Efficient Photoinduced Energy Transfer in Porphyrin-Based Nanomaterials

Synthesis, characterization, and ultrafast dynamics of porphyrin- and zinc porphyrin-based nanomaterials are reported. Spherical nanoparticles composed of a group of uniform materials based on organic salts (nanoGUMBOS) are prepared from either porphyrin or zinc porphyrin with trihexyl(tetradecyl)phosphonium in aqueous colloidal suspension with sizes of approximately 50 nm in diameter. Ultrafast excited-state dynamics of porphyrin and zinc porphyrin nanoGUMBOS in water are measured using transient absorption spectroscopy with 400 nm excitation. Results are compared to corresponding measurements of the porphyrin molecular dye parent compounds in water. Porphyrin and zinc porphyrin have long-lived excited states arising from intersystem crossing of the first-excited singlet S-1 state to the triplet T-1 state. These excited-state lifetimes are significantly faster in porphyrin-based nanoGUMBOS as compared to the corresponding porphyrin molecules due to intermolecular energy transfer, electronic delocalization, and altered chemical environments of the nanomaterials. Additionally, these results demonstrate that porphyrin-based nanoGUMBOS are promising nanomaterials for light harvesting in solar cells and optoelectronics.