Electrochemical nanostructured biosensors: Carbon nanotubes versus conductive and semi-conductive nanoparticles

The aim of this work was to demonstrate that various types of nanostructures provide different gains in terms of sensitivity or detection limit albeit providing the same gain in terms of increased area. Commercial screen printed electrodes (SPEs) were functionalized with 100 μg of bismuth oxide nanoparticles (Bi2O3 NPs), 13.5 μg of gold nanoparticles (Au NPs), and 4.8 μg of multi-wall carbon nanotubes (MWCNTs) to sense hydrogen peroxide (H2O2). The amount of nanomaterials to deposit was calculated using specific surface area (SSA) in order to equalize the additional electroactive surface area. Cyclic voltammetry (CV) experiments revealed oxidation peaks of Bi2O3 NPs, Au NPs, and MWCNTs based electrodes at (790 ± 1) mV, (386 ± 1) mV, and (589 ± 1) mV, respectively, and sensitivities evaluated by chronoamperometry (CA) were (74 ± 12) μA mM-1 cm-2, (129 ± 15) μA mM-1 cm-2, and (54 ± 2) μA mM-1 cm-2, respectively. Electrodes functionalized with Au NPs showed better sensing performance and lower redox potential (oxidative peak position) compared with the other two types of nanostructured SPEs. Interestingly, the average size of the tested Au NPs was 4 nm, under the limit of 10 nm where the quantum effects are dominant. The limit of detection (LOD) was (11.1 ± 2.8) μM, (8.0 ± 2.4) μM, and (3.4 ± 0.1) μM for Bi2O3 NPs, Au NPs, and for MWCNTs based electrodes, respectively.