Bondar M. One- and two-photon induced electronic processes in solutions of donor-acceptor fluorene molecules

Linear photophysical, nonlinear optical, photosensitizational and photochemical properties of new donor-acceptor fluorene derivatives were comprehensively investigated under one- and two-photon electronic excitation. The effect of donor-acceptor substituents in the fluorene core and solvent parameters on linear electronic absorption and fluorescence anisotropy properties have been shown. Two-photon absorption (2PA) spectra of new fluorene derivatives were obtained in a broad spectral range, based on modified open aperture "Z-scan" and two-photon induced fluorescence methods. A detailed analysis of the 2PA spectra of fluorenes was performed and their molecular structure-property relationships were established. Two-photon stimulated emission transitions in organic molecules were investigated for the first time, and corresponding values of two-photon emission cross sections were determined. The processes of singlet oxygen generation and photochemical decomposition of new fluorene derivatives were investigated under one- and two-photon excitation. The values of corresponding quantum yields of singlet oxygen generation and photochemical decomposition were obtained and analyzed. High potential abilities of new donor-acceptor fluorene molecules for practical application in the field of two-photon optical power limiting, 3D optical data storage, two-photon fluorescence microscopy and photodynamic therapy were shown.