Thioflavin-T binds to and detects amyloid fibrils via fluorescence enhancement. Using a combination of linear dichroism and fluorescence spectroscopies, we report that the relation between the emission intensity and binding of thioflavin-T to insulin fibrils is nonlinear and discuss this in relation to its use in kinetic assays. We demonstrate, from fluorescence lifetime recordings, that the nonlinearity is due to thioflavin-T being sensitive to self-quenching. In addition, thioflavin-T can induce fibril compaction but not alter fibril structure. Our work underscores the photophysical complexity of thioflavin-T and the necessity of calibrating the linear range of its emission response for quantitative in vitro studies.

Solar energy has the potential of providing the world with clean and storable energy. In principle, solar fuels can be generated by light absorption followed by primary charge separation and secondary charge separation to reaction centres. However this comes with several challenges, including the need for long-lived charge separation and accumulation of several charges. This Feature Article focuses on how to achieve long-lived charge separation in dye sensitized semiconductor assemblies and the way towards multi-electron transfer through conduction band mediation, aiming at solar fuel generation. Herein, we discuss various examples of how the charge separated lifetime can be extended and potential ways of achieving one or multiple electron transfer in these assemblies.

Singlet fission has emerged as a promising way to overcome the Shockley–Queisser limit in solar energy conversion devices, and a few studies have claimed proof-of-principle results using dye-sensitized photoelectrodes. However, a detailed understanding of what factors govern the fate of the excited state on mesoporous surfaces is still lacking. Here, we have studied how the excitation progresses into singlet fission, electron injection, or formation of molecular charge separated states in diphenylisobenzofuran derivatives with flexible carbon linkers attached to nanocrystalline mesoporous ZrO2, TiO2, and SnO2 thin films. We show that singlet fission occurs for the molecule attached to ZrO2 films when the assembly is immersed in nonpolar solvents, and that singlet fission is hampered by the formation of a molecular charge separated state in more polar solvents. On TiO2 surfaces, direct electron injection from the singlet excited state outcompetes the singlet fission. Instead, triplet formation occurs via charge recombination from the conduction band of TiO2 in nonpolar solvents. When the molecule is attached to SnO2 films, singlet fission partly outcompetes electron injection from the singlet excited state and the two processes occur in parallel. Subsequent to singlet fission on SnO2, triplet injection into the conduction band of SnO2 is observed. The results presented here provide a detailed picture of the singlet fission dynamics in molecules attached to mesoporous semiconductor surfaces, demonstrating that both the semiconductor substrate as well as the environment around the molecules have a large impact, which can be useful in the design of future devices.

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Three homoleptic ruthenium(II) complexes, 3 ] 2+ , [Ru(Q1Pz) 3 ] 2+ , and [Ru(DQPz) 2 ] 2+ , based on the quinoline−pyrazole ligands, Q3PzH (8-(3-pyrazole)-quinoline), Q1Pz (8-(1-pyrazole)-quinoline), and DQPz (bis(quinolinyl)-1,3-pyrazole), have been spectroscopically and theoretically investigated. Spectral component analysis, transient absorption spectroscopy, density functional theory calculations, and ligand exchange reactions with different chlorination agents reveal that the excited state dynamics for Ru(II) complexes with these biheteroaromatic ligands differ significantly from that of traditional polypyridyl complexes. Despite the high energy and low reorganization energy of the excited state, nonradiative decay dominates even at liquid nitrogen temperatures, where triplet metal-to-ligand-charge-transfer emission quantum yields range from 0.7 to 3.8%, and microsecond excited state lifetimes are observed. In contrast to traditional polypyridyl complexes where ligand exchange is facilitated by expansion of the metal−ligand bonds to stabilize a metal-centered state, photoinduced ligand exchange occurs in the bidentate complexes despite no substantial MC state population, while the tridentate complex is extremely photostable despite an activated decay route, highlighting the versatile photochemistry of nonpolypyridine ligands.