Action Of Hydrogen Bonds Research Articles

“Turn-on” fluorescent sensor for glycerol based on hydrazine-bridged bis-tetraphenylimidazole

Glycerol is an important biological molecule, but no facile and on-site fluorescence sensor for detecting glycerol has been reported up to now. In this work, the organic fluorescent sensor for glycerol was prepared based on hydrazine-bridged bis-tetraphenylimidazole (HBT), which exhibited an excellent “turn-on” blue fluorescence response in detecting glycerol for the first time. The good sensing selectivity for glycerol among all kinds of organic molecules and ions was confirmed with the low detection limitation (LOD=0.48 μM). The sensing mechanism was proposed as that the photo-induced electron transfer process between the lone pair electrons of the Schiff group and the tetraphenylimidazole moiety was interrupted by the multiple hydrogen-bond action between glycerol and HBT. The sensing ability of HBT for glycerol was successfully used for the detection of glycerol in test paper and real samples (glycerine enema and aloe vera gel), demonstrating the good potential for simple, rapid and in-situ detection of glycerol in daily life.

γ-AlOOH decorated 3D-reduce graphene oxide: An effective adsorbent for removal of methylene blue and ciprofloxacin

Engineering and synthesis of high-efficiency adsorbent is imperative for water purification. Herein, γ-AlOOH nanoflakes were in-situ decorated onto 3D-reduced graphene oxide (3D-rGO) with the intention of augmenting the specific surface area and ameliorating the adsorption capacity of 3D-rGO in virtue of a facile one-step hydrothermal method. The detailed morphological and structural information of γ-AlOOH/3D-rGO nanocomposite were captured via various instruments. γ-AlOOH/3D-rGO exhibited outstanding removal efficiency towards methylene blue (MB) and ciprofloxacin (CIP) due to its abundant mesopores, increased specific surface area and 3D macro structure. The MB model could well describe the MB adsorption behavior and CIP adsorption process can be fitted by the Elovich model. Isotherm fitting results proclaim that MB adsorption and CIP adsorption followed the Langmuir model; and γ-AlOOH/3D-rGO possessed outstanding adsorption for MB and CIP with the maximum adsorption capacity of 930.0889 mg/g at 288 K and 353.9148 mg/g at 318 K, respectively. The MB and CIP adsorption onto γ-AlOOH/3D-rGO should be the results of the joint action of hydrogen bonds, π-π interaction and complexation. γ-AlOOH/3D-rGO also exhibited excellent reusability after five cycles owing to its 3D macro structure.

Antiferroelectric AgNbO3 @KH550 Doped PVDF/PMMA Composites with High Energy Storage Performance.

The residual polarization of antiferroelectric ceramics is very small, yet they possess high energy storage density and efficiency. Incorporating antiferroelectric ceramic particles into a polymer matrix is beneficial for improving the energy storage performance of composites. However, excessive amounts of ceramic particles can lead to aggregation within the polymer, resulting in defects and a significant reduction in composite film performance. In this study, the antiferroelectric AgNbO3 is selected as the filler and modified with silane coupling agent KH550. poly(vinylidene fluoride) (PVDF) and polymethyl methacrylate (PMMA) are blended as the matrix, and the energy storage performance of the composite is improved by adjusting the additional amount of PVDF. The structure, dielectric properties, and energy storage properties of the composites are systematically studied. The results show that hydrogen bonds are formed between PVDF and PMMA, and PVDF and PMMA are tightly bonded under the action of hydrogen bonds. The compatibility of PVDF with PMMA is optimal when the mass fraction of PVDF is 30 wt%. Moreover, with the synergistic effect of the antiferroelectric filler AgNbO3 , the breakdown strength of AgNbO3 /PVDF/PMMA composites reaches 430kV mm-1 , and the energy storage density reaches 14.35 J cm-3 .

Расчет структуры и инфракрасных спектров поглощения водородно связанных комплексов метилформиата с фтористым водородом

Equilibrium nuclear configurations of three dimers formed by the most stable conformer of a methyl formate molecule with a hydrogen fluoride molecule are calculated using the MP2/aug-cc-pVTZ quantum–chemical method and taking the basis set superposition error into account. The frequencies and intensities for the IR absorption bands of dimers are determined both in the harmonic and anharmonic approximations with the use of the second-order perturbation theory. The calculation method was tested in a calculation of the spectrum of an isolated methyl formate molecule and by comparison with experimental data. The changes in the geometrical parameters of monomers and the charges on atoms under the action of hydrogen bonds were analyzed. The shifts of vibrational frequencies of the monomers upon formation of dimers were calculated. The strongest absorption bands of dimers that can be used in detection of these complexes in spectroscopic experiments were determined.

Enhancing the performance of polylactic acid composites through self-assembly lignin nanospheres for fused deposition modeling

Lignin nanospheres with low cost, high specific surface and good dispersibility have potential high value-added applications. In this study, lignin nanospheres were prepared by dissolving lignin in ethyl acetate (EA), emulsifying, high-speed centrifugation, ultrasonic dispersion and freeze-drying. The particle size distribution of ethyl acetate treated lignin nanospheres (EALNSs) was relatively uniform and concentrated at 200–400 nm, and the thermal stability of the nanospheres was improved to a certain extent. The EALNSs were used as fillers to reinforce polylactic acid (PLA), the processing viscosity of the composites could be effectively reduced, so as to increase the mechanical strength of 3D printing products and significantly enhancing the added value of lignin. The results showed that the EALNSs/PLA composites by adding only 0.50 wt% EALNSs have excellent mechanical properties. Compared with pure PLA, the flexural strength, tensile strength and impact strength of the composites were increased by 130.8%, 56.1% and 14.2%, respectively. Chemical calculation results showed that there was strong hydrogen bond action between EALNSs and PLA. Therefore, the EALNSs/PLA composites can be used as ideal biomass materials for fused deposition modeling.

Stretchable, freezing-tolerant conductive hydrogel for wearable electronics reinforced by cellulose nanocrystals toward multiple hydrogen bonding

Conductive hydrogels have the mechanical properties and the electronic transport properties of conductive polymers, which have been widely used in the fields of energy storage and bioelectronics. However, the rigidity and brittleness of conductive polymers hinder the long-term stability of hydrogels and limit its application in new flexible electronic devices. It is a high challenging task to prepare ion-conductive hydrogels with excellent mechanical properties, anti-freeze and electrical conductivity through a simple preparation process under the action of hydrogen bonds. We present a facile strategy to prepare mechanically tough, swelling ability hydrogels reinforced by cellulose nanocrystals (CNCs). Herein, CNCs were produced by high pressure homogeneous and pretreated with deep eutectic solvent (DES). The conductivity of the hydrogel is 0.021 S/cm at room temperature. Due to the function of DMSO/H2O in organic solvent system, the ion-conducting hydrogel remains flexible and conductive (0.014 S/cm) at −70 °C. Hydrogel has excellent mechanical properties (stress about 1.4 MPa, strain about 1018%), excellent transparency, freezing resistance (−70 °C) and other comprehensive characteristics. The hydrogel can be assembled into a sensor for use in monitoring large and small movements of the human body, showing good responsiveness and stability.

RETRACTED: Study on the Removal Efficiency and Mechanism of Tetracycline in Water Using Biochar and Magnetic Biochar

In this study, a new type of sludge-derived biochar material with high tetracycline removal efficiency, named magnetic Fe3O4 biochar, was accomplished by KOH activated and loaded with magnetic Fe3O4. The particles with spherical pellets observed by SEM, as well as the XRD patterns, indicated that magnetic Fe3O4 nanoparticles were successfully loaded onto the biochar. We studied the adsorption effects and mechanisms of the following three different adsorption materials for tetracycline: biochar (BC), magnetic Fe3O4, and magnetic biochar (MBC), and the loading conditions and reusability of the materials were also considered. The adsorption effects were as follows: Fe3O4 (94.3%) > MBC (88.3%) > BC (65.7%), and the ratio of biochar to ferric salt was 0.2:1; the removal effect reached the best result. Under an acidic condition, the adsorption capacity of all the materials reached the maximum, and the adsorption of tetracycline in water, by three adsorbents, involves chemical adsorption as the leading process and physical adsorption as the auxiliary process. Various characterizations indicated the removal of tetracycline, including pore filling, electrostatic interaction, hydrogen bond action, and cationic-π action. Complex bridging is a unique adsorption mechanism of magnetic Fe3O4 and magnetic biochar. In addition, the magnetic biochar also possesses π–π bond interaction. The magnetic materials can still maintain a certain amount of adsorption capacity on tetracycline after five cycles. This study proved that the magnetic sludge-based biochar are ideal adsorbents for the removal of tetracycline from water, as well as an effective route for the reclamation of waste sludge.

Molecular dynamics simulations of lauric acid confined in carbon nanotube with high thermal conductivity

ABSTRACT In this study, the structure and thermal behaviour of lauric acid (LA) confined in carbon nanotube (CNT) were analysed by the molecular dynamics (MD) method with filling ratios from 10% to 60%. The results showed that LA molecules exhibited a concentric structure from outside to inside. Under the hydrogen bond action, the confined LA molecules moved as a whole cluster and travelled much faster than the bulk. The diffusion ability of confined molecules decreased with the increase of filling ratios under the crowded environment. The thermal conductivity of LA/CNT composites was 116–131 times higher than that of bulk LA.

Study of the microscopic mechanism of lauryl glucoside wetting coal dust: Environmental pollution prevention and control

Molecular dynamics simulation combined with experimental methods were used to investigate the adsorption and wetting process of 25 lauryl glucoside (APG-12) molecules on coal molecules and in turn study the dust suppression mechanism by APG-12 at the molecular level. Through wetting experiments, our preliminary findings showed that APG-12 does have a certain wetting effect on coal dust. According to density functional theory in molecular dynamics simulations, the electrostatic potential and surface charge of the APG-12 and coal molecular models were analyzed to identify their nucleophilic and electrophilic regions, and illustrate the hydrogen bond adsorption mechanism. The dynamics simulation results showed that APG-12 molecules can be easily adsorbed on the surface of coal molecules and then adsorb water molecules around them under the action of hydrogen bonds. This was consistent with the results of an analysis of the system’s radial distribution function and the relative concentration distribution of each component in the Z-axis direction. The results are in good agreement with the experimental results from scanning electron microscopy and energy dispersive spectrometer analysis. These data provide further evidence that APG-12 can clearly improve the wettability and suppression of coal dust, which is of great importance for controlling coal dust pollution.

Investigation of interactions between oxygen-containing groups and water molecules on coal surfaces using density functional theory

The oxygen-containing group is a crucial factor that affects the water wettability of a coal surface. An investigation of the interaction between the oxygen-containing group and water molecule is conducive for understanding the water wettability of the coal surface. In this study, water contact angle measurements and X-ray photoelectron spectroscopy were used to explore the surface wettability and oxygen-containing groups for different rank coals respectively. The adsorption behavior of water molecules on the coal surface was investigated using the density functional theory. The results indicated that the oxygen-containing group enhances the hydrophilicity of the coal surface. In oxygen-containing groups, oxygen atoms possess strong nucleophilicity, and enhance the electrophilicity of hydrogen atoms attached to them. The oxygen atom in the water molecule prefers to form strong hydrogen bonds with the hydrogen atom that is attached to the oxygen atom in the oxygen-containing group. The hydrogen atom in the water molecule prefers to face down, thereby generating a strong van der Waals force on the carbon rings. Based on the combined action of hydrogen bonds and van der Waals force, the effect of oxygen-containing groups on water adsorption capability follows the order –OOH > –OH > –CHO > –OCH3.

Exploration of adsorption mechanism of 2-phosphonobutane-1,2,4-tricarboxylic acid onto kaolinite and montmorillonite via batch experiment and theoretical studies

Two clay minerals, kaolinite (Kaol) and montmorillonite (Mt) with different crystal structures were chosen to investigate the comparative adsorption of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) through batch control experiments and theoretical studies. The systematical isotherm and kinetic studies agreed with Langmuir model and pseudo-second-order model, confirming a monolayer and chemisorption interaction process, respectively. The maximum removal capacities of Kaol and Mt for PBTC were 72.297 mg/g and 121.163 mg/g at pH=3.0 and T=298 K, respectively. Furthermore, the adsorption mechanisms were investigated by molecular dynamic (MD) simulations and density functional theory (DFT). The Interface force field (IFF) was firstly introduced into Materials Studio package to explore the microscopic mechanism of clay mineral interface. The dynamics behaviors verified that the oxygen (O) atom of carboxyl group has stronger affinity at the external surface of Mt, which consistent with the experimental data well. For DFT calculations, quantitative analysis around molecular van der Waals (vdW) surface was adopted to predict reactive sites for the electrophilic reaction. Independent Gradient Model (IGM) and Hirshfeld surface analyses in Multiwfn indicated that the high adsorption effect mainly attributes to hydrogen bond action. These findings improve our ability to explore the related properties occurring at the interface of different clay minerals.

Insights into the mechanism of groove binding between 4-octylphenol and calf thymus DNA.

4-Octylphenol is an endocrine disruptor, belonging to environmental estrogens. It can be enriched in the human body through the food chain and may harm human health. Herein, we used a variety of spectroscopic techniques, molecular docking, and gel electrophoresis to study the interaction of 4-octylphenol and ctDNA. It was found that the mechanism of ctDNA quenching the endogenous fluorescence of 4-octylphenol was static quenching, and formed a complex. The negative enthalpy change (ΔH°), entropy change (ΔS°) and Gibbs free energy (ΔG°) have shown that 4-octylphenol and ctDNA spontaneously bind together under the action of hydrogen bonds and van der Waal's force. Viscosity, melting temperature and iodide quenching experiments showed that 4-octylphenol acted on the groove of ctDNA. Insignificant change in circular dichromism spectra further confirmed this binding mode. The binding sites and groups for 4-octylphenol and ctDNA interaction were identified by molecular docking. Gel electrophoresis found that 4-octylphenol at high concentrations caused DNA cleavage. Above findings may lay a theoretical foundation for understanding the toxicity mechanism of 4-octylphenol.

Design, Synthesis, and Insecticidal Activity of Novel Doramectin Derivatives Containing Acylurea and Acylthiourea Based on Hydrogen Bonding

Our recent investigation on the insecticidal activities of several doramectin derivatives preliminarily revealed that the presence of hydrogen bonds at the C4″ position of the molecule with target protein γ-aminobutyric acid (GABA) receptor was crucial for retaining high insecticidal activity. As a continuation of our research work on the development of new insecticides, two series of novel acylurea and acylthiourea doramectin derivatives were designed and synthesized. The bioassay results indicated that the newly synthesized compounds (5o, 5t, and 6t) exhibited higher insecticidal activity against diamondback moth, oriental armyworm, and corn borer than the control compounds doramectin, commercial avermectins, chlorbenzuron, and lead compound 3g in our laboratory. Specifically, compound 5t was identified as the most promising insecticide against diamondback moth, with a final mortality rate of 80.00% at the low concentration of 12.50 mg/L, showing approximately 7.75-fold higher potency than the parent doramectin (LC50 value of 48.1547 mg/L), 6.52-fold higher potency than commercial avermectins (LC50 value of 40.5507 mg/L), and 3.98-fold higher potency than compound 3g (LC50 value of 24.7742 mg/L). Additionally, molecular docking simulations revealed that compound 5t (2.17, 2.20, 2.56, and 2.83 Å) displayed stronger hydrogen-bond action in binding with the GABA receptor, better than that of compound 5o (1.64 and 2.15 Å) and compound 6t (2.20 and 2.31 Å) at the C4″ position. This work demonstrated that these compounds containing hydrogen-bond groups might contribute to the improvement of insecticidal activity and supply certain hints toward structure optimization design for the development of new insecticides.

Highly efficient methyldiethanolamine (MDEA) removal and light naphtha purification via synergistic effect of molecular sieves and fixed adsorption bed.

Light naphtha is an important raw material for the production of benzene, toluene, and xylene from cracking in tubular furnaces for the production of ethylene and propylene. Light naphtha contains MDEA which is left behind after desulfurization. MDEA remaining in light naphtha will cause high alkalinity of light naphtha, which decreases product quality and increases costs. Additionally, MDEA itself is not easy to degrade and is harmful to human skin, so the removal of MDEA is of great significance for the purification of light naphtha and the protection of the environment. In this paper, a molecular sieve (13X) is compared with silica gel and resin (NKA-9) as a means of removing MDEA from light naphtha via synergism with a fixed adsorption bed. The adsorption capacity decreased in the order of 13X > NKA-9 > silica gel, with values of 53.189, 45.889 and 34.863 mg g–1, respectively. Similarly, the effectiveness of steam for 13X regeneration after adsorption saturation was investigated, and the steam regeneration restored 95% of the activity of the fresh 13X. Furthermore, the adsorption mechanism of MDEA in light naphtha by 13X was studied, and it was confirmed that the adsorption process was dominated by chemisorption, supplemented by physisorption. The –OH and –NH2 functional groups were the main groups involved in the chemisorption, and capillary action and hydrogen bond action may be involved in physisorption.

Polydopamine-bridged synthesis of ternary h-BN@PDA@SnO2 as nanoenhancers for flame retardant and smoke suppression of epoxy composites

The potential prospect of hexagonal boron nitride (h-BN) in the fields of polymer composites is severely limited by undesirable exfoliation efficiency and chemical inertness. Herein, bio-based dopamine was employed toward exfoliating bulk h-BN with hydrogen bond action and imparting a highly-active surface. With assistance of polypodamine, SnO2 nanoparticles were in-situ synthesized and strengthened the interfacial interaction between h-BN and epoxy (EP) matrix. The integrated function of metal oxide/h-BN toward flame retardant and smoke suppression of polymer materials was firstly studied and obtained, in term of reduced peak heat release rate (decreased by 41.1%), lower total heat release (decreased by 30.1%), and suppressed total smoke production (decreased by 21.6%). In addition, the mechanism for enhancements on flame retardant and smoke suppression of EP composites was systematically investigated. Such a design route simultaneously achieves the exfoliation and functionalization of h-BN, thus offering an active platform for further functionalization modification.

Structure, properties and interactions in ionomer/lignin blends

Blends were prepared from lignin and ionomers, i.e. ethylene-methacrylic acid copolymers partially neutralized with inorganic salts for the first time in order to check the possible effect of ionic bonds on the structure and properties of the blends. A low density polyethylene and an ethylene-acrylic acid copolymer without any neutralization were used as references. The lignin content of the blends varied between 0 and 60 vol%. The components were homogenized in an internal mixer and the blends were characterized by various methods including dynamic mechanical analysis, differential scanning calorimetry and tensile testing. The size of dispersed lignin particles was determined from scanning electron micrographs, and component interactions were estimated quantitatively. The properties of ionomer/lignin blends indicated the development of strong interactions between the components. The simultaneous action of hydrogen bonds of non-neutralized methacrylic acid moieties and ionic bonds resulted in the formation of small, dispersed lignin particles of the size of several tenth of a micron. Surprisingly, hydrogen bridges improve interactions and compatibility more than ionic bonds. Contrary to most blends prepared from other polymers, ionomer/lignin blends can be produced with a reasonable combination of properties at moderate lignin contents.

Allergie de contact au cocoyl isethionate de sodium

Molecular dynamics simulation combined with experimental methods were used to investigate the adsorption and wetting process of 25 lauryl glucoside (APG-12) molecules on coal molecules and in turn study the dust suppression mechanism by APG-12 at the molecular level. Through wetting experiments, our preliminary findings showed that APG-12 does have a certain wetting effect on coal dust. According to density functional theory in molecular dynamics simulations, the electrostatic potential and surface charge of the APG-12 and coal molecular models were analyzed to identify their nucleophilic and electrophilic regions, and illustrate the hydrogen bond adsorption mechanism. The dynamics simulation results showed that APG-12 molecules can be easily adsorbed on the surface of coal molecules and then adsorb water molecules around them under the action of hydrogen bonds. This was consistent with the results of an analysis of the system’s radial distribution function and the relative concentration distribution of each component in the Z-axis direction. The results are in good agreement with the experimental results from scanning electron microscopy and energy dispersive spectrometer analysis. These data provide further evidence that APG-12 can clearly improve the wettability and suppression of coal dust, which is of great importance for controlling coal dust pollution.

Conformation and Orientation of Phospholipid Molecule in Pure Phospholipid Monolayer During Compressing

On the basis of energy conservation law and surface pressure isotherm, the conformation energy changes of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) in pure phospholipid monolayer at the air/water interface during compression are derived. The optimized conformations of phospholipids at absolute freedom state are simulated by Gaussian 98 software. Based on following assumptions: (1) the conformation energy change is mainly caused by the rotation of one special bond; (2) the atoms of glycerol near the water surface are active; (3) the rotation is motivated by hydrogen-bond action; (4) the rotation of bond is inertial, one simplified track of conformational change is suggested and the conformations of DPPC and DPPG at different states are determined by the plots of conformation energy change vs. dihedral angle. The thickness of the simulated phospholipid monolayer is consistent with published experimental result. According to molecular areas at different states, the molecular orientations in the compressing process are also developed.

Stepwise self-assembly to improve solar cell morphology

Organic photovoltaic device efficiencies can be greatly improved by controlling the morphology of donor and acceptor domains in the active layer. Connectivity within donor and acceptor domains is of key importance in order to direct charge carriers efficiently to the electrodes. We report here on self-assembly pathways leading towards optimal morphology of solar cell active layers, using as the donor a hairpin-shaped molecule containing a trans-1,2-diamidocyclohexane core and two arms of diketopyrrolopyrrole conjugated segments, and a C71 fullerene derivative as the electron acceptor. Self-assembly of the donor molecule is driven by the synergistic action of hydrogen bonds and π–π stacking, and under proper conditions this results in the formation of long supramolecular nanowires that enhance charge transport and device efficiencies. We found that a stepwise cooling process with minimal stirring of solutions is necessary to create by self-assembly robust wires that are not disrupted when acceptor molecules are added. The efficiencies of devices created by this process can be 400-fold greater than those of devices formed by simple mixing of donor and acceptor molecules. The synergistic action of hydrogen bonds and π stacking in donor molecules that create long nanowires by self-assembly results in devices that are 54% more efficient than those built with analogous donor molecules containing only the conjugated structure.

Synthesis of novel calix[6]-1,4-crown-based netty polymer and its excellent adsorption capabilities for aniline derivatives

By introducing four ester groups on p-tert-butylcalix[6]-1,4-crown-4 and then ammonolysis with ethanolamine, p-tert-butylcalix[6]-1,4-crown-4 amido derivative with four terminal hydroxyl groups (4) was obtained in good yield. Further by reacting compound 4 with 1,1,1-tris(tosylatemethyl)propane (6) in NaH/THF system, the novel netty calix[6]-1,4-crown-based polymer 7 was prepared in “4+3” condensation mode. The structure of polymer 7 was confirmed by elemental analysis, IR and 1H NMR spectra. The loose pores and cross-linked netty architecture were observed for polymer 7 in its SEM images. The M n of polymer 7 was 39,816 which indicated an average of approximately 23 calixarene units in each polymer molecule. Polymer 7 exhibited outstanding adsorption abilities for series of aniline derivatives (aniline, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-nitroaniline, m-nitroaniline and p-nitroaniline). The adsorption percentages for these aniline derivatives were above 90 %. The saturation adsorption capacities for aniline and p-nitroaniline were as high as 2.30 and 2.22 mmol/g, respectively. The adsorption abilities of polymer 7 kept stable at pH 6–10 and it could be re-used after desorption of 10 % HCl. The high adsorption abilities of polymer 7 for aniline derivatives were not just because of π–π stack action of the phenyl groups and the hydrogen bond action, but also due to the stable conformation of calix[6]arene skeleton and big cavity, which were favorable for adsorption of aniline derivatives.