A Simple Universal Strategy for Quantification of Carboxyl Groups on Carbon Nanomaterials: Carbon Dioxide Vapor Generation Coupled to Microplasma for Optical Emission Spectrometry

The physicochemical properties and applications of carbon nanomaterials are remarkably dependent on the amount of carboxyl group on their surfaces. Unfortunately, it is challenging to determine the carboxyl group on carbon nanomaterials at an ultra-low density not only due to the low sensitivities of conventional techniques but also because there are no matrix-matched Certified Reference Materials available. In this work, a novel strategy comprising coupling carbon dioxide vapor generation to a microplasma optical emission spectrometer was developed for the sensitive and accurate quantification of surface carboxyl groups on carbon nanomaterials. The carboxyl group on multiwall carbon nanotubes (MWCNTs), graphene (G) or its oxide (GO) was converted to carboxylic acid using concentrated hydrochloric acid prior to quantification. The generated carboxylic acid was purified and then reacted with sodium bicarbonate to generate CO2 which was swept into a miniature point discharge optical emission spectrometer (µ...