Near-field Fluorescence Spectroscopy and Photochemistry of Organic Mesoscopic Materials

Hiroshi MASUHARA and Hiroyuki YOSHIKAWA

Department of Applied Physics, Osaka University
Suita, Osaka 565-0871, Japan

We have set up a picosecond near-field fluorescence microspectroscopic system whose high performance of 100 nm spatial, a few ps temporal, and 1 nm spectral resolutions makes it possible to correlate topography, fluorescence image, fluorescence spectrum, and fluorescence rise and decay curve with each other. We have applied this system to organic mesoscopic materials containing representative organic chromophors, and spatial inhomogeneity and morphological change are considered in view of photophysics and photochemistry. Near-field fluorescence spectroscopy reveals thickness-dependent fluorescence spectra of tetracene microcrystals, relations between photophysics and morphology of charge transfer microcrystals, and inhomogeneous inner structure of single microcrystals in anthracene-tetracene films. Some anthracene solids show interesting photothermal and photochemical nanometer morphological changes. Future perspectives on near-field excitation with shorter wavelength and/or higher intensity and various kinds of pump-probe measurement are discussed in view of photochemistry studies.