The electron spin resonance technique has been applied to study the magnetization dynamics in broad temperature range in both concentrated magnetic fluid and diamagnetically diluted systems containing superparamagnetic maghemite nanoparticles. The ESR spectrum demonstrates an interesting double feature shape with a narrow peak near g=2, as well as “forbidden” resonances in low fields, and reveals strong dependence on temperature and nanoparticle concentration.The longitudinal spin-relaxation time was estimated. To describe the overall spectrum shape, a “quantization” model is used which involves summation of the resonance transitions corresponding to various orientations of the particle magnetic moment.

Ferromagnetic inductors with various geometries and permalloy thin film patterns were fabricated on the standard silicon substrate with a fully CMOS compatible process. The ferromagnetic resonance effects on the inductors were studied with the applied magnetic fields in different orientations. It showed that with the properly applied magnetic field, the ferromagnetic resonance for the patterned permalloy thin films can be pushed higher and the maximum quality factor for the ferromagnetic inductors can be improved. However, because the relative permeability decreases with increasing applied field, the trade-off between the effective inductance and the quality factor needs to be optimized for the practical designs.

Binary silicophosphate glasses containing between 7 and 35 mol% P2O5 were made by conventional melt quenching techniques and characterized by 29Si and 31P NMR spectroscopy. 31P and 29Si NMR data show that, as the P2O5 content is raised in these glasses, the network connectivity is decreased by a dilution of the silicate network with less polymerized Q3 phosphate groups. In addition to such changes in the network structure, 29Si NMR spectra for the most P2O5-rich glasses reveal the presence of silicon atoms with 5- and 6-fold coordination. These species increase in concentration with increasing P2O5 above approximately 30 mol% P2O5. Self-nucleating SiP2O7 glass-ceramics can be formed from the binary silicophosphate glasses with >25mol% P2O5. 29Si and 31P NMR results were used to monitor the crystallization of SiP2O7 by providing details on amount of crystallinity, relative grain sizes and even composition of the residual glassy matrix. Stabilization of octahedral Si as well as the onset of phase separation correlates with propensity for crystallization of SiP2O7 during subsequent heat treatment.

To understand amorphous and structurally disordered materials requires the application of a wide-range of advanced physical probe techniques and herein a combined methodology is outlined. The relatively short-range structural sensitivity of solid state NMR means that it is a core probe technique for characterizing such materials. The aspects of the solid state NMR contribution are emphasized here with examples given from a number of systems, with especial emphasis on the information available from 17O NMR in oxygen-containing materials. 17O NMR data for crystallization of pure sol-gel prepared oxides is compared, with new data presented from In2O3 and Sc2O3. Sol-gel formed oxide mixtures containing silica have been widely studied, but again the role and effect of the other added oxide varies widely. In a ternary ZrO2-TiO2-SiO2 silicate sol-gel the level of Q4 formation is dependent not only on the composition, as expected, but also the nature of the second added oxide. Sol-gel formed phosphates have been much less widely studied than silicates and some 31P NMR data from xerogel, sonogel and melt-quench glasses of the same composition are compared. The effect of small amounts of added antibacterial copper on phosphate glass networks is also explored.

Electron spin resonance (ESR) spectroscopy has become indispensable when it comes to the characterization on atomic-scale of structural, and correlated, electrical properties of actual semiconductor/insulator heterostructures. Through probing of paramagnetic point defects such as the Pb-type defects, E', and EX as a function of VUV irradiation and post deposition heat treatment, basic information as to the nature, quality, and thermal stability of the interface and interfacial regions can be established. This is illustrated by some specific examples of ESR analysis on contemporary Si/insulator structures promising for future developments in integrated circuits. First the impact of strain on the Si/SiO2 entity will be discussed. Through ESR analysis of thermally oxidized (111)Si substrates mechanically stressed in situ during oxidation, and tensile strained (100)sSi/SiO2 structures, it will be pointed out that in-plane tensile stress in Si can significantly improve the interface quality. Next, ESR results for stacks of (100)Si/SiOx/HfO2 and (100)Si/LaAlO3 are presented, revealing the potential to attain a high quality Si/SiO2 interface for the former and an abrupt, thermally stable interface for the latter.

Colloidal semiconductor nanocrystals or quantum dots are an important building block in bottom-up nanotechnology. They consist of an inorganic, crystalline core surrounded by a monolayer of organic ligands. As these ligands can be modified or exchanged for others, they provide a convenient way to give the quantum dots functionality. Here, we show that solution NMR techniques, including diffusion pulsed field gradient spectroscopy, is a very useful tool to investigate the ligands of colloidal nanocrystals. This is demonstrated using InP quantum dots with trioctylphospine oxide ligands as an example. Combining 1H-13C HSQC spectroscopy with pulsed field gradient diffusion NMR, an unequivocal identification of the resonances of the bound ligands is possible. This leads to the determination of the diffusion coefficient of the nanocrystals in solution and allows to verify capping exchange procedures. By calibrating the surface area of the NMR resonances using a solute of known concentration, the density of ligands at the nanocrystal surface can be quantified. We could demonstrate that a dynamic equilibrium exists between bound and free ligands. Analysis of the corresponding adsorption isotherm - determined using 1H NMR - leads to an estimation of the free energy of adsorption and the free energy of ligand-ligand interaction at the nanocrystals surface. Similar investigations are in progress on capped PbSe and ZnO2 nanoparticles. Preliminary results strongly support the generic nature of the approach described for the case of TOPO capped InP nanocrystals.

We have studied the effects of CO coverage on surface diffusion rates of CO adsorbed on nanoparticle Pt catalysts in sulfuric acid media by using 13C electrochemical nuclear magnetic resonance spectroscopy (EC-NMR) in the temperature range 253 - 293 K. For CO coverage from θ = 1.0 to 0.36, the diffusion coefficients follow Arrhenius behavior and both activation energy (E d) and pre-exponential factor (D co) show CO coverage dependence. Ed increases from 6.0 to 8.4 kcal/mol and DCO varies from 1.1 X 10-8 to 3.7 X 10-6 cm2/s when the coverage is increased from θ = 0.36 to θ = 1.0. On the Pt catalyst surface at partial CO coverage, our data strongly support the free site hopping model of adsorbed CO as the major surface diffusion mechanism, unlike the situation found with a fully CO covered surface where CO exchange between different surface sites is believed to be the major diffusion mechanism. Our results also indicate that the contributions of lateral repulsive interactions exert a stronger influence on the diffusive motion than does the nature of the surface structure. When the diffusion coefficient was estimated from CO stripping measurements by using an electrochemical modeling protocol, the estimated diffusion coefficients were a few orders of magnitude larger than those obtained from the EC-NMR experiments. Overall these results are important for improving our understanding of electrochemical surface dynamics of molecules at interfaces, and may help facilitate better control of fuel cell reactions where the presence of surface CO plays a crucial role in controlling the reaction rates.

The three versions of poly-styrene-ethylene/butylene-styrene (SEBS) triblock copolymers under investigation have different micro-scale morphologies: polystyrene (PS) spheres in poly-ethylene/butylene (EB) matrix, PS cylinders in EB matrix and EB cylinders in PS matrix. The diffusion phenomena of 2,2,4-trimethyl pentane (TMP) in SEBS probed with pulse field gradient NMR show distinct features related to the morphological characteristics. The micron scale size of grain boundaries may be obtained. In addition, the lattice model simulation was performed for the TMP diffusion in the membrane with spherical morphology.

A complete solid state NMR characterization of the vanadium oxides Cs[V3O8] and Cs2[V6O16].0.7H2O is proposed. We used 51V and 133Cs MAS NMR to investigate the local environment of cesium and vanadium nuclei and 2D 1H- 133Cs CP MAS HETCOR experiments to explore the connectivities between cesium ions and water molecules in the interlamellar space.

The water dynamics in molecular sieve materials are probe using high speed proton magic angle spinning NMR spectrscopy

The selection mechanism in the Discrimination Induced by Variable Angle Minipulse (DIVAM) sequence as a domain filter is investigated using spin dynamics simulations. Experiments on poly(vinylidinefluoride) (PVDF) show that 19F DIVAM selects on the basis of relaxation and the chemical shielding anisotropy interaction, where the role of the latter was confirmed by the simulations. The DIVAM filter was applied in domain selective 13C{1H,19F} experiments on poly[bis(trifluoroethoxy)-phosphazene] (PBFP). The resulting spectra were sensitive to morphological changes in the crystalline domain, which was not previously observed with 19F and 31P methods.

J-derived (HMQC, INEPT) and D-derived (double and triple resonance) experiments were applied to the detailed characterization of crystalline and amorphous silicophosphate derivatives. 31P/29Si and 1H/31P/29Si CP MAS experiments were suitable for the description of complex silicophosphate gels, which can act as precursors for biocompatible materials. First principles calculations involving the GIPAW approach (first developed by Mauri and Pickard) were applied for the determination of CSA (29Si, 31P, 17O) and quadrupolar (17O) parameters. Excellent agreement between experimental and calculated data was obtained.

We report the observation of a particularly simple effect of spin-orbit coupling which allows for efficient manipulation of spins by an electric current in semiconductor nanostructures. Passing an electric current density of j = 2.5 mA/cm through a modulation doped Si quantum well (density of 5 × 1011 cm-2) perpendicular to an in-plane magnetic field, we observe a shift of the spin resonance of the conduction electrons (CESR) by about 0.1 mT. This shift reverses sign when we invert (i) the current direction, (ii) the magnetic field direction and it vanishes for perpendicular magnetic field. We show that this current-induced shift in g-factor, i.e., its dependence on current and carrier density, its temperature dependence and its anisotropy can be consistently and quantitatively explained in terms of the Bychkov-Rashba coefficient determined earlier from the CESR broadening and the g-factor anisotropy [1]. Other sources of magnetic field (e.g. the Oersted effect) are negligible. This effect can be utilized for g-factor tuning, and thus for local spin manipulation: passing a current through some part of a sample may be utilized to bring those electrons into resonance with a microwave field. These spins are thus excited to Rabi oscillations and, using current pulses of suitable duration, π rotations (or by any other angle) can be achieved.

This paper illustrates the use of a 1H-29Si-1H double CP sequence to investigate different organic/SiO2 interfaces in templated porous silica. The advantage of this sequence is to selectively edit, in a one-dimensional experiment, the protons that are in close proximity with the Si surface sites. In order to maximize the polarization transfer efficiency, some experiments have been recorded at lower temperature (238 K). Examples will concern surfactant/silica interactions in mesostructured silicas and the behavior of benzoic acid and 4-methoxychlorophenol, a common pesticide, encapsulated in mesoporous silica.

Solid-state 13C and 207Pb NMR have been used to characterize a series of lead(II) ion complexes containing thiourea – widely used in materials science – as the organic complexing molecule. NMR data for the complexes have been measured and discussed with respect to the reported structures for the complexes.

Ultramarines are a family of pigments widely used as colorants in artists' paints, coatings, plastics, cosmetics, and various industrial materials. They are aluminosilicates characterized by a sodalite cage framework which enclarthrates paramagnetic (S3 -., S2 -.) and diamagnetic (S4 or S3Cl) chromophores responsible for the color of these pigments. Solid-state 27Al MAS NMR studies showed that the fading mechanisms in ultramarine pigments, both in acidic and alkaline environments, is initiated via de-alumination leading to framework destruction which in turn triggers the release of the chromophores. This results in color loss and in the emergence of extra-framework aluminum. 29Si MAS studies provide new insight into these processes and suggest that acidic attack leads to the formation of Q1-Q3 silicates and possibly to the emergence of Si(3Al), Si(2Al), Si(1Al) and Si(0Al) fragments indicative of the formation of secondary pores through which the guest chomophores can leave the cage. These findings are important for the design of proper conservation treatments and preservation procedures for artwork containing ultramarine pigments.

Hydrogels are multi-functional and can be used as scaffolds in bone tissue engineering. The pore architecture of the scaffolds is a significant factor in bone cell function. In this work, polyethylene glycol fumarate (OPF) hydrogel is used in the fabrication of porous scaffolds, and the effect of hydrogel porosity on bone formation is evaluated using an in vitro bone marrow stromal cell model. The porous hydrogels consist of copious amounts of water (90% or more by volume), and their structure is very similar to soft tissues. The characterization of porosity and interconnectivity in a typical OPF hydrogel scaffold and the bone formation inside the scaffold are assessed using magnetic resonance microscopy (MRM) techniques; and are shown to be very useful in micro structural studies of such water rich materials. A Bruker Avance 7 Tesla (proton 300 MHz) spectrometer equipped with a Micro Imaging 2.5 accessory is used in these studies. By optimizing the acquisition parameters such as relaxation recovery time (TR), echo time (TE), pulse flip angle (TA), and using solvent relaxation-enhancing media the pores and bone formations are clearly observed at an in plane resolution of 29 μm/pixel in various scaffold materials. Analysis of our MRM images data shows that the pores are highly interconnected and the porosity computed from the images correlate quite well with the experimental porosity parameters such as porogen size and percentage. In addition, the quantitative alkaline phosphatase activity, alizarin red staining as marker of osteoblastic differentiation and the mineralization capacity of marrow stromal cells are in good agreement with the bone formation seen in the MRM images.

Translational and rotational motions of dichloromethane were observed in a composite of poly(2,2-bis(trifluoromethyl)-4,5-difluoro-1,3-dioxole-co-tetrafluoroethylene), also referred to as AF1600, with fumed silica using NMR. Pulsed field gradient diffusion measurements show that adding fumed silica to AF1600 results in a great enhancement of the diffusion coefficient of dichloromethane. The diffusion enhancement behavior is similar to that previously reported in pentane, cyclohexane, and toluene in AF1600 nanocomposites. Spin-lattice relaxation time measurements of this system indicate two domains: one containing larger free volume elements (FVEs) that support faster dynamics and one containing smaller free volume elements that support slower dynamics. Adding the fumed silica disrupts the packing of polymer chains resulting in an increase of free volume and improved connections between domains supporting rapid translation. The lattice model simulation is performed to assist in understanding the mechanism of how the addition of fumed silica improves penetrant diffusion in nanocomposite polymer systems.

Electron spin resonance of graphite-like a-C thin films is investigated in the 20 K up to 340 K temperature range. The films with sp2 concentration of about 90 % (determined by electron energy loss spectroscopy), with no measurable optical band gap, were prepared by ion beam assisted sputtering. The results revealed an unexpected low density of paramagnetic centers, ascribed to itinerant states (conduction electrons) and not to localized states usually reported for a-C with band gap higher than 1.0 eV.

The local environment of niobium in oxides reflects the perturbations in bond strength that affect the acidity of oxygen atoms in the structure. To understand the relationship between metal environment and properties, 93Nb solid state NMR has been used to measure the electric field gradient and chemical shift anisotropy for layered niobates with either alkali cations or protons at the material surface. In order to determine these parameters, a variety of techniques have been applied to extract information for the multiple environments located in these oxides. Variable offset cumulative echo spectra were collected on static samples at multiple magnetic fields, 4.7 T, 9.4 T and 14.1 T. RAPT enhanced QPASS data were collected at 9.4 T to extract quadrupolar-coupling information without the influence of chemical shift anisotropy. Data from KCa2Nb3O10 and an acid exchanged form was collected and two distinct quadrupolar environments were observed. Acid exchange altered the isotropic chemical shift but did not significantly affect the electric field gradient or the chemical shift anisotropy.