Phase controlled synthesis of bifunctional TiO nanocrystallites d-mannitol for dye-sensitized solar cells and heterogeneous catalysis.

The crystal architecture of TiO was successfully tailored a low-temperature (≤200 °C) hydrothermal process in the presence of d-mannitol for feasible applications in dye-sensitized solar cells (DSSCs) and heterogeneous catalysis. In the development of anatase-TiO (A-TiO), d-mannitol does not merely acts as a complexing agent to manage the zigzag chains of octahedral TiO with dominant edge sharing but also performs as a capping agent by influencing the hydrolysis process during nucleation, as confirmed by Fourier-transform infrared spectroscopy and dynamic light scattering studies. After physical measurements, the as-synthesized nanocrystallites (NCs) of A-TiO were used in DSSCs, where a fascinating power conversion efficiency (PCE) of 6.0% was obtained, which showed excellent performance compared with commercial anatase-TiO (CA-TiO: 5.7%) and rutile-TiO (R-TiO) obtained without d-mannitol (3.7%). Moreover, a smart approach was developed the A-TiO catalyst to synthesize pharmaceutically important C-3 alkylated 4-hydroxycoumarins through different activated secondary alcohols under solvent-free, and heat/visible light conditions. In addition, the catalytic activity of the so-produced A-TiO catalyst under solvent-free conditions exhibited remarkable recyclability with up to five consecutive runs with negligible reduction, which is superior to existing reports, and clearly reveals the novelty, and green, sustainable nature of the as-synthesized A-TiO catalyst. A plausible reaction mechanism of both coupling partners was activated through the interaction with the A-TiO catalyst to produce valuable C-3 alkylated 4-hydroxycoumarins with 95% yield and high selectivity.