A new single pulse method for the measurements of photosensitized singlet oxygen quantum yield

Abstract

A new simpler relative method for estimating photosensitized singlet oxygen quantum yield has been developed. In this method a strong depletion signal is observed when porphyrin (2μ<i>M) </i>and l,3-diphenylisobenzofuran (DPBF, 500 μ <i>M) </i>are irradiated using second harmonic 532 nm Nd-YAG laser pulse and monitored at 410 or 415 nm by a ultraviolet filtered white light. The observed

depletion is attributed to the reaction of DPBF with sensitized singlet oxygen. The amplitude of the depletion signal is related directly to the singlet oxygen sensitization yield. Appropriate kinetic equations have been derived to relate the change in the absorbance of DPBF and singlet oxygen quantum yield. The

singlet oxygen quantum yields of fifteen porphyrins and metalloporphyrins have been investigated in dimethylformamide solution. The results are compared with the quantum yields obtained by the usual kinetic run experiments. The results are found to match exceedingly well in the two methods.