Research
Catching ultrafast photochemical reaction in real-time
Nonadiabatic molecular dynamics are essential in many photochemical reactions. Nonadiabatic effects become prominent at conical intersections (CIs), where two or more electronic surfaces become energetically degenerate and the electronic and nuclear degrees of freedom are strongly coupled.
Due to the strong electron−nuclear coupling at the crossing region, CIs provide an effective ultrafast nonradiative electronic decay channel for excited molecules. They play a key role in many chemical and biophysical processes, such as internal conversion, charge transfer, photoisomerization, and photodissociation.
Probing and characterizing CIs are essential for understanding and controlling photochemical reactions. Despite the many attempts, the direct unambiguous experimental observation of CI in molecules is still an open challenge. Spectroscopic techniques that probe an intrinsic property of CI, such as electronic coherence and the vanishing transition energy, are in demand. Our group pursues to find a way to understand photochemical processes by using quantum chemistry and multidimensional spectroscopy and to control the chemical reactivity in these processes by using quantum optical approaches.
(* Highlighted on the cover of J. Phys. Chem. Lett.)
Nanostructuring photocatalytic nanoparticles
Titanium dioxide (TiO2) is widely studied by theory and experiment both with respect to its fundamental properties and from a more applied perspective. The applications of TiO2 in photocatalysis constitute a particularly active field of research, because of the possibility of generating H2 from water splitting under light irradiation. Because of the rather large band gap of the most common polymorphs of titania (anatase and rutile), photocatalytic water splitting using these materials requires ultraviolet (UV) radiation. This feature inhibits their practical use under sunlight as only ∼10% of the sunlight incoming photons have enough energy to be absorbed and, hence, participate in the photocatalytic process.
Nanostructuring has been used to modify the photocatalytic activity of TiO2. Of particular relevance to our study, techniques have been developed for control of the shape and size of titania nanoparticles in order to optimize them for photoactivity. Our group pursues to find a way to understand and enhance the photocatalytic activity of nanoparticles.
