EG Molecules Research Articles

Hierarchical Spatial Confinement Unlocking the Storage Limit of MoS2 for Flexible High-Energy Supercapacitors.

Molybdenum sulfide (MoS2) is a promising electrode material for supercapacitors; however, its limited Mo/S edge sites and intrinsic inert basal plane give rise to sluggish active electronic states, thus constraining its electrochemical performance. Here we propose a hierarchical confinement strategy to develop ethylene molecule (EG)-intercalated Co-doped sulfur-deficient MoS2 (Co-EG/SV-MoS2) for efficient and durable K-ion storage. Theoretical analyses suggest that the intercalation-confined EG and lattice-confined Co can enhance the interfacial K-ion storage capacity while reducing the K-ion diffusion barrier. Experimentally, the intercalated EG molecules with mildly reducing properties induced the creation of sulfur vacancies, expanded the interlayer spacing, regulated the 2H-1T phase transition, and strengthened the structural grafting between layers, thereby facilitating ion diffusion and ensuring structural durability. Moreover, the Co dopants occupying the initial Mo sites initiated charge transfer, thus activating the basal plane. Consequently, the optimized Co-EG/SV-MoS2 electrode exhibited a substantially improved electrochemical performance. Flexible supercapacitors assembled with Co-EG/SV-MoS2 delivered a notable areal energy density of 0.51 mW h cm-2 at 0.84 mW cm-2 with good flexibility. Furthermore, supercapacitor devices were integrated with a strain sensor to create a self-powered system capable of real-time detection of human joint motion.

Atomistic insights into the performance of thermodynamic inhibitors in the nucleation of methane hydrate

Figure TOC Comparison of methane hydrate nucleation process (a) without or (b) with EG molecules. Critical nucleus size increase under the influence of Thermodynamic hydrate inhibitors. • Hydrophobic groups from the alcohols could approach the initial hydrate cages and destroy initial clusters. • The –OH groups were observed to form hydrogen bonds with the cage clusters and even initiate a new hydrate cage. • Alcohols can increase the critical nucleus size of gas hydrate. Thermodynamic inhibitors are intensively used in oil and gas pipelines to modify the formation conditions of gas hydrate, preventing the blockage of pipelines. However, their kinetic performance in hydrate nucleation is largely unclear. Herein, the molecular interactions of the small molecules of ethylene glycol and methanol with hydrate clusters were investigated. It was found that the hydrophobic groups from the glycols could approach the initial hydrate cages, thereby constricting the regional distribution of adjacent water molecules; thus, they functioned in the same way as the guest molecules that transiently helped to stabilize the water framework. However, these glycols would eventually dissolve into the solution to stay at the water/nanobubble interface; this would consequently destroy the initial cages upon losing the constraint from the surrounding hydrophobic molecules. In addition, the –OH groups were observed to form hydrogen bonds with the cage clusters and even initiate a new hydrate cage; however, they cannot stably reside there due to different atom coordination. Notably, these glycols can increase the critical nucleus size, which is considered the intrinsic mechanism of thermodynamic inhibition. Our results provide atomistic insights into the performance of glycols in the kinetic nucleation of gas hydrates and can help understand the interactions between guest and host molecules in the presence of hydrophobic and hydrophilic functional groups.

Alkali-free synthesis of hexagonal star-like Fe-ethylene glycol (Fe-EG) complex and subsequently decomposition to α-Fe2O3 and Fe3O4/α-Fe/C composites

• Hexagonal star-like Fe-EG complex was synthesized by a surfactant-and alkali-free solvothermal method. • Hexagonal star-like α-Fe 2 O 3 and Fe 3 O 4 /α-Fe/C were obtained after thermal treatment. • The saturation magnetisation of α-Fe 2 O 3 and Fe 3 O 4 /α-Fe/C were 17.07 and 86.95 emu g −1 , respectively. • The adsorption capacity of Fe 3 O 4 /α-Fe/C towards Congo red was 230.9 mg g −1 . Using ferric nitrate as iron source, hexagonal star-like Fe-ethylene glycol (Fe-EG) complex was synthesized using an alkali-and surfactant-free solvothermal method. The formation of the Fe-EG complex was attributed to the hydrolysis of ferric ions, the oxidation-reduction between EG molecules and nitric acid derived from the hydrolysis of ferric ions, and the reaction between the Fe-O sheets and the deprotonated hydroxyl and carboxyl groups. Hexagonal star-like α-Fe 2 O 3 and Fe 3 O 4 /α-Fe/C composites were obtained after thermal treatment. The saturation magnetisation of them were 17.07 and 86.95 emu g −1 , respectively. The adsorption of the obtained Fe 3 O 4 /α-Fe/C composites towards Congo red (CR) can be well fitted by the Langmuir model, and the maximum adsorption capacity was 230.9 mg g −1 . The results put forward an effective approach for the synthesis of metal alkoxides with a special microstructures.

Distinct Solvation Structures of CO2 and SO2 in Reline and Ethaline Deep Eutectic Solvents Revealed by AIMD Simulations.

Deep eutectic solvents (DESs) are emerging as an alternative media for the sequestration of greenhouse gases such as CO2 and SO2. Herein, we performed ab initio molecular dynamics (AIMD) simulations to elucidate the solvation structure around CO2 and SO2 in choline chloride-based DESs, namely, reline and ethaline. We show that in all four systems the structures of the nearest neighbor shells around these molecules are distinct. We observe that because of the electrophilic character, the carbon atom of CO2 and the sulfur atom of SO2 are preferentially solvated by the chloride anions. The strength of the correlation between the chloride anions and the sulfur atom is much stronger because of charge transfer, which is more profound in ethaline DES. In both DESs, the choline cations are found to be closer to the oxygen atoms of CO2 and SO2. We observe that upon changing the solute from CO2 to SO2, the nearest neighbor solvation structure changes drastically; while the chloride anions prefer to stay in a circular shell around the carbon atom of CO2, they are found to be much more localized near the sulfur atom of SO2. The solvation shells formed by the urea molecules in reline and EG molecules in ethaline also overlap with that of the chloride anion around CO2. In ethaline, the hydroxyl group of the choline cation is found to be closer to the solute molecules as compared to its ammonium headgroup.

Are There Magic Compositions in Deep Eutectic Solvents? Effects of Composition and Water Content in Choline Chloride/Ethylene Glycol from Ab Initio Molecular Dynamics.

Ab initio molecular dynamics simulations at elevated temperature are carried out to investigate the microscopic structure of liquid mixtures (deep eutectic solvents) composed of 1:1 and 1:2 choline chloride:ethylene glycol ([Ch]Cl:EG) and 1:2:1 choline chloride:ethylene glycol:water ([Ch]Cl:EG:water). In the present study, we aim to understand the composition effect on the choline chloride:ethylene glycol deep eutectic solvent and whether there is a specific composition in these solvents with marked special behavior at the microscopic level. The role of hydrogen bonds between all components was investigated through distribution functions. The structures are governed by the balance of hydrogen bond networks and the different populations of the EG molecule conformations. In the water-containing system, water competes for association with the anion. Also, the charge distribution analysis, which is consistent with structural analysis, indicates that the results are not impacted by changing composition. In addition, the charge transfer observed between ions, EG, and water molecules appears to be significant.

Unique 3D flower-on-sheet nanostructure of NiCo LDHs: Controllable microwave-assisted synthesis and its application for advanced supercapacitors

Two-dimensional (2D) nanostructures, though promising in energy storage, suffer from aggregation and subsequent deterioration of performance in practical applications. Hence, assembly of 2D nanostructures into three-dimensional (3D) architectures is highly desirable. Here, we report a microwave-assisted approach to the controllable synthesis of 2D materials with tunable 3D structures simply by adjusting the ratio of water/ethylene glycol (H2O/EG). Novel flower-on-sheet 3D hierarchical structures of nickel cobalt double hydroxide (NiCo LDHs) are obtained at EG content of 40%, while microspheres and 2D nanosheets are obtained when the EG content is 0% and 75%, respectively. We propose that under microwave irradiation, EG molecules disperse the nuclei and facilitate the initial formation of 2D sheets. Subsequently, the dominating hydrophobicity of the assembling results in the formation of nanoflowers on the sheets. When tested as electrode materials in supercapacitors, the flower-on-sheet NiCo LDH exhibits superior capacitance (1187.2 F g−1 at 1 A g−1), good rate capability (71% retention at 30 A g−1), and high stability (only 0.3% cyclic decay per cycle with respect to the first charge capacitance), which is ascribed to that ‘sheet’ could act as buffer substrate while ‘flower’ expose more active site. Our results demonstrate an energy-saving and one-pot approach for controllable construction of 2D derived 3D nanostructure that can be applied in next-generation energy storage materials.

Observation of conformational changes in ethylene glycol–water complexes by FTIR–ATR spectroscopy and computational studies

Attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectra of ethylene glycol–water (abbreviated as EG–H2O) mixtures were measured at 298 K with the ethylene glycol molar ratio ranging from 0.01 to 1400. The two bands at 1033 and 1082 cm-1 were assigned to be the C-C stretching vibration modes related to the trans- and gauche- conformation of EG. The absorbance of the two bands was found to be sensitive to the molar ratios. We made theoretical calculation for ten conformations of the EG molecules to understand the conformational transformation of EG molecules changing with EG–H2O molar ratios. The absorbance ratio (A1033/A1082) was used to determine the trans- and gauche- conformation ratio with the calculated (AνO-C-C-O-T/AνO-C-C-O-G) as standard. When the molar ratio of water and EG (xH2O/xEG) is smaller than 0.4, strong associations formed by the intermolecular hydrogen bonds were dominant in the solutions and the proportion of gauche- conformation was about 0.5. Within the region of 0.4< xH2O/xEG < 20, the intermolecular hydrogen bonds structure between EG molecules were broken by the water molecules and the structure of most EG molecules changed from trans- to gauche- conformation. The blue shift of the peaks indicated the increasing hydrogen bonding between water and EG. When xH2O/xEG is larger than 20, the monomers of molecules started to appear in the EG–H2O solution. The gauche- conformation was the dominated conformation in the dilute EG–H2O solution with proportion of 0.87. In the CH2 rocking vibration (δC-H) region, the computational results showed that the majority bands in this region were influenced by the gauche- conformation which can be divided into group G1 or G2. The transformation between the gauche- conformations of EG molecules can be studied by combining the experimental results and the computational results, The proportion of G1 for the EG-rich solution was about 0.71 while it decreased to 0.55 for the H2O–rich solution.

Role of Li + ions on the luminescence properties in water dispersible mesoporous CaF 2 : Eu 3 + nanocrystals

Polyvinyl pyrrolidone- (PVP) and ethylene glycol- (EG) coated water dispersible mesoporous CaF2:Eu3+,Li+ nanocrystals were synthesized by a simple one-pot hydrothermal method. The role of Li+ ions on the morphology and spectra in the CaF2 nanocrystals have been reported. The synthesized nanocrystals were monodisperse with regular sphere-like shapes and exhibited obvious hollow mesoporous structure. The results from x-ray photoelectron spectroscopy determined the successful incorporation of Eu3+ ions and Li+ ions into the CaF2 host lattice. The excitation and emission intensity of Eu3+ enhanced with Li+ concentration until 7 mol.%. The nanocrystals could disperse in water for more than a month due to the EG and PVP molecules coated over the nanocrystals.

The noble effect of aging on the thermal conductivity of modified CNTs-ethylene glycol nanofluids

ABSTRACTIn order to improve the heat transfer process by using nanofluids, different nanoparticles and base fluids have been studied. In this work, stability and effect of aging and temperature on the thermal conductivity of CNTs-ethylene glycol (EG) nanofluids were investigated. Chemical functionalisation was used to oxidise the surface of CNTs. The functionalised CNTs were used to prepare the nanofluids by a two-step method. The stability of nanofluids was measured by UV-vis spectroscopy and the results showed that the nanofluids had a good stability over several days. Immediately after nanofluid preparation not too much increase was observed for thermal conductivity but the nanofluid aging had a great influence on the improvement of the thermal conductivity, as after 65 days, about 50% increase was observed. The increase has been attributed to forming an ordered nanolayer of EG molecules around the CNTs. Also no significant temperature dependence of thermal conductivity was observed up to 50°C possibly due to the lack of temperature dependence of CNTs Brownian motions.

A molecular dynamics simulations study on ethylene glycol-water mixtures in mesoporous silica.

We perform molecular dynamics simulations to investigate structural and dynamical properties of ethylene glycol-water (EG-WA) mixtures in mesoporous silica. To obtain comprehensive insights into the dependence of liquid behaviors on the confinement features, we exploit that straightforward modification of the force field parameters allows us to vary the properties of the hydrogen-bond network of the confined liquid, we alter the polarity of the silica surface, and we consider amorphous as well as crystalline matrices. It is observed that the confinement induces a micro-phase separation in the liquid, which qualitatively depends on the properties of both liquid and matrix so that EG or WA molecules may be preferentially adsorbed at the silica surface. Furthermore, it is found that the confinement strongly affects the liquid dynamics. Largely independent of the polarity and structure of the matrix, structural relaxation is about a factor of 10(4) slower at the pore wall than in the pore center. Moreover, the non-Arrhenius temperature dependence of the bulk mixture turns into an Arrhenius behavior of the confined mixture so that the spatial restriction can slow down or speed up the structural relaxation, depending on temperature.

On the Perturbation of the H-Bonding Interaction in Ethylene Glycol Clusters upon Hydration

Ab initio and density functional methods have been employed to study the structure, stability, and spectral properties of various ethylene glycol (EG(m)) and ethylene glycol-water (EG(m)W(n)) (m = 1-3, n = 1-4) clusters. The effective fragment potential (EFP) approach was used to explore various possible EG(m)W(n) clusters. Calculated interaction energies of EG(m)W(n) clusters confirm that the hydrogen-bonding interaction between EG molecules is perturbed by the presence of water molecules and vice versa. Further, energy decomposition analysis shows that both electrostatic and polarization interactions predominantly contribute to the stability of these clusters. It was found from the same analysis that ethylene glycol-water interaction is predominant over the ethylene glycol-ethylene glycol and water-water interactions. Overall, the results clearly illustrate that the presence of water disrupts the ethylene glycol-ethylene glycol hydrogen bonds.

Thermodynamic and spectroscopic studies on binary mixtures of imidazolium ionic liquids in ethylene glycol

The thermodynamic behaviour of imidazolium based ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride [C 4mim][Cl]; 1-octyl-3-methylimidazolium chloride [C 8mim][Cl], and 1-butyl-3-methylimidazolium methylsulfate [C 4mim][C 1OSO 3] in ethylene glycol [HOCH 2CH 2OH] (EG) have been investigated over the whole composition range at T = (298.15 to 318.15) K to probe the interactions in bulk. For the purpose, volumetric properties such as excess molar volume, V m E , apparent molar volume, V ϕ , i , and its limiting values at infinite dilution, V ϕ , i ∞ , have been calculated from the experimental density measurements. The molecular scale interactions between ionic liquids and EG have been investigated through Fourier transform infrared (FTIR) and 1H NMR spectroscopy. The shift in the vibrational frequency for C–H stretch of aromatic ring protons of ILs and O–H stretch of EG molecules has been analysed. The NMR chemical shifts for various protons of RTILS or EG molecules and their deviations show multiple hydrogen bonding interactions of varying strengths between RTILs and EG in their binary mixtures.

Catalyst-free low temperature synthesis of discrete anatase titanium dioxide nanocrystals with highly thermal stability and UVC-cut capability

A novel, facile, catalyst-free, and low temperature process for the synthesis of discrete anatase TiO2 nanocrystals has been developed in the absence of stabilizing agent. The product was shown to be discrete anatase TiO2 nanocrystals with a mean diameter of 4.97 ± 0.9 nm and a specific surface area of 393 m2/g. By varying the water content and precursor concentration, the particle size could be tuned. Also, the resultant colloid solution was quite stable even in the absence of stabilizing agent because of the coverage of EG molecules on the particle surface. In addition, the anatase TiO2 nanocrystals obtained in this work had highly thermal stability even at temperatures up to 800 °C. Also, as compared to Degussa P25 TiO2 powders, they exhibited stronger absorption at 200–350 nm and higher transmittance in the visible light region. Thus, the new approach proposed in this work was practicable for the synthesis of anatase TiO2 nanocrystals, particularly for those requested to have highly thermal stability and UVC-cut capability.

Low frequency dielectric relaxation processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone)−ethylene glycol blends

The dielectric dispersion behaviour of montmorillonite (MMT) clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone)-ethylene glycol (PVP-EG) blends were investigated over the frequency range 20 Hz to 1 MHz at 30°C. The 0, 1, 2, 3, 5 and 10 wt% MMT clay concentration of the weight of total solute (MMT+PVP) were prepared in PVP-EG blends using EG as solvent. The complex relative dielectric function, alternating current (ac) electrical conductiv- ity, electric modulus and impedance spectra of these materials show the relaxation processes corresponding to the micro- Brownian motion of PVP chain, ion conduction and electrode polarization phenomena. The real part of ac conductivity spectra of these materials obeys Jonscher power law σ'(ω )= σdc + Aω n in upper frequency end of the measurement, whereas dispersion in lower frequency end confirms the presence of electrode polarization effect. It was observed that the increase of clay concentration in the PVP-EG blends significantly increases the ac conductivity values, and simultaneously reduces the ionic conductivity relaxation time and electric double layer relaxation time, which suggests that PVP segmen- tal dynamics and ionic motion are strongly coupled. The intercalation of EG structures in clay galleries and exfoliation of clay sheets by adsorption of PVP-EG structures on clay surfaces are discussed by considering the hydrogen bonding inter- actions between the hydroxyl group (-OH) of EG molecules, carbonyl group (C=O) of PVP monomer units, and the hydroxylated aluminate surfaces of the MMT clay particles. Results suggest that the colloidal suspension of MMT clay nano particles in the PVP-EG blends provide a convenient way to obtain an electrolyte solution with tailored electrical con- duction properties.

Diffusive relaxation processes and low-frequency dynamical properties in bulk and confined ethylene glycol by neutron spectroscopy

In this work, we report on a detailed study of the diffusional and vibrational dynamics of liquid ethylene glycol (EG: HO–CH2CH2–OH) in the bulk state and confined in a matrix of sol-gel porous glass with 26 Å interconnected cylindrical pores. The investigation is performed, by incoherent quasielastic and inelastic neutron scattering (IQENS and IINS), as a function of temperature. IQENS data have been definitively interpreted in terms of the α-relaxation dynamics predicted by mode coupling theory for supercooled liquids. We verified that a description by means of an Havriliak–Negami profile is consistent with the measured spectral line shape. Furthermore, IINS spectra show a clear different evolution versus T of the vibrational density of states, Z(ω), passing from the bulk samples to the confined ones, revealing, in particular, a thermal stabilization of the disordered longitudinal acoustic mode induced by interaction of EG molecules with the active silanol (Si–OH) groups of the surface.

Vibrational dynamics of ethylene glycol in mesoscopic confinement by incoherent inelastic neutron scattering (IINS) investigation

In this paper, we go deeply into an analysis performed, as a function of T, by means of incoherent inelastic neutron scattering (IINS), of vibrational dynamics of liquid ethylene glycol (EG: HO–CH 2CH 2–OH) in the bulk state and confined into 26 Å interconnected cylindrical pores of a sol-gel porous glass. IINS spectra revealed, as far as the vibrational density of states, Z( ω) is concerned, a different trend in temperature passing from bulk to confined samples. In particular, we observed a thermal stabilization of the disordered longitudinal acoustic mode as a consequence of the interaction between the hydroxyl groups (OH) of the EG molecules and the active silanol groups (Si–OH) on the surface of the porous glass.

Cetylpyridinium chloride[ndash ]tetradecyltrimethylammonium bromide mixed micelles in ethylene glycol[ndash ]water and diethylene glycol[ndash ]water mixtures

The conductances of cetylpyridinium chloride (CPyCl)–tetradecyltrimethylammonium bromide (TTAB) mixtures over the entire mole fraction range of CPyCl (xCPyCl) have been measured in water, ethylene glycol–water (EG–W) and diethylene glycol–water (DEG–W) mixtures consisting of 20, 40 and 60 wt.% EG and DEG in their respective binary mixtures at 30 °C. From the conductivity data, the mixed critical micellar concentration (cmc), degree of counter-ion dissociation (χ), standard Gibbs energy of transfer of the surfactant hydrocarbon chain from medium to the micelle (ΔGHP°), and Gibbs energy of transfer of surface contributions (ΔGs°) for mixed micelles were computed. The non-ideality in the mixed micelle formation was evaluated by using the regular solution theory extended by Rubingh. It was observed that the non-ideality decreases with increase in the amount of EG or DEG. This was attributed to the solvation of the surfactant hydrophobic tail by EG or DEG molecules owing to EG or DEG–hydrocarbon interactions.

Molecular dynamics of flexible molecules: torsional motions of n-butane and ethylene glycol

Molecular dynamics simulations have been performed for liquid n-butane and ethylene glycol (1,2-ethanediol; EG) in order to understand liquid structures in terms of both inter- and intra-molecular interactions. Each n-butane molecule consists of four sites interacting with LJ potential, and with only one dihedral angle potential, while each EG molecule has six sites interacting through LJ and coulomb potentials together with three dihedral angle potentials. The flexible molecule has the tendency to be folded more intensely in the liquid state than that in the gas phase. Comparing aqueous solution of EG with Xe solution and gaseous state of EG, it is found that EG molecules more strongly favor the folded form by intramolecular interactions, especially by intramolecular hydrogen bond.

Molecular dynamics simulations of flexible molecules. Part 1.—Aqueous solution of ethylene glycol

Molecular dynamics simulations have been performed for ethylene glycol (ethane-1,2-diol, EG) in water. Each EG molecule consists of six sites interacting through Lennard-Jones and coulomb potentials together with three dihedral angle potentials. A comparison of the behaviour of EG molecules in water and in Xe shows that in the latter solvent the EG molecules tend to fold, unlike those in water. In order to investigate how the intramolecular interaction affects the intermolecular hydrogen bonds, some rigid-EG models are also examined.