Study of stability of heavily boron doped nanodiamond dispersions

Comparative study of water dispersions of boron-doped and detonation nanodiamonds uniformly purified from non-diamond phases in acids reveals high resistance of boron-doped particles to agglomeration and precipitation and its absence in case of detonation nanodiamonds. Boron doped nanodiamonds were obtained by pyrolysis of 9-borabicyclo[3.3.1]nonane dimer C$_{16}$H$_{30}$B$_2$ at pressure 8–9 GPa and temperature 1250–1300$^\circ$С. The concentration of boron in the synthesized nanodiamonds was estimated using Raman spectroscopy to be at a level of 10$^{21}$ cm$^{-3}$ which corresponds to a heavily doped state. FTIR absorption analysis exposes additional lines in doped diamond spectra characteristic to B–O groups. The presence of boron on the nanoparticle surface is thought to be responsible for the high stability of the suspension after the acid purification process without the need for additional functionalization. Improved stability of boron-doped nanodiamond in aqueous solutions with a pH of 2.5–8 can be a crucial factor for its effective application in electrochemical and biomedical technologies, for seeding of crystallization centers to obtain conducting CVD diamond films without disturbing electrical contact with substrate, and for inkjet printing of patterned boron-doped diamond electrodes.