Anodic electrodeposition of highly oriented zirconium phosphate and polyaniline-intercalated zirconium phosphate films

Films of highly oriented alpha-zirconium phosphate and polyaniline-intercalated zirconium phosphate with controllable thickness in the micrometer range were grown anodically on Pt electrodes. To optimize the electrodeposition conditions, the exfoliation of alpha-zirconium phosphate by tetrabutylammonium (TBA) salts was investigated in several nonaqueous solvents. Acetonitrile was found to be the best solvent for making crack-free, oriented films because of its high vapor pressure, low viscosity, and relatively high permittivity. With TBA salts of neutral or weakly acidic anions (TBACl, TBABr, TBAI, TBA(HSO4), or TBA(H2PO4)), full exfoliation did not occur and alpha-zirconium phosphate and/or polyaniline were deposited as rough films. With basic anions (TBAF or TBAOH), dense, adherent films were obtained. X-ray diffraction patterns of the films showed that they were highly oriented along the stacking axis. The thickness could be controlled, up to about 40 microm, by limiting the time of the electrodeposition reaction. At monomer concentrations below 1.0 x 10(-2) mol/dm3, the emeraldine form of the intercalated polymer was obtained. Electrodeposition thus provides a thick film alternative to layer-by-layer assembly for intercalation compounds of alpha-zirconium phosphate with a conducting polymer.     

Synthesis and photocatalytic properties of highly crystalline and ordered mesoporous TiO2 thin films

Highly crystalline and ordered mesoporous TiO2 thin films have been synthesized by stabilization of the mesostructure with confined carbon; the films exhibit 2.5% photoconversion efficiency for the water photolysis at zero-bias and Xe lamp illumination of 40 mW cm(-2).     

Synthesis of ultrahigh-density ordered arrays of metallic nickel nanowires in mesoporous silica films

Two-dimensional (2D) mesoporous silica films were employed as a template to fabricate ultrahigh-density ordered arrays of metallic nickel nanowires via electroless deposition.     

Highly ordered hybrid mesoporous bifunctional thin films

Highly ordered mixed framework mesoporous cubic (Im3m) thin films of (M(1-x)(Si-R)(x))O(2) bearing organic groups (M = Ti or Zr, R = propylamine, propylthiol or phenyl, x < or = 0.2) are obtained by one-pot dip-coating; a second organic function (R' = hexadecyl, phenyl, thiol) can be added by post-grafting with a molecule presenting a group capable to anchor to the M sites, thus leading to bifunctional accessible mesopores.     

Synthesis and characterization of highly ordered mesoporous thin films with -COOH terminated pore surfaces

Highly ordered mesoporous inorganic-organic hybrid thin films with covalently bonded carboxylic acid (-COOH) terminal groups on the pore surfaces were synthesized by evaporation induced self-assembly of tetraethoxysilane, organosilanes, and a nonionic surfactant followed by acid hydrolysis and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, surface acoustic wave (SAW) based N2 sorption, and thermogravimetric analysis (TGA) techniques.     

有序中孔纳米多晶TiO~2薄膜的Li^+嵌脱行为

以三嵌段高分子非离子表面活性剂为结构导向剂,在非水条件下,合成了具有均一孔径分布(6.5nm)、高比表面积的稳定的中孔纳米多晶TiO~2薄膜。用循环伏安与电位阶跃技术研究了薄膜的Li^+离子嵌入反应。结果表明,由非离子表面活性剂导向而成的中孔TiO~2薄膜具有较大的Li^+离子嵌入容量,伏安特性中双电层电容效应非常显著,Li^+离子在脱嵌过程中电荷传递系数在0.15～0.4之间,嵌入系数为(4.7～55)×10^-^1^2cm^2/s。这些结果显示了具有大的比表面中孔TiO~2薄膜具有不同一般Li^+离子嵌入TiO~2薄膜的电化学反应特征。     

Design and post-functionalisation of ordered mesoporous zirconia thin films

Bidimensional hexagonal or centred-rectangular mesoporous zirconia thin films have been reproducibly prepared by evaporation-induced self-assembly (EISA), which are stable up to 300 degrees C, with pore size around 35 A; the films can be post-functionalised with organic ligands presenting different functions, opening a land of opportunities for the design of new hybrid mesostructured materials, based on the synergy of a transition metal oxide network and organic groups.     

Synthesis of transparent and ordered mesoporous silica monolithic films embedded with monomeric zinc phthalocyanine dye

Monolithic transparent mesoporous silica films embedded with zinc phthalocyanine (ZnPc) have been synthesized and it is shown that the encapsulated ZnPc dye molecules exist predominantly in monomeric form.     

Synthesis and magnetic investigation of ordered mesoporous two-line ferrihydrite

We report here for the first time on the synthesis and characterization of ordered mesoporous two-line ferrihydrite. Ordered mesoporous ferrihydrite has been prepared via the nanocasting route. Two types of ordered mesoporous silica, two-dimensional hexagonal SBA-15 and three-dimensional cubic KIT-6, were employed as hard templates. The magnetic behavior of ferrihydrite replicas with an average diameter of about 7 nm was investigated by direct current magnetometry. The temperature dependence of magnetization shows a superparamagnetic transition around 70 K. Field-induced changes in the low-field behavior of the magnetization were observed below 30 K. The results are explained assuming a spin-glass-like state of the surface spins. The 2D hexagonal two-line ferrihydrite showed very large coercivity up to 1.6 kOe at 5 K.     

Synthesis and characterization of highly ordered functional mesoporous silica thin films with positively chargeable -NH2 groups

Highly ordered mesoporous organic-inorganic hybrid silica thin films with covalently bonded, positively chargeable -NH2 terminal groups were synthesized by evaporation induced self-assembly of tetraethoxysilane, 3-aminopropyl-triethoxysilane, and a nonionic surfactant under acid conditions and characterized using TEM, GISAXS, FTIR, SAW-based N2 sorption, and TGA.     

Textured films of chromium phosphate synthesized by low-temperature vapor diffusion catalysis

The application of kinetically controlled vapor diffusion catalysis to the synthesis of films of chromium phosphate produces a novel, nanostructured film morphology. The resulting material consists of a thin, flat backplane (3 μm thick) with needles of CrPO₄·6H₂O projecting from one surface of the film. The reaction process occurs at low temperature (25 °C) and mild pH.     

Synthesis of mesoporous aluminophosphate (AlPO) and investigation of zirconium incorporation into mesoporous AlPOs

Mesoporous aluminophosphate materials with variable amounts of zirconium have been synthesized at room temperature using a nonionic surfactant tri-block copolymer (PEO(20)PPO(70)PEO(20)) as the structure-directing agent. Powder X-ray diffraction of as-synthesized and calcined AlPO and ZrAlPO mesoporous materials shows a single broad peak near 2theta = 2.5 degrees, indicative of the average pore-pore correlation distance. Electron probe microanalysis shows that the ratio of P/Al in the powders is approximately 0.5, far lower than 1.0 for an ideal aluminophosphate framework. XRD, TEM, and N2 adsorption data indicate that the calcined samples consist of wormlike tubular materials having surface areas >350 m2/g and pores in the mesopore range. Electron spin resonance (ESR) studies of the gamma-irradiated and evacuated ZrAlPO samples show signals due to Zr3+ that increase with Zr content in addition to signals due to framework defects (i.e., V centers) and H atoms. The line shape and g values observed for Zr3+ are best explained as arising from a trivalent zirconium ion situated at the framework tetrahedral sites.     

Investigation of the properties of organically modified ordered mesoporous silica films

Organically modified, ordered mesoporous silica films, which can provide hydrophobicity and low polarizability to the framework, were prepared using Brij-76 block copolymer as a template. Due to a fast condensation reaction of the silica precursor, mesostructured silica films were not properly synthesized. To circumvent this problem, a synthesis procedure was modified to provide an enhancement of pore periodicity through the incorporation of methyl ligands on the framework. The micropore volume was reduced, and the pore size was enlarged, as the concentration of the methyl ligands on the framework was increased. A mesophase transition from a two-dimensional hexagonal structure to a body-centered cubic (BCC) structure was observed according to the concentration of incorporated methyl ligands. The mechanical properties of the fabricated films were investigated according to the pore ordering and film density. The mechanical properties of the films with random pore geometry show a positive correlation between film density and elastic modulus. Meanwhile, the mechanical behavior of organically modified mesoporous silica films with periodic pore distribution represents a negative correlation within a certain density range, which is advantageous to the low-k materials. Especially, film with a low micropore volume fraction and BCC pore ordering is more applicable to a low-k material due to low dielectric constant and high mechanical strength.     

Structural and optical properties of TiO2 thin films prepared by spin coating

Transparent semiconducting thin films of titanium oxide (TiO₂) were deposited on glass substrates by the sol–gel method and spin-coating technique. The physical properties of the prepared films were studied as a function of the number of spun-cast layers. The microstructure and surface morphology of the TiO₂ films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), with respect to the film thickness. The XRD analysis reveals that the films are polycrystalline with an anatase crystal structure and a preferred grain orientation in the (101) direction. The morphological properties were investigated by AFM, which shows a porous morphology structure for the films. The optical properties of the films were characterized by UV–Visible spectrophotometry, which shows that the films are highly transparent in the visible region and their transparency is slightly influenced by the film thickness, with an average value above 80 %. The dependence of the refractive index (n), extinction coefficient (k), and absorption coefficient (α) of the films on the wavelength was investigated. A shift in the optical band gap energy of the films from 3.75 to 3.54 eV, as a function of the film thickness, has been observed.     

Effect of annealing temperature on titania thin films prepared by spin coating

Essentially fully dense titania thin films were spin coated on fused quartz substrates under identical conditions and subjected to annealing over the range 750°–900°C. The films were of a consistent ~400 nm thickness. The anatase → rutile phase transformation temperature was between 750°C and 800°C, with first-order kinetics; annealing at 900°C yielded single-phase rutile. Silicon contamination from the fused quartz substrate was considered to be critical since it suppressed both titania grain growth (maintaining constant grain size) and the phase transformation (occurring at an unusually high temperature); its presence also was considered to be responsible for the formation of lattice defects, which decreased the transmittances and the band gaps.     

Synthesis and characterization of sol-gel zirconium phosphate with template surfactants by different methods

Long chain trimethylammonium salts can be successfully used as guest molecules to produce mesoporous layered materials when intercalated in sol-gel zirconium phosphate, an inorganic ion-exchanger. The obtained materials are very similar independently of the chain length and the synthesis method batch (B) or direct intercalation (DI). They show a good thermal stability, and a very high interlayer distance if compared with their precursor. By the thermal characterization it can be observed that the surfactant is lost in two or three steps depending on its position in the host. The layered structure with the expanded interlayer distance is maintained up to 300°C. From the IR spectra the different surfactant release models for (B) and (DI) are confirmed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Formation of ordered microphase-separated pattern during spin coating of ABC triblock copolymer

In this paper, the authors have systematically studied the microphase separation and crystallization during spin coating of an ABC triblock copolymer, polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO). The microphase separation of PS-b-P2VP-b-PEO and the crystallization of PEO blocks can be modulated by the types of the solvent and the substrate, the spinning speed, and the copolymer concentration. Ordered microphase-separated pattern, where PEO and P2VP blocks adsorbed to the substrate and PS blocks protrusions formed hexagonal dots above the P2VP domains, can only be obtained when PS-b-P2VP-b-PEO is dissolved in N,N-dimethylformamide and the films are spin coated onto the polar substrate, silicon wafers or mica. The mechanism of the formation of regular pattern by microphase separation is found to be mainly related to the inducement of the substrate (middle block P2VP wetting the polar substrate), the quick vanishment of the solvent during the early stage of the spin coating, and the slow evaporation of the remaining solvent during the subsequent stage. On the other hand, the probability of the crystallization of PEO blocks during spin coating decreases with the reduced film thickness. When the film thickness reaches a certain value (3.0 nm), the extensive crystallization of PEO is effectively prohibited and ordered microphase-separated pattern over large areas can be routinely prepared. When the film thickness exceeds another definite value (12.0 nm), the crystallization of PEO dominates the surface morphology. For films with thickness between these two values, microphase separation and crystallization can simultaneously occur.     

Mesoporous metal oxides by vapor infiltration and atomic layer deposition on ordered surfactant polymer films

Catalysis, chemical separations, and energy conversion devices often depend on well-defined mesoporous materials as supports or active component elements. Herein, we show that ordered assembled organic surfactant films can directly template porous inorganic solids with surface area exceeding 1000 m(2)/g by infusing the polymers with reactive inorganic vapors, followed by anneal. The specific surface area, pore size, chemical composition, and overall shape of the product material are tuned by choice of the polymer and precursor materials as well as the influsion and postinfusion treatment conditions. X-ray diffraction, infrared spectroscopy, and electron microscopy show that vapor infusion changes both the physical and chemical structure of the starting ordered polymer films, consistent with quantified trends in specific surface area and pore size distribution measured by nitrogen adsorption after film annealing. This method yields porous TiO(2) films, for example, that function as an anode layer in a dye-sensitized solar cell.     

Fabrication of ordered mesoporous thin films for optical waveguiding and interferometric chemical sensing

Planar optical waveguides with a propagation loss of 2.9 dB/cm at 633 nm were fabricated using ordered mesoporous thin films of TiO2-P2O5 nanocomposite deposited on the tin-rich surfaces of float glass slides. The resulting waveguides show substantial sensitivity to parts-per-million-level ammonia gas at room temperature on the basis of single-beam polarimetric interferometry.