A Comparative Study of Synthesis Routes for Nitrogen-Doped Graphene Quantum Dots in Fluorescence Quenching-Based...

The detection of nitrite in water is crucial for environmental and public health monitoring, yet traditional methods are often complex and laboratory-bound. This work reports a comparative study of synthesis routes for developing a low-cost, fluorescence quenching-based sensor using nitrogen-doped graphene quantum dots (N-GQDs). The facile, one-pot hydrothermal synthesis using citric acid and ethylenediamine yields N-GQDs with superior optical properties and a more uniform size (3.01 ± 0.41 nm) compared to other common precursors. The optimized N-GQDs were successfully applied to nitrite detection in a custom-built, low-cost optoelectronic setup, exhibiting a robust linear response from 0-50 μM and achieving a limit of detection (LOD) of 7.37 μM. This work not only clarifies the role of synthesis routes in N-GQDs' performance but also provides a foundation for on-site water quality monitoring devices.