pH-Dependent reversible transformation of TPPS4 anchored on mesoporous TiO2 film between monomers and J-aggregates

Protonated TPPS4 monomer and its J-aggregate were formed simultaneously from TPPS4 adsorbed through its sulfonic acid groups on TiO2 porous film by decreasing the pH of the surrounding water and this behavior on TiO2 film can be reversibly repeated depending on pH, indicating a flexible and stable arrangement of TPPS4 through chemical bonds between the sulfonic acid groups and the TiO2 surface.