Cross-Linking of Ru(II) Polypyridyl Complexes Bearing Pyrrole Moieties on TiO₂ Nanoparticles to Enhance Light to Electricity Conversion

Abstract

Herein we report the synthesis and electrochemical and photophysical behaviors of a nanocomposite TiO 2 /P-[Rupyr] 2+ , where [Ru(bpy) 3 ] 2+ (bpy = 2,2′-bipyridine) cores bearing two pyrrole substituents on distinct bipyridines and a phosphonic anchoring group on the third bipyridine are immobilized on TiO 2 colloidal nanoparticles. Under visible light and in the presence of O 2 as a sacrificial electron scavenger, TiO 2 /P-[Ru-pyr] 2+ was converted into a suprastructure TiO 2 /P-oligo(Ru-pyr), where the [Ru(bpy) 3 ] 2+ cores were linked together through a pyrrole coupling reaction. The photoinduced charge separated state (e − )TiO 2 / Ru II -pyr + was revealed by electron paramagnetic resonance (EPR) spectroscopy ((e − )TiO 2 signal). The oxidative coupling of pyrroles was ascertained by identifying the additional organic radical EPR signal with DFT calculations of pyrrole-derived oligomers, combined with X-ray photoelectron spectroscopy (XPS) results. TiO 2 /P-oligo(Ru-pyr) exhibited a higher rate of electron injection from [Ru(bpy) 3 ] 2+ * to TiO 2 than for colloidal nanoparticules without pyrrole denoted as TiO 2 /P-[Ru] 2+ . The composites were then electrophoretically deposited on a fluorine-doped tin oxide surface and tested as photoanodes. At a bias of 0.12 V vs Ag/Ag + 0.01 M, FTO/TiO 2 /P-oligo(Ru-pyr) in the presence of tertiary amine as a sacrificial electron donor, displayed a current density double that of FTO/TiO 2 /P-[Ru] 2+ under similar conditions. XPS confirmed the stability of [Ru(bpy) 3 ] 2+ cores after the photopolymerization process, but a partial desorption was observed after the electrophoretic deposition.

Multimodal Biofilm Inactivation Using a Photocatalytic Bismuth Perovskite–TiO2–Ru(II)polypyridyl-Based Multisite Heterojunction

“…The Ti–O bond of TiO 2 and the hydroxyl groups are observed in the O 1s level with binding energies at 530 and 532 eV, respectively. Finally, the spectral features of Ru 3+ species in CBB/TiO 2 /RuPS are visible from the 3d 5/2 and 3d 3/2 spin-split doublet peaks at 281 and 285 eV, according to the sensitization of RuPS . The spectral patterns of CC/C–H, C C–N, and CO bonds of the polypyridyl Ru complex were also visible in their respective binding energies 284, 285, and 286 eV, respectively.…”

“…Finally, the spectral features of Ru 3+ species in CBB/TiO 2 /RuPS are visible from the 3d 5/2 and 3d 3/2 spin-split doublet peaks at 281 and 285 eV, according to the sensitization of RuPS. 35 The spectral patterns of C�C/C−H, C� C−N, and C�O bonds of the polypyridyl Ru complex were also visible in their respective binding energies 284, 285, and 286 eV, respectively. The 1 H-NMR spectrum registered for RuPS either alone or after CBB/ TiO 2 sensitization revealed the same pattern and preserves the molecularity of metal complex while forming a ternary junction (Figure S7).…”