Time-Resolved and Near-Field Scanning Optical Microscopy Study on Porphyrin J-Aggregate
A. Miura, K. Matsumura, X. Su and N. Tamai
Department of Chemistry, School of Science, Kwansei Gakuin University, 1-1-155 Uegahara, Nishinomiya 662-8501, Japan
Received: July 23, 1998
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Water-soluble porphyrin, 5,10,15,20-tetraphenyl- 21H,23H-porphine-tetrasulfonic acid (TPPS), forms J-aggregate in aqueous solution depending on experimental conditions such as pH, dye concentration, and/or ionic strength. The steady-state fluorescence and picosecond single-photon timing spectroscopy were applied for protonated monomer and J-aggregate in aqueous solution and in thin films to reveal the dynamics in the S2 and S1 states. The S2 fluorescence spectra from the protonated monomer and J-aggregate were observed in addition to the normal S1 fluorescence. The lifetime of the S2 state was estimated to be ≈5 ps for J-aggregate, whereas the lifetime is shorter than 1 ps for protonated TPPS monomer. The mesoscopic structures of J-aggregate in thin film with and without polymer on the glass surface were examined by scanning near-field optical microscopy. With the surface topography and scanning near-field optical microscopy transmission images, TPPS J-aggregate was found to form a long and narrow tube-like structure which has a few μm length, 0.2-0.5 μm width, and 5-30 nm height. An unidirectional orientation of the structure was also found, which may be originated from the spin-coating process.
DOI: 10.12693/APhysPolA.94.835
PACS numbers: 78.47.+p