Sol‐Gel Synthesis of Polycrystalline ZnO and ZnS Fibers

ZnO fibers with wurtzite structure have been prepared by a sol‐gel method using zinc nitrate hexahydrate and glucose as starting materials. The ZnO fibers with the diameter in the order of 3–5 µm are composed of ZnO nanoparticles with the size of 40～100 nm. The evolution of gel fibers to ZnO fibers was characterized by TG, XRD, FT‐IR, TEM, and SEM techniques in details. In addition, the transformation of ZnO fibers to ZnS fibers also was investigated.     

Preparation of ZnFe2O4 Nanofibers by Sol‐Gel Related Electrospinning Method

Zinc ferrite gel fibers were prepared from the sol precursor by the electrospinning method, and the ZnFe₂O₄ polycrystalline nanofibers were obtained upon calcination of the gel fibers. The obtained ZnFe₂O₄ nanofibers composed of 20–30 nm nanocrystals were about one hundred to several hundred nanometers in diameter. The materials have been characterized by means of SEM, TEM, XRD, TGA, and IR techniques.     

Preparation of Pt／C Catalyst with a New and Simple Organic Sol Method

It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.     

Sol‐Gel Related Solvothermal Procedure to Prepare Iron Oxide Fibers

A sol‐gel‐related solvothermal process is developed to prepare iron oxide fibers. Continuous iron oxide gel fiber was drawn from spinnable sol using ferric alkoxide as the precursor, and hollow hematite fiber was obtained after the gel fiber was treated by hydroncarbon thermal reaction. The as‐prepared hollow fiber was several millimeters in length, 4～15 µm in outer diameter, and ～3 µm in wall thickness. Substituting the hydrocarbon with triethylamide, Fe₃O₄ solid fiber composed of nanorods can be obtained. Incubated at 200°C in air for only 1 hour, Fe₃O₄ was oxidated to γ‐Fe₂O₃ fiber. Possible mechanisms involved in formation of these nanostructured iron oxide fibers also are discussed.     

Preparation of Silica-Gel Film with pH Indicators by the Sol–Gel Method

Gel films with various pH indicators were prepared by the sol–gel method without catalysts. The obtained gel films showed good response for various pH solutions as optical pH sensors and no leaching of the indicators was observed. The feature of absorption spectra of the indicators in the gel films was almost the same as that in the aqueous solutions. pKa of the indicators in the gel films was shifted with the increase of the TMOS content in the starting solutions. These results suggest that the pH indicators in the gel films were trapped in similar environment as in the solutions.     

Preparation of Silicon Oxycarbide Glass Fibers by Sol-Gel Method—Effect of Starting Sol Composition on Tensile Strength of Fibers

Silicon oxycarbide (Si—O—C) glass fibers were prepared by heat-treating the gel fibers drawn from the solution containing tetra-ethyl-ortho-silicate (TEOS), tri-ethoxysilane (HTES) and methyl-tri-ethoxysilane (MTES) in the course of sol-gel reaction.The replacement of TEOS by HTES in the solution, with the molar ratio of MTES to total alkoxysilanes being kept constant at 1/3, resulted in remarkable improvement of tensile strength of the glass fibers prepared at 1300°C. The decrease in the content of free carbon was observed in such fibers, even by an amount as small as a few wt%, and was considered to be related to the suppression of devitrification of the fibers to form -SiC and to the enhancement of mechanical strength.     

Encapsulation of Bromothymol Blue pH‐Indicator into a Sol‐Gel Matrix

Transparent monolithic silica doping with bromothymol blue has been prepared by the acid catalyzed sol‐gel reaction of tetraethylorthosilicate in the presence of bromothymol blue. The immobilized bromothymol blue shows behavior similar to its solution counterpart. It retains its structure during the sol‐gel reactions in terms of response to pH. Polarized light microscopy has indicated that the bromothymol blue molecules are strongly interacted within the host silica network. The immobilization of bromothymol blue into sol‐gel matrix could be used as a solid indicator.     

Mesoporous Silica Supported Sulfated Zirconia Prepared by a Sol–Gel Process

Mesoporous silica-supported sulfated zirconia aerogels with different Zr/Si and S/Zr molar ratios were prepared using a one-step preparation. The characterization of these solids was conducted using N₂ physisorption at 77 K, X-ray diffraction, mass spectrometry, and sulfur chemical analysis. The isomerization of n-Hexane was used as a catalytic test. Highly improved textural properties were obtained for these solids, and two types of mesopores were observed. Depending on the zirconium content, the size and amount of mesopores are highly affected. The importance of sulfates effectively bonded to Zr(IV) is elucidated, both for achieving high catalytic activity and for a good sulfur thermal stability. The catalytic activity (for a sample prepared with a particular S/Zr ratio) expressed per gram of Zr(IV) is comparable to that of pure sulfated zirconia.     

Encapsulation of Bromocresol Green pH Indicator into a Sol‐Gel Matrix

The bromocresol green pH indicator was encapsulated into transparent monolithic silica matrices using acid catalyzed sol‐gel reaction. Tetraethylorthosilicate was used for the entrapment of the bromocresol green indicator. The immobilized bromocresol green shows behavior similar to its solution counterpart. It retains its structure during the sol‐gel reactions in terms of response to pH and albumine. The polarized light microscopy has indicated that the bromocresol green molecules are strongly interacted within the host silica network.     

Effect of Synthesis Parameters on Sol–Gel Silica Modified by Zirconia

An experimental strategy was developed to obtain mesoporous SiO₂-ZrO₂ mixed oxides via a sol–gel process, which involved the use of tetraethylorthosilicate (TEOS) and an inorganic Zr-containing salt. The effects of key process parameters on the properties of the materials were investigated, including the choice of Zr(IV) source (zirconium oxychloride or nitrate), the ZrO₂ content and the synthesis pressure (i.e. ambient pressure or hydrothermal conditions). The resulting solids were dried, calcined at 500 °C, and characterized by nitrogen physisorption, pyridine chemisorption, ²⁹Si Nuclear Magnetic Resonance and X-ray diffraction. The data revealed that mesoporous materials with very narrow pore diameter distribution were obtained when using the autoclave procedure from both zirconium nitrate and oxychloride salts. The surface areas and pore size distributions were a function of ZrO₂ content. Differences in acidity, as determined by pyridine adsorption, were observed depending on the synthesis parameters.     

Preparation of Amorphous Silica-Alumina Using the Sol–Gel Method and its Reactivity for a Matrix in Catalytic Cracking

Amorphous silica-aluminas were prepared by the sol–gel method using organic templates such as carboxylic acid and the gel skeletal reinforcement method. Their reactivities as a matrix for the catalytic cracking were investigated. Malic acid (MA) was used as a catalyst for the sol–gel method, an organic template and a reagent for the dispersion of Al. When the ratio of MA/TEOS (tetraethoxysilane) increased from 0.22 to 1.22, surface area, pore volume and pore diameter increased and the mesopore was formed at 1.22. Their average BET pore diameters for 0.22 and 1.22 of MA/TEOS were 2.0 to 5.1 nm, respectively. Although conversions of n-dodecane were around 20% or less with single amorphous silica-aluminas, both single beta-zeolite and the mixed catalysts of zeolite and amorphous silica-aluminas showed much higher activity. Further, the mixed catalyst using silica-alumina with mesopore (MAT(MA122-5)) exhibited the higher ratio of multi-branched paraffin to single branched paraffin in the gasoline franction of products (C5–C11) than the mixed catalysts using silica-alumina with only micropore and silica with mesopore or single zeolite. In the gel skeletal reinforcement method, tetraethoxy orthosilicate (TEOS) was used as not only a precursor of silica but also an agent which reinforces the skeleton of silica-gel to prepare an aerogel and extremely large mesopores were formed for resultant silicas and silica-aluminas. When silica aerogel was reinforced by TEOS solution, the pore diameter and pore volume reached 30 nm and 3.1 cm³/g, respectively, in the N₂ adsorption measurement by the BJH method, indicating that most of pores for this silica consisted of mesopores. In catalytic clacking reaction of n-dodecane, the mixed catalyst prepared by beta-zeolite and silica-alumina with large mesopore exhibited not only the comparable activity to that for single zeolite but also the unique selectivity where large amounts of branched products were formed. When the catalyst beds of silica-alumina and zeolite were separated, the reference silica-alumina (ref.SA) → zeolite system exhibited the higher activity and the product selectivity close to those for MAT(ref.SA). It is likely that the primary cracking of n-dodecane on silica-alumina would occur to produce the primary cracked product which effectively reacted with zeolite and inhibited the coke formation by overcracking.     

Synthesize and Characterization of Ca2CuO3 Nanostructures via a Modified Sol–Gel Method Assisted by Hydrothermal Process

A sol–gel-hydrothermal method was used to prepare the highly homogeneous nanopowder of Ca₂CuO₃ ceramic with an average diameter of about 20–30?nm. In comparison with the conventional sol–gel process, this method caused the more purity product with smaller size of particle due to a high pressure and long reaction time. Photoluminescence measurement indicated that for Ca₂CuO₃ nanoparticles there are two emission peaks: one sharp band at about 400?nm and one broad visible emission band. The band gap energy of Ca₂CuO₃ nanoparticles has been estimated to be 3.09?eV that is far above the values reported earlier. The results showed that the morphology and particle size of the synthesized samples can be obviously affected by the reaction temperature and molar ratio (w) between citric acid and calcium nitrate. In this procedure, diethylene glycol monobutyl ether was used as both the solvent and the modest surfactant.     

Entrapment of pH Universal Indicator into Sol‐Gel Matrix

This study involves the behavior of universal indicator entrapped into the sol‐gel matrix. The encapsulation of universal indicator has been prepared by acid catalyzed sol‐gel reaction of tetraethylorthosilicate (TEOS) in the presence of universal indicator to produce transparent monolithic silica doping with universal indicator. The immobilized universal indicator pH‐indicator shows behavior similar to its solution counterpart. The UV/VIS spectra indicate that the universal indicator retains its structure during the sol‐gel reactions in terms of response to pH. The universal indicator can be regarded as uniformly distributed in the sol‐gel matrix. The use of SDS surfactant has positive effects on the immobilized universal indicator monolithic disk due to homogenizing the polymerizing system. This observation has been confirmed using polarized microscopy.     

A Simple Method for the Preparation of ZnO Prickly Spheres

The synthesis of ZnO prickly spheres using precipitation followed by heating treatment was investigated. Zn(OH)2 precursor was prepared by precipitation process using Zn(CH3COO)2-2H2O in mixed 1-propanol-water solvent. Sodium dodecyl sulfate (SDS) as the anionic surfactant was added to control the morphology. The size and structure of ZnO prickly spheres were studied using XRD, TEM and SEM. The results showed that the morphologies and size of the spheres strongly depended on the volume ratio of 1-propanol /water and molar ratio of SDS/Zn2+. ZnO prickly spheres composed of nanorods could be obtained, when the volume ratio of 1-propanol/water = 2:3 and the molar ratio of Zn2/SDS= 450:1.     

The Determination of Perphenazine by a New Simple Flow‐Injection Chemiluminescence Method

Abstract

A rapid and simple flow‐injection chemiluminescence (CL) method is described for the determination of perphenazine, which is based on the CL intensity that generated from the redox reaction of Ce (IV)-perphenazine in HNO₃ medium is proportional to the perphenazine concentration without any sensitizers. The proposed method allows the determination range within 1.0×10^?7–7.0 ×10^?5 g mL^?1 with a detection limit of 8.0×10^?8 g mL^?1, and it has been successfully applied to the determination of the perphenazine in pharmaceutical tablet compared well with the official method.     

Production of Zinc-Doped Yttrium Ferrite Nanopowders by the Sol–Gel Method

Zinc-doped yttrium orthoferrite nanocrystals having the perovskite structure were prepared by coprecipitation of yttrium, zinc, and iron hydroxides. The limiting zinc doping level of the yttrium ferrite to yield a ZnFe₂O₄ spinel second phase was determined. The yttrium orthoferrite particle size was found to be a nonmonotone function of dopant concentration. The specific magnetization of yttrium ferrite nanocrystals increases with increasing zinc doping level from 0.242 A m²/kg (in undoped YFeO₃) to 1.327 A m²/kg (the ratio (1–x)YFeO₃: xZn (x = 0.4)) at Т = 300 K in 1250-kA/m field. A zinc ferrite impurity in samples enhances the ferromagnetism of the material.     

Preparation of Homocitrate using a Modified Method

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Preparation of Microspheres by an Emulsification‐Condensation Method

Microspheres were prepared using N‐methylolurea‐dodecylamine conjugate (MU‐DOA), an emulsifiable and self‐condensaible oil. MU was prepared by reacting urea and formaldehyde at 70°C in alkali conditions and then conjugating it to DOA by a condensation reaction. The MU‐DOA conjugate was emulsified in distilled water without an emulsifier, and then the oil droplets were hardened to obtain microspheres by a self‐condensation reaction among methylols of the conjugate. The reactions of each step, e.g., the preparation of MU, the conjugation of MU and DOA, and the self‐condensation of emulsified oil, were confirmed by Fourier transform infrared (FTIR) spectra. On scanning electron microscopy (SEM), the microspheres formed by the self‐condensation of the emulsified MU‐DOA were shown as spherical and less than 30 µm in diameter. The phase transition temperatures of DOA, MU‐DOA, and MU‐DOA microspheres were 30.3°C, 21.1°C, and 20.1°C, respectively. The lower transition temperature of MU‐DOA is probably due to the bulky MU, which could reduce the intermolecular interaction of MU‐DOA. Zeta potentials of the microspheres decreased from positive to negative value as pH increased from 3.5 to 10.5. The deprotonation of the amines of MU‐DOA would be responsible for that result.     

Convenient Method for Preparation of Aza‐Crown Ethers

A convenient method for the preparation of peraza crown ethers in a one‐pot synthesis in the presence of KF/Al₂O₃ is presented.     

Preparation and Properties of Alginate/Water‐Soluble Chitin Blend Fibers

Water‐soluble chitin (half‐deacetylated chitin) was prepared from chitosan by N‐acetylation with acetic anhydride. Alginate/water‐soluble chitin blend fibers were prepared by spinning their mixture solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl₂ and ethanol. The structure and properties of the blend fibers were studied with the aids of infrared spectra (IR), X‐ray diffraction (XRD) and scanning electron microscopy (SEM). structure analysis indicated good miscibility existed between alginate and water‐soluble chitin, due to the strong interaction from the intermolecular hydrogen bonds and electrostatic interactions. Best values for the dry tensile strength and breaking elongation were obtained when the water‐soluble chitin content was 30 wt%. The wet tensile strength and breaking elongation decreased with the increase of water‐soluble chitin content. The introduction of water‐soluble chitin in the blend fiber can improve the water‐retention properties of the blend fiber compared to pure alginate fiber. The fibers treated with aqueous solution of silver nitrate have good antibacterial activity to Staphylococcus aureus.