Direct electrochemistry and electrocatalysis based on a film of horseradish peroxidase intercalated into Ni–Al layered double hydroxide nanosheets

Positively charged Ni–Al layered double hydroxide nanosheets (Ni–Al LDHNS) have been used for the first time as matrices for immobilization of horseradish peroxidase (HRP) in order to fabricate enzyme electrodes for the purpose of studying direct electron transfer between the redox centers of proteins and underlying electrodes. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that the HRP–Ni–Al LDHNS film had an ordered structure and that HRP was intercalated into Ni–Al LDHNS with a monolayer arrangement. Field emission scanning electron microscopy (FESEM) showed that the HRP–Ni–Al LDHNS film had a uniform, porous morphology. UV–vis spectroscopy indicated that the intercalated HRP retained its native structure after incorporation in the Ni–Al LDHNS film. The immobilized HRP in Ni–Al LDHNS on the surface of a glassy carbon electrode (GCE) exhibited good direct electrochemical and electrocatalytic responses to the reduction of hydrogen peroxide (H2O2) and trichloroacetic acid (TCA). The resulting H2O2 biosensor showed a wide linear range from 6.00 × 10−7 M to 1.92 × 10−4 M, low detection limit (4.00 × 10−7 M) and good stability. The results show that Ni–Al LDHNS provide a novel and efficient platform for the immobilization of enzymes and realizing direct electrochemistry and that the materials have potential applications in the fabrication of third-generation biosensors.