Synthesis of monodispersed lithium silicate particles using the sol–gel method

Lithium silicate particles were prepared by the sol–gel process based on the Stöber method using tetraethoxysilane and lithium ethoxide as starting materials; lithium dodecyl sulfate (LDS) was used as a surfactant. Lithium ion concentration of the obtained particles increased with an increase of Li/Si ratios from 1 to 4. Scanning electron microscope images showed that the obtained particles were rather monodispersed with diameter of 100–300 nm, and the particle size was not influenced by the amount of added LDS but the Li/Si ratios. Fourier-transform infrared spectra of the particles showed that the intensity of the peaks due to CO₃ ^2? increased with an increase of the Li/Si ratios. X-ray diffraction patterns and ²⁹Si magic-angle spinning-nuclear magnetic resonance spectra of the particles indicated that Q₃ and Q₂ units were present as amorphous state in the particles prepared with Li/Si ratios of 1 and 2, respectively. In the case of Li/Si ratios of more than 3, lithium metasilicate crystals formed, and Q₁ and Q₂ units were dominant.     

Synthesis of polyferromethylsiloxane sorbents using a sol–gel method

Trivalent iron complexes which could be easily converted into materials are formed by the reaction of FeCl₃ with K₃[O₃SiMe] in a highly concentrated aqueous alkaline solution. The presence of the liquid glass as an additive and decreasing the pH results in solutions that give rise to homogeneous gels. Polycondensation proceeds very rapidly in the higher pH range (viz. pH 9–10) and substantially slower in an acidic medium (pH 2–3). Xerogels were obtained having microporous structure after treatment of polyferromethylsiloxane gels obtained from acidic medium or mesoporous structure when obtained from alkaline medium.     

Synthesis of mesoporous hydrophobic silica microspheres through a modified sol–emulsion–gel process

Mesoporous silica microspheres were synthesised through a sol–emulsion–gel process using Span 80 as the surfactant in silica sol/n-hexane water in oil emulsion system. Surface modification of the microspheres was done with trimethylchlorosilane to obtain hydrophobic silica microspheres. Various parameters related to the synthesis of microspheres, including concentration of surfactant and viscosities of sol were studied. The hydrophobicity (wettability), thermal stability, porosity, and morphological features were also investigated.     

Deposition of silica thin films formed by sol–gel method

Deposition of silica thin films on silicon wafer was investigated by in situ mass measurements with a microbalance configured for dip coating. Mass change was recorded with respect to deposition time when the substrate was fully immersed in the silica sol. Mass gain during deposition was higher than predicted from monolayer coverage of silica nano particles. This implied that deposition was facilitated by gelling of the nanoparticles on the substrate. The rate of deposition was enhanced by increasing the particle concentration in the sol and by decreasing the particle size from 12 to 5 nm. Increasing the salt concentration of the silica sol at constant pH enhanced the deposition of the silica particles. Reducing the pH of the sol from 10 to 6 decreased the deposition rate due to aggregation of the primary silica particles.     

Synthesis of SnO2 nanostructures by ultrasonic-assisted sol–gel method

Fluorine doped SnO₂ nanostructures were grown using ultrasonic assisted sol–gel method. The gel was obtained by dissolving stannous chloride in methanol with ammonium fluoride as dopant followed by irradiation with ultrasonic vibrations. Obtained samples were characterized by structural, morphological and optical studies. All the peaks in the X-ray diffractograms are identified and indexed as tetragonal cassiterite structure. Negative slope of Williamson–Hall plots indicates compressive strain. Particle size of SnO₂ nanostructures is decreases with increases in concentration of fluorine doping. Atomic force microscopy, scanning electron microscopy and transmission electron microscopy studies confirm the formation of ring like porous structures and then hollow tube like growth with increase in the fluorine concentration. Peaks in Raman spectra also indicate strong confinement in SnO₂ particles. Distinct peaks in the PL spectra make the structure suitable for photovoltaic applications.     

Crystallization of inorganic silica based on interaction between polyimide and silica by sol–gel method

Crystalline silica in cristobalite phase was successfully prepared at a relatively low temperature of 800 °C by calcinating polyimide/silica hybrid films under ambient air. X-ray photoelectron spectroscopy measurements show that the product is silica after calcination. It is found that the crystallinity is dependent on the removing rate and the strength of the interaction between polyimide and silica. The presence of polyimide plays an important role in the growth of silica. Calcination to remove polyimide with rapid heating results in lower crystallinity compared with calcination with slow heating. For samples with the same content of silica, the crystallinity changes with the strength of the interaction between polyimide and silica molecules.     

Synthesis and characterization of silica xerogels obtained via fast sol–gel process

The synthesis and physical properties of high surface area silica xerogels obtained by a two-step sol–gel process in the absence of supercritical conditions are reported. The hydrolysis and condensation reactions were followed by infrared spectroscopy. The increment in the bands corresponding to silanol and hydroxyl groups suggests that the hydrolysis reaction was complete during the first 30 min. The effect on surface area and global reaction time under various reaction conditions, such as type of alkaline catalyst and solvents, water–monomer and solvent–monomer molar ratios, was also studied. The obtained results suggest that surface area was increased using 3-aminopropyltriethoxysilane as catalyst. The use of isopropyl alcohol as solvent promotes the reduction of the capillary stress, giving a well-structured xerogel. As a conclusion, with H₂O/i-PrOH/TEOS in a molar ratio of 10:4:1, it was possible to obtain silica xerogels with surface areas about 1,240 m²/g. Such surface areas are comparable with those obtained under supercritical conditions (aerogels), and higher than those xerogels conventionally obtained under normal condition (500–800 m²/g).     

Synthesis and characterization of nanostructured aluminum borate by sol–gel method

Nanostructured aluminum borate was synthesized using sol?Cgel technique. X-ray diffraction study revealed that the synthesized aluminum borate was single crystal. These nanorods have very uniform diameter. High-resolution transmission electron microscope images indicate that aluminum borate is well crystallized. The alternating current (AC) conductivity of the aluminum borate was studied as a function of temperature and frequency. The AC conductivity mechanism of the aluminum borate was found to be proportional to ??^s. The exponent s is almost independent with temperature. This suggests that AC conductivity mechanism of the aluminum borate can be interpreted by localized hopping model.     

Synthesis of nanostructural Yttrium fluorosilicate glass ceramic via sol–gel method

Journal of Sol-Gel Science and Technology - The yttrium fluorosilicate glass ceramic pieces were prepared by sol–gel method starting from yttrium acetate, trifluoroacetic acid, and...     

Synthesis and characterization of lead oxide nano-powders by sol–gel method

Our goal in this research was to obtain lead oxide nano-powders by sol–gel method. In this method, lead oxide nano-powders were synthesized through the reaction of citric acid (C₆H₇O₈·H₂O) solution and lead acetate [Pb(C₂H₃O₂)₂] solution as stabilizer and precursor, respectively. The effect of different parameters including calcination temperature, (molar ratio of citric acid to lead acetate) and drying conditions were investigated. The prepared lead oxide nano-powders were characterized by FT-IR spectroscopy, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The prepared PbO samples consist of the particles in the range of 50–120 nm or the thick plate like structures with thickness of 53 nm depending on the drying conditions.     

Synthesis and characterization of nanocrystalline tin oxide by sol–gel method

Nanocrystalline SnO₂ particles have been synthesized by a sol–gel method from the very simple starting material granulated tin. The synthesis leads a sol–gel process when citric acid is introduced in the solution obtained by dissolving granulated tin in HNO₃. Citric acid has a great effect on stabilizing the precursor solution, and slows down the hydrolysis and condensation processes. The obtained SnO₂ particles range from 2.8 to 5.1 nm in size and 289–143 m² g⁻¹ in specific surface area when the gel is heat treated at different temperatures. The particles show a lattice expansion with the reduction in particle size. With the absence of citric acid, the precursor hydrolyzes and condenses in an uncontrollable manner and the obtained SnO₂ nanocrystallites are comparatively larger in size and broader in size distribution. The nanocrystallites have been characterized by means of TG-DSC, FT-IR, XRD, BET and TEM.     

Synthesis of a dysprosium aluminum garnet nanopowder via sol–gel method

A dysprosium aluminum garnet (DAG) nanopowder was synthesized by aqueous sol–gel method using Al powder, HCl and Dy(CH₃COO)₃·4H₂O as raw materials. The dried amorphous gel was heat treated in the range of 800–1,200 °C. The influence of heat treatment on crystallization and phase transformation of the dried gel was investigated using X-ray diffractometery, scanning electron microscopy, thermogravimetry and differential thermal analysis and Fourier transform infrared spectroscopy. It was shown that the gel calcined from 900 to 1,200 °C resulted in the formation of a crystalline DAG nanopowder with particle size distribution ranges from 26 to 98 nm.     

Synthesis of superhydrophobic fluoro-containing silica sol coatings for cotton textile by one-step sol–gel process

Journal of Sol-Gel Science and Technology - Superhydrophobic coatings were successfully fabricated on cotton textiles through a simple one-step sol–gel process. A fluorinated copolymer...     

Structure and transmittance behavior of sol–gel silica nanoparticles synthesized using pH-stable alkanolamines

Journal of Sol-Gel Science and Technology - Although sol–gel silica nanoparticles are widely used in academic and industrial applications, only a few studies have focused on amine catalysts...     

Synthesis and sol–gel assembly of nanophosphors

Some recent works made in our group on inorganic nanophosphors are briefly reviewed in this paper. We first present the synthesis of highly concentrated semiconductor quantum dot colloids allowing the extension of the well-known oxide sol–gel process to chalcogenide compounds. Secondly, we show the synthesis and the chemical functionalization of lanthanide-doped insulator nanoparticles. In particular, the annealing process of these particles at high temperature leads to highly bright nanocrystals, which can be used as biological luminescent labels or for integration in transparent luminescent coatings. Finally, we consider luminescent transition metal clusters, which combine the inorganic structure of nanoparticles with the monodispersity and the easy functionalization of the organic molecules. Emphasis is put on the original thermochromic luminescence properties of copper iodide clusters trapped in siloxane-based films.     

Synthesis of titanium dioxide nano-powder via sol–gel method at ambient temperature

Titanium dioxide is a semiconductor with excellent photo catalytic properties and an important material with high regarded in nanotechnology. In this study, titanium dioxide nanoparticles was successfully synthesized via sol–gel method using tetra-n-butyl orthotitanate, hydrochloric acid and ammonia. Tetra-n-butyl orthotitanate was used as precursor. The ingredients were mixed at ambient temperature for 9 h on a magnetic stirring, sol was formed and converted to gel by adding ammonia. X-ray diffraction analysis clearly showed anatase and rutile phases so that, with increasing calcination temperature anatase converts to the rutile. Scanning electron microscopy was used for agglomerate observations. Energy-dispersive detector analysis was carried out and confirmed the formation of titanium dioxide. The influences of calcination temperature and pH value on particles size were studied. The results indicate that synthesis at room temperature reduced the particle size to 15 nm.     

Preparation of Cyanex 272-containing silica composite by sol–gel method for neodymium adsorption

A kind of silica composite containing bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) was prepared via a in situ sol–gel approach. ³¹P solid-state NMR and FT–IR spectra were employed to analyze the structure of the composite. The thermal stability and surface properties were characterized, and the adsorption ability towards trivalent neodymium (Nd(III)) was evaluated by batch experiments. The Cyanex 272 loaded silica composite showed the advantage of an effective adsorption of Nd(III) from low acidic or neutral solutions with a capacity of ~50 mg/g. The influence of contact time, acidity and initial metal concentration of the stock solutions on the adsorption were comprehensively investigated.