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

High Resolution Image Download MS PowerPoint Slide 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.