| A temporal study of single-walled carbon nanotube (SWNT) carboxylation by nitric acid reflux was conducted to optimize the presence of carboxyl groups, which provide the necessary and sufficient chemical anchors (e.g. carboxyl groups) to couple biomolecules for possible nanoscale applications, while maintaining SWNT physical, chemical, and optoelectronic properties. The SWNT samples were characterized by UV-Vis-NIR, FTIR, Raman, and X-ray photoelectron spectroscopies (XPS) as well as atomic force microscopy (AFM). Raw HiPco SWNTs were dispersed via sonication in an aqueous solution of Triton X-100 and then oxidized by nitric acid reflux. Aliquots of SWNTs were removed following reflux times ranging from 30 min to 48 h. Following 12 h of acid reflux, quantitative XPS studies revealed 11% absolute carboxylation, and UV-Vis-NIR spectra showed that these SWNTs maintained their optical properties as shown by the retention of van Hove singularities characteristic of SWNTs. |
