Abstract:
The effect of ultraviolet radiation on the optical absorption and fluorescence spectra of the colloidal system of carbon nanodots in ethanol has been investigated. The laser dye Nile red was used as a precursor to synthesize the nanodots. The emission spectrum of the nanodots has the shape of a broad weakly structured asymmetric band with a maximum at $\lambda\approx$ 652 nm. Ultraviolet irradiation (250–400 nm) leads to a significant transformation of the optical spectra of the dots, in particular, to the disappearance of the intense absorption band of the nanodots in the visible region, bleaching of the solution and an increase in absorption in the ultraviolet region of the spectrum. The changes in absorption are accompanied by quenching of fluorescence of nanodots and a change in its spectral composition: with increasing irradiation time, the fluorescence color changes from red to green, and short-wavelength radiation with a maximum at $\sim$500 nm begins to dominate in the spectrum. The observed effects are associated with photochemical reactions in carbon nanodots, leading to changes in their composition and structure.
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