Manganese-grafted detonation nanodiamond, a novel potential MRI contrast agent

Spatially Resolved Spin–Lattice Relaxation Times and Line Widths in Manganese-Grafted Detonation Nanodiamonds

“…The value of τ e calculated from the EPR data is between 3 × 10 −823 and 10 −7 s. 37 The former was estimated from the RT EPR measurements of the microwave power saturation curves of the Mn 2+ signals in our Mn-DND sample. 23 The latter was obtained from the RT Mn 2+ EPR measurements of the nonresonant dispersion, microwave susceptibility, and the z component of magnetization as a function of the microwave amplitude of the Mn 2+ signals in a paramagnetic salt MnSO 4 • 4H 2 0. 37 We note that the abovementioned EPR-derived electron spin−lattice relaxation times T 1e were measured at a low magnetic field of 0.35 T, while our NMR experiments were carried out at a magnetic field of 8 T. Terblanche and Reynhardt 38 measured T 1e values of the diamond P1 centers in different magnetic fields and discovered an increase in T 1e by a factor of ∼1.8 in the W band (ν = 95 GHz and B 0 ∼ 3.4 T) compared with that in the X band (ν = 9.4 GHz and B 0 ∼ 0.34 T).…”

“…Interaction of the nuclear spins with grafted paramagnetic Mn 2+ ions, carrying an electron spin S = 5/2 (electron configuration 3d 5 ), leads to the emergence of an additional relaxation channel of carbon nuclear spins, owing to their interaction with unpaired electron spins of the ions. Our measurements of the 13 C nuclear spin− lattice relaxation 23 showed a noticeable reduction in T 1 ( 13 C) with manganese grafting, from to T 1 = 575 ± 40 ms in the reference (non-grafted) sample to 133 ± 9 ms in the Mn-DND, respectively. This shortening of T 1 ( 13 C) is clearly visible in Figure 4.…”

“…Herewith, N S db,P1 (S = 1/2) turns out to be the same as in the reference DND sample 30 measured for comparison. The density of manganese ions corresponds to 8−9 Mn 2+ ions per Mn-DND particle, 23 which correlates with previously reported data on DND samples grafted with copper 14,15 and gadolinium. 16 13 C NMR measurements of the powder sample of Mn-DNDs were carried out at room temperature (RT) using a Tecmag pulse solid-state NMR spectrometer and an Oxford superconducting magnet in an external magnetic field B 0 = 8.0 T, corresponding to a 13 C resonance frequency of 85.62 MHz.…”

“…The approach was applied to a novel nanoma-terialhighly purified detonation nanodiamonds (DNDs) grafted with manganese ions, which is considered as a novel potential contrast agent for MRI. 23 According to our recent electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and conductometry study of this compound, 23 Mn 2+ ions are directly bound to the nanodiamond surface. Using our approach, we were able to determine the layer-by-layer contributions of the paramagnetic Mn 2+ ions to the spin−lattice relaxation and line width of 13 C carbon spins located at different depths from the diamond surface.…”

“…Using our approach, we were able to determine the layer-by-layer contributions of the paramagnetic Mn 2+ ions to the spin−lattice relaxation and line width of 13 C carbon spins located at different depths from the diamond surface. The distance between the Mn 2+ ions and the nanodiamond surface, determined earlier from the 13 C relaxation data, 23 was now also estimated from the second moments of the spectra. Being developed for nanodiamonds, the approach is nevertheless more general and can be successfully applied to the investigation and mapping of the effects of nuclear relaxation in various nanomaterials.…”