Photopatterning of Carbon Dots in Poly(vinyl alcohol) with Photoacid Generators.

Carbon dots (CDs) have drawn considerable attention owing to their attractive photoluminescence, advantageous chemical tolerance, good biocompatibility, and so on. However, it remains challenging to tune their photoluminescence spatially and temporally due to their high photostability. Herein, a viable approach to in-situ dialing the photoluminescence of CDs by using light in the presence of a photoacid generator (PAG, e.g., diphenyliodonium hexafluorophosphate) is demonstrated. Fluorescence quenching occurs upon light irradiation due to the protonation of pyridine and amino nitrogen atoms of CDs according to X-ray photoelectron spectroscopy and cyclic voltammetry. As such, blue, green, and red color fluorescent patterns of CDs are ready to form in poly(vinyl alcohol) by light irradiation under photomask. These patterns not only show a controlled preservation time under room light, but also can be erased on demand by flood UV irradiation, which are promising for advanced anti-counterfeiting such as shelf-life based security and erasable encryption.