OH Hydrogen Research Articles

Cooperativity in alkane-1,2- and 1,3-polyols: NMR, QTAIM, and IQA study of O─H… OH and C─H… OH bonding interactions.

Proton nuclear magnetic resonance chemical shifts and atom-atom interaction energies for alkanepolyols with 1,2-diol and 1,3-diol repeat units, and for their 1:1 pyridine complexes, are computed by density functional theory calculations. In the 1,3-polyols, based on a tG'Gg' repeat unit, the only important intramolecular hydrogen bonding interactions are O─H… OH. By quantum theory of atoms in molecules analysis of the electron density, unstable bond and ring critical points are found for such interactions in 1,2-polyols with tG'g repeat units, from butane-1,2,3,4-tetrol onwards and in their pyridine complexes from propane-1,2,3-triol onwards. Several features (OH proton shifts and charges, and interaction energies computed by the interacting quantum atoms approach) are used to monitor the dependence of cooperativity on chain length: This is much less regular in 1,2-polyols than in 1,3-polyols and by most criteria has a higher damping factor. Well defined C─H… OH interactions are found in butane-1,2,3,4-tetrol and higher members of the 1,2-polyol series, as well as in their pyridine complexes: There is no evidence for cooperativity with O─H… OH bonding. For the 1,2-polyols, there is a tenuous empirical relationship between the existence of a bond critical point for O─H… OH hydrogen bonding and the interaction energies of competing exchange channels, but the primary/secondary ratio is always less than unity.

Ion Pairs of 1-Butyl-3-Methylimidazolium Triflate Do Not Dissociate in Propan-1-ol: A Vibrational Spectroscopic Viewpoint

Adding imidazolium ionic liquids to polar solvents such as alkyl alcohols usually results in the dissociation of ion pairs as cation–anion interactions are replaced, e.g., by ion⋯OH hydrogen bonds. In this Communication, we apply Raman scattering and infrared absorption spectroscopy to an example binary system comprising 1-butyl-3-methylimidazolium trifluoromethanesulfonate (triflate) and propan-1-ol. The spectra are analyzed using principal component analysis (PCA), excess spectroscopy, and spectral decomposition. The results provide evidence that the ion pairs of the ionic liquid do not dissociate in propan-1-ol, even at high dilution. Moreover, there are clear signs that the propan-1-ol hydrogen bonding network is disrupted in the presence of the ionic liquid as the hydroxyl groups predominantly interact with the sulfonate oxygen atoms.

Solid-Solution Alloying of Immiscible Pt and AU Boosts Catalytic Performance for H2o2 Direct Synthesis

In the field of bimetallic catalysis, combinations of immiscible elements have been very limited. Here, we propose the solid-solution alloy nanoparticles (NPs) composed of Pt and Au supported on TiO 2 as an efficient catalyst for direct H 2 O 2 synthesis, although Pt and Au are entirely immiscible in the bulk phases. Pt and Au atoms were homogeneously distributed in a wide composition range of Pt x Au 100-x NPs (10≤x≤80) supported on TiO 2 . The most Au-rich Pt 10 Au 90 NPs/TiO 2 exhibits the best catalytic performances, H 2 O 2 selectivity (94.5±0.6%) and productivity (959±12 mmol H2O2 •g metal -1 •h -1 ), even under mild conditions (10 °C, 1 atm) and without halide-ion additives. Density functional theory calculations reveal that the introduction of inactive Au atoms strongly suppresses both O-O bond scission and OH hydrogenation, thereby enabling near unity selectivity. This work will stimulate active utilization of the overlooked class of immiscible elemental combinations for catalyst development.

Molecular Nitrogen as an Extraordinary Accelerator for Hydrodeoxygenation

Molecular nitrogen (N2) has been long believed to be an inert gas. Recently in Nature Catalysis, Duan et al. reported that N2 could dramatically promote the catalytic performance of hydrodeoxygenation over ruthenium-based catalysts and that as-formed hydrogenated nitrogen species contributed to the reduction of the activation energy required for carbon-oxygen bond cleavage inside p-cresol.

Linking pore scale mechanisms with macroscopic to core scale effects in controlled ionic composition low salinity waterflooding processes

The controlled ionic composition low salinity waterflooding processes through tuning of salinity and ionic composition are lately becoming popular for oil recovery in carbonates. Most of the experimental work reported in this area has been limited to macroscopic and core scale measurements and these results consensually pointed out wettability alteration towards water-wet state to be the main recovery mechanism. It is widely believed that wettability is the macroscopic to core scale effect and the link between such effects with molecular scale interactions and phenomena occurring at both carbonate-oil/brine and oil-brine interfaces is not yet well understood. The current study aims to address this knowledge gap by acquiring data on various crude oil/brine/carbonate and crude oil-brine physicochemical interactions using several macroscopic, pore, and core scale experimental techniques. These techniques include contact angle, zeta potential, cryo-broad ion beam scanning electron microscope (BIB-SEM), sum frequency generation (SFG) spectroscopy, and core flooding relative permeabilities. Both high salinity water (HSW) and a controlled ionic composition low salinity water (CICLSW) containing sufficient amount of three key ions (sulfates, magnesium, and calcium) are used to delineate water chemistry effects on resulting physicochemical interactions and changes occurring at carbonate-oil/brine and oil-brine interfaces.The macroscopic contact angle data showed strongly oil-wet behavior with HSW and favorable wettability alterations towards water-wet conditions with CICLSW. The opposing polarity of zeta potentials is observed at calcite/brine and oil-brine interfaces with HSW, which can collapse the thin water film and cause the direct contact of crude oil on to the rock surface to result in oil-wetness. In contrast, CICLSW showed increasingly negative zeta potentials at oil/brine interface and the polarity reversal to negative zeta potentials across calcite/brine interface to stabilize the water-film on the rock surface and subsequently render water-wet conditions. The cryo-BIB-SEM imaging showed trapping of oil ganglia in larger pores and relatively less contact of crude oil with carbonate surface for CICLSW flooded sample. The phase distributions in the sample further confirmed less amount of oil trapped in carbonate pores, which provides a clear indication of CICLSW effect on wettability alteration and better oil mobilization in carbonates. It is also understood from sum frequency generation spectroscopy CH3/CH2 stretching results that CICLSW increased the conformation order of hydrocarbon chains to enhance the interactions at thin interfaces and ultimately alter the wettability. Significant increase in the intensities of free OH stretches and hydrogen bonding are observed at oil/water interface with CICLSW. Such result provides a direct indication that dissolved salt ions displace some water molecules at the interface, resulting in reduced free OH bond densities to correlate well with zeta potential drop observed in HSW. The shifts in relative permeability curves obtained by history matching the coreflood experimental data also confirmed the favorable effect of CICLSW in altering the wettability towards water-wet conditions. This study thereby establishes a good agreement between macroscopic to core scale effects and pore scale interactions occurring at carbonate-oil/brine and oil-brine interfaces to clearly demonstrate the beneficial effects of CICLSW on wettability alteration and oil recovery in carbonates.

Optically Induced Rapid Wetting Transition on Zn-Polar and O-Polar Zinc Oxide.

The design and fabrication of surfaces that support rapid wetting transition remain technologically challenging. Here, we examine the effects of optical illumination on the wetting behaviors of zinc oxide (ZnO) single crystals. We find that ultraviolet irradiation above the band gap energy promotes a rapid wetting transition, characterized by sliding of the water droplet, within a few seconds. Notably, the transition for Zn-polar (0001) ZnO surfaces is even faster than that for O-polar (0001̅) ZnO surfaces. We confirmed that process is dependent on power, surface polarity, and solution pH and reversible through illumination by near-infrared light, which restores the water contact angle back to its initial value. Surface chemical analysis revealed that the instantaneous photocatalytic formation of surface-terminated hydroxyl (-OH) groups is responsible for the observed rapid wetting transition. Density functional theory calculations with the inclusion of onsite Coulomb interactions revealed that both the Zn-polar and O-polar surfaces can be easily covered with -OH groups through the adsorption of -OH groups or hydrogen atoms, respectively. This study develops a route to fabricate optically active and controllable microfluidic devices that support rapid wetting transitions for water droplet manipulation.

A highly stable, luminescent and layered zinc(II)-MOF: Iron(III)/copper(II) dual sensing and guest-assisted exfoliation

A highly stable and luminescent metal-organic framework (LMOF) with layered structure, namely, C6H4N5OZn (1) has been successfully achieved and fully characterized by single crystal X-ray diffraction, powder X-ray diffractions, fluorescence titration and thermogravimetry. This blue-light emitting compound 1 exhibit outstanding stability and can detect Fe3+ and Cu2+ in water specifically, presenting potential application in the field of fluorescent probe technology. Fluorescence titration experiments indicate that the detection of Fe3+ ions by 1 is more significant than that of Cu2+ ions in terms of Ksv value. Furthermore, guest-assisted exfoliation of layered MOF 1 is efficiently carried out through ether OH hydrogen bond or π···π interactions between the layered host structure and intercalated guest molecules (4,4′-oxybisbenzoic acid and triphenylamine). Tyndal scattering was observed in the suspensions of obtained MOF nanosheets. This study shows that the compound 1 with unique metal ion sensing properties can be applied as a probe material in water pollution treatment field, but also opens up the opportunity for synthesizing luminescent MONs through the “bottom-up” guest intercalation methodology.

Effects of humidity on room disinfection by dielectric barrier discharge plasma

Atmospheric pressure plasma is one of the most promising low-temperature methods for room sterilization. In this study, we demonstrate that plasma with a circulation system can disinfect the entire space in a laboratory chamber with very high uniformity. We also prove that humidity can accelerate the disinfecting power of plasma by generating active species from water molecules as well as delivering them through water vapor. Compared to low humidity (20%–50%) conditions, at high humidities (70%–90%), the quantities of plasma generated reactive species, specifically OH radicals and hydrogen peroxide, are increased two-fold while the quantity of generated ozone is halved. Ultraviolet irradiation of the plasma further reduces the amount of environmentally harmful ozone. Using an atmospheric pressure non-thermal plasma device, room disinfection and the eradication drug resistant Staphylococcus aureus were successfully achieved.

Taming heterogeneous rhenium catalysis for the production of biomass-derived chemicals

Rhenium is one of important components for heterogeneous catalysts, which has been recently used for the catalytic reactions related to the production of biomass-derived chemicals such as deoxydehydration of vicinal OH groups, C-O hydrogenolysis, and hydrogenation of carboxylic acids, and so on. Suitable oxidation state of Re as a catalytic active species is strongly dependent on the catalytic reactions. The control of the oxidation state of Re species on the catalysts is crucial on the catalyst development.

Chloride capture using a C-H hydrogen-bonding cage.

Tight binding and high selectivity are hallmarks of biomolecular recognition. Achieving these behaviors with synthetic receptors has usually been associated with OH and NH hydrogen bonding. Contrary to this conventional wisdom, we designed a chloride-selective receptor in the form of a cryptand-like cage using only CH hydrogen bonding. Crystallography showed chloride stabilized by six short 2.7-angstrom hydrogen bonds originating from the cage's six 1,2,3-triazoles. Attomolar affinity (1017 M-1) was determined using liquid-liquid extractions of chloride from water into nonpolar dichloromethane solvents. Controls verified the additional role of triazoles in rigidifying the three-dimensional structure to effect recognition affinity and selectivity: Cl- > Br- > NO3 - > I- This cage shows anti-Hofmeister salt extraction and corrosion inhibition.

Kinetic and mechanistic insight into the OH[rad]–initiated atmospheric oxidation of 2,3,7,8-tetrachlorodibenzo-p-dioxin via OH[rad]–addition and hydrogen abstraction pathways: A theoretical investigation

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic polychlorinated dibenzo-p-dioxin. The OH–initiated oxidation of TCDD has been studied using the density functional, canonical transition state, and canonical Rice-Ramsperger-Kassel-Marcus theories. The kinetic data were corrected for quantum tunneling by the Wigner and Eckart models. All OH addition and hydrogen atom abstraction channels were thermodynamically exergonic. The kinetic and thermodynamic data analysis at the reliable level MPWB1K/MG3S//M06-2X/MG3S indicate that the addition of OH to the carbon atom adjacent to the oxygen atom in dioxin ring leads to the formation of predominant adduct. The calculated bimolecular rate constant for the formation of predominant adduct was ~5.97–6.75 × 10−13 cm3 molecule−1 s−1, its branching ratio was ~0.955, and the overall rate constant for the OH–initiated oxidation of TCDD was ~6.25–7.08 × 10−13 cm3 molecule−1 s−1. The atmospheric lifetime of TCDD determined by OH was ~8.17–9.26 days indicating the TCDD can be categorized as medium lifetime organic pollutant.

Superstrong Noncovalent Interface between Melamine and Graphene Oxide.

There have been growing academic interests in the study of strong organic molecule-graphene [or graphene oxide (GO)] systems, owing to their essential noncovalent nature and the consequent chemomechanical behavior within the interface. A more recent experimental measurement [ Chem 2018, 4, 896-910] reported that the melamine-GO interface exhibits a remarkable noncovalent binding strength up to ∼1 nN, even comparable with typical covalent bonds. But the poor understanding on the complex noncovalent nature in particular makes it challenging to unveil the mystery of this high-performance interface. Herein, we carry out first-principles calculations to investigate the atomistic origin of ultrastrong noncovalent interaction between the melamine molecule and the GO sheet, as well as the chemomechanical synergy in interfacial behavior. The anomalous O-H···N hydrogen bonding, formed between the triazine moiety of melamine and the -OH in GO, is found cooperatively enhanced by the pin-like NH2-π interaction, which is responsible for the strong interface. Following static pulling simulations validates the 1 nN level rupture strength and the contribution of each noncovalent interaction within the interface. Moreover, our results show that the -OH hydrogen bonding will mainly augment the interfacial adhesion strength, whereas the -NH2 group cooperating with the -OH hydrogen bonding and conjugating with the GO surface will greatly improve the interfacial shear performance. Our work deepens the understanding on the chemomechanical behaviors within the noncovalent interface, which is expected to provide new potential strategies in designing high-performance graphene-based artificial nacreous materials.

Synthesis and testing of cellulose acetate nicotinate as adsorbent for rhodamine B dye

ABSTRACTThe esterification of cellulose hydroxyl groups with natural carboxylic acids in mild conditions represents an adequate pathway in obtaining cellulose derivatives with different useful properties. In this article, authors report the synthesis of new mixed ester of cellulose and cellulose acetate nicotinate (CAN) , in a homogenous medium using DMF as solvent, cellulose acetate (CA) as starting cellulosic material, and nicotinic acid as an esterification agent in the presence of p‐toluenesulfonyl chloride and pyridine. FTIR and NMR techniques were used to prove the binding of nicotinoyl group at free hydroxyl groups of CA. The obtained CAN was electrospun by electrospinning technique to obtain adsorbent ultrafine fibers, evidenced by SEM images, with high specific surface area. Monolayer Langmuir and empirical Leundrich isotherms were used to assess the adsorption capacity for rhodamine B dye of electrospun CAN in comparison with that of electrospun CA used as starting material. Langmuir isotherm led to a better assessment of experimental data suggesting that the adsorption is mainly determined by hydrogen bonds formed between carboxylic OH hydrogen bonding donor and pyridine N hydrogen bonding acceptor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47772.

Adsorption and dissociation of H2O molecule on the doped monolayer MoS2 with B/Si

Adsorption and dissociation of H2O on monolayer MoS2 surface doped with B/Si explored by first principle calculations coupled with climb image nudged elastic band method. The impurity B/Si atoms are more likely to occupy sulfur atom lattice positions with lower formation energies, which results in the breaking of surface chemically inertness of the MoS2 (001) plane. Free H2O molecules can be adsorbed on doped surfaces with lower adsorption energies, and form chemical bonds between oxygen and impurity atoms. Adsorbed H2O can be separated into OH radical and hydrogen adatom with a lower dissociation energy barrier on these doped systems (including impurity B/Si single doped, B and Si co-doped). Furthermore, the adsorbed OH radical can be further dissociated into oxygen and hydrogen adatoms on the surface of B and Si co-doped MoS2. Our theoretical study suggests that substrate of monolayer MoS2 doped with impurity B, Si may be a potential alternative choice for hydrogen evolution reaction.

The RGD tripeptide anticancer drug carrier: DFT computations and molecular dynamics simulations

The density functional theory (DFT) computations at B3LYP/6-31+G(d,p) level of theory was accomplished in water solvent to investigate the properties of twenty drug delivery systems formed between the tripeptide arginyl-glycyl-aspartic acid (RGD) carrier and the commercially well-known cyclophosphamide (CP) anticancer drug. The CP-RGD-7 produced by the hydrogen bond between phosphoryl (PO) oxygen atom of cyclophosphamide and OH hydrogen atom of RGD had the most negative binding energy. The dipole moments of CP and RGD were close to 8 Debye and this value was increased to 11.403, 7.5398, 14.946 and 10.321 in structures 1, 6, 7 and 8, respectively, demonstrating water (1.85 Debye) with high polarity and non-toxicity, is an appropriate solvent for delivery of such polar CP-RGD systems. The HOMO orbital in all CP-RGD systems was positioned on the cyclophosphamide but the LUMO orbital was dispersed on the tripeptide. Between CP-RGD-7 and CP-RGD-8 having the least binding energy values, CP-RGD-8 exhibited smaller values of chemical potential, energy gap and hardness but the greatest electronegativity and electrophilicity index that certified this structure had greater affinity for binding onto the cancerous tissue. Accordingly, it was established that among all CP-RGD systems, the CP-RGD-8 was the most promising system for the cancer treatment. Considering the molecular dynamics (MD) simulations results obtained at two temperatures (25 and 37 °C), the CP-3RGD was chosen as the most suitable system due to it exhibited desirable drug loading capacity and slow release rate.

Structural, vibrational, Hirshfeld surfaces and optical studies of nonlinear optical organic imidazolium L-tartrate single crystal

Imidazolium L-tartrate (IMLT) single crystal was grown using solution growth technique. The grown crystal belongs to monoclinic crystal structure with space group P21. Intermolecular interactions of IMLT is executed by the Hirshfeld surface analysis. The structure of the grown crystal was stabilized by an extensive network of OH⋯O, NH⋯O and OH hydrogen bonds. The vibrational modes are assigned based on potential energy distribution (PED). 13C and 1H NMR spectra were recorded to interpret the environment of the molecular structure. The HOMO-LUMO energy gap shows that the molecular chemical stability is high for the IMLT molecule. The Mulliken charge distribution confirms that the highest value is noted in C17, whereas the lowest value is obtained in C10 atom. The natural bond orbital (NBO) analysis has been computed to find out the electron delocalization and conjugative interactions. The bonding and anti-bonding orbitals are performed using density of states (DOS) spectrum. From photoconductivity measurement, the dark current is seen to be less than photocurrent. The etching analysis was done on (0 0 1) plane of IMLT crystal and rectangular etch pits are observed.

Radiation-induced loss of silica optical fibres with fluorine-doped cladding

The effect of gamma-irradiation of the fluorine-doped silica depressed cladding graded-index fibre (DCGIF) has been researched. New mechanism of the non-bridging oxygen hole centers (NBOHC) defect formation, conditioned by different mobility of diffusion counter flows of fluorine and oxygen at the core-cladding interface, has been proposed. Using silica tubes with 0.02 wt% of OH groups and hydrogen in free state in MCVD-technology of DCGIF fabrication completely eliminates the NBOHC absorption at the wavelength of 630 nm. However, gamma-irradiation of such fibres results in anomalously high attenuation level in the visible range of optical spectrum. It was established that irradiation of DCGIF leads to light scattering which is probably due to the appearance of optical inhomogeneities in the glass matrix.

Theoretical and Kinetic Properties of OH Radical-Initiated Oxidation of Galaxolide in the Atmosphere.

Galaxolide (HHCB), an important emerging contaminant, has attracted great environmental concern owing to its widespread occurrence and potential toxicity. In this study, the detailed multichannel mechanism of OH radical-initiated atmospheric degradation reactions of HHCB has been investigated by employing density functional theory (DFT). The reactants, transition states, intermediates, and products were optimized at the MPWB1K/6-31+G(d,p) level, and single-point energies were further refined at the MPWB1K/6-311+G(3df,2p) level of theory. The canonical variational transition-state (CVT) theory combined with the small curvature tunneling (SCT) was performed to evaluate the Arrhenius expressions and rate constants of key elementary reactions over a suitable range of 180-370 K. The thermodynamic and kinetic calculation results show that OH addition and hydrogen abstraction reactions are competitive pathways for HHCB. The dominant products in the presence of O2/NO are epoxide, dialdehyde, alcohol ketone, cyclolactone compounds, and HO2 radicals. At 298 K, the total rate constant of OH-initiated degradation of HHCB is 2.71 × 10-11 cm3 molecule-1 s-1. The atmospheric lifetime of HHCB determined by OH-initiated reactions is 10.09 h, which is in favor of the phenomenon of medium-range transport for HHCB in the atmosphere.

Insights on structural characteristic of Xilinguole lignite chars from low-temperature pyrolysis

The cleavage behavior of covalent bonds in Xilinguole (XLGL) lignite and changes in chemical structure of lignite and its chars during low-temperature pyrolysis were investigated by thermogravimetric (TG) analysis and Fourier-transform infrared (FTIR) spectroscopy. Based on the TG and differential thermogravimetric (DTG) analysis results, the cleavage of different types of chemical bonds in lignite occurred mainly at four certain temperatures, 170 °C, 376 °C, 432 °C, and 521 °C. The latter three were selected as the final pyrolysis temperatures of chars evaluated in this study. The FTIR analysis results indicate that thermal treatment increased the relative content of two and three adjacent H deformation structures but decreased that of four adjacent H deformation structure. This was caused by the cleavage of Cal–Cal and Car–Cal bonds. The oxygen-containing functional groups in lignite are dominated by C–O and C–OH groups with a lower chemical reactivity than C=O–C and conjugated C=O groups. Moreover, XLGL lignite has the highest ratio of CH2/CH3 which declines with increasing temperature, indicating the decrease in the length of aliphatic chains and increase in the degree of branching of aliphatic side chains. This change mainly resulted from the cleavage of Cal–O, Cal–Cal, and Car–Cal bonds. Furthermore, XLGL lignite and its chars contain five specific hydrogen bonds: OH–N, cyclic OH, OH–ether O, OH–OH, and OH–π hydrogen bonds. The relative content of OH–OH hydrogen bond was the highest, indicating that OH–OH hydrogen bond has the highest thermal stability.

Preparation of a 1:1.5 cocrystal of kaempferol with 4,4′-bipyridine based on analyzing intermolecular interaction of building units

Based on analyzing intermolecular interaction in building unit of cocrystal of quercetin with 4,4′-bipyridine (QUE·BPY) reported by us on before, a new cocrystal of kaempferol with 4,4′-bipyridine (KAE·BPY) has been designed and synthesized. Within the reported QUE·BPY, 3′OH was neither involved in the formation of the building unit nor played a big role in the 2D layer. Consequently, we boldly speculate kaempferol without 3′OH might crystallize with 4,4′-bipyridine to form similar structure to QUE·BPY. Just as expected, structural analysis shows kaempferol molecules and 4,4′-bipyridine molecules alternate connect to form the building units through 7-OH and 4′OH hydrogen bonds, the structure of KAE·BPY is similar to QUE·BPY. This work proves that new cocrystals could be designed and synthetized by analyzing the intermolecular interaction in building unit and seeking right structure of Active Pharmaceutical Ingredients (APIs). Additionally, the cocrystal of kaempferol with 4,4′-bipyridine shows advantages in terms of hygroscopic stability in comparison to pure kaempferol.