Anisotropic relaxation of nuclear spins dipolar energy of water molecules in two-dimensional nanopores - A single crystal NMR study.

Energy transfer from Zeeman to dipolar order discovered by Jeener et al. is usually observed in solids with a strong dipole-dipole interaction of nuclear spins. It is not observed in liquids, where fast molecular motion completely averages this interaction.

Magnetic Resonance Study of Bulky CVD Diamond Disc.

Diamonds produced using chemical vapor deposition (CVD) have found many applications in various fields of science and technology. Many applications involve polycrystalline CVD diamond films of micron thicknesses. However, a variety of optical, thermal, mechanical, and radiation sensing applications require more bulky CVD diamond samples.

Investigation of PZT Materials for Reliable Piezostack Deformable Mirror with Modular Design.

This article presents a study of the electrophysical properties of a piezoceramic material for use in adaptive optics. The key characteristics that may be important for the manufacturing of piezoelectric deformable mirrors are the following: piezoelectric constants (d, d, d), capacitance, elastic compliance values s for different crystal directions, and the dielectric loss tangent (tgδ). Based on PZT ceramics, the PKP-12 material was developed with high values of the dielectric constant, piezoelectric modulus, and electromechanical coupling coefficients.

Multicomponents of spin-spin relaxation, anisotropy of the echo decay, and nanoporous sample structure.

We have experimentally and theoretically investigated multicomponent H nuclear magnetic resonance (NMR) echo decays in a-Si:H films containing anisotropic nanopores, in which randomly moving hydrogen molecules are entrapped. The experimental results are interpreted within the framework of the previously developed theory, in which a nanoporous material is represented as a set of nanopores containing liquid or gas, and the relaxation rate is determined by the dipole-dipole spin interaction, considering the restricted motion of molecules inside the pores. Previously, such characteristics of a nanostructure as the average volume of pores and their orientation distribution were determined from the angular dependences of the spin-spin and spin-lattice relaxation times.

Nanostructure of hydrogenated amorphous silicon (a-Si:H) films studied by nuclear magnetic resonance.

The aim of this work is to investigate the nanostructures of nanoporous materials by studying the anisotropy of the nuclear spin-spin and spin-lattice relaxations of the guest molecules trapped in the pores. The nuclear magnetic resonance (NMR) data are analyzed in the framework of the theory of the nuclear relaxation dominated by the dipole-dipole interactions in gas or liquid species contained in nanopores. A distinctive feature of this theory is the establishment of a relationship between the degree of orientation ordering of nanopores in the host matrix and their characteristic volume and the anisotropy of the NMR relaxation times.

Universal Dependence of Nuclear Spin Relaxation on the Concentration of Paramagnetic Centers in Nano- and Microdiamonds.

An analysis of our data on H and C spin-lattice and spin-spin relaxation times and rates in aqueous suspensions of purified nanodiamonds produced by detonation technique (DNDs), DNDs with grafted paramagnetic ions, and micro- and nanodiamonds produced by milling bulk high-temperature high-pressure diamonds is presented. It has been established that in all the studied materials, the relaxation rates depend linearly on the concentration of diamond particles in suspensions, the concentration of grafted paramagnetic ions, and surface paramagnetic defects produced by milling, while the relaxation times exhibit a hyperbolic dependence on the concentration of paramagnetic centers. This is a universal law that is valid for suspensions, gels, and solids.

Anisotropy of transverse and longitudinal relaxations in liquids entrapped in nano- and micro-cavities of a plant stem.

We studied the anisotropy of H NMR spin-lattice and spin-spin relaxations in a fresh celery stem experimentally and modeled the sample theoretically as the water-containing nano- and micro-cavities. The angular dependence of the spin-lattice and the spin-spin relaxation times was obtained, which clearly shows the presence of water-filled nano- and micro-cavities in the celery stem, which have elongated shapes and are related to non-spherical vascular cells in the stem. To explain the experimental data, we applied the relaxation theory developed by us and used previously to interpret similar effects in liquids in nanocavities located in biological tissues such as cartilages and tendons.

PVP-coated Gd-grafted nanodiamonds as a novel and potentially safer contrast agent for in vivo MRI.

Purpose: Testing the potential use of saline suspension of polyvinylpyrrolidone (PVP)-coated gadolinium(Gd)-grafted detonation nanodiamonds (DND) as a novel contrast agent in MRI.

Methods: Stable saline suspensions of highly purified de-agglomerated Gd-grafted DND particles coated by a PVP protective shell were prepared. T and T proton relaxivities of the suspensions with varying gadolinium concentration were measured at 8 Tesla.

Examining relaxivities in suspensions of nanodiamonds grafted by magnetic entities: comparison of two approaches.

Objectives: Detonation nanodiamonds (DND) with Gd ions directly grafted to the DND surface have recently demonstrated enhanced relaxivity for protons in aqueous suspensions. Herewith, the relaxivity measurements were done on a series of suspensions with the gadolinium content varied by changing number of Gd ions grafted per each DND particle whereas the DND content in each suspension was kept the same. Such an approach to vary the contrast agent content differs from that commonly used in the relaxivity measurements.

Location of paramagnetic defects in detonation nanodiamond from proton spin-lattice relaxation data.

We developed an approach for determining location of intrinsic paramagnetic defects in nanodiamonds from the data of proton spin-lattice relaxation of the surface hydrogen atoms. The approach was applied to the detonation nanodiamond (DND) of the diameter of 5 nm. We found that dangling bonds with unpaired electron spins are located within the near-surface belt at the distance of 0.

Comment on "Angstrom-scale probing of paramagnetic center location in nanodiamonds by He NMR at low temperatures" by V. Kuzmin, K. Safiullin, G. Dolgorukov, A. Stanislavovas, E. Alakshin, T. Safin, B. Yavkin, S. Orlinskii, A. Kiiamov, M. Presnyakov, A. Klochkov and M. Tagirov, Phys. Chem. Chem. Phys., 2018, 20, 1476.

Kuzmin et al. reported on the application of the 3He NMR relaxometry technique to localization of intrinsic paramagnetic defects in detonation nanodiamond (DND) particles. We found some inconsistencies in the DND characterization, the model of paramagnetic defects' allocation used in that work as well as the estimation of distances between 3He NMR probes and paramagnetic defects, which question the results obtained.

Fluorescent single-digit detonation nanodiamond for biomedical applications.

Detonation nanodiamonds (DNDs) have emerged as promising candidates for a variety of biomedical applications, thanks to different physicochemical and biological properties, such as small size and reactive surfaces. In this study, we propose carbon dot decorated single digit (4-5 nm diameter) primary particles of detonation nanodiamond as promising fluorescent probes. Due to their intrinsic fluorescence originating from tiny (1-2 atomic layer thickness) carbonaceous structures on their surfaces, they exhibit brightness suitable for in vitro imaging.

Towards Determination of Distances Between Nanoparticles and Grafted Paramagnetic Ions by NMR Relaxation.

We developed an approach for determining distances between carbon nanoparticles and grafted paramagnetic ions and molecules by means of nuclear spin-lattice relaxation data. The approach was applied to copper-, cobalt- and gadolinium-grafted nanodiamonds, iron-grafted graphenes, manganese-grafted graphene oxide and activated carbon fibers that adsorb paramagnetic oxygen molecules. Our findings show that the aforementioned distances vary in the range of 2.

Na and Al NMR Study of Structure and Dynamics in Mordenite.

Temperature dependencies of Al and Na nuclear magnetic resonance spectra and spin-lattice relaxations in mordenite have been studied in static and magic angle spinning regimes. Our data show that the spin-lattice relaxations of the Na and Al nuclei are mainly governed by interaction of nuclear quadrupole moments with electric field gradients of the crystal, modulated by translational motion of water molecules in the mordenite channels. At temperatures below 200 K, the dipolar interaction of nuclear spins with paramagnetic impurities becomes an important relaxation mechanism of the Na and Al nuclei.

Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO.

This work demonstrates the potential of porous BaTiO for piezoelectric sensor and energy-harvesting applications by manufacture of materials, detailed characterisation and application of new models. Ferroelectric macro-porous BaTiO ceramics for piezoelectric applications are manufactured for a range of relative densities,  = 0.30-0.

(1)H NMR study of water molecules confined in nanochannels of mordenite.

Behavior of water molecules entrapped in nanochannels of zeolite mordenite has been investigated by (1)H NMR technique. The (1)H spectra and spin-lattice relaxation times in the laboratory and rotating frames, T1 and T1ρ, respectively, as well as the dipolar relaxation time T1D have been measured in the temperature range from 96 to 351K. Diffusion of water molecules along the channels was observed above ~200K.

Structure and Bonding in Chlorine-Functionalized Nanodiamond--Nuclear Magnetic Resonance and X-Ray Photoelectron Spectroscopy Study.

We report on investigation of detonation nanodiamond annealed at 800C°in chlorine atmosphere by means of 1H, 13C and 35Cl nuclear magnetic resonance and X-ray photoelectron spectroscopy. The results of these methods are found to be consistent with each other and evidence formation of chlorine-carbon groups and sp2 carbon shell on the nanodiamond surface. The data obtained provide detailed information about the structure and bonding in this diamond nanoparticle.

Effect of magic angle spinning on (13)C spin-lattice and spin-spin relaxation in nanodiamonds.

We report on (13)C spin-lattice (R 1) and spin-spin (R 2) relaxation rate dependence on magic-angle-spinning (MAS) rate in highly purified synthetic nanodiamonds. Noticeable slowdown of both relaxation processes and reduction of nuclear spin diffusion coefficient D with increasing MAS rate was obtained. This effect is attributed to suppression of nuclear spin diffusion by MAS.

Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds.

Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and (13)C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes.

(13)C spin-lattice relaxation in nanodiamonds in static and magic angle spinning regimes.

We report on (13)C nuclear spin-lattice relaxation time (T1) dependence on the magic-angle-spinning (MAS) rate in powder nanodiamond samples. We confirm that the relaxation is caused by interaction of nuclear spins with fluctuating electron spins of localized paramagnetic defects. It was found that T1 is practically not affected by MAS for small particles, while for larger particles with lower defect density T1 is different in static and MAS regimes and reveals elongation with increasing MAS rate.

Proton spin diffusion in a nanodiamond.

We report on a proton magnetic resonance study of a powder nanodiamond sample. We show that (1)H 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 [Formula: see text] in different external magnetic fields.

Nanodiamond graphitization: a magnetic resonance study.

We report on the first nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) study of the high-temperature nanodiamond-to-onion transformation. (1)H, (13)C NMR and EPR spectra of the initial nanodiamond samples and those annealed at 600, 700, 800 and 1800 ° C were measured. For the samples annealed at 600 to 800 ° C, our NMR data reveal the early stages of the surface modification, as well as a progressive increase in sp(2) carbon content with increased annealing temperature.

Hahn-echo decay for exchange-coupled nuclear spins in solids.

In this paper we present a simple model to calculate the Hahn-echo decay of the exchange-coupled nuclear spins in solids. Satisfactory agreement between the calculated and experimentally observed echo decay of the exchange-coupled spins of T203l and T205l isotopes in thallium chloride TlCl and thallium tantalum sulfide TlTaS(3) is obtained.