Carbon nanohorns – based nanocomposites as sensing layers for room temperature resistive oxygen sensing: preliminary results

This paper presents the oxygen sensing response of a resistive sensor employing sensing layers based on a binary matrix nanocomposite such as carbon nanohorns/polyvinylpyrrolidone and oxidized carbon nanohorns/polyvinylpyrrolidone, both at 9/1 w/w/ mass ratio. The sensing structure comprises a silicon substrate, a SiO2 layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The thin film's morphology and composition are examined through scanning electron microscopy (SEM) and RAMAN spectroscopy. The oxygen sensing capability of each carbon nanohorns composite-based sensing layer was analyzed by applying a current between the two electrodes and measuring the voltage difference when varying the O2 from 0% to 100% in dry nitrogen. Experiments reveal that in the case of pristine carbon nanohorns / PVP matrix nanocomposite, the resistance increases. In contrast, in the case of oxidized carbon nanohorns, the resistance of the sensitive layer decreases with increasing oxygen concentration. The results are explained by considering the differences from structural and electrical points of view between the two types of nanocarbonic materials. Moreover, previous resistive RH sensing measurements in humid air and humid nitrogen using oxidized carbon nanohorns as sensing elements proved helpful in better understanding and discriminating between the chemisorption/physisorption of oxygen molecules at carboxyl functional sites and graphitic carbon sites.