Absolute fluorescence quantum yield determined by photothermal deflection spectroscopy.

We present a spectroscopic method for measuring the fluorescence quantum efficiency [Formula: see text] of fluorophores that does not require calibration standards. Photothermal Deflection Spectroscopy (PDS) is combined with conventional absorbance spectroscopy, and [Formula: see text] is extracted from fits over the spectral range of interest. This technique obviates the need for multiple measurements-either on calibration standards or as a function of concentration-and yields results of [Formula: see text] in a single measurement consistent with previously reported values. Five different organic dyes are tested whose absorbance/fluorescence profiles span the visible spectrum and whose known quantum efficiencies range from 0 to near 1. The accuracy of the results over significant ranges of wavelength and quantum yield demonstrate the robustness and efficacy of this method.