Selective immobilization of hydroquinone on carbon nanotube modified electrode via phenol electro-oxidation method and its hydrazine electro-catalysis and Escherichia coli antibacterial activity

Abstract: Electrochemical oxidations of phenol and its derivatives (o-cresol and p-cresol) were examined on a carbon nanotube modified glassy carbon electrode (GCE/CNT) in pH 7 phosphate buffer solution. One of the phenol oxidation byproducts, hydroquinone (HQ) has been immobilized selectively on the GCE/CNT (GCE/HQ@CNT) during the electrochemical oxidation process. The GCE/HQ@CNT showed a stable and well-defined surface confined redox peak at 295mV vs. Ag/AgCl in pH 7. Amongst the various CNTs viz., impure-multiwalled carbon nanotube (MWCNT), functionalized-MWCNT, purified (p)-MWCNT and single walled CNT examined, the p-MWCNT modified GCE showed best results for the HQ immobilization. Physico–chemical characterizations of the HQ@p-MWCNT by TEM, XPS and FTIR and an in situ electrochemical quartz crystal microbalance studies reveal the presence of unreacted phenol on outer surface and clusters of HQ and {HQ-biphenol} species inside the walls of the HQ@p-MWCNT hybrid material. The GCE/HQ@p-MWCNT showed highly selective electrocatalytic oxidation of hydrazine through the mediation of the immobilized HQ/quinone redox species, without any interference from cysteine, ascorbic acid, uric acid, dopamine, nitrite, nitrate and hydrogen peroxide. Control experiments with GCE/MWCNT and GCE have failed to show any such electrocatalysis to hydrazine. Most interestingly, twice higher antibacterial activity towards the Escherichia coli bacteria over the native phenol was noticed on the HQ@CNT. These results indicate potential applicability of the HQ@CNT as hydrazine sensor and thin-film based antibacterial agent. [Copyright &y& Elsevier]