Pecularities of Heavily Boron-Doped Nanodiamond Formation during High-Pressure Pyrolysis of 9-Borabicyclo[3.3.1]nonane Dimer

We report a detailed study of nanodiamond formation during pyrolysis of the heterocyclic compound 9-borabicyclo[3.3.1]nonane dimer (C₁₆H₃₀B₂) at pressures of 8–9 GPa. Experimental data demonstrate nanodiamond nucleation directly upon precursor decomposition in the temperature range 770–830 K. We propose a mechanism of nanodiamond nucleation which involves cross-linking of molecules by B–C bonds, with the sp³ hybridization of the molecules retained. Raman spectroscopy results provide convincing evidence of boron incorporation into the crystal lattice of nanodiamond particles 2.1 and 4.3 nm in average size. Analysis of Raman spectra allows the boron concentration in the nanodiamond to be estimated at a level of 10²¹ cm^–3.