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Protonation of oxide cathodes triggers surface transition metal dissolution and accelerates the performance degradation of Li-ion batteries. While strategies are developed to improve cathode material surface stability, little is known about the effects of protonation on bulk phase transitions in these cathode materials or their sodium-ion battery counterparts. Here, using NaNiO2 in electrolytes with different proton-generating levels as model systems, a holistic picture of the effect of incorporated protons is presented. Protonation of lattice oxygens stimulate transition metal migration to the alkaline layer and accelerates layered-rock-salt phase transition, which leads to bulk structure disintegration and anisotropic surface reconstruction layers formation. A cathode that undergoes severe protonation reactions attains a porous architecture corresponding to its multifold performance fade. This work reveals that interactions between electrolyte and cathode that result in protonation can dominate the structural reversibility/stability of bulk cathodes, and the insight sheds light for the development of future batteries.

Dimensional engineering is promising for achieving a high power conversion efficiency (PCE) and long‐term stability of perovskite solar cells (PSCs). However, insulated organic spacers in 2D perovskites often severely hinder carrier transport between the internal layers of devices. Herein, the “protonation‐induced localized transformation of 2D perovskites” is proposed to overcome the low carrier transport and conductivity of 2D/3D perovskite heterojunctions. Metformin, with its multiple amine groups and a substantial difference between its pKa value and perovskites, is protonated in an acidic environment or directly converted into the hydrochloride salt for the surface passivation of methylammonium lead iodide. This leads to the transformation of disorderedly oriented layered 2D perovskite into vertically oriented ones at grain boundaries. Consequently, the PCE of a carbon‐based PSC treated by protonated metformin increased considerably, reaching an optimal level of 14.13%. Additionally, applying this passivation strategy to a planar device (ITO/4PADCP/perovskite/PCBM/BCP/Ag) increased PCE from 20.82% to 22.09%, confirming the applicability of the strategy. To demonstrate the practical stability, an integrated PSC–supercapacitor device is assembled, which shows good cycling stability. This article introduces a novel method to improve carrier transport in 2D/3D perovskite heterojunctions, promoting the extensive utilization of dimensional engineering. [ABSTRACT FROM AUTHOR]

SUMMARY Post‐embryonic primary root growth is effectively an interplay of several hormone signalling pathways. Here, we show that the ABA‐responsive transcription factor ABI3 controls primary root growth through the regulation of JA signalling molecule JAZ1 along with ABA‐responsive factor ABI1. In the absence of ABI3, the primary root elongation zone is shortened with significantly reduced cell length. Expression analyses and ChIP‐based assays indicate that ABI3 negatively regulates JAZ1 expression by occupying its upstream regulatory sequence and enriching repressive histone modification mark H3K27 trimethylation, thereby occluding RNAPII occupancy. Previous studies have shown that JAZ1 interacts with ABI1, the protein phosphatase 2C, that works during ABA signalling. Our results indicate that in the absence of ABI3, when JAZ1 expression levels are high, the ABI1 protein shows increased stability, compared to when JAZ1 is absent, or ABI3 is overexpressed. Consequently, in the abi3‐6 mutant, due to the higher stability of ABI1, reduced phosphorylation of plasma membrane H+‐ATPase (AHA2) occurs. HPTS staining further indicated that abi3‐6 root cell apoplasts show reduced protonation, compared to wild‐type and ABI3 overexpressing seedlings. Such impeded proton extrusion negatively affects cell length in the primary root elongation zone. ABI3 therefore controls cell elongation in the primary root by affecting the ABI1‐dependent protonation of root cell apoplasts. In summary, ABI3 controls the expression of JAZ1 and in turn modulates the function of ABI1 to regulate cell length in the elongation zone during primary root growth. [ABSTRACT FROM AUTHOR]

The transition metal‐catalyzed asymmetric hydro‐functionalization of 1,3‐dienes has been well explored, but most reactions focus on electron‐neutral substrates in an intermolecular manner. Here we first demonstrate that readily available 2,4‐dienyl hydrazones and oximes can be efficiently utilized in the hydro‐cyclization reaction under co‐catalysis of a Brønsted acid and a chiral palladium complex, furnishing multifunctional dihydropyrazones and dihydroisoxazoles, respectively. Diverse substitution patterns for both types of electron‐deficient diene compounds are tolerated, and corresponding heterocycles were generally constructed with moderate to excellent enantioselectivity, which can be elaborated to access products with higher molecular complexity and diversity. Control experiments and density functional theory calculations support that α‐regioselective protonation of dienyl substrates by acid and concurrent π‐Lewis base activation of Pd0 complex is energetically favoured in the formation of active π‐allylpalladium intermediates, and an outer‐sphere allylic amination or etherification mode is adopted to deliver the observed cyclized products enantioselectively. [ABSTRACT FROM AUTHOR]

Fluorescing proteins emitting in the near-infrared region are of high importance in various fields of biomedicine and applied life sciences. Promising candidates are phytochromes that can be engineered to a small size and genetically attached to a target system for in vivo monitoring. Here, we have investigated two of these minimal single-domain phytochromes, miRFP670nano3 and miRFP718nano, aiming at a better understanding of the structural parameters that control the fluorescence properties of the covalently bound biliverdin (BV) chromophore. On the basis of resonance Raman and time-resolved fluorescence spectroscopy, it is shown that in both proteins, BV is deprotonated at one of the inner pyrrole rings (B or C). This protonation pattern, which is unusual for tetrapyrroles in proteins, implies an equilibrium between a B- and C-protonated tautomer. The dynamics of the equilibrium are slow compared to the fluorescence lifetime in miRFP670nano3 but much faster in miRFP718nano, both in the ground and excited states. The different rates of proton exchange are most likely due to the different structural dynamics of the more rigid and more flexible chromophore in miRFP670nano3 and miRFP718nano, respectively. We suggest that these structural properties account for the quite different fluorescent quantum yields of both proteins. [ABSTRACT FROM AUTHOR]

Reprogrammable shape morphing is ubiquitous in living beings and highly crucial for them to move in normal situations, even to survive under dangerous conditions. There is increasing interest in using asymmetric hydrogel structures to understand and mimic living beings’ shape morphing upon an external trigger in a controlled way. However, these asymmetric or heterogeneous configurations cannot be further modified once the polymer hydrogels are prepared. Therefore, it is a great challenge to achieve reprogrammable shape morphing using the existing hydrogels. Inspired by marine amoebae, which transform into several different morphologies according to the various external salt concentrations, a new strategy is developed for salting hydrogels to reconfigure their anisotropy toward reprogrammable shape morphing. Polyampholyte hydrogels with equal stoichiometric COO− and N+(CH3)3 groups were first swollen in HCl/NaCl solution. After being then transferred into water, they first swollen again by water uptake driven by the osmotic pressure, and then were spontaneously deswollen due to increase in internal pH and dialysis of ions leading to deprotonation of COOH to COO− and regeneration of COO−/N+(CH3)3 electrostatic attraction. This work provides a novel strategy to reconfigure anisotropy of hydrogel soft actuators and to open up an avenue for reprogrammable shape morphing. [ABSTRACT FROM AUTHOR]

Replacing the slow protonation process of oxygen evolution reaction (OER) with the fast protonation of alcohol electro‐oxidation can decrease the driving potentials, thus improving overall efficiency of electrochemical devices. However, the formation of effective catalytic sites for alcohol oxidation remains challenging in accelerating protonation to inhibit metal leaching and improve catalyst stability. Herein, asymmetric Ni‐O‐Cr sites are constructed by alloying Cr into the NiO matrix to optimize coordination environments, showing significantly enhanced stability during alcohol electro‐oxidation. The asymmetric Ni‐O‐Cr can maintain constant valence states of Cr and Ni during alcohol oxidation, efficiently suppressing metal dissolution even at high oxidation potentials. In situ electrochemical characterizations combined with theoretical calculations indicate that asymmetric Ni‐O‐Cr can improve adsorption and activation of OH* and alcohol molecules compared to pure NiO, thus increasing anodic kinetics. The theoretical results also indicate that the smaller gap of Ni 3d‐O 2p in asymmetric Ni‐O‐Cr strengthens charge transfer, leading to fast protonation of catalytic sites with enhanced stability. This work gives insights into boosting anodic protonation using asymmetric sites‐enriched solid‐solution electrocatalysts. [ABSTRACT FROM AUTHOR]

The unimolecular reactions of protonated myrcene and linalool were investigated by collision‐induced dissociation and density functional theory calculations. Experiments on a triple quadrupole mass spectrometer showed that protonated myrcene undergoes two major unimolecular reactions losing propene and isobutene, and two minor reactions of ethene and propane loss. In each case, the product ion consists of a substituted five‐member ring. Protonation of myrcene was found to form four distinct protomers, three of which can be significantly populated in the ion source. The observed fragmentation reactions were calculated and found to depend on the starting protomer. Each pathway consisted of several hydrogen‐migration and ring‐forming/opening steps on the way to the observed products. Likewise, protonation of linalool also produces three distinct protomers, with the global minimum being formed by protonation of a central double bond. The major reaction is water loss to form protonated myrcene, but two minor channels were also observed resulting in loss of acetone and isobutene. The calculated minimum energy reaction pathways were found to be consistent with the relative abundances of the ions in the experimental breakdown diagrams. [ABSTRACT FROM AUTHOR]

Treating the amide acetanilide (N‐phenylacetamide, C8H9NO) with aqueous strong acids allowed the structures of five hemi‐protonated salt forms of acetanilide to be elucidated. N‐(1‐Hydroxyethylidene)anilinium chloride–N‐phenylacetamide (1/1), [(C8H9NO)2H][Cl], and the bromide, [(C8H9NO)2H][Br], triiodide, [(C8H9NO)2H][I3], tetrafluoroborate, [(C8H9NO)2H][BF4], and diiodobromide hemi(diiodine), [(C8H9NO)2H][I2Br]·0.5I2, analogues all feature centrosymmetric dimeric units linked by O—H...O hydrogen bonds that extend into one‐dimensional hydrogen‐bonded chains through N—H...X interactions, where X is the halide atom of the anion. Protonation occurs at the amide O atom and results in systematic lengthening of the C=O bond and a corresponding shortening of the C—N bond. The size of these geometric changes is similar to those found for hemi‐protonated paracetamol structures, but less than those in fully protonated paracetamol structures. The bond angles of the amide fragments are also found to change on protonation, but these angular changes are also influenced by conformation, namely, whether the amide group is coplanar with the phenyl ring or twisted out of plane. [ABSTRACT FROM AUTHOR]

Methoxypolyethylene glycol 1900 and α-bromoisobutanoyl bromide were utilized for alcoholysis reaction to obtain a macromolecular initiator. Then, a simple amphiphilic diblockpolymer (mPEG-PDMAEMA) based on the initiator and dimethylaminoethyl methacrylate was synthesized through the atomic transfer radical polymerization (ATRP) method. The structures of the initiator and diblock polymer were accurately characterized using infrared spectrum and proton nuclear magnetic resonance spectroscopy (1H NMR). Cryo-transmission electron microscopy revealed the self-assembly of mPEG-PDMAEMA into vesicle-like structures in water. Upon injection of CO2 into the solution, the tertiary amine structure within PDMAEMA underwent protonation, resulting in the mPEG-PDMAEMA adopting a hydrophilic structure. Consequently, the vesicles dissociated and dispersed, forming a network-like structure in water. The protonation phenomenon was confirmed by 1H NMR, as evidenced by the shifting of alkyl hydrogen atoms near nitrogen atoms toward downfield positions. [ABSTRACT FROM AUTHOR]

Methoxypolyethylene glycol 1900 and α-bromoisobutanoyl bromide were utilized for alcoholysis reaction to obtain a macromolecular initiator. Then, a simple amphiphilic diblockpolymer (mPEG-PDMAEMA) based on the initiator and dimethylaminoethyl methacrylate was synthesized through the atomic transfer radical polymerization (ATRP) method. The structures of the initiator and diblock polymer were accurately characterized using infrared spectrum and proton nuclear magnetic resonance spectroscopy (1H NMR). Cryo-transmission electron microscopy revealed the self-assembly of mPEG-PDMAEMA into vesicle-like structures in water. Upon injection of CO2 into the solution, the tertiary amine structure within PDMAEMA underwent protonation, resulting in the mPEG-PDMAEMA adopting a hydrophilic structure. Consequently, the vesicles dissociated and dispersed, forming a network-like structure in water. The protonation phenomenon was confirmed by 1H NMR, as evidenced by the shifting of alkyl hydrogen atoms near nitrogen atoms toward downfield positions.

Comprehensive Summary: Chiral α‐tertiary aminonitriles are valuable synthetic intermediates. They are also found in various structures of biologically active molecules. Therefore, numerous reports of catalytic asymmetric synthesis of chiral α‐aminonitriles continuously emerged during the past few decades. Great strides have been made for the synthesis of chiral α‐aryl and α‐branched alkyl aminonitriles. However, efficient methods for catalytic asymmetric synthesis of chiral α‐linear alkyl aminonitriles remain limited. We herein report a new synthetic approach to chiral α‐tertiary alkyl aminonitriles via catalytic asymmetric isomerization of cyanoketimines. The synthetic value of this method was illustrated by application to a concise catalytic asymmetric synthesis of vildagliptin. [ABSTRACT FROM AUTHOR]

Z-scheme CdS-COF-Ni-AC heterojunction was successfully synthesized by in-situ growth of CdS nanosheets on the obtained COF-Ni component and then protonation in ascorbic acid aqueous solution. Under the synergistic effect of the interfacial interaction and surface protonation treatment, the photocatalytic performance of CdS-COF-Ni-AC towards H 2 evolution has been significantly enhanced. [Display omitted] • A Z-scheme CdS-COF-Ni-AC heterojunction is successfully constructed. • Protonation treatment is used to improve the reaction kinetics for H 2 production. • A built-in electric field is formed to accelerate charge separation and transfer. • Interfacial interaction and protonation show synergistic effect on H 2 production. The low efficiency of photocatalytic hydrogen production from water is mainly suffer from limited light absorption, charge separation and water delivery to the active centers. Herein, an inorganic–organic Z-scheme heterojunction (CdS-COF-Ni) is constructed by in-situ growth of CdS nanosheets on the porphyrin-based covalent organic framework with nickel ions (COF-Ni) in the porphyrin centers. A built-in electric field is formed at the interface, which accelerates the separation and transfer of photogenerated charges. Moreover, through the surface protonation treatment in ascorbic acid (AC) solution, the hydrophilicity of the obtained composite is obviously increased and facilitates the transport of water molecules to the photocatalytic centers. Under the synergistic effect of the interfacial interaction and surface protonation treatment, the photocatalytic hydrogen production rate is optimized to be 18.23 mmol h−1 g−1 without adding any cocatalysts, which is 21 times that of CdS. After a series of photoelectrochemical measurements, in situ X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations, it is found that the photocatalytic charge transfer pathway conforms to the Z-scheme mechanism, which not only greatly accelerates the separation and transfer of photogenerated charges, but also retains a high reduction capacity for water splitting. This work offers a good strategy for constructing highly efficient organic–inorganic heterojunctions for water splitting. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are promising photocatalysts for H2O2 production from water via oxygen reduction reaction (ORR). The design of COFs for efficient H2O2 production indubitably hinges on an in‐depth understanding of their ORR mechanisms. In this work, taking an imine‐linked COF as an example, we demonstrate that protonation of the functional units such as imine, amine, and triazine, is a highly efficient strategy to upgrade the activity levels for H2O2 synthesis. The protonation not only extends the light absorption of the COF but also provides proton sources that directly participate in H2O2 generation. Notably, the protonation simplifies the reaction pathways of ORR to H2O2, i.e. from an indirect superoxide radical (O2•- ${{O}_{2}^{\bullet -}}$) mediated route to a direct one‐step two‐electron route. Theoretical calculations confirm that the protonation favors H2O2 synthesis due to easy access of protons near the reaction sites that removes the energy barrier for generating *OOH intermediate. These findings not only extend the mechanistic insight into H2O2 photosynthesis but also provide a rational guideline for the design and upgradation of efficient COFs. [ABSTRACT FROM AUTHOR]

Ion exchange is a promising synthetic method for alleviating severe cation mixing in traditional layered oxide materials for lithium-ion batteries, leading to enhanced structural stability. However, the underlying mechanisms of ion exchange are still not fully understood. Such a fundamental study of the ion-exchange mechanism is needed for achieving the controllable synthesis of layered oxides with a stable structure. Herein, we thoroughly unearth the underlying mechanism that triggers the ion exchange of Ni-rich materials in aqueous solutions by examining time-resolved structural evolution combined with theoretical calculations. Our results reveal that the reaction pathway of ion exchange can be divided into two steps: protonation and lithiation. The proton is the key to achieving charge balance in the ion exchange process, as revealed by X-ray adsorption spectroscopy and inductive coupled plasma analysis. In addition, the intermediate product shows high lattice distortion during ion exchange, but it ends up with a most stable product with high lattice energy. Such apparent discrepancies in lattice energy between materials before and after ion exchange emphasize the importance of synthetic design in structural stability. This work provides new insights into the ion-exchange synthesis of Ni-rich oxide materials, which advances the development of cathode materials for high-performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

This study developed three microstructured chitosan nanocapsules with immobilized lipase to explore chitosan-lipase interactions at different pH levels. Chitosan undergoes complete protonation or deprotonation based on pH level. Three distinct pH levels were examined: 5.5, where chitosan is fully protonated; 6.5, where chitosan is partially protonated/deprotonated; and 7.5, where chitosan is fully deprotonated. The nanocapsules exhibited nanoscale dimensions and the microstructures showed porous morphology. Immobilized lipase showed improved temperature stability, compared to free enzyme, especially in lipase supports at pH 5.5 and 7.5 due to electrostatic and hydrophobic interactions. The interactions between chitosan and lipase influenced the microenvironment around the active site, resulting in an optimum pH of 8 for all supports. Immobilized lipase at pH 5.5 and 7.5 displayed the best reusability in the hydrolysis of p-nitrophenyl palmitate under reaction conditions of 37 °C and pH 8. During refrigeration storage, all immobilized lipases maintained total activity for 7 days, but lipase immobilized at pH 6.5 maintained more the activity after 28 days. Therefore, this study has developed promising immobilized lipase, standing out not only for industrial application concerning cost-effectiveness, but also for the innovation in investigating the influence of chitosan-lipase interactions during immobilization. [ABSTRACT FROM AUTHOR]

Hydrogen‐associated electron doping Mottronics within d‐orbital transitional metal oxides (TMOs) opens up a new paradigm to explore exotic physical phenomena that enable promising applications such as artificial intelligence, Mottronic/iontronic devices, energy conversions, bio‐electronic sensing, and smart windows. Although remarkable progress is achieved over the past decade, systematic and in‐depth insights into hydrogen‐associated exotic physical phenomena within TMOs are still lacking. Herein, this review delivers a comprehensive and timely picture of hydrogen‐triggered electronic phase transitions within TMOs, covering the hydrogenation strategies, research progress, underneath mechanisms, multidisciplinary applications, and beyond. Furthermore, of particular interest, the hydrogenation or protonation enables the possibility of exploring the novel electronic phase and exotic physical properties within TMOs via breaking the intrinsic coupling in the charge, spin, lattice, and orbital degrees of freedom. Beyond that, a broader vision is further cast into the cutting‐edge researching fields of the multifunctionality associated with hydrogenated TMOs and the role of hydrogen in filling‐controlled Mottronic transitions by using hydrogenation. As combined with the critical overview of the existing open questions and future prospects, this review is expected to provide useful guidance on the hydrogen‐associated electronic phase transitions within TMOs and further broaden the promising applications. [ABSTRACT FROM AUTHOR]

Understanding the diversity of DNA structure and functions in biology requires tools to study this biomolecule selectively and thoroughly. Fluorescence methods are powerful technique for non-invasive research. Due to the low quantum yield, the intrinsic fluorescence of nucleotides has not been considered for use in the detection and differentiation of nucleic acid bases. Here, we have studied the influence of protonation of nucleotides on their fluorescence properties. We show that protonation of ATP and GTP leads to enhanced intrinsic fluorescence. Fluorescence enhancement at acidic pH has been observed for double-stranded DNA and single-stranded oligonucleotides. The formation of G4 secondary structures apparently protected certain nucleotides from protonation, resulting in less pronounced fluorescence enhancement. Furthermore, acid-induced depurination under protonation was less noticeable in G4 structures than in double-stranded and single-stranded DNA. We show that changes in the intrinsic fluorescence of guanine can be used as a sensitive sensor for changes in the structure of the DNA and for the protonation of specific nucleotides. • Protonation of purine nucleoside triphosphates leads to enhanced intrinsic fluorescence. • The intrinsic fluorescence of protonated purines depends on the DNA structure. • Formation of G4 structures protects certain guanines from protonation. [ABSTRACT FROM AUTHOR]

Electron-rich heteroaromatics, such as furan, thiophene and pyrrole, as well as their benzo-condensed derivatives, are of great interest as components of natural products and as starting substances for various products including high-tech materials. Although their reactions with Brønsted and Lewis acids play important roles, in particular as the primary step of various transformations, they are often disregarded and mechanistically not understood. The present publication gives a first overview about this chemistry focusing on the parent compounds. It comprises reactions with strong Brønsted acids forming adducts that can undergo intramolecular proton and/or substituent transfer reactions, ring openings or ring transformations into other heterocycles, depending on their structure. Interactions with weak Brønsted acids usually initiate oligomerizations/polymerizations. A similar behaviour is observed in reactions of these heteroaromatics with Lewis acids. Special effects are achieved when the Lewis acids are activated through primary protonation. Deuterated Brønsted acids allow straight forward deuteration of electron-rich heteroaromatics. Mercury salts as extremely weak Lewis acids cause direct metalation in a straight forward way replacing ring H-atoms yielding organomercury heterocycles. This review will provide comprehensive information about the chemistry of adducts of such heterocycles with Brønsted and Lewis acids enabling chemists to understand the mechanisms and the potential of this field and to apply the findings in future syntheses. [ABSTRACT FROM AUTHOR]

The salts bis(2‐amino‐3‐methylpyridinium) fumarate dihydrate, 2C6H9N2+·C4H2O22−·2H2O (I), and 2‐amino‐3‐methylpyridinium 5‐chlorosalicylate, C6H9N2+·C7H4ClO3− (II), were synthesized from 2‐amino‐3‐methylpyridine with fumaric acid and 5‐chlorosalicylic acid, respectively. The crystal structures of these salts were characterized by single‐crystal X‐ray diffraction, revealing protonation in I and II by the transfer of a H atom from the acid to the pyridine base. In the crystals of both I and II, N—H...O interactions form an R22(8) ring motif. Hirshfeld surface analysis distinguishes the interactions present in the crystal structures of I and II, and the two‐dimensional (2D) fingerprint plot analysis shows the percentage contribution of each type of interaction in the crystal packing. The volumes of the crystal voids of I (39.65 Å3) and II (118.10 Å3) have been calculated and reveal that the crystal of I is more mechanically stable than II. Frontier molecular orbital (FMO) analysis predicts that the band gap energy of II (2.6577 eV) is lower compared to I (4.0035 eV). The Quantum Theory of Atoms In Molecules (QTAIM) analysis shows that the pyridinium–carboxylate N—H...O interaction present in I is stronger than the other interactions, whereas in II, the hydroxy–carboxylate O—H...O interaction is stronger than the pyridinium–carboxylate N—H...O interaction; the bond dissociation energies also confirm these results. The positive Laplacian [∇2ρ(r) > 0] of these interactions shows that the interactions are of the closed shell type. An in‐silico ADME (Absorption, Distribution, Metabolism and Excretion) study predicts that both salts will exhibit good pharmacokinetic properties and druglikeness. [ABSTRACT FROM AUTHOR]

An composite adsorbent, Diatomite-KH560 was prepared by loading 7- (2, 3-epoxypropoxy)propytrimethoxysilane (KH560) on the surface of cheap and easily obtained diatomite, and its high-efficiency adsorption performance for iodide in aqueous solution was investigated. KH560 Was loaded on diatomite by immersion and hydrolysis, and contact time, temperature, pH, initial concentration and coexisting ions were investigated to evaluate the adsorption performance of Diatomite-KH560 for iodide. The result showed that Diatomite-KH560 with mild preparation conditions has high thermal stability, and the modification amount of KH560 is more than 13.3%. It takes a long time for Diatomite-KH560 to reach adsorption equilibrium for iodide, which may be controlled by several factors such as the diffusion of iodide in aqueous solution and the adsorption reaction rate on the adsorbent surface. The rate-controlling step is trans-formed into chemical adsorption process with the increase of temperature. In weak acid environment, the epoxy group on Diatomite-KH560 is protonated, forming positively charged adsorption sites, which adsorbs iodide through electrostatic attraction. According to the anion composition characteristics of brine, the effect of high concentration of chloride ion and trace amount of bromide ion and sulfate on the adsorption of iodide was investigated. It was found that the adsorption capacity of Diatomite-KH560 on iodide remained at 0.63 mg/g when the initial Cl/I reached 2 500 times. On the basis of the characterization results of EDS and FTIR, combined with the molecular structure of KH560, Diatomite-KH560 may achieve highly selective adsorption of iodide through the protonation of epoxy groups. [ABSTRACT FROM AUTHOR]

This study investigated the degradation and removal efficiency of reactive and direct dyes using various treatment processes, including UV alone, peroxide alone, Fenton, photo-Fenton, and UV-peroxide. The decolorization results showed that UV and peroxide alone had limited performance, achieving only 8.8% to 14.4% decolorization for direct dyes DR28 and DB71. The Fenton and photo-Fenton processes exhibited rapid total organic carbon (TOC) degradation within the initial 30 minutes, reducing reactive dyes RBla5, RB19, and RO16 by 41.3% to 38.8%. However, the reaction stagnated due to the depletion of Fe2+ in the Fenton process. Interestingly, the UV-peroxide treatment demonstrated superior decolorization performance, achieving 72.9% to 99.2% decolorization for DR28 and DB71 at pH 3 and 7. In contrast, TOC removal efficiency fell below expectations for all processes. The iron-based processes, Fenton and photo-Fenton, resulted in low TOC removal values for both direct dyes, possibly caused by the mordanting phenomena between dyes and iron, shown by visible sediment formation Further research is needed to optimize TOC removal efficiency, especially for direct dyes, and to elucidate the mechanisms of protonation and mordant interactions in the dye degradation process. [ABSTRACT FROM AUTHOR]

A Brønsted acid-catalyzed regioselective intramolecular hydroalkoxylation is described. This reaction proceeds via a carbocation intermediate and enables the preparation of 1,1,1'-trisubstituted tetrahydropyran derivatives under mild conditions using catalytic triflic acid (TfOH) and hexafluoroisopropanol (HFIP) as a mediator. [ABSTRACT FROM AUTHOR]

Nanoclay is considered to be one of the best fillers for reinforcement in structural polymer composites because of its low cost, easy availability, and ability to improve mechanical, thermal, corrosion resistance, barrier properties and nonflammability in corresponding nanocomposites. Pristine nanoclay is hydrophilic and therefore needs surface modification to make it compatible for uniform dispersion with polymer matrix. In the present work, montmorillonite nanoclay was protonated for generating more hydroxyl groups to facilitate silane functionalization and is reinforced to prepare epoxy nanocomposites with a varying content of 0.5 to 20 wt%. Studies are also conducted to investigate the effect of silanization of unprotonated nanoclay on epoxy nanocomposites. Interestingly, uniform highly exfoliated reduced‐size nanoclay platelets are obtained for functionalized protonated nanoclay. This behavior is attributed to the increase in the d‐spacing between the interlayers of the nanoclay during protonation and silanization. Tensile performances are found best with 0.5 wt% of silanized clay with an improvement of ~50%, ~84% and ~177% in strength, modulus and absorbed failure energy compared to neat epoxy. Although flexural and fracture performance are found highest with 2 wt% of silanized protonated clay with an improvement of ~57.5% in flexural strength and a remarkable ~241% and ~964% enhancement in fracture toughness and fracture energy compared to neat epoxy. The toughening mechanism investigation endorses the improvement in interfacial adhesion of the protonated silanized nanoclay that enhances the properties of the interfacial region, which significantly enhances the resistance for in‐panne crack propagation in epoxy nanocomposites. Highlights: Synthesized silanized and silanized protonated montmorillonite clay.Protonation facilitated silane moiety attachment onto nanoclay.Maximum improvement of flexural strength by ~57.5% for ESPrC2.KIC and GIC were highest showing ~1.74 MPam1/2 and ~830.28 J/m2 for ESPrC2.Enhanced interfacial adhesion due to SPrC with the epoxy matrix. [ABSTRACT FROM AUTHOR]

Li7La3Zr2O12 garnets are among the most promising materials for solid‐state electrolytes thanks to their high electrochemical stability and ionic conductivity. However, they are unstable in air and easily undergo a Li+/H+ exchange reaction, forming a lithiophobic and poorly Li‐conducting surface layer composed of LiOH and Li2CO3 upon further reaction with CO2. Despite a simple reaction mechanism, protonation of LLZO is a complex phenomenon. The thickness and composition of the secondary phases on the surface depend on many parameters both in the LLZO properties and in the storage atmosphere. Due to this complexity, proposing a universal procedure for removing the secondary phases is not simple. However, understanding the role of different parameters and rational selection of characterization techniques makes it possible to find the optimal conditions for removing the LiOH/Li2CO3 layer and further processing each material. This work compares some of the main approaches for cleaning the LLZO surface and describes their advantages and shortcomings. Additionally, the strengths and limitations of the most common characterization techniques for analyzing the (de)protonation of LLZO (XRD, XPS, Raman, NMR, TGA) are explained to help researchers design their experiments more accurately. [ABSTRACT FROM AUTHOR]

This study investigates the impact of thermal decomposition on the ion mobility spectrum of L-alanine using ion mobility spectrometry (IMS) and computational methods. By employing a post-injection delay system, we examined the evolution of ion peaks corresponding to thermal decomposition products and their interaction with protonated alanine. Experimental results revealed that the observed ion mobility spectra predominantly feature protonated isomers and adduct ions. Computational analysis using Density Functional Theory (DFT) predicted the thermodynamically favored structures and stabilities of these products. Findings indicate that protonation at the nitrogen site in alanine is more stable than at the oxygen site, and observed peaks correspond to protonated isomers and adducts formed with ammonium ions. Further investigations showed that thermal decomposition of alanine generates ammonia, contributing to the formation of new adduct ions. This research provides new insights into the behavior of amino acids under thermal conditions with implications for analytical chemistry and biochemistry.

AbstractAtomistic molecular dynamics simulations of the single chains of cationic polyelectrolytes of atactic poly(vinyl amines) (PVAm) modified by hydrophobic side-groups, poly(N-ethyl-n-vinyl amine) (ethyl-PVAm) and poly(N-benzyl-n-vinyl amine) (benzyl-PVAm), in aqueous solution, were carried out over the entire range of degree-of-ionization, f. These polymers, to our knowledge, were studied here by molecular simulations for the first time. The interplay of electrostatic interactions, excluded volume, hydrophobic effect, hydrogen bonding and counter-ion interaction with hydrophobic-polyions, is analyzed. The conformational transition of the polyelectrolyte chain from a coiled to an extended state was gradual and was observed for 0.3 < f < 0.7. Ethyl-PVAm and benzyl-PVAm exhibited similar values of radius-of-gyration Rg and end-to-end distance R for f > 0.5, in agreement with available experimental data. The more hydrophobic benzyl-PVAm showed a more extended conformation with a preference for trans states in the backbone. The change in chain expansion with respect to f was more for benzyl-PVAm as compared to ethyl-PVAm. The relaxation time of polymer-water H-bonds increased with f and the hydrophobicity of the polymer chain, with faster decay for ethyl-PVAm. The water molecules solvating the hydrophobic PVAm’s showed dynamical restriction due to bulky hydrophobic side-groups resulting in long-lived H-bonds. The number of polymer-water H-bonds showed a transition at a certain charge, which influenced the complex interplay of steric effect, hydrophobic effect and solvation. [ABSTRACT FROM AUTHOR]

We report a light‐irradiation method to control the synchronous nucleation of a donor‐acceptor (D‐A) fluorophore for growing highly uniform single‐crystalline microrods, which is in sharp contrast to the prevailing methods of restricting spontaneous nucleation and additionally adding seeds. The D‐A fluorophore was observed to undergo photoinduced electron transfer to CrCl3, leading to the generation of HCl and the subsequent protonation of the D‐A fluorophore. By intensifying photoirradiation or prolonging its duration, the concentration of protonated D‐A fluorophores can be rapidly increased to a high supersaturation level. This results in the formation of a controlled number of nuclei in a synchronous manner, which in turn kickstart the epitaxial growth of protonated D‐A fluorophores towards uniform single‐crystalline microrods of controlled sizes. The light‐regulated synchronous nucleation and uniform growth of microrods are a unique phenomenon that can only be achieved by specific Lewis acids, making it a novel probing method for sensitively detecting strong Lewis acids such as chromium chloride. [ABSTRACT FROM AUTHOR]

Salts of protonated sulfur dioxide were synthesized by recrystallization of [FS(OX)2][SbF6] (X=H, D) in aprotic solvents at low temperatures. Hemiprotonated sulfur dioxide [(SO2)2H][Sb2F11] was obtained from the solvent SO2 and the monoprotonated sulfur dioxide [OSOD][Sb2F11], using 1,1,1,2‐tetrafluoroethane as solvent. For both compounds, single crystals were obtained and an X‐ray structure analysis was conducted. Furthermore, the salts were characterized by Raman spectroscopy and the results were discussed together with quantum chemical calculations on the M06‐2X/aug‐cc‐pVTZ level of theory. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2), an energy carrier, is among the advanced energy technologies. In the study, a hybrid metal-free catalyst was provided by protonation of chitosan dispersed on montmorillonite (Chit-Mont-H) using calcination and hydrothermal methods. Highly active H 2 release via sodium borohydride (NaBH 4) using Chit-Mont-H in propylene glycol, methanol or propylene glycol/methanol mixture was performed as a first in the literature. H 2 generation rate (HGR) values in methanol and methanol/propylene glycol were 6743 and 23,536 mL min−1g cat −1, respectively. There is a significant increase of approximately 4 times in the HGR values in methanol/propylene glycol compared to methanol. The catalysts by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analyser (EDS), and Transmission electron microscopy (TEM) analyses were characterized. The activation energy (Ea) value was calculated as 27.53 kJ mol−1. Also, the mechanism of H 2 release in a mixture of methanol/propylene glycol by Chit-Mont-H was proposed. [Display omitted] • A hybrid metal-free catalyst was provided by protonation of Chit dispersed on Mont. • H 2 production via NaBH 4 in propylene glycol/methanol using Chit-Mont-H was performed. • HGR values in methanol and methanol/propylene glycol were 6743 and 23,536 mL min−1g cat −1. • The mechanism of H 2 release in methanol/propylene glycol by Chit-Mont-H was proposed. [ABSTRACT FROM AUTHOR]

Photoreduction carbon dioxide (CO2) and water (H2O) into valuable chemicals is a huge potential to mitigate immoderate CO2 emissions and energy crisis. To date, tremendous attention is concentrated on the improvement of independent CO2 reduction or H2O oxidation behaviors. However, the simultaneous control of efficient electron and hole utilization is still a huge challenge due to the complex cascade redox reactions. Here, a proton turnover exists in the whole CO2 photoreduction process is discovered, which is defined as the pivot to concatenate the hole and electron behaviors. As a demonstration of the concept, the efficient activated hydrogen (*H) production centers of copper (Cu) and rapid hydrogenation centers of nickel (Ni) are coupled by an alloying strategy, and the proton turnover behaviors could be directly determined by adjustment of the molar ratios of CuxNiy. Moreover, Cu3Ni1-TiO2 exhibits the highest electron selectivity of 93.7% for methane (CH4) production with a rate of 175.9 µmol g-1 h-1, while Cu1Ni5-TiO2 reaches up to the highest carbon monoxide (CO) electron selectivity and generation rate at 84.4% and 164.6 µmol g-1 h-1, respectively. Consequently, the experimental and theoretical analysis all clarify the predominate proton turnover effect during the overall CO2 photoreduction process, which directly determines the categories and generated efficiency of C-based products by regulating variable reaction pathways. Therefore, the revelation of the proton turnover pivot could broaden the new sights by bidirectional optimization of dynamics during the overall CO2 photoreduction system, which favors the efficient, selective, and stable photocatalytic CO2 reduction with H2O. [ABSTRACT FROM AUTHOR]

The synthesis of hydrogen peroxide through artificial photosynthesis is a green and promising technology with advantages in sustainability, economy and safety. However, superoxide radical (⋅O2−), an important intermediate in photocatalytic oxygen reduction to H2O2 production, has strong oxidizing properties that potentially destabilize the catalyst. Therefore, avoiding the accumulation of ⋅O2− for its rapid conversion to H2O2 is of paramount significance in improving catalyst stability and H2O2 yield. In this work, a strategy was developed to utilize protonated groups for the rapid depletion of converted ⋅O2−, thereby the efficiency of photocatalytic synthesis of H2O2 from CN was successfully enhanced by 47‐fold. The experimental findings demonstrated that polydopamine not only improved carrier separation efficiency, and more importantly, provided the adsorption reduction active site for ⋅O2− for efficient H2O2 production. This work offers a versatile approach for synthesizing efficient and stable photocatalysts. [ABSTRACT FROM AUTHOR]

The oxidative addition of methyl iodide or molecular iodine to the bis(С,N-chelate) deprotonated diaminocarbene platinum(II) complexes [Pt{C(N(H)Ar)(NC(N(H)Ph)N(Ph)}2] (Ar = C6H3-2,6-Me2 (Xyl), C6H2-2,4,6-Me3 (Mes), and C6H4-4-Me (pTol)) affords the corresponding platinum(IV) derivatives in a yield of 89–99%. The addition of CF3CO2H is accompanied by the protonation of the nitrogen atoms of the diaminocarbene fragment to form the cationic complexes [PtI(X)-{C(N(H)Ar)(NC-(N(H)Ph)N(Ph)}2]CF3CO2H (X = Me, I). The structures of the compounds are determined by elemental analysis; high resolution mass spectrometry with electrospray ionization (ESI HRMS); IR spectroscopy; 1H, 13C{1H}, 19F{1H}, and 195Pt{1H} NMR spectroscopy; 2D NMR spectroscopy (1H,1Н COSY, 1H,1Н NOESY, 1H,13C HSQC, 1H,13C HMBC, 1H,15N HSQC, 1H,15N HMBC), and X-ray diffraction (XRD) and thermogravimetric analyses. The synthesized platinum(IV) complexes are thermally stable to 200–260°C and are electroneutral molecules with the octahedral coordination sphere formed by two deprotonated diaminocarbene C,N‑chelate substituents and iodine and methyl or two iodine atoms localized in the apical positions. [ABSTRACT FROM AUTHOR]

A novel approach to enhance the utilization of low-cost and sustainable chitosan for wastewater remediation is presented in this investigation. The study centers around the modification of chitosan beads using a deep eutectic solvent composed of choline chloride and urea at a molar ratio of 1:2, followed by treatment with sulfuric acid using an impregnation accessible methodology. The effectiveness of the modified chitosan beads as an adsorbent was evaluated by studying the removal of the azo dye Reactive Black 5 (RB5) from aqueous solutions. Remarkably, the modified chitosan beads demonstrated a substantial increase in adsorption efficiency, achieving excellent removal of RB5 within the concentration range of 25–250 mg/L, ultimately leading to complete elimination. Several key parameters influencing the adsorption process were investigated, including initial RB5 concentration, adsorbent dosage, contact time, temperature, and pH. Quantitative analysis revealed that the pseudo-second-order kinetic model provided the best fit for the experimental data at lower dye concentrations, while the intraparticle diffusion model showed superior performance at higher RB5 concentration ranges (150–250 mg/L). The experimental data were successfully explained by the Langmuir isotherm model, and the maximum adsorption capacities were found to be 116.78 mg/g at 298 K and 379.90 mg/g at 318 K. Desorption studies demonstrated that approximately 41.7% of the dye could be successfully desorbed in a single cycle. Moreover, the regenerated adsorbent exhibited highly efficient RB5 removal (80.0–87.6%) for at least five consecutive uses. The outstanding adsorption properties of the modified chitosan beads can be attributed to the increased porosity, surface area, and swelling behavior resulting from the acidic treatment in combination with the DES modification. These findings establish the modified chitosan beads as a stable, versatile, and reusable eco-friendly adsorbent with high potential for industrial implementation. [ABSTRACT FROM AUTHOR]

The synthesis of new coordination compounds based on d-metal salts with protonated amides and thioamides, along with the study of their structure, physicochemical properties, formation patterns, and identification, poses a challenging task in modern chemistry. This article examines the quantum chemical and IR spectroscopic characteristics of compounds of amides and thioamides with hydrochloric and hexafluorosilicic acids and copper (II) salts. Metal ions form a coordination bond with the oxygen of the unprotonated urea molecule, and in its absence, with the nitrogen atom of the amino group, as confirmed by quantum chemical calculations. Using the quantum chemical method with the PM3 program, interatomic distances, bond angles, charges, and coordinates of the atoms of the resulting coordination compound were calculated. Energetically and geometrically more favorable for copper (II) complexes is the formation of a distorted octahedral structure, the ligands of which are urea, protonated urea and acid anions. Based on the IR spectra of amido complexes, the protonation of amides at the oxygen (sulfur) atom of the carbonyl group of the amide (thioamide) has been demonstrated. In addition, in thioamide compounds, S-protonation is favored by a shift to the high-frequency region of the absorption band of stretching vibrations of C-N bonds. Copper (II) coordination compounds contain both urea and protonated urea molecules in the inner sphere, the former being connected to the complexing agent through the oxygen atom of the carbonyl group, and the latter through the nitrogen atom of the amide group. The experimental data obtained and the established patterns of acid-base interaction of the components provide the theoretical basis for the chemistry of amido complexes, serving as reference material in the field of coordination compound chemistry. [ABSTRACT FROM AUTHOR]

1-[4-(4-Methoxyphenyl)azo]naphthol was synthesized using diazotization and azo coupling reactions. The compound was used as a nucleophile to prepare 3- and 4-[(4-methoxyphenylazo)-4-naphthoxy]phthalonitriles. The corresponding metal complexes of phthalocyanines were synthesized by the template condensation of the resulting substituted phthalonitriles with zinc and magnesium acetates. The influence of the substituent position on the protonation processes and spectroscopic characteristics of metal phthalocyanines was determined. The luminescence properties of the synthesized metal complexes and photosensitization of singlet oxygen were studied. [ABSTRACT FROM AUTHOR]

The oxidative addition of methyl iodide or molecular iodine to the bis(С,N-chelate) deprotonated diaminocarbene platinum(II) complexes [Pt{C(N(H)Ar)(NC(N(H)Ph)N(Ph)}2] (Ar = C6H3-2,6-Me2 (Xyl), C6H2-2,4,6-Me3 (Mes), and C6H4-4-Me (pTol)) affords the corresponding platinum(IV) derivatives in a yield of 89–99%. The addition of CF3CO2H is accompanied by the protonation of the nitrogen atoms of the diaminocarbene fragment to form the cationic complexes [PtI(X)-{C(N(H)Ar)(NC-(N(H)Ph)N(Ph)}2]CF3CO2H (X = Me, I). The structures of the compounds are determined by elemental analysis; high resolution mass spectrometry with electrospray ionization (ESI HRMS); IR spectroscopy; 1H, 13C{1H}, 19F{1H}, and 195Pt{1H} NMR spectroscopy; 2D NMR spectroscopy (1H,1Н COSY, 1H,1Н NOESY, 1H,13C HSQC, 1H,13C HMBC, 1H,15N HSQC, 1H,15N HMBC), and X-ray diffraction (XRD) and thermogravimetric analyses. The synthesized platinum(IV) complexes are thermally stable to 200–260°C and are electroneutral molecules with the octahedral coordination sphere formed by two deprotonated diaminocarbene C,N‑chelate substituents and iodine and methyl or two iodine atoms localized in the apical positions. [ABSTRACT FROM AUTHOR]

As a novel metal-free photocatalyst, g-C 3 N 5 exhibits the narrower bandgap energy and wider visible light response range, which is beneficial for hydrogen evolution reaction compared to g-C 3 N 4. However, the intrinsic features including the lower the separation rate of photogenerated carriers inhibit the further application for photocatalysis water splitting. Herein, the novel protonated-g-C 3 N 5 was fabricated via the reaction between pristine g-C 3 N 5 and nitric acid and further explore the optimal protonation time. The experimental results demonstrate that after the treatment of nitric acid, the specific area surface of g-C 3 N 5 was significantly increased due to the etching effect of acids, which is contributed to provide more reactive sites for enhanced the photocatalytic reaction rate. The superior photocatalytic hydrogen evolution efficiency belonging to the protonated g-C 3 N 5 was exhibited 3.68 times than that of pristine g-C 3 N 5 under the visible light irradiation due to the introduction of protons. The increased photocatalytic activity was attributed to the promoted reduction potential and carrier separation efficiency. Based on five consecutive cycling tests, the prepared samples display the excellent recyclability and stability and the features of the obtained samples were maintained after the cycling experiments. This work provided a facile and low-cost functionalized modification approach for graphitic carbon nitride to achieve higher hydrogen evolution driven by visible light. • The g-C 3 N 5 protonated via nitric acid was fabricated by impregnation methods. • The optimal protonated conditions (6 h) were determined. • The photocatalytic hydrogen production of protonated g-C 3 N 5 (6-HCN) was 3.68 times higher than that of the pristine g-C 3 N 5. • The prepared samples exhibited the superior recyclability and stability (5 cycles for 45 h). • The protonation process of g-C 3 N 5 and the mechanism of hydrogen evolution were hypothesized. [Display omitted] [ABSTRACT FROM AUTHOR]

An enantioselective addition reaction for the construction of 1,3‐nonadjacent stereogenic centers is developed by means of a chiral strong Brønsted base catalyst. The chiral sodium ureate catalyst efficiently promoted the reaction of α‐thioacetamides as less acidic pronucleophiles with vinyl sulfones having a variety of α‐substituents including aryl, alkyl and halo groups, and α‐phenylacrylates, accomplishing the construction of various 1,3‐nonadjacent stereogenic centers in highly diastereo‐ and enantioselective manners. This is a rare example of the construction of 1,3‐nonadjacent stereogenic centers with less acidic pronucleophiles. In addition, the application of Michael acceptors having various types of α‐substituents in a single catalyst system is achieved for the first time, demonstrating the utility of the present catalyst system for the construction of 1,3‐nonadjacent stereogenic centers. [ABSTRACT FROM AUTHOR]

The intricate nature of the surface structure of carbon dots (CDs) hinders a comprehensive understanding of their emission behavior. In this study, we employ two types of CDs created through acid‐alkali treatments, one with surface protonation and the other with surface deprotonation, with the objective of investigating the impact of these surface modifications on carrier behavior using ultrafast spectroscopy techniques. TEM, XRD, FTIR and Raman spectra demonstrate the CDs' structure, featuring graphitic core and abundant surface functional groups. XPS confirms the successful surface modifications of CDs via protonation and deprotonation. Ultrafast transient absorption (TA) spectroscopy reveals that deprotonation modification may decelerate the relaxation process, thereby increasing the visible PL quantum yields (PLQY). Conversely, protonation may accelerate the relaxation process due to the induced low‐energy absorption band, resulting in self‐absorption and reduced PLQY. Furthermore, TA analysis of CDs in mixed solvents with different proportions of ethanol shows the beneficial effect of ethanol in decelerating the relaxation process, leading to an increased PLQY of 33.7 % for deprotonated CDs and 22.1 % for protonated CDs. This study illuminates the intricate relationship between surface deprotonation/protonation modifications and carrier behavior in CDs, offering a potential avenue for the design of high‐brightness CDs for diverse applications. [ABSTRACT FROM AUTHOR]

Proton-coupled oligopeptide transporters (POTs) are of great pharmaceutical interest owing to their promiscuous substrate binding site that has been linked to improved oral bioavailability of several classes of drugs. Members of the POT family are conserved across all phylogenetic kingdoms and function by coupling peptide uptake to the proton electrochemical gradient. Cryo-EM structures and alphafold models have recently provided new insights into different conformational states of two mammalian POTs, SLC15A1, and SLC15A2. Nevertheless, these studies leave open important questions regarding the mechanism of proton and substrate coupling, while simultaneously providing a unique opportunity to investigate these processes using molecular dynamics (MD) simulations. Here, we employ extensive unbiased and enhanced-sampling MD to map out the full SLC15A2 conformational cycle and its thermodynamic driving forces. By computing conformational free energy landscapes in different protonation states and in the absence or presence of peptide substrate, we identify a likely sequence of intermediate protonation steps that drive inward-directed alternating access. These simulations identify key differences in the extracellular gate between mammalian and bacterial POTs, which we validate experimentally in cell-based transport assays. Our results from constant-PH MD and absolute binding free energy (ABFE) calculations also establish a mechanistic link between proton binding and peptide recognition, revealing key details underpining secondary active transport in POTs. This study provides a vital step forward in understanding proton-coupled peptide and drug transport in mammals and pave the way to integrate knowledge of solute carrier structural biology with enhanced drug design to target tissue and organ bioavailability.

Abstract Li7La3Zr2O12 garnets are among the most promising materials for solid‐state electrolytes thanks to their high electrochemical stability and ionic conductivity. However, they are unstable in air and easily undergo a Li+/H+ exchange reaction, forming a lithiophobic and poorly Li‐conducting surface layer composed of LiOH and Li2CO3 upon further reaction with CO2. Despite a simple reaction mechanism, protonation of LLZO is a complex phenomenon. The thickness and composition of the secondary phases on the surface depend on many parameters both in the LLZO properties and in the storage atmosphere. Due to this complexity, proposing a universal procedure for removing the secondary phases is not simple. However, understanding the role of different parameters and rational selection of characterization techniques makes it possible to find the optimal conditions for removing the LiOH/Li2CO3 layer and further processing each material. This work compares some of the main approaches for cleaning the LLZO surface and describes their advantages and shortcomings. Additionally, the strengths and limitations of the most common characterization techniques for analyzing the (de)protonation of LLZO (XRD, XPS, Raman, NMR, TGA) are explained to help researchers design their experiments more accurately.

Fluorescing proteins emitting in the near-infrared region are of high importance in various fields of biomedicine and applied life sciences. Promising candidates are phytochromes that can be engineered to a small size and genetically attached to a target system for in vivo monitoring. Here, we have investigated two of these minimal single-domain phytochromes, miRFP670nano3 and miRFP718nano, aiming at a better understanding of the structural parameters that control the fluorescence properties of the covalently bound biliverdin (BV) chromophore. On the basis of resonance Raman and time-resolved fluorescence spectroscopy, it is shown that in both proteins, BV is deprotonated at one of the inner pyrrole rings (B or C). This protonation pattern, which is unusual for tetrapyrroles in proteins, implies an equilibrium between a B- and C-protonated tautomer. The dynamics of the equilibrium are slow compared to the fluorescence lifetime in miRFP670nano3 but much faster in miRFP718nano, both in the ground and excited states. The different rates of proton exchange are most likely due to the different structural dynamics of the more rigid and more flexible chromophore in miRFP670nano3 and miRFP718nano, respectively. We suggest that these structural properties account for the quite different fluorescent quantum yields of both proteins.

Diethylenetriaminepentaacetic acid (DTPA) is a chelating agent whose complex with the Gd3+ ion is used in medical imaging. DTPA is also used in lanthanide‐actinide separation processes. As protonation of the DTPA ligand can facilitate dissociation of the Gd3+ ion from the Gd‐DTPA complex, this work investigates the coordination structures of the aqueous Gd3+ ion and its environment when chelated by DTPA in eight different DTPA protonation states. Both classical and ab initio molecular dynamics (MD) simulations are conducted to model the solvated complexes. Extended X‐ray absorption fine structure (EXAFS) measurements of the Gd3+aqua ion, and the Gd‐DTPA complex at pH 1 and 11, are compared to EXAFS spectra predicted from the MD simulations to verify the accuracy of the MD structures. The findings of this work provide atomic‐level details into the fluctuating Gd‐DTPA complex environment as the DTPA ligand gradually detaches from the Gd3+ ion with increased protonation. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped cavities are pervasive in graphenic materials, and represent key sites for catalytic and electrochemical activity. However, their structures are generally heterogeneous. In this study, we present the synthesis of a well‐defined molecular cutout of graphene featuring N‐doped cavity. The graphitization of a macrocyclic pyridinic precursor was achieved through photochemical cyclodehydrochlorination. In comparison to its counterpart with pyridinic nitrogen at the edges, the pyridinic nitrogen atoms in this nanographene cavity exhibit significantly reduced basicity and selective binding to Ag+ ion. Analysis of the protonation and coordination equilibria revealed that the tri‐N‐doped cavity binds three protons, but only one Ag+ ion. These distinct protonation and coordination behaviors clearly illustrate the space confinement effect imparted by the cavities. [ABSTRACT FROM AUTHOR]

Decaniobate is a polyoxoniobate considered in photocatalytic studies lacking more detailed electronic transition data. Moreover, its stability in aqueous solution depends on the pH and little is known regarding the protonation of this polyanion. Hence, this electronic structure study based on Density Functional Theory calculations shows that initial protonations occur at specific external oxygen sites situated above and below the equatorial plane of the polyanion [Oe(A)]. Moreover, these Oe(A) protonations cause small perturbations to the inner core structural skeleton constituted by bonds between niobium and internal oxygen atoms via a trans effect. The ultraviolet/visible spectra are slightly affected by these protonations as well, exhibiting a general trend for formation of four main bands in the range from 150 to 250 nm with similar positions and relative intensity profiles. The nature of the lowest energy electronic transitions (231 to 249 nm) indicates that these are charge transfer bands mainly from bridging oxygen to niobium atoms, with an amount of electronic charge received by metal atoms nearly unaltered by the protonations (from 0.32 to 0.38 e). [ABSTRACT FROM AUTHOR]

In chordates, energy buffering is achieved in part through phosphocreatine, which requires cellular uptake of creatine by the membrane‐embedded creatine transporter (CRT1/SLC6A8). Mutations in human slc6a8 lead to creatine transporter deficiency syndrome, for which there is only limited treatment. Here, we used a combined homology modeling, molecular dynamics, and experimental approach to generate a structural model of CRT1. Our observations support the following conclusions: contrary to previous proposals, C144, a key residue in the substrate binding site, is not present in a charged state. Similarly, the side chain D458 must be present in a protonated form to maintain the structural integrity of CRT1. Finally, we identified that the interaction chain Y148‐creatine‐Na+ is essential to the process of occlusion, which occurs via a "hold‐and‐pull" mechanism. The model should be useful to study the impact of disease‐associated point mutations on the folding of CRT1 and identify approaches which correct folding‐deficient mutants. [ABSTRACT FROM AUTHOR]

Layered perovskite-like niobate CsBa2Nb3O10 has been synthesized in a pure single-phase state for the first time using both nitrates and carbonates of cesium and barium. Unlike its Ca-, Sr- and Pb-containing analogs, the niobate obtained was shown not to undergo substitution of interlayer alkali cations with protons (protonation) upon acid treatments under various conditions. A potential reason for its chemical inactivity may consist in partial disordering of cesium and barium cations between the interlayer space and perovskite slab, hindering the interlayer ion exchange. Optical bandgap energy of CsBa2Nb3O10, being equal to 2.8 eV, potentially allows using visible light (λ < 443 nm) for driving photocatalytic reactions. However, the photocatalytic potential of this niobate towards hydrogen production remains untapped since the activity of the interlayer space in protonation and hydration reactions, as shown earlier, is a fundamentally important factor determining the photocatalytic performance of ion-exchangeable layered perovskite-like oxides. [ABSTRACT FROM AUTHOR]

The large‐scale deployment of CO2 electroreduction is hampered by deficient carbon utilization in neutral and alkaline electrolytes due to CO2 loss into (bi)carbonates. Switching to acidic media mitigates carbonation, but suffers from low product selectivity because of hydrogen evolution. Here we report a crown ether decoration strategy on a Cu catalyst to enhance carbon utilization and selectivity of CO2 methanation under acidic conditions. Macrocyclic 18‐Crown‐6 is found to enrich potassium cations near the Cu electrode surface, simultaneously enhancing the interfacial electric field to stabilize the *CO intermediate and accelerate water dissociation to boost *CO protonation. Remarkably, the mixture of 18‐Crown‐6 and Cu nanoparticles affords a CH4 Faradaic efficiency of 51.2 % and a single pass carbon efficiency of 43.0 % toward CO2 electroreduction in electrolyte with pH=2. This study provides a facile strategy to promote CH4 selectivity and carbon utilization by modifying Cu catalysts with supramolecules. [ABSTRACT FROM AUTHOR]

Although a few metal‐free octahedral compounds based on nitrogen‐containing ligands are known, the realization of mixed ligand compounds remains difficult. To obtain an improved understanding of this class of compounds, two new octahedral compounds, [(tmphenH)(phen)]PF6, and [(tmphenH)(tmphen)]PF6 (where tmphen=3,4,7,8‐tetramethyl‐1,10‐phenanthroline and phen=1,10‐phenanthroline), were synthesized. The relationship between the emission properties, as evaluated using experimental measurements and theoretical calculations, and structures of the protonated compounds was studied. In addition, differences between the atomic charge distributions and geometries in the ground and singlet excited states were investigated using density functional theory calculations. Both [(tmphenH)(phen)]PF6 and [(tmphenH)(tmphen)]PF6 formed hydrogen‐bonded octahedrons in acetonitrile solution, even in the excited state. However, the hydrogen bonding in [(tmphenH)(phen)]PF6 was weak and thermal vibrations decreased the emission intensity. In contrast, the additional methyl substituents in [(tmphenH)(tmphen)]PF6 suppressed thermal vibrations, resulting in a higher emission intensity. [ABSTRACT FROM AUTHOR]