Polyaniline-Derived Nitrogen-Doped Graphene Quantum Dots for the Ultratrace Level Electrochemical Detection of Trinitrophenol and the Effective Differentiation of Nitroaromatics: Structure Matters

Highly crystalline and aromatic nitrogen-doped graphene quantum dots (N-GQDs) which demonstrate unparalleled electrochemical sensing properties toward nitroaromatics were made from a single source, polyaniline (PANI), by a simple hydrothermal synthetic strategy. The higher sensitivity and the effective differentiation between different nitro compounds exhibited by the N-GQD is evidence of its potential as a sensor for nitro compounds, especially the nitroaromatics. The N-GQD modified glassy carbon electrode (N-GQD/GCE) exhibited record sensitivity for 2,4,6-trinitrophenol (TNP) with a limit of detection (LOD) as low as 0.2 ppb (∼200 ng/l or 1 nM), which is the lowest of the reported values, the previous lowest is in micromolar (μM) levels and extended the remarkable sensing property in real water samples as well. The superior and selective sensing behavior of N-GQD toward TNP and other nitroaromatics is assigned to the richly N-doped aromatic structure of the N-GQD from the precursor PANI, which can possibly promote closer and selective molecular interactions with nitroaromatic compounds through ring stacking, π–π, or hydrogen bonding or a combination of these, and the enhanced conductivity and improved electron transfer ability due to the in situ N-doping.