Up-converted luminescence of cyanine dye J-aggregates

A J-band photoluminescence of cyanine dye J-aggregates was observed under excitation below the band gap. This emission is not due to two-photon absorption. The luminescence intensity becomes weaker with a decrease in temperature. For the excitation below the band gap, the rise and decay times of the J-band luminescence from cyanine dye concentration of 4×10−4 M are 9.0 and 155 ps, respectively. In case of the band-to-band excitation, the radiative decay starts just after excitation and fast and slow decay components have time constants of 13 and 54 ps, respectively. The lifetime of luminescence depends on the concentration of the cyanine dye.