Pd(II)-Directed Encapsulation of Hydrogenase within the Layer-by-Layer Multilayers of Carbon Nanotube Polyelectrolyte Used as a Heterogeneous Catalyst for Oxidation of Hydrogen

Abstract

A metal-directed assembling approach has been developed to encapsulate hydrogenase (H2ase) within a layer-by-layer (LBL) multilayer of carbon nanotube polyelectrolyte (MWNT-PVPMe), which showed efficient biocatalytic oxidation of H2 gas. The MWNT-PVPMe was prepared via a diazonium process and addition reactions with poly(4-vinylpyridine) (PVP) and methyl iodide (MeI). The covalently attached polymers and organic substituents in the polyelectrolyte comprised 60-70% of the total weight. The polyelectrolyte was then used as a substrate for H2ase binding to produce MWNT-PVPMe@H2ase bionanocomposites. X-ray photoelectron spectra revealed that the bionanocomposites included the elements of Br, S, C, N, O, I, Fe, and Ni, which confirmed that they were composed of MWNT-PVPMe and H2ase. Field emission transmission electron microscope images revealed that the H2ase was adsorbed on the surface of MWNT-PVPMe with the domains ranging from 20 to 40 nm. Further, with the use of the bionanocomposites as nanolinkers and Na2PdCl4 as connectors, the (Pd/MWNT-PVPMe@H2ase)n multilayers were constructed on the quartz and gold substrate surfaces by the Pd(II)-directed LBL assembling technique. Finally, the as-prepared LBL multilayers were used as heterogeneous catalysts for hydrogen oxidation with methyl viologen (MV(2+)) as an electron carrier. The dynamic processes for the reversible color change between blue-colored MV(+) and colorless MV(2+) (catalyzed by the LBL multilayers) were video recorded, which confirmed that the H2ase encapsulated within the present LBL multilayers was of much stronger stability and higher biocatalytic activity of H2 oxidation resulting in potential applications for the development of H2 biosensors and fuel cells.

Synthesis and photophysical properties of pyrene-functionalized nano-SiO2 hybrids in solutions and doped-PMMA thin films

“…Secondly, two sharp peaks recorded at approximately 2940 and 2890 cm −1 were assigned to the aliphatic -CH 2 stretching vibration bands and confirmed that the 3-aminopropyl substituent had anchored onto the silica core surface [23]. This feature has been previously observed in studies where a detailed characterization of different organic-modified carbon nanotubes has been performed [33,34]. In the present study, given the much thinner organic layer relative to the SiO 2 nanoparticle size compared to that of carbon nanotubes, the FETEM image of the organic layer was not as clear as that observed on carbon nanotubes;…”