Defined functionality and increased luminescence of nanodiamonds for sensing and diagnostic applications by targeted high temperature reactions and electron beam irradiation

Abstract

Nanodiamonds have excellent mechanical and optical properties, high surface areas and tunable functional surfaces. They are also non-toxic, which makes them well suited for biomedical applications. Here we highlight an integrated and scalable surface functionalization approach by a high temperature gas–solid phase reaction protocol monitored via thermogravimetry for very controlled and precise degraphitization, as well as hydrogen, oxygen and nitrogen (–NH₂) functionalization in a high temperature reactor. In particular, we discuss the rational and precise control of chemical functionalization through introduction of functional groups and of an increased photoluminescence from additional nitrogen-vacancy defects (NV-centers) produced via controlled electron beam irradiation. We have shown that multiple surface analytical methods such as IR-, Raman, photoelectron spectroscopy, light scattering, and electron microscopies allow for quality control of the surface functionalization. The approach together with controlled electron beam irradiation is well suited to produce large amounts of functionalized bright fluorescent nanodiamond probes, which can easily be further chemically modified. Employing this integrated and scalable approach well defined (multi-) functionalized bright fluorescent nanodiamonds are available in large quantities and with high quality enabling a wide range of potential applications as novel sensors and for bioimaging beyond the lab scale.