Tuning the formation of aggregates in silica–Rhodamine 6G hybrids by thermal treatment

The formation of fluorescent J aggregates in organic–inorganic Rhodamine 6G–silica hybrids is investigated in sol–gel prepared bulk samples in the concentration range of the transition from fluorescent to non-fluorescent aggregates (1.0 × 10−4–1.0 × 10−3 mol/l). The spectral properties of the observed aggregates are studied by recording the excitation and emission fluorescence spectra and the fluorescence decay kinetics and analyzed in the exciton theory framework. The reported optical features depend both on the synthesis technique and the post synthesis treatments. It is shown that the geometry of fluorescent J aggregates can be modified from oblique to coplanar inclined configuration by thermal treatment of the samples.

► Fluorescent J dimers in Rhodamine 6G–silica type I hybrids.
► J to H dimers concentration threshold is about 1.0 × 10−3 mol/l.
► Large decrease of dye mobility in chloride samples.
► Oblique to coplanar J dimers tuning by 65 ̊C thermal treatment.