An investigation of super-hydrophilic properties of TiO2/SnO2 nano composite thin films

A sol-gel dip coating technique was used to fabricate TiO₂/SnO₂ nano composite thin films on soda-lime glass. The solutions of SnO₂ and TiO₂ were mixed with different molar ratios of SnO₂:TiO₂ as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO₂ concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO₂, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity.     

Preparation and characterization of transparent semiconductor RuO2-SiO2 films synthesized by sol-gel route

RuO₂-SiO₂ thin films with different Si/Ru molar ratios were prepared by the sol-gel method, using the hydrate ruthenium (III) chloride (RuCl₃·3.5H₂O) and tetraethylorthosilicate as precursors. The crystal structure, resistivity, chemical bonding configuration, transmittance, carrier concentration, and mobility of the RuO₂-SiO₂ films were investigated before and after annealing in N₂ ambient at 400-700 °C. The resistivity of the RuO₂-SiO₂ films with different Si/Ru molar ratios decreased abruptly after annealing at 400-700 °C. On the other hand, RuO₂ phase precipitated in the RuO₂-SiO₂ films with different Si/Ru molar ratios after annealing. Fourier transform infrared spectroscopy spectra indicated that the water absorption occurs for as-deposited RuO₂-SiO₂ films with different Si/Ru molar ratios. The transmittance of all RuO₂-SiO₂ films presented transmittance maximums after annealing at 700 °C. The carrier concentration and mobility of RuO₂-SiO₂ films are related to the Si/Ru molar ratios and the annealing temperature. This study discusses the connection among the material properties of the RuO₂-SiO₂ films and how they are influenced by the Si/Ru molar ratios and the annealing temperatures of RuO₂-SiO₂ films.     

SiO2/TiO2 multilayer films grown on cotton fibers surface at low temperature by a novel two-step process

A novel two-step process was developed to synthesize and deposit SiO₂/TiO₂ multilayer films onto the cotton fibers. In the first step, SiO₂ particles on cotton fiber surface were synthesized via tetraethoxysilane hydrolysis in the presence of cotton fibers, in order to protect the fibers against photo-catalytic decomposition by TiO₂ nanoparticles. In the second step, the growth of TiO₂ nanoparticles into the modified cotton fiber surface was carried out via a sol-gel method at the temperature as low as 100 °C. The as-obtained SiO₂/TiO₂ multilayer films coated on cotton fibers were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy and X-ray diffraction, respectively.     

Microwave dielectric properties of Li2TiO3 ceramics sintered at low temperatures

Li₂TiO₃ ceramics were prepared at the sintering temperatures from 1050 to 1250 °C. The optimal microwave dielectric properties were ?_r = 23.29, Q × f = 15,525 GHz (5.9 GHz), and τ_f = 35.05 ppm/ °C for the sample sintered at 1200 °C. The microwave dielectric properties were improved obviously when the Li₂TiO₃ ceramics were sintered at low temperatures with small additions of H₃BO₃ (B₂O₃ in the form of H₃BO₃). Only monoclinic Li₂TiO₃ was found in the pure or H₃BO₃-doped Li₂TiO₃ ceramics. About 1.0 wt.% H₃BO₃ addition aided the sintering of Li₂TiO₃ ceramics effectively while excessive H₃BO₃ (≥2.5 wt.%) was not favorable. Typically the best microwave dielectric properties were ?_r = 23.28, Q × f = 37,110 GHz (6.3 GHz), and τ_f = 30.43 ppm/ °C for the 1.0 wt.% H₃BO₃-doped Li₂TiO₃ ceramic sintered at 920 for 3 h, which is promising for LTCC applications.     

Low temperature facile synthesis of anatase TiO2 coated multiwalled carbon nanotube nanocomposites

Anatase TiO₂ coated multiwalled carbon nanotube (MWNT) nanocomposites were prepared by combining the sol-gel method with a self assembly technique at a low temperature. XRD, TEM, FTIR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the sample. The results showed that MWNTs were covered with a 12-20 nm thickness layer of anatase TiO₂ or surrounded by a 30 -290 nm thickness coating of anatase TiO₂. The layer or coating is constructed of TiO₂ nanoparticles about 5.8 nm. Furthermore, as-prepared composite was rich in surface hydroxyl groups.     

Formation of alkali resistant PDMS-TiO2-SiO2 hybrid coatings

PDMS-TiO₂-SiO₂ hybrid coatings have been prepared on glass substrates via sol-gel method. The structural evolution of the coatings containing different PDMS amounts was examined by TG-DTA and FTIR. It was found that the hybrid character of coatings can be reserved after heating at 200 °C. The alkali resistance of hybrid coatings in 1 N NaOH solution at 50 °C was investigated by X-ray fluorescence analysis, weight loss and scanning electron microscopy. The results showed that the coating could resist effectively the alkali attack for 24 h. Such alkali resistance depended on the added amount of PDMS and the coating with 20 wt.% PDMS showed a better alkali resistance.     

Photoactive and self-cleaning TiO2-SiO2 thin films on 316L stainless steel

In this study, TiO₂-SiO₂ nanocomposite films with different amounts of SiO₂ were prepared by sol-gel process and were coated onto stainless steel 316L. The effect of addition of various amount of SiO₂ in the precursor solution on the photocatalysis, photo-generated hydrophilicity and self-cleaning property of TiO₂ thin films was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, water contact angle measurements and UV spectroscopy. In the tested ranges of SiO₂ content and sintering temperature, the highest photocatalytic activity and self-cleaning property were observed in the 15 mol% SiO₂ sample sintered at 750 °C. Addition of less than 30 mol% SiO₂ had a suppressive effect on the transformation of anatase to rutile and on the crystal growth of anatase in the sintering heat treatment. Phase separation occurred in the composite films for SiO₂ content of 30 mol% or more.     

Phase transformation in semi-transparent TiO2 films irradiated with CO2 laser

Anatase (TiO₂) thin films were obtained by immersion of glass plates into a titanium sol-gel precursor followed by calcination at 450 °C for 3 h. The Raman results for the CO₂ laser irradiated TiO₂ films show that laser radiation is able to promote favorable changes of anatase phase in anatase/rutile mixtures. Nevertheless, the transformation process level depends on laser characteristics and scan speed of the radiation treatment.     

Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared by sol-gel method

We have studied the structural and optical properties of thin films of TiO₂, doped with 5% ZrO₂ and deposited on glass substrate (by the sol-gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450 °C) and for various layer thicknesses (63-286 nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62-2.29 and the porosity is in the range of 0.21-0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO₂, doped with 5% ZrO₂, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm grains). However, the undoped TiO₂ exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58-20.56 nm).     

Synthesis and characterization of beta barium borate thin films obtained from the BaO-B2O3-TiO2 ternary system

This work reports on the synthesis and the structural and optical characterization of beta barium borate (β-BBO) thin films containing 4, 8 and 16 mol% of titanium oxide (TiO₂) deposited on fused silica and silicon (0 0 1) substrates using the polymeric precursor method. The thin films were characterized by X-ray diffraction, Raman spectroscopy, atomic force microscopy and scanning electron microscopy techniques. The optical transmission spectra of the thin films were measured over a wavelength range of 800-200 nm. A decrease was observed in the band gap energy as the TiO₂ content was raised to 16 mol%. Only the β-BBO phase with a preferential orientation in the (0 0 l) direction was obtained in the sample containing 4 mol% of TiO₂ and crystallized at 650 °C for 2 h.     

Effect of copper-oxide segregation on the dielectric properties of CaCu3Ti4O12 thin films fabricated by pulsed-laser deposition

We investigated the effects of post-deposition cooling conditions on the surface morphologies and dielectric properties of CaCu₃Ti₄O₁₂ (CCTO) thin films grown by pulsed-laser deposition on Pt/TiO₂/SiO₂/Si substrates. CCTO thin films cooled under the typical cooling parameters, i.e., slow cooling (3 °C/min) at high oxygen pressure (66 kPa) showed a severe segregation of nanoparticles near the grain boundaries, which was identified to be copper oxide from electron probe micro analyzer mapping. On the other hand, we could not observe any segregation on the film surface when the samples were cooled fast (∼ 20 °C/min) at relatively low oxygen pressure (100 Pa). The dielectric constant, ε_r, of CCTO thin films deposited at 750 °C with severe surface segregation (ε_r ∼ 750 at 10 kHz) was found to be much lower than that (ε_r ∼ 2000 at 10 kHz) of CCTO thin films with smooth surface. As the copper-oxide segregation becomes more serious, which preferentially occurs at relatively high ambient oxygen pressure and temperature, the degradation in the dielectric properties of CCTO films becomes larger. The variation of dielectric constant of CCTO films with no copper-oxide segregation could be related to the presence of an impurity phase at grain boundaries.     

Nanocrystalline anatase TiO2 prepared via a facile low temperature route

Nanocrystalline anatase TiO₂ was prepared by a facile sol-gel route at a temperature of 65 °C under mild conditions. Tetrabutyl titanate was used as a titanium precursor, glacial acetic acid was used as an inhibitor, and anhydrous ethanol was used as a solvent. XRD, TEM, FT-IR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the nanoanatase TiO₂. The results showed that as prepared ellipse-shaped anatase TiO₂ with an average diameter of 7 nm, which is rich in surface hydroxyl groups, was found to exhibit high dispersibility.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.     

The gas sensitivity of nano TiO2-SnO2 film doped with Cd(II) ion

The nanocomposite oxide (0.2TiO₂-0.8SnO₂) doped with Cd²⁺ powder have been prepared and characterized by XRD and their gas-sensing sensitivity were characterized using gas sensing measurement. Experimental results show that, bicomponent nano anatase TiO₂ and rutile SnO₂ particulate thick film doped with Cd²⁺ behaves with good sensitivity to formaldehyde gas of 200 ppm in the air, and the optimum sensing temperature was reduced from 360 °C to 320 °C compared with the undoped Cd²⁺ thick film. The gas sensing thick films doped with Cd²⁺ also show good selectivity to formaldehyde among benzene, toluene, xylene and ammonia as disturbed gas and could be effectively used as an indoor formaldehyde sensor.     

Optical properties of TiO2 thin films after Ag ion implantation

Metal plasma ion implantation has being successfully developed for improving the electronic and optical properties of semiconductor materials. Prior to deposition, a TiO₂ colloidal suspension was synthesized by microwave-induced thermal hydrolysis of the titanium tetrachloride aqueous solution. The TiO₂ thin film was optimized to obtain a high-purity crystalline anatase phase by calcinations at 550 °C. The TiO₂ coating was uniform without aggregation, which provided good photo conversion efficiency. Ag ion implantation into the as-calcined TiO₂ thin films was conducted with 1 × 10¹⁵ ~ 1 × 10¹⁶ ions/cm² at 40 keV. The peak position and intensity of the photoluminescence and UV-Vis absorption spectra are quite sensitive to Ag doping. The optical characterization showed a shift in optical absorption wavelength towards infrared ray side, which was correlated with the structure variation of the Ag⁺ implanted TiO₂. Due to the strong capability of forming compounds between the energetic silver ions and TiO₂, the photoluminescence emission and UV-Vis absorption efficiencies were improved.     

Nanocrystalline chemically modified CdIn2O4 thick films for H2S gas sensor

CdIn₂O₄ sensor with high sensitivity and excellent selectivity for H₂S gas was synthesized by using sol-gel technique. Structural, electrical and gas sensing properties of doped and undoped CdIn₂O₄ thick films were studied. XRD revealed the single-phase polycrystalline nature of the synthesized CdIn₂O₄ nanomaterials. Since the resistance change of a sensing material is the measure of its response, selectivity and sensitivity was found to be enhanced by doping different concentrations of cobalt in CdIn₂O₄ thick films. The sensor exhibits high response and selectivity toward H₂S for 10 wt.% Co doped CdIn₂O₄ thick films. The current-voltage characteristics of 10 wt.% Co doped CdIn₂O₄ calcined at 650 °C shows one order increase in current with change in the bias voltage at an operating temperature of 200 °C for 1000 ppm H₂S gas.     

Solar photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using TiO2/SiO2 aerogel composite photocatalysts

Silica aerogels and TiO₂/silica aerogel composite photocatalysts were synthesized by sol–gel technique at ambient pressure using orthosilioate and tetra-n-butyl titanate as precursors, respectively. The prepared composite photocatalysts were characterized by XRD, TEM, BET surface area, FT-IR and UV–vis absorption spectra. The results showed that the TiO₂/silica aerogel composite photocatalysts possess high surface area. The addition of silica aerogels inhibited the grain growth and phase transformation of anatase to rutile during calcination. The TiO₂/silica aerogel composite sample calcined at 500 °C with an optimal silica aerogel content of 7 wt.% afforded the highest photocatalytic activity. The photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) was investigated by using this novel TiO₂/silica aerogel composite photocatalyst under solar light irradiation. The effects of irradiation time, pH, catalyst concentration, temperature and initial DNBP concentration were examined as operational parameters. The optimal operational parameters were found as follows: pH as solution pH 4.82, 8 g L⁻¹ catalyst concentration, 20 °C, and 240 min irradiation time. The kinetics of DNBP degradation by TiO₂/silica aerogel composite fit well a pseudo-first-order kinetic model. The repeatability of photocatalytic activity was also tested. This study showed the feasible and potential use of TiO₂/silica aerogel composite photocatalysts in degradation of toxic organic contaminants.     

Structure and CO gas sensing properties of electrospun TiO2 nanofibers

Titanium dioxide (TiO₂) nanofibers were fabricated by electrospinning a hybrid solution, which is a mixture of the TiO₂ sol precursor, polymer, and solvent. The structure and gas sensing properties of TiO₂ nanofibers were investigated. By calcining at 600 °C, the polymeric components were decomposed and a multi-layered random network structure of TiO₂ nanofibers was obtained. Polycrystalline TiO₂ nanofibers consist of tetragonal anatase and rutile TiO₂ phases. The diameter ranged from 400 nm to 500 nm and the grain size was about 15 nm. The TiO₂ nanofibers-based sensor exhibited response to CO concentration as low as 1 ppm at 200 °C.     

Fast response detection of H2S by CuO-doped SnO2 films prepared by electrodeposition and oxidization at low temperature

Fast response detection of H₂S by CuO-doped SnO₂ films prepared was prepared by a simple two-step process: electrodeposition from aqueous solutions of SnCl₂ and CuCl₂, and oxidization at 600 °C. The phase constitution and morphology of the CuO-doped SnO₂ films were characterized by X-ray diffraction and scanning electron microscopy. In all cases, a polycrystalline porous film of SnO₂ was the product, with the CuO deposited on the individual SnO₂ particles. Two types of CuO-doped SnO₂ films with different microstructures were obtained via control of oxidation time: nanosized CuO dotted island doped SnO₂ and ultra-uniform, porous, and thin CuO film coated SnO₂. The sensor response of the CuO doped SnO₂ films to H₂S gas at 50–300 ppm was investigated within the temperature range of 25–125 °C. Both of the CuO-doped SnO₂ films show fast response and recovery properties. The response time of the ultra-uniform, porous, and thin CuO coated SnO₂ to H₂S gas at 50 ppm was 34 s at 100 °C, and its corresponding recovery time was about 1/3 of the response time.     

Microscale meshes of Ti3O5 nano- and microfibers prepared via annealing of C-doped TiO2 thin films

A new technique to produce microscale Ti₃O₅ nano- and microfiber meshes is proposed. When a 3 wt% carbon-doped TiO₂ film on Si(1 0 0) was annealed at 1000 °C in wet nitrogen (0.8%H₂O), the amorphous TiO₂ phase gave rise to crystalline phases of λ-Ti₃O₅ (75%) and rutile + trace of TiO_2−xC_x (25%). From Raman and FTIR Spectroscopy results, it was concluded that rutile is formed at the inner layer located at the interface between the mesh and the Si that was located away from the surface such that the meshes of nano- and microfibers are predominantly composed of Ti₃O₅ grown from the reaction of rutile with Si to form Ti₃O₅ and SiO₂. On the other hand, it was noteworthy that the microscale mesh of nano- and microfibers showed increased photoluminescence compared with amorphous TiO₂. The PL spectrum which had a broad band in the visible spectrum, fitted as three broad Gaussian distributions centered at 571.6 nm (∼2.2 eV), 623.0 nm (∼2.0 eV) and 661.9 nm (∼1.9 eV).