Sol Gel Template Method Research Articles

One-Dimensional Nanostructured TiO2for Photocatalytic Degradation of Organic Pollutants in Wastewater

The present paper reviews the progress in the synthesis of one-dimensional (1D) TiO2nanostructures and their environmental applications in the removal of organic pollutants. According to the shape, 1D TiO2nanostructures can be divided into nanorods, nanotubes, nanowires/nanofibers, and nanobelts. Each of them can be synthesized via different technologies, such as sol-gel template method, chemical vapor deposition, and hydrothermal method. These methods are discussed in this paper, and the recent development of the synthesis technologies is also presented. Furthermore, the organic pollutants, degradation using the synthesized 1D TiO2nanostructures is studied as an important application of photocatalytic oxidation (PCO). The 1D nanostructured TiO2exhibited excellent photocatalytic activity in a PCO process, and the mechanism of photocatalytic degradation of organic pollutants is also discussed. Moreover, the modification of 1D TiO2nanostructures using metal ions, metal oxide, or inorganic element can further enhance the photocatalytic activity of the photocatalyst. This phenomenon can be explained by the suppression of e−-h+pairs recombination rate, increased specific surface area, and reduction of band gap. In addition, 1D nanostructured TiO2can be further constructed as a film or membrane, which may extend its practical applications.

The Photocatalytic Reduction of Hexavalent Chromium by Controllable Mesoporous Anatase TiO2Nanoparticles

Titania (TiO2) nanoparticles with periodical mesopore size (up to 150 Å) have successfully been synthesized by sol-gel template method, using titanium(IV) tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different quantities of activated carbon (0%, 5%, and 10% by weight) were used as templates to control the porosity and particle size of titania nanoparticles. The templates were completely removed during the calcination in air at 500°C for 3 hr. The results showed that the specific surface area of titania is increased with increasing activated carbon content. The optical bandgap of synthesized titania exhibits a blue shift by 0.3–0.6 eV when compared to the reported value for the bulk anatase and rutile phases. The photocatalytic activity of porous titania is determined with its reduction efficiency of hexavalent chromium (Cr6+). The reduction efficiency is optimized under ultraviolet illumination.

Influence of sulfuretted temperature on the luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays by EDTA complexing sol–gel template method

Y2O3:Eu3+, Mg2+, Ti4+ nanotube arrays were prepared by sol–gel template method using EDTA (Ethylene Diamine Tetraacetic Acid) as complexing agent to serve as precursor. Long-lasting phosphors Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays were obtained by calcinating the precursor in the CS2 atmosphere. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and photoluminescence spectroscopy were used to investigate the effects of sulfuretted temperature on the crystal characteristics, morphology and luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays. The results of XRD and EDS reveal that the main phase of sample is Y2O2S when the sulfuretted temperature is 700–850 °C, and the ratio of element Y and S of the sample is very close to 2:1. The SEM observations show that the obtained Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays are of uniform size. From the spectrum, the main emission peak lies at 626nm under the 320nm excitation, which is ascribed to the transition of Eu3+ ion from 5D0 to 7F2. After irradiation with 365nm UV (Ultraviolet) radiation for 10min, the phosphor emitted red long-lasting phosphorescence which could last for about 17min (⩾1 mcd/m2).

Influence of Eu3+ doping concentration on the luminescence properties of Y2O2S: Eu3+, Mg2+, Ti4+ nanoarrays via sol–gel template method

Firstly, Y(2−x−0.04)O3: xEu3+, Mg2+0.02, Ti4+0.02 (x=5.0mol%, 5.5mol%, 6.0mol%, 6.5mol% and 7.0mol%) nanotube arrays were synthesized by sol–gel template method to serve as the precursors. Then the precursors were calcined in CS2 condition at 850°C for 2h to obtain the red long afterglow phosphor Y2O2S: Eu3+, Mg2+, Ti4+ nanotube arrays with different Eu3+ doping concentration. The samples of theY2O2S: Eu3+, Mg2+, Ti4+ nanotube arrays were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence spectroscopy and long-lasting phosphorescence. SEM proves that the Y2O2S: Eu3+, Mg2+, Ti4+ nanotube arrays are highly ordered and have uniform size. XRD testified that the main phase constitution of the phosphor is Y2O2S. From the spectrum, the main emission peaks at 616nm and 626nm are excited by the 339nm UV excitation, which are ascribed to the Eu3+ ions transition from 5D0 to 7F2. After irradiation by 365nm UV radiation for 10min, the decay time of the Y2O2S: Eu3+, Mg2+, Ti4+ nanotube arrays with 6.5mol% Eu3+ doping concentration could last for over 280s (⩾1mcd/m2).

Synthesis of Anatase TiO<SUB>2</SUB> Nanoparticles by Template Sol–Gel Method and Its Application in Photocatalytic Degradation of Organic Pollutants

Synthesis of Anatase TiO<SUB>2</SUB> Nanoparticles by Template Sol–Gel Method and Its Application in Photocatalytic Degradation of Organic Pollutants

The Performance of Au Nanoparticle Supported on Mesoporous TiO<sub>2</sub> for Low-Temperature CO Oxidation

A series of mesoporous TiO2 supports were synthesized by the sol-gel template method by using different surfactant and Au/TiO2 catalysts were prepared by the solution reduction method. The catalytic oxidation of CO was taken as the probe reaction for comparing the catalyst activity. Wide-angle XRD patterns and N2 adsorption–desorption isotherms revealed that the TiO2 with crystallized anatase and mesoporous structure can be synthesized after an optimized sol-gel template method. The results indicated that the pore size of TiO2 plays a key role in the catalyst activity. Among them the activity of Au/TiO2-F1 catalyst synthesized by using the F127 surfactant demonstrated superior activity to other catalysts. CO could be converted at 70 °C.

Oxygen vacancy dominant strong visible photoluminescence from BiFeO3 nanotubes

AbstractIn this Letter, we report oxygen vacancy dominant strong visible photoluminescence (PL) from multiferroic BiFeO3(BFO) nanotubes (NTs) prepared by sol–gel template method. Abundant oxygen vacancies present in BFO NTs provide alternate paths for the photo‐induced carrier generation and recombination thus affecting the PL and photoabsorption characteristics. This study not only assists in understanding the optoelectronic characteristics of BFO NTs at nanoscale but also suggests BFO nanostructures as potential candidates for future photonic and sensing applications. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation of biomorphic porous calcium titanate and its application for preconcentration of nickel in water and food samples

Biomorphic porous nanocrystalline-calcium titanate (SPCTO) was successfully prepared using the sol–gel method and with sorghum straw as the template. Characterization was conducted through XRD, SEM and FTIR. The ability of SPCTO to adsorb nickel ion in water was assessed. Elution and regeneration conditions, as well as the thermodynamics and kinetics of nickel adsorption, were also investigated. The result showed that the sorbent by the sol–gel template method was porous and has a perovskite structure with an average particle diameter of 26nm. The nickel ion could be quantitatively retained at a pH value range of 4–8, but the adsorbed nickel ion could be completely eluted using 2molL−1 HNO3. The adsorption capacity of SPCTO for nickel was found to be 51.814mgg−1 and the adsorption behavior followed a Langmuir adsorption isotherm and a pseudo-second-order kinetic model. The enthalpy change (ΔH) of the adsorption process was 33.520kJmol−1. At various temperatures, Gibbs free energy changes (ΔG) were negative, and entropy changes (ΔS) were positive. The activation energy (Ea) was 25.291kJmol−1 for the adsorption. These results demonstrate that the adsorption was an endothermic and spontaneous physical process. This same method has been successfully applied in the preconcentration and determination of nickel in water and food samples with good results.

Hydrogen evolution by templated cadmium indate nanoparticles under natural sunlight illumination

Carbon-doped cadmium indate (CdIn2O4) nanoparticles were synthesized by a sol–gel templating method using the block co-polymer surfactant Pluronic F127 and evaluated for hydrogen generation activity under artificial and natural solar illumination. Each catalyst powder was loaded with platinum as a cocatalyst in order to promote charge carrier separation. BET surface area measurements indicated an increase in surface area with F127 introduction of up to 5 times the area of the non-templated sample. Natural sunlight illumination experiments showed the hydrogen evolution rate of CdIn2O4 was 17 μmol h−1 as compared to 2.1 μmol h−1 for the Pt:TiO2 reference material. The H2 rate was determined to be similar under both stirring and non-stirring conditions for the CdIn2O4 catalyst, which resulted from 10 min irradiation exposure times. Laboratory experiments confirmed this effect and showed that at longer, out to 60 min, irradiation times the evolution rate was 3 times greater for stirred over non-stirred samples. The templated nanoparticle CdIn2O4 catalysts are promising for solar hydrogen conversion.

Luminescent Eosin Y–SiO2 hybrid nano and microrods prepared by sol–gel template method

Sol–gel chemistry within the pores of a polycarbonate template membrane was used for the preparation of Eosin Y–SiO2 hybrid nano- and microrods, using tetraethylorthosilicate [TEOS, Si(OC2H5)4] as the precursor in the presence of trifluoroacetic acid (TFA) catalyst. The ethanolic solution of Eosin-Y was added to the silica sol to trap dye molecules inside the SiO2 gel network during the gelation. Structural and morphological characterization using scanning electron microscopy (SEM) and luminescence microscopy have shown the formation of rods with 200nm and 1.2μm diameter and about 30μm length, exhibiting luminescence properties. Spectroscopic characterization has shown that the luminescence is due to Eosin-Y molecule in the xerogel porous network, surrounded by a solvation shell given mainly by the water.

Functional and Disordered Meso-Macroporous <I>γ</I>-Al<SUB>2−<I>x</I></SUB>M<SUB><I>x</I></SUB>O<SUB>3±<I>y</I></SUB> (M = Cu and/or Ce)

Disordered meso-macro porous Cu-Ce-Al2O3 nanocomposite (gamma-Al(2-x)M(x)O3 +/- y, M = Cu and or Ce) with different compositions has been synthesized. In situ templated sol-gel method has been adopted with simple EDTA ethylenediamine tetra aceticacid and ethylenediamine molecules to prepare gamma-Al(2-x)M(x)O3 +/- y, (M = Cu and or Ce). Above meso-macro porous materials were characterized by structural, spectroscopy, microscopy and textural techniques. Detailed characterization indicates that Cu2+ ions are introduced into the ceria and alumina lattice positions. Nano composite nature of the gamma-Al(2-x)M(x)O3 +/- y has been confirmed by detailed microscopy investigations. Catalytic activity of the above nanocomposite materials have been screened for environmentally important CO oxidation reaction. 30% Ce-60% Al and 10% Cu containing material shows the best activity among other meso-macroporous material with (50%) 100% CO oxidation at (107 degrees C) 145 degrees C.

Influence of sulfuretted temperature on the luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays

Y2O3:Eu3+, Mg2+, Ti4+ nanotube arrays were firstly prepared via sol–gel template method to serve as precursor. Long-lasting phosphors Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays were obtained by calcinating the precursor in the CS2 atmosphere. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and photoluminescence spectroscopy were used to investigate the effects of sulfuretted temperature on the crystal characteristics, morphology and luminescent properties of Y2O2S:Eu3+, Mg2+, Ti4+ nanoarrays. The results of XRD and EDS reveal that the main phase of sample is Y2O2S when the sulfuretted temperature rises to 850°C, and the ratio of element Y and S of the sample is very close to 2:1. The SEM observations show that the obtained Y2O2S:Eu3+, Mg2+, Ti4+ nanotube arrays are of uniform size. From the spectrum, the main emission peak lies at 626nm under the 320nm excitation, which is ascribed to the transition of Eu3+ ion from 5D0 to 7F2. After irradiation with 365nm UV (Ultraviolet) radiation for 10min, the phosphor emitted red long-lasting phosphorescence which could last for about 3min (≥1mcd/m2).

The synthesis of microporous and mesoporous titania with high specific surface area using sol–gel method and activated carbon templates

In this study, porous titania nanoparticles were synthesized by sol–gel template method, using titanium (IV) tetraisopropoxide as a starting precursor and isopropanol as a solvent. Different commercial activated carbons were used as templates at 10wt% in titania sol. The templates were completely removed during the calcination in air at 500°C for 3h, forming porous titania. Nanocrystalline anatase titania with specific surface area as high as 700m2/g was successfully obtained in this study. This specific surface area is one of the highest values reported in the literature under similar sol–gel conditions.

Preparation of Nano-ZnFe<sub>2</sub>O<sub>4</sub> Doped TiO<sub>2</sub> Photocatalytic Films on Porous Hayddites

Applied nano-ZnFe2O4/TiO2 photocatlytic films are prepared by template sol-gel method on porous haydites. The effects of ZnFe2O4-doping on TiO2 crystallization, sintering temperature, light absorption and photocatalysis are mainly studied, simultaneously, effect of template, amphiphilic block copolymer P(styrene-b-acrylic acid) (PS-b-PAA) on the phtocatalytic activity of ZnFe2O4/TiO2 films are also studied. The results show that right amount of ZnFe2O4-doping reduces TiO2 sintering temperature and particle size, and increases TiO2 absorbency in ultraviolet region, and a right amount of template (PS-b-PAA) forms orient arranged ZnFe2O4/TiO2 films with the high photocatalytic activity and decomposes fully methyl orange in water after light irradiating 2h.

Preparation and characterization of multiferroic CoFe2O4/Bi0.97Ce0.03FeO3 coaxial nanotubes

Multiferroic CoFe2O4 (CFO)/Bi0.97Ce0.03FeO3 (BCFO) coaxial nanotubes were prepared by a sol-gel template method. Transmission electron microscopy revealed that the coaxial nanotubes featured with inner CFO and outer BCFO nanotubes. Selected area electron diffraction confirmed the coexistence of spinel CFO and perovskite BCFO phases in the coaxial nanotubes. Vibrating sample magnetometer measurements showed that the saturated magnetization of the coaxial nanotubes was 3.3 emu/g, smaller than that of CFO nanotubes. The P–E hysteresis loop of the coaxial nanotubes was of poor shape due to possible high conductivity in the inner CFO nanotubes. Dielectric measurements exhibited that the dielectric constant of the coaxial nanotubes decreased while the dielectric loss increased due probably to the small dielectric constant and high conductivity in the inner CFO nanotube. Ferroelectric and magnetic properties were simultaneously demonstrated in the CFO/BCFO coaxial nanotubes.

Preparation and properties of the CoFe2O4/Bi3.15Nd0.85Ti3O12 multiferroic composite coaxial nanotubes

The CoFe2O4 (CFO)/Bi3.15Nd0.85Ti3O12 (BNT) multiferroic composite coaxial nanotubes were prepared by a sol–gel template method. The morphologies of the coaxial nanotubes were characterized and the selected area electron diffraction patterns confirmed the coexistence of spinel CFO and perovskite BNT phase. The vibrating sample magnetometer measurements showed that the saturation magnetization and coercive field of the coaxial nanotubes were 1emu/g and 0.7kOe, respectively, which was contributed totally from the inner CFO nanotubes. The CFO/BNT coaxial nanotubes showed typical ferroelectric hysteresis loop, while the increased leakage current density is likely due to the high conductivity in the inner CFO nanotubes. Our study demonstrated that the CFO/BNT coaxial nanotubes were of both ferroelectric and magnetic features in nanoscale.

Sol–gel template synthesis and characterization of VO2 nanotube arrays

In this paper, we report on the obtention of highly ordered VO2 nanotube arrays synthesized by the simple sol–gel template method. Techniques of transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy were used to characterize the morphology and structure of the as-synthesized nanotube arrays. It is found that the size of the as-obtained nanotubes has the dimension of 180–220 nm in outer diameter, 110–140 nm in inner diameter and up to 10 μm in length. The results show that as-synthesized sample is assigned to VO2 (B) phase in expected V/O ratio with V existing in the +4 oxidation state.

Synthesis and characterization of mesoporous titania microspheres and their applications

Mesoporous titanium dioxide microspheres were synthesized by the sol–gel templating method, using calcium alginate as a sacrificial template, and subjecting to different temperatures, under various atmospheres. The gradual changes in composition, crystallinity, phase and surface morphology, due to variation in calcination atmosphere and temperature, were monitored by TGA, XRD, SEM and EDX techniques. The effect of polymeric content on the surface area and the pore size of the titania beads was evaluated by BET analysis. The results show that N2 atmosphere and high temperature influence the phase content and morphology of the microsphere significantly. Anatase to rutile phase transformation and formation of calcium titanate take place under nitrogen atmosphere at lower temperature, as compared to that under air atmosphere. To examine the applications of these synthesized microspheres, photo-catalytic activity and sorption efficiency of the microspheres were evaluated, by carrying out photo-degradation of methylene blue (MB) dye, and removal of arsenic ions from ammoniacal solution. The microspheres showed good photo catalytic activity towards MB dye. Tracer experiments with 76As showed ∼98% sorption of arsenic ions from aqueous solution onto the titania microspheres.

Fabrication of PZT nano dot array and their ferroelectric properties

This paper demonstrates a promising and low-cost method for fabricating PZT nano-dot array by using sol–gel template method combined with laser interference lithography. ZrO2 template with the pitch of 1 μm is firstly fabricated by sol–gel method and laser interference with a 325 nm He-Cd laser. Afterwards, PZT nano dot array with diameter of 500 nm and thickness of 20 nm is prepared on the ZrO2 template. Atomic force microscope results show that the PZT nano dot array is uniform and highly ordered. Ferroelectric properties of PZT nano dot array are in situ measured through online-operation of TF analyzer and AFM. A ferroelectric hysteresis loop is obtained for the PZT nano dot.

A Novel Fabrication Method of Magnetic Co/Ni0.4Zn0.6Fe204 Coaxial Nanocables

A highly ordered Co/Ni0.4Zn0.6Fe2O4 coaxial nanocable array has been synthesized based on porous anodized aluminum oxide template via a new approach, which combines an improved sol-gel template method and alternating current electrochemical deposition. Scanning electron microscopy and transmission electron microscopy images show the nanocables are uniform with outer diameter of about 50 nm and inner diameter of about 17 nm. X-ray diffraction patterns and energy dispersive spectrometer confirm that Co nanowires are successfully deposited into the pores of the Ni0.4Zn0.6Fe2O4 nanotubes. Normalized magnetic hysteresis loops demonstrate the coercive force and the squareness with the applied field parallel to the axis of the nanocables increase dramatically compared with that of the nanotubes.