Cu(III)-independent oxidation and sensing of glucose on multi-layer stacked copper nanoparticles

A highly sensitive electrode for sensing glucose has been fabricated by electropolymerization of 2-amino-5-mercapto-1,3,4-thiadiazole on a solid carbon paste substrate, and subsequent electrodeposition of multi-layer stacked copper particles as an outer surface. The individual copper particles are characterized by a large number of edges and corners of crystallites. Their preferred orientation {111} is parallel to the electrode surface. The conductive polymer interlayer results in an increase of the particle nucleation density and a further decrease of the polarization overpotential for direct (enzyme-free) oxidation of glucose in 0.1 M NaOH solution. A well-shaped voltammetric peak can be observed at around 0.3-0.5 V (vs. SCE, depending on scan rate) that is due to glucose oxidation. This potential is much lower than the one required for Cu(III) formation. A bulk electrolysis experiment using a thin-layer electrochemical cell confirmed the assumption that that glucose undergoes 2-electron oxidation. The mechanism of glucose oxidation in the absence of Cu(III) is discussed. The electrode exhibits a very high sensitivity (slope) of 3.31 mA cm(-2) mM(-1), and the detection limit is 2 mu M (at an SNR of 3). Features of the new sensor include the ease of fabrication, its high stability and good selectivity.