Sol Gel Template Method Research Articles

Sol-gel template synthesis and photocatalytic behaviour of anatase titania nanoparticles

In this study, titania nanoparticles were successfully prepared by a sol-gel template method, employing cetyltrimethylammonium bromide (CTAB) and CaCO3 nanoparticles as templates. Titanium(IV) tetraisopropoxide and ethanol were used as a titanium precursor and alcoholic solvent, respectively. The obtained nanosized-titania was characterized by X-ray diffraction, transmission-electron microscopy, and N2 adsorption and desorption methods. The photocatalytic activity of titania was investigated from the photodegradation of methylene blue solution under UVC irradiation. The results indicated that the amount of anatase crystallites and pore characteristics were important factors influencing the degree of photocatalysis of titania nanoparticles. Highly crystalline anatase titania could be obtained through the controlled hydrolysis reaction rate and the formation of loose-packed titania nanoparticles, while high specific surface area could be achieved with a template method.

Application of synthesized mesoporous titania microspheres for arsenic [(III) and (V)] uptake studies

The present work describes the application of radiotracer technique for studying uptake of arsenic on titanium hydroxide, commercial titanium dioxide (TiO2) powder (anatase) and synthesized mesoporous titania beads in acidic, neutral, and alkaline conditions. Sol–gel templating method was used to prepare titania–polysaccharide composites, with different polymer contents. Mesoporous titania was obtained by heat treatment of the composite beads in a controlled environment. The synthesis process was optimized, using thermogravimetry analysis. X-ray diffraction patterns confirmed the formation of anatase pure phase titania (TiO2) at 700 °C in different environments, and scanning electron microscopy studies confirmed uniform pore size distribution. The effect of surface area, polymer content and pH on uptake of arsenic(III) and (V) on the synthesized titania beads was also investigated. Arsenic(V) was found to be retained quantitatively on the titania beads synthesized from 0.8% polymer content titania–polymer composite precursor in neutral to alkaline conditions. Details of the results obtained are discussed.

Effect of High Magnetic Field Annealing on Magnetic Properties of CoFe$_{2}$O$_{4}$ Nanowire Arrays

Cobalt ferrite (CoFe2O4) nanowire arrays with different diameters were prepared in porous anodic aluminum oxide (AAO) template by a sol-gel template method. A magnetic field annealing procedure was performed in the direction along wire axis (out of sample planes) at 600°C under 10-T applied magnetic field to orient the spinel CoFe2O4 crystalline. The morphology was studied by scanning electron and transmission electron microscope. X-ray diffraction (XRD) patterns show that samples performed by the magnetic field annealing procedure have a 〈110〉 texture along the nanowire axis, while those annealed without applied magnetic field show a nonoriented polycrystalline phase of spinel type structure. Vibration sample magnetometer (VSM) test shows the difference between CoFe2O4 nanowire arrays samples annealed with or without applied magnetic field. This difference shows the magneto-crystalline anisotropy with the easy magnetization direction along the nanowire axis, and is caused by the resultant effect of the easy magnetization direction distribution of the crystalline.

Effect of aspect ratio on microstructure and magnetic properties of spinel CoFe2O4 nanowire arrays

Cobalt ferrite (CoFe2O4) nanowire arrays with different diameters were prepared in porous anodic aluminum oxide (AAO) template by a sol-gel template method with the assistance of organic solvent and surfactant. The morphology was studied by scanning electron and transmission electron microscopy. A polycrystalline phase of spinel type structure was ascertained by X-ray diffraction (XRD) patterns. A magnetic test was performed using a physical property measurement system (PPMS), showing the uniaxial anisotropy with easy axis along the nanowire with an aspect ratio larger than 1000. A coercivity reduction from about 1500 Oe to about 800 Oe has been observed, while the diameter increases from 20 nm to 50 nm in this experiment. The cause of this has been discussed.

Structure and composition-dependent optical properties of (PbxSr1–x)TiO3 (x=0.4, 0.6) nanotube arrays

AbstractLead strontium titanate (PbxSr1–x)TiO3 (x=0.4, 0.6) nanotubes were synthesized by sol-gel template method via spin coating. The structures and morphology of the as-prepared samples were characterized by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. X-ray photoelectron spectroscopy was used to determine the chemical composition of the sample and the valence state of elements. Raman spectroscopy of the as-prepared (PbxSr1–x)TiO3 (x=0.4, 0.6) nanotubes at room temperature was also investigated. The results indicate that as-prepared (PbxSr1–x)TiO3 (x=0.4, 0.6) nanotubes are perfectly crystallized and there is a trend of structure change from PST40 to PST60. A weak peak at 508 cm−1 assigned to E(3TO) mode can be seen in the Raman spectrum of (Pb0.6Sr0.4)TiO3 sample. Photoluminescence spectra of samples at room temperature reveal three intense emission bands centered at 356, 400 nm for (Pb0.4Sr0.6)TiO3 and 413, 433, 451 nm for (Pb0.6Sr0.4)TiO3 nanotubes, respectively. The peak positions of the emission band have a significant blue shift as Pb content increases.

Synthesis and structural characterization of perovskite 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 nanotubes

We report the synthesis and structural characterization of 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 (PMN-PT) nanotubes prepared by a novel sol–gel template method. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 °C for 1 h) PMN-PT nanotubes were polycrystalline with perovskite crystal structure. The field emission scanning electron microscope (FE-SEM) shows that as prepared PMN-PT nanotubes were hollow with diameter to be about 200 nm. High resolution transmission electron microscope (HRTEM) analysis confirmed that the obtained PMN-PT nanotubes made up of nanoparticles (10–20 nm) which were randomly aligned in the nanotubes. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the stoichiometric 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3. The possible formation mechanism of PMN-PT nanotubes was proposed at the end.

Membrane solid phase microextraction with alumina hollow fiber on line coupled with ICP-OES for the determination of trace copper, manganese and nickel in environmental water samples

A novel alumina hollow fiber was synthesized by sol–gel template method and was characterized by scanning electron microscopy, N2 adsorption technique and X-ray diffraction. With the use of prepared alumina hollow fiber as extraction membrane, a new method of flow injection (FI)-membrane solid phase microextraction (MSPME) on-line coupled to inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for simultaneous determination of trace metals (Cu, Mn and Ni) in environmental water samples. The adsorption capacities of the alumina hollow fiber for Cu, Mn and Ni were found to be 6.6, 8.7 and 13.3mgg−1, respectively. With a preconcentration factor of 10, the limits of detection (LODs) for Cu, Mn and Ni were found to be 0.88, 0.61 and 0.38ngmL−1, respectively, and the relative standard deviations (RSDs) were ranging from 6.2 to 7.9% (n=7, c=10ngmL−1). To validate the accuracy, the proposed method was applied to the analysis of certified reference material GSBZ50009-88 environmental water and the determined values are in good agreement with the certified values. The developed method was also employed for the analysis of Yangtze River water and East Lake water, and the recoveries for the spiked samples were in the range of 87.4–110.2%.

Preparation of Bi0.85Nd0.15FeO3 Nanotube Arrays by a Sol–Gel Template Method

Bi0.85Nd0.15FeO3 (BNF) nanotube arrays were prepared by a sol–gel template method. The microstructure and phase were observed by scanning electron microscopy and transmission electron microscopy. Highly ordered nanotube arrays with BNF nanotubes of 200 nm diameter, 60 μm length, and 20 nm wall thickness were obtained. The BNF nanotube array capacitor showed ferroelectricity with a remanent polarization (2P r) of 68.7 μC/cm2 and a coercive electric field (2E c) of 141.9 kV/cm at frequency of 1000 Hz. The leakage current behavior of the BNF nanotube array was dominated by an ohmic conduction mechanism at E < 30 kV/cm and a space-charge-limited current mechanism at E = 30 kV/cm to 200 kV/cm.

On key factors for the fabrication of mesoporous tungsten oxide films from tungstic acid

Thermally stable mesoporous tungsten oxide films (TOFs) were prepared by surfactant templated sol–gel method using tungstic acid as tungsten oxide source. Influence of various experimental conditions on the obtained mesostructures was investigated, including the solvent compositions, addition of hydrogen peroxide, substrates, and aging time, heat treatment, etc. It has been found that the addition of hydrogen peroxide has a significant influence on the flexibility of formed meso-frameworks, and just a small amount can regenerate the degraded coating sol. TOFs were also found to crystallize on ITO coating easier than on bare glass, indicating that the different interactions with the substrates influence the crystallinity of obtained meso-structured TOFs. Film thickness can be adjusted by simply changing the solvent compositions while keeping mesostructures intact. This work clarified several key parameters in delivering well-defined mesostructured TOFs from cheap, moisture-insensitive tungstic acid precursor via the process developed.

Oxalic acid sensors based on sol–gel nanostructured TiO2 films

Titanium (IV) oxide semiconducting layers were prepared by means of the templated sol–gel method and deposited on conductive ITO substrates. The films were described by a series of techniques involving X-ray diffraction (XRD), Raman spectroscopy, X-ray reflectivity (XRR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultraviolet–visible spectroscopy (UV–Vis). The photo-excitation properties of the films were characterized by electrochemical tests and evaluated from the obtained polarization curves. The generated photocurrents were measured in the presence of the hole-scavengers—oxalic acid and formic acid in the electrolyte. It was shown that especially in the case of oxalic acid the developed system can be used as an efficient and simpler concentration sensor. The relationship between values of the generated photocurrent and the layers’ thicknesses was also investigated.

Preparation and magnetic properties of Fe2O3 microtubules prepared by sol-gel template method

Fe(OH)3 precursor sol was prepared by a sol-gel method. The precursor sol was dipped onto the absorbent cotton, and gel was formed on the absorbent cotton template after the volatilization of moisture. Fe2O3 microtubules were synthesized after the process of self-propagation or calcination. The phase, morphology, and particle diameter of the samples were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the magnetic properties of the samples were measured using a vibrating sample magnetometer (VSM). The external diameters of Fe2O3 microtubules ranged between 8 and 13 μm, and the wall thicknesses ranged between 0.5 and 2 μm. The type of the calcination method plays a significant role in developing the Fe2O3 phase and the variation in the magnetic properties in the sol-gel template complexing method. γ-Fe2O3 was synthesized by a self-propagation method. However, α-Fe2O3 was synthesized after calcination at 400°C for 2 h. The coercivity of the samples synthesized by calcination at 400°C for 2 h after self-propagation was found to increase significantly, thereby presenting hard magnetic properties.

Study of surfaces of TiO2-based nanostructured films obtained under action of various templates

Using the template sol-gel method and employing polyethyleneimine, polyethylene glycol monooleate, and octylamine as templates, we obtain hybrid materials based on titanium dioxide whose structure contains ordered mesophases of organic substrates. The materials are studied using the thermal, X-ray phase, and X-ray diffraction analyses, as well as small-angle X-ray scattering. Films on a glass surface are obtained from isopropanol solutions containing titanium isopropoxide and organic templates via immersion technique. The surface structure of the films formed before and after annealing was studied by scanning probe microscopy. It is shown that, by using various structure-forming agents, it is possible to control the structure of hybrid materials and films in meso- and macroregions and to obtain titanium dioxide with different composition crystalline modifications during their heat treatment.

Synthesis of Nanostructural Silica Using Quaternary Ammonium Salt of Lignin as Template

Cationic surfactant, quaternary ammonium salt of lignin, was synthesis from the lignin and trimethylamine though Mannich Reaction. Then quaternary ammonium salt of lignin was used as a novel template to prepare nanostructural silica from TEOS by sol-gel templating method. After removing the template at 580°C, nanostructural silica were obtained. The results of SEM and TEM show that there were two kinds of the silica after calcined. One is 3-dimetional macroporous silica, with the pore size of 100-200 nm. The other kind of silica is nanoparticle: the particle sizes range from 20 to 200nm and the specific surface area is 387.6 m2•g-1.

Synthesis and ferroelectric properties of Nd doped multiferroic BiFeO3 nanotubes

Nd doped multiferroic BiFeO3 (Bi0.94Nd0.06FeO3 (BNF)) nanotubes were successfully synthesized by a sol-gel template method. Electron microscopy investigations exhibited that these nanotubes had straight and smooth profile with diameters of about 200 nm and wall thickness of about 20 nm. A perovskite-type structure of BNF was confirmed in the nanotubes by high-resolution transmission electron microscopy and selected area electron diffraction analysis. These nanotubes had high resistivity. The dielectric constant and dielectric loss of the nanotubes were 126 and 0.040 at 1 MHz, respectively. The ferroelectric properties of these BNF nanotubes were demonstrated with a remnant polarization of 48 μC/cm2 and a coercive electric field of 163 kV/cm.

Hydrogen production by auto-thermal reforming of ethanol over nickel catalyst supported on metal oxide-stabilized zirconia

Metal oxide-stabilized mesoporous zirconia supports (M–ZrO 2) with different metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) were prepared by a templating sol–gel method. 20 wt% Ni catalysts supported on M–ZrO 2 (M = Zr, Y, La, Ca, and Mg) were then prepared by an incipient wetness impregnation method for use in hydrogen production by auto-thermal reforming of ethanol. The effect of metal oxide stabilizer (M = Zr, Y, La, Ca, and Mg) on the catalytic performance of supported nickel catalysts was investigated. Ni/M–ZrO 2 (M = Y, La, Ca, and Mg) catalysts exhibited a higher catalytic performance than Ni/Zr–ZrO 2, because surface oxygen vacancy of M–ZrO 2 (M = Y, La, Ca, and Mg) and reducibility of Ni/M–ZrO 2 (M = Y, La, Ca, and Mg) were enhanced by the addition of lower valent metal cation. Hydrogen yield over Ni/M–ZrO 2 (M = Zr, Y, La, Ca, and Mg) catalyst was monotonically increased with increasing both surface oxygen vacancy of M–ZrO 2 support and reducibility of Ni/M–ZrO 2 catalyst. Among the catalysts tested, Ni catalyst supported on yttria-stabilized mesoporous zirconia (Ni/Y–ZrO 2) showed the best catalytic performance.

Bioinspired Photonic Crystals: Diamond‐Structured Titania Photonic‐Bandgap Crystals from Biological Templates (Adv. Mater. 1/2010)

The striking coloration of the weevil Lamprocyphus augustus is the result of exoskeleton photonic structures with a diamond-based lattice. Michael Bartl and co-workers report on p. 107 on the development of a sol–gel templating method to convert these unique biopolymeric structures into high-dielectric replicas. Theoretical, structural, and optical studies reveal these bioderived photonic crystals possess a complete bandgap at visible frequencies – the basis for novel optical phenomena based on light localization.

Nitrogen-doped SiO2/TiO2 core/shell nanoparticles as highly efficient visible light photocatalyst

Abstract Nitrogen-doped SiO 2 /TiO 2 core/shell nanoparticles with uniform diameter were fabricated using SiO 2 template sol–gel method. Furthermore, the relationship between the temperate of calcination and photocatalytic efficiency was also investigated in the viewpoint of organic pollutant decomposition. The morphology and characteristics of nitrogen-doped SiO 2 /TiO 2 core/shell nanoparticles were studied by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), and specific surface area. The results demonstrated that nitrogen-doped TiO 2 layer was successfully coated onto the SiO 2 nanoparticles without aggregation. Nitrogen-doped SiO 2 /TiO 2 core/shell nanoparticles exhibited highly efficient photocatalytic activity under visible light irradiation due to high nitrogen doping level and surface area.

Synthesis and Multiferroic Properties of BiFeO3 Nanotubes

Highly ordered BiFeO3(BFO) nanotubes with about 200 nm in diameter and 60 μm in length are fabricated by a sol-gel AAO template method. A perovskite-type structure of BFO is confirmed in the nanotubes by transmission electron microscopy and selected area electron diffraction analysis. The coexistence of ferroelectric and ferromagnetic ordering of these BFO nanotubes at room temperature is demonstrated, giving a remnant polarization of 26μC/cm2, a low coercive electric field of 60 kV/cm, and a magnetization of 0.18 emu/g. In addition, it is found that the leakage behavior of these nanotubes is dominated by the ohmic contact mechanism.

A novel preparation of macroscopic beads of porous silica

We report a new method for preparing porous silica beads using a high internal phase emulsion (HIPE) sol–gel templating method. The method uses a silica sol based HIPE and does not rely on a polymeric support to produce the final structure. As a result beads may be formed readily in large numbers. The beads have an open porous structure commensurate with the formation of a HIPE precursor phase. We also describe how the rheology of the HIPE reflects the formation of an open porous structure and how the viscosity of the HIPE can affect the shape of the beads and how HIPE destabilization may be used to vary the pore size.

Ag nanoparticles deposited onto silica, titania, and zirconia mesoporous films synthesized by sol–gel template method

A variety of Ag nanoparticles/oxide mesoporous films with templated silica, titania, and zirconia was synthesized by sol–gel method at glass, aluminum, and silicon substrates using metal alkoxides (tetraethoxysilane, titanium tetraisopropoxide, and zirconium tetrapropoxide) and AgNO3 as precursors of oxide films and Ag nanoparticles, respectively, and Pluronic P123 as a template agent. Oxide films alone and Ag/oxide composites were characterized using hexane adsorption, X-ray diffraction (XRD), Raman and ultraviolet (UV)/vis spectroscopies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The distribution of Ag nanoparticles within the films, their sizes, intensity, and position of surface plasmon resonance (SPR) absorbance band at λ = 400 nm, as well as the textural and structural characteristics of whole films depend on treatment temperature, types of substrates and oxide matrices, oxide crystallization, and Ag content. Ag nanoparticles form preferably on the outer surface of the films under lower sintering temperatures if the amount of loaded silver is low. Oxide crystallization (e.g., TiO2) promotes silver embedding into the outer film layer. At higher silver content (≥10 at.%) and higher calcination temperature (873 K), silver nanoparticles could be entrapped more uniformly along the film profile because of more intensive evaporation of silver droplets from the outer surface of the films on heating.