Smartphone colorimetric determination of hydrogen peroxide in real samples based on B, N, and S co-doped carbon dots probe

In this paper, we report the use of a smartphone and B, N, and S co-doped carbon dots (BNS-CDs) as a promising peroxidase mimic to quantify hydrogen peroxide (H 2 O 2 ). The synthesized BNS-CDs exhibited excellent peroxidase-like activity to catalyze the reaction of the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) with H 2 O 2 to generate a blue oxide product (ox-TMB) with maximum absorption at 652 nm. Steady-state kinetic analysis demonstrated that the BNS-CDs showed much higher affinity than natural horseradish peroxidase (HRP) for H 2 O 2 due to their small size and larger specific surface area. A smartphone colorimetric readout device was employed to record the RGB (red green blue) value of the ox-TMB solution via the Android application Color Grab for quantitative detection. A good linear relationship ( R 2 = 0.9970) between the H 2 O 2 concentration and |R-R blank | value was obtained in the range of 3–30 μM with a limit of detection (LOD) of 0.8 μM. The current method was successfully applied to determine H 2 O 2 in mouthwash and milk with recoveries of 92.70–108.30%. The developed assay is a promising portable detection platform for H 2 O 2 with good sensitivity and selectivity, simple operation, fast response, and low cost. Graphical abstract