Hydrogenation of HPHT nanodiamonds and their nanoscale interaction with chitosan

Abstract

Hydrogenation of the surface can provide specific and unique properties to nanodiamonds. In this study, a series of high-pressure high-temperature nanodiamonds (HPHT NDs) with varying levels of hydrogenation and sp2 carbon content is prepared and characterized in terms of optical properties, structure, surface chemistry, particle size distribution, and zeta potential. The higher the surface sp2-C content and level of hydrogenation the better dispersibility in acidic to neutral pH and higher isoelectric points are achieved. We further evaluated the interaction of hydrogenated HPHT NDs with chitosan by infrared spectroscopy and atomic force microscopy. We have found that chitosan is electrostatically attracted to the hydrogenated HPHT NDs, it improves the dispersibility of the HPHT NDs with a lower level of hydrogenation, and it provides colloidal stability in the broad pH range 2–11 to all hydrogenated HPHT NDs. Finally, we demonstrate that chitosan coating enables the decoration of hydrogenated HPHT NDs by silver nanoparticles.