Multifunctional N-doped graphene quantum dots towards tetracycline detection, temperature sensing and high-performance WLEDs

In this work, nitrogen-doped graphene quantum dots (N-GQDs) with high blue fluorescence are synthesized by the one-pot hydrothermal method from benzimidazoles. The as-fabricated N-GQDs possess a homogeneous size of 3.8 nm, good crystallinity, pip photostability, good water soluble, and a high quantum yield of about 25 %. In addition, it is found that the fluorescence of N-GQDs can be obviously quenched by tetracycline (TC) and elevated temperature. The detection of TC is implemented, with a detection limit of 0.21 μmol L⁻¹. For the temperature sensing, the fluorescence intensity shows a linear reduction between 25 °C and 100 °C. Moreover, reversible and stable abilities of temperature sensing are demonstrated. Owing to the superior optoelectronic properties, white light emitting diodes (WLEDs) using the N-GQDs as the phosphor are fabricated, and the CIE coordinates is (0.357, 0.315) with the color temperature of 4427 K. The results reported here will expand the multiple applications of N-GQDs in environment monitoring, biosensing engineering and optoelectronic devices.