Luminescence-based assessment of thermodynamic constants for electrostatic binding of non-luminescent dyes and atomic ions to colloidal semiconductor surfaces

Steady-state and time-resolved luminescence experiments were employed to study the electrostatic interaction of cationic photosensitizers and negatively charged colloidal semiconductor particles. Electrostatic adsorption of efficient photosensitizers on semiconductor surfaces is known to quench the photosensitizers' luminescence. By monitoring the quenching, either directly or competitively, thermodynamic constants for binding of both luminescent and non-luminescent ruthenium and osmium complexes to negatively charged SnO₂ particle have been determined. The function of atomic cations, such as Li⁺, Na⁺ and K⁺, in controlling the binding of cationic dyes to colloidal SnO₂ has also been studied via competitive luminescence. From the study, semiconductor surface binding constants for these species have also been determined.