Tetragonal TiO2 Research Articles

Synthesis of titanium-vanadium oxide thin films through thermal oxidation process for their use in CO gas sensing application

The thermal oxidation of evaporated titanium-vanadium thin films was carried out at different post-annealing temperatures. The structural, morphological, compositional, optical, electrical, and gas sensing properties of titanium-vanadium oxide thin films were primarily investigated. The results of the XRD study and Raman spectroscopy verified the presence of the orthorhombic V2O5, tetragonal TiO2, and monoclinic V2Ti3O9 phases. The crystallinity of TVO thin films was improved at higher annealing temperatures. The grain size (seen from SEM images) and oxygen compositions (obtained from EDS measurement) of TVO samples are also enhanced when the post-annealing temperature is increased from 500 to 575 °C. From the transmittance curves, the bandgap values for TVO samples were estimated and found in the range of 2.14–2.36 eV. The n-type conductivity of TVO films was confirmed by the negative Hall coefficient values. At last, the CO gas sensing response of TVO thin films was analyzed by monitoring the change in the surface electrical resistances at different operating temperatures and CO gas concentrations. The dynamic and static resistances were assessed at different operating temperatures varying from 100 to 300 °C. The TVO sample prepared at 550 °C showed the best conditions by examining the materials and CO sensing properties.

Synthesis of Mesoporous Tetragonal ZrO2, TiO2 and Solid Solutions and Effect of Colloidal Silica on Porosity.

Metal oxides possessing a large surface area, pore volume and desirable pore size provide more varieties and active industrial potentials. Nevertheless, it is very challenging to produce crystal metal oxides while keeping satisfactory porosity features, especially for ternary compositions. High temperature is usually needed to produce crystal metal oxides, which readily leads to the collapse of the pore structure. Herein, by employing a 'soft' dispersant agent and a hard silica template, ZrO2, TiO2 and Zr-Ti solid solutions having a tetragonal crystal structure are produced and the silica-leached materials are characterized from macroscopic to atomistic scales. The micron-sized particulate powders are composed of nanoscale 'building blocks', with crystallite sizes between ~8 and 21 nm. These polycrystalline ceramic powders exhibit a high specific surface area (up to ~200 m2·g-1) and pore volume (up to 0.5 cm3·g-1), with a pore size range of ~5-20 nm. Importantly, the Zr/Ti-O-Si-OH chemical bonds exist on the particle surface, with about two-thirds of the surface covered by silica. The hydroxyl groups can further post-graft organic ligands or directly associate with species. Synthesized mesoporous metal oxides are highly homogenous and could potentially be used in various applications because of their tetragonal structure and porosity features.

650 ps SET speed in Ge2Sb2Te5 phase change memory induced by TiO2 dielectric crystal plane

AbstractCrystallization speed of phase change material is one of the main obstacles for the application of phase change memory (PCM) as storage class memory in computing systems, which requires the combination of nonvolatility with ultra‐fast operation speed in nanoseconds. Here, we propose a novel approach to speed up crystallization process of the only commercial phase change chalcogenide Ge2Sb2Te5 (GST). By employing TiO2 as the dielectric layer in phase change device, operation speed of 650 ps has been achieved, which is the fastest among existing representative PCM, and is comparable to the programing speed of commercial dynamic random access memory (DRAM). Because of its octahedral atomic configuration, TiO2 can provide nucleation interfaces for GST, thus facilitating the crystal growth at the determinate interface area. Ti–O–Ti–O four‐fold rings on the (110) plane of tetragonal TiO2 is critical for the fast‐atomic rearrangement in the amorphous matrix of GST that enables ultra‐fast operation speed. The significant improvement of operation speed in PCM through incorporating standard dielectric material TiO2 in DRAM paves the way for the application of phase change memory in high performance cache‐type data storage.image

Mycofabrication of bimetal oxide nanoparticles (CuO/TiO2) using the endophytic fungus Trichoderma virens: Material properties and microbiocidal effects against bacterial pathogens

Bimetallic oxide nanoparticles (NPs) have gained the interest of researchers owing to the synergistic mechanism of action by the elements present. Mycosynthesis of nanostructures is a promising, facile, and an environmentally friendly approach. In the present study, CuO/TiO2 NPs were produced using the cell-free filtrate of the endophytic fungus Trichoderma virens. The reaction of the fungal filtrate with the two metal salts, CuSO4.5H2O and TiO2, resulted in the mycosynthesis of the CuO/TiO2 NPs. The prepared bimetal oxide NPs were characterized using XRD, FTIR spectroscopy, EDX, DLS, zeta potential analysis, XPS, Raman scattering, FESEM, and HRTEM. The mycosynthesized CuO/TiO2 NPs exhibited diffraction peaks characteristic of the monoclinic CuO and tetragonal rutile TiO2 crystal planes. Homogeneity and stability were observed as a result of the biological moieties present in the fungal filtrate, which capped the CuO/TiO2 NPs. The prepared CuO/TiO2 NPs were distributed as flake/plate-like and quasi-spherical/nanorod CuO and TiO2 NPs, respectively. A broad-spectrum antibacterial effect was recorded, with zones of inhibition as follows: foodborne pathogens Escherichia coli (14.34 mm), Salmonella enterica serovar Typhimurium (11.32 mm), and Staphylococcus aureus (9.63 mm); and phytopathogenic bacteria involving Clavibacter michiganensis subsp. michiganensis (Cmm, 12.16 mm), C. michiganensis subsp. capsici (Cmc, 11.26 mm), wild type and streptomycin-resistant Pectobacterium carotovorum subsp. carotovorum (Pcc, 11.06 and 12.37 mm, respectively), and wild type and streptomycin-resistant Xanthomonas citri pv citri (Xcc, 12.48 and 12.69 mm, respectively). The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the CuO/TiO2 NPs were determined using the broth microdilution assay. NP-treated bacterial cells at sub-MICs had rough surfaces with membrane defects and exhibited shrinkage, reduction of cell edges, cracks, and fractures on their surfaces. This study provides insights into the potential of the mycosynthesized CuO/TiO2 NPs as alternative nano-antimicrobial agents, which could be employed for future biomedical, agricultural, and pharmaceutical applications.

A Study of Green Synthesis of Nano-TiO2 Catalyst by Gossypium Leaf Extract and Its Nanocatalysis in the Synthesis of Biofuel from Gossypium Seed Oil

Synthesis of TiO2 nanoparticles by aqueous leaf extract of Gossypium (Gossypiumarboretum) leaves on meta titanic acid [TiO(OH)2]. Rutile tetragonal TiO2 nanoparticles were characterized by XRD, SEM and TEM studies and their particle size was calculated, which was below 100 nm. The Obtained TiO2NPs were used as catalysts in the transesterification of Gossypium seed oil, which enhanced the rate of reaction. Thus, it is a very attractive catalyst for biodiesel production from Gossypium seed oil. The effect of the amount of nano-TiO2 catalyst and microwave heating was studied. In this study, the preparation of both catalyst and biodiesel from the parts of the same Gossypium plant and the feasibility of carrying out the microwave-assisted transesterification (green process) of Gossypium seed oil by using biogenic nanoTiO2 catalyst was explored. They improve the efficiency of transesterification. The used catalyst can be recycled by simple filtration and reused without reduction in its activity. It is a green method (affords nontoxic and noncorrosive medium), clean reaction, simple experimental, isolation procedures, gives high yield and the properties of synthesized biodiesel are in good agreement with that of diesel oil. So, it may be used alone or by blending with diesel.

Environmentally Friendly New Catalyst Using Waste Alkaline Solution from Aluminum Production for the Synthesis of Biodiesel in Aqueous Medium.

Red mud (RM) is composed of a waste alkaline solution (pH = 13.3) obtained from the production of alumina. It contains high concentrations of hematite (Fe2O3), goethite (FeOOH), gibbsite [Al(OH)3], a boehmite (AlOOH), anatase (Tetragonal-TiO2), rutile (Ditetragonal dipyramidal-TiO2), hydrogarnets [Ca3Al2(SiO4)3-x(OH)4x], quartz (SiO2), and perovskite (CaTiO3). It was shown to be an excellent catalytic mixture for biodiesel production. To demonstrate the value of RM, an environmentally friendly process of transesterification in aqueous medium using waste cooking oil (WCO), MeOH, and waste alkaline solution (WAS) obtained from aluminum production was proposed. Triglycerides of WCO reacted with MeOH at 60 °C to yield mixtures of fatty acid methyl esters (FAMEs) in the presence of 0.019% (w/w) WAS/WCO using the WAS (0.204 mol L-1, predetermined by potentiometric titration) from aluminum production by the Bayer process. The use of the new catalyst (WAS) resulted in a high yield of the products (greater than 99% yield).

Electrochemical Lithium Insertion into TiO2 Anatase ALD Thin Films for Li‐Ion Microbatteries: An Atomic‐Scale Picture Provided by Raman Spectroscopy

AbstractElectrochemical lithium (de)intercalation in an atomic layer deposited (ALD) TiO2 anatase thin film deposited on a planar Si /Al2O3/Pt substrate is investigated by Raman spectroscopy. An initial discharge capacity of 63 µAh cm−2 µm−1 (0.5 Li+ mole−1) is reached at C/10 rate, which increases up to 77 µAh cm−2 µm−1 upon further cycles. An excellent capacity retention is achieved over at least 100 cycles, showing the good adherence of the ALD thin film. Raman spectra of LixTiO2 (0 ≤ x ≤ 0.5) thin film electrodes point to the nucleation of the orthorhombic lithiated titanate (LT) Li0.5TiO2 phase from x = 0.1. This LT phase coexists with tetragonal TiO2 in the 0.1 ≤ x ≤ 0.4 composition domain to be pure for x = 0.5. A fully reversible transformation from orthorhombic LT to tetragonal TiO2 is observed upon the charge. The high quality of the Raman spectra allows identifying for the first time 12 modes in the 100–800 cm−1 region for the electrochemically formed LT phase. Furthermore, an appropriate Raman spectra analysis allows a reliable and quantitative determination of the thin film composition during discharge and charge. These results illustrate Raman spectroscopy is a powerful probe to scrutinize the Li insertion/extraction mechanism in TiO2 thin films.

Characterization and Biological Studies of Synthesized Titanium Dioxide Nanoparticles from Leaf Extract of Juniperus phoenicea (L.) Growing in Taif Region, Saudi Arabia

Green synthesis of metal nanoparticles in nanosized form has acquired great interest in the area of nanomedicine as an environmentally friendly and cost-effective alternative compared to other chemical and physical methods. This study deals with the eco-friendly green synthesis of titanium dioxide nanoparticles (TiO2 NPs) utilizing Juniperus phoenicea leaf extract and their characterization. The biosynthesis of TiO2 NPs was completed in 3 h and confirmed by UV-Vis spectroscopy, a strong band at 205.4 nm distinctly revealed the formation of NPs. Transmissions electron microscopy (TEM) analysis showed the synthesized TiO2 NPs are spherical in shape, with a diameter in a range of 10–30 nm. The XRD major peak at 27.1° congruent with the (110) lattice plane of tetragonal rutile TiO2 phase. Dynamic light scattering (DLS) analysis revealed synthesized TiO2 NPs average particle size (hydrodynamic diameter) of (74.8 ± 0.649) nm. Fourier transmission infrared (FTIR) revealed the bioactive components present in the leaf extract, which act as reducing and capping agents. The antimicrobial efficacy of synthesized TiO2NPs against, Staphylococcus aureus, and Bacillus subtilis (Gram-positive), Escherichia coli and Klebsiella pneumoniae (Gram-negative), Yeast strain (Saccharomyces cerevisiae) and fungi (Aspergillus niger, and Penicillium digitatum) assayed by a disc diffusion method. TiO2NPs inhibited all tested strains by mean inhibition zone (MIZ), which ranged from the lowest 15.7 ± 0.45 mm against K. pneumoniae to the highest 30.3 ± 0.25 against Aspergillus niger. The lowest minimum inhibitory concentration (MIC) and bactericidal (MBC) values were 20 μL/mL and 40 μL/mL of TiO2NPs were observed against Asp. niger. Moreover, it showed significant inhibitory activity against human ovarian adenocarcinoma cells with IC50 = 50.13 ± 1.65 µg/mL. The findings concluded that biosynthesized TiO2 NPs using Juniperus phoenicea leaf extract can be used in medicine as curative agents according to their in vitro antibacterial, antifungal, and cytotoxic activities.

Flame synthesized tetragonal TiO2 nanoparticles for Methylene Blue and Congo Red dye removal applications

Commercially affordable titanium dioxide nanoparticles (TiO2 NPs) catalyst with low toxicity and high efficiency, were prepared by scalable Flame pyrolysis method. For this, titanium iso-propoxide solution was directly burned in air, the product in the form of white soot was collected over water cooled conical flask. The prepared nanoparticles were characterized by various sophisticated techniques viz. UV–Visible, FTIR, XRD, SEM, EDS and TEM. The SEM, TEM and Zeta Potential Analyzer illustrated spherical morphology of the synthesized TiO2 NPs with an average size of about 150 nm. The XRD confirmed formation of prominently dominated anatase phase co-existed with traces of rutile phase. The combination of anatase and rutile phase exhibited increased catalytic activity for removal of dyes. The flame synthesized TiO2 nanoparticles exhibited strong dye removal efficiency of 97.64 % for Methylene Blue and 92.39 % for Congo Red dyes respectively, making it vitally important for the waste water treatment and industrial dyes removal applications. Probable dye degradations mechanism on the surface of TiO2 NPs also proposed based on the LCMS results.

Surface-Engineered TiO2 for High-Performance Flexible Supercapacitor Applications

Titanium dioxide (TiO2) shows excellent pseudocapacitive properties. However, the low internal conductivity of TiO2 limits its use in supercapacitor applications. Therefore, an efficient surface engineering process was developed to enhance the overall pseudocapacitive performance of rutile TiO2 nanorods. Specifically, surface-engineered TiO2 nanorod arrays coordinated on carbon cloth were established through the Kapton tape-assisted hydrothermal route. X-ray diffraction analysis confirmed the formation of a tetragonal TiO2 rutile phase. Morphological analysis revealed the formation of uniform nanorods with an apparent high surface-to-volume aspect ratio. X-ray photoelectron spectroscopy analysis showed that the TiO2 synthesized in the presence of Kapton tape and annealed under air had high content of hydroxyl groups and Ti3+, which is favorable for supercapacitor performance. Surface treatment of the samples led to significantly enhanced conductivity and electrochemical behavior of TiO2. The surface-engineered TiO2 nanorod arrays show specific capacitance of about 57.62 mF/cm2 at 10 mV/s in 2 M KOH, with excellent rate capability of about 83% at 200 mV/s, and also exhibit long cycle life, retaining 91% of their original capacitance after 10,000 charge/discharge cycles, which is among the highest values reported for TiO2-based supercapacitors.Graphical

Synthesis and Characterization of BaTiO3/TiO2 Heterojunction Photocatalyst for Novel Application in Photocatalytic Degradation of TBBPA under Simulated Sunlight Irradiation

AbstractThe polyacrylamide gel method combined with low temperature sintering technology (PGMCLTST) have been used to synthesize the BaTiO3/TiO2 heterojunction photocatalysts. The BaTiO3/TiO2 heterojunction photocatalyst only contains tetragonal BaTiO3, rutile TiO2 and anatase TiO2, without any other impurities. Based on a variety of characterization, it was confirmed that a special heterojunction was formed between BaTiO3 and TiO2, and there were a large number of interface defects or oxygen defects in the samples. The BaTiO3/10 wt % TiO2 heterojunction photocatalysts have high photocatalytic activity for the degradation of tetrabromobisphenol A (TBBPA) under simulated sunlight irradiation. The interfacial defects enhance the transfer and separation efficiency of charge carriers in BaTiO3/TiO2 heterojunction photocatalysts. This technique provides a new idea for the application of BaTiO3/TiO2 heterojunction photocatalysts and other heterojunction photocatalysts in the degradation of persistent organic pollutants (POPs).

Visible-light-induced V2O5 -TiO2 photocatalysts with high photocatalytic ability for degradation of tetracycline

In this contribution, mesoporous V2O5–TiO2 heterojunctions were constructed utilizing a soft-chemistry approach. The photocatalytic ability of the V2O5–TiO2 nanocomposites was assessed for tetracycline degradation under visible exposure compared to bare TiO2 and P-25. TEM images presented the close contact between the tetragonal TiO2 in the anatase phase and orthorhombic V2O5 with particle sizes between 10 and 20 nm. The obtained V2O5–TiO2 photocatalysts indicated higher photocatalytic performance compared to bare TiO2 and P-25 in the photooxidation of tetracycline. It demonstrated that 3%V2O5–TiO2 nanocomposite exhibited a superb photocatalytic ability in the destruction of tetracycline ∼100% after 120 min, owing to its promoted visible harvest ability, large surface area and enhanced separation efficiency of carriers. Meanwhile, the kinetic rate constant of 3%V2O5–TiO2 nanocomposite was about 9.8 and 29.3 times larger than bare TiO2 and P-25. The photocurrent responses and PL spectra measurements are matched well with the photocatalytic efficiency of the V2O5–TiO2 nanocomposites. The reasonably designed heterojunctions V2O5–TiO2 nanocomposites could enhance the photocatalytic performance by reducing the recombination rate of photoinduced carriers.

Enhancement of visible-light photo-activity of TiO2 arrays for environmental water purification

PurposeOver the past decades, intense efforts have been devoted to design and synthesize efficient photocatalysts which are active under sunlight for environmental and energy applications. Titanium dioxide (TiO2) has attracted much attention over many years for organic contaminant degradation in air or water due to its strong optical absorptivity, chemical stability and low cost. However, TiO2 has a very low photo quantum yield which prompts the easy recombination of photogeneration electron/hole pairs. In addition, bandgap of 3.2 eV restrains application of this photocatalyst mainly to the UV range.Design/methodology/approachVertically oriented one-dimensional TiO2 nanostructures remarkably improve electron transport by creating a direct conduction pathway, decreasing intercrystalline contacts and stretching grown structure with the specified directionality. In this research, to enhance the visible light absorbance of TiO2, prearranged hydrogenated titanium dioxide nanorods (H-TNRs) in the presence of H2/N2 gas flow are hydrothermally synthesized.FindingsThe X-ray diffraction patterns illustrated the characteristic peaks of tetragonal rutile TiO2 and confirmed that there is no phase change after hydrogenation. Trivalent titanium ions surface defects and oxygen vacancies were considered as major reasons for redshift of absorption edge toward visible region and subsequently narrowing the bandgap to 2.27 eV. The optimized photocatalysts exhibited high visible-light-driven photocatalytic activity for degradation of methylene blue in water within 210. The synthesized H-TNRs established themselves as promising photocatalysts for organic compounds degradation in the aqueous solution.Originality/valueTo the best of the authors’ knowledge, this work is original and has not been published elsewhere nor is it currently under consideration for publication elsewhere.

Effects of additional oxygen on the structural, mechanical, thermal, and corrosive properties of TiN coatings

In this study, the influence of additional oxygen on the structural, mechanical, thermal, and corrosive properties of TiN coatings was investigated. A progressive change occurred in the structure from cubic TiN, Ti0.50O0.11N0.39, Ti0.46O0.15N0.39, and Ti0.44O0.28N0.28 to mixed cubic and monoclinic Ti0.39O0.40N0.21, and finally to tetragonal TiO2. Doping oxygen into TiN led to a significant change in hardness owing to the solid solution strengthening effect and the formation of ionic bonds and oxide phases. Ti0.46O0.15N0.39 exhibited the highest hardness of ∼28.8 GPa. The addition of oxygen weakened the thermal stability of the TiN coating owing to the production of more oxides during annealing. After oxidation at 600 °C for 10 h, the Ti0.50O0.11N0.39 coating with an oxide thickness of ∼0.86 μm exhibited an excellent oxidation resistance. The TiO2 coating was not oxidized, thereby maintaining the initial morphology. In addition, the corrosion resistances of the TiON coatings were closely related to the oxygen content, where the low oxygen content compound Ti0.50O0.11N0.39 exhibited the best corrosion resistance.

Multifunctional Core-Shell NiFe2O4 Shield with TiO2/rGO Nanostructures for Biomedical and Environmental Applications.

Multifunctional core@shell nanoparticles have been synthesized in this paper through 3 stages: NiFe2O4 nanoparticles by microwave irradiation using Pedalium murex leaf extract as a fuel, core@shell NiFe2O4@TiO2 nanoparticles by sol-gel, and NiFe2O4@TiO2@rGO by sol-gel using preprepared reduced graphene oxide obtained by modified Hummer's method. XRD analysis confirmed the presence of both cubic NiFe2O4 spinel and tetragonal TiO2 rutile phases, while Raman spectroscopy analysis displays both D and G bands (ID/IG = 1.04) associated with rGO. Morphological observations by HRTEM reveal a core-shell nanostructure formed by NiFe2O4 core as confirmed by SAED with subsequent thin layers of TiO2 and rGO. Magnetic measurements show a ferromagnetic behavior, where the saturation magnetization drops drastically from 45 emu/g for NiFe2O4 to 15 emu/g after TiO2 and rGO nonmagnetic bilayers coating. The as-fabricated multifunctional core@shell nanostructures demonstrate tunable self-heating characteristics: rise of temperature and specific absorption rate in the range of ΔT = 3–10°C and SAR = 3–58 W/g, respectively. This effectiveness is much close to the threshold temperature of hyperthermia (45°C), and the zones of inhibition show the better effective antibacterial activity of NTG against various Gram-positive and Gram-negative bacterial strains besides simultaneous good efficient, stable, and removable sonophotocatalyst toward the TC degradation.

Ball Milling synthesis and characterization of highly crystalline TiO[formula omitted]-ZnO hybrids for photovoltaic applications

In this work, Ball Milling is investigated as a viable synthesis method for highly crystalline TiO2-ZnO composites. The composites were verified using various standard techniques. XRD measurements confirmed the presence of hexagonal wurtzite ZnO and tetragonal TiO2 nano particles. Both XRD and transmission electron microscopy show a mean crystallite size between 12.7 and 15.0 nm. The blend compatibility of the two oxides was investigated by varying the molar ratio of ZnO from 0 to 30%. It is apparent that the morphology compatibility of ZnO and TiO2 plays a significant role in the performance of the final device. The composite specific surface area is seen to increase with ZnO doping. UV–Vis measurements show that its band gap decreases from 3.281 to 3.221 eV. UV–Vis further demonstrated a red-shift of TZHO absorption band which enhances the ability of hybrids to absorb in the visible wavelength range. Scanning electron microscopy suggests that TiO2 and ZnO are morphologically well-matched, and can be used as the electron transport layer in a blended perovskite solar cell. A maximum efficiency of 8% was measured on the PSC with 30% ZnO with Isc=18.4 mA, Voc=0.69 V, and FF=0.65. This efficiency is comparable for PSCs with the hybrid oxide synthesized using other methods, showing that Ball Milling is also a viable method.

Comparison of Eosin yellowish dye–sensitized and CdS-sensitized TiO2 nanomaterial–based solid-state solar cells

In the present work, Eosin yellowish (EY) dye–sensitized and CdS-sensitized TiO2 photoanodes prepared by doctor blade technique, for dye (DSSC)- and semiconductor-sensitized solar cell (SSSC) by engaging different forms of solid-state electrolyte. To begin with, the TiO2 and CdS/TiO2 nanomaterials are synthesized by the solvothermal method and the changing of physical properties is examined from structural, optical, morphological, and chemical composition measurements. The formation of anatase tetragonal phase TiO2 and hexagonal phase CdS are investigated from XRD. UV-vis and photoluminescence studies expose that the nanomaterials loaded with different amounts of CdS on TiO2 extend the absorption wavelength region from ultraviolet to visible. The photovoltaic performances of pure and CdS-added TiO2 nanoparticle have studied by current-voltage measurement and impedance spectral response. We have achieved the highest solar conversion efficiency of 2.89% with the aid of the CdS-sensitized TiO2 photoanode. CdS-sensitized TiO2 photoanode shows good stability as inferred from transient photocurrent and photovoltage measurements. Overall investigation describes that the inclusion of CdS into the TiO2 photoanodes gradually increase efficiency and stability.

Impact of Ferroelectric Polarization on Different Semiconductors for Photoelectrochemical Application

Introducing a built-in electric field into photoelectrochemical (PEC) system is considered as an effective strategy to tune interfacial energy band bending and manipulate charge transport direction. Here, we design the hybrid ferroelectric-semiconductor structure photoanodes for water oxidation, and the BaTiO3 is used for ferroelectric while monoclinic WO3, tetragonal TiO2, and triclinic CuWO4 for the semiconductors respectively. After the positive poling, 3 wt% BTO-WO3 and 3 wt% BTO-CuWO4 hybrid photoanodes perform significantly enhanced photocurrent of 68.5% and 62.9% compare with the pristine semiconductors. The efficiencies of charge separation and oxidation kinetics of these hybrid photoanodes increase by 14-19% and 1.38-1.42 fold, and the electron transport time decreases by 16%. Further, Kelvin probe force microscopy measurements indicate that the surface potential of hybrid structure is lower than unmodified samples, suggesting the space charge region near the semiconductor surface has been change...

Investigation of growth mechanism for highly oriented TiO2 nanorods: the role of reaction time and annealing temperature

Titanium dioxide (TiO2) is a versatile and inexpensive material for extended applicability in several scientific and technological fields including photo-catalysis for industrial waste treatment, energy harvesting, and hydrogen production. In this work, we report the synthesis of TiO2 thin film using hydrothermal method and investigations on the influence of reaction time and annealing temperature on growth mechanism of the TiO2 nanorods. The synthesized TiO2 films were studied by using UV–visible spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscope and energy-dispersive X-ray spectroscopy (EDS). The XRD and Raman measurements revealed the formation of defect free and pure tetragonal TiO2 rutile phase. The TiO2 thin films show absorption band edge at around 420 nm in the UV–visible spectrum and exhibit direct band gap value of 2.9 eV. The TiO2 nanorods are demonstrated to grow randomly on the FTO substrate with changing reaction times but grow uniformly in a flower-like pattern with increasing annealing temperature. Investigation of the field emission properties of TiO2 thin films (tested as field-emitter array) estimates the turn-on and threshold field at 4.06 and 7.06 V/µm at 10 and 100 µA/cm2, respectively.Graphic

Enhanced red emission of Eu3+ in ZnO-TiO2:Dy3+, Eu3+ nanocomposites by UV downconversion process

ZnO-TiO2:0.4 mol. %Dy3+,x mol. %Eu3+ (x = 0.05, 0.15, 0.25, 0.50, and 0.75) nanophosphors were synthesized using the solgel method. X-ray diffraction data confirmed crystallization of a mixture of wurtzite hexagonal ZnO and tetragonal TiO2 (anatase and rutile) nanocomposite phases. The nanocomposites were excited in the ultraviolet region with a wavelength of 248 nm, and the major narrowband emissions were observed in the visible range at 496, 584, 593, and 614 nm. The emissions at 496 and 584 nm were assigned to f → f transitions of Dy3+ ions from the upper 4F9/2 level to lower 6H15/2 and 6H13/2 levels, respectively, while those at 593 and 614 nm were assigned to f → f transitions of Eu3+ ions from the 5D0 level to the 5F1 and 5F2 levels, respectively. The effects of changing the Eu3+ concentrations on the PL intensity and energy transfer mechanisms from the charge transfer states and Dy3+ to Eu3+ are discussed. Energy transfer from Dy3+ to Eu3+ was confirmed by measuring the decay curves of orange-yellow and red emission of Dy3+ and Eu3+, respectively, in ZnO-TiO2:Dy3+,Eu3+.