Multi-wall Carbon Nanotubes Decorated with Bismuth Oxide Nanocrystals Using Infrared Irradiation and Diazonium Chemistry

Abstract

A simple and efficient method using infrared (IR) irradiation is presented to decorate multi-wall carbon nanotubes (MWCNTs) with bismuth oxide nanocrystals (Bi2O3 NCs) using ammonium bismuth citrate (ABC) as Bi precursor. The present methodology comprises 4 steps: purification, functionalization, impregnation and calcination. Various techniques (XPS, TEM, PXRD, EDX, Raman and TGA) are used to characterize the resulting materials. The treatment with sodium hydroxide leads to the purification of MWCNTs (p-MWCNTs) which is confirmed by the absence of alumina. The chemical functionalization of p-MWCNTs with monocarboxylic aryl diazonium salts generated in-situ (p-MWCNTs-D1) followed by impregnation in the presence of IR radiation is the crucial step in homogeneously impregnating functionalized MWCNTs with ABC (p-MWCNTs-D1/ABC). Calcining p-MWCNTs-D1/ABC at optimum temperature results in a controlled decoration of Bi2O3 NCs in their pure phase. A bimodal distribution of Bi2O3 NCs on MWCNTs with a Gaussian mean diameter of ~ 1.1 and ~ 11.21 nm is evidenced. The originality of this work is the decoration of CNTs for the first time with Bi2O3 nanocrystals. Metastable β-Bi2O3 (tetragonal) crystal phase is noticed on the surface of CNTs. Electrical conductivity of the samples was assessed on bucky papers elaborated from the various modified MWCNTs. The present methodology is applicable to large-scale preparation which opens interesting perspectives for nanotechnology applications.