Purification of nitrogen-doped graphene quantum dots via the liquid–liquid extraction system of tetrahydrofuran–(NH4)2SO4–water and its application to sensitive iron(iii) ions determination

Abstract

A facile, rapid method based on a liquid–liquid extraction system for the purification of graphene quantum dots is reported in this study. Nitrogen-doped graphene quantum dots (N-GQDs) were synthesized by a simple hydrothermal route for cutting graphene oxide sheets. Then, through the liquid–liquid extraction system of tetrahydrofuran–(NH₄)₂SO₄–water, N-GQDs have been successfully purified. The as-prepared N-GQDs have an average size of 6 nm and exhibit optimum excitation and emission wavelengths of 330 and 435 nm, respectively. N-GQDs were demonstrated as a sensitive fluorescent sensing probe for Fe³⁺. The sensor can detect Fe³⁺ (R² = 0.992) in the concentration range of 0.2–30 μM, with a detection limit of 0.06 μM. This method of quantitative analysis of Fe³⁺ has good linearity and reliable reproducibility.