Alkoxide Solutions Research Articles

Transesterification catalyst strength as observed by solution-based oxygen-17 nuclear magnetic resonance spectroscopy

Natural abundance oxygen-17 nuclear magnetic resonance spectroscopy (17O-NMR) was applied to study homogeneous transesterification catalysts for fatty acid methyl ester production. Alkoxide catalysts were made with selected permutations of lithium, sodium, magnesium, and potassium hydroxides with ethanol, methanol, isopropanol, and glycerol. Pilot scale transesterification reactions of Canola oil were completed and the 17O-NMR spectra were collected from the reaction products. The alkoxide solutions showed the downfield shifts relative to the reagent alcohol, in a linear relationship with the concentration of catalyst ion. The electron deshielding of the oxygen of the alkoxide catalyst is observed directly by 17O-NMR, and the fastest catalyst has the largest downfield (high frequency) shift. This effect is most pronounced in potassium methoxide and less pronounced for less polar solvents such as isopropanol.

Effect of the heating rate on crystallization and densification of TiO2 films prepared from alkoxide solutions containing various organic additives

ABSTRACT The effect of the heating rate on crystallization and densification of sol–gel-derived TiO2 films has been investigated. The TiO2 gel films were prepared from Ti(OC3H7 i )4 solutions containing alcohols (2-butanol and 2-methoxyethanol), glycols (propylene glycol, diethylene glycol and dipropylene glycol) and chelating agents (acetylacetone and benzoylacetone) as organic additives, followed by heat treatment to 800°C at various heating rates. In the cases without organic additives and with alcohols, anatase films were obtained irrespective of the heating rate, where the refractive indexes of the films were higher for slower heating rate. Conversely, for the films prepared with glycols and chelating agents, rapid heating activated crystallization and densification. In particular, addition of chelating agents led to the formation of rutile films with much higher refractive indexes than those of the anatase films.

One-pot synthesis of novel poly-substituted 3-cyanopyridines: Molecular docking, antimicrobial, cytotoxicity, and DFT/TD-DFT studies

Novel pyridine-3-carbonitrile derivatives, denoted as (4a-j), were synthesized using a convergent synthetic approach that involved a one-pot four-component reaction. This was achieved by utilizing a combination of various aromatic aldehydes, acetophenone derivatives, malononitrile, and four different sodium alkoxide solutions. The synthesized compounds were characterized using various spectroscopic techniques such as IR, 1HNMR , 13CNMR , and elemental analysis. Molecular docking simulations were employed to investigate the binding affinity of compounds (4a-j) towards two proteins, DHFR and HT-hTS. The results revealed that 4-(4-chlorophenyl)-2-ethoxy-6-phenyl-pyridine-3-carbonitrile (4a) compound exhibited the highest binding affinity score (ΔG = -8.06 Kcal/mol) upon docking into the active site of DHFR, while 2-(4-nitrophenyl)-6-(4-chlorophenyl)-4-ethoxy-pyridine-3-carbonitrile (4d) compound displayed the strongest binding affinity score (ΔG = -4.17 Kcal/mol) when docked to the active site of HT-hTS. These results were supported by the cytotoxic activity of selected compounds (4a, 4b, 4e, and 4 h) against human cancer cell lines (MCF7, HT29, and A2780) as well as normal human fetal lung fibroblast (MRC5) using MTT assay. The cytotoxicity analyses revealed that compound (4a) displayed cytotoxic activity against all cancer cell lines, particularly human colorectal carcinoma (HT29) with an IC50 value of 2.243±0.217 μM, which is lower than that of the reference drug (Doxorubicin) with an IC50 value of 3.964±0.360 μM. Furthermore, compound (4a) exhibited a lower cytotoxic effect on normal human fetal lung fibroblast (MRC5) with an IC50 value of 2.222±0.137 μM, as compared to the IC50 value of the reference drug (Doxorubicin) which was 2.476±0.033 μM. The antimicrobial activity of selected compounds such as (4a, 4c, and 4f) was also evaluated against a panel of microorganisms, including two gram-positive strains (Staphylococcus aureus and Enterococcus faecalis) and two gram-negative strains (Escherichia coli and Pseudomonas aeruginosa). The zone of inhibition and minimum inhibition concentration (MIC) demonstrated the potency of these compounds. Specifically, compounds 4-(4-chlorophenyl)-2-ethoxy-6-phenyl-pyridine-3-carbonitrile (4a) and 4-(4-methoxyphenyl)-2‑methoxy-6-(4-nitrophenyl)-pyridine-3-carbonitrile (4f) exhibited MIC of 0.013 µM against E. coli strains, which is comparable to that of the reference drug amoxicillin (MIC=0.01 µM). Finally, Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) studies were performed on compounds (4a-j) to obtain a more comprehensive understanding of the structure-activity relationship and solvatochromic behavior of these molecules. Overall, the results suggest that compound (4a) could potentially serve as a promising cytotoxic and antibacterial agent with a better safety profile and reduced side effects on normal cells.

Chemical Absorption of CO2 Enhanced by Solutions of Alkali Hydroxides and Alkoxides at Room Temperature

AbstractThis article presents the study of CO2 capture through aqueous solutions with high basicity conditions. Systematic experiments were conducted to assess the performance of alcohols mixed with aqueous alkaline hydroxides for carbon dioxide capture. Alcohols can work as a catalyst in the capture of CO2 providing greater basicity, a lower surface tension, and an amphiphilic character in the polar aqueous solvent/ (nonpolar CO2 and N2) gas mixture interface, and a lower temperature of solvent regeneration. The results showed that short‐chain alcohols, such as methanol and ethanol, and alkaline metals of greater molar mass (i. e., K compared to Na) can produce greater basicity and a higher CO2 absorption rate in the mixtures than conventional aqueous solutions such as ammonia or monoethanolamine in the same concentration. DFT calculations of electronic and thermodynamic properties for CO2 absorption reactions were carried out to analyze the nucleophilic trend of the short‐chain alkoxides studied. The volumetric proportion between water and alcohol, as well as the concentration of alkaline hydroxide, influences the rate of CO2 absorption, the temperature of regeneration and volatility of the solvent, and the formation of precipitates. CO2 absorption rates greater than 90 % v/v and solvent regeneration temperatures of approximately 78 °C were achieved using ethanol, water, and KOH.

Efficient Synthesis of 6,7-Dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile Compounds and Their Applicability As Inhibitor Films for Steel Alloy Corrosion: Collective Computational and Practical Approaches.

An effective method for designing new heterocyclic compounds of 6,7-dihydro-5H-cyclopenta[b]pyridine-3-carbonitrile derivatives (CAPDs) was presented through cyclocondensation reaction between 2,5-diarylidenecyclopentanone derivatives and propanedinitrile, and the cyclocondensation reaction succeeded using a sodium alkoxide solution (sodium ethoxide or sodium methoxide) as the reagent and the catalyst. The synthesized CAPD derivatives were employed as novel inhibitors for carbon steel (CS) corrosion in a molar H2SO4 medium. The corrosion protection proficiency was investigated by electrochemical measurements (open circuit potential vs time (EOCP vs t), potentiodynamic polarization plots (PDP), and electrochemical impedance spectroscopy (EIS)) and surface morphology (scanning electron microscopy (SEM)) examinations. The results show that the CAPD derivatives exhibit mixed type inhibitors and a superior inhibition efficiency of 97.7% in the presence of 1.0 mM CAPD-1. The adsorption of CAPD derivatives on the CS interface follows the Langmuir isotherm model, including physisorption and chemisorption. Scanning electron microscopy (SEM) exploration confirmed the adsorption of the CAPD derivatives on the CS substrate. Monte Carlo (MC) simulations and DFT calculations revealed that the efficacy of the CAPD molecules correlates well with their structures, and this protection was attributed to their adsorption on the CS surface.

B2O3 katkılı TiO2 ve katkısız ince filmlerin yüzey özelliklerinin Sol-jel yöntemi ile karşılaştırılması

Titanium dioxide (TiO2) is a widely used material in nanotechnological applications. Especially in photocatalytic and optical applications, TiO2 thin films are an indispensable material. Metal-doped thin films are of interest to researchers for the development of these properties. In this study, the effect of boron oxide (B2O3) additive on surface properties in coating TiO2 thin films on soda-lime glasses was investigated. In the experimental study, alkoxide solutions with a source of boron and titanium were used. TiO2 sol was prepared with Sol-Gel method. In addition, the sol was prepared by adding Triisopropyl borate. Condensation and polymerization steps were completed in acid catalysis and the solution was obtained. In the home-made dip coater device, the solution is coated on the surface. The surface properties of dried thin films have been characterized by applying morphological analysis and contact angle measurement tests. As a result, the B2O3-doped TiO2 coated surface was found to have better hydrophilic properties than the non-doped TiO2 surface. It has been observed that the boron oxide-doped TiO2 coated glass material has a superhydrophilic value.

Effect of titanium source and sol-gel TiO2 thin film formation parameters on its morphology and photocatalytic activity

Abstract TiO2 thin films with different surface structure have been prepared from alkoxide solutions by the sol-gel method using different cationic precursors and heat treatment techniques. The effect of using titanium isopropoxide as well as titanium butoxide as a titanium source on the surface structure and photocatalytic activity of the resultant thin films was studied. Significant differences in the rate of hydrolysis and condensation reactions during the sol-gel synthesis were observed for these titanium precursors. This had a direct influence on the morphology of the as-prepared TiO2 films. Higher quality oxide coatings were obtained from titanium isopropoxide. They were characterized by a smaller grain size, improved surface roughness and uniform coverage of the glass substrate. A beneficial effect of calcination process after each sol application cycle in contrast to single step calcination after all dip-coating cycles was observed. Photocatalytic degradation tests showed that methyl orange was decolorized in the presence of all prepared TiO2 films by exposing their aqueous solutions to UV light (λ = 254 nm). The highest photocatalytic activity had the TiO2 layer produced using titanium isopropoxide.

Biodiesel production by interesterification of rapeseed oil with methyl formate in presence of potassium alkoxides

An alternative method for the biodiesel or fatty acid alkyl ester (FAAE) synthesis has been proposed—rapeseed oil interesterification with methyl formate. Reaction with methyl formate proceeds at a relatively low temperature (28 °C) instead of 55–65 °C necessary for triglyceride reactions with methanol and other monoesters. Similarly to transesterification with methanol, the product of the reaction with methyl formate consists of two layers. The main product the fatty acid methyl ester (FAME) is located in the top layer, but the process by-product formins forms the bottom layer. In this work, solutions of potassium alkoxides (methoxide, ethoxide, isopropoxide, tert-butoxide) in appropriate alcohols as homogeneous catalysts were used, adhering to the catalyst to oil molar ratio (COMR) 0.1 and methyl formate to oil molar ratio (MFOMR) 18. The FAAE content in the biodiesel layer in presence of all catalysts was 77–81 wt.%, which is lower than the level required by the EN14214 but significantly higher than the FAME content in reactions with methyl acetate under the same conditions. Fuel properties such as flash point, carbon residue, density, viscosity, and cold flow properties were investigated. For samples with MFOMR equal to or higher than 36 FAAE exceed 93% and the main characteristics of samples correspond to the EN14214 limits even without product purification.

In-plane stress development in sol–gel-derived titania and silica thin films on Si(100) substrates

In order to study (i) how the in-plane stress develops in alkoxide-derived oxide gel films on heating and (ii) how the residual stress changes with firing temperature, we prepared titania and silica gel films on Si(100) wafers from alkoxide solutions. The intrinsic stress was previously measured in situ during heating up to 500 °C for the gel films, where the stress was calculated from the radius of curvature of the substrate bending. Because the commercialized apparatus that measures the substrate bending has an upper limitation of temperature at 500 °C, we devised a method for estimating the intrinsic stress over 500 °C in the present work. The gel films were heated from 100 °C up to 900 or 1000 °C successively and cumulatively. Then we estimated the intrinsic stress over 500 °C by monitoring the changes in stress in situ during heating and cooling for the cumulatively fired films. Combining the estimated data over 500 °C with those measured below 500 °C, we found that the intrinsic stress increases and then decreases around to zero with temperature for both titania and silica gel films, which we recognized as a general trend in alkoxide-derived oxide thin films in conjunction with our previous work on yttria stabilized zirconia (YSZ) films. Regarding the residual stress, the titania and silica films exhibited different behaviors. The titania film showed an increase followed by a slight decrease, and finally a significant increase in residual tensile stress with increasing firing temperature. The silica films also exhibited an increase and a decrease in residual tensile stress with increasing firing temperature, but the stress continued to decrease and turned into compressive one at ca 800 °C. The last decrease in residual tensile stress that turned into compressive one resulted from the development of compressive thermal stress during cooling, which is due to the smaller thermal expansion coefficient of silica than silicon. It was thus clarified that the difference in thermal expansion coefficient between the film and the substrate becomes prominent in residual stress when the films are fired at high temperatures like 800 °C. Thus we could successfully obtain a general view on how the residual stress changes with firing temperature as well as on how the in-plane stress develops during heating thanks to the information on the stress development in the sol–gel-derived titania and silica films that was added to the information on the YSZ films.

Biphasic Sol-Gel Synthesis of Microstructured/Nanostructured YVO4:Eu3+ Materials and Their H2O2 Sensing Ability.

Microstructured/nanostructured YVO4:Eu3+ powders and films were synthesized through a biphasic sol–gel method, aiming at their application as H2O2 sensing materials based on the turn-off luminescence of Eu3+ ions. The synthesis was typically carried out at temperatures of 80 °C or lower by using organic solutions to dissolve vanadium alkoxide and aqueous solutions to dissolve yttrium and europium salts together with sodium carboxylates. The resultant crystalline YVO4:Eu3+ powders and films were characterized as containing micrometer-sized particles comprising primary nanoparticles with high specific surface areas. A comparative study was performed on the H2O2-responsive turn-off luminescence properties for the above samples and those synthesized by a single-phase sol–gel or a conventional solid-state reaction method. The results indicated that the microstructural feature of the samples from the biphasic sol–gel method was effective for detecting H2O2 through its adsorption on the particle surface and quenching of the Eu3+ luminescence. The film samples showed repeatable and quantitative turn-off luminescence, thereby demonstrating their suitability as solid-state H2O2 sensors.

An efficient synthesis of benzylidene-2-alkoxy-4-aryl-2,3-cycloalkenopyridine-3-carbonitrile derivatives

An efficient procedure for the synthesis of a novel class of benzylidene-2-alkoxy-4-aryl-6,7-dihydro-5H-cyclopenta[b]pyridine-, -5,6,7,8-tetrahydroquinoline and/or -6,7,8,9-tetrahydro-5H-cyclohepta[b]pyridine-3-carbonitrile was introduced through the one-pot multi-component reaction of cyclopentanone, cyclohexanone, and/or cycloheptanone with different aromatic aldehydes and malononitrile. The same products were also produced by classical route by the two-component reaction of dibenzylidine cyclopentanone, cyclohexanone, and/or cycloheptanone derivatives with malononitrile. The reactions were achieved using sodium alkoxide solution as catalyst and reagent.

Controlling the Composition, Morphology, Porosity, and Surface Chemistry of Lignin-Based Electrospun Carbon Materials

Electrospinning is a suitable top-down technique for the preparation of polymeric fibers using high voltage electrical fields and solutions of the selected polymer of adequate viscosity and conductivity. The versatility of electrospinning allows accurate control of the morphology and composition of the fibers by a wide combination of operating conditions and small modifications of the spinneret and collector. Alcell lignin, which is extracted from lignocellulosic biomass using organic solvents through Organosolv process, is readily solved in ethanol, producing a solution that matches the requirements of the electrospinning process. This review summarizes the vast collection of carbon materials that can be obtained by processing lignin using electrohydrodynamic forces. The coaxial and triaxial electrospinning setups allow for obtaining fibers with two or more components hierchically arranged, the use of these configurations along with a carefully setting of the operating conditions (distance between needle and collector, voltage, flow rate,…) and the solution properties (conductivity, viscosity,…) facilitates the conformation of lignin into spheres, beaded fibers, straight fibers and fused meshes. All these morphologies can be implemented with solid or hollow bodies (i.e. enabling the production of tubes and hollow spheres) by using a sacrificial templating agent. Phosphoric acid can also be added in small amounts to the lignin solution, shortening the thermostabilization time of the fibers. The porosity of the phosphorus containing carbon fibers can be modified in the last stage of the preparation of carbon fibers by controlled gasification process, owing to the extended oxidation resistance of the P-doped fibers. Fibrillar carbon catalysts can be also obtained by one-pot preparation method, only solving small quantities of metallic salts in the lignin solution. In addition, alumina and silica-coated lignin fibers were produced by feeding a partially gelated solution of the respective alkoxide through the outer needle of the spinneret. The coated fibers can be carbonized without thermostabilization step, decreasing considerably the preparation time. All these carbon materials were successfully tested in different applications such as heterogeneous catalysis, energy storage and environmental protection, confirming that electrospinning is a powerful tool for maximizing the value of lignin as carbon precursor.

Electro-Caloric Properties of BT/PZT Multilayer Thin Films Prepared by Sol-Gel Method.

In this study, Barium Titanate (BT)/Lead Zirconate Titanate (PZT) multilayer thin films were fabricated by the spin-coating method on Pt (200 nm)/Ti (10 nm) SiO2 (100 nm)/P-Si (100) substrates using BaTiO3 and Pb(Zr0.90Ti0.10)O3 metal alkoxide solutions. The coating and heating procedure was repeated several times to form the multilayer thin films. All of BT/PZT multilayer thin films show X-ray diffraction patterns typical to a polycrystalline perovskite structure and a uniform and void free grain microstructure. The thickness of the BT and PZT film by one-cycle of drying/sintering was approximately 50 nm and all of the films consisted of fine grains with a flat surface morphology. The electrocaloric properties of BT/PZT thin films were investigated by indirect estimation. The results showed that the temperature change ΔT can be calculated as a function of temperature using Maxwell's relation; the temperature change reaches a maximum value of ~1.85 °C at 135 °C under an applied electric field of 260 kV/cm.

Controlling nucleation and growth of nano-CaCO3 via CO2 sequestration by a calcium alkoxide solution to produce nanocomposites for drug delivery applications

The proposed sol-gel synthesis of CaCO3 proved to create unprecedented size of CaCO3 nanoparticles with striking size uniformity. The obtained results clearly demonstrate their ability to incorporate hydrophobic components in a nanocomposite matrix converting them into amorphous nano sized particles, building stable colloids via release in acidic medium. Transfer of a sol produced in organic medium into water in the presence of albumen surfactant results in relatively uniform micro particles about 1μm size. The obtained materials show characteristics attractive for use in drug delivery and potentially also a variety of other industrial applications.

Experimental design applied to optimisation of silica nanoparticles size obtained by sonosynthesis

In this paper, the sonocatalysis has been successfully used to synthesise silica nanoparticles. The Stober method which implies silicon alkoxide, ammonia and aqueous alcohol solution with magnetic stirring followed by ultrasound bath was modified with the use of a high-power ultrasound probe. The factors considered to prepare silica nanoparticles were the amount of water, tetraethyl orthosilicate and ammonia concentrations, reaction temperature, energy applied by the ultrasound probe and insonation time. The synthesis time was significantly reduced (from 270 to 10 min compared to the traditional Stober method), and smaller nanoparticles have also been obtained. Statistical experimental design has allowed us to establish the most important factors and its interactions, which influence on the size and size distribution, with a reduced number of experiments. A central composite experimental design at two levels was selected. Dynamic light scattering (DLS) was used to characterise the silica nanoparticles. The sizes obtained for different conditions ranged from 6 to 153 nm. Zeta potential was also estimated to establish its stability. In some cases, transmission electron microscopy was used to evaluate the nanoparticle shape.

Photoinduced Formation of Colloidal Silver in Nitrocellulose Solutions Containing Titanium Alkoxides

The study shows the possibility of photo-induced reduction of silver nitrate and formation of stable colloidal silver particles in an isopropanol-N,N-dimethylacetamide solution of titanium alkoxide (polybutyl titanate) stabilized by nitrocellulose. It is established that titanium alkoxide and the products of its partial hydrolysis in the liquid composition play the role of a photocatalyst for the reduction of silver ions; the introduction of nitric or acetic acid additives to the composition significantly increases its photosensitivity. The films deposited from the liquid composition, previously irradiated with visible or UV light, consist of hydrated titanium dioxide and nitrocellulose with incorporated colloidal silver. Thermal treatment of the films at 150–245°C leads to the decomposition of nitrocellulose and an increase in the absorption by silver particles.

Low-cost composites based on porous titania–apatite surfaces for the removal of patent blue V from water: Effect of chemical structure of dye

Hydroxyapatite/titania nanocomposites (TiHAp) were synthesized from a mixture of a titanium alkoxide solution and dissolution products of a Moroccan natural phosphate. The simultaneous gelation and precipitation processes occurring at room temperature led to the formation of TiHAp nanocomposites. X-ray diffraction results indicated that hydroxyapatite and anatase (TiO2) were the major crystalline phases. The specific surface area of the nanocomposites increased with the TiO2 content. Resulting TiHAp powders were assessed for the removal of the patent blue V dye from water. Kinetic experiments suggested that a sequence of adsorption and photodegradation is responsible for discoloration of dye solutions. These results suggest that such hydroxyapatite/titania nanocomposites constitute attractive low-cost materials for the removal of dyes from industrial textile effluent.

Preparation of SiOC/HfO2 fibers from silicon alkoxides and tetrachloride hafnium by a sol–gel process

This study presents fabrication and characterization of novel SiOC/HfO2 fibers by a sol–gel process. Polyhafnosiloxane (PHfSO) fibers have been drawn from silicon alkoxide solution consisting of tetraethoxylsilane (TEOS) and dimethyldiethoxylsilane (DMDES) using tetrachloride hafnium (HfCl4) as hafnium source. The spinnability of the solution has been optimized by varying the amount of HfCl4 and H2O. The Hf incorporation is confirmed by the formation of Hf–O–Si bridge through co-condensation of HfCl4, TEOS and DEDES. Subsequent pyrolysis treatment of the PHfSO gel fibers yields dense SiOC/HfO2 fibers with high ceramic yield of 81wt%. The SiOC/HfO2 fibers exhibit good thermal stability up to 1500°C and mechanical property with tensile strength of 930MPa.

Combined sol–gel and carbothermal synthesis of ZrC–TiC powders for composites

The TiC–ZrC binary compound of nanostructured powders was synthesised by combination of sol–gel and carbothermal reduction. The polymeric precursor of the blend was produced by sol–gel process from titanium tetrabutoxide, zirconium tetrabutoxide and benzene-1.4-diol; then carbothermally reduced to the TiC–ZrC blend at 1600 °C in an inert environment. The chemical reactions occurring in the system were monitored by infrared spectrometry. Stable alkoxide solution was obtained by adding acetylacetone to avoid premature gelation of the metal alkoxide mixture. A solid solution of ZrTiC2 was produced by spark plasma sintering at temperature of 2000 °C.

Synthesis of Crack-Free PZT thin Films by Sol-gel Processing on Glass Substrate

PZT thin films deposited on glass substrates have been proposed for many applications such as adjustable optics in future X-ray telescopes. Sol-gel method is widely utilized to prepare PZT thin films due to its low reaction temperature, uniform mixing of reactants, and precise control of component. Crack-free transparent PZT thin films were prepared by dip-coating the solutions of complex alkoxides. PZT thin films were calcined at various temperatures and characterized by X-ray diffraction, field emission scanning electron microscopy to examine the surface morphology, and FT-IR spectroscopy. The XRD analysis confirmed the formation of perovskite phase at 600°C. FE-SEM results showed nucleation of PZT perovskite phase. Furthermore, the average grain size was measured in the range of 55 to 190nm.