Graphene Oxide Nanosheets as 2D Cationic Photoinitiators with Enhanced Photoluminescence for Chemical Patterning

UV irradiation on native graphene oxide (GO) surfaces in a cation-forming liquid yields surface cationic species that graft the reaction product directly on the GO surface. These surface cations also enhance the intrinsic photoluminescence of GO. The formation of pyrylium as the surface cation is proposed to be responsible for both effects. Using a micrometer-scale photomask, GO itself is used as a 2D platform to form chemical patterns by photoluminescence, cationic polymerization, and reactions with nucleophiles under UV or visible light exposure. Postpatterning by adsorption and fabricating a functionally graded surface are also described for further applications. Our finding offers a versatile light-exposure-based technique to mass-produce the GO microchips with a high integration density.