X-ray photoelectron spectroscopy studies of graphite powder and multiwalled carbon nanotubes covalently modified with Fast Black K: evidence for a chemical release mechanism via electrochemical reduction

The development of new materials from which to construct controlled chem.-release systems was an active area of research for the past 4 decades. Using XPS graphite powder and multiwalled C nanotubes (MWCNTs) covalently derivatized with 2,5-dimethoxy-4-[4-(nitrophenyl)azo]benzenediazonium chloride (FBK) or a deriv. of FBK are important new micro and nano-scale materials for use as voltammetrically controlled chem.-release reagents in applications where the small size of the material is advantageous. By examg. the N1s and O1s regions of the XPS spectra the authors can identify functionalities within the FBK moiety as well as hydroxyl, quinonyl and carboxylic acid functional groups present on the C surface. Comparison of the XPS spectra of the FBK derivatized C (FBK carbon) and FBK derivatized MWCNTs (FBK-MWCNTs) before and after electrochem. redn. reveals that cleavage of the azo-linkage within the FBK moiety occurs upon redn. in aq. soln. The voltammetric cleavage of the azo-linkage induces chem. release of 1,4-phenylenediamine from the C surface, demonstrating the proof of concept for these novel materials. It is envisaged that derivs. of these materials could be used in vivo in a wide range of areas including medical diagnosis and targeted drug-delivery systems as well as in in vitro applications such as anal. chem., sensor technol. and industrial process monitoring and control. [on SciFinder(R)]