Effect of Electrochemical Oxidation on Physicochemical Properties of Fe‐Containing Single‐Walled Carbon Nanotubes

Abstract

Metal catalysts are necessary for fabricating carbon nanotubes, but are often considered impurities in the end products, and arduous steps are used to remove catalyst residues from the nanotube structure. However, as metals can be electrocatalytic, instead of removing them we can utilize their role in detection of analgesics. Herein, we study the physicochemical properties of Fe-containing single-walled carbon nanotubes (SWCNTs), and the effect of simple oxidative pretreatment on them. We show that a gentle anodic pretreatment i) increased the amount of oxidized Fe nanoparticles, most likely exhibiting phases Fe 3 O 4 and Fe 2 O 3 and ii) effectively removed disordered carbonaceous material from SWCNT bundles surfaces. Pretreatment had only a marginal effect on sensitivity towards analgesics. However, interestingly, selectivity of Fe-SWCNTs towards paracetamol and morphine could be modified with pretreatment. Through this kind of in-depth investigation, we can, to a certain extent, correlate various material properties of SWCNTs with the observed electrochemical performance. This approach allows us to evaluate what factors in SWCNTs truly affect the electrochemical detection of biomolecules.

What Determines the Electrochemical Properties of Nitrogenated Amorphous Carbon Thin Films?

“…Likewise, AA has been shown to experience a similar cathodic shift in its oxidation potential in the presence of similar oxygen functionalities . Moreover, our recent investigations show that PA also experiences a cathodic shift in its oxidation potential upon oxidative treatment of single-wall carbon nanotube (SWCNT) network electrodes . Because an opposite trend is seen here in all of the previously discussed cases, some species other than oxygen in the system must cause this inhibition of the reaction on the nitrogenated electrode surfaces.…”

“…39 Moreover, our recent investigations show that PA also experiences a cathodic shift in its oxidation potential upon oxidative treatment of singlewall carbon nanotube (SWCNT) network electrodes. 58 Because an opposite trend is seen here in all of the previously discussed cases, some species other than oxygen in the system must cause this inhibition of the reaction on the nitrogenated electrode surfaces. Furthermore, the response of nitrogenated amorphous carbon films toward DA oxidation was recently investigated by Behan et al 23 Their results indicated that there was a slight increase in the oxidation current of DA (but no change in the oxidation potential) on nitrogen-containing film in comparison with nitrogen-free film: The I p value increased linearly as a function of the scan rate, and the peaks were symmetric, pointing toward the weak adsorption of reaction species on the surface of nitrogenated a-C electrodes.…”