Solvent Effect Of Water Research Articles

Modeling hydration of graphene oxide (GO) – Does size matter?

The biomedical applications of graphene-based materials become one of hot scientific and technological topics in the last few years. Flake graphene oxide (GO) is considered as one of the promising materials for biomedical use due to a number of specific properties, in particular in design of advanced drug delivery systems (DDS). The key factor in the formation of non-covalently bonded complexes for drug transport is the strength of non-covalent interactions of the carrier with both the drug and the environment. In the current work, we have focused on molecular modeling of solvation of zigzag-edged graphene oxide, functionalized with hydroxyl and carboxyl substituents. The hydration was determined from the magnitude of weak intermolecular interactions of GO with one or two water molecules. Our goal was to establish the dependence of the degree and type of functionalization, as well as the size of graphene flakes and the position of hydrophilic substituents on the number and strength of H-bonds. All calculations were performed using density functional theory (DFT) at the B3LYPD3BJ/6-311++G** level. The effect of water solvent was established using an explicit (discrete) model of solvent.

Unexpected longer T1 lifetime of 6-sulfur guanine than 6-selenium guanine: the solvent effect of hydrogen bonds to brake the triplet decay.

The decay of the T1 state to the ground state is an essential property of photosensitizers because it decides the lifetime of excited states and, thus, the time window for sensitization. The sulfur/selenium substitution of carbonyl groups can red-shift absorption spectra and enhance the triplet yield because of the large spin-orbit coupling, modifying nucleobases to potential photosensitizers for various applications. However, replacing sulfur with selenium will also cause a much shorter T1 lifetime. Experimental studies found that the triplet decay rate of 6-seleno guanine (6SeGua) is 835 times faster than that of 6-thio guanine (6tGua) in aqueous solution. In this work, we reveal the mechanism of the T1 decay difference between 6SeGua and 6tGua by computing the activation energy and spin-orbit coupling for rate calculation. The solvent effect of water is treated with explicit microsolvation and implicit solvent models. We find that the hydrogen bond between the sulfur atom of 6tGua and the water molecule can brake the triplet decay, which is weaker in 6SeGua. This difference is crucial to explain the relatively long T1 lifetime of 6tGua in an aqueous solution. This insight emphasizes the role of solvents in modulating the excited state dynamics and the efficiency of photosensitizers, particularly in aqueous environments.

Design, synthesis, and density functional theory studies of a new selective chemosensor for Pb2+

Herein, we have focused on a new colorimetric ligand synthesized from the reaction of 2-hydroxy-5-methylbenzene-1,3-dialdehyde with 2-amino-thiophenol, and investigated its activity as a sensor. In this regard, the sensory activity of the ligand towards different ions (Mn2+, Cu2+, Co2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Ag+, Na+, Cs+, Mg2+, Al3+, Ba2+, K+, and Pb2+) was studied. The specificity of ion bindings is discussed through UV–Vis analysis. The ligand that was synthesized showed remarkable sensitivity, with a detection limit of 0.001 ppb. Additionally, the presence of Pb2+ ions can be visually detected through a color change from colorless to yellow. In the last part of this work, we seek to predict the available experimental measurements. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) are employed to examine the bonding between the ligand and the Pb2+ ion. The effect of water solvent was thoroughly examined for all the steps via the conductor-like Polarizable Continuum Model (CPCM). The theoretical findings revealed that electronic properties, including energy gap, adsorption energy, charge/energy transfer, and optical characteristics, undergo significant changes when Pb2+ cations are present. Hence, it can be inferred that the newly synthesized chemosensor (NC) is highly efficient in detecting Pb2+.

C24 Fullerene and its derivatives as a viable glucose sensor: DFT and TD-DFT studies

The requirement of highly sensitive, selective and responsive sensor for biomolecules remains a subject of great interest and under the development. We aimed to explore new 0D materials such as C24, Al12N12 and Al12P12 fullerenes for glucose sensing using dispersion (D3) corrected Density functional calculation with B3LYP/6–31G(d,p) basis sets. Among these Al12P12 and Al12N12 show the strong chemisorption and charge is transferred from fullerenes to Glucose(Glu) while an optimal adsorption has been found for C24 with glucose in which charge is transferred from glucose to fullerene. Adsorption energy calculation, NBO analysis, Mulliken charge analysis, DOS calculation, RDG analysis, sensing response and UV spectra analysis have been performed to justify the interaction between glucose and C24 and their derivatives. All calculations favor our expected results and concludes that for Al12N12 and Al12P12 can be used for glucose isolation from mixture of the other biomolecules due to their high recovery time in range of 1019 and 1011 s while C24 as a detection purpose. Based on the Mulliken charge analysis it has been observed that charge have been transferred from Glucose to Al12N12 and Al12P12. On the effect of water solvent, it is observed that the nature of the adsorption for Al12N12 and Al12P12 towards glucose remains the same and it confirms their application as carrier.

Probing the water mediated proton transfer in histidine tautomerization

Histidine tautomerism plays a key role in the aggregation of amyloid peptides, which is important for understanding the origin of Alzheimer’s disease as well as its diagnosis and treatment. Herein, density functional theory calculations were performed using explicit water molecules and joint implicit/explicit water cluster models to explore the catalytic mechanism and the key role of water assistance effect in the histidine tautomerization reaction. To clarify the proton transfer mechanism involved in histidine tautomerization, three to five water molecules were used to catalyze the proton transfer process governing the transition between the histidine tautomers. Potential energy calculations showed that hiε·(H2O)n tautomerism proceeds via a single proton transfer pathway. Systematic analyses of the hydrogen bonds and charge distribution of the key components indicated that tautomerism can be promoted by reducing the number of assistant water molecules or involving the joint implicit/explicit water solvent effect. This study provides theoretical insights into the mechanism of water-assisted histidine isomerization as it relates to the Aβ aggregation hypothesis of Alzheimer’s disease.

Solvent effects of water on the decarboxylation of o-phthalic acid in supercritical water

Water's effect on o-phthalic acid decarboxylation was studied by varying the pressure from (20 to 40) MPa at (380, 400, and 420) °C. The rate constants decreased with increasing pressure at (400 and 420) °C, but remained nearly constant at 380 °C. The trends at (400 and 420) °C were explained using Kirkwood theory, which proposed preferential solvation of the reactant over the transition state. The 380 °C trend was thought to be explained by solvent inhomogeneities and water's peculiar behavior near the critical point. Solvent inhomogeneities were most likely responsible when rates remained low despite low dielectric constant values. These inhomogeneities could have caused a higher local dielectric constant around the solute, suppressing the rate in a manner similar to the higher-pressure region. Water, according to these findings, has the greatest influence on the reaction via solvation.

Highly Reversible Intercalation of Calcium Ions in Layered Vanadium Compounds Enabled by Acetonitrile-Water Hybrid Electrolyte.

Currently, the development of calcium-ion batteries (CIBs) is still in its infancy and greatly plagued by the absence of satisfactory cathode materials and compatible electrolytes. Herein, an acetonitrile-water hybrid electrolyte is first developed in CIB chemistry, in which, the strong lubricating and shielding effect of water solvent significantly boosts the swift transport of bulky Ca2+, thus contributing to large capacity storage of Ca2+ in layered vanadium oxides (Ca0.25V2O5·nH2O, CVO). Meanwhile, the acetonitrile component noticeably suppresses the dissolution of vanadium species during repeated Ca2+-ion uptake/release, endowing the CVO cathode with a robust cycle life. More importantly, spectral characterization and molecular dynamics simulation confirm that the water molecules are well stabilized by the mutual hydrogen bonding with acetonitrile molecules (O-H···N), endowing the aqueous hybrid electrolyte with high electrochemical stability. By using this aqueous hybrid electrolyte, the CVO electrode shows a high specific discharge capacity of 158.2 mAh g-1 at 0.2 A g-1, an appealing capacity of 104.6 mAh g-1 at a high rate of 5 A g-1, and a capacity retention of 95% after 2000 cycles at 1.0 A g-1, which is a record-high performance for CIBs reported so far. A mechanistic study exemplifies the reversible extraction of Ca2+ from the gap of VO polyhedral layers, which are accompanied by the reversible V-O and V-V skeleton change as well as reversible variation of layer spacing. This work constitutes a major advance in developing high-performance Ca-ion batteries.

Unique solvent effect of water in radical cyclization reaction

The radical cyclization reaction in the aqueous environment by Yorimitsu et al. is revisited using the RISM-SCF-cSED method, a hybrid of quantum chemistry and statistical mechanics theory for molecular liquids. The difference between the barrier height of the forward reaction from the intermediate E-rot, the cyclization step, and that of the backward reaction is crucial to the reaction yield. Considering the effect of hydrogen bonding through the RISM theory, we found that the barrier height for the forward reaction is lower, especially in water. In other words, considering microscopic solvation effects clearly shows the difference between water and DMSO solvents, explaining the remarkable acceleration of the reaction in the aqueous environment.

Hydrogenative rearrangement of bioderived furfurals to cyclopentanones over Ni/Nb2O5 catalysts: Promotion effect of reducible NbOx and water

Selective aqueous hydrogenation of furfurals to valuable cyclopentanones is attractive for biomass utilization. Herein, Ni/Nb2O5 catalysts with different calcination temperatures were synthesized and employed to study the effect of reducible NbOx species and water solvent on the aqueous hydrogenation-rearrangement of furfural. A significantly higher cyclopentanone (CPO) yield (>92 %) was achieved in water on Ni/Nb2O5-500, while no CPO was detected in heptane. Catalysts characterization indicated that the calcination temperature of Nb2O5 determined the crystallinity and modulated reducible NbOx. Kinetic and isotopic experiments elucidated that the excellent catalytic performance of Ni/Nb2O5 remarkably correlated with surface reducible NbOx species and H2O-mediated effect. NbOx species closely interacted with Ni sites, in which Ni was in charge of H2 activation and NbOx facilitated furfural adsorption via flat configuration. Water helped furfural activation and active hydrogen transfer between Ni sites and adsorbed furfural on NbOx sites, thus significantly boosted aqueous hydrogenation of furfural to CPO.

Solvent effect of water on the UV-B absorption of plant sunscreen agents

These authors contributed equally to this work. UV-B (280-320 nm) sunscreening is crucial for lives on Earth. Examining the role of surrounding of UV-B screening molecules can help us better understand UV-B absorption. Water is ubiquitous in cells as the solvent, but its impacts on UV-B absorption of sunscreen agents are underexplored. Herein, we report a first-principle study on UV-B absorption of sinapate malate (SM) and relevant molecular species, with a focus on the solvent effect of water. The capability of UV-B screening by anions of SM, the proposed species for actual sunscreening, is shaped by water. Both the implicit water providing the dielectric environment of solvation and the explicit water molecules forming hydrogen bonding to SM anion can appreciably alter the nature of transition orbitals responsible to the UV-B absorption of the anion. Finally, we find the molecular dipole moment of an organic UV-B screening agent can be an indicator of its UV-B screening sensitivity to the surrounding water. Our work may serve as a starting point of developing new water-soluble UV-B screening agent.

The chemical reaction of thioindole and [20] fullerene and the use of DFT to estimate some quantum chemical descriptors

In this study, the solvent effects are probed on the chemical reaction of the (E)-3-thiophene-2-yl-indoline-2-thione (I) and [20] fullerene, and the resulted complex (Ia ) via the density functional theory (DFT). To characterize the synchronicity of the reaction and its correlation with activation energy, we estimated the energy barrier of transition states (E TS1 ≠ and E TS2 ≠) in the used solvents. The highest E TS1 ≠ and E TS2 ≠ value are found in water solvent, whereas the lowest E TS1 ≠ and E TS2 ≠ value are considered in the gas phase. Formation of the TS2 appears energetically less favorable due to the non-bonding electrostatic repulsion among the sulfur heteroatoms and C20 , also the π–stacking between the thiophene ring and nanocage, which affects the stability of the TSs. The most thermodynamic stability, the adsorption energy difference among liquid phase and gas phase (ΔE l-g = E l − E g), and the most polarity (µ) belongs to stabilizing effect of water solvent on Ia , whereas the lowest thermodynamic stability, the lowest released ΔE l-g and the least polarity belongs to optimization of Ia in the gas phase. This stabilizing effect is attributed to the possibility of hydrogen bonding and dipole–dipole interaction in the water. The n→π* donation of N–C═S leads to a stronger interaction between sulfur heteroatom of I and fullerene. In contrast to the previous report on the produced thio-oxindoles in organic solvents, toluene was found to be the best solvent in terms of the highest yield and the shortest reaction time, in this case, adsorption takes place in water with no catalyst addition. Here, we have focused on chemical reaction of I and C20 to produce Ia complex via the optimized TSs in the gas phase, toluene, dichloromethane, methanol, acetonitrile, dimethyl sulfoxide and water, using DFT approach.

Superfast desulfurization for protein chemical synthesis and modification

Superfast desulfurization for protein chemical synthesis and modification

Fisetin and Robinetin antiradical activity under solvent effect: density functional theory study

The structural and antioxidant activity of two flavonols, namely, Fisetin and Robinetin, have been investigated employing the density functional theory (DFT) using B3LYP functional and 6-311++G (d, p) basis set. The calculations were performed in the gas phase and under the solvent effect of water, dimethylsulfoxide (DMSO), methanol, and benzene. The Hydrogen-Atom Transfer (HAT), single Electron Transfer Followed by Proton Transfer (SET-PT), and sequential Proton Loss Electron Transfer (SPLET) mechanisms were investigated to rationalize the radical scavenging capacities and to identify the favored antioxidant mechanism. Hence, the bond dissociation enthalpies (BDE) ionization potential (IP), IE, proton dissociation enthalpy (PDE), proton affinity (PA), and electron Transfer enthalpy (ETE) related to each mechanism were reported and discussed in function of the solvent effect. For both flavonols, the results showed that 4'-OH hydroxyl is the preferred active site following the trend 4'-OH > 3'-OH > 3-OH > (5'-OH) > 7-OH. Besides, the HAT mechanism is energetically the most favored pathway. The energetically favored solvents follow the trends water > DMSO > benzene > methanol and benzene > DMSO > methanol > water, for Fisetin and Robinetin, respectively.

Dual‐Control Mechanism of Water and Temperature in Automatically Programmable Shape Memory Polymers

AbstractAuto‐programmable shape memory polymers (AP‐SMPs) can deform automatically without external manipulation, exhibiting either a free‐standing temporary shape or a permanent shape. The unique shape memory behaviors derive mainly from control by two factors, water and temperature. However, the control mechanism is unknown. This study analyzes and demonstrates the dual‐control mechanism of water and temperature in the three shape‐changing processes of AP‐SMPs. First, the AP‐SMP is immersed in warm water (50 °C). Asymmetric swelling of bilayer films provides the driving force for the shape auto‐programming of the AP‐SMP. The solvent effect of water reduces the glass transition temperature (Tg) of the AP‐SMP, which becomes lower than the medium temperature in warm water. AP‐SMP can be programmed automatically. Then, the AP‐SMP is removed from water and placed in air at room temperature. The Tg value of the matrix film increases notably in air and exceeds the medium temperature. The temporary shape of the AP‐SMP can thus be fixed. Finally, the AP‐SMP can quickly return to its permanent shape when the medium temperature exceeds the matrix film Tg in air. The dual control shape memory mechanism provides insights into the design and development of AP‐SMPs.

Ether-Water Hybrid Electrolyte Contributing to Excellent Mg Ion Storage in Layered Sodium Vanadate.

Magnesium ion batteries have potential for large-scale energy storage. However, the high charge density of Mg2+ ions establishes a strong intercalation energy barrier in host materials, causing sluggish diffusion kinetics and structural degradation. Here, we report that the kinetic and dissolution issues connected to cathode materials can be resolved simultaneously using a tetraethylene glycol dimethyl ether (TEGDME)-water hybrid electrolyte. The lubricating and shielding effect of water solvent could boost the swift transport of Mg2+, contributing to a high diffusion coefficient within the sodium vanadate (NaV8O20·nH2O) cathode. Meanwhile, the organic TEGDME component can coordinate with water to diminish its activity, thus providing the hybrid electrolyte with a broad electrochemical window of 3.9 V. More importantly, the TEGDME preferentially amassed at the interface, leading to a robust cathode electrolyte interface layer that suppresses the dissolution of vanadium species. Consequently, the NaV8O20·nH2O cathode achieved a specific capacity of 351 mAh g-1 at 0.3 A g-1 and a long cycle life of 1000 cycles in this hybrid electrolyte. A mechanism study revealed the reversible interaction of Mg2+ during cycles. This organic water hybrid electrolyte is effective for overcoming the difficulty of multivalent ion storage.

Role of solvent in enhancing the production of butyl levulinate from fructose

The use of alkyl levulinates is growing interest in fuels. Adding n-butyl levulinate (BL) to fuels presents some benefits compared to ethyl levulinate. The conventional production route of BL is from the esterification of levulinic acid, but the latter compound presents some corrosion issues. Alcoholysis of fructose by butanol over cation exchange resins (solid catalyst) seems to be a better alternative. The effect of water addition, solvent, swelling effect (from the cation exchange resin), and fructose solubility at temperatures higher than 25 °C are unclear on this reaction. To understand these effects, the alcoholysis of fructose by butanol at 110 °C in different solvents, e.g., gamma-valerolactone (GVL), were studied in a pressurized autoclave in an inert environment. The dissolution study was conducted in a temperature range of 20–120 °C in different solvents. The concentration profiles of fructose, 5-(hydroxymethyl)furfural (HMF), 5-(butoxymethyl)furfural (BMF) and BL were analyzed in different solvents: butanol/water, butanol, butanol/GVL/water and butanol/GVL. We found that using a butanol/GVL (70/30 wt%) solvent is better from the conversion and dissolution viewpoints.

Combined effect of hot water and deep eutectic solvent (DES) pretreatment on a lignocellulosic biomass mixture for improved saccharification efficiency

The combined effect of hot water (HW) and deep eutectic solvent (DES) on the solubilization of hemicellulose and lignin present in a lignocellulose mixture (rice straw, napier grass, and sugarcane bagasse in a 1:1:1 ratio) was investigated. The selected DES for present study included choline chloride (ChCl) with urea (U), glycerol (G), and lactic acid (LA) at a molar ratio of 1:2 w/w. The selection of different lignocellulosic biomass was made taking into account the similar percentage of hemicellulose and lignin. The hot water and DES pretreatment was performed with biomass loading of 1:10 w/v, 121 °C, 40 min. and 130 °C, 95 min, and 150 rpm, respectively. The HW-ChCl-LA resulted in 4.51-fold increase in cellulose digestibility at 72 h (20.63 ± 0.68% to 93 ± 3.62%). The FTIR spectrum for pretreated solids showed significant changes in the wavelength related to hemicellulose and lignin.

Density Functional Theory Study of Intermolecular Interactions between Amylum and Cellulose

Amylum is one of the polysaccharides developed into biodegradable plastic bags. However, amylum-based plastics are easily damaged due to their low mechanical strength and hydrophilic properties. Cellulose is used as a support material in amylum-based plastics to increase strength and reduce water damage. This study investigated the molecular interactions between amylum and cellulose computationally. The minimum interaction energy of amylum and cellulose was calculated using in silico modeling using the Density Functional Theory (DFT) method. The B3LYP function and the basis set 6-31++g** were used in the calculations. Simultaneously, D3 Grimme dispersion correction was used as the effect of water solvent in the measures. The results obtained from this study were the interaction energy of amylum and cellulose of –29.8 kcal/mol. The HOMO-LUMO energy gap of the cellulose-amylum complex was lower than cellulose, indicating that the cellulose-amylum complex was more reactive and bonded to each other. Analysis of Natural Bond Orbital (NBO), Quantum Theory Atom in Molecule (QTAIM), Reduced Density Gradient (RDG), Non-covalent Interaction Index (NCI), and Intrinsic Bond Strength Index (IBSI) showed that the cellulose-amylum complex had weak to medium intermolecular bonds. The hydrogen bond at O61···H48 was the strongest in the complex. All data show that cellulose and amylum could interact through non-covalent bonds.

Density functional theory study on the initial reactions of d-Xylose and d-Xylulose dehydration to furfural

The mechanism of the initial reactions in the acid-catalytic conversion of d-xylose/d-xylulose to furfural was studied with density functional theory. The reactions included mutual transformations among d-xylose, d-xylulose and the intermediate of 1,2-enediol. The catalytic performances of several acids including H2SO4, HNO3, HCl, HBr and HI, and the solvent effects of water and THF (tetrahydrofuran) were studied. A simplified kinetic model of the d-xylose/d-xylulose-to-furfural conversion in water solvent was built, with the assumption that the conversion from 1,2-enediol to furfural was the rate-limiting step and could be treated as one-step reaction. The simulation can well fit the experimental regulation, which verifies the rationality of the model simplification. The dominant reaction pathways from d-xylose/d-xylulose to furfural were deduced based on the calculated energy barriers and corresponding reaction rate constants, with different acid catalysis and reaction mediums.

A DFT study of the Pb ion adsorption on smithsonite (1 0 1) surface in aqueous system

Understanding the adsorption mechanism of Pb ion on smithsonite surface is crucial for the sulphidation xanthate flotation of smithsonite. In this paper, the adsorption mechanism of Pb ion on smithsonite (101) surface in aqueous system was first investigated by DFT simulation. We further considered the effect of water solvent and analysed the structures of Pb ion hydrates in aqueous system, and finally the [PbOH(H2O)4]+ and Pb(OH)2(H2O)2 were employed as the main solvation components to study the Pb ion adsorption. Then, the adsorption behaviour and bonding mechanism of which on smithsonite surface were studied by analysing the adsorption configurations and electronic properties. We found that the hollow site with an eight-membered ring was the main adsorption site. In addition, H-bond played an important role in the stability of the adsorption configurations of the Pb ion hydrates on smithsonite surface. Moreover, we found that the bonding of Pb-O was mainly attributed to the hybridization of Pb 6s and Pb 6p orbitals with O 2p orbital and hybridization of Pb 5d orbital with O 2s orbital, and the formed PbO bond exhibited some ionic bond characteristic. The obtained adsorption structures corresponded well with the previous experiment.