Triplet-triplet annihilation based upconversion in silica matrices

Abstract

Triplet-triplet annihilation based upconversion emission (TTA-UC), through energy transfer processes among organic dyes, has been achieving great attentions for the potential applications in different fields; an important step forward the application of TTA-UC systems in real devices is the incorporation of the dye couple into solid supports.In this work mesoporous silica (SBA) with regular pores and silica nanoparticles (SNs) with core-shell structure were prepared and loaded with 2,3,7,8,12,13,17,18–octaethyl–21H,23H–porphine platinum(II) (PtOEP) and 1,3,6,8–Tetraphenylpyrene (TPPy) which act as antenna/sensitizer of the TTA-UC process and as light emitting species, respectively. The samples were fully characterized by TEM imaging, XRDP, steady-state and time resolved fluorescence and phosphorescence measurements. No upconverted emission could be detected for the SBA samples because the mesoporous matrix offered a rigid location to the dyes resulting in aggregate and excimer-like species with modified electronic properties. On the other hand, TTA-UC was recorded on SNs samples; in the latter case, steady-state and time resolved phosphorescence and fluorescence measurements indicated that PtOEP was entrapped in monomeric form and TPPy was mainly present as monomer.The careful and detailed photophysical characterization of the obtained nanostructured materials enables the optimization of the conditions to achieve light upconversion in solid matrices.