Growth Of TiO Research Articles

A hybrid supercapacitor fabricated with an activated carbon as cathode and an urchin-like TiO2 as anode

In this paper, an asymmetric hybrid supercapacitor is fabricated using activated carbon as the cathode and urchin-like TiO2 as the anode. To investigate the electrochemical performance of the hybrid supercapacitor according to TiO2 growth, the reaction time during hydrothermal treatment is controlled. The electrochemical performance of the hybrid supercapacitor using urchin-like TiO2 with a reaction time of 20 h exhibits the best electrochemical performance. It has a capacitance of 61.2 F g−1, capacitance retention of 89% after 5000 cycles at 3 A g−1 and energy density of 50.6 Wh kg−1 at a power density of 194.4 kW kg−1. Therefore, the urchin-like TiO2 anode material has the potential to be used in electric vehicles (EVs).

Effect on the stabilization of the anatase phase and luminescent properties of samarium-doped TiO2 nanocrystals prepared by microwave irradiation

The structural and luminescent properties of TiO2 and TiO2:Sm3+ powder, synthesized by microwave irradiation using benzyl alcohol as solvent, were studied over an annealing range of 200–1000 °C. Structural and luminescent characterization was carried out by XRD, TEM, HRTEM, HRSEM and PL. Pure synthesized TiO2 presents similar structural characteristics to other methods and its transformation from the anatase to the rutile phase occurs between 600 and 800 °C. It was determined that the anatase phase of TiO2 is stabilized when doped with Sm3+, even at temperatures up to 1000 °C. Crystal growth of TiO2:Sm3+ powder is very slow, measuring 5 nm at 200 °C and 29 nm at 800 °C. It was observed that the particles consist of nano-sized crystals for all working conditions. Microwave irradiation technic allowed the successful incorporation of Sm3+ ions into the TiO2 host lattice, so it is reasonable to conclude that Sm3+ ions distorted octahedron of TiO6 to replace Ti4+ ions. TiO2:Sm3+ nanocrystals show emission of Sm3+ ion in the visible wavelength region. The visible photoluminescence correspond to transitions from the excited 4G5/2 level to the 6H11/2, 9/2, 7/2, 5/2 levels, respectively. The results of spectroscopic measurements of luminescence excitation, imply that Sm3+ emissions, are due to indirect excitation of the Sm3+ ions through an energy transference process from electron-hole pairs generated in the TiO2 host. The increased emission intensity is directly related with high crystallinity obtained by annealing treatment.

Preparation and characterization of nitrogen-doped TiO2/diatomite integrated photocatalytic pellet for the adsorption-degradation of tetracycline hydrochloride using visible light

Pharmaceutical wastes, such as antibiotics, have been successfully degradated by TiO2 under UV light irradiation. Yet, similar work has seldom been done by visible light responsive catalysts. In this work, we prepared N doped TiO2/diatomite integrated photocatalytic pellet (N-IPP), and evaluated its photoactivity by degradating tetracycline hydrochloride (TC) solution. According to the degradation results, optimal experimental and preparation conditions were determined. Besides, the effects of inorganic ions were also investigated: Ca2+, Mg2+, NO3−, SO42− and PO43−. According to BET results, the specific surface area of N-IPP pellet was similar to that of N-TiO2/diatomite powder. SEM and TEM images showed that, the hierarchical porous structure of diatomite helped TiO2 nanoparticles disperse well on its surface and prevented their agglomeration. XRD and XPS analysis revealed that, the formation of Si–O–Ti bond and N dopant restrained the crystal growth of TiO2. Various intermediates generated during degradation process were illustrated, and active species were determined using scavengers, then we concluded the degradation pathway and mechanism of N-IPP. Moreover, N-IPP exhibited good reusability and could be easily filtrated from the reactor.

Photocatalytic removal of SO2 over Mn doped titanium dioxide supported by multi-walled carbon nanotubes

In this paper, titanium dioxide supported by multi-walled carbon nanotubes (MWCNTs/TiO2), and Mn doped TiO2 supported by MWCNTs (MWCNTs/Mn-TiO2) were synthesized in a sol–gel method. Characterizations of these two prepared photocatalysts were analyzed by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance spectra (DRS). The results show that MWCNTs and Mn dopants inhibits the grain growth of TiO2. The excellent optical properties in UV and visible region were both observed on 0.5% MWCNTs/Mn-TiO2. The photocatalytic oxidation and removal efficiency of SO2 from simulated flue gas were investigated experimentally in a fix-bed reactor. Removal efficiency of SO2 can reach 69% while using 0.5% MWCNTs/Mn-TiO2 as photocatalysts at the optimal conditions (155 mg/m3 SO2, 8% O2, 5% H2O). The desulfurization efficiency was lower in the presence of NO due to the competition for adsorption sites between SO2 and NO. O2 and H2O played important roles in the photocatalytic oxidation of SO2. In addition, the possible reaction mechanism involved was also proposed here.

Thin-film growth of (110) rutile TiO2 on (100) Ge substrate by pulsed laser deposition

The deposition conditions of (100) rutile TiO2 grown on p-type (100) Ge substrates by pulsed laser deposition (PLD) were optimized to improve the electrical properties of the TiO2/Ge structure. Increasing the substrate temperature (Tsub) enhanced the grain growth, the surface roughness of the film, and Ge diffusion into the TiO2 layer. The growth rate, which was controlled by the laser density in PLD (Ld), affected the Ge diffusion. Ld of 0.35 J/cm2 (0.37 nm/min) enhanced the Ge diffusion and improved the crystallinity and surface roughness at a temperature of 450 °C, at which GeOx undergoes decomposition and desorption. However, the Ge diffusion into TiO2 degraded the electrical properties. By using the optimized conditions (Ld = 0.7 J/cm2 and Tsub = 420 °C) with postannealing, the TiO2/Ge structure showed an improvement in the leakage current of 3 orders of magnitude and the capacitance–voltage property characteristics indicated the formation of a p–n junction.

Two‐Step Oxidation of Mxene in the Synthesis of Layer‐Stacked Anatase Titania with Enhanced Lithium‐Storage Performance

AbstractLayer‐stacked anatase titania (a‐TiO2) was synthesized with two‐step oxidation of MXene (Ti3C2Tx, T=O, OH, or F). Compared with direct oxidation of MXene in air, the two‐step oxidation process involving additional hydrothermal pre‐oxidation could alleviate the anomalous grain growth of TiO2, and largely keep the fine structure of MXene. The layered structure derived from MXene enabled the synthesized a‐TiO2 to exhibit superior electrochemical properties. Its discharge capacities reached 241.9 and 131.1 mA h g−1 at the current rates of 0.3 and 12 C, respectively. Even after 10 000 cycles at 6 C, its capacity remained at 107.1 mA h g−1, which is approximately 70 % of the initial capacity. Cyclic voltammetry analysis showed that both diffusive lithium storage in the bulk and interfacial (pseudocapacitive) lithium storage at the surface of layer‐stacked a‐TiO2 contributed to its electrochemical properties.

Carbon and TiO2 synergistic effect on methylene blue adsorption

Due to its high efficiency, low cost and a simple operation, the adsorption process is an important and widely used technique for industrial wastewater treatment. Recent studies on the removal of artificial dyes by adsorption include a large number of adsorbents, such as: activated carbon, silicates, carbon nanotube, graphene, fibers, titanates and doped titanates. The carbon insertion in the TiO2 structure promotes a synergistic effect on the adsorbent composite, improving the adsorption and the charge-transfer efficiency rates. However, there are few studies regarding the adsorption capacity of TiO2/Carbon composites with the carbon concentration. This study evaluates the effect of carbon (resorcinol/formaldehyde) insertion on TiO2 structure through the adsorption process. Adsorbents were prepared by varying the carbon weight percentages using the sol-gel method. The physicochemical properties of the catalysts prepared, such as crystallinity, particle size, surface morphology, specific surface area and pore volume were investigated. The kinetic study, adsorption isotherm, pH effect and thermodynamic study were examined in batch experiments using methylene blue as organic molecule. In addition, the effect of carbon phase on the adsorption capacity of TiO2-carbon composite was deeply investigated. SEM micrographs showed that TiO2 phase grows along the carbon phase and FT-IR results showed the presence of TiOC chemical bonding. The experiments indicate that the carbon phase acted as a nucleation agent for the growth of TiO2 during the sol-gel step, with a TiO2 structure suitable for blue methylene adsorption, resulting in a material with large surface area and slit-like or wedge-shaped pores. Further experiments will show the best carbon concentration for methylene blue adsorption using a TiO2 based material.

(Invited) Development of New High-Dielectric Constant Thin Film Materials for Next-Generation Nanoelectronics

The development of high-dielectric constant thin film materials is essential for future active and passive nanoelectronics devices. Recently we have developed high-dielectric constant thin film materials for thin film capacitor and gate dielectrics. In the case of the high-dielectric constant thin film material for the passive devices, we focused on the power device application. Compound semiconducter based power devices such as SiC require high-temperature operational passive devices such as a capacitor, resistor and inductors. SiC based active devices are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. In the casse of capacitors, current available capacitors can efficiently function up to 175°C only. Therefore, a thin-film capacitor that can be operated at high-temperatures and integrated monolithically in the proximity of active device should be developed. The BaTiO3 based relaxor ferroelectrics wiht a high dielectric constant (> 200) and free of hazardous elements, are promising candidates. Among the BaTiO3 based relaxor ferroelectrics, we have chosen x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] (BT-BMN) due to its high dielectric constant and temperature stability in the bulk form. However, a thin-film process of this ceramic is not available yet. Moreover, the control of Bi composition, which affects on dielectric constant and ferroelectricity strongly, is challenging due to high volatility of Bi. In this context, high throughput combinatorial synthesis method is effective in the fast optimization of the Bi composition. By employing combinatorial method and the thermal diffusion theory, we have developed a thin-film processing technology for BT-BMN films. The dielectric constant of BT-BMN is close to 400 and the stability is <8% from room temperature to 400°C, which are promising as a high-temperature dielectric medium. In the presentation, we also briefly introduce the development of high-k gate materials for aGe channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.

Correction to "Anisotropic Growth of TiO2 onto Gold Nanorods for Plasmon-Enhanced Hydrogen Production from Water Reduction".

Correction to "Anisotropic Growth of TiO2 onto Gold Nanorods for Plasmon-Enhanced Hydrogen Production from Water Reduction".

Catalytic oxidation and capture of elemental mercury from simulated flue gas using Mn-doped titanium dioxide

Titanium dioxide (TiO2) and Mn-doped TiO2 (Mn(x)-TiO2) were synthesized in a sol-gel method and characterized by BET surface area analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Gasphase elemental mercury (Hg0) oxidation and capture by the Mn-doped TiO2 catalyst was studied in the simulated flue gas in a fixed-bed reactor. The investigation of the influence of Mn loading, flue gas components (SO2, NO, O2, and H2O) showed that the Hg0 capture capability of Mn(x)-TiO2 was much higher than that of pure TiO2. The addition of Mn inhibits the grain growth of TiO2 and improves the porous structure parameters of Mn(x)-TiO2. Excellent Hg0 oxidation performance was observed with the catalyst with 10% of Mn loading ratio and 97% of Hg0 oxidation was achieved under the test condition (120 °C, N2/6%O2). The presence of O2 and NO had positive effect on the Hg0 removal efficiency, while mercury capture capacity was reduced in the presence of SO2 and H2O. XPS spectra results reveal that the mercury is mainly present in its oxidized form (HgO) in the spent catalyst and Mn4+ doped on the surface of TiO2 is partially converted into Mn3+ which indicates Mn and the lattice oxygen are involved in Hg0 oxidation reactions.

Effects of tin doping level on structure, acidity and catalytic performance of Ti-Ce-Ox catalyst for selective catalytic reduction of NO by ammonia

A series of tin-doped Ti-Ce-Ox complex oxide catalysts were synthesized by sol–gel method and tested for selective catalytic reduction of NOx with NH3 (NH3-SCR). Effects of tin additives on structure, acidity and catalytic performance of Ti-Ce-Ox for NH3-SCR of NO were investigated through characterization of N2 adsorption–desorption, H2-TPR, XRD, NH3-TPD and SEM. Results showed that tin additives extended the active temperature window especially toward lower temperatures and the NO conversion efficiency of Ti-Sn-Ce-Ox (the Ti/Sn is equal to 4) catalyst reached 92% at 200°C. The addition of tin not only inhibit grain growth of CeO2 and TiO2, but also expand unit cell and cause lattice distortion, which are especially beneficial to NH3-SCR. Moreover the introduction of tin also improved redox property significantly and enhance the acidity of catalyst. The anti-sulfur and anti-influence of water performance of catalyst also improved by tin-doped, when injecting 300ppm SO2 and 10vol.% H2O, the NO conversion efficiency of Ti-Sn-Ce-Ox catalyst was still reached 85% at 200°C.

Fabrication of TiO2/C3N4 heterostructure for enhanced photocatalytic Z-scheme overall water splitting

Z-scheme overall water splitting based on semiconductors has been extensively investigated for hydrogen fuel production from renewable resources. The Z-scheme involves two different kinds of semiconductor photocatalysts and the closely related oxidation-reduction processes. However, the two separated photocatalytic processes require good production and separation of carriers, which greatly limit the efficiency of overall water splitting. Herein, to solve the recombination problem of photogenerated charge carriers, we developed a one-step hydrothermal process to synthesize TiO2/C3N4 heterojunctions. The layered g-C3N4 provides the template and guidance for the anatase TiO2 heterogeneous nucleation with (001) facet exposed. Meanwhile, the bulk g-C3N4 turned into thicker nanosheets through the self-exfoliation with the growth of TiO2. The heterojunctions with TiO2 (001) facet exposed ensure the efficient separation of photogenerated carriers, which accordingly enhances the photocatalytic hydrogen evolution. WO3 and BiVO4 are chosen as photocatalysts for the half reaction of oxygen evolution. With suitable redox mediators i.e. I−/IO3− or Fe2+/Fe3+, the overall water splitting to H2 and O2 could be achieved. If β-Ni(OH)2, was loaded on the oxygen evolution photocatalysts, the efficiency of Z-scheme water splitting was greatly enhanced. Under the monochromatic light irradiation of LEDs, the apparent quantum efficiency (AQE) values for the Z-scheme of TiO2/C3N4, β-Ni(OH)2/WO3(PtOx) and I−/IO3− system were 4.94% and 4.01% under 365 and 405nm, respectively. The heterojunction strategy for enhancing Z-scheme overall water splitting may give us some hints on the design of composite systems for overall water splitting.

Atomically flat reconstructed rutile TiO2(001) surfaces for oxide film growth

The availability of low-index rutile TiO2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxial growth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO2(001) surfaces can be prepared with an atomically ordered reconstructed surface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surface energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxial growth of TiO2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.

Synergistic effects of F and Fe in co-doped TiO2 nanoparticles

TiO2 photocatalysts co-doped with F and Fe were synthesized by a sol–gel method. Synergistic effects of F and Fe in the co-doped TiO2 were verified by NH3 decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–Vis) absorption spectroscopy, and was analyzed by the simulation based on the density functional theory (DFT). The results from NH3 decomposition confirmed that the cooperation of F and Fe broadened the optical response of TiO2 to visible light region and also enhanced the photocatalytic activity of TiO2 under ultraviolet light. XRD patterns, SEM and HRTEM images showed that the co-doped samples were nanometric anatase with an average particle size of 25 nm. Co-doping with F and Fe inhibited the grain growth of TiO2 from anatase to rutile and resulted in a larger lattice defect. XPS analysis exhibited that the doped F and Fe atoms were into the TiO2 lattice. UV–Vis absorption spectra showed that its optical absorption edge was moved up to approximately 617 nm and its ultraviolet absorption was also enhanced. The DFT results indicated that the cooperation of Fe 3d and O 2p orbits narrowed the band gap of TiO2 and F 2p orbit widened the upper valence bands. The synergistic electron density around F and Fe in co-doped TiO2 was capable to enhance the photo-chemical stability of TiO2.

Dye sensitized solar cells based on hydrothermally grown TiO2 nanostars over nanorods

A rutile titanium dioxide nanostar over nanorods is synthesized by a simple and cost-effective hydrothermal deposition method onto conducting glass substrates. In order to study the effect of precursor concentrations on the growth of TiO2, the amount of Ti precursor is varied from 0.1mL to 0.5mL at the interval of 0.1mL. These TiO2 thin films are characterized for their morphological, structural, optical and J–V properties using various characterization techniques. SEM images showed the formation of densely packed nanostars over nanorods for 0.3mL titanium tetraisopropoxide (TTIP). XRD patterns show the formation of polycrystalline TiO2 with tetragonal crystal structure possessing rutile phase. Further, the TiO2 thin films are used for dye sensitized solar cells using N3-dye.The films were photoelectrochemically active and can be viewed as a promising application in DSSC with maximum current density of 1.459mA/cm2 with enhanced photovoltage of 696mV for the sample prepared at 0.3mL TTIP.

Solid phase epitaxial regrowth of (001) anatase titanium dioxide

The growing interest in metal oxide based semiconductor technologies has driven the need to produce high quality epitaxial films of one metal oxide upon another. Largely unrecognized in synthetic efforts is that some metal oxides offer strongly polar surfaces and interfaces that require electrostatic stabilization to avoid a physically implausible divergence in the potential. The present work examines these issues for epitaxial growth of anatase TiO2 on strontium titanate (001). Solid phase epitaxial regrowth yields only the (001) facet, while direct crystalline growth by atomic layer deposition yields both the (112) and (001). The presence of amorphous TiO2 during regrowth may provide preferential stabilization for formation of the (001) facet.

ANTIBACTERIAL ACTIVITY OF TiO2 THIN FILMS AGAINST GRAM NEGATIVE OF BACTERIAL STRAINS

Titanium dioxide (TiO 2 ) is one of the most important semiconductors. It has attracted a growing attention in huge applications because of their unique properties. In this present survey we are interesting to investigate the resist growth of TiO 2 thin films with various dopants against gram negative of Escherichia coli bacteria. TiO 2 thin films were deposited on soda lime glass and tissue by two different methods (spray pyrolysis and sol-gel) in order to study their effect on antibacterial activity. We used two processes of bacteria and in the both the results indicate that TiO 2 can resist the growth of E. coli. The zone of inhibition of this bacterium is found between 11 and 17 mm.

Effect of substrate-enhanced and inhibited growth on atomic layer deposition and properties of aluminum–titanium oxide films

Atomic layer deposition of aluminum–titanium oxide films from different precursor combinations was investigated. In addition to well-known TiCl4–H2O, AlCl3–H2O and Al(CH3)3–H2O ALD processes, combination of hydrogen-free TiCl4–O3 and AlCl3–O3 processes was used. Most of the films were grown at 350°C because this temperature ensured reliable growth of TiO2 and Al2O3 in all processes combined. The films were deposited using supercycles that contained 1–60 successive cycles for deposition of TiO2 followed by 1–3cycles for deposition of Al2O3. The films were amorphous, when 15 or less TiO2 cycles per Al2O3 cycle were applied in a supercycle, and contained anatase when ≥30 TiO2 cycles were applied. A marked increase in the Al deposition per cycle was observed with the increase of the number of TiO2 cycles per supercycle from 0 to 5–10. With the further increase of the number of TiO2 cycles from 15 per supercycle to higher values, the Al deposition per cycle depended on the precursor combination used. The Ti deposition per cycle depended, in turn, on the precursor system used for deposition of Al2O3 layers. Deposition of Ti was most significantly hindered on Al2O3-rich surface deposited from AlCl3–O3 and markedly enhanced on Al2O3 deposited from Al(CH3)3–H2O. In addition, the phase composition markedly influenced the growth rate of both components as well as the mean growth rate and surface roughness of the films.

Simultaneous Cu doping and growth of TiO2 nanocrystalline array film as a glucose biosensor

Copper ion doping and growth of a TiO2 nanocrystalline material can be realized by using colloidal nanoparticles as a reactive precursor. Such an efficient doping design facilitates the use of TiO2 as a potential biosensor for glucose molecules.

Growth of TiO&lt;sub&gt;2&lt;/sub&gt; Thin Films by Atomic Layer Deposition (ALD)

Ceramic oxide thin films are an important material, with applications in many areas of science and technology. Titanium oxide (TiO2) is also a well-known and important material for applications such as gas sensors [1], photocatalysis materials [3], and electrochemicals [1], due to its self-cleaning [2], good corrosion resistance and biocompatibility. Atomic Layer Deposition (ALD) is a nanotechnology tool that is used for the deposition of nanostructured thin films. The unique advantage of ALD is the self-limiting film growth mechanism, which offers attractive properties, simple and accurate film thickness control, sharp interfaces, uniformity over large areas, excellent conformality, good reproducibility, a multilayer processing capability, and high quality films at low temperatures [3, 4]. TiO2 thin films were grown using TTIP (Titanium isopropoxide) ALD on silicon wafers, glass slides, and stainless steel plates in order to study the effect of substrates on the growth of TiO2. In order to achieve the desired advantages of using TTIP, a series of experiments were performed to study the growth mechanism of TiO2 thin films using TTIP and H2O by ALD.