Time-resolved fluorescence and absorption microspectroscopy of a single microparticle

Time-resolved fluorescence and transient absorption spectroscopy systems have been developed for elucidating photophysical and photochemical processes occurring in μm-sized volumes. The fluorescence measurement is based on a confocal fluorescence microscope and single photon timing, which enables the fluorescence dynamics to be observed with both sub-μm three-dimensional space- and ps time resolutions. For transient absorption spectroscopy, excitation and monitoring laser pulses are coaxially and confocally introduced into a microscope. This optical arrangement provides the longitudinal resolution in addition to the lateral resolution. By combining a laser trapping technique we have succeeded in measuring primary photoprocesses of a single manipulated particle in solution. Fluorescence analysis of individual microcapsules in solution gave information on solute concentration distribution between capsules. The viscosity of a single oil droplet dispersed in aqueous solution was estimated by analyzing the T-T annihilation of Zn-tetraphenylporphyrin.