Peroxidase Mimic Sulfur‐Rich CuO‐Carbon Nitride Core‐Shell Nanorods for the Colorimetric Detection of Aminophenol Isomers

A solid-state method was used to derive a sulfur rich CuO-carbon nitride core-shell nano-composite from a Cu-organic hybrid. The synthesized material was characterized by XRD, morphology by SEM and TEM. Elemental analysis was investigated using EDS. The novel sulfur rich CuO-carbon nitride core-shell composite demonstrated as peroxidase activity for the oxidation of aminophenol isomers in the presence of H₂O₂. The oxidized products of o-aminophenol (o-AP) and p-aminophenol (p-AP) in phosphate buffer (PB, pH 7) showed strong absorption peaks at 435 and 475 nm, respectively in the UV-Visible spectra. Whereas no oxidation reaction was observed for m-aminophenol. Kinetic analysis of sulfur rich CuO-graphitic carbon nitride revealed that the catalyst functioned by a ping-pong mechanism for the oxidation of both o-AP & p-AP by hydrogen peroxide (H₂O₂). Based on K_M values, substrate affinities were in the order o-AP>H₂O₂>p-AP. We further used this material for selective colorimetric detection of o-AP and p-AP in PB pH 7. The linear ranges obtained for o-AP and p-AP were 1–200 μM (LOD=1.5 μM, r²=0.99) and 10–500 μM (LOD=2.27 μM, r²=0.99), respectively. The developed analytical platform was used to detect these isomers in river water and p-AP in artificial urine.