Fluorometric detection of pH and quercetin based on nitrogen and phosphorus co-doped highly luminescent graphene-analogous flakes
Highly luminescent nitrogen and phosphorus co-doped graphene-analogous flakes (NPCGFs) were synthesized by one-pot simple hydrothermal reaction using β-cyclodextrin (β-CD), vinylphosphnic acid (VPA) and o-phenylenediamine (oPD) as the precursors. Importantly, VPA, as an important organic P-containing monomer, was selected as phosphorus source to generate more conjugated and effective binding sites on the surface of NPCGFs. This synthetic strategy not only allows to enhance structural rigidity, but also effectively eliminates surface traps of the NPCGFs, resulting in improved fluorescent quantum yield (FL QY) of the NPCGFs. And oPD act as nitrogen source and amino-functionalisation of NPCGFs surface in the synthesis process, simultaneously. The high FL of NPCGFs (QY, 32.49%) have an irregular shape with a typical diameter of ~62 nm and display strong fluorescence, with excitation/emission maxima of 360/445 nm. What’s more, it is found that the NPCGFs can serve as multifunctional FL probes for pH and quercetin (Qc) detection. Linear relationship exist between the drop in FL intensity and the concentrations of Qc in the range from 0.35 to 30 mg mL-1 and linear of pH variation between 4.0 and 7.0. The probe was further applied to the determination of Qc in living cells.