Theoretical Understanding of Photo-induced Processes in Photocatalysis and Molecular-structured Solar Cell
Nobel laureates (1981), R. Hoffmann, and K. Fukui, taught us importance of the frontier molecular orbital (HOMO&LUMO) picture, i.e., molecular interactions and chemical reactions can be analyzed from the starting point of the electron energy levels of the electron donor (HOMO) and the electron acceptor (LUMO). The Woodward?Hoffmann rules were first formulated to explain the striking stereo-specificity of electro-cyclic reactions under thermal and photochemical control. As for the electron-transfer processes in the molecular systems, Nobel laureates (1992), R. A. Marcus developed “Marcus Theory” to explain the reaction rate at which an electron can move from the electron donor molecule to the electron acceptor molecule, and the theory evaluated photo-induced chemical reaction processes to notable extents.
On the other hands, Nobel laureate (1998), Walter Kohn shows that the energy of a quantum-mechanical system is uniquely determined by electron density on the basis of Density-functional Theory (DFT). DFT is more easily handled in computational calculations, giving reliable molecular modeling for the interacting molecules as results of their van der Waals and Coulomb interactions. In addition, P. Pople (Nobel laureate (1998)), and his colleagues (e.g., W. J. Hehre, WAVEFUNDTION Inc.) developed excellent computer programs for molecular orbitals of the molecule’s electron density and energy. It is worth noting to mention the Pople’s advice to W. J. Hehre; Pick the simplest model that describes the property of interest within or close to “chemical accuracy”. Recognize that there may be differences between what is measured and what is calculated, and also recognize errors measurements. More complicated models may make you feel better, but “Simpler is Better”. I also hear that Dr. Hehre appreciated the advice from R. Hoffman; “Pictures are better than words”.
With these advanced theoretical chemistry in mind, he is introducing the underlying molecular orbitals and their electron density concepts to understand, visualize and predict electronic molecular processes where photoactive and electro-active molecules play a crucial role.
He is now interested in the following topics,
- The quasi-photosynthetic process observed for solar-photolysis of p-benzoquinone and ethanol to respective hydroquinone and acetaldehyde.
- Instant photo-oxidation processes of C60 in the presence of O2
- Efficient Photo-reduction processes in the presence of p-terphenyl as a photocatalyst and triethylamine as a sacrificial electron donor.
- DFT-based understanding of unidirectional photoelectron transfer and transport processes using LUMO orbitals of the molecular device systems.