Development of highly stable conductive multiwalled carbon nanotube ink using covalent and non-covalent functionalization for electrochemical sensors

Ana Elisa Ferreira Oliveira,Arnaldo César Pereira,Lucas Franco Ferreira

doi:10.5599/jese.1134

Abstract

The purpose of this work was the fabrication of a conductive carbon nanotube (CNT) ink. The proposed CNT ink remained remarkably stable over several months. The method includes combining the covalent and non-covalent functionalization, resulting in ink that exhibits excellent storage stability. The covalent functionalization was performed in the acid medium using H2SO4 and HNO3, while the non-covalent functionalization used sodium dodecyl sulfate (SDS) and ultrasonication. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). FTIR and SEM confirmed that at the non-covalent functionalization, SDS was successfully adsorbed on the f-CNT surface, while at the covalent functionalization, the functional groups (-COOH, C=O and -OH) were inserted into the CNT surface. Voltammetry and EIS indicated that SDS in the presence of functional groups facilitates electron transfer by improved electrical conductivity. The final product was a well-dispersed CNT ink with an average ohmic resistance of 18.62 kΩ. This indicates that CNT ink can be used in the fabrication of electrochemical sensors.

Highlights

The carbon nanotube (CNT) was first discovered by Iijima in 1991 [1]
The covalent bonding between functional groups and the CNT skeleton is stronger than the non-covalent interactions
The functionalized carbon nanotube (f-CNT)/sodium dodecyl sulfate (SDS) spectrum shows the bands of SDS related to sulfate groups (1249 and 1121 cm-1), implying that SDS was successfully adsorbed on the f-CNT surface

Summary

Introduction

The carbon nanotube (CNT) was first discovered by Iijima in 1991 [1]. He was studying the synthesis of fullerenes using the arc discharge technique when a “new type of finite carbon structure consisting of needle-like tubes” was discovered. The carbon nanotube ink was fabricated using functionalization. The approach used in this work was a covalent and non-covalent functionalization to improve the carbon nanotube's dispersion stability in water. Non-covalent functionalization of f-CNT was performed in order to improve the dispersion ability in the water.

Objectives

Results

Conclusion