Natural Abundance ¹⁷O DNP Two-Dimensional and Surface-Enhanced NMR Spectroscopy

Due to its extremely low natural abundance and quadrupolar nature, the ¹⁷O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to ¹⁷O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from ¹H. Here, we demonstrate new DNP-based measurements that extend ¹⁷O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional ¹H–¹⁷O cross-polarization greatly improves the sensitivity and enables the facile measurement of undistorted line shapes and two-dimensional ¹H–¹⁷O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone ¹⁷O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. Lastly, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the ¹⁷O nuclide

Measuring Long-Range ¹³C–¹³C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid-State Nuclear Magnetic Resonance

We report that spatial (<1 nm) proximity between different molecules in solid bulk materials and, for the first time, different moieties on the surface of a catalyst, can be established without isotope enrichment by means of homonuclear CHHC solid-state nuclear magnetic resonance experiment. This ¹³C–¹³C correlation measurement, which hitherto was not possible for natural-abundance solids, was enabled by the use of dynamic nuclear polarization. Importantly, it allows the study of long-range correlations in a variety of materials with high resolution

Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi_1/3Mn_1/3Co_1/3O₂

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class “safe” lithium polymer batteries without flammable liquid electrolyte

Mechanism of Solid-State Thermolysis of Ammonia Borane: A ¹⁵N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

The solid-state thermolysis of ammonia borane (NH₃BH₃, AB) was explored using state-of-the-art ¹⁵N solid-state NMR spectroscopy, including 2D indirectly detected ¹H­{¹⁵N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced ¹⁵N­{¹H} cross-polarization experiments as well as ¹¹B NMR. The complementary use of ¹⁵N and ¹¹B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of ABinsights that have not been available by ¹¹B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane

Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi_1/3Mn_1/3Co_1/3O₂

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class “safe” lithium polymer batteries without flammable liquid electrolyte

Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi_1/3Mn_1/3Co_1/3O₂

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class “safe” lithium polymer batteries without flammable liquid electrolyte

Oxidation Reaction of Polyether-Based Material and Its Suppression in Lithium Rechargeable Battery Using 4 V Class Cathode, LiNi_1/3Mn_1/3Co_1/3O₂

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class “safe” lithium polymer batteries without flammable liquid electrolyte

Hyperthermic treatment of DMBA-induced rat mammary cancer using magnetic nanoparticles-3

<p><b>Copyright information:</b></p><p>Taken from "Hyperthermic treatment of DMBA-induced rat mammary cancer using magnetic nanoparticles"</p><p>http://www.biomagres.com/content/6/1/2</p><p>Biomagnetic Research and Technology 2008;6():2-2.</p><p>Published online 25 Feb 2008</p><p>PMCID:PMC2266920.</p><p></p

Solid-State NMR Study of Li-Assisted Dehydrogenation of Ammonia Borane

The mechanism of thermochemical dehydrogenation of the 1:3 mixture of Li₃AlH₆ and NH₃BH₃ (AB) has been studied by the extensive use of solid-state NMR spectroscopy and theoretical calculations. The activation energy for the dehydrogenation is estimated to be 110 kJ mol^–1, which is lower than for pristine AB (184 kJ mol^–1). The major hydrogen release from the mixture occurs at 60 and 72 °C, which compares favorably with pristine AB and related hydrogen storage materials, such as lithium amidoborane (LiNH₂BH₃, LiAB). The NMR studies suggest that Li₃AlH₆ improves the dehydrogenation kinetics of AB by forming an intermediate compound (LiAB)_<i>x</i>(AB)_1–<i>x</i>. A part of AB in the mixture transforms into LiAB to form this intermediate, which accelerates the subsequent formation of branched polyaminoborane species and further release of hydrogen. The detailed reaction mechanism, in particular the role of lithium, revealed in the present study highlights new opportunities for using ammonia borane and its derivatives as hydrogen storage materials

Molecular-Level Consequences of Biomass Pretreatment by Dilute Sulfuric Acid at Various Temperatures

<i>Ex situ</i> room-temperature ¹³C nuclear magnetic resonance (NMR) measurements are reported on powdered poplar wood that has been pretreated with dilute sulfuric acid (concentrations up to 1 wt %) for times ranging up to 20 min and at temperatures of 120, 130, 140, and 150 °C. There are significant, albeit not dramatic, changes in the measured NMR spectra of the biomass as result of dilute sulfuric acid treatment. Values of <i>T</i>₁ for ¹³C and ¹H, as well as <i>T</i>_CH and <i>T</i>_1ρH, were measured for lignin peaks and cellulose peaks in the ¹³C NMR spectra, as potential indicators of the degree of atomic-level motion. For lignin components, one finds a trend to larger <i>T</i>_CH values as the treatment time or H₂SO₄ concentration is increased for treatment temperatures of 120 and 130 °C; however, for treatment temperatures of 140 and 150 °C, <i>T</i>_CH apparently decreases as the treatment time is increased. This higher temperature <i>T</i>_CH behavior implies that the lignin may actually become more rigid at later stages of treatment at temperatures ≥140 °C, which can be explained by cleavages of ether linkages of lignin and subsequent formation of new linkages, i.e., lignin recondensation. <i>T</i>_1C and <i>T</i>_1H measurements are consistent with this interpretation. The relationships between atomic-level mobility of lignin in biomass and treatment temperature is consistent with published relationships between the sugar yield and treatment temperature. The key role of acid treatment as a pretreatment for enzymatic digestion is evident in NMR measurements, including relaxation measurements, even after the treatment