Proton spin diffusion in a nanodiamond

We report on a proton magnetic resonance study of a powder nanodiamond sample. We show that 1H spin–lattice relaxation in this compound is mainly driven by the interaction of nuclear spins with unpaired electron spins of paramagnetic defects. We measured the spin–lattice relaxation time T1 by means of a saturation comb pulse sequence followed by dipolar dephasing, and plotted T1 as a function of the dephasing time τd in different external magnetic fields. The received T1(τd) dependence provides a striking manifestation of the spin diffusion-assisted relaxation regime. The obtained experimental data allow us to estimate the spin diffusion coefficient and spin diffusion barrier radius. (papers)