Molar Ratio Of Water Research Articles

Effect of the Amount of Water in the Synthesis of B-TiO2: Orange II Photodegradation

A series of boron-doped TiO2 photocatalysts (2% B-TiO2) with different water/alkoxide molar ratio were synthesized by conventional sol-gel method. The prepared samples were characterized by BET measurement, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIRS), and diffuse-reflectance UV-vis. The phase anatase was present, but unexpectedly a small amount of rutile phase was formed with low and excess water in the synthesis. Additionally it has been observed that the increase in the molar ratio of water significantly increases the values of band gap energy and the specific surface area. Results showed that degradation of Orange II azo dye increases with surface area, particle size, boron, and water content in photocatalysis. The boron species were introduced in the tricoordinated form.

Preparation of Size Controllable BaTiO<sub>3</sub> Nanoparticles in Microemulsion at Low Temperature

Size controllable Barium titanate nanoparticles were synthesized in microemulsion consisting of water, OP-10, hexanol and cyclohexane under atmospheric pressure and low temperature, with Ba (OH)2·8H2O and tetrabutyl titanate used as starting reactants. Products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that 65°C is the proper temperature for the synthesis. The particle size can be controlled by varying the reactants’ concentration, ω value (molar ratios of water to surfactant) and aging time.

Solute dynamics in block-copolymer reverse micelles: do water content and copolymer concentration alter the microenvironment?

Solute dynamics has been explored in reverse micelles formed with the triblock copolymer (EO)13-(PO)30-(EO)13 (L64), where EO and PO represent ethylene oxide and propylene oxide units, respectively, with small amounts of water in p-xylene. To this effect, nonradiative rate constants (knr) and reorientation times (τr) of two carbocyanine derivatives, 3,3'-diethyloxadicarbocyanine iodide (DODCI) and merocyanine 540 (MC 540) have been measured at different mole ratios of water to copolymer (W) and also at three copolymer concentrations. By examining the nonradiative rate constants and the reorientation times of the two solutes, the microenvironment offered by L64/water/p-xylene reverse micellar system has been investigated. It has been observed that there is no variation in the nonradiative rate constants as well as in the reorientation times of both DODCI and MC 540 with an increase in W and [L64]. Since knr represents activated twist motion about the double bonds for these solutes, it is sensitive to the local friction and likewise, τr also provides information about the microenvironment. Thus, the results of this study indicate that DODCI and MC 540 are located in the cores of the L64 reverse micelles that are made up of hydrated ethylene oxide blocks and the hydration levels are not altered despite an increase in the water content and copolymer concentration. In other words, there is no variation in the microenvironment offered by L64/water/p-xylene reverse micellar system upon increasing W and [L64].

Obtention and characterization of a ciclesonide: methyl-beta cyclodextrin complex

Corticosteroids like ciclesonide are used to manage asthma. However, its physicochemical properties—namely water solubility—and, consequently, pharmacokinetics and pharmacodynamics could be object of improvement. One way to achieve this is by the use of cyclodextrins, a well-known group of molecules able to include water-insoluble molecules, solubilising them. The aim of this work is to verify if is possible to obtain a dry powder for inhalation containing ciclesonide included within Crysmeb (a commercially available type of methylated beta-cyclodextrin) applying the simple and inexpensive technique of kneading. Four different dry powders were obtained, varying the water content and molar ratios of drug:cyclodextrin (50 and 90 % water content and 1:1 and 1:2 M drug:cyclodextrin). The complexes were then analysed using different instrumental methods, namely, ultraviolet spectroscopy, differential scanning calorimetry and infrared spectroscopy. The physical characteristics of the powders formulated for inhalation were assessed by the particles time-of-flight (particle size analysis), and the Twin Stage Liquid Impinger (aerodynamic assessment of fine particles). The powder that best performed, overall, was the one obtained with 50 % water content and 1:1 M drug:cyclodextrin. It was concluded that the kneading method is feasible for obtention of a ciclesonide–Crysmeb inclusion complex.

Systematic implicit solvent coarse graining of dimyristoylphosphatidylcholine lipids.

We have used systematic structure-based coarse graining to derive effective site-site potentials for a 10-site coarse-grained dimyristoylphosphatidylcholine (DMPC) lipid model and investigated their state point dependence. The potentials provide for the coarse-grained model the same site-site radial distribution functions, bond and angle distributions as those computed in atomistic simulations carried out at four different lipid-water molar ratios. It was shown that there is a non-negligible dependence of the effective potentials on the concentration at which they were generated, which is also manifested in the properties of the lipid bilayers simulated using these potentials. Thus, effective potentials computed at low lipid concentration favor to more condensed and ordered structure of the bilayer with lower average area per lipid, while potentials obtained at higher lipid concentrations provide more fluid-like structure. The best agreement with the reference data and experiment was achieved using the set of potentials derived from atomistic simulations at 1:30 lipid:water molar ratio providing fully saturated hydration of DMPC lipids. Despite theoretical limitations of pairwise coarse-grained potentials expressed in their state point dependence, all the resulting potentials provide a stable bilayer structure with correct partitioning of different lipid groups across the bilayer as well as acceptable values of the average lipid area, compressibility and orientational ordering. In addition to bilayer simulations, the model has proven its robustness in modeling of self-aggregation of lipids from randomly dispersed solution to ordered bilayer structures, bicelles, and vesicles.

Modified Polyol-Mediated Synthesis of Doped TiO<sub>2</sub> Nanoparticles as the Photoanode in Dye Solar Cells (DSCs)

Synthesis of nanoscale TiO2 exhibiting specific properties of electron or ion conductivity is critical to improve the performance of dye solar cells (DSC). This paper presents the modified polyol-mediated synthesis of doped TiO2 nanoparticles. TiO2 samples were doped with cobalt (Co) and nickel (Ni) and the effects of calcination temperature (550 °C and 650 °C) on the crystallinity of pure samples were investigated. X-ray diffraction (XRD) analysis was used to determine the effect of dopant in lattice structure. The morphology and Crystal structure of TiO2 samples and their chemical analysis was conducted using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometer respectively. Results show agglomeration of spherical particles in all doped samples. Crystal structure in the doped samples reveals modified phases and major crystal phase identical to anatase. It is observed that the molar ratio of water to metal can control the nucleation and growth and prevents significant agglomeration of nanoparticles. More effective doping was recorded for samples with 0.5 % concentration. Effective hydroxyl group is detected in both 0.5% Ni and Co promising good photocatalytic material. SEM images of 0.2% Ni-doped sample shows smallest average particle size.

The photophysics of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester in reverse micelle: excitation wavelength dependent dynamics

This paper focuses on the photophysical studies of 7-(diethylamino)coumarin-3-carboxylic acid N-succinimidyl ester (7-DCCAE) in aqueous reverse micelles using steady state absorption, fluorescence emission and picosecond time resolved emission spectroscopy. We used sodium dioctylsulfosuccinate (AOT) as surfactant to prepare reverse micelles. We have observed excitation wavelength dependent photophysics of 7-DCCAE in the reverse micelles. The red edge excitation shift (REES) was found in the reverse micelles, at different w0 values. The REES gradually decreases with increase in size of the water pool. The rotational relaxation time of the dye molecule decreases with increasing the mole ratio of water to surfactant (w0) inside the reverse micelles. The fluorescence anisotropy decays were found biexponential in nature with fast and slow reorientation times, which is explained by two steps and “wobbling-in-cone model”. We have observed the excitation wavelength dependent dynamics of 7-DCCAE in the reverse micelles. We have observed the difference in the photophysics 7-DCCAE with its acid form.

Physicochemical studies of water-in-oil nonionic microemulsion in presence of benzimidazole-based ionic liquid and probing of microenvironment using model C–C cross coupling (Heck) reaction

The present report focuses on the evaluation of the interfacial composition and the thermodynamics of the transfer of 1-pentanol (Pn) from a continuous oil phase to the interface of w/o nonionic microemulsion [Tween-20/Pn/cyclohexane(Cy)/water] in the absence and the presence of an ionic liquid (IL) (1-butyl-3-propylbenzimidazolium bromide) under different physicochemical conditions [viz. variation in concentrations of IL (0.0 → 0.20 mol dm−3) and temperature (293 → 323 K] at a fixed molar ratio of water to surfactant (ω) by the Schulman's method of cosurfactant titration at the oil/water interface. The overall transfer process has been found to be spontaneous, exothermic and organized in the absence or the presence of IL, but shown to be influenced by [IL]. The microstructure and state of water organization inside a pool of these systems have been characterized by different experimental techniques, e.g., conductivity, DLS and FTIR in the absence or the presence of IL. In addition, a C–C cross coupling reaction (Heck reaction) has been employed to explore the properties of IL (additive) in the confined environment of the microemulsion vis-a-vis its interaction with the constituents of the interface. The reaction progress has been monitored using the above techniques. The reaction ended with the highest yield (75%) in the presence of 0.05 mol dm−3 of IL, wherein the microemulsion forms spontaneously with the highest stability.

Synthesis of silver nano-particles using micro-emulsion technique

Silver nanoparticles were synthesized by mixing two micro-emulsion systems – one with precursor (AgNO3) and one with reducing agent (NaBH4). Dioctyl sodium sulfonsuccinate – AOT was used as surfactant. We studied parameters as ω – molar ratio of water to surfactant, hydrocarbon (oil) types. The molar ratio of water to surfactant was changed from 2.5 to 5; 7.5 and 10. The used oil types were cyclohexane, iso-octane, and dodecane. XRD, UV-Vis and TEM images were used to elucidate the structure and size of the products. The results showed that, synthesized silver nanoparticles sizes were between 5 – 7 nm, with homogeneously spherical shapes. The silver colloids were used in antibacterial applications. The antibacterial efficiency was very high, above 99% at ~ 4 μg/ml concentration of silver nanoparticles.

Batch and fed-batch enzymatic hydrolysis of soybean oil under ultrasound irradiation

Abstract This work reports the hydrolysis of fatty acids from soybean oil using a commercial immobilized lipase (Lipozyme TL IM) under the influence of ultrasound irradiation. Batch and fed-batch experiments were performed at 65 °C, 10 wt% of enzyme concentration, oil to water molar ratio of 1:9, output irradiation power of 132 W, and 600 rpm agitation. Results show that ultrasound-assisted lipase-catalyzed hydrolysis of oils system might be a potential alternative route to conventional methods, as almost complete reaction yield was achieved for the fed-batch system, with relatively good results for the batch mode at mild irradiation power supply and temperature in a relatively short reaction time, 120 min. Besides, it is shown that the initial reaction rates are of hydrolysis are increased when ultrasound irradiation was applied into the reaction system.

Hydrogenation of 5-hydroxymethylfurfural in supercritical carbon dioxide–water: a tunable approach to dimethylfuran selectivity

The use of supercritical carbon dioxide–water on the hydrogenation of 5-hydroxymethylfurfural (HMF) was investigated over a Pd/C catalyst. It was possible to achieve a very high yield (100%) of DMF within the reaction time of 2 hours at 80 °C. A significant effect of CO2 pressure was observed on the product distribution. Simply by tuning the CO2 pressure it was possible to achieve various key compound, such as tetrahydro-5-methyl-2-furanmethanol (MTHFM) (<10 MPa), 2,5-dimethylfuran (DMF) (10 MPa) and 2,5-dimethyltetrahydrofuran (DMTHF) (>10 MPa) with very high selectivity. Optimization of other reaction parameters revealed that H2 pressure, temperature, as well as the CO2–water mole ratio, played an important role in the selectivity to the targeted DMF. It is interesting to note that a very high yield of DMF was achieved when a combination of CO2 and water was used. For instance, in the absence of water or CO2, the selectivity of DMF was low; similarly, an excess of water against the fixed pressure of CO2 reduced the selectivity to DMF. Hence, an optimized amount of water was mandatory in the presence of CO2 for the formation of DMF with high selectivity. This method was successfully extended to the hydrogenation of furfural, which could afford 100% selectivity to 2-methylfuran with complete conversion within a very short reaction time of 10 min. The studied catalyst could be recycled successfully without significant loss of catalytic activity.

Hydrothermal synthesis of hydroxy sodalite zeolite membrane: Separation of H2/CH4

In this study, hydroxy sodalite (HS) zeolite was synthesized via hydrothermal method. As reported in the literature, the recommended molar composition of H2O/Al2O3 for HS zeolite synthesis is about 1000. However in our work, HS zeolite was synthesized using new molar compositions of H2O/Al2O3 for different synthesis times and their effects on morphology and crystallinity of the synthesized zeolites were investigated. Also, HS zeolite membranes were synthesized on seeded supports using synthesized powders and the effect of seed size was also investigated. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Gas permeation through the membranes was also measured. First of all, it was found that synthesis time has a significant effect on crystallinity and crystal size of the synthesized zeolite. Also, water molar ratio can control crystal size of the synthesized zeolite.It was found out that with increasing the seed size, H2 and CH4 permeations decrease, from 3224 to 279 (Barrer) and from 611 to 45 (Barrer), respectively, while the H2/CH4 selectivity increases from 5.28 to 6.20. Finally, to obtain HS zeolite with desirable particle size, crystallinity and morphology, optimum synthesis conditions were proposed.

Toward a Single-Layer Two-Dimensional Honeycomb Supramolecular Organic Framework in Water

The self-assembly of well-defined 2D supramolecular polymers in solution has been a challenge in supramolecular chemistry. We have designed and synthesized a rigid stacking-forbidden 1,3,5-triphenylbenzene compound that bears three 4,4'-bipyridin-1-ium (BP) units on the peripheral benzene rings. Three hydrophilic bis(2-hydroxyethyl)carbamoyl groups are introduced to the central benzene ring to suppress 1D stacking of the triangular backbone and to ensure solubility in water. Mixing the triangular preorganized molecule with cucurbit[8]uril (CB[8]) in a 2:3 molar ratio in water leads to the formation of the first solution-phase single-layer 2D supramolecular organic framework, which is stabilized by the strong complexation of CB[8] with two BP units of adjacent molecules. The periodic honeycomb 2D framework has been characterized by various (1)H NMR spectroscopy, dynamic light scattering, X-ray diffraction and scattering, scanning probe and electron microscope techniques and by comparing with the self-assembled structures of the control systems.

ChemInform Abstract: Novel Antitumor Agent, Trilacunary Keggin‐Type Tungstobismuthate, Inhibits Proliferation and Induces Apoptosis in Human Gastric Cancer SGC‐7901 Cells.

AbstractYellow (Himi)2 [(W(OH)2)2(Mn (H2O)3)2(Na3 (H2O)14)(BiW9O33)2] ·16H2O (I) (imi: imidazole) is synthesized by reaction of Na2WO4·2H2O, Bi(NO3)3·5H2O, imi, and MnCl2·6H2O (4.7:0.5:1:0.7 molar ratio) in water (stirring at 80 °C, 2 h; addn.

Can Critical Packing Parameter Depict Probe Rotation in Block-Copolymer Reverse Micelles?

Rotational diffusion of two ionic probes, cationic rhodamine 110 (R110) and anionic fluorescein (FL), has been examined in reverse micelles formed with the triblock copolymer (EO)13-(PO)30-(EO)13 (L64), where EO and PO represent ethylene oxide and propylene oxide units, respectively, with small amounts of water in p-xylene. This study has essentially been undertaken to explore the influence of mole ratio of water to copolymer (W) as well as copolymer concentration on probe rotation. On the basis of fluorescence lifetimes and reorientation times, it has been established that both R110 and FL are located in the interfacial region of L64/water/p-xylene reverse micellar system. The average reorientation time decreases by 10-35% with an increase in W for both the probes at a given copolymer concentration. However, for a particular W, the average reorientation time increases by 10-30% as the concentration of the copolymer is enhanced. From the micellar structural parameters available in the literature, critical packing parameters have been calculated for the L64/water/p-xylene reverse micellar system, and it has been noticed that the average reorientation times of both the probes scale linearly with the critical packing parameter. In essence, the results of this study indicate that the probe mobility in the interfacial region of block copolymer reverse micelles is governed by the micellar packing.

Optimized synthesis and photovoltaic performance of TiO2 nanoparticles for dye-sensitized solar cell

This paper presents response surface methodology (RSM) as an efficient approach for modeling and optimizing TiO2 nanoparticles preparation via co-precipitation for dye-sensitized solar cell (DSSC) performance. Titanium (IV) bis-(acetylacetonate) di-isopropoxide (DIPBAT), isopropanol and water were used as precursor, solvent and co-solvent, respectively. Molar ratio of water, aging temperature and calcination temperature as preparation factors with main and interaction effects on particle characteristics and performances were investigated. Particle characteristics in terms of primary and secondary sizes, crystal orientation and morphology were determined by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Band gap energy and power conversion efficiency of DSSCs were used for performance studies. According to analysis of variance (ANOVA) in response surface methodology (RSM), all three independent parameters were statistically significant and the final model was accurate. The model predicted maximum power conversion efficiency (0.14%) under the optimal condition of molar ratio of DIPBAT-to-isopropanol-to-water of 1:10:500, aging temperature of 36°C and calcination temperature of 400°C. A second set of data was adopted to validate the model at optimal conditions and was found to be 0.14±0.015%, which was very close to the predicted value. This study proves the reliability of the model in identifying the optimal condition for maximum performance.

Structure of aqueous potassium tetraborate solutions by X-ray scattering

The borate species in aqueous potassium tetraborate solution were obtained according to the chemical species distribution diagram and the Raman spectrum. X-ray scattering is used to study the solutions with salt–water molar ratios of 1 : 25, 1 : 20 and 1 : 15 at 298 and 323 K. The model calculation and model refinement programmes are used to calculate the structure parameters r i−j , b i−j and n i−j . It manifests that the first hydration distance of K+ is ∼0.29 nm, with an average hydrated number of 8.0. The hydration bond peak is around 0.278 nm and the coordination number is from 1.9 to 2.4. Borate anions coordinate with K+ ions in the mono-dentate form, the average distance of K–B is 0.38 nm. The distance of B–H2O in hydrated anion is from 0.37 to 0.38 nm with the hydrated number 4–9. The other interaction such as water shared pair interaction is also discussed.

Ethanol steam reforming for hydrogen generation over structured catalysts

The present paper reports on the preparation, characterization and reaction evaluation of structured catalysts toward hydrogen generation via ethanol steam reforming. To these ends, 400 cpsi cordierite monoliths were functionalized with Rh–Pd/CeO2 catalyst. SEM, TEM and XRD showed a uniform and well-covering CeO2 layer where Rh–Pd nanoparticles of less than 0.5 nm were anchored. The functionalized monoliths were successfully tested for synthesis gas production from ethanol steam reforming. Realistic operating conditions were selected, including temperatures between 500 and 950 K, pressures from 1 to 6 bar, undiluted ethanol:water molar ratios 1:4–1:8 (i.e., 2 ≤ S/C ≤ 4) and a wide range of feed loads. Appropriate activity and hydrogen selectivity were verified for the catalytic system, with ca. complete ethanol conversion at T > 700 K and a minor, or even negligible, generation of by-products (acetaldehyde, acetone, ethane, ethylene). Operating at 950 K and 1.5 bar, a H2 yield of 3.4 mol hydrogen per mol ethanol in feed was achieved for a liquid feed load of 0.22 μlliq/(mgcat min) (S/C = 3), with 8.1% of CH4 and 8.2% of CO on dry basis. Kinetic parameters of a phenomenological set of reaction rate equations were fitted against experimental data, considering ethanol decomposition (methane formation) with subsequent methane steam reforming to both CO and CO2 and water–gas shift reaction.

Optimization of Enzymatic Hydrolysis of Sacha Inchi Oil using Conventional and Supercritical Carbon Dioxide Processes

AbstractSacha inchi (Plukenetia volubilis) oil has high polyunsaturated fatty acids content. The hydrolysis of this oil is an efficient way to obtain desirable free fatty acids (FFA). The optimization of parameters was carried out according to the maximum production of FFA using two enzymatic hydrolysis processes. The effect of enzyme concentration (5–40 % based on weight of oil), temperature (40–60 °C), and oil:water molar ratio (1:5–1:70) were studied for the conventional enzymatic hydrolysis process, while pressure (10–30 MPa) and oil:water molar ratio (1:5–1:30) were studied for the enzymatic hydrolysis in supercritical carbon dioxide (SC‐CO2) media. The hydrolysis in SC‐CO2 media resulted in higher production of FFA (77.98 % w/w) at 30 MPa and an oil:water molar ratio equal to 1:5 compared to the conventional process (68.40 ± 0.98 % w/w) at 60 °C, oil:water molar ratio equal to 1:70, and 26.17 % w/w, enzyme/oil. The only significant parameter on the production of FFA for conventional enzymatic hydrolysis was enzyme concentration, while for the hydrolysis in SC‐CO2 media both pressure and the molar ratio of oil:water were significant. Lipid class analyses showed that with both methods, FFA, monoglycerides, and diglycerides content in the final product increased compared to pure oil, while triglycerides content decreased. Fatty acid composition analysis showed that the content of fatty acids in the FFA form were similar to their triglyceride form.

Synthesis of Low Molecular Distribution Dihydric Polybutadiene in the Presence of Triflic Acid

A method is described for the preparation of functional polybutadiene (PB) with hydroxyl groups along the polymer chain. This material can be used directly or as the starting substrate for further polymerization in both academic and industrial processes. We have developed a convenient method to obtain a polymer with a narrow molecular weight distribution and with a known content of hydroxyl groups along the backbone. By controlling the hydroxylation reaction conditions, the appropriate molar ratios of THF, water and acid with the epoxide are 30, 15 and 1.5, respectively. By minimizing the crosslinking reaction, the desired PB was prepared and subsequently characterized.