Immobilized Anatase/Rutile Mixed Phase Titanium Dioxide on Glass Beads Prepared via Dip Coating Technique.

In this work, anatase/rutile mixed phase titanium dioxide (TiO2) particles prepared via sonochemical combined with calcination process was immobilized on borosilicate glass beads via sol-gel dip coating technique utilizing titanium tetraisopropoxide (TTIP). The optical properties of mixed phase TiO2 was evaluated by diffuse reflectance UV-Vis spectrophotometer to confirm phase transformation of anatase to rutile phase at different calcination temperatures. Phase identification and structural properties of TiO2 particles were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Surface morphology of mixed phase TiO2 coated on glass beads with different coating precursor solution were monitored by scanning electron microscope. The chemical composition of coated beads was characterized by energy dispersive spectroscopy to affirm the presence of TiO2 on glass bead substrate.

Effects of Seeding Layer Annealing Temperature on Physical and Morphological Structure of Ga/F Co-Doped ZnO Nanostructures.

In this work, effects of annealing temperature of seeding layer on structural properties and morphologies of Ga/F co-doped ZnO nanostructures synthesized by hydrothermal process were investigated by varying the annealing temperature of seed layer as 300-500 °C. The ZnO seeding layers were deposited onto cleaned glass substrates by dip-coating technique using zinc acetate dehydrate (CH3COO)2Zn·2H2O as starting coating precursor. The Ga/F co-doped ZnO nanostructures were then grown on these seed layers by conventional hydrothermal process using Zn(NO3)2, NH4F, GaN3O9 and hexamethyltetramine as Zn, F and Ga sources, respectively. Effect of seed layer annealing temperature on morphologies, structural and Photoluminescence properties was investigated by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), and Photoluminescence spectra, respectively. Variation of annealing temperature of seed layers can significantly result to the difference in morphological, structure and shape of the as-synthesized nanostructure products. It is found that the increase in annealing temperature leads to alternation in their shape from vertically-aligned nanosheets to nanorods with their average size ranging from 50 to 200 nm. Furthermore, the luminescence could be ascribed to the different contributions of the defect emissions, such asthe increase in the oxygen vacancy (VO) emissionor the decrease of the Zinc vacancy (Vzn). However, it can be speculated from the photoluminescence that the incorporated Ga and F substitute into ZnO.

Effect of Metal (Mn, Co, Zn, Ni) Doping on Structural, Optical and Photocatalytic Properties of TiO2 Nanoparticles Prepared by Sonochemical Method.

Metal-doped TiO2 nanoparticles (Metal = Mn, Co, Zn, Ni) were synthesized by sonochemical method accompanying post calcination process using metallic nitrates of manganese, cobalt, zinc, nickel with various metal contents from 0-5 mol% and titanium isopropoxide as a starting precursors. Sodium hydroxide (NaOH) base was used as a precipitating agent. The influence of ultrasound operated at 750 W 20 kHz on the crystalline structure of metal-doped TiO2 nanoparticles has been characterized by X-ray diffraction (XRD) while morphologies and grain size of the nanoparticles were monitored by field emission scanning electron microscope (FE-SEM). The optical absorptivities and corresponding band gaps were evaluated by diffuse reflectance spectroscopy (DRS). The performance of photocatalytic activities of metal-doped TiO2 nanoparticles against aqueous organic dye Rhodamine B (RhB) under visible light was investigated. The results reveal that their crystallinity of synthesized metal doped TiO2 nanoparticles is in mixed phase between anatase, rutile and brookite with calcination temperature at 500 °C for 3 h and their crystalline of all samples are shown. The incorporation of metal dopant on the photocatalytic performance of TiO2 exhibits a significant enhancement in its photocatalytic activities under visible light due to the decrease in band gap energy of metal doped TiO2 nanoparticles.

Er-Doped BiVO4/BiFeO3 Nanocomposites Synthesized via Sonochemical Process and Their Piezo-Photocatalytic Application.

In this work, Er-doped BiVO4/BiFeO3 composites are prepared using the sonochemical process with a difference of rare earth loading compositions. The crystallinity and chemical and morphological structure of as-synthesized samples were investigated via X-ray diffraction, Raman scattering, and electron microscopy, respectively. The diffuse reflectance technique was used to extract the optical property and calculate the optical band gap of the composite sample. The piezo-photocatalytic performance was evaluated according to the decomposition of a Rhodamine B organic compound. The decomposition of the organic compound was achieved under ultrasonic bath irradiation combined with light exposure. The Er-doped BiVO4/BiFeO3 composite heterojunction material exhibited significant enhancement of the piezo-photocatalytic activity under both ultrasonic and light irradiation due to the improvement in charge generation and separation. The result indicates that Er dopant strongly affects the phase transformation, change in morphology, and alternation in optical band gap of the BiVO4 matrix. The incorporation of BiFeO3 in the composite form with BiVO4 doped with 1%Er can improve the photocatalytic performance of BiVO4 via piezo-induced charge separation and charge recombination retardment.

The Effect of Polyvinyl Alcohol Addition on the Optical Properties and Oxygen Detection Performance of Titanium Dioxide and Methylene Blue Nanocomposite Colorimetric Indicators.

In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO2/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO2 nanoparticles with MB and citric acid. PVA, at varying concentrations (0, 3, 9, and 14 wt%), was introduced during the wet milling process to produce a homogeneous composite film. Spin coating was employed to fabricate TiO2/MB nanocomposite films for oxygen detection evaluation. The influence of PVA loading on the films' chemical functionalities and surface morphologies was assessed using Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The indicator's activation process, involving a color change between bleached and colored states, and its recovery time were monitored via optical imaging and UV-VIS-NIR spectrophotometry. The results revealed that a PVA content of 9 wt% yielded well-defined films with enhanced stability of the TiO2/MB nanocomposite's oxygen detection performance.

Structural and Optical Characterizations of Polymethyl Methacrylate Films with the Incorporation of Ultrafine SiO2/TiO2 Composites Utilized as Self-Cleaning Surfaces.

The structural and optical characterizations of nanocomposite films of polymethyl methacrylate (PMMA) and SiO2/TiO2 composites prepared via the spin-coating technique were investigated using different SiO2:TiO2 ratios. The SiO2/TiO2 nanocomposites were synthesized using the sonochemical process with Si:Ti precursor ratios of 1:0.1, 1:0.5, 1:1, 1:2, 1:4, and 0:1. All characterizations of ultrafine SiO2/TiO2 particles were loaded at 1 wt.% in a PMMA matrix for the fabrication of transparent SiO2/TiO2/PMMA composite films. The phase structure and morphology of SiO2/TiO2/PMMA composite films were monitored using X-ray diffraction, optical microscopy, and field-emission scanning electron microscopy. A surface roughness analysis of SiO2/TiO2/PMMA nanocomposite films was conducted using atomic force microscopy. For optical characterization, transmission properties with different incident angles of SiO2/TiO2/PMMA composite films were analyzed with UV-vis spectrophotometry. The water contact angles of SiO2/TiO2/PMMA composite films were analyzed to identify hydrophilic properties on film surfaces. Photocatalytic reactions in SiO2TiO2 composite films under UV irradiation were evaluated using rhodamine B dye degradation. The optimal condition of SiO2/TiO2/PMMA nanocomposite films was obtained at a 1:1 SiO2:TiO2 ratio in self-cleaning applications, resulting from good particle dispersion and the presence of the TiO2 phase in the composite.

Tailoring the Emission Behavior of WO3 Thin Films by Eu3+ Ions for Light-Emitting Applications.

The article reports the successful fabrication of Eu3+-doped WO3 thin films via the radio-frequency magnetron sputtering (RFMS) technique. To our knowledge, this is the first study showing the tunable visible emission (blue to bluish red) from a WO3:Eu3+ thin film system using RFMS. X-ray diffractograms revealed that the crystalline nature of these thin films increased upto 3 wt% of the Eu3+ concentration. The diffraction peaks in the crystalline films are matched well with the monoclinic crystalline phase of WO3, but for all the films', micro-Raman spectra detected bands related to WO3 monoclinic phase. Vibrational and surface studies reveal the amorphous/semi-crystalline behavior of the 10 wt% Eu3+-doped sample. Valence state determination shows the trivalent state of Eu ions in doped films. In the 400-900 nm regions, the fabricated thin films show an average optical transparency of ~51-85%. Moreover, the band gap energy gradually reduces from 2.95 to 2.49 eV, with an enhancement of the Eu3+-doping content. The doped films, except the one at a higher doping concentration (10 wt%), show unique emissions of Eu3+ ions, besides the band edge emission of WO3. With an enhancement of the Eu3+ content, the concentration quenching process of the Eu3+ ions' emission intensities is visible. The variation in CIE chromaticity coordinates suggest that the overall emission color can be altered from blue to bluish red by changing the Eu3+ ion concentration.

Quasi-solid-state dye-sensitized solar cells based on TiO2/NiO core-shell nanocomposites.

The core-shell nanocomposites of titanium dioxide (TiO2) and nickel oxide (NiO) used as modified photoelectrode materials in a quasi-solid-state dye-sensitized solar cell (quasi-DSSC) were synthesized using TiO2 P-25 and a nickel acetate precursor, via ball milling. The as-obtained intermediate products were annealed at 350, 450, and 550 degrees C. The structural properties of the NiO/TiO2 nanocomposites were well characterized via X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The results imply that NiO-shell-coated TiO2 nanoparticles can be obtained with the assistance of sufficient thermal energy in the system. The crystallite size of the composite increased as the annealing temperature increased. Among all the prepared conditions, the composite with 0.1 wt% NiO exhibited the best performance, with an optimized solar-energy conversion efficiency of 2.29% and with a short-circuit current density of 7.21 mA/cm2. The significant enhancement of the device's current density may be associated with the charge recombination suppression by the NiO shell, which acted as a potential barrier in the composite. The decrease in the recombination of the photo-injected electrons, and the increase in the number of electrons tunneling through the NiO layer at the interface, may have resulted from the presence of a NiO layer on the TiO2 nanoparticles.

Microwave-assisted synthesis and characterization of zinc oxide/carbon nanotube composites.

A composite material of zinc oxide and carbon nanotubes were successfully synthesized via a sol process using zinc acetate dihydrate and treated multi-wall carbon nanotubes under microwave irradiation. The morphology, microstructure and chemical bonding of as-obtained composites were well characterized using X-ray diffraction, scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy. Zinc oxide nanoparticles were dispersively coated on the surface of carbon nanotube when the precursor was dried under microwave irradiation without post-annealing. X-ray diffraction results obviously showed the mixture of two phases of carbon nanotube and wurzite zinc oxide whose size is approximately 15 nm. The formation of zinc oxide nanoparticles on carbon nanotube surface in the composite prepared by microwave heating is much better than the composite heated by conventional annealing. Fourier transform infrared spectroscopic results suggest that carboxylic groups and uniform heating by microwave heating could play key roles on the nucleation of zinc oxide on carbon nanotube surface.

Sonochemical Synthesis, Characterization, and Photocatalytic Activity of Perovskite ZnTiO3 Nanopowders.

Perovskite zinc titanate (ZnTiO3) nanopowders were synthesized using the sonochemical method combined with calcinations at 500 °C and 900 °C for 2 h to improve their crystallinity. The effect of calcination temperature on their structural, optical, and photocatalytic properties has been studied. The cubic phase and the mixing phase of cubic and hexagonal were observed in sample calcined at 600 °C and 700 °C, respectively, while the spinel ZnTiO3 and rutile TiO2 phase arises in sample calcined over 700 °C. The valence state was investigated by the X-ray absorption near-edge spectroscopy technique, and the corresponding results indicate the existence of Zn2+ and Ti4+ in the powders. The chemical states of the samples were scrutinized by X-ray photoelectron spectroscopy. The average particle size is approximately 20-240 nm. The excellent photocatalytic performance of ZnTiO3 nanoparticle calcined at 700 °C gave complete degradation Rhodamine B (RhB) in 75 min under ultraviolet light exposure with the k rate of 0.033 min -1 and 55% of decolorization RhB in 210 min under visible irradiation. The sample calcined at 700 °C ensures a good dielectric permittivity with a value 20 and the loss tangent of about 10-2 .

Sb-Doped SnO2 Nanoparticles Synthesized by Sonochemical-Assisted Precipitation Process.

Sb-doped SnO2 nanopowders were synthesized by sonochemical-assisted precipitation process using stannic chloride pentahydrate (SnCl4.5H2O) and antimony chloride (SbC3) as starting precursors. Effect of sonication and Sb doping concentrations on physical structures and electrical properties of Sb-doped SnO2 nanoparticles were investigated by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, Raman spectroscopy and two-point probe method. The results indicated that the good dispersion with less agglomeration of particles in SnO2 phase can be obtained by single step sonochemical-assisted process. Moreover, XRD results indicated that the crystallinity of Sb-doped SnO2 nanopowders deteriorated with increasing Sb content, suggesting that Sb dopant significantly prevent SnO2 crystallite growth. The XPS spectra of Sb-doped SnO2 obviously confirmed the existence of Sb ion incorporated into SnO2 matrix. These results revealed that incorporation of Sb ions into SnO2 lattice with specific concentration has significant influence on formation and crystallization and can dramatically enhance the conductivity of tin oxide.