Fluorescence resonance energy transfer between CdTe quantum dots and copper phthalocyanine

The fluorescence resonance energy transfer in CdTe quantum dots (QDs)-copper phthalocyanine (CuPc) is investigated by ultrafast time-resolved spectroscopy technique equipped with femtosecond laser (780 nm, 76 MHz, 130 fs). The results show that the fluorescence lifetime of CdTe QDs decreases with the increase of CuPc concentration, and the energy transfer efficiency is found to increase with the increase of CuPc concentration. Moreover, the influence of the laser excitation power on the energy transfer efficiency is also studied. It is found that transfer efficiency decreases as excitation laser power increases, the physical mechanism is the thermal activation in the high power and the excited state transitions of high order induced by two-photon. The energy transfer efficiency can reach 43.8%, when the laser power is 200 mW, via two-photon excitation. This study indicates that the CdTe QDs-CuPc composite system has high potential as the third generation of photosensitizers.