Green Synthesis of Reduced-Graphene OxideQuantum Dots and Application for Colorimetric Biosensor

Abstract We report a one-pot synthesis method to produce reduced-graphene oxide quantum dots (rGOQDs) in perfluorotributylamine (PFTBA) solution by avoiding the use of toxic materials and preventing the generation of undesirable functional groups (epoxy, carbonyl, and carboxyl). The PFTBA solution, consisting of three butyl fluoride groups connected to an amine center, effectively cracked down rGO precursors at ∼ 160 °C, and produced high purity of rGOQDs. Under UV irradiation, the location of the emission peak of the photoluminescence (PL) shifted from 489.3 nm to 460.8 nm as the solution temperature increased from 160 °C to 190 °C due to the enhancement of the bandgap. The produced sample exhibited a long-term photostability without the decay in intensity over 30 days, which can be used for an optical device. Depending on the oxidation state, PL spectra from the rGOQDs-solution mixed with glucose oxidase (GOx) changed the color from blue to green with high sensitivity (3.869 deg/mM) in the glucose concentration of 0-2 millimole, demonstrating that rGOQDs can be applied for colorimetric biosensors using a portable smartphone.