RESUMO
In this study, nanostructured porous gold electrodes were prepared by the anodization of gold in the presence of oxalic acid or glucose as a reductant, and applied as scaffolds for direct electron transfer (DET)-type bioelectrocatalysis. Gold cations generated in the anodization seem to be reduced by the reductant to construct a porous gold structure. The DET-type performance of the electrode was examined using two DET-type model enzymes, bilirubin oxidase (BOD) and peroxidase (POD), for the four-electron reduction of dioxygen and the two-electron reduction of peroxide, respectively. BOD and POD on the anodized porous gold electrodes exhibited well-defined sigmoidal steady-state waves corresponding to DET-type bioelectrocatalysis. Scanning electron microscopy images revealed sponge-like pores on the electrodes. The anodized porous gold electrodes demonstrate promise as scaffolds for DET-type bioelectrocatalysis.
Assuntos
Biocatálise , Enzimas Imobilizadas/química , Ouro/química , Nanoestruturas/química , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/química , Peroxidase/química , Eletroquímica , Eletrodos , Transporte de Elétrons , Glucose/química , Peróxido de Hidrogênio/química , Ácido Oxálico/química , Oxigênio/química , Porosidade , Propriedades de SuperfícieRESUMO
A method to stably immobilize microbes on electrodes was developed. Resting cells of Methylobacterium extorquens AM1(MeAM1) were caged within multiwalled carbon nanotubes (MWNTs)by adding the cells to a water dispersion of MWNTs then allowing the resulting mixture to dry on electrodes. The MeAM1-MWCNTs electrode thus obtained displayed excellent activities in the bidirectional bioelectrocatalysis due to formate dehydrogenase(s) in the resting cells; formate oxidation and carbon dioxide reduction proceeded at steady-state catalytic current densities of 0.6⯱â¯0.1 and -0.8⯱â¯0.1â¯mA cm-2, respectively, using methyl viologen as mediator under very mild conditions (pH 7.0, atmospheric pressure, and 37⯰C). In addition, the catalytic signal was stable for more than one week under continuous operation.
Assuntos
Fontes de Energia Bioelétrica/microbiologia , Técnicas Biossensoriais/métodos , Eletrodos , Methylobacterium extorquens/metabolismo , Nanotubos de Carbono/química , Biodegradação Ambiental , Catálise , Formiato Desidrogenases/metabolismo , OxirreduçãoRESUMO
A photo-driven bioanode was constructed using the thylakoid membrane from spinach, carbon nanotubes, and an artificial mediator. By considering a linear free-energy relationship in the electron transfer from the thylakoid membrane to the mediators, and the oxygen resistance of the reduced mediators, 1,2-naphthoquinone was selected as the most suitable mediator for the photo-driven bioanode. Water-dispersed multi-walled carbon nanotubes served as scaffolds to hold the thylakoid membrane on a porous electrode. The constructed photo-driven bioanode exhibited a photocurrent density of over 100µAcm-2 at a photon flux density of 1500µmolm-2s-1.