In 1980 in collaboration with researchers at the NRC, we were the first to demonstrate the process of electronic energy pooling via molecular excited singlet-excited singlet annihilation in fluid media. In accord with our predictions, we have now found its triplet counterpart (triplet-triplet annihilation giving a highly excited singlet product) in an aromatic thione in solution at room temperature. These observations provide proof-of-concept for multiple photon energy capture and (temporary) storage in a highly excited molecule, and constitute both an opportunity for and a hitherto unrecognized efficiency limit on methods of solar energy conversion and storage, including those based on porhyrins and metalloporphyrins.

The laser chemistry group, in collaborations with colleagues, continues to seek practical applications of the results of its fundamental photophysical and spectroscopic investigations. To this end we have systematically investigated the spectroscopy and dynamics of pyrene-labeled synthetic polypeptides. Pyrene is frequently used as a fluorescent probe in biophysical studies of the binding of small peptides, but little attention has been paid to the effect of the tether used for attaching the pyrene label to the binding molecule. We have shown that the nature of the tether determines the excited state lifetimes and relaxation dynamics, and have discovered a useful empirical correlation between readily measurable absorption parameters of these pyrene-tethered compounds and their excited state lifetimes.