A novel catalase mimicking nanocomposite of Mn(II)-poly-L-histidine-carboxylated multi walled carbon nanotubes and the application to hydrogen peroxide sensing

Abstract

In this work, a novel enzyme-mimicking nanocomposite of Mn(II)-poly-L-histidine (PLH) functionalized carboxylated multi walled carbon nanotubes (CMWCNTs) was designed and synthesized. Based on the catalase-like activity of the nanocomposite, a non-enzymatic hydrogen peroxide (H₂O₂) biosensor was then established and explored for H₂O₂ electrochemical detection. The nanocomposite was characterized by Fourier transform infrared spectra, Raman spectroscopy, and transmission electron microscopy. Due to the enlarged effective surface area and the efficient electrocatalytic activity of the Mn(II)-PLH redox-active units, the obtained Mn(II)-PLH-CMWCNT electrode showed excellent electrocatalytic performance toward H₂O₂ disproportionation. Under the selected optimum conditions, the prepared biosensor exhibited highly sensitive response toward H₂O₂, and the response current had a good linear relationship between the response currents and H₂O₂ concentrations in the range of 0.002-1.0 mM, a low detection limit of 0.5 μM and a sensitivity of 464.18 μA mM^-1 cm^-2. With the good stability, reproducibility and selectivity, the proposed biosensor was successfully applied to the determination of H₂O₂ in real-life samples, and showed satisfactory results. In summary, the Mn(II)-PLH-CMWCNT nanocomposite could be a promising enzyme-mimicking nanomaterial for the researches of electrocatalysis, biosensing and relevant fields.

Keywords: Biosensor; Hydrogen peroxide; Mn(II); Multi walled carbon nanotubes; Poly-L-histidine.