DONOR-ACCEPTOR COMPLEXES OF EXCITED-STATES ON SILICA SURFACE AND IN HEXANE SOLUTION AT LIQUID-NITROGEN TEMPERATURE

It is shown that an exciplex between pyrene (Py) and N,N-dimethylanili ne (DMA) forms at low temperature (77 K) on the nonporous silica surfa ce and in a solid hexane solution. The fluorescence lifetime of pyrene in the adsorption state increases when the quencher concentration gro ws at 77 K. The exciplex fluorescence spectra in the adsorption state shifts to a blue wavelength range when the temperature decreases as a result of the dipole-dipole interaction of the exciplex with the hydro xy groups of the silica surface. On the basis of the model suggested t he hydroxyl group concentration on the dehydrated at 770 K silica surf ace has been estimated.