Nanodiamond as a New Hyperpolarizing Agent and Its (13)C MRS.

In this work, we have hyperpolarized carbonaceous nanoparticles (D ≈ 10 nm), that is, "nanodiamonds", with 1.1% (13)C (natural abundance) using dynamic nuclear polarization (DNP). The polarization buildup curve showed a signal enhancement with relative intensity up to 4700 at 1.4 K and 100 mW microwave power. (13)C magnetic resonance spectra (MRS) were obtained from the sample at 7 T, and the signal decayed with a T1 of 55 ± 3s. Notably, polarization was possible in the absence of added radical, consistent with previous results showing endogenous unpaired electrons in natural nanodiamonds. These likely contribute to the shorter T1's compared to those of highly pure diamond. Despite the relatively short T1, these observations suggest that natural nanodiamonds may be useful for in vivo applications.