Direct laser writing of semicylindrical conductive structures encircled by graphene quantum dots

Graphene quantum dots (GQDs) are fluorescent nanoparticles with temperature-dependent fluorescence and have been studied for applications in anti-counterfeiting tags. We have reported that polydimethylsiloxane (PDMS) can be modified into a graphitic carbon and GQDs by femtosecond laser irradiation. Additionally, the formation of silicon carbide was observed. In this study, a semicylindrical conductive structure circled by GQDs was fabricated through a single-laser scanning of PDMS. Fluorescence microscopic images of the cross-sectional structure revealed the formation of a fluorescence structure around the conductive structure. The emission peak was observed at 400 nm (excitation at 360 nm) using a spectrometer, consistent with typical GQD fluorescence. Applying DC voltage to the structure induced Joule heating, leading to temperature-dependent changes in GQDs fluorescence intensity. The fluorescence intensity decreased as the temperature increased and recovered with cooling. Therefore, the fluorescence intensity can be modulated by applying voltage, which has potential applications in voltage-controlled optoelectronic devices.