Laser Direct Writing of Graphene Quantum Dots inside a Transparent Polymer

Graphene quantum dots (GQDs) have emerged as a promising new class of environmentally friendly quantum dots with unique properties. However, the limitations of synthesis and patterning methods have hindered GQDs from displaying their true potentials to date. Here, we demonstrate the simultaneous synthesis and patterning of GQDs for the first time inside a transparent polymer, polydimethylsiloxane (PDMS), using femtosecond laser pulses. By focusing and scanning femtosecond laser pulses, arbitrary fluorescent patterns such as a concealed fluorescent QR code can be readily patterned without pre- and/or post-treatment. In addition, the proposed method is applied to the fabrication of fluorescent three-dimensional structures inside a transparent polymer via multiphoton interactions. The proposed method realizes single-stepped and spatially selective patterning of GQDs directly inside polymer substrates and expands the possibilities of GQDs for applications in novel flexible three-dimensional optoelectrical devices.