Showing papers on "Sol-gel published in 2012"
TL;DR: The studied results indicate that the as-prepared CYS: Ce(3+), Mn(2+), Tb(3+) phosphors have good CL intensity and CIE color coordinate stability with a color-tunable emission crossing the whole white light region under low-voltage electron beam excitation.
Abstract: A series of Ca4Y6(SiO4)6O (CYS): Ce3+/Mn2+/Tb3+ oxyapatite phosphors were prepared via high-temperature solid-state reaction. Under UV excitation, there exist dual energy transfers (ET), i.e., Ce3+→Mn2+ and Ce3+→Tb3+ in the CYS: Ce3+, Mn2+, Tb3+ system and their emitting colors can be adjusted from blue to orange-red via ET of Ce3+→Mn2+ and from blue to green via ET of Ce3+→Tb3+, respectively. Moreover, a wide-range-tunable white light emission with high quantum yields (13%-30%) were obtained by precisely controlling the contents of Ce3+, Mn2+ and Tb3+ ions. On the other hand, the CL properties of CYS: Ce3+, Mn2+, Tb3+ phosphors have been investigated in detail. The studied results indicate that the as-prepared CYS: Ce3+, Mn2+, Tb3+ phosphors have good CL intensity and CIE color coordinate stability with a color-tunable emission crossing the whole white light region under low-voltage electron beam excitation. In general, the white light with varied hues has been obtained in Ce3+, Mn2+, and Tb3+-triactivat...
212 citations
TL;DR: The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.
Abstract: We report on the synthesis of poly(vinyl alcohol) (PVA)-silica hybrid nanofibers via sol-gel electrospinning. Silica is synthesized through acid catalysis of a silica precursor (tetraethyl orthosilicate (TEOS) in ethanol-water), and fibers are obtained by electrospinning a mixture of the silica precursor solution and aqueous PVA. A systematic investigation on how the amount of TEOS, the silica-PVA ratio, the aging time of the silica precursor mixture, and the solution rheology influence the fiber morphology is undertaken and reveals a composition window in which defect-free hybrid nanofibers with diameters as small as 150 nm are obtained. When soaked overnight in water, the hybrid fibers remain intact, essentially maintaining their morphology, even though PVA is soluble in water. We believe that mixing of the silica precursor and PVA in solution initiates the participation of the silica precursor in cross-linking of PVA so that its -OH group becomes unavailable for hydrogen bonding with water. FTIR analysis of the hybrids confirms the disappearance of the -OH peak typically shown by PVA, while formation of a bond between PVA and silica is indicated by the Si-O-C peak in the spectra of all the hybrids. The ability to form cross-linked nanofibers of PVA using thermally stable and relatively inert silica could broaden the scope of use of these materials in various technologies.
207 citations
TL;DR: A new family of surface-reactive organic-inorganic hybrid materials built from chitosan microspheres are described and discussed on the basis of their textural and structural properties, thermal and chemical stability and their performance in catalysis and adsorption.
Abstract: Recently, organic-inorganic hybrid materials have attracted tremendous attention thanks to their outstanding properties, their efficiency, versatility and their promising applications in a broad range of areas at the interface of chemistry and biology. This article deals with a new family of surface-reactive organic-inorganic hybrid materials built from chitosan microspheres. The gelation of chitosan (a renewable amino carbohydrate obtained by deacetylation of chitin) by pH inversion affords highly dispersed fibrillar networks shaped as self-standing microspheres. Nanocasting of sol-gel processable monomeric alkoxides inside these natural hydrocolloids and their subsequent CO(2) supercritical drying provide high-surface-area organic-inorganic hybrid materials. Examples including chitosan-SiO(2), chitosan-TiO(2), chitosan-redox-clusters and chitosan-clay-aerogel microspheres are described and discussed on the basis of their textural and structural properties, thermal and chemical stability and their performance in catalysis and adsorption.
144 citations
TL;DR: Tungsten oxide nanoparticles synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells had a good cycling stability and a cyclability up to more than 50,000 cycles with a degradation of 25%.
Abstract: Tungsten oxide nanoparticles were synthesized via a sol-gel route using metallic tungsten as precursor, and were printed on a flexible electrode using inkjet printing in order to build solid-state electrochromic cells. Several spectroscopic techniques were used to characterize and compare tungsten oxide particles obtained from different origins. FTIR, Raman and X-ray diffraction spectroscopic measurements showed that the sol-gel synthesis described here produces nanoparticles mainly in an amorphous state with hexagonal crystalline domains and allowed the analysis of the hydration extent of those nanoparticles. The size was measured combining dynamic light scattering, sedimentation, and microscopic techniques (AFM), showing a consistent size of about 200 nm. The tungsten oxide nanoparticles were used to produce an ink formulation for application in inkjet printing. Solid-state electrochromic devices were assembled at room temperature, without sintering the tungsten oxide printed films, showing excellent contrast between on/off states. Electrochemical characterization of those films is described using cyclic voltammetry. The devices were then tested through spectroelectrochemistry by Visible/NIR absorption spectroscopy (400-2200 nm range), showing a dual spectroscopic response depending on the applied voltage. This phenomenon is attributed to the presence of two different crystalline states in accordance with results obtained from the spectroscopic characterization of the nanoparticles. The electrochromic cells had a good cycling stability showing high reversibility and a cyclability up to more than 50,000 cycles with a degradation of 25%.
129 citations
TL;DR: In this article, the effects of Mg concentrations on microstructure, surface topography and optical properties of ZnO thin films have been measured by X-ray diffraction (XRD), atomic force microscope (AFM), UV-vis spectrophotometer, and fluorophotometer (FL), respectively.
123 citations
TL;DR: In this paper, transparent ZnO thin films were deposited by multi-step sol-gel method and the effect of sol concentration on structural, morphological and optical properties were investigated.
Abstract: The transparent Zinc Oxide (ZnO) thin films were deposited by multi-step sol-gel method and the effect of sol concentration on structural, morphological and optical properties were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize structures and morphologies of the as-deposited films. The crystallographic orientation of the ZnO films shows the preferred orientation of (002) that is along c-axis direction and the films were uniform and well adherent to the substrates. The grain size is in the range of 15.3~19.7 nm and the thickness in the range of 266~295 nm, both increase with zinc acetate concentration. It is found that the transmittance of the films is enhanced from 83 to 95% in the visible near- IR region in the range from 400 to 800 nm by increasing the concentration. The optical band gap energy attenuates from 3.307 to 3.227 eV and whereas the Urbach energies of the films increase from 68.2 to 82.4 meV with increasing the concentration from 0.35 M to 0.65 M.
Key words: Sol-Gel method, spin coating, structural properties, optical properties.
114 citations
TL;DR: In this paper, the effects of the Al concentration on the optical properties of zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method.
Abstract: Aluminium (Al)-doped zinc oxide (AZO) thin films with different Al concentrations were prepared by the solgel spin-coating method. Optical parameters such as the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity were studied in order to investigate the effects of the Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at infinite wavelength of the AZO thin films were found to be affected by Al incorporation. The optical conductivity of the AZO thin films also increases with increasing photon energy.
109 citations
TL;DR: Polydimethylsiloxane (PDMS)-silica ORMOSIL (organically modified silicate) sols were prepared by a one-pot sol-gel process using tetraethyl orthosilicate as an inorganic precursor and hydroxylterminated PDMS as an organic modifier, and antireflective (AR) coatings were prepared with these sols by dip coating.
Abstract: Polydimethylsiloxane (PDMS)–silica ORMOSIL (organically modified silicate) sols were prepared by a one-pot sol–gel process using tetraethyl orthosilicate as an inorganic precursor and hydroxyl-terminated PDMS as an organic modifier, and antireflective (AR) coatings were prepared with these sols by dip coating. It was found that the addition of PDMS to silica sols significantly increased the viscosity and the controllable viscosity range of the silica sols, affording us a simple route to prepare very thick AR coatings with controlled thickness by a single deposition step. The coated fused silica substrates retained very high transmission of up to 99.9% at a determined wavelength. The addition of PDMS to the silica sols improved the hydrophobicity and abrasion-resistance of the coating, and prevented to some extent the coating from cracking which occurred in a pure inorganic thick AR coating. The PDMS–silica ORMOSIL AR coatings are stable after standing for 2 months at room temperature in an environment of 95% relative humidity. The relationship between structure and properties of the coatings is discussed considering the particle growth mechanism.
96 citations
TL;DR: In this paper, the effect of annealing on the microsctructural and optoelectronic properties of titanium dioxide (TiO 2 ) thin films prepared using sol-gel method onto silicon (Si) (100) and quartz substrates was reported.
96 citations
TL;DR: In this paper, the structural and micro-structural properties of NiO films were studied by means of X-ray diffraction and field emission scanning electron microscopy, which showed that all the films are crystallized in the cubic phase and present a random orientation, and the surface morphology of the NiO film consists of nanocrystalline grains with uniform coverage of the substrate surface with randomly oriented morphology.
94 citations
TL;DR: In this article, the effects of aluminum dopant on the crystalline structure and orientation of the ZnO films have been investigated by X-ray diffraction (XRD) study.
TL;DR: In this article, the influence of zinc concentration on the microstructure, crystal structure, surface wettability, surface roughness, and antibacterial property of zinc-substituted cobalt ferrite nanopowders was investigated systematically.
Abstract: Zinc-substituted cobalt ferrite nanopowders were prepared via a sol-gel route using citric acid as a chelating agent. The influence of zinc concentration on the microstructure, crystal structure, surface wettability, surface roughness, and antibacterial property of zinc-substituted cobalt ferrite nanopowders was investigated systematically. The substitution of zinc influences slightly the microstructure, surface wettability, surface roughness, and crystal structure but strongly affects the antibacterial property of the cobalt ferrite nanopowders.
TL;DR: In this paper, the antibacterial activity studies of synthesized composites films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectrogrammy (FT-IR), and UV-vis diffuse reflectance spectrography (DRS).
TL;DR: In this article, the dependence of structural and optical properties of ZnO thin films on sol concentrations was deeply investigated, and the results showed that low sol concentration is favorable for obtaining high c-axis oriented ZnOs with good crystalline quality.
TL;DR: In this paper, the formation of metal aluminate nanoparticles and their particle size were found to depend upon the calcination temperature, which was much lower than that required for its preparation through solid state reactions.
TL;DR: In this paper, WO 3 -Cr 2 O 3 semiconducting thin films were prepared by sol-gel method by using field emission scanning electron microscopy (FEM) and X-ray diffraction.
TL;DR: In this article, various iron-based polycrystalline monoliths, Fe3O4, iron, and Fe3C, with hierarchically distributed pores have been synthesized from ionic precursors using a sol-gel process accompanied by phase separation.
Abstract: Various iron-based polycrystalline monoliths, Fe3O4, iron, and Fe3C, with hierarchically distributed pores have been synthesized from ionic precursors using a sol–gel process accompanied by phase separation. Propylene oxide acts as a proton scavenger to increase pH moderately and uniformly in a reaction solution, which leads to homogeneous gelation. On the other hand, poly(acrylamide) works as a phase separation inducer as well as a precipitation inhibitor. Appropriate choice of iron precursor, solvent, polymer, and epoxide allowed the formation of iron(III)-based xerogels with cocontinuous macroporous structures. The dried gels were amorphous, whereas heating in air above 300 °C led to the formation of α-Fe2O3. Calcination under an inert condition above 400 °C formed Fe3O4, iron, and Fe3C without collapse of macrostructures. Examination has been carried out using SEM, TG-DTA, FT-IR, Hg intrusion, pH measurement, X-ray diffraction, and N2 adsorption–desorption.
TL;DR: In this article, silicon carbide nanopowders and nanowhiskers were synthesized using phenolic resin and silicon alkoxide as precursors through sol-gel process with atomic ratio of C/Si = 1.8 in water-solvent-catalyst-dispersant system.
TL;DR: In this paper, cobalt-based metal oxide thin films (MxCoyOz with M = Mn, Cu, Ni) have been deposited on commercial aluminum and glass substrates using sol-gel dip-coating method.
Abstract: New cobalt-based metal oxide thin films (MxCoyOz with M = Mn, Cu, Ni) have been deposited on commercial aluminum and glass substrates using sol–gel dip-coating method. The as-deposited films were characterized by a wide range of complementary techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), spectrophotometry and nanoindentation techniques. A light absorption study for coatings on glass substrates within a wavelength range of 300–1100 nm was also conducted. Topographical and morphological investigations showed the presence of nano-sized, grain-like particles in the copper–cobalt oxide coatings, which consequently had the roughest surface among the three coatings. All coatings on glass substrate exhibited higher absorption of ultraviolet (UV) light compared to visible light, while coatings on aluminum substrate generally had low reflectance (< 50%) of UV light, moderate reflectance (< 80%) of visible light and high reflectance (up to 100%) of infrared light. Implications of optical properties as a function of film thickness controlled by dip-heating cycles were discussed. The elastic modulus (E) and hardness (H) of thin film samples compared with stand‐alone commercial aluminum substrate were also measured.
TL;DR: In this article, transparent conductive CuFeO2 thin films were deposited onto a quartz substrate using a low-cost sol-gel process and sequential annealing in N2.
TL;DR: In this paper, Nanocrystalline sulfated zirconia powder was prepared by a non-alkoxide sol-gel route using acidic condition (pH 1-2).
TL;DR: In this paper, the complex sol-gel technique is applied to the preparation of Mg-Zr-doped LiCoO2 cobaltites, which results in composite powders in which the cathodic material is intimately mixed with inactive metal oxides as Co3O4, MgO and ZrO2.
TL;DR: In this article, a polycrystalline ferroelectric lead-free (Bi 0.5 Na 0.95 Ba 0.05 TiO 3 (BNT-NT0.05 ) thin films have been deposited on Pt/TiO 2/SiO 2 /Si substrates by an optimized sol-gel/spin-coating process.
TL;DR: The final result is a solid-state electrochromic cell showing excellent contrast between the redox states, giving rise to colors such as yellow, green, or blue.
Abstract: Vanadium oxide gel was synthesized and formulated for the assembly of solid-state electrochromic cells on flexible and transparent electrodes using inkjet printing. FTIR, Raman, and X-ray diffraction spectroscopic measurements showed that the vanadium oxide gel here synthesized consisted of V2O5·6H2O, microstructures similar to orthorhombic V2O5, while Raman spectroscopy also shows the presence of amorphous domains. Atomic force microscopy (AFM) images of the thin films printed using an inkjet shows a ribbonlike structure, which is in accordance with previous results of the vanadium oxide gels in solution. Solid-state electrochromic devices were assembled at room temperature using the inkjet printed films, without any sinterization step. The electrochemical properties of the vanadium oxide gel were characterized by cyclic voltammetry and spectroelectrochemistry by visible/NIR absorption spectroscopy (in both liquid and solid-state). Several redox steps are observed, which gives rise to a variety of color ...
TL;DR: In this paper, a conduction mechanism was proposed to explain the origin of giant dielectric constant in CCTO system, which was found that the main weight-loss and decomposition of precursors occurred below 450°C and the complex perovskite phase appeared when the calcination temperature was higher than 700°C.
TL;DR: Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective coatings were prepared by the reaction of MgCl2 with HF as discussed by the authors.
Abstract: Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective coatings were prepared by the reaction of MgCl2 with HF. The formation and crystallisation of MgF2 nanoparticles were followed by 19F NMR spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) in the liquid phase. The crystallization of the resulting films was monitored by XRD experiments. At temperatures exceeding 550 °C the film material and glass substrates undergo a chemical reaction, MgO is formed and SiF4 evaporates as a volatile product. Microstructure and optical properties were characterized as a function of the annealing temperature. The mechanical stability of MgF2 films was evaluated by the Crockmeter test using both felt and steel wool. It is shown that porous MgF2 films prepared by this synthesis have a vast potential for the large-area processing of antireflective coatings.
TL;DR: In this article, the main aspects of the sol-gel synthesis of ZnO thin films were critically examined with particular reference to the optimization of the process parameters that influence specific properties of the films, such as the transparency, the crystallization behavior and the electrical resistivity.
TL;DR: In this paper, the effect of aging times and temperatures on physical and chemical properties of TiO 2 sol particles was systematically investigated, and the results showed that the crystallinity and average particle size of the TiO2 sol particles can be successfully controlled by adjusting the aging time and temperature.
TL;DR: In this paper, thin films of the mixed ZnO-SnO 2 system were obtained by employing the sol-gel technique, starting from the mixture of zinc oxide and tin oxide precursor solutions.
Abstract: Thin films of the mixed ZnO–SnO 2 system were obtained by employing the sol–gel technique, starting from the mixture of zinc oxide and tin oxide precursor solutions. The tin atomic concentration percentages ( X ) in the precursor solutions with respect to the ZnO + SnO 2 total growing solution were: 0, 10, 20, 30, 40 and 100 at.%, here, the ZnO atomic percentage is (100– X ). The films were deposited by the dip coating method on glass substrates and were sintered at 450, 500 and 550 °C, in an open atmosphere. The X-ray diffraction patterns show the presence of zinc oxide and tin oxide crystals. The optical properties of the films were studied by UV–vis spectroscopy. The photocatalytic activity was quantified by means of the bleaching of methylene blue. The films of the mixed ZnO–SnO 2 system show higher photocatalytic activity than the SnO 2 and ZnO films.
TL;DR: In this paper, submicron bioactive glass particles were synthesized by a sol-gel process and were then coated on a 316L stainless steel substrate using an electrophoretic deposition (EPD) technique.