Porous graphitic carbon nitride (g-C3N4) was prepared by a one-step acid etching and ultrasonication process. It is found that the strong blue fluorescence of g-C3N4 (with excitation/emission maxima at 320/400 nm) is fairly selectively quenched by uric acid (UA). The morphology and chemical structure of the nanoporous g-C3N4 were characterized by XRD, TEM and FTIR. Quenching studies and Stern-Volmer plots reveal two UA concentration ranges of different quenching efficiency. The first extends from 50 to 500 nM, the other from 0.5 to 10 μM. The limit of detection is 8.4 nM. The two quenching processes are attributed to both dynamic and static quenching. The porous g-C3N4 probes were applied to the determination of UA in (spiked) human serum and human plasma, and the results were as good as those obtained with UA standard solutions. These data illustrate that g-C3N4 can be used to selectively and sensitively quantify trace levels of UA even in a complex environment. Graphical abstract Porous graphite nitride carbon (g-C3N4) is shown to be a viable fluorescent probe for uric acid (UA) via both dynamic and static quenching. The electron transfer of carbon nitride is represented by the arrows; hν is the incident light; PL is the fluorescence emission.
Keywords: Acid etching; Blue fluorescence; Dynamic quenching; Limit of detection; Plasma; Serum; Static quenching; Stern-Volmer plots.