Substrate effect on the properties of functionalized multiwalled carbon nanotubes grown by e-beam evaporation for high performance H2O2 detection.

Abstract

In the present study, the properties of functionalized multiwalled carbon nanotube thin films deposited on Ta and Al2O3 substrates were compared for better electrochemical sensing performance towards H2O2. We pioneer the fabrication of high quality carbon nanotubes by electron beam evaporation at a high vacuum of 10-6 mTorr. The fabricated films were further characterised using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). Crystallographic properties revealed that the carbon nanotube (CNT) film grown on the Al2O3 substrate exhibits a preferentially oriented (002) peak with high intensity compared to that on Ta. CNTs fabricated on a Ta substrate show better morphology with tightly packed grains and decreased nanotube diameter than the film on sapphire. TEM images confirmed the well adherent and dense nature of the nanotubes on Ta. Electrochemical H2O2 sensors were constructed to demonstrate the sensing performance of CNT/Ta and CNT/sapphire electrodes. CV curves of the samples show high sensitivity for the MWCNT film grown on Ta due to the highly conductive acid resisting nature of the substrate, overcoming the obstacles to electrochemical H2O2 sensing. Compared with the CNT/sapphire electrode, the CNT/Ta electrode exhibited high electrocatalytic activity towards the oxidation of H2O2, as distinct nanotubes are electrochemically linked with the conductive Ta substrate. The CNTs on Ta revealed a very low detection limit of 0.07 μm due to the nanoporous morphology of the film which supported better penetration of electrolytes into the electrode material. The synergetic electrocatalytic effect of the CNT/Ta electrode with excellent redox chemistry is promising for the development of highly sensitive biosensors.