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Decreasing VPTT immediately after slightly increasing VPTT in water/DMSO mixtures and monotonically increasing VPTT in water/acetone mixtures of poly(N,N-diethylacrylamide) gels are displayed.

Nanodiamond (ND) polarizer can be used for dynamic nuclear polarization (DNP), owing to unpaired electrons provided by surface defects. However, 1H enhancement via Overhauser DNP (ODNP) using ND in-situ liquid has been found much smaller than traditional radicals. Herein, we study the surface properties of ND using electron spin resonance (ESR) and Raman methods firstly. Then the enhancement of 1H ODNP is explored using ND as polarizer with different nanoparticle sizes and concentrations at home-built 0.06 T DNP spectrometer. The surface of ND with the size of 30 nm is further modification via high temperature air oxidized and the enhancement was measured. The results show that nanoparticle sizes and Raman peak intensity ratio of sp2/sp3 hybridization are approximate negative correlation and positive correlation to enhancement, respectively. Furthermore, there is no significant enhancement in the oxidation group, and a −22.5-fold 1H ODNP enhancement is achieved in-situ liquid at room temperature, which demonstrate the ND can be used as an efficient enhancer. We expect ND to play a greater role in biomedical research, especially for multimodal imaging with improving the performance of ND surface.

The limitations of conventional organic liquid electrolytes such as sodium dendrite growth, serious side reactions, and liquid leakage hinder the development of sodium–metal batteries (SMBs). In th...

The glass transition of supercooled water is not well understood yet. We have observed a clear glass transition of the supercooled water confined in channel of amphiphilic polymer films at 145 K. Using NMR, we probe two types of relaxations occurred in the glass former, e.g., a rapid local β-process and a slow α-process (most likely). It is found that slow α-relaxation follows the Arrhenius relationship, indicating the glass former is a strong liquid. We also find a dynamic crossover from low-temperature Arrhenius α-process to high-temperature VFT process at 198-208 K, accompanying with simultaneous disappearing of local β-relaxation.

The fast Li-ion pathways in crystals contribute to superionic conductivity-extraordinarily high ionic conductivity-of the Li10GeP2S12 (LGPS) structure. Composition tuning is expected to improve the conductivity. The phase behavior, microstructure, and ion dynamics of a series of solid solutions of xLi4GeS4-yLi3PS4 (4/1 ≥ x/y ≥ 1/2) were studied by multiple 7Li and 31P solid-state NMR methods. Li10GeP2S12 (Ge/P = x/y = 1/2) is the smallest x/y of the disordered LGPS structure. When the Ge/P ratio increases, the room-temperature Li ionic conductivity first increases to a maximum around x/y = 1/1.2 and then decreases. Meanwhile, a disordered LGPS structure transforms into an ordered LGPS' structure synchronously with conductivity reduction. The Li4GeS4-Li3PS4 phase diagram with the order-disorder structure transition was reconstructed accordingly. Both ordered LGPS' and disordered LGPS exhibit similar two-dimensional (2D) and one-dimensional (1D) Li diffusion paths. But the disordered LGPS structure is conducive to fast ionic conductivity, rooted in its fast 2D Li+ diffusion in the ab-plane rather than 1D diffusion along the c-axis. Two high-temperature relaxation processes are observed in the LGPS' structure, suggesting heterogeneous 2D jumps of rapid and slow rates, whereas only a single homogeneous 2D jump process was found in the LGPS structure. Our findings provide insight into understanding the relationship between structure order (or disorder) and ionic conductivity of superionic materials, offering guidelines for optimizing ionic conductivity for extensive solid electrolyte materials rather than LGPS materials.

Finding sodium solid electrolytes (SSEs) with good performance is key to building all-solid-state sodium batteries. In the development of solid electrolytes, halogen doping has been shown to be an ...

Fast ion conduction in solid-state matrices constitutes the foundation for a wide spectrum of electrochemical systems that use solid electrolytes (SEs), examples of which include solid-state batteries (SSBs), solid oxide fuel cells (SOFCs), and diversified gas sensors. Mixing different solid conductors to form composite solid electrolytes (CSEs) introduces unique opportunities for SEs to possess exceptional overall performance far superior to their individual parental solids, thanks to the abundant chemistry and physics at the new interfaces thus created. In this review, we provide a comprehensive and in-depth examination of the development and understanding of CSEs for SSBs, with special focus on their physiochemical properties and mechanisms of ion transport therein. The origin of the enhanced ionic conductivity in CSEs relative to their single-phase parents is discussed in the context of defect chemistry and interfacial reactions. The models/theories for ion movement in diversified composites are critically reviewed to interrogate a general strategy to the design of novel CSEs, while properties such as mechanical strength and electrochemical stability are discussed in view of their perspective applications in lithium metal batteries and beyond. As an integral component of understanding how ions interact with their composite environments, characterization techniques to probe the ion transport kinetics across different temporal and spatial time scales are also summarized.

Low-cost hierarchical porous carbon materials with a controllable structure and high specific surface area as well as large pore volume were synthesized by a one-step route involving SnO2@chitosan precursor carbonization and subsequent SnO2 template removal. We found that when HPC CISC-29 is applied as the electrode in the supercapacitor device, it exhibits both high specific capacity (260.4 F g−1) and excellent rate capacitance retention (81.9%) from 0.1 A g−1 to 10 A g−1. CISC-29 shows superiority compared to conventional activated carbons for which specific capacitance and capacitance retention are 100–200 F g−1 and 60–70%, respectively. Solid-state NMR and NLDFT porosity distribution results reveal that the high specific capacitance is most likely associated with the optimized hierarchical porous structure, e.g. rich small-size micropores and their good connection with large-size mesopores. Finally, CISC-29 was complexed with Se to construct a cathode for lithium selenium batteries. Se@CISC-29 shows excellent performance with a specific capacity of 1207.0 mA h g−1 at 0.1 A g−1.

Over-lithiated organosulfides, such as sulfurized polyacrylonitrile (SPAN), are promising candidates of lithium metal anode (LMA) protection since they could form robust solid electrolyte interphases (SEIs), which is the key toward stable lithium metal batteries. So far, the mechanism of over-lithiation and evolution of the electrode surface is poorly understood. Herein, several in situ techniques were employed to study the over-lithiation process in SPAN, including in situ Raman spectroscopy to reveal the chemical transformation and in situ electrochemical atomic force microscopy (EC-AFM) to visualize interfacial evolution. The results undoubtedly prove the breaking of the C-S bond and formation of the C-Li bond during the over-lithiation process. The nucleophilic C-Li could further trigger the decomposition of the electrolyte to form an inorganic-organic hybrid SEI on the surface of SPAN, which allows uniform Li deposition and significantly improves the cycle stability of LMAs, as supported by the in situ EC-AFM characterization as well as a series of full cell tests. New insights into the over-lithiation mechanism of SPAN should facilitate the design of organosulfides to construct stable lithium metal anodes.

Summary Developing low cost, yet high-voltage electrolyte is significant to improve the energy density and practicability of lithium metal batteries (LMBs). Low concentration electrolyte has significant merits in terms of cost and viscosity; however, their poor compatibility with high-voltage LMBs hinders its applications. Here, we develop a diluted low concentration electrolyte by replacing solvating cosolvent with a non-solvating cosolvent to facilitate the interaction between BF4− and Li+, resulting in optimized interfacial chemistry and suppressed side reaction. Thus, the high-loading Li-LiCoO2 full cells (20.4 mg cm−2) deliver outstanding cycling stability and rate performance at a cutoff voltage of 4.6 V. More impressively, a Li-LiCoO2 pouch cell achieves an energy density of more than 400 Wh kg−1 under practical conditions with thin Li (50 μm) and lean electrolyte (2.7 g Ah−1). This work provides a rational approach to design a low concentration electrolyte, which can be extended to other high voltage battery systems., Graphical abstract, Highlights • A low concentration electrolyte is designed for high-voltage lithium metal batteries • Low concentration electrolyte has advantages in terms of cost and viscosity • The addition of diluent can regulate the solvation structure and interface properties • A Li-LiCoO2 pouch cell achieves an energy density of more than 400 Wh kg−1, Electrochemistry; Energy storage; Materials science

Vanadium hexacyanoferrate (VHCF) with an open-framework crystal structure is a promising cathode material for rechargeable aqueous metal-ion batteries owing to its high electrochemical performance and easy synthesis. In this paper, vanadium hexacyanoferrate cathodes were first used for constructing rechargeable aqueous sodium-ion batteries (VHCF/WO3) and tested in the new-type electrolyte (NaP-4.6) consisting of a polyethylene glycol (PEG)/H2O/NaClO4 electrolyte with a low H+ concentration (molar ratio of [H2O]/[Na+] is 4.6), which has high stability at a high current density as high as 1000 mA g-1 with a capacity retention of 90.3% after 2000 cycles at high coulombic efficiency (above 97.8%). To understand their outstanding performance, the proton-assisted sodium-ion storage mechanism and interphase chemistry of VHCF are investigated by solid-state NMR (ssNMR) technology. It is suggested that the H+ storage reaction is accompanied by the redox of vanadium atoms and Na+ intercalation is accompanied by the redox of iron atoms. It is also observed that the complex of polyethylene glycol (PEG) with Na+ (PEG-Na+) exists on the VHCF surface, which facilitates the stability of VHCF and promotes the alkali-ion transfer at a high current density. The results of the ssNMR study offer new insights into the intercalation chemistry of Prussian blue analogues with open-framework-structured compounds, which can greatly broaden our horizons for battery research.

Hierarchical porous graphitic carbon material is obtained by one-step vapor-assisted catalytic graphitization accompanied with chemical activation of phenolic resin. Water vapor is used to enhance the catalytic graphitization process by etching carbon layers coated on metal nanocatalysts to maintain their high catalytic activity, and the resultant hydrogen and carbon monoxide as strong reduction gases arising from water-gas shift reaction can promote the transformation of metal ions to metal catalysts. Thus, the resultant graphitic carbon exhibits hierarchical pore structure, large surface area and high graphitic degree, which is advantageous over conventional activated carbon materials in electrochemical energy storage. The applications of hierarchical porous graphitic carbon as electrode materials for supercapacitors, and host for sulfur in lithium-sulfur cells is demonstrated, which shows remarkably enhanced electrochemical performance due to the unique structure.

In this research, the bimetallic NiCoP nanoparticles and NiCoP/carbon nanotubes (CNTs) composites were successfully synthesized, and their performances as counter electrodes (CEs) for dye sensitized solar cells were investigated. The optimal composite CE (NiCoP-CNTs-3) exhibits outstanding photoelectric conversion efficiency (PCE) of 7.24%, which exceeds the single NiCoP (4.71%) or CNTs electrode (6.05%) and is on par with the standard Pt CE (7.12%) under same conditions. The electrochemical properties of NiCoP-CNTs electrodes were also characterized by utilizing the electrochemical impedance spectroscopy (EIS), Tafel polarization curves and cyclic-voltammetry (CV). The results indicate that NiCoP-CNTs-3 electrode holds Pt-like good electrocatalytic activity towards reduction of I3−. In addtion, the composite CE shows a reliably electrochemical stability. The present materials in this study may pave a way for the practical applications of Pt-free DSSCs.

Currently used aqueous electrolytes for lithium-ion batteries suffer from narrow potential windows of

Sodium superionic conductors are keys to develop high safety and low cost all-solid-state sodium batteries. Among developed sodium ionic conductors, antiperovskite-type ionic conductors have attracted vast interest due to their high structural tolerance and good formability. Herein, we successfully synthesize Na3OBH4 with cubic antiperovskite structure by solid-state reaction from Na2O and NaBH4. Na3OBH4 exhibits ionic conductivity of 4.4 × 10-3 S cm-1 at room temperature (1.1 × 10-2 S cm-1 at 328 K) and activation energy of 0.25 eV. The ionic conductivity is 4 orders of magnitude higher than the existing antiperovskite Na3OX (X = Cl, Br, I). It is shown that such enhancement is not only due to the specific cubic antiperovskite structure of Na3OBH4 but also because of the rotation of BH4 cluster anion. This work deepens the understanding of the antiperovskite structure and the role of cluster anions for superionic conduction.

The effects of salts on protein systems are not yet fully understood. We investigated the ionic dynamics of three halide salts (NaI, NaBr, and NaCl) with two protein models, namely poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA), using multinuclear NMR, dispersion corrected density functional theory (DFT-D) calculations and dynamic light scattering (DLS) methods. The variation in ionic line-widths and chemical shifts induced by the polymers clearly illustrates that anions rather than cations interact directly with the polymers. From the variable temperature measurements of the NMR transverse relaxation rates of anions, which characterize the polymer–anion interaction intensities, the evolution behaviors of Cl−/Br−/I− during phase transitions are similar in each polymer system but differ between the two polymer systems. The NMR transverse relaxation rates of anions change synchronously with the phase transition of PNIPAM upon heating, but they drop rapidly and vanish about 3–4.5 °C before the phase transition of PDEA. By combining the DFT-D and DLS data, the relaxation results imply that anions escape from the interacting sites with PDEA prior to full polymer dehydration or collapse, which can be attributed to the lack of anion–NH interactions. The different dynamic evolutions of the anions in the PNIPAM and PDEA systems give us an important clue for understanding the micro-mechanism of protein folding in a complex salt aqueous solvent.

The crown-shaped 36-molybdate cluster organophosphonate-functionalized polyoxomolybdates with the highest nuclearity in organophosphonate-based polyoxometalate chemistry, (NH4 )19 Na7 H10 [Cu(H2 O)TeMo6 O21 {N(CH2 PO3 )3 }]6 ⋅31 H2 O, has been reported for the first time. The synthesized 36-molybdate cluster was characterized by routine techniques and tested as a heterogeneous catalyst for selective oxidation of sulfides with impressive catalytic and selective performances after heat treatment. High efficiency (TON=15333) was achieved in the selective oxidation of sulfides to sulfoxides, caused by the synergic effect between copper and polyoxomolybdates and the generation of the cuprous species during the heat treatment.

Two new indolo[3,2-b]carbazole-based metal-free organic dyes (D1 and D2) were synthesized by utilizing triphenylamine as the first donor which were connected to the second donor indolo[3,2-b]carbazole via 9-position and 8-position, respectively. The dyes were characterized by UV–visible absorption spectra and electrochemical analyses. The both two dyes showed intensive absorption spectra in the wavelength of 300–600 nm and narrow band gap of 2.29 eV for D1 and 2.16 eV for D2. The cyclic voltammetry indicated that the oxidative potentials and reductive potentials of the dyes were well matched with the energy levels of the I−/I3− redox couple and TiO2 conduction band, respectively. The substituted positions on the indolo[3,2-b]carbazole played important roles in tuning the photoelectronic properties. The dye D2 with 2, 8-substituted indolo[3,2-b]carbazole core shows wider absorption spectrum and lower dye aggregation than D1 with 3,9-substituted isomer. The best power conversion efficiency (PCE) of 6.34% is obtained by the dye D2 due to its wider absorption spectra and strong steric hindrance, which can effectively suppress the undesirable dye aggregation. The co-sensitization of D1 and D2 enhances IPCE response in the visible light region and further improves the PCE up to 7.03%.

Developing low-cost and high-performance Pt-free counter electrodes (CE) is of vital significance for the commercial DSSCs application. Herein, three kinds of transition metal phosphates (Ni3(PO4)2, Co3(PO4)2, Ag3PO4) were separately composited with the conductive binder PEDOT and the yielded hybrid films were successfully used as counter electrodes for DSSCs. It is found that the content of the phosphates forcefully affects the performance of the composite CEs. Among these phosphates-PEDOT hybrid films, the Ni3(PO4)2-based composite CE with 50 mg/ml Ni3(PO4)2 in PEDOT precursor solution, shows the best power conversion efficiency (PCE) of 6.412%, which is higher than the original PEDOT PCE (5.443%) and comparable with the conventional magnetron sputtering Pt PCE (6.307%). Various analytical methods were utilized to investigate the origin of the improved power conversion efficiency (PCE). The results demonstrate that large active area, low charge transfer resistance and excellent electrocatalytic activity contribute to the outstanding PCE. Moreover, the optimizing PEDOT-Ni3(PO4)2-50 hybrid film CE exhibits good stability in the practical operation, demonstrating its potential for replacing the rare and expensive Pt CE.

The photovoltaic performance of dye-sensitized solar cell (DSSC) is strongly influenced by the electrocatalytic ability of its counter electrode (CE) materials. To obtain the affordable and high-performance electrocatalysts, the N/S dual-doped chitin-derived carbon materials SCCh were manufactured via in-situ S-doped method in the annealing process, where richer active sites are created compared to the pristine chitin-derived carbon matrix CCh, thus enhancing the intrinsic catalytic activity of carbon materials. When SCCh is incorporated with graphene, the yielded composites hold a further boosted catalytic activity due to facilitating the electronic fast transfer. The DSSC assembled with the optimizing rGO-SCCh-3 composite CE shows a favourable power conversion efficiency of 6.36%, which is comparable with that of the Pt-sputtering electrode (6.30%), indicate of the outstanding I3− reduction ability of the composite material. The electrochemical characterizations demonstrate that the low charge transfer resistance and excellent electrocatalytic activity all contribute to the superior photovoltaic performance. More importantly, the composite CE exhibits good electrochemical stability in the practical operation. In consideration of the low cost and the simple preparation procedure, the present metal-free carbonaceous composites could be used as a promising counter electrode material in future large scale production of DSSCs.

Lithium deposition on graphite electrode not only reduces fast-charging capability of lithium ion batteries but also causes safety trouble. Here, a low-field 7Li dynamic nuclear polarization (DNP) is used to probe Li plating on the surfaces of three types of carbon electrodes: hard carbon, soft carbon and graphite. Owing to the strong Fermi contact interaction between 7Li and conduction electrons, the 7Li nuclear-magnetic-resonance (NMR) signal of Li metal deposited on electrode surface could be selectively enhanced by DNP. It is suggested that low-field 7Li DNP spectroscopy is a sensitive tool for investigating Li deposition on electrodes during charging/discharging processes.

Dynamic nuclear polarization (DNP) technology can be utilized to dramatically enhance NMR signal. In this paper, we report on the development of a self-constructed 5 T DNP spectrometer for liquid samples and the 13C DNP enhancement achieved with this spectrometer. The DNP spectrometer is comprised of a wide-bore superconducting magnet, a home-made console, a dual resonance probe and a self-built 140 GHz microwave source for the spectrometer. Specifically, a microwave source of traveling wave tube (TWT) amplifier has been developed, which can provide a maximum power output of 4.4 W and a wide frequency tuning range of 1 GHz. The excellent performance of our built liquid-state DNP spectrometer is verified by the observation of more than 100-fold DNP enhancement of the 13C NMR signal for liquid 13CCl4 sample. Our result shows the superiority of DNP technology in the liquid-state high-field NMR spectrometer.

Elucidating the structure-activity relationship of curdlan is hampered by a lack of characterization with unique specific conformations (i.e., single- or triple-helix). In this study, single-helical curdlan is generated in dilute NaOH solutions at 35-50 °C, and characterized with NMR, SAXS, and GPC. The conformational transition from coil to single-helix and the intramolecular hydrogen bond interaction are explored using NMR. It is found that the two aforementioned types of curdlan interact with Congo Red in very different ways. Single-helical curdlan can encapsulate Congo Red to form a stable, supramolecular dye assembly, which is demonstrated by the shortest distance between the H3 of curdlan and the phenyl groups of Congo Red, and also the same self-diffusion coefficients of Congo Red and curdlan. In contrast, random-coil curdlan interacts weakly with Congo Red and cannot enwrap it. This study offers insight into the specific structure-activity relationship of beta-(1,3)-glucans.

A series of composite films based on LiFePO4/TiO2/Pt were synthesized and used as counter electrodes for dye sensitized solar cells (DSSCs). The composites are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET). These analysis results demonstrate that the crystal structure of LiFePO4 in composite is not changed, and the prepared LiFePO4/TiO2/Pt composite films hold a rough surface and porous structure which provide more catalytic activity sites for I3 − reduction and more space for I−/I3 − diffusion. The DSSC based on LiFePO4/TiO2/Pt composite CEs shows a high power conversion efficiency of 6.23% at a low Pt dosage of 2%, comparable to the conventional magnetron sputtering Pt CE (6.31%). The electrochemical analysis reveals that the presented composite CEs have good electrocatalytic activity and low charge transfer resistance. Furthermore, the DSSCs based on LiFePO4/TiO2/Pt composite CE exhibit high stability under the continuous tests condition and electrolyte soaking. The results suggest that this LiFePO4-based composite film could be a perspective electrode for practical application of DSSCs and it maybe provide a potential for further research about photo-charging lithium-ion batteries.

Cononsolvency of poly(N-isopropylacrylamide) (PNIPAM) gels in binary mixed solvents (water–acetone and water–DMSO) has been comparatively investigated by 1H HR-MAS NMR spectroscopy. The results demonstrate that, although the addition of both acetone and DMSO gives rise to cononsolvency behavior, PNIPAM preferentially interacts with acetone rather than DMSO in a water-rich regime, regardless of whether the temperature is above or below the volume phase transition temperature (VPTT). It suggests that the preferential adsorption of the additive cannot be deemed as a prerequisite for the cononsolvency in water-rich mixtures. The underlying molecular mechanism of cononsolvency involves a delicate balance between polymer–solvent and solvent–solvent interactions. Moreover, a new NOE-based NMR approach has been proposed to study the preferential adsorption in this work, which can be extensively adopted to study other relevant processes, including protein hydration, ligand binding, enzyme catalysis, etc.

Non-flammable and low-cost aqueous batteries operating on “M+/N+-dual shuttles” (AMIB) offer great opportunities in large-scale utility grid applications. Here, for the first time, we demonstrate a series of high-voltage AMIB (>1.23 V) based on open-framework copper hexacyanoferrates (CuHCFs) as cathode materials, and TiP2O7 & NaTi2(PO4)3 as anode materials. Among them, CuHCF/NaTi2(PO4)3 possesses high power density as an ultra-capacitor (3006 W kg−1), but with a higher energy density (56 W h kg−1). Through multiple characterization techniques combined with ab initio calculations, the intercalation chemistry of alkali cations in CuHCF is revealed. With increasing ionic size, the most stable interstitial site changes from the face-centered site (24d) to the body-centered site (8c). The intercalation voltage for the alkali cations follows the order: K+ > Na+ > Li+. Meanwhile, the ion-selectivity among them follows the same order as the intercalation voltage, which accounts for the higher voltage outputs of AMIB in contrast to aqueous batteries operating on one shuttle.

High resolution magic angle spinning (HR-MAS) NMR techniques provide effective atomic level characterization methods for heterogeneous systems such as tissues and polymer gels by sufficiently reducing the line broadening caused by the residual dipolar couplings or chemical shift anisotropy. In this chapter, the recent progress in HR-MAS NMR characterization of polymer gels is summarized. In particular, HR-MAS NMR methods for probing the network collapse dynamics and intermolecular interactions in thermo-responsive polymer gel systems are overviewed.

Vanadium hexacyanoferrate (VHCF) with an open-framework crystal structure is a promising cathode material for rechargeable aqueous metal-ion batteries owing to its high electrochemical performance and easy synthesis. In this paper, vanadium hexacyanoferrate cathodes were first used for constructing rechargeable aqueous sodium-ion batteries (VHCF/WO

This work provides a simple method for the preparation of thermoplastic chitosan using the most common dilute inorganic and organic acids in aqueous solutions, namely hydrochloric acid (HCl) and acetic acid (HAc). The melting plasticization behavior of chitosan under different concentrations and types of acid solution was investigated. By means of infrared spectra (IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and other characterization methods, as well as a mechanical property test, it was found that as the acid solution concentration increased, the protonation effect was stronger and the plasticization performance showed a better trend. The structure and performance of the modified chitosan were optimal when the concentration of HCl was around 8 wt %. In addition, it was found that HCl had a better effect on the plasticization of chitosan than HAc, which was because the protonation ability of HCl was stronger than that of HAc. Unlike the casting method, the structure and properties of chitosan sheets prepared by thermoplastic processing were directly affected by protonation, however not by the interaction of anionic-cationic electrostatic attractions between the &ndash, NH3+ groups of chitosan chains and the carboxyl groups of acetic acids or the chloridoid groups of hydrochloric acid.

Sodium superionic conductors are keys to develop high safety and low cost all-solid-state sodium batteries. Among developed sodium ionic conductors, antiperovskite-type ionic conductors have attracted vast interest due to their high structural tolerance and good formability. Herein, we successfully synthesize Na

Artificial intelligence sensations have aroused scientific interest from electronic conductors to bio-inspired ionic conductors. The conductivity of electrons decreases with increasing temperature, while the ionic conductivity agrees with an Arrhenius equation or a modified Vogel-Tammann-Fulcher (VTF) equation. Herein, thermo-responsive poly(N-isopropyl amide) (PNIPAm) and single-ion-conducting poly(2-acrylamido-2-methyl-1-propanesulfonic lithium salt) (PAMPSLi) were copolymerized via a facile radical polymerization to demonstrate a very intriguing anti-Arrhenius ionic conductivity behaviour during thermally induced volume-phase transition. These smart hydrogels presented very promising scaffolds for architecting flexible, wearable or advanced functional ionic devices.

Mapping B0-field and shim functions spatially is a crucial step in the gradient shimming. The conventional estimation method used in the phase difference imaging technique takes no account for noise and T2(∗) effects, and is prone to create noisy and distorted field maps. This paper describes a new gradient shimming based on the regularized estimation for B0-field and shim functions. Based on a statistical model, the B0-field and shim function maps are estimated by a Penalized Maximum Likelihood method that minimizes two regularized least-squares cost functions, respectively. The first cost function of B0-field exploits the two facts that the noise in the phase difference measurements is Gaussian and the B0-field maps tend to be smooth. And the other one adds an additional fact that each shim function corresponds to a given spherical harmonic of the magnetic field. Significant improvements in the quality of field mapping and in the final shimming results are demonstrated through computer simulations as well as experiments, especially when the magnetic field homogeneity is poor.

Our NMR experiments show that chitin can dissolve well in aqueous KOH through a freeze-thawing process, and the dissolution power of the alkali solvent systems is in the order of KOH > NaOH > LiOH aqueous solution, which is totally contrary to that of cellulose in the alkali aqueous solution (i.e., LiOH > NaOH ≫ KOH). In this work, we systematically study the dissolution process in KOH and KOH/urea aqueous solutions. Chitin has good solubility (solubility ~80 %) in 8.4–25 wt% KOH aqueous solution at −30 °C. The role of urea also has been investigated: unlike aqueous chitin-NaOH solutions, urea indeed enhances the solubility of chitin in KOH aqueous solutions, but the increased degree becomes unobtrusive with decreasing temperature and increasing dissolution time; the DA decline curves of chitin-KOH and chitin-KOH/urea aqueous solutions are nearly overlapping, indicating that the effect of the urea on the degree of acetylation of chitin in KOH aqueous solutions is small, similar to the NaOH/urea solvent.

1H MAS NMR spectroscopy has been applied to study the urea effect on phase transition of two similar thermosensitive polymer hydrogels: poly(N-isopropylacrylamide) (PNIPAM) and poly(N,N-diethylacrylamide) (PDEA). It is found that urea influences the phase transition of the hydrogels in opposite ways: lowering the lower critical solution temperature (LCST) of PNIPAM and hence stabilizing its globular structure, whereas raising the LCST of PDEA and destabilizing the globular structure. The self-diffusion coefficient and urea–polymer nuclear Overhauser effect (NOE) measurement reveal that urea has a stronger interaction with PNIPAM than with PDEA. Moreover, the enhanced positive water–PNIPAM NOE suggests that urea not only interacts directly with PNIPAM via hydrogen bond but also intensifies the hydrogen bonding interaction between water and PNIPAM. We suggest that different urea–polymer hydrogen bonding interaction due to the presence or absence of amide hydrogen is correlated with the distinct LCST variati...

We present a method to identify and sort the oils in oil-water mixtures based on the Overhauser dynamic nuclear polarization (ODNP) enhancement at low field. Through combining two types of radicals, e.g. ODNP enhancer TEMPO and relaxation reagent Mn2+, we can selectively enhance the 1H NMR signal of oil in oil-water mixture infiltrated in porous media. More importantly, we have found that the enhancements of light oils in porous materials are inversely dependent of their viscosities but independent of pore size approximately above 10 μm. This allows us to roughly sort oils according to their ODNP enhancement values. The verification experiments in sandstones saturated with several oil and water mixtures show that the method is useful for oils identification and classification in porous media, especially for reservoir assessment or development.

The low-temperature dissolving mechanism of chitin/chitosan in the alkali (LiOH, NaOH and KOH) aqueous solvents has not been well established yet. As revealed by our XRD and NMR methods, the prepared deacetylated chitins can be categorized as chitin (DA = 0.94-0.74), chitosan I (DA = 0.53-0.25) and chitosan II (DA 0.25). Aqueous alkali exhibits fully different dissolving power in the above three regions, i.e., KOH NaOH LiOH for chitin, KOH ≈ LiOH ≈ NaOH for chitosan I, and inverse LiOH KOH NaOH for chitosan II. While in the two-alkali mixed solvent, NaOH or KOH can destroy the interaction of LiOH with D9 (chitosan II region) in the order of NaOH KOH, but LiOH cannot destroy the interaction of KOH with raw chitin. The varied solubility of chitin/chitosan in alkali solvent is suggested to be from the cation's preferential interaction rather than OH

Li10GeP2S12 (LGPS) is a new solid electrolyte of the highest Li ionic conductivity reported as of now. An anisotropic 3D Li ionic transport network consisting of an ultrafast Li 1D diffusion tunnel and fast in-plane 2D pathways was previously predicted by molecular dynamics simulations. In this paper, we have studied in detail the Li ion dynamics in LGPS by multiple solid-state NMR methods. Two different Li motion processes, characterized by apparently different activation energies of 0.16 eV and 0.26 eV, were unambiguously probed by both 7Li and 31P solid-state NMR and assigned to Li ion diffusions in the 1D tunnel and in the 2D plane, respectively. 31P spin-locking relaxation measurement further reveals that interstitial position Li(4) is active for in-plane Li migration.

The low-temperature dissolution mechanism of chitin in NaOH/urea aqueous solution has not been well established yet, especially at a temperature that lowers the crystallization temperature of both NaOH and urea. Using multiple nuclei (H-1, N-15 and Na-23) nuclear magnetic resonance (NMR) methods, we find that the ternary NaOH/urea/D2O system, different from the fully frozen binary NaOH-D2O system, exhibits solid-liquid phase coexistence below -40 degrees C, and the residual liquid phase consists of certain concentrations of NaOH (10 wt%), urea (13 wt%) and D2O at -40 degrees C. Our NMR results further demonstrate that chitin dissolves in the residual liquid phase (containing 5-10 wt% NaOH and 8-12 wt% urea) at low temperatures (-40 and -70 degrees C). An important role of urea is enhancing the low-temperature stability of NaOH aqueous solutions and then increasing the dissolution temperature range of chitin, thus providing an essential low-temperature liquid environment for chitin dissolution.