Enhancement of fluorescence and singlet oxygen production of berberine on clay Nanosheets by surface-fixation Induced emission (S-FIE)

[Display omitted] •The fluorescence quantum yield (Φf) of Berberine was much enhanced when Berberine was adsorbed on the clay surface.•While the Φf of Berberine in water is 0.00049, that with clay is 0.49.•The excited lifetime (τ) of Berberine without and with the clay is 0.084 and 14 ns.•Singlet oxygen generation was observed o with a quantum yield of 0.022 by the light irradiation to Berberine on the clay. In this study, photochemical properties including singlet oxygen production of a natural alkaloid-type dye berberine were investigated in water and on the clay. Berberine adsorbed on the clay showed an increase in the fluorescence quantum yield and fluorescence lifetime. In particular, the fluorescence enhanced about 1000 times, which is the highest in luminescence enhancement achieved by clay. The effect of clay on the energy level such as the charge separation state was thought to be one of the factors responsible for fluorescence enhancement. Furthermore, it was found that the clay improved the singlet oxygen production quantum yield of berberine to 0.022, while berberine did not generate singlet oxygen in water. So far, the effects of complexing dye molecules with clay were mainly focused on the photo-physicochemical processes such as the absorption wavelength, fluorescence quantum yield, and excited lifetime of dye molecules, but this research revealed that complexing with clay can improve the efficiency of the photochemical reaction such as singlet oxygen generation.