Carbon Dot Films with Efficient Interdot Förster Resonance Energy Transfer for Optical Coding by Ultraviolet Photooxidation

The influence of ultraviolet (UV) laser irradiation on the optical properties of carbon dots (CDs) prepared by the hydrothermal synthesis from citric acid and ethylenediamine has been investigated. Investigation was performed in close-packed carbon films obtained by drop-casting. Observed photoluminescence redshift in films was ascribed to Förster Resonance Energy Transfer (FRET). UV laser irradiation increased carbon dot film light transmission and photoluminescence intensity and leads to a blueshift of photoluminescence. We attribute these changes to CD surface distraction via oxidation that leads to changing of FRET conditions. Controllable changing of carbon dot transmission and photoluminescence parameters by confocal laser irradiation might be used for optical microcoding and the creation of fluorescent labels.