Measurement of fluorescent quantum yield using photothermal deflection spectroscopy

Photothermal deflection spectroscopy (PDS) is technique best known for its ability to measure weak optical absorptions various media. In this presentation we demonstrate an extended application for PDS, namely, measurement of the fluorescent quantum yield (Φ_f) of fluorophores. Starting from first principles of energy conservation, a simple model for the photothermal deflection spectrum as a function of Φ_f is fit to the spectral data using Φ_f as a single fitting parameter. Using this method, extracted values of Φ_f for standard fluorophores such as Rhodamine 6G match closely with literature values. Given that this measurement technique requires no calibration standard, this method could potentially be used as a new standard procedure for determining Φ_f in fluorescent materials.