Application of photoacoustic, photothermal and fluorescence spectroscopies in signal enhancement and the kinetics, chemistry and photophysics of several dyes

Photothermal and photoacoustic phenomena are consequences of nonradiative, heat releasing processes that occur upon relaxation of an excited molecule. When a molecule absorbs energy, as through excitation with a laser light source, heat releasing processes such as internal conversion and intersystem crossing will result in the formation of a pressure wave due to a change in the local density due to solvent heating and the production of a thermal gradient due to local heating of the solvent. By monitoring the magnitude and/or time profile of such heat releasing processes by a substance or substances after absorption of exciting radiation, quantum yields, lifetimes and a wide variety of kinetic and photophysical or photochemical parameters of a solute molecule or system of molecules may be determined.; A number of modifications to conventional photoacoustic and photothermal spectroscopies are applied in analytical studies of liquid and solid systems. The quenching of benzophenone by potassium iodide is used to demonstrate the application of time resolved photothermal spectroscopies in the study of fast (submicrosecond) deexcitation processes. Inherently weak X-ray photoacoustic signals at a synchrotron are enhanced by the introduction of a volatile liquid into a gas-microphone photoacoustic cell.; Traditionally, photoacoustic signals have been detected either by gas coupling with a microphone or with a piezoelectric detector. However, optically detected photoacoustic signals have been used in the determination of physical properties of a liquid sample system and are successfully applied to the study of deexcitation processes of a number of dye molecules. Photothermal beam deflection photoacoustic (PBDPA), fluorescence and absorbance measurements are utilized to study the chemistry and photophysics of cresyl violet in aqueous, aqueous micellar and methanolic solutions. A previously unrecognized concentration dependence of the fluorescence quantum yield of cresyl violet is thoroughly investigated.; Aspects of the chemistry and photophysics relating to the potential use of several diazo dyes as photothermal sensitizing dyes in photodynamic therapy are explored experimentally and discussed. Photothermal beam deflection, fluorescence and absorbance measurements are again utilized. The dyes are found to have a number of interesting chemical and photophysical properties. They are also determined to be ideal photothermal sensitizing dye candidates.