Proton Mobility Research Articles

The Impact of Nanoscale Percolation in Yttrium‐Doped BaZrO3 on the Oxygen Ion and Proton Conductivities: A Density Functional Theory and Kinetic Monte Carlo Study

Yttrium‐doped BaZrO3 is known for its high proton conductivity, making it an advanced energy material for various applications, like electrolyzers, fuel cells, or methane conversion cells. In the previous study, density functional theory (DFT) and kinetic Monte Carlo simulations (KMC) show that nanoscale percolation of Y ions enhances the proton mobility by providing fast migration pathways for protons. To investigate the general impact of nanoscale percolation on ionic conductivities, the same methods, DFT and KMC, are now used to calculate oxygen ion conductivity of Y‐doped BaZrO3. The results explain on a microscopic level why the macroscopic oxygen ion conductivity exhibits a higher activation energy than the proton conductivity, as known experimentally. They also show that nanoscale percolation pathways are not beneficial for oxygen ion conduction due to trapping of oxygen vacancies by single Y ions and blocking of their motion by nanoscale percolation of Y ions. Finally, the understanding and comparison of the microscopic jump processes of oxygen vacancies and of protons in acceptor‐doped BaZrO3 are used to propose a simple descriptor for the influence of a dopant on the ionic conductivities, of oxygen ions and of protons as well. This new descriptor allows an easy screening of various dopants.

Application of High-Frequency Conductivity Map Using MRI to Evaluate It in the Brain of Alzheimer's Disease Patients.

BackgroundThe previous studies reported increased concentrations of metallic ions, imbalanced Na+ and K+ ions, and the increased mobility of protons by microstructural disruptions in Alzheimer's disease (AD).Purpose(1) to apply a high-frequency conductivity (HFC) mapping technique using a clinical 3T MRI system, (2) compare HFC values in the brains of participants with AD, amnestic mild cognitive impairment (MCI), and cognitively normal (CN) elderly people, (3) evaluate the relationship between HFC values and cognitive decline, and (4) explore usefulness of HFC values as an imaging biomarker to evaluate the differentiation of AD from CN.Materials and MethodsThis prospective study included 74 participants (23 AD patients, 27 amnestic MCI patients, and 24 CN elderly people) to explore the clinical application of HFC mapping in the brain from March 2019 to August 2021. We performed statistical analyses to compare HFC maps between the three participant groups, evaluate the association of HFC maps with Mini-Mental State Examination (MMSE) scores, and to evaluate the differentiation between the participant groups for HFC values for some brain areas.ResultsWe obtained a good HFC map non-invasively. The HFC value was higher in the AD group than in the CN and MCI groups. MMSE scores were negatively associated with HFC values. Age was positively associated with HFC values. The HFC value in the insula has a high area under the receiver operating characteristic (ROC) curve (AUC) value to differentiate AD patients from the CN participants (Sensitivity [SE] = 82, Specificity [SP] =97, AUC = 0.902, p < 0.0001), better than gray matter volume (GMV) in hippocampus (SE = 79, SP = 83, AUC = 0.880, p < 0.0001). The classification for differentiating AD from CN was highest by adding the hippocampal GMV to the insular HFC value (SE = 87, SP = 87, AUC = 0.928, p < 0.0001).ConclusionHigh-frequency conductivity values were significantly increased in the AD group compared to the CN group and increased with age and disease severity. HFC values of the insula along with the GMV of the hippocampus can be used as an imaging biomarker to improve the differentiation of AD from CN.

Novel proton-conducting layered perovskite based on BaLaInO4 with two different cations in B-sublattice: Synthesis, hydration, ionic (O2−, H+) conductivity

The present study focused on the novel material with significantly improved properties for the application in the area of clean energy. The new complex oxide BaLaIn0·5Y0·5O4 with layered perovskite structure was obtained for the first time. It was proved that the introduction of Y3+ ions in the perovskite layer of BaLaInO4 leads i) to the rise of the oxygen-ionic conductivity due to the increase in mobility of oxygen ions as a result of the expand of the cell volume and ii) to the enhancement of protonic conductivity due to the increase in the proton concentration and mobility. The sample BaLaIn0·5Y0·5O4 is nearly pure proton conductor below 400 °C and has the protonic conductivity value 1.6∙10−5 S/cm at this temperature.

Study of proton mobility and thermal stability of novel orthophosphate-based composite electrolyte for conductivity improvement

Study of proton mobility and thermal stability of novel orthophosphate-based composite electrolyte for conductivity improvement

Comparing Proton Conduction in Potassium and Ammonium Borosulfate—Isostructural Inorganic Polyelectrolytes Exhibiting High Proton Mobility

A scalable new method for the synthesis of borosulfate compounds in sulfuric acid providing control over product crystallite size is reported as an alternative to traditional methods requiring slow growth from oleum. This new synthetic approach is used to prepare three isostructural, 1D borosulfates: one containing only ammonium cations, another containing only potassium cations, and the third sample with a solid solution of 1:1 ammonium–potassium. Proton conduction in polycrystalline pellets of these borosulfate electrolytes is compared by electrochemical impedance spectroscopy (EIS) and ab initio molecular dynamics (AIMD) simulations. For a given cation (e.g., NH4 +), conductivity decreases by three orders of magnitude with decreasing particle size while maintaining constant activation energy, indicating that proton conduction is not primarily a grain‐boundary process. AIMD simulations show that excess proton mobility in K[B(SO4)2] is in line with that of NH4[B(SO4)2], being a backbone (not cation) mediated process. Although K[B(SO4)2] exhibits higher activation energy (60.6 ± 2.0 kJ mol−1) than NH4[B(SO4)2] (33.8 ± 1.0 kJ mol−1), at 200 °C it achieves comparable conductivity to NH4[B(SO4)2] samples, which is attributable to hydrolytic B–O–H defects being the common source of mobile protons in these materials.

Assembly of two-dimensional nanofluidic channel with high proton conductivity using single-layer MnO2 nanosheets

Two-dimensional (2D) single-layer δ-MnO2 (SLMO) with cations intercalated in the interlayers demonstrates specific structural characteristics, possessing superiority in the fields such as energy storage, catalysis, and sensor. However, the synthesis technology of large-lateral-size SLMO nanosheets with high uniformity is rare, which hinders their correlated research. Herein, we report an intercalation-assisted exfoliation approach to produce large-sized SLMO nanosheets with high dispersity in aqueous solution. Few-layer K+-intercalated δ-MnO2 (KMnO) nanosheets were used as a precursor to ensure complete exfoliation. On account of high dispersion and ultrathin 2D morphology, SLMO nanosheets self-assembled into a flexible and free-standing film to construct ordered nanochannels. A high surface charge density of 1.71 mC m−2 and proton mobility of 2.59 × 10−3 cm2 V−1 s−1 were achieved in the free-standing SLMO film. With the extraordinary properties and easily scaled fabrication of the 2D SLMO film, this approach will pave the way for the study of confined ion transportation and enable the easy construction of nanofluidic devices.

Infrared fingerprints of water collective dynamics indicate proton transport in biological systems.

Recent publications on spectroscopy of water layers in water bridge structures revealed a significant enhancement of the proton mobility and the dielectric contribution of translational vibrations of water molecules in the interfacial layers compared to bulk water. Herewith, the results of long-term studies of proton dynamics in solid-state acids have shown that proton mobility increases significantly with the predominance of hydronium, but not Zundel, cations in the aqueous phase. In the present work, in the light of these data, we reanalyzed our previously published results on broadband dielectric spectroscopy of bovine heart cytochrome c, bovine serum albumin, and the extracellular matrix and filaments of Shewanella oneidensis MR-1. We revealed that, just as in water bridges, an increase in electrical conductivity in these systems correlates with an increase in the dielectric contribution of water molecular translational vibrations. In addition, the appearance of spectral signatures of the hydronium cations was observed only in those cases when the system revealed noticeable electrical conductivity due to delocalized charge carriers.

First‐principles analysis of proton conduction mechanism in perovskite‐structured sodium tantalate

AbstractWith the aim to elucidate the proton conduction mechanism in sodium tantalite with an orthorhombic perovskite structure, o‐NaTaO3, proton sites and elementary processes of proton jumps in the crystal were explored using first‐principles calculations. In this crystal, interoctahedral hopping plays a key role in the proton conduction, contrast to cubic perovskites where protons migrate over a long range only by rotation and intraoctahedral hopping. The interoctahedral hopping results from the tilting structure of TaO6 octahedra units, which accelerates the relatively fast proton migration along b‐ and c‐axes compared to that along a‐axis. This suggests that the low symmetry of the crystal structure can be beneficial to proton conduction in some cases, although the low symmetry is generally considered to make the potential barrier of long‐range proton migration higher. Considering the trapping effect of Ti dopants as the change in the concentration of mobile protons, the calculated proton conductivity is in excellent agreement with the experimental one.

Ultrafast rectifying counter-directional transport of proton and metal ions in metal-organic framework-based nanochannels.

Bioinspired control of ion transport at the subnanoscale has become a major focus in the fields of nanofluidics and membrane separation. It is fundamentally important to achieve rectifying ion-specific transport in artificial ion channels, but it remains a challenge. Here, we report a previously unidentified metal-organic framework nanochannel (MOF NC) nanofluidic system to achieve unidirectional ultrafast counter-directional transport of alkaline metal ions and proton. This highly effective ion-specific rectifying transport behavior is attributed to two distinct mechanisms for metal ions and proton, elucidated by theoretical simulations. Notably, the MOF NC exhibits ultrafast proton conduction stemming from ultrahigh proton mobility, i.e., 11.3 × 10−7 m2 /V·s, and low energy barrier of 0.075 eV in MIL-53-COOH subnanochannels. Furthermore, the MOF NC shows excellent osmotic power–harvesting performance in reverse electrodialysis. This work expects to inspire further research into multifunctional biomimetic ion channels for advanced nanofluidics, biomimetics, and separation applications.

Research on the Electrochemical Properties of Al2−x Zn x O3−α

To understand the electrochemical properties of the Al2O3 based proton conductor in more detail, a solid-state electrolyte Zn-doped Al2O3 was successfully prepared using the solid-state reaction method at the temperatures of 1873 K for 10 h. The phase structure and microscopic morphology of these materials are thoroughly investigated. The structural analysis results revealed that the electrolyte has a pure perovskite phase structure. The crystal grains are relatively uniform, the ceramic material is dense, and the relative density is greater than 97 percent, according to microscopic morphology analysis. The electrical conductivity of the specimen was measured using the two-terminal AC method to clarify the electrochemical properties of Zn-doped Al2O3. The H/D isotope effect of electrical conductivity was studied, and it was discovered that protons are the dominant charge carrier at temperatures ranging from 1073 to 1473 K in hydrogen-rich atmospheres. The electrochemical impedance spectroscopy test showed that in the temperature range of 1073K–1473 K, the conductivity of the sample increases with the increase of temperature, and the electrochemical performance of the sample is the best when the doping amount is x = 0.012. The conductance activation energy () is in the range of 1.01–1.62 eV in hydrogen-rich atmospheres. From the point of view of electromotive force measurement, the theoretical (computational) electrical potential matches the measured potential very well. In a hydrogen-rich atmosphere of 1073–1473 K, the proton mobility of Al2−x Zn x O3−α exceeds 0.90. In this work, we proved that Al2−x Zn x O3−α sample is a proton conductor.

Starch structure and exchangeable protons contribute to reduced aging of high-amylose wheat bread

Breads were prepared from wild-type wheat flour (WTWF) and high-amylose wheat flour (HAWF) with amylose content (AM) 71% and 84%. Melting enthalpy of recrystallized amylopectin (ΔHAP) increased significantly on storage for wild-type (WT), slightly for 71% AM but not at all for bread with 84% AM. Firmness of bread was positively related to AM content and ΔHAP. Exchangeable proton populations and mobility in high-amylose wheat bread (HAWB) crumb were higher than WT bread measured by 1H T2 NMR, consistent with the higher water content needed to make doughs from HAWF leading to the crumb network being more plasticized and hindering crumb aging. Although starch recrystallization and bread firming increased, no increase in enzyme-resistant starch (RS) content was observed during bread aging, with RS content only dependent on AM content. Although HAWB has a harder crumb than wild-type, it has greater shelf-life stability and higher nutritional value.

Improved hydrogen sorption properties of Pd in protic and aprotic ionic liquids effected by superacid addition

The mixtures of selected protic and aprotic ionic liquids with their parent superacids were used as electrolytes in the process of hydrogen electrosorption in thin (ca. 0.5 µm) Pd films. The properties of ionic liquids and their mixtures with superacids were characterized with the use of electrochemical and physicochemical methods to show the perspectives of their potential utilization as electrolytes in hydride/protonic systems. Based on the electrochemical studies it was possible to estimate the minimum concentrations of the superacids in protic and aprotic ionic liquids which give maximum hydrogen absorption capacities in Pd (H/Pd). Unusual, previously unnoticed ‘two-step’ α→β phase transition was observed on the hydrogen electrosorption isotherm of Pd for the process of hydrogen absorption from the protic ionic liquids for some superacid concentrations. 1H NMR spectroscopy of the protic ionic liquids enables to discuss the relation between proton mobility and hydrogen electrosorption properties.

New monoclinic ruthenium dioxide with highly selective hydrogenation activity

HxRuO2 acts as a standalone catalyst exhibiting selective hydrogenation under mild conditions. Mobile protons embedded in the oxide lattice play an important role in stabilizing the distorted structure, and facile proton dynamics is key to improving catalytic properties.

Towards understanding the formation of internal fragments generated by collisionally activated dissociation for top-down mass spectrometry

Top-down mass spectrometry (TD-MS) generates fragment ions that returns information on the polypeptide amino acid sequence. In addition to terminal fragments, internal fragments that result from multiple cleavage events can also be formed. Traditionally, internal fragments are largely ignored due to a lack of available software to reliably assign them, mainly caused by a poor understanding of their formation mechanism. To accurately assign internal fragments, their formation process needs to be better understood. Here, we applied a statistical method to compare fragmentation patterns of internal and terminal fragments of peptides and proteins generated by collisionally activated dissociation (CAD). Internal fragments share similar fragmentation propensities with terminal fragments (e.g., enhanced cleavages N-terminal to proline and C-terminal to acidic residues), suggesting that their formation follows conventional CAD pathways. Internal fragments should be generated by subsequent cleavages of terminal fragments and their formation can be explained by the well-known mobile proton model. In addition, internal fragments can be coupled with terminal fragments to form complementary product ions that span the entire protein sequence. These enhance our understanding of internal fragment formation and can help improve sequencing algorithms to accurately assign internal fragments, which will ultimately lead to more efficient and comprehensive TD-MS analysis of proteins and proteoforms.

Proton dynamics in water confined at the interface of the graphene-MXene heterostructure.

Heterostructures of 2D materials offer a fertile ground to study ion transport and charge storage. Here, we use ab initio molecular dynamics to examine the proton-transfer/diffusion and redox behavior in a water layer confined in the graphene-Ti3C2O2 heterostructure. We find that in comparison with the similar interface of water confined between Ti3C2O2 layers, the proton redox rate in the dissimilar interface of graphene-Ti3C2O2 is much higher, owing to the very different interfacial structure as well as the interfacial electric field induced by an electron transfer in the latter. Water molecules in the dissimilar interface of the graphene-Ti3C2O2 heterostructure form a denser hydrogen-bond network with a preferred orientation of water molecules, leading to an increase in proton mobility with proton concentration in the graphene-Ti3C2O2 interface. As the proton concentration further increases, proton mobility decreases due to increasingly more frequent surface redox events that slow down proton mobility due to binding with surface O atoms. Our work provides important insights into how the dissimilar interface and their associated interfacial structure and properties impact proton transfer and redox in the confined space.

Self‐Healable Organic–Inorganic Hybrid Thermoelectric Materials with Excellent Ionic Thermoelectric Properties

AbstractSelf‐healable and stretchable thermoelectric (TE) materials provide new possibilities for self‐powered flexible wearable devices to self‐repair mechanical damage. However, developing high‐performance materials with such desirable TE and mechanical properties is a significant challenge. In this work, organic–inorganic ionic TE composites (OITCs) with an unprecedently high ionic TE figure of merit (ZTi = 3.74 at 80% relative humidity) and robust properties of simultaneous self‐healing and stretching are reported. The OITCs are developed by incorporating inorganic SiO2 nanoparticles (SiO2‐nps) in a polyaniline: poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid): phytic acid (PANI:PAAMPSA:PA) ternary polymer. The incorporated SiO2‐nps constructively interact with the hybrid polymer to provide autonomous self‐healability and stretchability while augmenting the mobile proton concentration in OITCs, which substantially improves their ionic TE properties (i.e., ionic Seebeck coefficient and ionic conductivity). Moreover, the OITCs remain repeatedly stretchable and self‐healable under severe external stresses (50 cycles of 100% strain and 25 cycles of cutting/healing) without degradation of their TE properties. Using the OITCs with multi‐walled carbon nanotube electrodes, an ionic TE supercapacitor (ITESC) with a maximum energy density of 19.4 mJ m−2 is demonstrated upon a temperature difference of 1.8 K.

Elucidating the Fragmentation Mechanism of Protonated Lewis A Trisaccharide using MSn CID.

Lewis blood group antigens are a prominent example of isomeric oligosaccharides with biological activity. Understanding the fragmentation mechanism in the gas phase is essential for their identification and assignment by mass spectrometric methods such as ESI-MS. In this work, the [M + H]+ species of Lewis A trisaccharide and Lewis A trisaccharide methyl glycoside were studied by ESI-MS with FT-ICR as mass analyzer with respect to their fragmentation mechanism. The comparison between the underivatized and the methylated species has shown that the reducing end plays a key role in this mechanism. The results of this study question the existence of Z-type fragment ions after activation of the protonated species. The main product of the fragmentation are Y-type fragment ions and a combination of Y-type fragmentation and the loss of water at the reducing end instead of Z-type fragmentation. C-type fragment ions could not be detected. MS3 measurements also reveal that each fragment ion only occurs with the participation of a mobile proton and the possibility of glycosidic bond cleavage after fragmentation has already occurred at the reducing end as B2 fragment ion.

The Proton in Biochemistry: Impacts on Bioenergetics, Biophysical Chemistry, and Bioorganic Chemistry.

The proton is the smallest atomic particle, and in aqueous solution it is the smallest hydrated ion, having only two waters in its first hydration shell. In this article we survey key aspects of the proton in chemistry and biochemistry, starting with the definitions of pH and pK a and their application inside biological cells. This includes an exploration of pH in nanoscale spaces, distinguishing between bulk and interfacial phases. We survey the Eigen and Zundel models of the structure of the hydrated proton, and how these can be used to explain: a) the behavior of protons at the water-hydrophobic interface, and b) the extraordinarily high mobility of protons in bulk water via Grotthuss hopping, and inside proteins via proton wires. Lastly, we survey key aspects of the effect of proton concentration and proton transfer on biochemical reactions including ligand binding and enzyme catalysis, as well as pH effects on biochemical thermodynamics, including the Chemiosmotic Theory. We find, for example, that the spontaneity of ATP hydrolysis at pH ≥ 7 is not due to any inherent property of ATP (or ADP or phosphate), but rather to the low concentration of H+. Additionally, we show that acidification due to fermentation does not derive from the organic acid waste products, but rather from the proton produced by ATP hydrolysis.

Basics of the Development of Microwave Intensification of Upstream on the Example of &lt;i&gt;Escherichia coli&lt;/i&gt;

Introduction. E. coli strains are the main microorganisms used for the production of a number of important biopharmaceutical products. There are no natural sources of microwave radiation on Earth, as it is absorbed by the upper atmosphere. No one doubts the importance of studying the biological effect of microwave radiation. The number of publications devoted to this problem is growing every year, and new ideas for the use of microwaves in drug production technology are emerging.Aim. Reveal the main effects of microwave irradiation and develop a technology for microwave intensification of E. coli culture growth.Materials and methods. This study presents the results of atomic force microscopy, refractometry, NMR relaxometry, turbidimetry, and lumimetry, demonstrating the possibility of microwave intensification of the cultivation process.Results and discussion. It was found that microwave irradiation leads to changes in the mobility of protons and the adsorption of water molecules on biopolymers and cells. These are the main links in the mechanism of "non-thermal" microwave action. A single microwave irradiation, depending on a number of parameters, can decrease or increase the growth of biomass. Studies of the bioluminescence of the E. coli strain with the lux-operon have shown that the optimal processing conditions do not negatively affect the luciferase production and metabolic activity of cells. Conclusion. The intensification procedure using microwave radiation can be considered a promising method and can provide new ideas for various applications in biotechnology.

Quantifying proton diffusion in acid-functionalized chitosan membranes

We explore proton diffusion in hydrated, maleic-acid-functionalized chitosan membranes using ab initio molecular dynamics (AIMD) simulations. Our simulations show that more frequent proton hopping between water molecules leads to an increase in the proton diffusion coefficient at higher water content in membranes based on 50 and 100% de-acetylated maleic chitosan. Moreover, mobile protons interact with the oxygen atoms of the 50% de-acetylated polymer’s acetyl groups, making them susceptible to protonation. The maleic acid group’s three oxygen atoms hydrogen-bond to water molecules in the membrane channels and are protonated less frequently than the acetyl groups.