A new strategy for simple and quick estimation of redox active nickel impurity in pristine SWCNT as nickel hexacyanoferrate by electrochemical technique

Abstract

Residual metal impurities in the pristine carbon nanotubes (CNT) have been found to show an exceptional electrochemical and electro-catalytic properties. To quantify the impurities, sophisticated instrumental techniques and time consuming electrochemical methods have been adopted. Herein, we report, a new strategy for simple and quick detection of nickel impurity in pristine single walled carbon nanotube (SWCNT*Ni, *Ni=nickel impurity) as redox active nickel hexacyanoferrate hybrid (SWCNT*Ni-HCF) by potential cycling of the pristine SWCNT modified glassy carbon electrode (GCE/SWCNT*Ni) with ferricyanide in pH 2 KCl-HCl solution at a scan rate 50mVs−1 (t=12±1min). Quantitative stripping of the nickel as nickel ion that combines with ferricyanide to form Ni-HCF hybrid on the SWCNT surface (i.e., GCE/SWCNT*Ni-HCF) is found to be the mechanism for the observation. In-situ derivatization of NiO modified GCE with ferricyanide was studied as an important control experiment. A calibration plot was constructed by plotting surface excess value of GCE/Ni-HCF obtained by cyclic voltammetric experiment against NiO loading on unmodified GCE surface. Unknown concentration of nickel in the pristine SWCNT was then determined by substituting surface excess value of SWCNT*Ni-HCF in the calibration plot. Obtained value is comparable with the result of continuum source electro-thermal atomic absorption spectrometry method.