An insight into the functionalisation of carbon nanotubes by diazonium chemistry: Towards a controlled decoration

The derivatisation of materials including iron, gold, and carbon by addition of diazonium salts is a reliable process to tune their interfacial interaction with the surrounding media. In this regard, the functionalisation of carbon nanostructures by diazonium chemistry is a versatile strategy to obtain soluble nanomaterials with degrees of functionalisation among the highest ever reported. Starting from these premises we have studied the functionalisation of multi-walled carbon nanotubes by addition of the aryl diazonium salts generated in situ by treatment of 4-methoxyaniline with isopentylnitrite. Following a thorough purification and characterisation protocol (UV–vis, TGA, ATR-IR, cyclic voltammetry, AFM and other surface analytical techniques), we have investigated the key parameters to obtain both functionalised multi-walled carbon nanotubes, where the amount of functional groups anchored to the carbon surface is less than a monolayer, and superfunctionalised carbon nanotubes, with a carbon nanotube core and a multilayered aryl coating. The results outlined provide the basis for the design and controlled processing of novel decorated carbon nanostructures that would be useful for a number of technological applications.