Charge-transfer excitations and photoinduced injection in nasunin-Ag3 complexes adsorbed on metal-oxide semiconductors.

Novel optoelectronic systems are crucial for mitigating the environmental impact of energy production. To this end, we focus on the design of photosensitizers with strong one- and two-photon optical responses that also enable charge transfer at semiconductor interfaces. In this context, atomically precise noble metal nanoclusters (NCs) are employed in conjunction with the natural dye nasunin+, owing to their quantum-confined electronic structures and their ability to bridge macroscopic and nanoscale regimes. In particular, density functional theory (DFT) and its time-dependent extension (TDDFT) are used to investigate the electronic structure and optical and photovoltaic properties of the proposed nasunin-Ag3 bio-nano hybrid. Through metal-ligand hybridization, we demonstrate how the excited-state manifold can be tuned to achieve favorable energy level alignment and promote charge transfer. Furthermore, real-space grid-based DFT calculations of the TiO2-anchored system provide insight into the mechanism of photoinduced electron injection. These results offer a theoretical framework for the rational design of next-generation bio-NC sensitizers for solar energy conversion.