Control of coherence length and aggregate size in the J-aggregate of porphyrin

The spectroscopic aggregation number (coherence length) and physical size of the J-aggregates of anionic meso-tetrakis(4-sulphonatophenyl)porphyrin (H4TPPS2−) are controlled by ammonium ion concentration. The contributions of absorption and scattering are determined using the extinction and resonance light scattering (RLS) spectra of the TPPS J-aggregate. The highest spectroscopic aggregation number (12.9) was determined for the J-aggregate of hydrodynamic radius of 56 ± 10 nm.