Influence Of Hydroxylation Research Articles

Study of Surface Chemistry, Temperature and Strain Rate on the Tensile Properties of Monolayer Graphene Oxide

The mechanical properties of graphene oxide (GO) during tensile fracture were studied using molecular dynamics methods, and the influence of hydroxyl and epoxy groups on the mechanical properties of GO was explored. In addition, the changes in mechanical properties of GO under different temperatures and strain rates were studied to gain a deeper understanding of its mechanical behavior. The results indicate that hydroxyl and epoxy groups have a significant influence on the elastic modulus, ultimate stress, and ultimate strain of GO. The presence of hydroxyl and epoxy groups can alter the molecular structure of GO, thereby affecting its ultimate stress and strain. When the number of hydroxyl groups is 16 and the number of epoxy groups is 20, the ultimate stress decreases by about 31% and the elastic modulus decreases by about 20%. The variation of elastic modulus, ultimate stress, and ultimate strain of GO with temperature was studied at three temperatures: 300[Formula: see text]K, 500[Formula: see text]K, and 800[Formula: see text]K. As the temperature increases, the amplitude of atomic vibration increases and internal defects and cracks in GO continue to form and expand. At the same time, its coefficient of thermal expansion also increases, causing deformation and loosening of the crystal structure, resulting in a decrease of about 10% in the ultimate stress of GO, and a slight decrease in the ultimate strain and elastic modulus. Finally, the influence of different strain rates on the mechanical properties of GO was studied. As the strain rate increases, the intermolecular interactions within GO are rapidly altered, and the previously loose structure gradually becomes tightly ordered, resulting in an increasing trend in the elastic modulus, ultimate stress, and ultimate strain of GO.

Electronic properties of single-layer CoO2/Au(111)

We report direct measurements via angle-resolved photoemission spectroscopy (ARPES) of the electronic dispersion of single-layer (SL) CoO2. The Fermi contour consists of a large hole pocket centered at the point. To interpret the ARPES results, we use density functional theory (DFT) in combination with the multi-orbital Gutzwiller Approximation (DFT+GA), basing our calculations on crystalline structure parameters derived from x-ray photoelectron diffraction and low-energy electron diffraction. Our calculations are in good agreement with the measured dispersion. We conclude that the material is a moderately correlated metal. We also discuss substrate effects, and the influence of hydroxylation on the CoO2 SL electronic structure.

The effects of hydroxyl by water addition on the photoluminescence of zero-dimensional perovskites Cs4PbBr6 nanocrystals

To investigate the effect of hydroxyl on the photoluminescence (PL) of zero-dimensional perovskite Cs4PbBr6, the Cs4PbBr6 nanocrystals (NCs) were prepared by solution method, and the influence of hydroxyl on the green emission of Cs4PbBr6 NCs was considered. The experiment results show that the green emission of Cs4PbBr6 displays a certain change by adding different amounts of water, NaOH water solution, and absolute ethyl alcohol. The pure Cs4PbBr6 NCs do not show green emission. After water added, CsPbBr3 NCs were observed and not considered to be the main reason for the green emission. Moreover, the hydroxyl of different degrees polarization has an apparent influence on the PL of Cs4PbBr6, which is believed the origin of the green emission. This effect can be explained by hydroxyl caused defect energy level in Cs4PbBr6.

The deposition of metal nanoparticles on carbon surfaces: the role of specific functional groups.

The enormous complexity of a typical heterogeneous catalyst makes understanding the development and properties of any active nanoparticles present extremely challenging. In the case of carbon based catalysts that difficulty is compounded by the variability of the carbon powders used. We have previously developed a strategy that addresses these problems by mimicking the catalyst preparation conditions very closely but using highly ordered pyrolytic graphite crystals (HOPG) as a model surface. This enables us to examine the effects of specific functional groups on nanoparticle formation. We report here an extension of our work characterising functional groups on the HOPG surface, using XPS and AFM to explore the deposition of gold from aqueous solution onto HOPG surfaces treated in a variety of ways to alter the surface functionality. The structure and oxidation state of the resulting nanoparticles depend critically on the nature of the functional groups present and offers some insight into the development of catalysts based on these materials. Hydroxyls are identified as key functional species, reducing gold ions to their metallic state whilst being oxidised themselves to carbonyls. Carbonyls meanwhile promote the nucleation of Au3+, creating a network of islands at the HOPG surface. The results have relevance not only to catalysts using activated carbons but also the new generation of materials based on graphene and carbon nanotubes.

Influence of Hydroxyl and Carboxyl Functionalized Multi-Walled Carbon Nanotube and Filler Loading on the Tensile Properties of Epoxy Composites

In this study, three various types of fillers; pristine multi-walled carbon nanotube (MWCNT), hydroxyl functionalized multi-walled carbon nanotube (MWCNT-OH) and carboxyl functionalized multi-walled carbon nanotube (MWCNT-COOH) were used to prepare epoxy (EP) composites via ultrasonication and casting techniques. The effect of pristine MWCNT and functionalized MWCNT (MWCNT-OH and MWCNT-COOH) and fillers loading (0-1.0 vol%) on tensile properties of EP composites were investigated and compared. To identify the effectiveness of functional groups on the EP composites, the MWCNT, MWCNT-OH and MWCNT-COOH were compared through tensile testing. The addition of pristine MWCNT decreased the material’s tensile strength and modulus, while the addition of MWCNT-OH decreased the material’s tensile strength. However, among the EP composites, the 0.4 vol% MWCNT-COOH/EP composite exhibited a 12.80% increase in tensile strength (44 MPa). The tensile modulus of 0.4 vol% MWCNT-OH/EP and MWCNT-COOH/EP composites were found to be significantly higher compared to unfilled epoxy which were approximately 15.60% (2376 MPa) and 18.54% (2436 MPa) respectively. In conclusion, the MWCNT-COOH/EP composite showed slight improvement in both the tensile strength and modulus. The effect of functionalized MWCNT was supported by morphological analysis, which demonstrated an improvement in MWCNT-COOH dispersion with slightly fine agglomerates particles at 0.4 vol%.

Influence of hydroxyls at interfaces on motion and friction of carbon nanotube by molecular dynamics simulation

Understanding how the groups at interface influence the friction of carbon nanotubes can provide reference for their applications. In this paper, we investigate the influences of hydroxyls on motion and friction of carbon nanotube on graphite substrate by molecular dynamics simulation. The simulation cases include the ideal vertical carbon nanotube on the ideal graphite substrate, the ideal vertical carbon nanotube on the graphite with hydroxyls on the top layer, the carbon nanotube and the graphite both with hydroxyls on the surface. The results show that the lateral force of carbon nanotube changes when hydroxyls are introduced into the interfaces. If hydroxyls are only on the graphite, the fluctuation of lateral force increases obviously. The reason can be attributed to the increase of atomic surface roughness. Moreover, due to the small contact area between vertical aligned carbon nanotube and substrate, the mean friction becomes raised with hydroxyl content increasing, which is different from the conclusion obtained from silicon tip sliding on graphene with hydrogen on the surface. In that case, owing to the large contact area, the mean friction of tip reaches a maximum value at hydrogen content in a range between 5 and 10% because of the competition between the increase in the number of hydrogen atoms and the weakening of the interlock due to the increase in separation of tip from substrate. Hydrogen bond and Coulomb force appear between interfaces when hydroxyls are both on carbon nanotube and on graphite, which significantly increases friction force on carbon nanotube. And slip interfaces translate rapidly from between carbon nanotube and graphite into between graphite layers. Like the case with hydroxyls only on the graphite, the sliding of carbon nanotube perpendicular to the initial velocity also occurs when carbon nanotube and graphite are both with hydroxyls. This phenomena can be explained as the fact that the introduction of hydroxyls breaks the equilibrium of the force on the carbon nanotube in the Y direction. Moreover, the random distribution of hydroxyls causes the random motion of the carbon nanotube.

The Influence of Hydroxylation on Maintaining CpG Methylation Patterns: A Hidden Markov Model Approach.

DNA methylation and demethylation are opposing processes that when in balance create stable patterns of epigenetic memory. The control of DNA methylation pattern formation by replication dependent and independent demethylation processes has been suggested to be influenced by Tet mediated oxidation of 5mC. Several alternative mechanisms have been proposed suggesting that 5hmC influences either replication dependent maintenance of DNA methylation or replication independent processes of active demethylation. Using high resolution hairpin oxidative bisulfite sequencing data, we precisely determine the amount of 5mC and 5hmC and model the contribution of 5hmC to processes of demethylation in mouse ESCs. We develop an extended hidden Markov model capable of accurately describing the regional contribution of 5hmC to demethylation dynamics. Our analysis shows that 5hmC has a strong impact on replication dependent demethylation, mainly by impairing methylation maintenance.

D2O Interaction with Planar ZnO(0001) Bilayer Supported on Au(111): Structures, Energetics and Influence of Hydroxyls

We investigate the interaction between D2O and the planar ZnO(0001) bilayer grown on Au(111) with temperature programmed desorption (TPD), low energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. We show that D2O molecules adsorbed on this planar surface form two ordered overlayers, a (3 × 3) and a (√3 × √3)R30°, not seen before on any of the bulk ZnO single crystal surfaces. The apparent activation energies of desorption (Ed) estimated from TPD peaks are 15.2 and 16.7–17.3 kcal/mol for (3 × 3) and (√3 × √3)R30°, respectively, which agree well with the adsorption energy values calculated from DFT (14.9–15.6 kcal/mol and 16.8–16.9 kcal/mol, respectively). The DFT calculations reveal that the formation of the overlayers takes place at different packing densities and is mediated by extensive hydrogen bonding among the molecules. The hydroxyl groups, which accumulate very slowly on the ZnO(0001) bilayer surface under the standard ultrahi...

Influence of hydroxylation on fabrication of PVC/CaSO4 composite

The influences of hydroxylation on grafting of aminopropyltrimethoxysilane ((CH3O)3SiCH2CH2CH2NH2, abbreviated as APS) and fabrication of CaSO4/PVC composite were investigated in this paper. The experimental results indicated that the pre-treatment of CaSO4 particles by NaOH promoted the formation of OH−, which enhanced the grafting of APS on CaSO4 surface and improved the interfacial adhesion between CaSO4 and PVC matrix. Compared with the use of CaSO4 with sole APS modification, the use of the CaSO4 with NaOH and APS modification led to the increase of the impact strength of the CaSO4/PVC composite from 36.5kJm−2 to 50.2kJm−2 and the flexural strength from 48.7MPa to 62.1MPa.

Influence of Hydroxylation, Chain Length, and Chain Unsaturation on Bilayer Properties of Ceramides

Mammalian ceramides constitute a family of at least a few hundred closely related molecules distinguished by small structural differences, giving rise to individual molecular species that are expressed in distinct cellular compartments, or tissue types, in which they are believed to execute distinct functions. We have examined how specific structural details influence the bilayer properties of a selection of biologically relevant ceramides in mixed bilayers together with sphingomyelin, phosphatidylcholine, and cholesterol. The ceramide structure varied with regard to interfacial hydroxylation, the identity of the headgroup, the length of the N-acyl chain, and the position of cis-double bonds in the acyl chains. The interactions of the ceramides with sphingomyelin, their lateral segregation into ceramide-rich domains in phosphatidylcholine bilayers, and the effect of cholesterol on such domains were studied with DSC and various fluorescence-based approaches. The largest differences arose from the presence and relative position of cis-double bonds, causing destabilization of the ceramide’s interactions and lateral packing relative to common saturated and hydroxylated species. Less variation was observed as a consequence of interfacial hydroxylation and the N-acyl chain length, although an additional hydroxyl in the sphingoid long-chain base slightly destabilized the ceramide’s interactions and packing relative to a nonhydroxyceramide, whereas an additional hydroxyl in the N-acyl chain had the opposite effect. In conclusion, small structural details conferred variance in the bilayer behavior of ceramides, some causing more dramatic changes in the bilayer properties, whereas others imposed only fine adjustments in the interactions of ceramides with other membrane lipids, reflecting possible functional implications in distinct cell or tissue types.

The effect of alkylation, protonation, and hydroxyl group substitution on reversible alcohol and water addition to 2- and 4-formyl pyridine derivatives

The regiochemical influence of hydroxyl or methoxy substitution on 2- and 4-formyl pyridine derivatives upon alcohol and water addition was studied.

Synthesis by Stille Cross-Coupling Procedure and Electrochemical Characterization of Branched Polymers Based on Substituted 1,3,5-Triarylbenzenes

A series of various substituted 1,3,5-triarylbenzenes, 2,4,6-triaryl-1-phenoles, 1,3,5-triaryl-1-methoxybenzenes and 2,4,6-triaryl-1,3,5-trimethoxybenzenes were synthesized by a Stille cross-coupling procedure. Their structures were confirmed by 1H NMR, 13C NMR, and elemental analysis. Containing thienyl, furyl and EDOT groups polymers obtained in the process of electropolymerization could be carefully considered as a building material in a wide range of organic-electronic devices. We compare properties of monomers and related polymers depending on aryls moieties and their influence of hydroxyl and methoxyl groups attached to the central benzene core.

Influence of Hydroxylation and Copper Binding on Poly (L‐Proline) Type II Helix Formation in the N‐terminal Domain of the Prion Protein

A family of neurodegenerative disorders including scrapie, chronic wasting disease, bovine spongiform encephalopathy and Creutzfeldt‐Jakob disease are thought to be associated with the conversion of normal cellular prion protein (PrPc) to a protease resistant prion isoform, PrPSc (prion protein scrapie). The N‐terminal region of PrP is highly flexible, containing poly (L‐proline) type II (PPII) helical content. The five octarepeat sequences in the N‐terminal region of the prion protein (amino acids 53–90) are also involved in metal ion binding. While the biological role of the N‐terminal region in the conversion of PrPc to PrPSc remains unclear, a recent report indicates that Pro 44 is post‐translationally modified to a 4‐hydroxyproline residue (4‐Hyp) and that the PPII helix content is increased in N‐terminal domain peptides that are hydroxylated. Circular dichroism spectroscopy has been used to examine the effect of hydroxylation at Pro 44 on PPII helix formation in unmodified and modified (4‐Hyp) model peptides of the N‐terminal domain containing zero, one, or two octarepeat sequences (amino acids 37–53, 37–61, 37–69). In all cases, hydroxylation of Pro 44 increases PPII helical content. The addition of copper to these peptides also alters PPII helical content, with different effects observed for each pair of peptides.

Influence of hydroxylation and glycosylation in ring A of soybean isoflavones on interaction with BSA

In this paper, the influence of hydroxylation and glycosylation of soybean isoflavones in ring A on the interaction with BSA was investigated. Two soybean isoflavone aglycones (daidzein and genistein) and their glycosides (daidzin and genistin) were used to study their ability to bind BSA by quenching the BSA intrinsic fluorescence in solution. The hydroxylation and glycosylation of soybean isoflavones in ring A significantly affected the binding/quenching process; in general, the hydroxylation increases the binding affinity and the glycosylation decreased the binding affinity. For daidzein and daidzin, the binding constants for BSA were 5.2 × 10 4 and 5.58 × 10 3 L mol −1, respectively. For genistein and genistin, the binding constants were 8.40 × 10 5 and 1.44 × 10 5 L mol −1, respectively.

Wet air oxidation (WAO) as a precursor to biological treatment of substituted phenols: Refractory nature of the WAO intermediates

Abstract Wet air oxidation (WAO) was investigated as a suitable precursor for the biological treatment of industrial wastewaters that contained high concentrations of phenol, o-cresol or 2-chlorophenol. Two hours WAO semi-batch experiments were conducted at 2 and 9 bar of oxygen partial pressure ( P O 2 ) and at 215, 240 and 265 °C with total organic carbon (TOC) abatement up to 86%. The influence of hydroxyl-, methyl- and chloride ring substitution on the oxidation mechanism of aromatic compounds was established. Also, the readily biodegradable COD fraction (%CODRB) of the WAO effluents was found by respirometric techniques. The maximum %CODRB was 24% for phenol WAO at 265 °C and 9 bar of P O 2 , 10% for o-cresol WAO at 265 °C and 9 bar of P O 2 and 19% for 2-chlorophenol WAO at 215 °C and 2 bar of P O 2 . These results allow comparison of whether or not the WAO effluents were suitable for a conventional activated sludge plant with non-acclimated biomass. Also, the results were compared to those obtained from a previous study for the same model compounds but using catalytic WAO (CWAO) with activated carbon (AC) as a catalyst [1]. This comparison allows us to establish whether or not the WAO effluents were less biodegradable or had more refractory intermediates than CWAO effluents.

Optimization of synthesizing leucine-binding nano-sized magnetite by a two-step transformation

The optimum conditions for synthesizing leucine (Leu)-binding nano-sized magnetite (NSM) particles by a two-step transformation (TST) process were studied. The formation and magnetization of as-synthesized NSM particles were investigated through variation of the acidity, the type of surface modifier, and the nature of the acid for pH adjustment. With increased acidity, the saturation magnetization of the NSM particles decreased, but the amount of Leu coated on the surface of NSM particles increased. After the influence of hydroxyl (OH − ) groups on the sur- face of NSM particles was removed by using the dicarboxyl anion (C2O4 2− ) as a ligand in the first step, Leu was suc- cessfully bound with NSM particles in the second step. However, when polyethylene glycol (PEG) was used as a sur- face modifier, it was difficult to form the Leu-to-NSM particle complex. In terms of the acid used to modify pH, H2SO4 was slightly less effective than HCl in achieving saturation magnetization because the coordination for SO4 2− anions is stronger than that of Cl − anions. The preparation of other amino acid-binding NSM particles can be optimized in an analogous manner.

Ontogenic development-associated changes in the expression of genes involved in rat bile acid homeostasis

Ontogenic changes in the rat bile acid (BA) pool, measured enzymatically and by GC-MS, and expression of enzymes (5alpha-reductase, 5beta-reductase, and cytochrome P450 enzymes Cyp7a1, Cyp8b1, Cyp27 and Cyp3a11), transporters [bile salt export pump, sodium taurocholate-cotransporting polypeptide, apical sodium-dependent bile acid transporter, and organic solute transporter alpha/beta (Ostalpha/Ostbeta)], and nuclear receptors [fetoprotein transcription factor (Ftf), farnesoid X receptor (Fxr), small heterodimer partner (Shp), and hepatic nuclear factor 4alpha (HNF-4alpha)], determined by quantitative PCR, were investigated. The absolute size of the BA pool increased progressively up to adulthood, whereas the complexity of its composition was high in fetuses, decreased after birth, increased again progressively up to adulthood, and decreased in aged animals. Allo-cholic acid only appeared early in development, in spite of low 5alpha-reductase expression. The relative size of the BA pool, corrected by liver weight, was maintained from 1 week after birth, except at weaning, when a transient peak accompanied by Shp downregulation and Cyp7a1 upregulation was observed. An imposed weaning delay of 1 week had no effect on the time course of the BA pool size but decreased the proportion of chenodeoxycholic and alpha-muricholic acids, whereas the proportion of cholic acid was increased, probably as a result of Cyp8b1 upregulation. In conclusion, changes in the expression of genes involved in BA homeostasis may play a role in physiological adaptations to digestive functions during the rat life span.

Catalytic wet air oxidation of substituted phenols using activated carbon as catalyst

Continuous catalytic wet air oxidation (CWAO) was investigated as a suitable precursor for the biological treatment of industrial wastewater that contained phenols (phenol, o-cresol, 2-chlorophenol and p-nitrophenol), aniline, sulfolane, nitrobenzene or sodium dodecylbenzene sulfonate (DBS). Seventy-two-hour tests were carried out in a fixed bed reactor in trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and total pressure were 140°C and 13.1bar, respectively. The influence of hydroxyl-, methyl-, chloride-, nitro-, sulfo- and sulfonic-substituents on the oxidation mechanism of aromatic compounds, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate elimination) were established. The results show that the AC without any supported active metal behaves bifunctionally as adsorbent and catalyst, and is active enough to oxidate phenol, o-cresol, 2-chlorophenol and DBS, giving conversions between 30 and 55% at the conditions tested. The selectivity to the production of carbon dioxide was considerable with total organic carbon (TOC) abatement between 15 and 50%. The chemical oxygen demand (COD) reduction was between 12 and 45%. In turn, aniline, sulfolane, p-nitrophenol and nitrobenzene conversions were below 5% and there was almost no TOC abatement or COD reduction, which shows the refractory nature of these compounds.

Influence of hydroxyl on glass transformation kinetics in lithium disilicate melt and a re-evaluation of structural relaxation in NBS 710 and 711

Differential scanning calorimetry (DSC) experiments are presented that document the strong effect that ppm-level hydroxyl concentrations have on glass transformation kinetics in silicate melt. In particular, relaxation times decrease by an order of magnitude and limiting fictive temperatures ( T f ∞ ) decrease ~20 K with an increase in hydroxyl content from 30 to ~1400 ppmw in the lithium disilicate system. Activation energies derived from Arrhenius plots of reciprocal T f ∞ values versus log(quench rate) show no dependence on hydroxyl content. Heat capacity scans of samples with various hydroxyl contents quenched at the same rate collapse to single curves when scans are plotted using ( T− T f ∞ ). Such behavior can be incorporated most simply into the Tool–Narayanaswamy (TN) model of structural relaxation by allowing only the pre-exponential term in the relaxation function to be a function of hydroxyl content. Fits of our data to the TN model were obtained using three different activation energy values: (1) 757 kJ/mol (from cooling rate dependence of T f ∞ ); (2) 599 kJ/mol (from published viscosity data); and (3) 526 kJ/mol (4-parameter fit). The fit using the activation energy from viscosity measurements provided the best overall fit. In addition, structural relaxation phenomena of NBS 711 and NBS 710, lead silicate and soda-lime silicate compositions, respectively, were re-examined and a significant discrepancy in activation energies for NBS 710 and 711 between this study and earlier work was documented.

Influence of substituent of direct dye having bisphenylenebis(azo) skeletal structure on structure of nascent cellulose produced by Acetobacter xylinum [I]: different influence of Direct Red 28, Blue 1 and 15 on nascent structure

The difference of influence of a certain kind of direct dye on the structure of nascent microbial cellulose was examined, with Direct Red 28 having a biphenylenebis(azo) skeletal structure; Direct Blue 1 having two hydroxyl, two methoxy and two sulfonate groups more than Direct Red 28; and Direct Blue 15 whose sulfonate groups position are different compared to Direct Blue 1. It became clear that the product in the presence of a direct dye (in particular, Direct Red 28) has the structure in which the dye molecule is included between the monolayer in the cellulose sheets corresponding to the (110) plane of microbial cellulose. On the other hand, the structure of the product in the presence of Direct Blue l and 15 contains conceived cellulose II structure which occurred due to be removal of dye during the rinsing process as a result of larger hydrophilicity than its affinity toward cellulose. Solid state 13C NMR and deuteration-IR measurements showed that the product in the presence of direct dye is in a noncrystalline state, although X-ray measurements indicated that they are in a crystalline state. These results support the inclusion of a dye between the (1TO) planes. Solid state 13C NMR and deuteration-IR reveal that the crystal structure of cellulose regenerated from the product in the presence of Direct Red 28 is similar to cellulose IV I, while that from each Direct Blue 1 and 15 product is cellulose II. The difference of the influence of the former and the latter on the nascent cellulose seemed to be caused mainly by the number of sulfonate groups, although the influence of hydroxyl and methoxy groups is not clear at present.