Different Numbers Of Hydroxyl Groups Research Articles

Regulating Intermolecular Hydrogen Bonds in Organic Cathode Materials to Realize Ultra‐stable, Flexible and Low‐temperature Aqueous Zinc‐organic Batteries

Rational design of molecular structures is one of the effective strategies to obtain high‐performance organic cathode materials. However, besides the optimization of single‐molecule structures, the influence of the "weak" interaction forces (e.g. hydrogen bonds) in organic cathode materials on the performance of batteries should be fully considered. Herein, three organic small molecules with different numbers of hydroxyl groups (namely nitrogen heterocyclic tetraketone (DAB), monohydroxyl nitrogen heterocyclic dione (HDA), dihydroxyl nitrogen heterocyclic dione (DHT)) were selected as the cathodes of aqueous zinc ion batteries (AZIBs), and the effect of the intermolecular hydrogen bonds on their electrochemical performance was studied for the first time. Clearly, the stable hydrogen‐bond networks built through the hydroxyl groups significantly enhance the cycle stability of organic small‐molecule cathodes and facilitate rapid proton conduction between the hydrogen‐bond networks through the Grotthuss mechanism, thereby endowing them with excellent rate performance. In addition, a larger and more dense two‐dimensional hydrogen‐bond network can be constructed through multiple hydroxyl groups, further enhancing the structural stability of organic small‐molecule cathodes, giving them better cycle tolerance, excellent rate performance, and extreme environmental tolerance.

Regulating Intermolecular Hydrogen Bonds in Organic Cathode Materials to Realize Ultra-stable, Flexible and Low-temperature Aqueous Zinc-organic Batteries.

Rational design of molecular structures is one of the effective strategies to obtain high-performance organic cathode materials. However, besides the optimization of single-molecule structures, the influence of the "weak" interaction forces (e.g. hydrogen bonds) in organic cathode materials on the performance of batteries should be fully considered. Herein, three organic small molecules with different numbers of hydroxyl groups (namely nitrogen heterocyclic tetraketone (DAB), monohydroxyl nitrogen heterocyclic dione (HDA), dihydroxyl nitrogen heterocyclic dione (DHT)) were selected as the cathodes of aqueous zinc ion batteries (AZIBs), and the effect of the intermolecular hydrogen bonds on their electrochemical performance was studied for the first time. Clearly, the stable hydrogen-bond networks built through the hydroxyl groups significantly enhance the cycle stability of organic small-molecule cathodes and facilitate rapid proton conduction between the hydrogen-bond networks through the Grotthuss mechanism, thereby endowing them with excellent rate performance. In addition, a larger and more dense two-dimensional hydrogen-bond network can be constructed through multiple hydroxyl groups, further enhancing the structural stability of organic small-molecule cathodes, giving them better cycle tolerance, excellent rate performance, and extreme environmental tolerance.

Enhancing the photoelectrochemical hydrogen evolution activity of polyaniline through small molecular acid doping to introduce polariton-enhanced active sites

Development of organic polymer photoelectrodes with high surface activity is the key to efficient water splitting for hydrogen production. Polyaniline (PANI) prepared under alkaline conditions has semiconducting properties, but high reaction rates are difficult to achieve due to its poor surface activity. In this study, electrochemical doping was used to introduce small molecular acids (2,3-hydroxybutanedioic acid (TA), 2-hydroxybutanedioic acid (MA), and succinic acid (SA)) containing different numbers of hydroxyl groups into the PANI backbone to form polarizers, dipolarizers and active sites. Density Functional Theory (DFT) shows that small molecular acids interact with the imine (=N-) structure of the PANI backbone via electron cloud stacking to form complex active sites. Meanwhile, the transition from polarons to dipolarons under light conditions increases the polarity of the PANI molecular chain, which further improves the photoelectrocatalytic performance. This study will bring new ideas for efficient photoelectrocatalysis based on organic polymers.

New theoretical perspective for easy evaluation of the antioxidant properties of typical flavonoids

To intensively investigate the antioxidant property of flavonoids and their different phenolic hydroxyl groups, we selected six types of typical flavonoids and carried out experimental analysis and quantum chemical calculations. By calculating the Mulliken charges, frontier molecular orbitals, molecular dipole moments, and interaction model hydrogen bond lengths of the compounds, the theoretical analysis results were compared with the free radical scavenging assays. Results show that the three flavonoids with different numbers of hydroxyl groups on the B ring are ranked in antioxidant activity as myricetin > quercetin > kaempferol. The glycoside linked in the C ring has a great effect on bioavailability, and the antioxidant activity is ranked as quercetin > isoquercetin > rutin. Besides, the results of the novel interaction model calculations show that quercetin with an meta-hydroxy group on the B ring structure has stronger antioxidant capacity than morin with an ortho-hydroxy group. The theoretical evaluation method established in this work is expected to provide new ideas and references for the evaluation of antioxidant properties of natural active substances from the electronic structure perspective.

Sugaring-out plus salting-out: A novel separation and purification technique for biofuel

Using fermentation-based alcohol fuel as a substitute for fossil fuels is one of the means to alleviate the oil crisis and exhaust emissions. However, the low fermentation titer and the formation of azeotropes pose challenges to the separation process. In this paper, sugaring-out was proposed to separate a biofuel, namely isobutanol, as sugars are milder than salts and can be used as the fermentation media. The decrease in the water content is a linear function of the initial sugar concentration so that the isobutanol + water azeotrope was broken. The recovery of isobutanol in the 60 wt% isobutanol system using sucrose, glucose, and fructose reached 96.57 %, 97.01 %, and 97.98 %, respectively. After a two-step surgating-out + salting-out process, the isobutanol was purified to 99.82 wt%. The sugaring-out effects of different sugars were quantized by fitting the natural logarithm of isobutanol solubility with sugar molality in the aqueous phase. Due to the different number of hydroxyl groups in the sugar's structure, the order of the sugaring-out effect is glucose ≈ fructose > sucrose. This article provides detailed data on the sugaring-out separation of the concentrated biobutanol systems, which has a guiding role for the use of sugaring-out effect to separate other biofuels from fermentation broth.

Surface functional group nanoarchitectonics of TiO2 nanoparticles for enhanced adsorption Ge(IV)

BackgroundTo compose an effective adsorbent for water purification, surface functional groups have a critical role in determining the adsorption achievement of metal oxide particles. MethodsHerein, the organic acid-functionalized TiO2 nanoparticles were synthesized by modifying TiO2 nanoparticles with organic acids contenting different number of hydroxyl groups. The adjustment of the surface hydroxyl functional groups content of functionalized TiO2 nanoparticles significantly affected the Ge(IV) adsorption capacity. Significant findingsOur results indicate successfully that the obtained tartaric acid (dihydroxysuccinic acid) functionalized TiO2 (TA-TiO2-OH) have more hydroxyl functional groups (up to 4.38 mmol·g−1) and large Ge(IV) adsorption capacity (122.26 mg·g−1) at pH = 3, which are higher than those of the currently reported adsorbents. More importantly, TA-TiO2-OH also has a remarkable affinity for Ge(IV) at a Ge(IV) metallurgical simulated solution.

Assessing the impact of increase in the number of hydroxyl groups on the microscopic behaviors of ammonium-based room temperature ionic liquids: A combined fluorescence up-conversion, fluorescence correlation and NMR spectroscopic study

The current study aims to understand the impact of variation of number of hydroxyl groups on the cationic head of ammonium-based room temperature ionic liquids (RTILs) towards inter/intra molecular hydrogen bonding interaction, local structural organization and dynamics of the solvent systems. For this purpose, three hydroxyl functionalized ammonium based RTILs (HFILs) bearing different numbers of hydroxyl groups on the cationic head as well as a non-hydroxyl ammonium based RTIL have been examined using both ensembled average and single-molecule spectroscopy techniques. Investigation of solvent relaxation dynamics of all the concerned RTILs by the combination of femto-second fluorescence up-conversion techniques and time corelated single photon counting techniques reveals a bimodal solvent relaxation behaviour having a very fast sub-picosecond and a relatively slower picosecond to nanosecond solvation time component for all the RTILs. Interestingly, analysis of the rotational and translational diffusion dynamics of a few particular solutes shows that the solvent–solvent interaction in the poly-hydroxyl-based HFILs is substantially stronger than the solute–solvent interaction. Additionally, analysis of the rotational diffusion data reveals that all RTILs exhibit significant dynamic heterogeneity, which increases with increase the number of hydroxyl groups on the cationic head of HFILs. Moreover, PFG-NMR study have shown that the HFILs had considerably greater hydrodynamic radii than the non-hydroxyl RTILs, which is likely due to the result of stronger hydrogen bonding interaction between the hydroxyl groups and the constituent of the HFILs. The outcomes of all these investigations have essentially demonstrated that subsequent addition of hydroxyl functionalities to the cationic head of the RTILs significantly alter the intra/inter molecular interaction, local structural organisation and heterogeneity of the medium.

Effect of the number of hydroxyl groups of CO2-triggered surfactants on capability and performance in CO2-stimulated response

This paper reports the synthesis and characterization of three CO2-triggered surfactants (S-0, S-2, S-4) containing different number of hydroxyl groups. The impact of the hydroxyl groups on S-0, S-2, and S-4 was investigated by observing the morphological appearance, conductivity, and pH after CO2 bubbling. The surface tension of the three CO2-triggered surfactants decreased from S-0 to S-2 then to S-4, meaning surface tension decreasing with increasing the number of hydroxyl groups. The interfacial tension results showed that surfactants with more hydroxyl groups can better reduce the interfacial tension at a given pH. The pKa and micromorphology results revealed different degree of protonation of the CO2-triggered surfactants by CO2 in water, causing variations in their aggregation patterns. Molecular simulations revealed that increasing the number of hydroxyl groups increases the thickness of the hydration layer. And S-4 with a thicker hydration layer will more likely form a complex network structure than S-0 and S-2 with a thinner hydration layer. The new surfactants utilize a simple and mild approach to synthesis; solving problems such as insolubility and phase separation through the introduction of hydroxyl groups. The study serves as a guide to the application of CO2-trigger surfactant solutions.

Squaraine dye/Ti3C2Tx MXene organic-inorganic hybrids for photocatalytic hydrogen evolution

MXenes, a new family of 2D nanostructured materials, have been widely studied in the field of artificial photosynthesis due to their outstanding physicochemical properties. In this work, a series of 2,4-bis[4-(N,N-dibutylamino)phenyl] squaraine (SQ) derivatives with different number of hydroxyl groups were hybridized with Ti3C2Tx MXene nanosheets, and the organic–inorganic hybrid photocatalysts were applied for water-splitting hydrogen evolution. The mass ratios of SQ@Ti3C2Tx were optimized to 4 wt% for each SQ, and the best hydrogen evolution reaction (HER) rate of 28.6 μmol h−1 g−1 was achieved by SQ-3 with four OH groups. The photocatalytic ability of the hybrid comes from the outstanding light harvesting of SQ dye, sufficient active sites of Ti3C2Tx, and efficient separation and transfer of the photogenerated charges via heterojunction between SQ aggregates and Ti3C2Tx. This work firstly demonstrates an example of SQ sensitizer combined with MXene for hydrogen generation, which provides a new insight to further explore the MXene-based hybrid nanomaterials for water splitting hydrogen evolution.

The Tribological Property of a-C:H Coating with Tribolayer by Additive Having Glycerol and Phosphate Oxide Structure

The tribological properties of a-C:H coating sliding against a SUJ2 ball, a SUJ2 roller, and an a-C:H coated roller were investigated under temperatures ranging from 20 to 80 °C in PAO with different additives. The additives had a glycerol and hydroxyl functional group in one molecule to enhance additive adsorption for mating with the a-C:H coating disk material and to build a phosphorus oxide tribolayer. Additives with different numbers of hydroxyl groups and primary or secondary-type C6H13O structures were also prepared. The tribolayer derived from each additive was analyzed via EDS, XPS, and ToF-SIMS. XPS depth analysis for the tribolayers revealed that additives were dissociated by friction and suggested C–O bond cleavage occurred.Graphical Abstract

Three in one: Rational engineering of multifunctional MIL-101-based ionic catalysts for carbon dioxide-epoxide cycloaddition

CO2-epoxide cycloaddition represents one of most attractive approaches for chemical fixation and utilization of CO2, but highly efficient and fully heterogeneous green catalysis is still challenging. Ionic metal-organic frameworks (IMOFs) are nice porous matrices heterogenizing the essential free nucleophilic anions and meanwhile providing Lewis acids, but the catalytic efficiency has been limited for low anion content and lack of auxiliary catalytic sites. In this work, we report stepwise optimization of IMOF catalysts by integrating multiple catalytic sites into MIL-101. Various monocationic IMOFs with quaternary ammonium and bromide anions were prepared by facile alkyne-azide click chemistry. Different numbers of hydroxyl groups were introduced in this ionization step to optimize the activity. To introduce more anions, dicationic IMOFs were created by a second ionization step, N-quaternization of triazolyl to triazolium. By the stepwise ionization and functionalization, we demonstrated the synergic catalytic effects among different sites, the impacts of hydroxyl/bromide content, and the size effect of the cationic group. The optimal IMOFs are superior to previous ionic heterogeneous catalysts in absence of cocatalysts. In particular, the dicationic catalyst can quantitatively convert epichlorohydrin to the carbonate within 1 h at 1 MPa CO2 and 80 °C, the apparent turnover frequency being up to 478 h−1. The highly active and selective, fully heterogeneous and recyclable catalyst has the appeal for practical applications.

Anti-inflammatory activity of flavonols via inhibiting MAPK and NF-κB signaling pathways in RAW264.7 macrophages

Fisetin (Fis), quercetin (Que), and myricetin (Myr) are flavonols with similar structure but different number of hydroxyl groups. The present research focused on the anti-inflammatory effect of these three flavonols in lipopolysaccharide-stimulated RAW264.7 cells. The number and site of hydroxyl group in flavonols obviously affected their anti-inflammation activity. These flavonols suppressed the overproduction of nitric oxide. Fis showed the best activity with an inhibition rate of 52% at 20 μM. Moreover, the flavonols reduced the levels of ROS, TNF-α, and IL-6. The mechanistic study showed that they inhibited the activation of NF-κB and MAPK pathways by suppressing the phosphorylation of IκBα, p65, JNK, ERK, p38, MEK, and reducing the nuclear translocation of NF-κB p65. In addition, the metabolism of the flavonols was examined. The results indicated that Fis was both methylated and glucuronidated. Que and Myr were mainly transformed into methylated products. This study highlights the anti-inflammatory activity of flavonols, particularly Fis, which has the potential for the prevention or treatment of inflammation as an adjuvant medicine or food additive.

Effect of spacer hydroxyl number on the performance of Gemini cationic viscoelastic surfactant for fracturing fluids

The performance of Gemini cationic viscoelastic surfactant (VES) is affected by the spacer group, which is also the focus for developing the molecular structure design of high -performance clean fracturing fluid. In this study, we synthesized Gemini cationic VESs (VES-O, VES-DO, VES-TO) by introducing different number of hydroxyl groups in the spacer. The effect of the number of hydroxyl groups in the spacer on the performance of Gemini cationic VES was investigated using surface tension measurement, apparent viscosity and viscoelasticity tests in the presence of KCl. Further, the performance of clean fracturing fluids containing VES-O, VES-DO, and VES-TO were evaluated. We discovered that increasing numbers of hydroxyl groups in the spacer improves surfactant performance in fracturing fluid and high-elasticity fracturing fluids with low viscosity. This gives us ideas for future designs of high-performance clean fracturing fluids.

Regulating the type of cobalt porphyrins for synergistic promotion of photoelectrochemical water splitting of BiVO4

Three novel semiconductor composite photoanodes (BiVO4/GO/CoTPP(OH)n, n = 1, 4 and 8) are designed and prepared by decorating BiVO4 with graphene oxide (GO) and cobalt porphyrins bearing different number of hydroxyl groups. The introduction of GO and CoTPP(OH)n onto the BiVO4 surface has been confirmed by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared and Raman spectroscopic techniques, endowing BiVO4 with improved charge transfer and broadened light absorption ability. Their viability as photoelectrochemical system is investigated under AM 1.5 G light irradiation, the photoelectrochemical water splitting performance being found to be dependent on the type of cobalt porphyrins. The BiVO4/GO/CoTPP(OH)4 is found to exhibit the largest photocurrent density of 5.27 mA/cm−2 at 1.23 V vs. RHE due to a combination of mechanisms.

Synthesis of plant oil derived polyols and their effects on the properties of prepared ethyl cellulose composite films

Polyols with different number of hydroxyl groups were synthesized from ricinoleic acid and oleic acid. These plant oil derived polyols can be used as plasticizers and combined with ethyl cellulose (EC) through supramolecular system to prepare ethyl cellulose composite films. The morphology, thermal stability and mechanical properties of the prepared ethyl cellulose films were studied in detail to indicate the plasticizing efficiency of these polyols and the effect of the number of hydroxyl groups in polyols on EC composite film’s properties. With the addition of polyols, the tensile strength of EC composite films decreased, while the elongation at break increased. The elongation at break of EC composite films can be improved by 11–12 times when the polyols contain 1–3 hydroxyl groups. Thus, the plant oil derived polyols with 1–3 hydroxyl groups can be used as plasticizers for EC films. In addition, molecular dynamic simulations were performed to further probe the effects of the number of hydroxyl groups in polyols on EC composite film’s properties.

Molecular Weight Distribution of Two Types of Living Chains Formed during Nitroxide-Mediated Polymerization of Styrene.

Different types of polymer chains generated during the nitroxide-mediated polymerization of styrene are separated for the first time, and their molecular weight distribution (MWD) is investigated. Living and dead chains are monitored during the reaction; specifically, two types of living chains derived from the initiation of the alkoxyamine (RT) and the self-initiation of styrene and dead chains present in the as-prepared polystyrene (PS). To distinguish between each polymer species, different numbers of hydroxyl groups are introduced onto the T and R groups of the alkoxyamine (one and two groups, respectively). Each living and dead chains is resolved according to the distinct number of hydroxyl groups on its chain-end using high-performance liquid chromatography. Molecular structures of the fractionated PS are characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 1 H nuclear magnetic resonance spectroscopy, and the results of which show two distinct initiation paths: one originating from RT and the other from the self-initiation of styrene. Molecular weight and MWD are measured using size-exclusion chromatography and reveal a narrow MWD for the living chains derived from RT. Contrastingly, a broad and skewed MWD is observed for the other living chains derived from the self-initiation of styrene and the dead chains.

Three-dimensional porous carbon derived from different organic acid salts for application in electrochemical sensing.

Three-dimensional porous carbon materials were synthesized by the one-step pyrolysis of organic salts with different numbers of hydroxyl groups on the side chain (sodium tartrate, sodium malate and sodium succinate). Further, the formation of these porous carbon materials was explored. And then, three kinds of carbon materials were used for constructing electrochemical sensors for nitrite detection, respectively. Porous carbon derived from sodium tartrate (PCST) showed the highest electrocatalytic ability for nitrite oxidation among all three materials. The PCST-based sensors allow for rapid detection of nitrite in a wide linear range of 0.1–100 μM with a low detection limit of 0.043 μM. The sensor was applied to detect nitrite in meat samples and the results tested by the developed sensor were consistent with the results obtained by HPLC. We envision that PCST-based electrochemical sensor is promising as an alternative choice for the development of electrochemical analysis.

Effect of dispersing media and temperature on inter-yarn frictional properties of Kevlar fabrics impregnated with shear thickening fluid

Shear thickening fluid (STF) treated Kevlar fabrics is a potential method to improve the stab resistance of flexible body armors, whereas the STFs were significantly influenced by the temperature during their practical application. In this study, four kinds of STFs were prepared using constant silica and various dispersing media with different number of hydroxyl groups and chain length. The steady state and dynamic rheological properties of STFs were investigated in the temperature range of 20 to 50 °C. The pull-out test of the STF/Kevlar fabrics were also studied at different speeds and temperatures to evaluate the contribution of shear thickening effect. The results indicated that the STF/Kevlar fabrics had higher inter-yarn friction than the neat fabrics, suggesting a correlation of shear thickening effect. At 50 °C, the STFs with more hydroxyl groups and longer chains could reduce the negative effect of elevated temperature on the inter-yarn friction from 88.94% to 49.23%. Therefore, according to the different environment temperature, it is necessary to choose suitable dispersing medium to design application-specific of STFs.

Synthesis and characterization of starch sulfates obtained by the sulfamic acid-urea complex

The process of sulfation of starch with sulfamic acid in the presence of urea was studied. The sulfur content of starch sulfate increases with increasing sulfation temperature from 70 to 100 °C. To obtain starch sulfates with a high sulfur content (about 10 wt%), It is advisable to carry out the sulfation process at a temperature of 100 °C for 120 min. Mathematical modeling of the process of sulfation of starch with sulfamic acid in the presence of urea was carried out. The introduction of a sulfate group in the structure of starch is confirmed by FTIR spectroscopy. In the FTIR spectra of sulfated starch, in contrast to the original starch, there are absorption bands at 1255 cm−1, 808-817 cm−1 and 859-867 cm−1, corresponding to sulfate groups. Sulfation of starch with a complex of sulfamic acid - urea can improve the environmental safety and efficiency of the process in comparison with the known methods of sulfation. Initial starch and sulfated starch were analyzed by gel permeation chromatography. The initial starch was shown to have a main peak with Mn 139 kDa and Mw 382 kDa, and sulfated starch has a peak in the chromatogram relating to Mn 44 kDa and Mw 60 kDa. Besides, the quantum chemical calculations of the starch and sulfated starches (in dimer forms) formed when different number of hydroxyl groups in starch were replaced with sulfate groups were performed using the DFT/B3LYP method with 6-31+G (d, p) basis set in the ground state. Firstly, these molecules were optimized. Then, from the optimized geometry of the starch and sulfated starches, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) surfaces, bond parameters, chemical reactivity descriptors such as chemical potential, electron affinity, electronegativity, ionization energy, electrophilicity index and chemical hardness have been calculated theoretically. In addition, spectroscopic analyzes of starch and sulfated starches such as FTIR and 1H NMR were theoretically performed using the same method and compared with each other.

Application of linear solvation energy relationships and principal component analysis methods for the prediction of the retention behaviour of E-resveratrol analogues with substituted silica hydride stationary phases

In this investigation, application of linear solvent energy relationships (LSERs) and principal component analysis (PCA) methods have been employed to investigate the structure-retention dependencies of E-resveratrol analogues separated under different stationary and mobile phase conditions. To this end, the retention of 22 analogues have been determined with phenyl, diol, bidentate anchored C18 (BDC18) and Diamond Hydride™ C18 (DHC18) substituted silica hydride stationary phases under isocratic chromatographic conditions using mobile phases containing 0.1 (% v/v) formic acid and different acetonitrile or methanol contents from 10 to 90% (v/v) in 10% increments. In general, these compounds showed decreasing retention with increased acetonitrile or methanol content in the mobile phase with all the stationary phases. The retention order generally followed their log P values, although some unique selectivity variations were apparent depending on the nature of the selected stationary and mobile phases. These 22 compounds contained different backbone functionalities linking the phenyl ring A to phenyl ring B and different numbers of hydroxyl groups in the phenyl ring A/phenyl ring B. Structure-retention descriptors, derived according to LSER concepts, were analysed by PCA methods to provide group classification of these resveratrol analogues from the associated PC1 versus PC2 score plots. These results revealed that the selectivity of these compounds was dominated by hydrophobic and steric interactions. Based on the number and position of hydroxyl groups in a specific resveratrol analogue, a reliable curve fitting approach (indicated by R2 > 0.99 for the correlation between experimental and predicted log k values) was derived for prediction of the retention of these analytes under different mobile phase isocratic separation conditions. The application of similar methods are anticipated to find general utility for the analysis of diverse classes of other low molecular mass compounds in the different modes of liquid chromatography, permitting enhanced levels of prediction and evaluation of the retention attributes of polar and non-polar compounds.