Dual emission carbon dots as enzyme mimics and fluorescent probes for the determination of o-phenylenediamine and hydrogen peroxide.

A selective and sensitive fluorescent technique is proposed to determine o-phenylenediamine (OPD) and hydrogen peroxide (H2O2). This is carried out by utilizing enzyme mimics carbon dots (N/Cl-CDs) and fluorescent probe carbon dots (N/Zn-CDs). The synthesized N/Cl-CDs and N/Zn-CDs were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Ultraviolet-visible spectrophotometry techniques. The particle size of synthesized carbon dots was found to be 4.1 ± 1.09 nm and 3.3 ± 1.82 nm for N/Cl-CDs and N/Zn-CDs, respectively. The N/Cl-CDs showed a noticeable intrinsic peroxidase-like activity, which could catalyze the oxidization of OPD by H2O2 to form the yellow colored product 2,3-diaminophenazine (DAP). The N/Zn-CD fluorescence was quenched directly by DAP through the inner filter effect (IFE). As a result, a novel double carbon dot system as enzyme mimics and fluorescent investigations to recognize OPD and H2O2 was obtained. The N/Cl-CDs were synthesized by deep eutectic solvent (DES) source and chamber electric furnace. N/Zn-CDs were also synthesized with the quantum yield of 27.52% through the tubular furnace technique using ethylenediamine tetra acetic acid disodium zinc salt and ascorbic acid as precursors. The detection limits were found to be 0.58 μM and 0.27 μM for OPD and H2O2, respectively. The nanoprobe was applied to real sample analysis, which showed excellent recovery in the range of 95.8-103.5% and 98.6-107.3% for OPD and H2O2, respectively. The dual emission carbon dots as enzyme mimic and fluorescent probe sensing system opens a new platform for determination of H2O2 and OPD in real samples. Graphical abstract Schematic illustration of the preparation of double carbon dots and determination process of o-phenylenediamine (OPD) and hydrogen peroxide (H2O2).