Single Step Sol Gel Research Articles

Synthesis and characterization of superhydrophobic–superoleophilic surface

The binary superhydrophobic–superhydrophilic surface has been successfully achieved by a combination of nanoscale texture roughness on micro-textured cotton thread network by layer-by-layer deposition method through the single-step sol–gel route. Furthermore, microstructures with improved wettability were produced, in which silica nanotextures were grown without modifying the chemical method to form superoleophilic and superhydrophobic networks. A superoleophilic surface (oil contact angle 0°) and a superhydrophobic coated cotton fabric with surface free energy of γ total = 13. 23 ± 0.37 mJ m−2 (water contact angle of 167 ± 1° and a small sliding angle of 4 ± 1°) were successfully obtained. The results were exemplified here by the creation of immiscible oils separation membranes, and the innumerable applications of this technology also include self-cleaning fabrics, antistaining fabrics, water purification, and antiwetting fabrics for military applications.

One step synthesis and characterization of copper doped sulfated titania and its enhanced photocatalytic activity in visible light by degradation of methyl orange

This paper reports on the synthesis of copper doped sulfated titania nano-crystalline powders with varying (2.0%–10.0%, by mass) by single step sol gel method. The synthesized photo catalyst has been characterized by employing various techniques like X-ray Diffraction (XRD), Ultraviolet–Visible Diffuse Reflection Spectroscopy (UV–Vis DRS), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometry (EDS), Fourier Transform Infrared Spectroscopic Studies (FT-IR), and Transmission Electron Microscopy (TEM). From the XRD and TEM results, all the samples were reported in anatase phase with reduction in particle size in the range of 7 to 12nm. SEM indicated the change in morphology of the particles. The presence of copper in titania lattice was evidenced by XPS. From UV–Vis DRS and FT-IR studies indicated that prominent absorption shift is observed towards visible region (red shift), the entry of Cu2+ into TiO2 lattice as a substitutional dopant and SO42− ions were covalently bonded with Ti4+ on the surface of the copper doped titania respectively.The photocatalytic activity studies were investigated by considering methyl orange (MO) as dye pollutant in the presence of the visible light. The effect of various parameters like effect of dosage of the catalyst, dopant concentration, pH of the solution, and concentration of the dye was studied in detail.

Dynamic capture of low-concentration CO2 on amine hybrid silsesquioxane aerogel

Amine hybrid silsesquioxane aerogel (AHSA) was synthesized through a single-step sol–gel process followed by supercritical drying. CO2 adsorption performances of highly porous AHSA in 1% CO2 were investigated. 50°C is preferred to perform the CO2 capture of AHSA to achieve a CO2 adsorption capacity of 3.04mmol/g (dry) or 3.84mmol/g (humid) under given conditions. A rise in adsorption gas flow rate from 300 to 700ml/min results in the decrease of CO2 adsorption capacity from 3.04 to 2.42mmol/g. The CO2 adsorption rate is mainly affected by the gas flow rate, while the effect of temperature can be ignored. Different with the adsorption performance, the CO2 desorption kinetics of AHSA is mainly affected by the temperature, the effect of gas flow rate is indifferent. Water favors the CO2 capture capability of AHSA, however, it is bad for the CO2 adsorption and desorption kinetics. The CO2 adsorption capacities of AHSA in 1% CO2 are much higher than those of other amine based porous adsorbents obtained with a 1% or even higher CO2 gas mixture. Also, AHSA has very short adsorption half time (22–55s) and low desorption temperature of 80°C, much lower than those of other amine-based adsorbents. The resulting adsorbent is dynamic and possesses excellent regenerability for low-concentration CO2 capture.

MoO3 modified CeO2/TiO2 catalyst prepared by a single step sol–gel method for selective catalytic reduction of NO with NH3

A MoO3 modified CeO2/TiO2 catalyst was prepared by a single step sol–gel method for selective catalytic reduction of NO with NH3. The experimental results indicates that MoO3 modified CeO2/TiO2 catalyst exhibited higher SCR activity and resistance to 10% H2O and 1000ppm SO2. From the characterization results, it can be concluded that good physical properties, highly dispersed active species of Ce and Mo, more appearance of Ce3+ and chemisorbed oxygen, strong interaction among ceria, molybdenum and titania, and high oxygen storage capacity might contribute to the excellent deNOx performance of CeO2–MoO3/TiO2 catalyst prepared by a single step sol–gel method.

Synthesis of PbS–Al2O3 nanocomposites by sol–gel process and studies on their optical properties

PbS–Al2O3 nanocomposites were prepared by a single step sol–gel method starting from lead acetate, thiourea and aluminium isopropoxide. The crystallinity, shape of crystallites and optical properties of the nanocomposites were examined by various analytical techniques. X-ray diffraction indicates that the PbS–Al2O3 nanocomposites consist of small PbS crystallites (18.2–40.5nm). Transmission electron microscopy images show cube-like and flake-like morphology for pure PbS and Al2O3, respectively and TEM images of the nanocomposites indicate uniform distribution of PbS nanoparticles on the Al2O3 matrix. Diffuse reflectance spectral (DRS) studies on the nanocomposites indicate near infrared (NIR) absorption and the nanocomposites exhibit blue shift of the band gap of PbS compared to pure PbS nanoparticles. Photoluminescence studies show characteristic peak due to excitonic emission of PbS nanoparticles in the nanocomposites.

Activity and characterization of a Ce–W–Ti oxide catalyst prepared by a single step sol–gel method for selective catalytic reduction of NO with NH3

A Ce–W–Ti mixed oxide catalyst prepared by a single step sol–gel method exhibited excellent SCR activity and high resistance to H2O and SO2. The excellent catalytic performance might be attributed to the improved dispersion of Ce species on TiO2, the increase in the amount of Ce3+ and chemisorbed oxygen and the strong interaction among ceria, tungsten and titania owing to the addition of WO3.

Synthesis of silica–titania composite aerogel beads for the removal of Rhodamine B in water

Silica–titania (SiO2–TiO2) aerogel beads are synthesized by a single-step sol–gel reaction, followed by supercritical drying. They show the good capability of removing RhB from water even after several successive adsorption–photodegradation cycles.

Synthesis of mesoporous Ag/ZnO nanocrystals with enhanced photocatalytic activity

Mesoporous Ag/ZnO nanocrystals have been successfully synthesized at different Ag contents (0–10wt%) through a single-step sol–gel method in presence of triblock copolymer as a structure directing agent. The as-prepared hybrid materials were calcined at 450°C in air for 4h, subsequently, Ag nanoparticles have been photo-reduced from AgNO3 onto mesopores ZnO nanocyrstals. The XRD and Raman analysis revealed that well crystalline ZnO hexagonal wurtzite phase and face-centered cubic metallic Ag nanoparticles were formed. TEM images of mesoporous ZnO nanocrystals showed that synthesized materials composed of discrete ZnO nanoparticles agglomerated with worm-like mesoporous structure. The lattice fringes exhibit the typical distances, i.e., Ag(111) and ZnO(100) and the average Ag and ZnO nanoparticle diameters are ∼5 and 10nm, respectively. The photocatalytic performance of different prepared photocatalysts was evaluated by degradation of methylene blue (MB) under visible light irradiation. The results indicate that the photocatalytic efficiencies of mesoporous ZnO photocatalysts were remarkably enhanced by adding 1% Ag nanoparticles which completely degrade the target MB dye within 150min. The photodegradation rate was found to increase linearly with increasing the Ag contents from 0 to 1% and it is faster 2.2 times than undoped ZnO. From economic point of view, 1% Ag/ZnO photocatalyst contains optimum Ag content as there is no significant increase in the photocalatytic performance at higher Ag content.

Design of cyanate ester/azomethine/ZrO2 nanocomposites high‐k dielectric materials by single step sol–gel approach

ABSTRACTIn this article we designed a cyanate ester based novel hybrid nanocomposites by sol–gel approach with different weight percentages of Zirconium dioxide (ZrO2). The synthesized monomer and polymer nanocomposites were characterized by Fourier‐transform infrared, 1H, and 13C nuclear magnetic resonance (NMR) spectra. Optical and thermal properties reveals the excellent optical transparency and good thermal stability of hybrid nanocomposites. Scanning electron microscope and high resolution transmission electron microscope analysis confirm the homogeneous dispersion of ZrO2 in the nanocomposites. Interestingly 7% ZrO2 nanocomposite exhibit highest k value of 9.21 which may be due to the well dispersion of ZrO2 and their strong interfacial polarization in the organic–inorganic hybrid nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41097.

Effect of silica sources on nanostructures of resorcinol–formaldehyde/silica and carbon/silicon carbide composite aerogels

The subject of this paper is the investigation of the effect of silica sources on microstructure of resorcinol–formaldehyde/silica composite (RF/SiO2) and carbon/silicon carbide composite (C/SiC) aerogels. Hybrid silica sources (HSS) were composed of 3-(aminopropyl)triethoxysilane (APTES) and tetraethoxysilane (TEOS) with different molar ratio. RF/SiO2 aerogel was obtained by a single-step sol–gel process followed by supercritical fluid drying (SCFD). C/SiC aerogel was formed from RF/SiO2 aerogel after carbothermal reduction. Scanning electron microscopy (SEM) and N2 adsorption/desorption were used to investigate the evolution of morphology and pore structures of aerogels. X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated that the as-prepared C/SiC aerogel was composed of carbon nanoparticle and α-SiC nanocrystal. The microstructure was hugely affected by the component of HSS. When the molar fraction of APTES in HSS was 60%, RF/SiO2 and C/SiC aerogels possessed the highest surface area and pore volume and the lowest thermal conductivity.

Single-Step Synthesis of Silver-Doped Titanium Dioxide: Influence of Silver on Structural, Textural, and Photocatalytic Properties

The silver-doped titanium dioxide (Ag–TiO2) photocatalysts with varied silver content ranging from 0.75 at % to 3.5 at % were synthesized by a single-step sol–gel method. The role of silver content on the properties of photocatalyst has been studied. The doping of 0.75 at % silver in TiO2 produced thermally stable TiO2 anatase phase with smallest particle size, uniform particles size and morphology, high surface area and low-energy excitation characteristics. The Ag–TiO2 sample with 0.75 at % silver possesses predominantly finely dispersed silver species (Ag2O and AgO) on the surface. The proportion of surface agglomerated silver metal (Ag0) increases as the silver content in the Ag–TiO2 sample increases. The silver oxide species were observed to be responsible for better physicochemical and catalytic properties. The TiO2 with 0.75 at % silver was found to be an efficient photocatalyst showing enhanced photocatalytic activity for aqueous medium photocatalytic degradation of phthalic acid in the presence of UV radiation and air.

Pendant chains containing thiopropanamide groups inside talc-like phyllosilicate galleries as thermodynamically favorable agents for cation removal

A lamellar inorganic–organic talc-like magnesium phyllosilicate has been synthesized through a single step sol–gel route under mild conditions, using a newly synthesized [3-(3-trimethoxysilylpropyl)thiopropanamide] silylating agent, obtained from acrylamine and 3-mercaptopropyltrimethoxysilane. Elemental analysis data based on the sulfur atom showed an incorporation of 3.66 mmol g−1 of the thiopropanamide group inside the galleries of the hybrid. Infrared spectroscopy and nuclear magnetic resonance (NMR) in the solid state for the 13C nucleus confirmed the thiopropanamide moiety covalently bonded inside the lamellar structural galleries. Solid state 29Si NMR showed the presence of Tn silicon species in the backbone in agreement to the hydrolysis and condensation reactions during the sol–gel process. X-ray diffractions gave a basal distance of 1.854 nm, near twice that of the natural talc and the 060 reflection confirmed a structure similar to natural talc. The basic centers on pendant chain coordinate divalent nickel, cadmium and lead cations from aqueous solution at the solid/liquid interface. Based on the Langmuir model, the maximum sorption capacity of the hybrid for these cations was 0.70, 1.10 and 2.71 mmol g−1, respectively. The thermodynamic data for cation/basic center interactions were determined through calorimetric titration, demonstrating spontaneous interactions, ΔG, exothermic enthalpic ΔH and positive entropy ΔS values. These favorable results for removal these toxic cations in a heterogeneous system may be useful for remove ions from wastewaters.

N-doped TiO2 visible light photocatalyst films via a sol–gel route using TMEDA as the nitrogen source

Abstract N-doped TiO 2 thin films were successfully prepared using N,N,N′,N′-tetramethylethane-1,2-diamine (TMEDA) via a single step sol–gel synthesis. Characterisation by X-ray diffraction and Raman spectroscopy confirmed that the anatase crystal type of TiO 2 was present in all samples. UV/Vis spectroscopy was used to determine the absorbance and band-gap of the materials. Stearic acid and resazurin dye Photo-degradation measurements were used to show the enhanced photocatalytic properties of the materials. Both of these methods are well known for the assessment of photocatalytic films for self cleaning applications with stearic acid being the preferred model for bacteria. The N-doped films showed superhydrophilicity under filtered white light conditions, whereas the undoped films did not show any photo-induced superhydrophilicity. The N-doped TiO 2 films show interstitial nitrogen content rather than substitutional and a substantial red-shift of the band-gap. They were shown to be superior visible light photocatalysts when compared to similar non-doped films. The nature of the chelating ligand, TMEDA, has a profound effect on the oxidation state of the Ti centres, with low concentrations of TMEDA promoting the formation of Ti 3+ centres giving a superior photocatalyst. This method is to the best of our knowledge the easiest, reliable and most reproducible one step route to achieve N-doped TiO 2 films for photocatalytic applications. These N-doped TiO 2 films could have potential applications; as self-cleaning surfaces in healthcare, water sterilisation, and solar energy harvesting.

Influence of the preparation method on the performance of CeO2–MoO3 catalyst for the selective catalytic reduction of NO with NH3

CeO2–MoO3 catalysts were prepared by three methods: single step sol–gel, homogeneous precipitation, hydrothermal. These catalysts were used for the selective catalytic reduction of NO with NH3 in the temperature range from 150 to 400 °C. The tested results suggested that the catalyst prepared by the hydrothermal method showed the higher NO conversion. The BET, XRD, H2-TPR, NH3-TPD and in situ DRIFTS characterization results indicated that the larger surface area, highly dispersed nanoctrystalline ceria, good redox ability and the stronger adsorption capacity for the NH3 should be the key factors to acquire the better NH3-SCR performance.

Low-temperature selective catalytic reduction of NO on CeO2–CuO/Al2O3 catalysts prepared by different methods

CeO2–CuO/Al2O3 catalysts were prepared by three different methods and their activities for selective catalytic reduction (SCR) of NO with NH3 were investigated. As can be seen from the experimental results, the catalyst prepared by the single-step sol–gel (SG) method showed the best SCR activity and resistance to SO2 and H2O. In order to investigate the relationship between the preparation method and the performance of SCR catalysts, the catalysts were characterized by using Brunauer–Emmett–Teller, X-ray diffraction, temperature programmed reduction with hydrogen, temperature programmed desorption with ammonia, X-ray photoelectron spectroscopy, Fourier transform infrared and thermo-gravimetric analysis techniques. It was found that the excellent performance of CeO2–CuO/Al2O3 catalyst prepared by the single-step SG method should be resulted from its large surface area, low crystallinity, high oxygen storage capacity, high NH3 adsorption capacity, high concentration of surface chemisorbed oxygen, weak sulphation process and weak water absorption.

Characterization of CeO2–WO3 catalysts prepared by different methods for selective catalytic reduction of NO with NH3

In this work, cerium–tungsten oxide catalysts were prepared by three methods: single step sol–gel (SG), impregnation (IM), and solid processing (SP). The catalysts were used for selective catalytic reduction (SCR) of NOx with ammonia over a wide temperature range. The results indicated that the catalysts prepared by the SP and IM methods exhibited better SCR activity than that prepared via the SG method in 175–500 °C. The excellent activity can be attributed to larger surface area, higher surface concentrations of Ce and Ce3 +, enhanced NO oxidization ability, and greater number of surface acid sites.

Photocatalytic reduction of carbon dioxide with water vapors over montmorillonite modified TiO2 nanocomposites

Montmorillonite (MMT) modified TiO2 nanocomposites were synthesized by single step sol–gel method. The samples were characterized by XRD, FE-SEM, HR-TEM, FT-IR, N2-adsorption–desorption, UV–vis and photoluminescence (PL) spectroscopy. Modification of TiO2 with MMT controlled the crystal growth and produced anatase phase of delaminated TiO2 pillared montmorillonite. The size of TiO2 nanoparticles reduced from 18.73 to 13.87nm after adding MMT, while the surface area and pore volume increased. The UV–vis results identified blue shift in TiO2 band gap for the MMT modified samples. In addition, PL spectroscopy revealed significant inhibition in recombination of photogenerated electron–hole pairs. The performance of MMT modified TiO2 samples for reducing CO2 with H2O to hydrocarbon fuels was investigated. The effects of parameters such as MMT loading on TiO2, H2O/CO2 feed ratios, and reaction temperature on TiO2 photocatalytic activity was studied. Loading MMT on TiO2 enhanced the performance of TiO2 and markedly increased CO2 reduction to C1–C3 hydrocarbon fuels. The highest yield rates produced were 441.5 and 103μmolgcat−1h−1 for CH4 and CO, respectively under UV light irradiations at 20wt.% MMT loading, reactor pressure of 0.20 bars and 393K reaction temperature. These results revealed silicate layers of MMT dispersed in the given TiO2 sol system and vacant d-orbits of the MMT transition metal ions have obvious effect on the photocatalytic activity of TiO2. The possible pathways and reaction mechanisms of CH4 and CO productions were also suggested. Thus, MMT is a potentially attractive material to improve TiO2 as a photocatalyst for application in photocatalytic CO2 reduction.

Effect of preparation methods on the performance of CeO2/Al2O3 catalysts for selective catalytic reduction of NO with NH3

CeO2/Al2O3 catalysts prepared by three methods were investigated for selective reduction of NO with NH3. It was found that the catalyst prepared by the single step sol–gel method had the best SCR activity and SO2 resistance performance. From the results of BET, XRD, TPD and TPR, it can be concluded that large surface area, strong interaction, highly dispersed nano-crystalline ceria, high NH3 adsorption capacity and good redox ability might be the main reasons for the excellent performance of CeO2/Al2O3 catalyst prepared by the single step sol–gel method.

Methanation of carbon dioxide over mesoporous Ni–Fe–Ru–Al2O3 xerogel catalysts: Effect of ruthenium content

Mesoporous nickel (35wt%)–iron (5wt%)–ruthenium (x wt%)–alumina xerogel (denoted as 35Ni5FexRuAX) catalysts with different ruthenium contents (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0) were prepared by a single-step sol–gel method for use in the methane production from CO2 and H2. Conversion of CO2, yield for CH4, metal surface area, and the amount of desorbed carbon dioxide of the catalysts showed volcano-shaped trends with respect to ruthenium content. Experimental results revealed that metal surface area and the amount of desorbed carbon dioxide of 35Ni5FexRu catalysts were well correlated with conversion of CO2 and yield for CH4.

Methanation of Carbon Dioxide Over Mesoporous Nickel–M–Alumina (M = Fe, Zr, Ni, Y, and Mg) Xerogel Catalysts: Effect of Second Metal

Mesoporous nickel (35 wt%)–M (5 wt%)–alumina xerogel (denoted as 35Ni5MAX) catalysts with different second metal (M = Fe, Zr, Ni, Y, and Mg) were prepared by a single-step sol–gel method for use in the methane production from carbon dioxide and hydrogen. In the carbon dioxide methanation reaction, yield for CH4 decreased in the order of 35Ni5FeAX > 35Ni5ZrAX > 35Ni5NiAX > 35Ni5YAX > 35Ni5MgAX. This indicated that the catalytic performance was greatly influenced by the identity of second metal in the carbon dioxide methanation reaction. Experimental results revealed that CO dissociation energy and metal-support interaction of the catalyst played key roles in determining the catalytic performance of 35Ni5MAX catalysts in the reaction. Among the catalysts tested, 35Ni5FeAX catalyst, which retained the most optimal CO dissociation energy and the weakest metal-support interaction, exhibited the best catalytic performance in terms of conversion of CO2 and yield for CH4. In the carbon dioxide methanation over mesoporous nickel–M–alumina xerogel catalysts with different second metal (M = Fe, Zr, Ni, Y, and Mg), yield for CH4 increased with decreasing TPSR peak temperature and with decreasing metal-support interaction of the catalyst.