Langmuir−Blodgett Films of Pyridyldithio-Modified Multiwalled Carbon Nanotubes as a Support to Immobilize Hydrogenase

Pyridylthio-modified multiwalled carbon nanotubes (pythio-MWNTs) have been prepared by a reaction of the oxidized MWNTs with S-(2-aminoethylthio)-2-thiopyridine hydrochloride. The obtained pythio-MWNTs nanocomposites formed stable floating monolayers at the air−water interface, which were transferred onto substrate surfaces by the Langmuir−Blodgett (LB) method. Compositions and morphologies of the LB films were characterized by absorption, Raman, X-ray photoelectron spectra as well as by scan electron microscopy and atomic force microscopy. These pythio-MWNTs LB films were then used as a support to immobilize hydrogenase (H2ase) to form bionanocomposite of pythio-MWNTs-H2ase. Cyclic voltammograms for indium tin oxide electrode covered with the pythio-MWNTs-H2ase films were investigated in both Ar and H2 saturated 0.05 M KCl electrolyte solutions at pH from 4.0 to 9.0. A reversible redox couple of [4Fe−4S]2+/1+ clusters of H2ase was recorded when the pH value was 6.0 and 9.0, with reduction and oxidation potentials appearing at about −0.70 and −0.35 V vs Ag/AgCl, respectively. It was revealed that the H2ase was of high catalytic activity and strong stability in the LB films of pythio-MWNTs-H2ase. Hence, we suggested that the present bionanocomposites could be used as heterogeneous biocatalyst to catalyze reversible reaction between protons and H2, resulting in potential applications in biohydrogen evolution and H2 biofuel cells.