Hydrogen-bonded Molecules Research Articles

Characterization and quantitative analysis of unfrozen water at ultra-low temperatures: Insights from NMR and MD study

Unfrozen water, integral to numerous processes such as heat transfer, frost heave, and hydro-thermo-mechanical simulations, has been traditionally studied at 0 ∼ −30 °C, but remains under-investigated at ultra-low temperatures. Understanding this component at ultra-low temperatures and its categorization requires more explorative, quantitative research, particularly considering the ubiquity of frozen soils. The nuclear magnetic resonance (NMR) and molecular dynamics (MD) methods were employed to characterize and quantify unfrozen water during 0 ∼ −80 °C. Our results indicated that bulk and capillary water could completely freeze at −3°C and −5°C, respectively, but only bound water exists below −10 °C. The evolution of unfrozen water with temperature in MD agreed with our NMR results, where the existence of unfrozen water molecules was due to the breakage of hydrogen bonds in ice molecules and the surface effect of clay. This mechanism elucidated the water–ice-clay atomic system’s role in quantifying experimentally measured unfrozen water content. These findings have important implications for frozen soil engineering, polar region development, artificial freezing technology, and lunar soil exploration.

Theoretical study of excited hydrogen bond dynamics of Julolidine-Fluorene compounds

Juronidine have attracted extensive investigations in the field of chromogenic and chemiluminescent materials. In this thesis, DFT and TDDFT methods are used to study the excited state hydrogen bond dynamics and excited state proton transfer mechanism of JDF, including the analysis of its geometric structure, infrared vibration spectrum, absorption and emission spectra, frontier molecular orbitals, and potential energy curve. Results show that the intramolecular hydrogen bond in the JDF molecule weakens after photoexcitation, leading to the relatively high barrier (6.7 kcal/mol) during proton transfer process in the S1 state.

Molecular dynamics simulation of extraction of Curcuma longa L. extract using subcritical water

Humans have utilized plants for various purposes, including sustenance and medical treatment for millennia. Researchers have extensively investigated medicinal plants’ potential in drug development, spurred by their rich array of chemical compounds. Curcumin, a valuable bioactive compound, is extracted from Turmeric, known by the scientific name Curcuma Longa L. Notably, curcumin boasts potent antioxidant and anti-inflammatory properties, making it a promising candidate for treating cancer and other microbial diseases. Therefore, the simulation study of the extraction of this important medicinal compound by water, which is a green solvent, was carried out. This study employed molecular dynamics simulation for the first time to explore the extraction of Curcuma Longa L. extract using subcritical water. The simulations were carried out at constant pressure and different temperatures, using the Compass force field in the Lammps simulation package. The findings revealed an increase in the amount of Curcuma longa extract with rising temperature, indicating a weakening of hydrogen bonds in water molecules. Water lost its polar state with increasing temperature and became a suitable non-polar solvent for extracting non-polar compounds. The average absolute relative deviation (AARD) for calculated and simulated density data was 6.45%.

Quantitative Analysis of Amorphous Form in Indomethacin by Near Infrared Spectroscopy Combined with Partial Least Squares Regression Analysis.

Indomethacin (INDO) is a synthetic non-steroidal antipyretic, analgesic, and anti-inflammatory drug that commonly exists in both amorphous and crystalline states. Its amorphous state (A-INDO) is utilized by pharmaceutical companies as an active pharmaceutical ingredient (API) in the production of INDO drugs due to its higher apparent solubility and bioavailability. The crystal state also encompasses various crystal forms such as the α-crystal form (α-INDO) and γ-crystal form (γ-INDO), with the highly crystalline and insoluble γ-INDO being commercially available. A-INDO, existing in a thermodynamically high-energy state, is susceptible to several factors during the preparation, storage, and transportation of API leading to its conversion into γ-INDO, thus impacting the bioavailability and efficacy of INDO drugs. Therefore, quantitative analysis of the A-INDO/γ-INDO content in INDO API becomes essential for controlling the production quality of INDO. The primary objective of this study is to investigate the feasibility of NIR for the quantitative analysis of A-INDO in INDO API, and to further elucidate its quantitative analysis mechanism. The NIR spectral data were collected for A-INDO and γ-INDO binary mixture samples with different resolutions, and these spectra were then selected and reconstructed using the interval partial least square (iPLS) method. Different pretreatment methods were employed to enhance the reconstructed spectra by highlighting relevant eigen information while eliminating invalid information caused by environmental factors or physical characteristics of samples. The most suitable PLSR model for quantitative analysis of A-INDO within the range of 0.0000-100.0000% w/w% was established, screened, and validated. From various perspectives, including distribution of spectral effective information, impact of resolution on PLSR model performance, variance contribution/cumulative variance contribution of PLSR model principal components (PCs), PCI loadings, relationship between spectral scores, and A-INDO content, feasibility assessment was conducted for the quantitative analysis of A-INDO in INDO using NIR spectroscopy. Additionally, a detailed investigation on the quantitative analysis mechanism of the optimal PLSR model was undertaken including the correlation between the characteristic peaks of spectra and information regarding hydrogen groups or hydrogen bonds in A-INDO or γ-INDO molecules. This study aims to provide theoretical support for the quantitative analysis of A-INDO in INDO API as well as serve as a reliable reference method for API quantification and quality control in similar drugs.

Conformational Geometry Matters: The Case of the Low-Melting-Point Systems of Tetrabutylammonium Triflate with Fumaric or Maleic Acid.

For this article, the interaction of tetrabutylammonium trifluoromethanesulfonate (TBATFO) with either fumaric (FUM) or maleic (MAL) acid has been investigated. These acids are isomers and can be considered the trans and cis configurations of the same molecular geometry. When TBATFO is mixed with FUM, an eutectic point is obtained for a relative composition of 90-10 (molar ratio), with a melting point of ≈90 °C. If maleic acid is mixed with TBATFO, one obtains an inhomogeneous phase with the retention of a solid portion immersed in a liquid phase, even above 90 °C. DFT calculations helped to model the interaction between the components. It is suggested herein that TBATFO interacts more strongly with FUM than with MAL, due to possible interactions in two different sites for hydrogen bonding (HB) in FUM. In MAL, one of the HB sites is instead retained in the intramolecular interactions; therefore, fewer sites are available for intermolecular interactions. Infrared spectroscopy measurements have confirmed this scenario, in which the hydrogen bonds of the acid molecules are replaced by HB between the acid and the ionic couple: for both kinds of mixtures, the vibration region of the OH bonds is strongly affected by mixing. However, in the case of FUM, the vibrations of the SO3 group of the TFO anion are displaced, while they remain in practically the same frequency position in the case of MAL.

Symmetry Donor-Acceptor Molecule Regulating Hydrogen-Bonding Network for Improved Metal Zinc Anode.

The issues of zinc dendrites and side reactions caused by active water molecules have seriously affected the development of aqueous zinc batteries (AZBs). Herein, a symmetry hydrogen-bond donor-acceptor molecule additive named 1,3-bis(hydroxymethyl)urea (BHMU) can preferentially adsorb on the anode surface and lock up water molecules through hydrogen bonding, thus isolating water molecules and reducing side reactions caused by active water molecules. With these advantages, the mixed electrolyte containing BHMU additive impels a reversible Zn anode with a high Coulombic efficiency (99.7% over 1000 cycles at 1 mA cm-2), while it also enables a stable symmetric cell operated at 1 mA cm-2 (1 mAh cm-2, 6.89% DODZn) for 2250 h and 10 mA cm-2 (10 mAh cm-2, 68.9% DODZn) for 350 h. More importantly, the Zn||PTO full battery also delivered superior cycling stability and higher capacity after 3000 consecutive 3000 cycles of circulation at 5 A g-1. This study has great significance for the use of symmetry donor-acceptor molecules to modulate the solvation structure and the interface stability of the Zn anode in aqueous electrolytes.

Identification of Alzheimer’s disease and vascular dementia based on a Deep Forest and near-infrared spectroscopy analysis method

Alzheimer’s disease (AD) and vascular dementia (VaD) typically do not exhibit distinct differences in clinical manifestations and auxiliary examination results, which leads to a high misdiagnosis rate. However, significant differences in treatment approaches and prognosis between these two diseases underscore the critical need for an accurate diagnosis of AD and VaD. In this study, serum samples from 33 patients with AD patients, 37 patients with VaD, and 130 healthy individuals were collected, employing near-infrared aquaphotomics technology in combination with deep learning for differential diagnoses. Through an analysis of water absorption patterns among different diseases via aquaphotomics, the efficacies of traditional machine learning methods (Support Vector Machine and Decision Trees) and deep learning approaches (Deep Forest) in modeling were compared. Ultimately, by leveraging feature extraction techniques in conjunction with deep learning, a differential diagnostic model for AD and VaD was successfully developed. The results revealed that aquaphotomics could identify a certain correlation between the number of hydrogen bonds in water molecules and the development of AD and VaD; the deep learning model was found to be superior to traditional machine learning models, achieving an accuracy of 98.67 %, sensitivity of 97.33 %, and specificity of 100.00 %. The bands identified using the Competitive Adaptive Reweighting Algorithm method, primarily located at approximately 1300–1500 nm, showed a significant correlation with water molecules containing four hydrogen bonds. These results highlighted the potential role of the water molecule hydrogen-bond network in disease development and were consistent with the aquaphotomics analysis results. Therefore, the differential diagnostic model developed by integrating near-infrared spectroscopy and deep learning was proven to be effective and feasible, providing accurate and rapid diagnostic methods for AD and VaD diagnoses.

Hydrogen bond-derived symmetry transformation in hydroxyborates: Converting the nonlinearity from null to active

Non-centrosymmetric structure is the prerequisite to symmetry-dependent properties for functional materials. The inherent tendency of crystallization toward centrosymmetric arrangements has posed a great challenge in nonlinear optical crystals that requires non-centrosymmetric structure. Here we discovered two new hydroxyborates A[C(NH2)3][B4O5(OH)4]·nH2O (A = K, Rb; n = 3, 1.5), which have high similarity in cationic and anionic frameworks but clearly differ in terms of symmetry, such as non-centrosymmetric versus centrosymmetric. Variations in the hydrogen bonds of water molecules in the lattice are confirmed to be the origin of the symmetry breaking and transformation. The effectiveness of hydrogen bond-derived molecular engineering in producing non-centrosymmetric structure and opening up new avenues in the nonlinear optical crystal sector is demonstrated in this work.

New approach: Solvent effects of benzaldehyde in aliphatic alcohol solvents with FT-IR spectroscopy and augmented vertex-adjacency matrices

In this study of benzaldehyde (BNZ) in 7 aliphatic alcohol solvents, were undertaken to investigate the solvent/solute interaction with Fouirer Transform Infrared Spectroscopy (FT-IR), BNZ produced carbonyl group stretching vibration frequencies (ν(C=O)1 and ν(C=O)2). In the present paper, ν(C=O)1 and ν(C=O)2 of BNZ are observed and correlated with the solvent acceptor number (AN), dipolarity/polarizability (π*), hydrogen-bond donor acidity (α), hydrogen-bond acceptor basicity (β), solvent polarity parameter [ET(30)], KBM parameter ƒ(ε), boiling point (bp) and the linear solvation energy relationship (LSER) using single and multiple regression analysis. All calculations were performed for ν(C=O)1 and ν(C=O)2 and compared. ν(C=O)1 was believed to correspond to a single hydrogen bonded BNZ-alcohol complex, while ν(C=O)2 was believed to correspond to a multiple hydrogen bonded BNZ-alcohol complex and multiple hydrogen-bonded alcohol molecules. It was seen that LSER equation as multiple regression analysis was better than single regression analysis in explaining solute-solvent interactions due to the higher correlation coefficients obtained. The correlations of a set of the mathematical characteristics of the augmented vertex-adjacency matrices (AV-AM) obtained by the chemical structure of BNZ with solvent parameters and ν(C=O) were investigated. It was determined that the correlation factors (R2 > 0.999) of the multiparameter regression models obtained using the matrix results were higher than the correlation factors (R2 > 0.99) of the LSER equations including solvent parameters.

Theoretical Study on the Effect of Cyano- and Dimethylamine-Group on ESIPT Behavior and Luminescent Properties of Novel Flavone-Based Fluorophore.

Recently, a new fluorescent senor based on 3-hydroxy-2-(naphthalen-2-yl)-4H-chromen-4-one (HFN) for selective detection of H2Sn was obtained in the experiment (Spectrochim. Acta Part A 271(2022)120962). Based on HFN, three new compounds (HFN1, HFN2 and HFN3) are designed to explore the influences of dimethylamine (-N(CH3)2) and cyano (-CN) groups on the excited-state intramolecular proton transfer (ESIPT) process and luminescent features of HFN. After analyzing the mainly geometrical parameters, electron densities and infrared spectra, we discovered that the intramolecular hydrogen bonds (IHBs) in the target molecules become stronger upon photo-excitation. Introducing -CN or/and -N(CH3)2 groups into HFN indeed influences its ESIPT behavior and luminescent properties. The -N(CH3)2 group enhances IHB, reduces ESIPT barrier and caused absorption/ fluorescence (at T form) peak blue-shift, while the -CN group shows a counterproductive effect. The coincidence of -N(CH3)2 and -CN made the absorption/fluorescent wavelength of HFN red-shift more than single -N(CH3)2 or -CN group does.

ОБЛАДНАННЯ ВХІДНОЇ МАГНІТНО-КАВІТАЦІЙНОЇ ПІДГОТОВКИ ВОДИ ДЛЯ ТЕПЛОМЕРЕЖ

If high-quality water treatment for boilers is not organized, the impurities present in untreated water lead to a number of problems: large colloidal and mechanical impurities in the form of scale, rust, clay or sand quickly clog the pipes, significantly reducing their internal diameter. This causes the failure of shut-off valves and pumping equipment: hardness salts and other poorly soluble salts (carbonates, magnesium and calcium sulfates, silicates, various compounds of copper and manganese) settle, creating a crust on the metal walls of the equipment, which reduces its heat output. This contributes to a reduction in boiler power, increases energy costs, and significantly shortens the life of the equipment. Based on the analysis of the latest research, it is proposed to improve the quality and composition of water that comes from municipal water supply, artesian wells and reservoirs, before filtering and deaerating water, it is proposed to pre-treat it with hydrocavitation and a magnetic field in order to soften and change its properties. The essence of the operation of the proposed equipment is that the effect of sound hydrocavitation and a variable magnetic field on water is reduced to a single process - the splitting of water molecules in the cavitation cavity into active radicals. The essence of various processes, namely hydrocavitation and magnetic influence on the passage of chemical reactions, breaking of hydrogen bonds in water molecules, is considered. The design of the equipment for the incoming magnetic cavitation preparation of water with an additional hydrocavitation effect on water during the reciprocating movement of the liquid through the nozzle is proposed, which combines the effects of breaking hydrogen bonds in water molecules, oxidation of iron and calcium ions, increasing the Рn indicator, and after its after settling, it is fed to the ion exchange and deaeration units, and later to the heating mains.

In Situ Growth of Mn-Co3O4 on Mesoporous ZSM-5 Zeolite for Boosting Lean Methane Catalytic Oxidation

The low-temperature oxidation of methane gas in coal mine exhaust gas is important for reducing the greenhouse effect and protecting the environment. Unfortunately, the carbon–hydrogen bonds in methane molecules are highly stable, requiring higher reaction temperatures to achieve effective catalytic oxidation. However, metal oxide-based catalysts face the problem of easy sintering and the deactivation of active components at high temperatures, which is an important challenge that catalysts need to overcome in practical applications. In this work, a series of Mn-Co3O4 active components were grown in situ on ZSM-5 zeolite with mesoporous pore structures treated with an alkaline solution via a hydrothermal synthesis method. Due to the presence of polyethylene glycol as a structure-directing agent, manganese can be uniformly doped into the Co3O4 lattice. The large specific surface area of ZSM-5 zeolite allows the active component Mn-Co3O4 to be uniformly dispersed, effectively preventing the sintering and growth of active component particles during the catalytic reaction process. It is worth mentioning that the Mn-Co3O4/meso-ZSM-5-6.67 catalyst has a methane conversion rate of up to 90% at a space velocity of 36,000 mL·g−1·h−1 and a reaction temperature of 363 °C. This is mainly due to the mesoporous ZSM-5 carrier with a high specific surface area, which is conducive to the adsorption and mass transfer of reaction molecules. The active component has an abundance of oxygen vacancies, which is conducive to the activation of reaction molecules and enhances its catalytic activity, which is even higher than that of noble metal-based catalysts. The new ideas for the preparation of metal oxide-based low-temperature methane oxidation catalysts proposed in this work are expected to provide new solutions for low-temperature methane oxidation reactions and promote technological progress in related fields.

Machine Learning model for the prediction of self-diffusion coefficients in liquids, compressed gases and supercritical fluids

Machine Learning (ML) models were developed in this work to predict self-diffusion coefficients (D11) of dense fluids using four training algorithms: Gradient Boosting, k-Nearest Neighbors, Decision Tree, and Random Forest. A database of 7931 experimental points from 223 substances, at different pressures and temperatures, was used to train the models. From an initial set of 34 input features (variables/properties), the eight most important ones, ranked by decreasing relevance, were: density, acentric factor, temperature, critical temperature, critical volume, number of NH and/or OH bonds, pressure, and number of rotatable bonds. The best performance was achieved by models using the first 5 and 8 input features (ML5-D11 and ML8-D11) using the Gradient Boosting algorithm, for which the average absolute relative deviations (AARDglobal) were 9.06 % and 7.14 %, for the test set. The performance of the ML5-D11 and ML8-D11 models was compared with four phenomenological models – the predictive Zhu et al. equation, the 2-parameters Dymond-Hildebrand-Batschinski correlation, and the 1-parameter and 4-parameters Lennard-Jones correlations (LJ1 and LJ4) – which showed AARDglobal of 104.05 %, 82.94 %, 16.92 % and 7.97 %, respectively, for the same test set. Despite the good results of LJ4 equation, it is worth noting it embodies 4 substance-specific parameters that must be fitted to experimental data in advance. The new ML5-D11 and ML8-D11 models are purely predictive and can be applied to polar/nonpolar, spherical/non-spherical, and even hydrogen-bonding molecules in liquids, compressed gases or supercritical fluids. The ML5-D11 and ML8-D11 are provided for use as a Python program.

Binding energies and hydrogen bonds effects on DNA-cisplatin interactions: a DFT-xTB study.

A systematic study of hydrogen bonds in base pairs and the interaction of cisplatin with DNA fragments was carried out. Structure, binding energies, and electron density were analyzed. xTB has proven to be an accurate method for obtaining structures and binding energies in DNA structures. Our xTB values for DNA base binding energy were in the same order and in some cases better than CAM-B3LYP values compared to experimental values. Double-stranded DNA-cisplatin structures have been calculated and the hydrogen bonds of water molecules are a decisive factor contributing to the preference for the cisplatin-Guanine interaction. Higher values of the water hydrogen bonding energies were obtained in cisplatin-Guanine structures. Furthermore, the electrostatic potential was used to investigate and improve the analysis of DNA-cisplatin structures. We applied the xTB method and the CAM-B3LYP functional combined with def2-SVP basis set to perform and analyze of the bonding energies of the cisplatin interaction and the effects of the hydrogen bonds. Results were calculated employing the xTB and the ORCA software.

Percolation transition and bimodal density distribution in hydrogen fluoride.

Hydrogen-bond networks in associating fluids can be extremely robust and characterize the topological properties of the liquid phase, as in the case of water, over its whole domain of stability and beyond. Here, we report on molecular dynamics simulations of hydrogen fluoride (HF), one of the strongest hydrogen-bonding molecules. HF has more limited connectivity than water but can still create long, dynamic chains, setting it apart from most other small molecular liquids. Our simulation results provide robust evidence of a second-order percolation transition of HF's hydrogen bond network occurring below the critical point. This behavior is remarkable as it underlines the presence of two different cohesive mechanisms in liquid HF, one at low temperatures characterized by a spanning network of long, entangled hydrogen-bonded polymers, as opposed to short oligomers bound by the dispersion interaction above the percolation threshold. This second-order phase transition underlines the presence of marked structural heterogeneity in the fluid, which we found in the form of two liquid populations with distinct local densities.

Study on the mechanism of interaction between cations and the surface of nano-SiO2 particle in the salt solution by using molecular dynamics simulation

Nano-SiO2 solution has great potential for application in the field of oil and gas exploration and development. However, its application is restricted due to the aggregation of nano-SiO2 in stratum water. This paper studies the process of interaction between nano-SiO2 particles and salt solutions by using the molecular dynamics simulation experiments, including the characteristics of transportation and diffusion of cations around the nano SiO2, the effect of cations on the recombination and destruction of hydrogen bonds, the interaction energy between cations and nano SiO2. The main results are as follows. During the transportation and diffusion of cations in the solution, the hydrogen bonds of water molecules are broken, so that the hydrogen bonds can be rearranged, and a stable solvated layer can be formed. In the solvated layer, the repulsive force of solvation can prevent the charge exchange between cation and the charged surface of nano SiO2 particle. Compared with the monovalent salt solution, more divalent cations can break through the solvation layer to generate the charge exchange on the surface of nano-SiO2 particle. More divalent cations can conduct small amplitude oscillation movement near the surface of nano-SiO2 particle due to the strong electrostatic effect. When the concentration of salt solution is increased (3000 mg/L → 7000 mg/L) and the valence of cations is increased (monovalent → bivalent), the hydrogen bond is easier to break through the solvation layer to gather on the surface of nano SiO2 particles, which is unfavorable to the stability of nano SiO2 particles. When the cations transport to the position of 7 Å away from the surface of nano-SiO2 particles, the short-range force (including hydrogen bond force, van der Waals force, and electrostatic force) begins to affect the movement of cations. When the cations transport to the position of 2 ∼ 3 Å away from the surface of nano-SiO2 particles, the charge exchange occurs between cations and the surface of nano SiO2 particle, so that the local energy is increased and the cation continues to oscillate. In summary, with the increasing of concentration of salt solution and the valence state, more cations can break through the solvation layer to be adsorbed on the surface of nano SiO2 particle, showing that the ability of transportation and diffusion of cations is weakened, the interaction energy between nano SiO2 particle and salt solution molecules is enhanced. The electrostatic force is the main force to destroy the stability of nano SiO2 particle. The conclusions can provide a certain theoretical basis for the efficient application of nano-SiO2 materials in the field of oil and gas exploration and development and other interrelated industry.

Meteorological Data and Spectral Analyses of Non-Equilibrium Processes in Water during the Total Solar Eclipse of 11.08.1999 in Bulgaria

There are partial or total solar eclipses every year on our planet. They are observed from relatively small areas. From 1950 to 2100, three total solar eclipses fell within the territory of Bulgaria. The two solar eclipses from the 20th century were observed on 15.02.1961 and 11.08.1999. The next total solar eclipse will happen on 3.09.2081. The partial solar eclipses in Bulgaria were on 3.10.2005, 29.03.2006, 1.09.2008, 4.01.2011, and 25.10.2022. The question of the influence of solar eclipses on the Earth’s atmosphere, water, and living organisms is an area of interest for many researchers. In this connection, studies have been conducted on atmospheric and water parameters during partial and total solar eclipses. Most investigations were performed with meteorological data – temperature and humidity. In the last 30 years, other methods have also been applied for the investigations of solar eclipses – spectral methods with infrared (IR) spectroscopy, studies of magnetic and electric fields, polarization, and measurements of the parameters of the fluids in plants. Our studies have used meteorological methods and analyses. For the effects on the water, spectral methods are applied to the non-equilibrium energy spectrum (NES) and differential non-equilibrium spectrum (DNES). A deionized water sample examined during the solar eclipse on 11.08.1999 was used, aiming to analyze the parameters of NES and DNES. The deionized water control sample was tested on 10.08.1999 at the same time as the solar eclipse of the next day. The results of our research show relatively rapid and significant changes in air parameters during a solar eclipse, which are most prominent immediately after its culmination. The conditions of non-equilibrium arising during the solar eclipse allow for studying the restructuring of the hydrogen bonds of water molecules. The results of the current studies prove that the solar eclipse’s significantly affect water which is the primary substance in the Nature and living organisms. These data are consistent with other ones which also prove that, during a solar eclipse, the structure of water undergoes significant changes. By influencing the water, this natural phenomenon affects the whole Nature and all living organisms on the planet.

Investigation of the role of sodium chloride on wheat starch multi-structure, physicochemical and digestibility properties during X-ray irradiation

In this paper, different NaCl content was added to wheat starch and then subjected to X-ray irradiation to investigate the effect of salt on starch modification by irradiation. The results showed that the degradation of wheat starch intensified with the increase in irradiation dose. When irradiated at the same dose, wheat starch with sodium chloride produced shorter chains, lower molecular weight and amylose content, and higher crystallinity, solubility, and resistant starch than wheat starch without sodium chloride. The energy generated by X-rays dissociating sodium chloride caused damage to the glycoside bonds of the starch molecule. With a further increase in the mass fraction of NaCl, the hydrogen bonds of the starch molecules were broken, and the double helix structure was depolymerized, which exacerbated the extent of irradiation-modified wheat starch. At the same time, starch molecules will be rearranged to form a more stable structure.

Ethylenediamine modulate bonding interaction of solvation structure for wide-temperature aqueous ammonium-ion capacitor

Aqueous ammonium-ion capacitors (AAICs) are promising for large-scale energy storage owing to low cost and inherent safety, while their practical applications are suffered from performance under extreme environment. Low ion conductivity and high viscosity, as well as freezing of the electrolyte, are the main issues for the electrochemical performance failure at low temperatures. In this work, the AAICs were assembled with commercial carbon electrodes and antifreeze electrolyte, where the electrolyte with a freezing point lower than −115 °C is developed by using Ethylenediamine (EDA) as an additive with a volume ratio of 50 % to an aqueous solution of 0.5 M NH4Cl. This antifreeze electrolyte displays a superior ionic conductivity of 8.58 mS cm−1 and a weaker viscosity of 8.16 mPa s at low temperatures. Furthermore, the spectroscopic investigations and molecular dynamics (MD) simulations demonstrate that the addition of EDA can break the hydrogen bonds of water molecules and modulate the solvation structure. Therefore, the assembled AAICs with electrolytes of 0.5 M NH4Cl (50 %-EDA) could be operated at wide-temperature conditions steadily, exhibiting excellent capacity, rate performance and good cycling stability. This work provides a simple and effective strategy for wide-temperature energy storage devices.

Proposed crystal structure of carbadox, C11H10N4O4

A model for the crystal structure of carbadox has been generated and refined using synchrotron X-ray powder diffraction data and optimized using density functional theory techniques. Carbadox crystallizes in space group P21 (#4) with a = 13.8155(3), b = 21.4662(1), c = 16.3297(3) Å, β = 110.0931(7)°, V = 4548.10(3) Å3, and Z = 16. The crystal structure is characterized by approximately parallel stacking of the eight independent carbadox molecules parallel to the bc-plane. There are two different molecular configurations of the eight carbadox molecules; five are in the lower-energy configuration and three are in a ~10% higher-energy configuration. This arrangement likely achieves the lowest-energy crystalline packing via hydrogen bonding. Hydrogen bonds link the molecules both within and between the planes. Each of the amino groups forms a N–H⋯O hydrogen bond to an oxygen atom of the 1,4-dioxidoquinoxaline ring system of another molecule. The result is four pairs of hydrogen-bonded molecules, which form rings with graph set R2,2(14). Variation in specimen preparation can affect the preferred orientation of particles considerably. The powder pattern has been submitted to ICDD for inclusion in the Powder Diffraction File™ (PDF®).