Angstrom-scale probing of paramagnetic centers location in nanodiamonds by ³He NMR at low temperatures

Abstract

In this article a method to assess the location of paramagnetic centers in nanodiamonds was proposed. The nuclear magnetic relaxation of adsorbed He used as a probe in this method was studied at temperatures of 1.5-4.2 K and magnetic fields of 100-600 mT. A strong influence of the paramagnetic centers of the sample on theHe nuclear spin relaxation time T was found. Preplating the nanodiamond surface with adsorbed nitrogen layers allowed us to vary the distance from He nuclei to paramagnetic centers in a controlled way and to determine their location using a simple model. The observed T minima in temperature dependences are well described within the frame of the suggested model and consistent with the concentration of paramagnetic centers determined by electron paramagnetic resonance. The average distance found from the paramagnetic centers to the nanodiamond surface (0.5 ± 0.1 nm) confirms the well-known statement that paramagnetic centers in this type of nanodiamond are located in the carbon shell. The proposed method can be applied to detailed studies of nano-materials at low temperatures.

Nanodiamond enhanced mechanical and biological properties of extrudable gelatin hydrogel cross-linked with tannic acid and ferrous sulphate

“…3 c). The indexing of SAED pattern confirmed the crystal planes of ND at (111), (220), (311) [ 24 ]. SEM images revealed a porous structure of the crosslinked gels with and without ND (Fig.…”

Influence of the Chemical Modification of the Nanodiamond Surface on Electron Paramagnetic Resonance/Electron-Nuclear Double Resonance Spectra of Intrinsic Nitrogen Defects

“…Consequently, the lower limit on the distance from the paramagnetic center to the surface nuclei r min in accordance with expression where μ 0 magnetic constant, g e and g n electronic and nuclear g -factors, and β e and β n electronic and nuclear magnetons is r min ≈ 1.5 nm. For comparison, in paper, a method based on the NMR and nuclear relaxation times measurements of 3 He adsorbed on the ND surface was introduced which shows that ND paramagnetic centers responsible for the acceleration of 3 He nuclear relaxation are situated at the distance of about 0.5 nm from the surface. Hyperfine interaction of the intrinsic N 0 center with 13 C nuclei in bulk diamonds with very narrow EPR lines was studied in ref by conventional X-band EPR.…”

Production, surface modification, physicochemical properties, biocompatibility, and bioimaging applications of nanodiamonds

“…NDs can be characterized with various techniques. [112][113][114][115][116][117] As shown in low-and high (inset)-resolution transmission electron microscope (TEM) images in Fig. 3a-d and Table 1, the diameters of NDs largely depend on production method.…”

“…The broad peaks are owing to small particle sizes of NDs. 113,114 The Raman spectra of NDs produced by different methods exhibit a diamond peak from the C-C sp 3 chemical bond at 1332.9 cm −1 (Fig. 5).…”