C3N4 nanosheet-supported Prussian Blue nanoparticles as a peroxidase mimic: colorimetric enzymatic determination of lactate.

Prussian Blue nanoparticles were deposited on g-C3N4 nanosheets. The resulting nanocomposite possesses peroxidase-like (POx) activity and can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine at room temperature in the presence of H2O2. This leads to formation of a blue product with an absorption maximum at 650 nm. The formation of the Prussian Blue nanoparticles on the g-C3N4 nanosheets, and the POx-like activity of the composite were characterized in detail. The POx mimic was used for determination of L-lactic acid via detection of H2O2 that is produced by the enzyme lactate oxidase (LOx). The assay has a linear range that extends from 5 to 100 μM, and the detection limit is 2.2 μM. The method was successfully applied to the determination of L-lactic acid in spiked human serum. Graphical abstract Ultra-small Prussian Blue (PB) nanoparticles were used to modify g-C3N4 nanosheets, and their peroxidase-like activity was explored for detection of L-lactic acid. LOx represent L-lactate oxidase, and TMB represents 3,3',5,5'-tetramethylbenzidine.