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

Abstract

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 μM (at an SNR of 3). Features of the new sensor include the ease of fabrication, its high stability and good selectivity.

Insight into the Electro-Oxidation Mechanism of Glucose and Other Carbohydrates by CuO-Based Electrodes

“…Although some researchers have already mentioned these suspicions, , the mechanism of glucose oxidation mediated by the Cu III species is considered in almost all works, − and it is considered an established consensus.…”

“…A similar finding has been observed when analyzing glucose sensor results. In this case, the glucose oxidation peak occurs in more negative potentials than that attributed to the formation of Cu III species …”

“…In this case, the glucose oxidation peak occurs in more negative potentials than that attributed to the formation of Cu III species. 33 Other information that also corroborates these controversies is that there are few discrete molecules in which the existence of Cu III is accepted, and in these cases, the ligands play a fundamental role in their stabilization. 34,35 Electron affinity and ionization energy data show that the energy required to remove 1 electron from O (g) 2− (+844 kJ mol −1 ) is smaller than the energy required to remove 1 electron from Cu (g) 2+ (+3554.6 kJ mol −1 ).…”

Electrochemical biomass upgrading: degradation of glucose to lactic acid on a copper(ii) electrode

“…Peaks D and E. Traditionally, peak D is widely ascribed to a Cu 2+ to Cu 3+ oxidation; [50][51][52][53][54] in other words, the formation of a Cu 2 O 3 or CuOOH from CuO or Cu(OH) 2 . Peak E is the redox pairing to peak D, so peak E has been attributed to the reduction of Cu 3+ species to Cu 2+ .…”

Interfacial Effect of Oxygen-Doped Nanodiamond on CuO and Micropyramidal Silicon Heterostructures for Efficient Nonenzymatic Glucose Sensor

“…The CV curve of CuO/NOND/Pyr-Si in the alkaline blank solution exhibited a pair of anodic and cathodic peaks from 0.3 to 0.6 V, as well as an anodic shoulder in the +0.4 to +0.6 V range. The peak potentials from 0.3 to 0.6 V are a typical Cu 0 /Cu­(II) redox couple according to the following reactions: …”