Title:	Electrochemical Reaction Assisted 2D π‑Stacking of Benzene on a MWCNT Surface and its Unique Redox and Electrocatalytic Properties
Authors:	Nisha, Sivakumar Lakshminarayanan, V. Kumar, Annamalai Senthil
Issue Date:	Jan-2020
Publisher:	American Chemical Society Publications
Citation:	Langmuir 2020, Vol.36, p19
Abstract:	Turning the π-structure and electronic properties of carbon nanotubes (CNTs) is a cutting-edge research topic in interdisciplinary areas of material chemistry. In general, chemical functionalization of CNT has been adopted for this purpose, which has resulted in a few monolayer thickness increment of CNT diameter size. Herein, we report an interesting observation of >10-fold increment in the apparent diameter of multiwalled carbon nanotubes (MWCNTs) brought about by a process of self-assembly of the BZ moiety on MWCNT, which is formed by electrochemical oxidation of a surface-adsorbed benzene–water cluster, {BZ-nH2O}. From physicochemical characterizations by transmission electron microscopy (TEM) and Raman and IR spectroscopic techniques and electrochemical characterizations by several radical scavenger species, it has been revealed that benzene radical moieties as a series of π-stacked layers ([BZ]-π-stack) were self-assembled on the MWCNT surface. A possible mechanism for their formation was proposed to be electrochemical oxidation of H2O from the MWCNT@{BZ-nH2O}ads layer to oxygen gas via hydroxyl radical formation and benzene cationic radical species at 1.2 V vs Ag/AgCl followed by its self-assembly into a unique MWCNT@[BZ]-π-stack network. The scanning electrochemical microscopic (SECM) technique was used to identify the in situ •OH radical formation. The electrochemical studies of a glassy-carbon-modified MWCNT@[BZ]-π-stack system showed a well-defined and highly symmetrical redox peak at an equilibrium potential E1/2 = 0.2 V vs Ag/AgCl (pH 2 HCl/KCl), with a peak-to-peak potential separation of 0 V, highlighting the ideal-surface-confined electron-transfer nature of the redox couple. Furthermore, enhanced electrical conductivity over the unmodified MWCNT was observed when testing the surface-sensitive redox couple Fe3+/Fe2+ with the modified electrode. This new redox material showed a specific electrocatalytic reduction of hydrogen peroxide at neutral pH (pH 7 phosphate buffer solution) unlike the quinone and other organic redox mediators, which show the reduction signal only in the presence of horseradish peroxidase enzyme.
Description:	Restricted Access.
URI:	http://hdl.handle.net/2289/7427
ISSN:	0743-7463 1520-5827 (Online)
Alternative Location:	https://doi.org/10.1021/acs.langmuir.9b01970
Copyright:	2019 American Chemical Society
Additional information:	Supplementary information available
Appears in Collections:	Research Papers (SCM)

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