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We report a novel and inexpensive fabrication process of multiferroic nanocomposite via liquid phase using an anodic alumina template. The sol-gel spin-coating technique was used to coat the template with ferrimagnetic CoFe2O4. By dissolving the template with NaOH aqueous solution, a unique nanotube array structure of CoFe2O4 was obtained. The CoFe2O4 nanotube arrays were filled with, and sandwiched in, ferroelectric BaTiO3 layers by a sol-gel spin-coating method to obtain the composite. Its multiferroicity was confirmed by measuring the magnetic and dielectric hysteresis loops. [ABSTRACT FROM AUTHOR]

SUMMARY Well-aligned zinc oxide (ZnO) nanorod arrays were formed on indium tin oxide (ITO)/glass substrates via a low-temperature hydrothermal growth of a sol-gel-derived seed layer. The seed layer was heat treated at 300 °C for 10 min prior to the hydrothermal growth using optimized conditions from our previous work to form well-aligned ZnO nanorod arrays. Hydrothermal growth time was varied for 4, 8, 12 and 24 h. Flat-top hexagonal ZnO nanorod arrays were obtained, and the length of the ZnO nanorods formed increased from approximately 150 nm after 4 h to approximately 2 µm after 24 h using a single reactive bath. X-ray diffraction patterns showed predominant ZnO peak at (002) plane for all the samples. Photoluminescence spectra of the ZnO nanorod arrays showed peaks at ultra-violet and green region, which indicated good crystalline crystal formation containing oxygen-related defects. Raman scattering results obtained showed strong band at 438 cm−1 that correlated to E2 non-polar hexagonal wurtzite phase. Dye-sensitized solar cells (DSSC) based on the well-aligned ZnO nanorod arrays were fabricated. The maximum conversion efficiency of 0.22% was achieved for the nanorods formed after a prolonged hydrothermal time of 24 h. The conversion efficiency of the DSSC increased with hydrothermal exposure time as longer ZnO nanorods provided larger surface for dye adsorption to generate more electrons. Improved crystallinity of the ZnO nanorods provided at prolonged hydrothermal time also contributed to the higher conversion efficiency as the electron transportation was enhanced. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Titania nanosheet-precipitated coatings have been prepared by treating SiO2-TiO2 gel films on glass substrates with hot water at 90°C under vibration. Longitudinal vibrations at about 6 Hz during the treatment enhanced the formation of titania nanosheet. The titania nanosheet consisted of several layers with a spacing of about 0.6 nm and was identified as hydrated titania with a lepidocrocite-type structure. The morphology of the titania nanosheet-precipitated coatings is probably achieved by lowering of the concentration of hydrolyzed titania species at the surface due to rapid water flow driven by the vibrations. The coatings were transparent in the visible range and showed high photocatalytic activity and antifogging property. [ABSTRACT FROM AUTHOR]

In materials processing, the sol–gel method is one of the techniques that has enabled large-scale production at low cost in the past few decades. The versatility of the method has been proven as the fabrication of various materials ranging from metallic, inorganic, organic, and hybrid has been reported. In this review, a brief introduction of the sol–gel technique is provided and followed by a discussion of the significance of this method for materials processing and development leading to the creation of novel materials through sol–gel derived coatings. The controlled modification of sol–gel derived coatings and their respective applications are also described. Finally, current development and the outlook of the sol–gel method for the design and fabrication of nanomaterials in various fields are described. The emphasis is on the significant potential of the sol–gel method for the development of new, emerging technologies. [ABSTRACT FROM AUTHOR]

Abstract: We describe the preparation and characterization of zirconia (ZrO2) thin films via sol–gel route by spin-coating method. By utilizing alkoxides Zr[O(CH2)3CH3]4 in the presence of ethanol (EtOH), nitric acid and acetylacetone as a chelating agent, a stable sol of ZrO2 was obtained. Smooth surface morphology with nano-cracks was exhibited for all ZrO2 thin films being fabricated. The film thickness varied from 39 to 206nm depending on the molar ratio of EtOH during the sol preparation and also annealing temperature applied. All ZrO2 films possess high optical transmittance. Refractive index of the thin film was ranging from 1.6 to 2.4 depending on molar ratio of EtOH and annealing temperature. Tetragonal phase of ZrO2 was formed after annealed at 400°C. Crystallinity of ZrO2 was enhanced by increasing molar ratio of EtOH. Crystallite size of tetragonal ZrO2 was ranged from 3.0 to 9.9nm. A hot-water treatment reduced the film thickness and further improved crystallinity of the sol–gel derived oxide. [Copyright &y& Elsevier]

Superhydrophobic surfaces and electrowetting have found applications in many fields. Two of the most desired features in these applications are a robust surface and low voltage actuation electrowetting. A thermally and chemically robust nano-scale superhydrophobic surface was prepared using facile techniques of sol-gel and hot water treatment to obtain rough pseudoboehmite alumina structures; and layer-by-layer coating, using Nafion®, to achieve the hydrophobization. It exhibited a contact angle of 167.2 ± 0.8°; thermal stability of up to 300 °C; stability to acid, base, organic solvents and UV irradiation. Subsequently replacing Nafion® with 1H, 1H, 2H, 2H-perfluorodecyltrimethoxysilane and a conductive Au under layer coating, an extremely low voltage, 3 V, electrowetting and reversible electrowetting were achieved in air and dodecane media, respectively. [ABSTRACT FROM AUTHOR]

The morphological evolution of the zinc oxide (ZnO) nanostructures generated by hot-water treatment (HWT) of sol–gel derived coatings as a function of temperature from 30 to 90 °C was investigated. With increasing HWT temperature, the ZnO crystals evolved from nanoparticles to rod-like and needle-like nanostructures. High-resolution transmission electron microscope observations of rod-like and needle-like nanostructures generated at 60 and 90 °C indicated single crystal ZnO wurtzite structure was obtained. All the hot-water treated samples exhibited blue emission at approximately 440 nm in room temperature. The intensity of blue emission increased with higher HWT temperatures. The unique photoluminescence emission characteristic remained even after heat-treatment at 400 °C for 1 h. As the emission peak obtained in our work is approximately 440 nm (2.82 eV), the emission peak is corresponding to the electron transition from the interstitial Zn to the top of valence band. This facile formation of blue-emitting ZnO nanostructures at low-temperature can be utilized on substrate with low thermal stability for optoelectronic applications such as light emitting devices and biological fluorescence labeling. [ABSTRACT FROM AUTHOR]

Abstract: Rod-like undoped and Ce-doped ZnO nanostructures have been formed using hot-water treatment of the undoped and Ce-doped sol–gel derived layer at low temperature of 60°C for 30min on glass substrates. The concentration of Ce doping was varied from 2 to 20at% in the precursor films. Morphological structures and optical properties of the hot-water treated ZnO films were investigated and compared with those of the conventional, annealed ZnO films. The resultant undoped and Ce-doped rod-like ZnO films showed ultraviolet (UV) and strong blue emissions. The photoluminescence of the Ce-doped films exhibited blue shift in UV emission and reduced blue emission intensity, compared to pure ZnO due to the incorporation of Ce. Increment of broad green emission intensity is observed with increased Ce doping in the precursor concentration for the hot-water treated films, which indicates the formation in Ce vacancies. Ce-doped ZnO films obtained which show promising optical properties can be used for the fabrication of optoelectronics devices utilizing substrates with low thermal stability such as organic polymers. [Copyright &y& Elsevier]

Abstract: An inorganic–organic hybrid of phenylsilsesquioxane-silica (PhSiO3/2–SiO2) nanoparticle was prepared by sol–gel process, and a high proton-conducting electrolyte was synthesized by surface-sulfonation of phenyl groups of the particles. Chlorosulfonic acid was used as a sulfonation agent. The PhSiO3/2–SiO2 particles are chemically stable as well as flexible. The proton conductivity of the pelletized sample reached about 10−2 S/cm at 80 °C and 80% relative humidity (RH). The open circuit voltage (OCV) of the single cell prepared using the pelletized sample as an electrolyte for a H2-air fuel cell increased with increasing the RH of the cell. The maximum power density of ~40 mW/cm2 and OCV of 0.9 V was obtained at 80 °C and 95% RH. [Copyright &y& Elsevier]

Abstract: Thermally and chemically stable phenylsilsesquioxane (PhSiO3/2) particles were prepared by sol–gel process, and ultra-thin layers of oppositely charged poly(diallyldimethylammonium chloride) (PDDA) and dodecatungstophosphoric acid (WPA) were alternately deposited on the negative-charged PhSiO3/2 particles via layer-by-layer assembly technique. Hygroscopic property of WPA was remarkably reduced owing to the formation of PDDA/WPA complex. The amount of WPA adsorbed on PhSiO3/2 particles was estimated to be ∼0.03 (g/g PhSiO3/2). Transparent and monolithic pellet can be obtained from the resultant core–shell particles by pressing. Proton conductivity of WPA-deposited samples increased about 4 orders of magnitude compared with unmodified samples, and reached to about 10−4 S/cm at 80 °C and 80% relative humidity. [Copyright &y& Elsevier]

Abstract: Thermally and chemically stable proton conductors were prepared via surface-sulfonation of sol–gel-derived phenylsilsesquioxane–methylsilsesquioxane (PhSiO3/2–MeSiO3/2) particles in a range from 250 to 650 nm in diameter. MeSiO3/2 component was indispensable to improve the chemical durability against sulfonation solvent. Proton conductivity of the pelletized samples prepared using the sulfonated PhSiO3/2–MeSiO3/2 particles increased linearly with increasing the ion exchange capacity (IEC) of the particles. The mobility (μ) of proton was calculated to be 0.3×10−4 cm2/V s. Porous PhSiO3/2–MeSiO3/2 particles prepared using a cationic surfactant of cetyltrimethylammonium bromide (CTAB) as a template of pores showed higher both IEC and water uptake, leading to an increase in proton conductivity to ∼ 10−2 S/cm at 80 °C and 80% relative humidity. [Copyright &y& Elsevier]