Facile chemical strategies for the preparation of multiwalled carbon nanotube based composite electrodes for sensing applications

Abstract

The thesis focuses on the development of different composites, based on MWCNT which finds application in various electrochemical sensing platforms. MWCNTs possess some excellent properties and this gets enhanced when metals or metal oxides are coalesced on to the CNT matrix. MWCNT composites of distinctive nature were fabricated by employing different noble metals like silver, palladium and ruthenium. Besides these metals certain metal oxides of tungsten, cobalt and iron are also incorporated. As different materials are successfully integrated, the newly formed MWCNT hybrids could possess some unique properties of all the materials that is being incorporated. More over surface functionalisation of MWCNTs provide more binding sites for the anchoring of metals and metal oxides. Further more such mild functionalisation technique can protect CNTs from structural damage also. The thesis elaborate on the fabrication of four distinct nanocomposites based on MWCNT and their usefulness in various applications. These include Ag/fMWCNT, Cu-WO3- MWCNT, Pd@MWCNT-Co3O4 and RuO2/Fe3O4/MWCNT composite electrode. Ag/fMWCNT flexible films were fabricated through facile method in which silver is being deposited on to MWCNT films by electroless deposition process. The substrate employed in this work is PET, which is flexible and the fabricated electrode can be employed for sensing dopamine. Electrochemical methods like cyclic voltammetry, differential pulse voltametry and chronoamperometry were used to study the sensing behavior of the electrode towards dopamine. The LOD values were found to be 0.7 μM. The electrode also exhibited good pseudocapacitive behavior. Another flexible film electrode Cu-WO3-MWCNT utilized the techniques viz. electroless and electrodeposition process for its formation. Tungsten oxide was incorporated on to MWCNT matrix which was then deposited on to electroless copper substrate. The preliminary and qualitative sensing of ageing of lubricant oils was studied using this electrode. This was revealed by electrochemical impedance studies. One another work reports on the development of Pd@MWCNT-Co3O4 film. The relevance of the electrode lies in the fact that cobalt oxide employed for the fabrication was recovered from spent lithium-ion battries. The cobalt was extracted from the used lithium ion batteries and then converted into oxide form and finally palladium incorporated MWCNT is being deposited on to Co3O4 film byelectrophoretic deposition process. The developed Pd@MWCNT-Co3O4 electrode was used as glucose sensor. The sensing behavior of the electrode towards glucose was revealed from the chronoamperometric studies and the limit of detection was found to be 0.6 μM. Another composite electrode based on MWCNT is from RuO2 and Fe3O4 mixed oxide. The composite was drop casted on to glassy carbon electrode and the sensing behavior of the composite towards simultaneous detection of ascorbic acid and dopamine was studied using cyclic voltammetry and differential pulse voltammetry. The limit of detection was found to be 1.12 μM for ascorbic acid and 0.11 μM for dopamine. In brief, all the nanocomposite electrodes of MWCNTs fabricated were developed through different facile strategies that were found to have good sensing capability towards different analyte molecules. The procedures adopted for the fabrication process were simple and economical. The composites films were characterized by different analytical and instrumental methods. The sensing characteristics were studied using different electrochemical techniques. All the electrodes were found to be stable and reproducible.