Photophysical Characterization of Non-Covalently Bound Porphyrin-Nanodiamond Assemblies in Water

Photoinduced charge transfer dynamics between nanodiamond, ND, particles and adsorbed dyes can potentially provide the necessary driving force to induce chemical reactions. We present steady-state and time-resolved fluorescence and UV-visible absorption data of self-assembled aggregates of the free-base porphyrin meso-(tetracarboxyphenyl)porphyrin, H₂TCPP, and surface modified ND. Surface modification of H-terminated nanodiamond was carried out by the laser ablation method in water which has been reported to result in a OH-rich surface of ND, OHND. Interactions between H₂TCPP and OHND in water result in a bathochromic shift of the porphyrin Soret band and a quenching of both the porphyrin singlet and triplet state. The results are discussed in the context of what is known regarding the energetics of ND in solution and a model of porphyrin quenching by OHND is proposed.