Iridium-doped carbon dots as a nanozyme for a smartphone-based dual colorimetric and fluorometric detection of H2O2 in food samples

In this study, iridium-doped carbon dots (Ir-CDs) were synthesized by using a one-step hydrothermal method and characterized. We studied the oxidase- and peroxidase-like properties of Ir-CDs and introduced them as a novel nanozyme. The kinetic behavior of Ir-CDs as a peroxidase mimic nanozyme was investigated using the Michaelis-Menten model. Moreover, we employed Ir-CDs as both fluorophore and catalytic agent to design a dual colorimetric and fluorimetric sensor based on the Ir-CDs-TMB-H 2 O 2 reaction to measure hydrogen peroxide. The linear ranges for colorimetric and fluorimetric methods were 0.5-7.5 and 5-50 nM, respectively, and the detection limits were 0.13 and 1.0 nM. The methods demonstrated good repeatability, with relative standard deviations (RSDs) of 1.0% (2.5 nM) for colorimetry and 1.4% (10 nM) for fluorimetry. Additionally, a smartphone-based dual-sensor system was established for hydrogen peroxide using the introduced colorimetric and fluorimetric methods. The developed method showed acceptable reproducibility with RSDs of 5.0% (3.75 nM) and 2.0% (20 nM) for colorimetric and fluorimetric detection, respectively. The proposed instrumental and smartphone-based sensors were successfully applied to determine hydrogen peroxide in honey and soda samples. The obtained recoveries were in the range of 93–107%. • -Ir-CDs were synthesized by a simple hydrothermal method. • -The peroxidase mimic properties of Ir-CDs were studied and confirmed. • -A dual colorimetric and fluorometric sensor for H 2 O 2 detection was designed based on Ir-CDs-TMB-H 2 O 2 reaction. • -Ir-CDs act as both fluorophore and colorimetric reaction catalytic agent in the sensor. • -The dual sensor was employed to determine H 2 O 2 in honey and soda samples.