Solid-based titrimetry as a straightforward method for simultaneous detection of hydroxyl and carboxylic functional groups during evaluation of the acidity of nanocarbons

Abstract

A novel method has been proposed based on solid-based titrimetry for detection of –COOH and –OH functional groups in nanocarbons during direct evaluation of the acidity and functionality of carbon nanostructures. In this technique, a known amount of carbon nanostructure is homogeneously mixed with NaCl powder as solid media with optimized ratio (1:8, w/w). Then the mixture is put on a vibrating spatula for addition to a NaOH standard solution (0.05M) to get two distinct end points (EPs) in the titration curve for carbon nanostructures such as multi-walled carbon nanotubes (MWCNTs). The first EP is correlated to the simultaneous neutralization of –COOH and –OH with known equivalent of a standard basic solution during evaluation of the total amounts of both –COOH and –OH presented in nanocarbons. Whereas, the other EP is related to the reaction between added MWCNT–COOH and MWCNT–O−, generated during the first EP. Relative standard deviation of the solid-based titrimetry for four replicate analyses is evaluated to 3.02%. The reliability of the observed trends is finally evaluated by estimation of the acidity of an initial standard material, followed by comparison with back-titration method.