Enhancement of Singlet Oxygen Generation of Radachlorin® Conjugated with Polyvinylpyrrolidone and Nanodiamonds in Aqueous Media

Catalytic complexes of photosensitizer Radachlorin® (sodium salts of chlorin e6, chlorin p6, purpurin 5) with polyvinylpyrrolidone (PVP) and detonation nanodiamonds (DND) have been synthesized and studied by optical absorption spectroscopy, luminescence excitation, dynamic light scattering and viscometry methods. Binary complexes PVP-Radachlorin® demonstrated electrostatic and donor–acceptor binding of Radachlorin® with PVP detected by spectrophotometric titration when Q-band (~650 nm) displayed bathochromic shift and enhancement with isosbestic point indicating a single type of binding sites. Similar changes in luminescence emission spectra in binary complexes were observed earlier at higher polymer contents. The yield of singlet oxygen under UV-irradiation (405 nm) of Radachlorin® increased in PVP-Radachlorin® complex. Dynamic light scattering and viscometry confirmed the stability of complexes and no agglomeration. Ternary complexes DND-PVP-Radachlorin® provided a generation of singlet oxygen by UV-irradiation exciting diamonds which do not emit but transfer the energy to surrounding molecules. The results allow develop effective catalysts for chemical and medical applications as well as for disinfection, active filtration and cleaning air, water, surfaces. Novel catalytic complexes based on chemically inert diamonds are resistant to the singlet oxygen and profitable for long-term usage.