Cu3Mo2O9 nanosheet incorporated with hemoglobin on carbon ionic liquid electrode for the direct electrochemistry and electrocatalysis

In this paper Cu3Mo2O9 nanosheet was prepared by a hydrothermal method and further used to investigate the direct electrochemistry of hemoglobin (Hb) with a carbon ionic liquid electrode (CILE) as the substrate electrode. Hb was mixed with Cu3Mo2O9 nanosheet and cast on the CILE surface with chitosan (CTS) as the film-forming material. UV-vis and FT-IR spectroscopic results showed that Hb remained in its native structure in the composite film. Direct electron transfer of Hb on the modified electrode was realized with a pair of well-defined quasi-reversible redox waves that appeared on cyclic voltammograms. The redox peak potential appeared at -0.252 V (E (pc)) and -0.141 V (E (pa)), respectively, with the formal peak potential calculated as -0.196 V, which was the characteristic of electroactive center of Hb heme Fe(III)/Fe(II). The result could be attributed to the presence of Cu3Mo2O9 nanosheet on the electrode surface that was of benefit for the protein orientation and promoted direct electron transfer between the redox active center of Hb and the substrate electrode. The CTS/Cu3Mo2O9-Hb/CILE showed good electrocatalytic ability in reducing different substrates such as trichloroacetic acid, H2O2 and O-2, with wider linear range and lower detection limit, thus exhibiting the potential application of the Cu3Mo2O9 nanosheet in third-generation electrochemical biosensors.