Direct Electrochemistry of Hemoglobin Based on Silver Sulfide Nanospheres Anchored Multiwalled Carbon Nanotubes

Abstract

A novel silver sulfide nanospheres anchored multiwalled carbon nanotubes (Ag2S-MWNTs) nanocomposite was prepared by hydrothermal method, after which the direct electrochemistry of hemoglobin (Hb) immobilized on the Ag2S-MWNTs/chitosan (Ag2S-MWNTs/CHIT) composite matrix modified glassy carbon electrode (GCE) was demonstrated. The morphologies and composition of the Ag2S-MWNTs were characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy. Cyclic voltammetric and amperometric studies demonstrated that the Hb incorporated in the Ag2S-MWNTs/CHIT film exhibited a pair of well–defined, quasi–reversible cyclic voltammetric peaks at about –0.30 V vs. SCE in pH 7.0 buffer and possessed excellent electrocatalytic ability toward H2O2 reduction. The linear dynamic range for the detection of H2O2 was 0.8 – 240.0 μM with a correlation coefficient of 0.999 and the detection limit was estimated at about 0.4 μM (S/N = 3). The electron transfer rate constant was estimated to be 3.1·s−1, suggesting a fast direct electron transfer was realized. The present study indicated that the nanocomposites show the potential applicability as the new type of mediator for direct electrochemistry of the redox proteins.