Direct formation of thermally stabilized amorphous mesoporous Fe2O3/SiO2 nanocomposites by hydrolysis of aqueous iron III nitrate in sols of spherical silica particles

Nanocomposite materials containing 10% and 20% iron oxide/silica, Fe2O3/SiO2 (w/w), were prepared by direct hydrolysis of aqueous iron III nitrate solution in sols of freshly prepared spherical silica particles (St?ber particles) present in their mother liquors. This was followed by aging, drying, calcination up to 600 degrees C through two different ramp rates, and then isothermal calcinations at 600 degrees C for 3 h. The calcined and the uncalcined (dried at 120 degrees C) composites were characterized by thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption techniques, and scanning electron microscopy as required. XRD patterns of the calcined composites showed no line broadening at any d-spacing positions of iron oxide phases, thereby reflecting the amorphous nature of Fe2O3 in the composite. The calcined composites showed nitrogen adsorption isotherms characterizing type IV isotherms with high surface area. Moreover, surface area increased with the increasing of the iron oxide ratio and lowering of the calcination ramp rate. Results indicated that iron oxide particles were dispersed on the exterior of silica particles as isolated and/or aggregated nanoparticles. The formation of the title composite was discussed in terms of the hydrolysis and condensation mechanisms of the inorganic FeIII precursor in the silica sols. Thereby, fast nucleation and limited growth of hydrous iron oxide led to the formation of nanoparticles that spread interactively on the hydroxylated surface of spherical silica particles. Therefore, a nanostructured composite of amorphous nanoparticles of iron oxide (as a shell) spreading on the surface of silica particles (as a core) was formed. This morphology limited the aggregation of Fe2O3 nanoparticles, prevented silica particle coalescence at high temperatures, and enhanced thermal stability.     

Aerosol-assisted fabrication of mesoporous titania spheres with crystallized anatase structures and investigation of their photocatalitic properties

We demonstrate practical aerosol-assisted approach to synthesize spherical mesoporous titania particles with high surface areas. Scanning electron microscopy observation of the spray-dried products clearly shows spherical morphology. To remove surfactants and enhance crystallinity, the spray-dried products are calcined under various temperatures. The crystalline structures inside the particles are carefully detected by wide-angle XRD measurements. With increase of the calcination temperatures, anatase crystal growth proceeds and transformation from anatase to rutile is occurred. The effect of various calcination temperatures on the mesostructures is also studied by using N₂ adsorption desorption isotherms. The mesoporous titania particles calcined at 350, 400, and 500 °C exhibit type IV isotherms with a capillary condensation step and shows a hysteresis loop, which is a characteristic of mesoporous materials. The reduction in the surface areas and the pore volumes is confirmed by increasing the calcination temperatures, while the average pore diameters are increased gradually. This is attributed to the distortion of the mesostructures due to the grain growth of the anatase phase and the transformation to the rutile phase during the calcination process. As a preliminary experimental photocatalytic activity, oxidative decomposition of acetaldehyde under UV irradiation is examined. The mesoporous titania calcined at 400 °C shows the highest photocatalytic activity, due to both high surface area and well-developed anatase crystalline phase.     

Simple route to monodispersed silica-titania core-shell photocatalysts

A monodispersed silica-titania core-shell photocatalyst was synthesized via a sol-gel route without the need of pH adjustment, cationic polyelectrolytes, or surfactants in a process where silica spheres were impregnated with hydrolyzed titanium tetrabutoxide, incubated at room temperature, and then condensed using an ethanol/water (1:1) solvent. Four coating cycles in a 10% v/v titania sol produced homogeneous titania shells. The quality of catalysts was assessed quantitatively using Rietveld analysis of powder X-ray diffraction patterns combined with X-ray fluorescence spectrometry. During calcination, the anatase-to-rutile transformation was delayed to 1000 degrees C, which is approximately 300 degrees C higher than usually observed. The thermal stability and surface area of titania were enhanced through the slow crystal growth of anatase. The photocatalytic activity of the core-shell photocatalysts calcined at 400-600 degrees C was found to be proportional to the thickness of titania but did not directly correlate with the surface area.     

Synthesis and characterization of mesoporous ceria/alumina nanocomposite materials via mixing of the corresponding ceria and alumina gel precursors

Mesoporous ceria/alumina, CeO(2)/Al(2)O(3), composites containing 10, 20 and 30% (w/w) ceria were prepared by a novel gel mixing method. In the method, ceria gel (formed via hydrolysis of ammonium cerium(IV) nitrate by aqueous ammonium carbonate solution) and alumina gel (formed via controlled hydrolysis of aluminum tri-isopropoxide) were mixed together. The mixed gel was subjected to subsequent drying and calcination for 3 h at 400, 600, 800 and 1000 degrees C. The uncalcined (dried at 110 degrees C) and the calcined composites were investigated by different techniques including TGA, DSC, FTIR, XRD, SEM and nitrogen adsorption/desorption isotherms. Results indicated that composites calcined for 3 h at 800 degrees C mainly kept amorphous alumina structure and gamma-alumina formed only upon calcinations at 1000 degrees C. On the other hand, CeO(2) was found to crystallize in the common ceria, cerinite, phase and it kept this structure over the entire calcination range (400-1000 degrees C). Therefore, high surface areas, stable surface textures, and non-aggregated nano-sized ceria dispersions were obtained. A systematic texture change based on ceria ratio was observed, however in all cases mesoporous composite materials exposing thermally stable texture and structure were obtained. The presented method produces composite ceria/alumina materials that suit different applications in the field of catalysis and membranes technology, and throw some light on physicochemical factors that determine textural morphology and thermal stability of such important composite.     

New route to synthesize highly active nanocrystalline sulfated titania-silica: synergic effects between sulfate species and silica in enhancing the photocatalysis efficiency

A simple and efficient approach has been set up for fabricating highly active sulfated titania-silica (SO(4)(2-)/TiO(2)-SiO(2)): Ti(SO(4))(2) was hydrolyzed in the presence of silica, making it possible to sulfate titania and form titania-silica mixed oxide in one step. This study was focused on investigating the roles of sulfate species and silica in improving the physicochemical properties and photoactivity of SO(4)(2-)/TiO(2)-SiO(2) through comparison with sulfated titania (SO(4)(2-)/TiO(2)) and sulfate-free catalysts (TiO(2) and TiO(2)-SiO(2)). Various characterization methods, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and surface photovoltage spectroscopy (SPS), were employed to test these materials. The results revealed that for SO(4)(2-)/TiO(2) and TiO(2)-SiO(2) the sole presence of either sulfate species or silica imposes negative effects on the photocatalysis behavior of titania, leading them to have negligible photoactivities. On the contrary, in the case of SO(4)(2-)/TiO(2)-SiO(2), sulfate species and silica were proved to act in a cooperative manner; therefore, the following enhanced structure and surface properties of SO(4)(2-)/TiO(2)-SiO(2) were obtained: (i) relatively well-crystallized and smaller-size (15.4 nm) anatase-phase titania was formed upon 500 degrees C calcination without forming rutile phase and (ii) the formation of active surface sulfate species promotes the separation of photoinduced electron-hole pairs and therefore accelerates the photocatalysis reaction. Therefore, its photoactivity is enhanced as a result of the favorable synergic effects between sulfate species and silica due to their simultaneous presence.     

Formation and characterization of different ceria/silica composite materials via dispersion of ceria gel or soluble ceria precursors in silica sols

Composite ceria/silica materials of 10 and 20% (w/w) were prepared by calcination, at 650 degrees C for 3 h, of the xerogels obtained by mixing the corresponding amount of a ceria precursor with freshly prepared sols of spherical silica particles (Stober particles) in their mother liquors. Two different ceria precursors were examined in this investigation. The first was a gel produced by the prehydrolysis of cerium(IV) isopropoxide in isopropanol medium, and the second was an aqueous solution of cerium(IV) ammonium nitrate. Different textural and morphological characteristics that developed by calcination were investigated by TGA, FTIR, XRD, SEM, and analyses of N2 adsorption isotherms. The results indicated that ceria dispersion and formation of mesoporous textural composite materials produced by the second precursor, cerium(IV) ammonium nitrate, are better than those produced by the first precursor, prehydrolyzed cerium(IV) isopropoxide. The results are discussed in terms of the effect of precursors and mixing media on nucleation and growth of ceria particles and their protection from sintering on calcination at the test temperature.     

Distribution of macropores in silica particles prepared by using multiple emulsions

The distribution of macropores in silica particles prepared by the hydrolysis and condensation of TEOS in a hexane/water/decyl alcohol (O(1)/W/O(2)) multiple emulsion was investigated. To stabilize the emulsion structure, hydroxypropyl cellulose (HPC) was added into the O(2) phase and polyethylene glycol (PEG) was added into the water phase. Without HPC, the particles have an irregular shape and hardly have particulate forms. As the concentration of HPC increases, the shape of particles becomes more and more spherical and the size decreases. The size of silica particles was varied from 5 to 1 microm as the concentration of HPC increased from 0.5 to 0.7 wt%. The number and size of the macropores in silica particles were affected by PEG polymer concentration. With the variation in the concentration of PEG, macropores in silica particles were located at the surface of or inside the particles. At high concentrations of PEG, the macropores in particles were located inside the particles, but at low concentrations of PEG the macropores were located at the surfaces of particles. Interestingly, the particles of dimpled surfaces were formed when the molar ratio of water to TEOS (R(w)) was 4.0 and the concentrations of PEG and HPC were 2.0 and 0.7 wt% respectively. The surface areas of dimpled silica particles and completely spherical particles, measured by the BET method, were 409 and 433 m(2)/g respectively.     

Surfactant mediated synthesis of spherical binary oxides photocatalytic with enhanced activity in visible light

Spherical silica and zirconia mixed titania and pure titania samples were prepared in presence of cetyltrimethylammonium bromide (CTAB) through controlled hydrolysis of corresponding metal alcoxides. Effect of surfactant amount and calcinations temperature on morphology, surface area and photocatalytic activity is studied using PXRD, SEM, FTIR, Solid state UV-vis spectroscopy and BET surface area. It is well observed that in presence of 2 mol% CTAB, uniform sized spherical oxide particles can be synthesized. However, increasing or decreasing the surfactant amount does not favor the spherical particle formation. Material synthesis in presence of CTAB not only helps in the spherical particle formation but also increases the surface area and visible light absorption. Studies on photocatalytic lead removal with respect to calcination temperature indicate that the calcination at 500 degrees C is most suitable for the best photocatalytic activity. Mixing of zirconia and silica helps in anatase phase stabilization even at 900 degrees C calcination. Accordingly low decrease in surface area even at 900 degrees C calcination is observed. Due to the phase stabilization and higher surface area binary oxide materials showed comparatively better photocatalytic activity even after calcination at 900 degrees C. So it can be concluded that present synthesis approach can produce uniform sized spherical binary oxide materials with better photocatalytic activity in visible light.     

Synthesis and characterization of Nano titania particles embedded in mesoporous silica with both high photocatalytic activity and adsorption capability

TiO(2)-xSiO(2) composites with a high specific surface area (up to 645 m(2)/g), large pore volume, and narrow distribution with average pore sizes ranging from 15 to 20 A have been synthesized by the sol-gel method. The results of characterization by XRD, BET, TEM, FTIR, and DRUV reveal that these TiO(2)-xSiO(2) composites exhibit a core/shell structure of a nano titania/Ti-O-Si species modified titania embedded in mesoporous silica. As compared to pure anatase, the embedding of nano titania particles into the mesoporous silica matrix results in a substantial blue shift of absorption edge from 3.2 to 3.54 eV and higher UV absorption intensity, which are attributed to the formation of the Ti-O-Si species modified titania in the interface between titania and silica. The as-synthesized TiO(2)-xSiO(2) composites exhibit both much higher absorption capability of organic pollutants and better photocatalytic activity for the photooxidation of benzene than pure titania. The better photocatalytic activity of as-synthesized TiO(2)-xSiO(2) composites than pure titania is attributed to their high surface area, higher UV absorption intensity, and easy diffusion of absorbed pollutants on the absorption sites to photogenerated oxidizing radicals on the photoactive sites.     

Preparation of ordered mesoporous SiC from preceramic polymer templated by nanoporous silica

Highly ordered mesoporous SiC materials were prepared by infiltrating viscous liquid preceramic polymer, allylhydridopolycarbosilane, into two types of surface modified nanoporous silica templates: mesoporous silica SBA-15 and mesocellular siliceous foam. The silica templates were subsequently etched off after pyrolysis at 1000 degrees C under nitrogen atmosphere with the resultant formation of ordered mesoporous structures. The mesoporous SiC materials, synthesized from both types of templates possessed high Brunauer-Emmett-Teller (BET) surface areas in the range of 250-260 m(2)/g with pore sizes of 3.4-3.6 nm. The ordered structures of mesoporous SiC were exact inverse replicas of their respective silica templates, as characterized by small angle X-ray diffraction (XRD), transmission electron microscope (TEM) images, and the adsorption-desorption isotherm of nitrogen.     

Fabrication of hydroxyl group modified monodispersed hybrid silica particles and the h-SiO(2)/TiO(2) core/shell microspheres as high performance photocatalyst for dye degradation

The monodisperse hybrid silica particles (h-SiO(2)) were firstly prepared by a modified sol-gel process and the surface was modified in situ with double bonds, then abundant carboxyl moieties were introduced onto the surface of the silica core via thiol-ene click reaction. Afterward, the h-SiO(2)/TiO(2) core/shell microspheres were prepared by hydrolysis of titanium tetrabutoxide (TBOT) via sol-gel process in mixed ethanol/acetonitrile solvent, in which the activity of TBOT could be easily controlled. The carboxyl groups on the surface of silica particles promote the formation of a dense and smooth titania layer under well control, and the layer thickness of titania could be tuned from 12 to 100nm. The well-defined h-SiO(2)/TiO(2) core/shell structures have been confirmed by electron microscopy and X-ray photoelectron spectroscopy studies. After calcination at 500°C for 2h, the amorphous TiO(2) layer turned into anatase titania. These anatase titania-coated silica particles showed good photocatalytic performance in degradation of methyl orange aqueous solution under UV light.     

Synthesis of titanium dioxide nanoparticles with mesoporous anatase wall and high photocatalytic activity

Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6 nm with mean pore size of 2.1 nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430 m2/g and that of the samples after calcination at 600 degrees C still have 221.9 m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400 degrees C.     

Synthesis and photocatalytic activity of mesoporous TiO(2) with the surface area, crystallite size, and pore size

Mesoporous TiO(2) materials with various pore-size distributions were synthesized by using diblock copolymers via a sol-gel process in aqueous solution. The properties of these materials were characterized by FE-SEM, HR-TEM, XRD, DRS, BET, and BJH analysis. All particles have spherical morphology with a diameter range of 1-3 mum. The mesoporous TiO(2) materials calcined at 400 degrees C were found to have different specific surface areas - 186, 210, and 192 m(2) g(-1) - and average pore sizes depending on the type of diblock copolymer-5.1, 6.1, and 6.4 nm-and their crystallite sizes were found to be 8.1, 8.3, and 8.8 nm. The photocatalytic activity of each sample was investigated by measuring the photodecomposition of methylene blue (MB), and the small crystallite size, large surface area, and small pore size were found to exhibit better photocatalytic activities. In addition, the photocatalytic activities of all the mesoporous TiO(2) materials were found to be better than that of commercial TiO(2).     

Three-dimensional low symmetry mesoporous silica structures templated from tetra-headgroup rigid bolaform quaternary ammonium surfactant

Two kinds of highly ordered mesoporous silica materials (FDU-11, FDU-13) with novel three-dimensional (3-D) tetragonal and orthorhombic structures were synthesized by using tetra-headgroup rigid bolaform quaternary ammonium surfactant [(CH(3))(3)NCH(2)CH(2)CH(2)N(CH(3))(2)CH(2)(CH(2))(11)OC(6)H(4)C(6)H(4)O(CH(2))(11)CH(2)N(CH(3))(2)CH(2)CH(2)CH(2)N(CH(3))(3).4Br] (C(3-12-12)(-)(3)) as a template under alkaline conditions. High-resolution transmission electron microscopy (HRTEM), small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD) show that mesoporous silica FDU-11 has primitive tetragonal P4/mmm structure with cell parameters a = b = 8.46 nm, c = 5.22 nm, and c/a ratio = 0.617. N(2) sorption isotherms show that calcined FDU-11 has a high BET surface area of approximately 1490 m(2)/g, a uniform pore size of approximately 2.72 nm, and a pore volume of approximately 1.88 cm(3)/g. Mesoporous silica FDU-13 has primitive orthorhombic Pmmm structure. The cell parameters are a = 9.81, b = 5.67, and c = 3.66 nm. N(2) sorption isotherms show that calcined FDU-13 has a high BET surface area of 1210 m(2)/g, a uniform mesopore size of approximately 1.76 nm, and a large pore volume of approximately 1.83 cm(3)/g. Such low symmetries for 3-D mesostructures (tetragonal and orthorhombic system) have not been observed before even in amphiphilic liquid crystals, which maybe resulted from an oblate aggregation of the bolaform surfactant and its strong electrostatic interaction with inorganic precursor. A probable mechanism has been proposed for the formation of such a 3-D low symmetrical mesostructure. These results will further extend the synthesis of mesoporous materials and may open up new opportunities for their new applications in catalysis, separation, and nanoscience.     

Influence of morphology and composition of fumed oxides on changes in their structural and adsorptive characteristics on hydrothermal treatment in steam phase at different temperatures

A series of fumed oxides such as silica, titania, alumina, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST), initial and hydrothermally treated (HTT) in the steam phase at T(HTT)=150, 250, and 350 degrees C was studied by adsorption, AFM, XRD, FTIR, and theoretical methods. Diminution of the size of primary particles (corresponding to increasing S(BET)) of initial silica and mixed oxides results in enhancement of their structural changes on HTT with elevating T(HTT) and increasing density of packing of primary particles in the secondary structures. Relative changes in the texture of treated fumed silicas are smaller than those of mesoporous silica gels occurring under similar HTT conditions. On HTT, aggregates of primary particles and their agglomerates become denser but their surface layers become looser because of transfer of silica fragments from one particle to another, and the smaller the initial primary particles, the greater the relative diminution of the specific surface area S(BET) for the same type of primary particle packing in aggregates. Relative changes in the pore volume V(p) (or V(BJHd)) on HTT are more complex than that of S(BET), as for many samples the V(p) value increases especially at T(HTT)=150 degrees C. Alumina and titania partially inhibit structural changes on HTT, which decrease in the series silica > SA > AST approximately ST.     

Physicochemical Characterization and Catalytic Properties of Titania Gel Doped with Lithium and Rubidium

The effect on titania of doping with lithium and rubidium titania gels has been studied in samples prepared with titanium (IV) tetra-n-butoxide co-gelling with the alkaline metal precursors. Titania and doped titania were characterized by X-Ray diffraction, which showed that the catalysts were nanostructured. In samples calcined at 400°C, the crystallite size of the anatase phase was 17 and 14 nm, and 78 and 38 nm for samples calcined at 600°C, for Li/TiO₂ and Rb/TiO₂, respectively. The specific surface areas of doped samples (400°C) are lower in Li/TiO₂ (90 m²/g) than in Rb/TiO₂(125 m²/g). Evaluation of their basic properties has been carried out in the acetone condensation reaction. It was found that the activity strongly depended on the Li and Rb ionic radii.     

Preparation of mesostructured barium sulfate with high surface area by dispersion method and its characterization

The spherical and cubic mesoporous BaSO(4) particles with high surface area were successfully produced via one-step process through precipitation reaction in aqueous solution of Ba(OH)(2) and H(2)SO(4) with ethylene glycol (n-HOCH(2)CH(2)OH) as a modifying agent. The BaSO(4) nanomaterial revealed that the high surface area and the mesoporous was stable up to 400 degrees C. Agglomerate mesoporous barium sulfate nanomaterials were obtained by the reaction of Ba(2+) and SO(2-)(4) with ethylene glycol aqueous solution. The ethylene glycol was used to control the BaSO(4) particle size and to modify the surface property of the particles produced from the precipitation. The dried and calcined mesoporous BaSO(4) nanomaterials were characterized by X-ray diffraction (XRD), BET surface area and N(2) adsorption-desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared resonance (FTIR) and thermogravimetric analysis (TGA). The as-prepared mesoporous dried BaSO(4) possesses a high BET surface area of 91.56 m(2) g(-1), pore volume of 0.188 cm(3) g(-1) (P/P(0)=0.9849) and pore size of 8.22 nm. The SEM indicates that the morphology of BaSO(4) nanomaterial shows shell like particles up to 400 degrees C, after that there is drastically change in the material due to agglomeration. Synthesis of mesoporous BaSO(4) nanomaterial is of significant importance for both sulphuric acid decomposition and oxidation of methane to methanol.     

Characterization and evaluation of the photocatalytic properties of wormhole-like mesoporous silica incorporating TiO2, prepared using different hydrothermal and calcination temperatures

TiO₂?CSiO₂ mesoporous materials were synthesised by deposition of TiO₂ nanoparticles prepared by the sol?Cgel method on to the internal pore surface of wormhole-like mesoporous silica. In this work we synthesised wormhole-like mesoporous silica of different surface area by changing the hydrothermal temperature (70, 100, or 130?°C). Subsequent to this, titania solution was deposited on to the inner surface of the pores and this was followed by calcination at different temperatures (400, 600, or 800?°C). The effect of different hydrothermal and calcination temperature on the photocatalytic properties was evaluated. The samples were characterized by N₂-sorption, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The effect of different hydrothermal and calcination temperatures on the photocatalytic properties was evaluated by measuring the degradation of methylene blue in aqueous solution under UV light irradiation (mercury lamp, 125?W). The results indicated that appropriate surface area and degree of crystallinity are two important factors for obtaining high photocatalytic efficiency. Samples prepared at a hydrothermal temperature of 100?°C and calcined at 800?°C had the best photocatalytic performance, because of the highest surface area and high crystallinity.     

Thermal wetting of platinum nanocrystals on silica surface

Thermal stability of facetted Pt nanocrystals on amorphous silica support films was investigated using in situ transmission electron microscopy in a temperature range between 25 and 800 degrees C. The particles started to change their shapes at approximately 350 degrees C. Above 500 degrees C, the particles spread on the support film with increasing temperature, rather than becoming more spherical. Such temperature-induced wetting of Pt nanoparticles on silica surface can be attributed to the interfacial mixing of Pt and SiO(2) and the resulting negative interface energy.     

High surface area sol–gel alumina–titania nanocatalyst

Alumina–titania mixed oxide nanocatalysts with molar ratios = 1:0.5, 1:1, 1:2, 1:5 have been synthesized by adopting a hybrid sol–gel route using boehmite sol as the precursor for alumina and titanium isopropoxide as the precursor for titania. The thermal properties, XRD phase analysis, specific surface area, adsorption isotherms and pore size details along with temperature programmed desorption of ammonia are presented. A specific surface area as high as 291 m²/g is observed for 1:5 Al₂O₃/TiO₂ composition calcined at 400 °C, but the same composition when calcined at 1,000 °C, resulted in a surface area of 4 m²/g, while 1:0.5 composition shows a specific surface area of 41 m²/g at 1,000 °C. Temperature programmed desorption (of ammonia) results show more acidic nature for the titania rich mixed oxide compositions. Transmission electron microscopy of low and high titania content samples calcined at 400 °C, shows homogeneous distribution of phases in the nano range. In the mixed oxide, the particle size ranges between 10–20 nm depending on titania content. The detailed porosity data analysis contributes very much in designing alumina–titania mixed oxide nanocatalysts.