ru-polypyridyl complex is optimized in synthesis and the final mononuclear fragment attached on a-C:H photochemically under UV-irradiation with concomitant N-2 release. The Ru-polypyridyl complex is characterized by MS, NMR, IR, UV/vis, fluorescence spectroscopy, and time-dependent density functional theory (DFT) calculations. Crystallographic data for the intermediate 4-nitro-2-(pyridin-2-yl)pyridine 1-oxide as essential precursor are established. Morphological characteristics of the a-C:H @ Si and final Ru(complex) @ a-C:H @ Si combinations are determined by atomic force microscopy (AFM) revealing individual grain-like structures. The presence of Ru on the a-C:H @ Si surface is initially verified qualitatively by laser-induced breakdown spectroscopy (LIBS) and by inductively coupled plasma-sector field mass spectrometry (ICP-SF-MS) after chemical digestion. With laser ablation-ICP-MS mapping, full Ru coverage is proven, also revealing inhomogeneities in terms of "Ru hot spots". The current investigation proves the successful attachment of a Ru-complex on a-C:H and indicates a starting point for the development of further material combinations for feasible sunlight to energy conversions