Preparation of Ag-doped mesoporous titania and its enhanced photocatalytic activity under UV light irradiation

Ag-doped mesoporous titania was synthesized via a combined sol-gel process with surfactant-assisted templating method using cetyltrimethyl ammonium bromide (CTAB) as the structure-directing agent. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂ adsorption-desorption measurements (BET) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the samples was determined by degradation of model contaminant water of phenol in aqueous solution. Results showed that different amounts of Ag-doping had different effects on the crystal phase structure and photocatalytic activity of the samples. The sample with 0.5% Ag doping shows the highest photocatalytic activity, which is 2.3 times that of the undoped mesoporous titania.     

Chemical synthesis of nano-porous ruthenium oxide (RuO2) thin films for supercapacitor application

Ruthenium oxide (RuO₂) thin films have been prepared using single step chemical method containing Ru(III) Cl₃ solution in an aqueous medium at low temperature. The structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and optical absorption technique. The XRD study revealed the formation of amorphous RuO₂ thin film. The surface examination by SEM showed formation of nano-porous material on the substrate. The TEM study revealed the formation of nanostructured material. The optical absorption studies showed the presence of direct band transition with band gap equal to 2.2 eV. The RuO₂ has proved its applicability in supercapacitor showing 50 F/g specific capacitance in 0.5 M H₂SO₄ at 20 mV/s scan rate.     

Synthesis, characterization, and oxygen sensing properties of Ru(II) complex covalently grafted to mesoporous MCM-41

Novel oxygen sensing materials consisting of [Ru(Bphen)₂bpy]²⁺ (Bphen=4,7-diphenyl-1,10-phenanthroline, bpy=2,2′-bipyridyl) portion covalently grafted to the backbones of the ordered functionalized mesoporous MCM-41 are synthesized by co-condensation of tetraethoxysilane (TEOS) and the functionalized Ru(II) complex [Ru(Bphen)₂Bpy-Si]²⁺ using surfactant cetyltrimethylammoniumbromide (CTAB) as template. The Bpy-Si was used as not only one of the precursors of the sol-gel process but also the second ligand of Ru(Bphen)₂Cl₂·2H₂O complex to prepare the functionalized mesoporous materials for oxygen sensors. Dye leaching shortcoming is overcome due to the Si-C bonds. The derivative mesoporous oxygen sensing materials are characterized by Fourier transform infrared (FT-IR), small angle X-ray diffraction (SAXRD), luminescence intensity quenching Stern-Volmer plots, and excited-state decay analysis. The mesoporous materials show higher sensitivity to the O₂ concentration in N₂ (I₀/I₁₀₀=23.2) and shorter response time (1.2 s) in comparison with those based on sol-gel method. When the concentration of oxygen is 10%, the luminescence intensity of the oxygen sensor can be quenched by 89.9%, suggesting that it is highly sensing at low concentration of oxygen.     

The growth mechanism and supercapacitor study of anodically deposited amorphous ruthenium oxide films

In the present study, ruthenium oxide (RuO₂) thin films were deposited on the stainless steel (s.s.) substrates by anodic deposition. The nucleation and growth mechanism of electrodeposited RuO₂ film has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive analysis by X-rays (EDAX) for structural, morphological, and compositional studies. The electrochemical supercapacitor study of ruthenium oxide thin films have been carried out for different film thicknesses in 0.5 M H₂SO₄ electrolyte. The highest specific capacitance was found to be 1190 F/g for 0.376 mg/cm² film thickness.     

Catalytic conversion of air-methane flow by nanostructured ruthenium dioxide: FTIR spectroscopy and modeling

Nanostructured powders of ruthenium dioxide RuO₂ were synthesized via a sol-gel route involving acidic solutions with pH varying between 0.4 and 4.5. The RuO₂ nanopowders were characterized by X-ray diffraction. Crystallite sizes measured from X-ray diffraction profiles and TEM analysis varied in the range 8-16 nm, with a minimum of crystallite dimension for pH 1.5. Catalytic conversion of methane by these RuO₂ nanostructured catalysts was studied as a function of pH, catalytic interaction time, air methane composition, and catalysis temperature, by the way of Fourier transform infrared (FTIR) spectroscopy coupled to homemade catalytic cell. The catalytic efficiency defined as FTIR absorption band intensities I(CO₂) was maximum for sample prepared at pH 1.5, and mainly correlated to crystallite dimensions. A modeling approach of catalytic conversion is proposed for such a specific experimental configuration.     

Investigation of structural and magnetic properties of Ni, NiFe and NiFe2O4 thin films

Soft magnetic thin films of Ni, NiFe and NiFe₂O₄ were prepared using reactive magnetron sputtering in various deposition conditions. Experimentally observed soft magnetic property was compared and correlated with nanocrystalline structure evolution. Ni and NiFe deposited films are textured with fcc(111) phase preferred orientation. Accordingly, grain size and lattice parameter were calculated from X-ray diffraction (111) peak line width and 2θ peak position. Addition of reactive gas oxygen in deposition process has substantial effect on crystalline structure of film. There is phase transition from the ordered NiFe (111) structure to the NiFe₂O₄ nanocrystalline phase. The resulting film has shown small X-ray diffraction intensity peak corresponding to (311) and (400) orientation, indicating small amount of existing NiFe₂O₄ phase. The mechanism has been discussed to be responsible for nanocrystallization and amorphization of NiFe₂O₄ films. Magnetic measurement (M-H) loop reveal soft magnetic nature of films with magnetic anisotropy. The coercivity (H_c) of films is in accordance with random anisotropy model, where H_c reduced with grain size. The structural transformation was supported by Fourier transforms infrared spectroscopy measurement. The films are highly smooth with surface roughness in the range of ∼0.53-0.93 nm. NiFe₂O₄ films have shown lowest surface roughness with highest electrical resistivity values. The structural, surface, magnetic and infrared spectroscopy results are observed and analyzed.     

Effects of non-stoichiometric RuO x thin films on the dielectric properties of BaTiO3 thin films

The deconvolution process of X-ray photoemission spectra for O 1s and Ru 3d, X-ray diffraction and Rutherford backscattering spectrometry reveal that the RuO _x films (x = 2.0 – 2.2) deposited at a O₂ partial pressure less than 30% show (110)-oriented grains, whereas the RuO _x films (x = 2.3 – 2.4) deposited at a 40–50% O₂ partial pressure show amorphous and (101)-oriented grains due to the excess O interstitials and RuO₃ or RuO₄. These differences in the crystal phases of RuO _x influence the crystal structure of BaTiO₃ deposited on these RuO _x bottom electrodes, resulting in a higher dielectric constant and a lower dissipation factor for tetragonal BaTiO₃/RuO _x (x = 2.1) than amorphous BaTiO₃/RuO _x (x = 2.4).     

CTAB assisted growth and characterization of nanocrystalline CuO films by ultrasonic spray pyrolysis technique

An aqueous solution of cupric nitrate trihydrate (Cu(NO₃)₂·3H₂O) modified with cetyltrimetylammonium bromide (CTAB) is used to deposit CuO films on glass substrate by chemical spray pyrolysis technique. The thermal analysis shows that the dried CTAB doped precursor decomposes by an exothermic reaction and suggests that minimum substrate temperature for film deposition should be greater than 270 °C. X-ray diffraction (XRD) studies indicate the formation of monoclinic CuO with preferential orientation along (0 0 2) plane for all film samples. The CTAB used as cationic surfactant in precursor results in the suppression of grain growth in films along the (1 1 0), (0 2 0) and (2 2 0) crystal planes of CuO. Surfactant modified films showed an increase in crystallite size of 14 nm at substrate temperature of 300 °C. The scanning electron micrographs (FESEM) confirm the uniform distribution of facets like grains on the entire area of substrate. CTAB modified films show a significant reduction in the particle agglomeration. Electrical studies of the CuO films deposited at substrate temperature of 300 °C with and without surfactant reveal that the CTAB doping increase the activation energy of conduction by 0.217 eV and room temperature response to ammonia by 9%. The kinetics of the ammonia gas adsorption on the film surface follows the Elovich and Diffusion models.     

Facile preparation of superhydrophobic copper surface by HNO3 etching technique with the assistance of CTAB and ultrasonication

Superhydrophobic rough structure was prepared on copper wafer via HNO₃ etching technique with the assistance of Cetyltrimethyl Ammonium Bromide (CTAB) and ultrasonication. After modification of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTES), the copper wafer showed stable superhydrophobicity. The morphologies, chemical compositions and hydrophobicity of the substrates were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. Dense and spherical micropits appeared on copper wafer after it was etched by 5 M nitric acid with 1.2 mM CTAB under ultrasonication for 20 min. The SEM results indicated that the joint action of CTAB and ultrasonication caused the formation of dense and spherical micropits.     

Influence of Fe ions in characteristics and optical properties of mesoporous titanium oxide thin films

Fe-doped mesoporous titanium dioxide (M-TiO₂-Fe) thin films have been prepared on indium tin oxide (ITO) glass substrates by sol–gel and spin coating methods. All films exhibited mesoporous structure with the pore size around 5–9 nm characterized by small angle X-ray diffraction (SAXRD) and further confirmed by high resolution transmission electron microscopy (HRTEM). Raman spectra illustrated that lower Fe-doping contributed to the formation of nanocrystalline of M-TiO₂-Fe thin films. X-ray photoelectron spectroscopy (XPS) data indicated that the doped Fe ions exist in forms of Fe³⁺, which can play a role as e⁻ or h⁺ traps and reduce e⁻/h⁺ pair recombination rate. Optical properties including refractive indices/n, energy gaps/E_g and Urbach energy width/E₀ of the thin films were estimated and investigated by UV/vis transmittance spectra. The presence of Fe content extended the light absorption band and decreased the values of n, implying enhanced light response and performance on dye-sensitized solar cells (DSSC). The optimum Fe content in M-TiO₂-Fe thin films is determined as 10 mol%, for its compatibility of well crystalline and well potential electron transfer performance.     

Catalytic behaviors of ruthenium dioxide films deposited on ferroelectrics substrates, by spin coating process

Catalytic ruthenium dioxide films were deposited by spin-coating process on ferroelectric films mainly constituted of SrBi₂Ta₂O₉ (SBT) and Ba₂NaNb₅O₁₅ (BNN) phases. After thermal treatment under air, these ferroelectric-catalytic systems were characterized by X-ray diffraction and scanning electron microscopy (SEM). SEM images showed that RuO₂ film morphology depended on substrate nature. A study of CH₄ conversion into CO₂ and H₂O was carried out using these catalytic-ferroelectric multilayers: the conversion was analyzed from Fourier transform infrared (FTIR) spectroscopy, at various temperatures. Improved catalytic properties were observed for RuO₂ films deposited on BNN oxide layer.     

Selective ethanol gas sensing behavior of mesoporous n-type semiconducting FeNbO4 nanopowder obtained by niobium–citrate process

Beyond the most investigated mesoporous silica and carbon based materials, metal oxides have attracted considerable interest due to their more diverse electronic functionality, which includes gas sensing activities, semiconductor characteristics and magnetic properties. In this paper, we describe the fabrication, characterization and application of mesoporous FeNbO₄ nanopowder for ethanol gas sensing application. FeNbO₄ nanopowder was synthesized via the niobium–citrate complex method, without using any surfactant and size selection medium. Thermal stability and structure of the nanopowder was analyzed by thermogravimetric analysis (TG/DTA) and X-ray diffraction analysis (XRD). Structural analysis confirmed the formation of FeNbO₄ with monoclinic structure. The particle size, electrical and optical properties were also systemically investigated by means of transmission electron microscopy (TEM), impedance and diffused reflectance spectra. Nitrogen adsorption isotherms of the FeNbO₄ were type IV with hysteresis loops of type H₃ indicating well-defined pore structure with mesoporous nature. The sensing characteristics of FeNbO₄ nanopowder such as sensitivity, operating temperature and response time, were studied in the presence of ethanol (C₂H₅OH). Experimental result confirmed that a higher response to ethanol at relatively lower operating temperature of 200 °C.     

Microwave synthesis and textural property of europium substituted mesoporous molecular sieves

Using cetyltrimethyl ammonium bromide (CTAB) as the template and sodium silicate as the silicon source, the MCM-41 mesoporous molecular sieves with Eu incorporated in the framework were synthesized under microwave irradiation condition and the influence of the Si/Eu molar ratio on the crystalline structure, textural properties and the long-range ordering of the resulting sample was investigated by various physicochemical techniques such as X-ray diffraction (XRD), transmission electron microscope (TEM), diffuse reflectance ultraviolet-visible spectroscopy (UV-vis), thermal gravimetric-differential scanning calorimeter (TG-DSC) and N₂ physical adsorption. The results of N₂ adsorption and XRD reveal that the synthesized sample has the ordered hexagonal mesoporous structure. UV-vis spectra provide the strong evidences that most of europium ions were incorporated into the framework of the MCM-41 sample. The crystalline structure, textural properties and mesoporous ordering of the resultant mesoporous materials are related to the amount of europium incorporation. Small amount europium incorporated into the silica-based MCM-41 does not strongly modify the structure of mesoporous molecular sieve. An increase of the Eu content in sample led to reduction of the specific surface area and the deterioration of the long-range ordering.     

Preparation, characterization, and luminescence properties of novel hybrid material containing europium(III) complex covalently bonded to MCM-41

In this paper, a novel luminescent organic-inorganic hybrid material containing covalently bonded ternary europium complex in mesoporous silica MCM-41 has been successfully prepared by co-condensation of tetrethoxysilane (TEOS) and the modified ligand 2-phenyl-1H-imidazo[4,5-f][1,10]phen-3-(triethoxysilyl)propylcarbamate (PIP-Si) in the presence of cetyltrimethylammonium bromide (CTAB) surfactant as template. PIP-Si containing 1,10-phenanthroline covalently grafted to 3-(triethoxysilyl)propyl isocyanate is used not only as a precursor but also as the second ligand for Eu(TTA)₃·2H₂O (TTA: 2-thenoyltrifluoroacetate) complex to prepare a novel functionalized mesoporous material. The resulted mesoporous composite materials, which demonstrate strong characteristic emission lines of Eu³⁺⁵D₀-⁷F_J (J=0, 1, 2, 3, 4), were characterized by Fourier transform infrared (FT-IR), small-angle X-ray diffraction, excited-state decay analysis. Emission intensity of the Eu(III) complex covalently linked to MCM-41 (Eu-MCM-41) increases with the increasing irradiation time, demonstrating better photostability compared with both pure Eu(III) complex and physically incorporated sample.     

Preparation and characterization of electrodeposited SnS thin films

Tin sulfide (SnS) thin films have been deposited by electrodeposition using potentiostaic method on indium doped tin oxide (ITO) coated glass substrates from aqueous solution containing SnCl₂·2H₂O and Na₂S₂O₃ at various potentials. Good quality thin films were obtained at a cathodic potential −1000 mV versus saturated calomel electrode (SCE). The deposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR). X-ray diffraction analysis shows that the crystal structure of SnS thin films is orthorhombic with preferential orientation along 〈0 2 1〉 plane. Microstructural parameters such as crystallite size, micro strain, and dislocation density are calculated and found to depend upon cathodic potentials. SEM studies reveal that the SnS films exhibited uniformly distributed grains over the entire surface of the substrate. The optical transmittance studies showed that the direct band gap of SnS is 1.1 eV. FTIR was used to further characterize the SnS films obtained at various potentials.     

Synthesis and characterization of superhydrophobic functionalized Cu(OH)2 nanotube arrays on copper foil

Superhydrophobic functionalized cupric hydroxide (Cu(OH)₂) nanotube arrays were prepared on copper foils via a facile alkali assistant surface oxidation technique. Thus nanotube arrays of Cu(OH)₂ were directly fabricated on the surface of copper foil by immersing in an aqueous solution of NaOH and (NH₄)₂S₂O₈. The wettability of the surface was changed from surperhydrophilicity to superhydrophobicity by chemical modification with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS). The morphologies, microstructures, crystal structure, chemical compositions and states, and hydrophobicity of the films on the copper foil substrates were analyzed by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and water contact angle measurement. It was found that the rough structure of the surface helped to magnify the wettability. The static contact angle (CA) for water is larger than 160° and the contact angle hysteresis (CAH) is lower than 5° on the modified surface. The high roughness of the nanotube arrays along with the generated C-F chains by chemical modification contributed to the improved superhydrophobicity. The present research is expected to be significant in providing a new strategy for the preparation of novel multifunctional materials with potential industrial applications on copper substrates.     

Synthesis and characterization of the Pd/InVO4-TiO2 co-doped thin films with visible light photocatalytic activities

Novel Pd/InVO₄-TiO₂ thin films with visible light photocatalytic activity were synthesized from the Pd and InVO₂ co-doped TiO₂ sol via sol-gel method. The photocatalytic activities of Pd/InVO₄-TiO₂ thin films were investigated based on the oxidative decomposition of methyl orange in aqueous solution. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy (UV-vis). The results indicate that the Pd/InVO₄-TiO₂ thin films are compact, uniform and consist of sphere nanoparticles with diameters about 80-100 nm. The UV-vis spectra show that the Pd/InVO₄-TiO₂ thin films extend the light absorption spectrum toward the visible region. XPS results reveal that doped Pd exist in the form of metallic palladium. The photocatalytic experiments demonstrate that Pd doping can effectively enhance the photocatalytic activities of InVO₄-TiO₂ thin films in decomposition of aqueous methyl orange under visible light irradiation. It has been confirmed that Pd/InVO₄-TiO₂ thin films could be excited by visible light (E < 3.2 eV) due to the existence of the Pd and InVO₄ doped in the films.     

Direct synthesis and characterization of highly ordered functional mesoporous silica thin films with high amino-groups content

A series of continuous, crack-free, highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of cationic CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻ (CTAB), nonionic C₁₆H₃₃(OCH₂CH₂)₁₀OH (Brij-56) or triblock copolymer H(OCH₂CH₂)₂₀(OCH(CH₃)CH₂)₇₀(OCH₂CH₂)₂₀)OH (P123) surfactant species under acidic conditions by sol-gel dip-coating. The molar ration of APTES/(TEOS + APTES) in the starting sol attains a value of 0.4. The effect of the sol aging on the mesostructure of thin films is systematically studied, and the optimal sol aging time is obtained for different surfactant systems. The amino-functionalized mesoporous silica thin films exhibit long-range ordering of 2D hexagonal (p6mm) and 3D cubic (Fm3m) pore arrays of size range from 2.2 to 8.3 nm following surfactants extraction as demonstrated by XRD, TEM and physical adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for thin films prepared using different surfactants is calculated to be 3.2 and above amino-groups per nm², which is very useful and promising for incorporating inorganic ions and biomolecules into these mesoporous silica materials.     

A comparative study of structural, compositional, thermal and optical properties of non stoichiometric (Zn,Fe)S chalcogenide pellets and thin films

Non-stiochiometric ternary chalcogenides Zn_1−xFe_xS, were prepared in the bulk form by co-precipitation of ZnS and FeS by Na₂S from aqueous solution containing FeSO₄ and ZnSO₄ and sintering of pellets of the co-precipitate repeatedly at 1073K in vacuum sealed quartz ampoules. Concomitant with the bulk form; thin fims of (Zn,Fe)S were synthesized by pyrolytic spray deposition method on quartz substrates from aqueous precursor solution containing ZnCl₂, FeCl₂ and thiourea in varying concentration under optimized conditions of substrate temperature (653K) carrier gas flowrate (11 l min⁻¹) and solution flow rate (8-6 ml min⁻¹).The structure, chemical composition, optical and thermoelectrical properties of the (bulk) pellets and thin films are studied as a function of initial solution concentration.X-ray diffraction of the pellets and thin films indicated the presence of solid solutions Zn_1−xFe_xS (sphalerite), while surface morphology as determined by SEM revealed a granular structure. Electrical resistivity of pellets and thin films, measured using two probe method (for pellets) and four probe van der Pauw method (for thin films) indicated that they are semiconducting while resistivity studies could not be carried out for a few thin films due to their high resistance (>20 MΩ).The chemical composition of the resulting solids as analyzed by X-ray fluorescence and that of thin films as analyzed by energy dispersive X-ray, reflected the composition of the solutions from which precipitation (for pellets) and deposition (for thin films) was carried out, with Fe contents up to x=0.4.SEM micrograph of pellets and thin films reveal that later have smaller grain size.Thermoelectric studies revealed that both solids and thin films possess the ability of ‘n’ as well as ‘p’ type conductivity.The diffuse optical reflectance measurements of pellets and transmittance measurements for thin films; as a function of wavelength reveal the dependence of direct optical band-gap on Fe content.     

H2O2水热合成双峰介孔硅MCM-48球

在温和的条件下,通过H₂O₂水热处理预合成的MCM-48,得到了有序的双峰介孔硅MCM-48球． 结果表明H₂O₂对于同时去除有机模板剂及形成双峰介孔硅MCM-48球具有重要的作用．采用XRD、TEM、FT-IR和N₂吸附-解吸等方法对双峰介孔MCM-48材料进行了表征,对双峰介孔MCM-48的形成机理也进行了探讨．