Self-assembled porphyrin aggregates have been employed as a model system for biomimetic photosynthetic antenna in our study. Here we will present our recent results on temperature dependent ultrafast spectroscopy of energy transfer in self-aggregating porphyrin nanorods. This study will provide insights into designing principles for efficient long�range energy transport in biomimetic photosynthetic antenna systems.Temperature dependent fluorescence lifetime measurement showed that aggregates exhibit a dynamic Stokes shift of the fluorescence spectrum at low temperature. The fluorescence spectrum was red-shifting with the time delay (see figure 1). Indicating there is energy transfer between different segments of one aggregate. Because the length and environment of these segments in one aggregate are variable, the energy level of different segments could be different. So there should be energy relaxation from higher lying states to lower lying states. The reason of why this cannot be observed at room temperature could be ascribed to �reversed� energy transfer at higher temperature. Temperature dependent polarized pump-probe measurement was also carried out for porphyrin aggregates. The anisotropy decay at low temperature provided evidence for energy transfer pathways from Q state of one segment to the Q state of another segment in the same aggregate. Figure 1 Transient fluorescence spectra of porphyrin aggregate measured at 3 K.

Probing energy transport in biomimetic photosynthetic antenna with ultrafast spectroscopy

246th National Meeting (2013)

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