Magneto-Induced Self-Assembling of Conductive Nanowires for Biosensor Applications

A novel procedure to architecture nanoelectrode arrays with enhanced electrochemical properties was developed. Magneto-assisted formation of conducting nanowires upon self-assembling of Au-shell/CoFe₂O₄-magnetic-core nanoparticles (18 ± 3 nm diameter) was demonstrated on a Au electrode surface by application of an external magnetic field. The nanowires were visualized by atomic force microscopy showing similar diameters (40 nm) and a length increase from 0.57 to 1.53 μm when the time intervals allowed for the self-assembling process ranged from 15 to 120 min. The conducting nanowires caused an increase of the electrode surface area yielding an electrochemical response to a diffusional redox probe (ferrocenemonocarboxylic acid) enhanced by ∼6.5-fold after 120 min. The enhancement factor for the electrochemical process was controlled by the time intervals allowed for the nanoelectrode array formation. The primary electrochemical reaction of the electron relay was coupled with the bioelectrocatalytic oxidation of glucose in the presence of soluble glucose oxidase resulting in the amplification of the biocatalytic cascade controlled by the growth of the nanostructured assembly on the electrode surface. The studied nanoelectrode array was suggested as a general platform for electrochemical biosensors with the enhanced current outputs controlled by the structure of the self-assembled nanowires.