A nanocomposite prepared from silver nanoparticles and carbon dots with peroxidase mimicking activity for colorimetric and SERS-based determination of uric acid.

Silver-carbon dots (Ag-CDs) nanocomposites with excellent peroxidase-like and surface-enhanced Raman scattering (SERS) activities were fabricated by reducing silver ion with carbon dots. The formation of the core-shell structure was demonstrated by transmission electron microscopy. The Ag-CD nanocomposite catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to form oxidized TMB (oxTMB) that has a blue color with an absorption maximum at 652 nm. The catalytic activity originates from the fact that the electrons of CDs are transferred to H2O2 and decompose H2O2 into hydroxy radicals. The nanocomposites can be used for uric acid (UA) detection because UA can reduce oxTMB to form colorless TMB. The absorbance drops as the concentration of UA increases from 1 to 500 μM. The SERS signal of oxTMB can be detected (at 1605 cm-1) using the Ag-CD nanocomposites as SERS substrate. The intensity of the SERS signal decreases when the concentration of UA ranges from 0.01 to 500 μM. Graphical abstract Schematic representation of the fabrication of silver-carbon dots (Ag-CDs). The Ag-CDs catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to form blue-colored oxidized TMB (oxTMB). UA reduces oxTMB to form colorless TMB. This process is monitored by surface-enhanced Raman scattering (SERS) spectra for UA detection.