Sol-gel Hydrothermal Method Research Articles

Synthesis of Keggin-type lacunary 11-tungstophosphates encapsulated into mesoporous silica pillared in clay interlayer galleries and their catalytic performance in oxidative desulfurization

Keggin-type lacunary polyoxotungstates [PW11O39(H2O)]7− (PW11) and metal-modified [PW11O39(H2O)M]5− (M=Ni2+ or Co2+) were incorporated into the mesoporous silica pillared clays (MSPC) by a hydrothermal sol–gel method. The resulting materials retain the layered structure of the clay precursor and possess a mesoporous structure. The catalytic performance of the materials was tested using oxidative desulfurization of dibenzothiophene-containing model oil as a probe reaction. The results indicated that PW11-MSPC possess an excellent catalytic performance.

Preparation of Nano-Copper Oxide and Removal of Hydrogen Sulfide under Room Temperature

In this paper, nanocopper oxide is prepared by complexing-precipitate, and the influence of different process parameters on the removal of H2S performance are studied, and make a comparison for two other methods. The results indicate that different complexing agent, the molar ratio of Cu2+/OH- and calcination temperature, etc., effect the desulfurization activity of nanocopper oxide. nanocopper prepared under optimum conditions (the complexing agent is ammonia, the molar ratio of Cu2+/OH- is 1:3.0, calcination temperature is 400 °C) exhibits best desulfurization activity with a H2S breakthrough time of 235 min, this is much longer than that prepared by hydrothermal method and sol-gel method with breakthrough time of H2S only 20 min and 50 min, respectively; XRD analysis shows that the big grain size of nanocopper oxide and low purity are not in favor of H2S adsorption at room temperature.

Design of H3PW12O40/TiO2 nano-photocatalyst for efficient photocatalysis under simulated sunlight irradiation

H3PW12O40/TiO2 (PW12/TiO2) nano-photocatalyst was successfully synthesized through a modified sol–gel-hydrothermal method. The X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra, UV–vis diffuse reflectance spectrum (UV–vis DRS), and N2 adsorption–desorption isotherms were characterized respectively to investigate the physical and chemical properties of prepared catalysts. Under simulated sunlight (320nm<λ<780nm) irradiation, the degradation of fuchsin acid, malachite green and p-nitrophenol (PNP) were carried out to evaluate the photocatalytic activity of PW12/TiO2. The results showed that the pollutants degradation followed first-order kinetics, and the kinetic constants of photocatalytic degradation of fuchsin acid, malachite green and PNP were 2.82, 4.66, and 3.48 times as great as that using pristine TiO2, respectively. The high pollutants degradation efficiency was ascribed to the synergistic effect between H3PW12O40 and TiO2, which resulted in enhanced quantum efficiency and high light harvesting efficiency. We believe this work could provide new insights into the fabrication of photocatalyst with high photocatalytic performance and facilitate their practical application in environmental issues.

ELECTROCHEMICAL PREPARATION OF NEW ORGANOSILICONE COMPOUNDS FOR FUNCTIONALIZING OF MESOPOROUS SILICA

Electrochemistry has been introduced as a powerful tool in order to prepare new organometallic reagents for functionalizing of mesoporous silica. Preparation of the reagents was based on electrochemical oxidation of dihydroxybenzene derivatives in the presence of 3-(trimethoxysilyl)-1-propanethiol as a nucleophile. The mechanisms of electrochemical reactions were studied by voltammetric studies. Mesoporous silica SBA-15 was also synthesized in this work through sol-gel hydrothermal method using Genapol PF-10 as structure directing compound. The prepared mesoporous silica was characterized by FT-IR analysis and Barrett–Joiner–Halenda (BJH) pore size and Brunauer–Emmett–Teller (BET) surface area measurement methods using N2adsorption–desorption isotherm. Finally, the organometallic reagent was covalently grafted on the surface of mesoporous silica. Functionalizing of this material with the new reagent was confirmed by Fourier transform infrared (FT-IR) spectroscopy. The functionalized mesoporous silica by new reagent can be utilized in biological applications.

Applications of highly ordered paddle wheel like structured ZnO nanorods in dye sensitized solar cells

Highly ordered paddle wheel like structured ZnO nanorods have been prepared by the simple sol–gel hydrothermal method. TiO2 nanoparticles are embedded on hydrothermally grown paddle wheel like structured ZnO nanorods. The TiO2 nanoparticle embedded nanorods were used as a photo-anode in dye sensitized solar cells and their photovoltaic performance was analyzed. The TiO2 nanoparticle embedded paddle wheel like structured ZnO nanorod electrodes enhance the adsorption of dye molecules, charge transport and power conversion efficiency. The crystallinity, presence of TiO2 nanoparticle on ZnO nanorods and morphology of the photo-anodes were characterized by X-ray diffraction and scanning electron microscopy studies. The dye molecules adsorbed by the photo-anode were observed by UV–vis absorption spectra. The efficiency of the TiO2 nanoparticle embedded paddle wheel like structured ZnO nanorod based dye sensitized solar cell is 3.25%.

Low-temperature synthesis of BaTiO 3 powders by the sol–gel-hydrothermal method

Abstract BaTiO 3 powders were successfully prepared by a novel sol–gel-hydrothermal method using tetrabutyl titanate and barium acetate as the main raw materials. The phase composition and microstructure of the powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results indicate that BaTiO 3 powders with well-developed crystallinity and good morphology could be synthesized at 120 °C (12 h) comparatively lower than the normal sol–gel route. The crystallinity and morphology were less affected by further increasing the reaction temperature and time. However, the KOH concentration had a great impact on the crystallinity and particles size of the powders that were all cubic phase with perovskite structure.

Efficient visible-light-driven photocatalytic H2 production over Cr/N-codoped SrTiO3

Visible-light-response Cr/N-codoped SrTiO3 was prepared by a sol–gel hydrothermal method. The comparison studies indicate that Cr-doped and Cr/N-codoped SrTiO3 can be synthesized by this means, but not the N-doped SrTiO3. The theoretical calculations exhibit the defect formation energy of the Cr/N codoping into SrTiO3 is much smaller than that of the N doping into SrTiO3, illuminating that the incorporation of Cr can promote the N doping into the O sites in the SrTiO3. Compared to the Cr-doped SrTiO3, the Cr/N-codoped SrTiO3 photocatalyst shows the high photocatalytic activities for hydrogen production with the quantum efficiency of 3.1% at 420 nm, due to the smaller band gap and much less vacancy defects.

Tunable morphology and optical absorption of bismuth ferrite synthesized by sol–gel–hydrothermal method

Bismuth ferrite BiFeO3 (BFO) powders with various morphologies were successfully prepared via a sol–gel–hydrothermal synthesis process. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Microspheres and microcubes were obtained as Bi–Fe–glycerol sol was used as precursor, and submicrometer-sized particles could be prepared by using Bi–Fe–glycerol gel. Possible formation mechanism of BFO microcrystals was proposed in this work. Moreover, the results of UV–vis diffuse reflectance spectroscopy reveal that BFO powders can be used as an effective photocatalyst under visible light in addition to its ferroelectric and magnetic applications.

Synthesize and Characterization of Ca2CuO3 Nanostructures via a Modified Sol–Gel Method Assisted by Hydrothermal Process

A sol–gel-hydrothermal method was used to prepare the highly homogeneous nanopowder of Ca2CuO3 ceramic with an average diameter of about 20–30 nm. In comparison with the conventional sol–gel process, this method caused the more purity product with smaller size of particle due to a high pressure and long reaction time. Photoluminescence measurement indicated that for Ca2CuO3 nanoparticles there are two emission peaks: one sharp band at about 400 nm and one broad visible emission band. The band gap energy of Ca2CuO3 nanoparticles has been estimated to be 3.09 eV that is far above the values reported earlier. The results showed that the morphology and particle size of the synthesized samples can be obviously affected by the reaction temperature and molar ratio (w) between citric acid and calcium nitrate. In this procedure, diethylene glycol monobutyl ether was used as both the solvent and the modest surfactant.

Sol–gel hydrothermal synthesis of strontium hexaferrite nanoparticles and the relation between their crystal structure and high coercivity properties

Hard magnetic strontium hexaferrite SrFe 12 O 19 nanoparticles were synthesized by the sol–gel hydrothermal method. The factors affecting the synthesized process, such as the mole proportion of the reactants, pH, temperature, the hydrothermal conditions and the calcination process, have been investigated. The crystal structures of these materials were refined by Rietveld method. The obtained materials have single crystal phase, equal nano-size, plate shape and high anisotropy. The high magnetic coercivity of 6.3 kOe with the magnetization at 11.1 kOe of 66 emu g −1 at room temperature was observed for the strontium hexaferrite nanoparticles. For other nanoparticles (SrLn x Fe 12-x O 19 and SrFe 12 O 19/CoFe 2 O 4) synthesized on the basis of SrFe 12 O 19 the complex completion of the crystal structure distortion and the interaction between magnetic phases were observed.

Photocatalytic degradation of an aqueous sulfamethoxazole over the metallic silver and Keggin unit codoped titania nanocomposites

A series of metallic silver and Keggin unit codoped titania nanocomposites (H3PW12O40/Ag–TiO2) were prepared through a single step sol–gel-hydrothermal method. The composites mainly exhibited an anatase phase, featuring micro–meso dual porosity with metallic Ag nanoparticles homogeneously dispersed on the surface of the H3PW12O40/Ag–TiO2; meanwhile, they showed photoresponses to both the UV- and visible-light regions. As the novel composite photocatalysts, the materials were used to degrade a light-insensitive target compound, sulfamethoxazole (SMZ), under Xe lamp irradiation (320nm<λ<680nm). The influences of the experimental parameters such as the initial acidity of the reaction system, the initial concentration of SMZ, and the amount of the catalyst on the photocatalytic activity of the H3PW12O40/Ag–TiO2 were studied; additionally, the photocatalytic degradation pathway of an aqueous SMZ over H3PW12O40/Ag–TiO2 was proposed by analyzing the reaction intermediates and final products identified during the photcatalytic process. Finally, the recyclability of the photocatalyst was evaluated.

Inlaid Nd-substituted bismuth titanate nanoplates for protein immobilization and Nd-controlled electrochemical properties

Neodymium (Nd) substituted bismuth titanate (Bi4−xNdxTi3O12, BNTO-x) nanoplates inlaid one another were prepared by sol–gel hydrothermal method, which was explored for protein immobilization and biosensor fabrication. Comparative experiments witnessed that Bi3+ ions in bismuth titanate (Bi4Ti3O12, BTO) were successfully substituted with Nd3+ ions, and the electrochemical properties of the Hb–Chi–BNTO biosensors closely depended on the Nd3+ ion content. With increasing the Nd3+ doping content, the electrochemical performance of the Hb–Chi–BNTO-x biosensors showed regularly variable. Moreover, compared with the Hb–Chi–BTO and other Hb–Chi–BNTO-x biosensors, the Hb–Chi–BNTO-0.85 biosensor had more excellent electrochemical and electrocatalytic properties such as stronger redox peak currents (approximately three-fold), smaller peak-to-peak separation (50mV), larger heterogeneous electron transfer rate (14.1±3.8s−1), higher surface concentration of electroactive redox protein (about 8.16×10−11mol/cm2), and better reproducibility and stability. The Nd-depended electrochemical properties of the Hb–Chi–BNTO biosensors may open up a new idea for designing third-generation electrochemical biosensors, and the BNTO-0.85-based biosensor is also expected to find potential applications in many areas such as biomedical, food, and environmental detection.

Raman Observation of Silicomolybdic Acid Formation Derived from H&lt;sub&gt;2&lt;/sub&gt;MoO&lt;sub&gt;4&lt;/sub&gt; and Excess Tetraethylorthosilicate Using Hydrothermal Sol-gel Method

In order to develop the preparation procedure for silicomolybdic acid (H4SiMo12O40, SMA) on silica catalysts, H2MoO4 and excess tetraethylorthosilicate (TEOS) are employed as starting reagents and three catalysts with different loadings are prepared by a hydrothermal sol-gel method. From Raman measurements in the course of the preparation steps, Raman spectra imply the formation of beta type silicomolybdic acid (β-SMA) reported by M. A. Bañares et al.; Raman spectroscopy suggests that the SMA species are formed in the precursor solution and is stable on 14.6 and 20 wt% MoO3/SiO2 even in the drying process (110 °C). When the loading is 7.9 wt%, Raman peaks of SMA disappear after the hydrothermal treatment at 100 °C. The structural distortion of the SMA due to hydrogen interaction between OH groups and Mo=O bonds is also observed. Raman measurement indicates the transformation to β- and α-MoO3 in 20 wt% MoO3/SiO2 after the calcination at 500 °C, but only surface molybdates are observed at the loadings of 7.9 and 14.6 wt%. The results indicate that H2MoO4 is also effective for the simple preparation of SMA. In addition, as no XRD patterns of all Mo species are observed, Raman spectroscopy is an effective method to structural analysis of Mo species, even in liquid and wet samples.

Preparation of TiO2-Nanorods Supported Pd Catalyst and Its Electrocatalytic Oxidation on Formic Acid

TiO 2 nanorods (TiO2-R) and irregular TiO2 (TiO2-I) with anatase phase structure are synthesized by hydrothermal synthesis and inorganic sol gel method, respectively. Using as-prepared TiO2 as support, Pd/TiO2 catalysts are prepared by using sodium ethylenediamine tetracetate (EDTA) as complexing agent and NaBH4 as reductant. The studies of transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that the average particle size of Pd/TiO2-R catalyst is very similar to that of Pd/TiO2-I catalyst. Cyclic voltammetry measurements show that the peak current of formic acid oxidation at Pd/TiO2-R catalyst increases by 70%. Chronoamperometric measurements indicate that the current density at the Pd/TiO2-R catalyst electrode at 3000 s is almost 16 times larger than that at the Pd/TiO2-I catalyst electrode. These electrochemical experiments show that the electrocatalytic activity and long-term operation stability of Pd/TiO2-R catalyst are much better than that of Pd/TiO2-I catalyst for formic acid oxidation in acidic media, indicating that TiO2 nanorods support material can effectively promote the electrocatalytic activity and sta- bility of Pd catalyst for formic acid electrooxidation. Likely, TiO2 nanorods possess good electronic conduc- tivity and abundant surface oxygen-containing groups, which improve the electrocatalytic activity and the anti-poisoned performance of Pd catalyst for the formic acid electrooxidation. Thus, TiO2 nanorods with

Hydrothermal Treatment and its Influence on the Structure of Phosphorous Doped Titania

P-doped titania was synthesized by a one step hydrothermal method and sol-gel method, which is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The samples prepared by hydrothermal method demonstrate higher photocatalytic activity toward the degradation of methylene blue under xenon lamp which has similar spectra to solar light, and also is much superior to that of the commercial P25. The as prepared P-doped titania shows a small particle size (the minimum reaches to 4.5 nm). In addition, the samples prepared by hydrothermal treatment could severely influence the crystal lattice structure. Morever, P-doped titania can further enhacnce the photocatalytic activity effectively, and hydrothermal treatment is a very suitable method for the synthesis of P-doped titania. This excellent performance could endow the as-prepared P-doped titania potential in purifying wastewater.

Synthesis, characterization and photocatalytic activity of Bi-doped TiO 2 photocatalysts under simulated solar irradiation

A series of Bi 3+-doped TiO 2 catalysts with a doping concentration up to 2 wt% were prepared by a sol–gel hydrothermal method. The prepared photocatalysts were characterized by different techniques to determine their structure, morphology and light absorption properties. The activities were evaluated in the photocatalytic oxidation of phenol in aqueous solution under UV–vis illumination. The experimental results indicate that the presence of Bi 3+ in TiO 2 catalysts enhances the photocatalytic reaction of phenol degradation, although the efficiency of the process markedly depends on the nominal content of the Bi 3+ and on the calcination temperature. It was found that the optimal dosage of 0.5 wt% Bi 3+ in TiO 2 and calcinations at 600 °C 4 h achieved the fastest reaction of phenol degradation under the experimental conditions. From the comparison of the initial rates of the photocatalytic degradation of phenol between home prepared undoped and Bi 3+-doped TiO 2 with commercial TiO 2 Degussa P25, it can be inferred that home prepared TiO 2 calcined at temperatures above 500 °C clearly exceed the photocatalytic performance of P25. When bismuth is incorporated, the reaction rate values are even higher, especially at 600 °C. Even when Bi 3+-doped TiO 2 (0.5 wt% Bi 3+) calcined at 600 °C has almost the same BET surface than P25, its activity is better. In particular, the reaction rate for the sample with a 0.5% mass content of Bi 3+ calcined at 600 °C not only present higher value with respect to the other series but also a degree of mineralization close to 100%.

Low-temperature preparation of lanthanum-doped BiFeO 3 crystallites by a sol–gel-hydrothermal method

Multiferroic Bi 1− x La x FeO 3 (BLFO, x = 0, 0.15, 0.3, 0.4) powders were for the first time synthesized by a novel sol–gel-hydrothermal route. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and fourier transform infrared (FT-IR) spectroscopy. The XRD results indicated that pure BLFO crystallites could be obtained for x ≤ 0.3, and the phase purity was sensitive to the concentration of mineralizer. SEM results revealed that the morphology and dimension of the BLFO microspheres and submicrotiles could be effectively controlled by varying KOH concentrations. The formation mechanism of the BLFO crystalline was also discussed.

Degradation of PCP-Na with La–B co-doped TiO 2 series synthesized by the sol–gel hydrothermal method under visible and solar light irradiation

A series of photocatalysts was synthesized by doping TiO 2 with La and B via the sol–gel hydrothermal route. The photocatalytic capability of the catalysts under visible and solar light was evaluated in terms of sodium pentachlorophenate (PCP-Na) decomposition and dechlorination. The structural and physicochemical properties of these nanocatalysts were characterized by XRD, DRS, ICP-OES, TEM, XPS, and N 2 adsorption–desorption techniques. B doping enlarged the anatase framework, and La doping hindered the crystallization and growth of the mesoporous structure in both singly La-doped and La–B co-doped catalysts. B implantation mainly resulted in visible-light response, whereas overload La 2O 3 coating worsened visible light absorption, as confirmed by DRS and XPS. XPS and ICP-OES analyses revealed that the B and La content increased approximately by 1.6 and 4.8 times from the interior to the surface of modified TiO 2, which dominantly existed in the form of La 2O 3 and interstitial B structure. The co-doped sample with 1% La and 5% B doping (LA10B50) exhibited maximum photocatalytic activity under visible and solar light compared with the mono-doped samples, which was attributed to synergetic effects, namely, efficient separation of photo-generated carriers by La and response to the extended visible region due to B. An increase in hydroxyl groups and the photosensitivity of carbon on the surface also contributed to the improvement of photoactivity.

Low‐temperature preparation of bismuth ferrite microcrystals by a sol‐gel‐hydrothermal method

AbstractWell‐crystallized pure perovskite bismuth ferrite (BiFeO3) powders with various morphologies have been synthesized by a novel sol‐gel‐hydrothermal route for the first time, which combined the conventional sol‐gel process and the hydrothermal method. The as‐prepared samples were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and ferroelectric test system. The results revealed that the compositions, morphological and dimensional changes in bismuth ferrite samples synthesized by sol–gel–hydrothermal method strongly depend on the concentrations of mineralizer. Ferroelectric hysteresis loops are displayed in the BiFeO3 samples. The bismuth ferrites were hydrothermally synthesized at as low a temperature as 180 °C, which is comparatively lower than that synthesized by the normal sol–gel route. The formation mechanism of the bismuth ferrite crystalline was also discussed. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Sol–gel hydrothermal synthesis and enhanced biosensing properties of nanoplated lanthanum-substituted bismuth titanate microspheres

Nanoplated lanthanum-substituted bismuth titanate (Bi3.25La0.75Ti3O12, BLTO) microspheres constructed with tens of BLTO nanoplates were synthesized by a sol–gel hydrothermal method. Using nanoplated BLTO microspheres, a novel third-generation H2O2 biosensor was fabricated with loading of myoglobin (Mb) and chitosan (Chi). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) measurements reveal that partial Bi ions of bismuth titanate (BTO, Bi4Ti3O12) are successfully substituted with La ions by the sol–gel hydrothermal method. UV-visible (UV-vis) and Fourier-transform infrared (FTIR) spectra show that Mb encapsulated in the Mb–Chi–BLTO film can retain its bioactivity well. Comparative experiments witness that the Mb–Chi–BLTO biosensor, compared with the Mb–Chi–BTO biosensor, not only has enhanced direct electron-transfer capacity (e.g., stronger redox peak currents (approximately 3-fold) and a larger heterogeneous electron-transfer rate constant of 12.8 ± 3.3 s−1), but also exhibits a wider linear response to H2O2 in the concentration range of 2–490 μM, higher sensitivity (88 mA cm−2 M−1), a lower Michaelis–Menten constant (0.55 mM) and detection limit (0.14 μM), a shorter response time (2.8 s), and better reproducibility and stability. These results imply that La doping greatly improves electrochemical and electrocatalytic properties of the Mb–Chi–BLTO biosensor, which will open up a new idea for the design of third-generation electrochemical biosensors, and the BLTO-based biosensors are also expected to find potential applications in many areas such as clinical diagnosis and food and environmental detection.