2D Co3O4 modified by IrO2 nanozyme for convenient detection of aqueous Fe2+ and intercellular H2O2

A portable sensor for visual monitoring of Fe2+ and H2O2, two-dimensional Co3O4 modified by nano-IrO2 (IrO2@2D Co3O4) was prepared in this work, for the first time, with the help of microwave radiation at 140 ?, which was further stabilized onto common test strips. The present IrO2@2D Co3O4 possessed superior dual-function enzyme-like activity with low toxicity and excellent biocompatibility. Especially, trace Fe2+ and H2O2 could exclusively alter their enzyme-like catalytic activity with discriminating hyperchromic or hypochromic effect, i.e., from blue to colorless or to dark blue for both IrO2@2D Co3O4 dispersion and its functionalized test strips. The linear regression equations were A(652) = 0.5940 - 0.00041 c(Fe)(2+) (10(-8) M, R-2 = 0.9927) for Fe2+ and increment delta A(652) = 0.0023 c(H2O2) + 0.00025 (10(-7) M, R-2 = 0.9982) for H2O2, respectively. When applied to visual monitoring of aqueous Fe2+ and intercellular H2O2, the recoveries were 101.2 similar to 102.5% and 95.8 similar to 103.7% with detection limits of 1.25 x 10(-8) mol/L and 1.02 x 10(-7) mol/L, respectively, far below the permitted values in drinking water set by the World Health Organization. The mechanisms for the enhancing enzyme-mimetic activity of IrO2@2D Co3O4 and its selective responses to Fe2+ and H2O2 were investigated in detail.