Titania Gel Research Articles

Crystallization mechanism of barium titanate in amorphous titania gel pellets by acid–base chemical densification near room temperature

Crystallization mechanism of barium titanate in amorphous titania gel pellets by acid–base chemical densification near room temperature

Submicron titania pattern fabrication via thermal nanoimprint printing and microstructural analysis of printable titania gels

Titania is a functional oxide used as a catalyst and photocatalyst, which has various applications. Modifying the surface morphology and creating micro patterns on titania can significantly enhance its catalytic efficiency and utility in semiconductor devices. This study focuses on the fabrication of submicron patterns on titania using thermal nanoimprinting. The process involves the preparation of a high-viscosity sol consisting of 2-butoxyethanol, titanium butoxide, ethylene glycol, and water, followed by drying on a substrate to obtain a printable titania gel. We investigated the structural characteristics of this printable titania gel using Fourier transform infrared thermal analysis and high-energy X-ray diffraction. These structural analyses shed light on the critical factors affecting the growth of the Ti–O network within the gel and the effect of the organic content of the gel on its properties.

Optimization of Mass and Light Transport in Nanoparticle-Based Titania Aerogels.

Aerogels composed of preformed titania nanocrystals exhibit a large surface area, open porosity, and high crystallinity, making these materials appealing for applications in gas-phase photocatalysis. Recent studies on nanoparticle-based titania aerogels have mainly focused on optimizing their composition to improve photocatalytic performance. Little attention has been paid to modification at the microstructural level to control fundamental properties such as gas permeability and light transmittance, although these features are of fundamental importance, especially for photocatalysts of macroscopic size. In this study, we systematically control the porosity and transparency of titania gels and aerogels by adjusting the particle loading and nonsolvent fraction during the gelation step. Mass transport and light transport were assessed by gas permeability and light attenuation measurements, and the results were related to the microstructure determined by gas sorption analysis and scanning electron microscopy. Mass transport through the aerogel network was found to proceed primarily via Knudsen diffusion leading to relatively low permeabilities in the range of 10-5-10-6 m2/s, despite very high porosities of 96-99%. While permeability was found to depend mainly on particle loading, the optical properties are predominantly affected by the amount of nonsolvent during gelation, allowing independent tuning of mass and light transport.

Degradation of o-dichlorobenzene by DBD-NTP co-modified titanium gel catalyst

In order to study the degradation process of dioxins in industrial flue gas, the decomposition of o-dichlorobenzene (o-DCB) in a DBD plasma catalytic reactor was investigated. The results showed that an NTP-catalyzed system, especially using the CuMnTiOx catalyst, had better o-DCB degradation performance compared to plasma alone. The combination of the CuMnTiOx catalyst with NTP can achieve a degradation efficiency of up to 97.2% for o-DCB; the selectivity of CO and CO2 and the carbon balance were 40%, 45%, and 85%, respectively. The dielectric constant and electrical property results indicated that the surface discharge capacity of the catalysts played a major role in the degradation of o-DCB, and a higher dielectric constant could suppress the plasma expansion and enhance the duration of the plasma discharge per discharge cycle. According to the O1s XPS and O2-TPD results, the conversion of CO to CO2 follows the M-v-K mechanism; thus, the active species on the catalyst surface play an important role. Moreover, the CuMnTiOx and NTP mixed system exhibited excellent stability, which is probably because Cu doping improved the lifetime of the catalyst. This work can provide an experimental and theoretical basis for research in the degradation of o-DCB by plasma catalyst systems.

Hierarchically Structured NH2‐MIL‐125/TiO2/Cellulose Composite Membranes With Enhanced Photocatalytic Performance

AbstractA cellulose‐based photocatalytic membrane was fabricated by in situ growth of the NH2‐MIL‐125 nanoparticles onto the surfaces of the ultrathin titania (TiO2) gel layers pre‐coated cellulose nanofibres of natural cellulose substance (commercial laboratory filter paper). The NH2‐MIL‐125 nanoparticles were grown on the surface of the titania gel coated cellulose nanofibres via a one‐step solvothermal method. The resultant composite membranes maintained the initial hierarchical network structures of the bulk cellulose substance, consisting titania gel layer coated cellulose nanofibres with NH2‐MIL‐125 nanoparticles anchored on the surfaces. Owing to the hierarchical porous structure of the cellulose substrates as well as the effective heterostructure formation between the NH2‐MIL‐125 particles and the TiO2 layers, the composites showed enhanced photocatalytic performances. The NH2‐MIL‐125/TiO2/cellulose composite composed of 15.82 wt% NH2‐MIL‐125 content with nanoparticles sizes of 100–200 nm showed an apparent rate constant of 0.032 min−1 in photocatalytic degradation of Rhodamine B (RhB), which was higher than those of the NH2‐MIL‐125/cellulose composite and the TiO2/cellulose composite. It was demonstrated that pre‐coating of the cellulose nanofibres with ultrathin titania gel layers was essential for the growth of the NH2‐MIL‐125 nanoparticles thereon.

Structure, light absorption properties and photocatalytic activity of carbon-containing titania nanocomposites synthesized via a facile sol–gel method

Facile and green sol–gel method was used to synthesize carbon-containing titania nanopowder, and diethanolamine (DEA) was used as the in situ carbon source. The titania gel was heat treated at temperatures ranging from 300 to 700 °C. X-ray diffraction (XRD), thermal analysis, and Raman spectroscopy reported no crystalline phase at <325 °C. Crystallization of the anatase phase with traces of brookite phases was observed at T > 325 °C, followed by a transformation to anatase/rutile in the range of 400 °C < T ≤ 650 °C. Finally, the complete phase transformation to the rutile phase occurs at temperatures of T > 650 °C. High-resolution electron microscopy (HREM) micrographs confirm the coexistence of anatase and rutile nanocrystals and amorphous carbon clusters in the composite samples. Chemical element analysis via X-ray photoelectron spectroscopy (XPS) indicated nonstoichiometry in the O/Ti ratio, the presence of (Ti3+) oxidation state, and elemental carbon. Thermogravimetric (TG) measurements are the most accurate method to measure the carbon content in samples. UV-vis spectroscopy demonstrated considerable enhancement in the optical absorption properties and electronic structure of prepared samples compared to the pure anatase and rutile. This enhancement is strongly correlated with the structure and composition of prepared samples and consequently depends on the preparation method as well as conditions. Innovative features such as self-cleaning action was demonstrated in carbon containing titanate nanocomposite.

Fundamental properties of alkoxide-derived titania gel films providing plastics surface with high refractive index

Fundamental properties of alkoxide-derived titania gel films providing plastics surface with high refractive index

Sol–Gel Approach for Design of Pt/Al2O3-TiO2 System—Synthesis and Catalytic Tests

Al2O3-TiO2 systems with Ti:Al 0.1, 0.5 and 1.0 molar ratio obtained by the sol–gel method have been used as a platinum support. As a precursor of alumina gel, aluminum isopropoxide has been chosen. Titanium tert-butoxylate was applied to obtain titania gel and hexachloroplatinic acid was applied as a source of platinum. The systems have been characterized by the following methods: thermogravimetric analysis (TGA), Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), low-temperature nitrogen adsorption–desorption isotherms (BET, BJH), temperature-programmed reduction with hydrogen (TPR-H2) and hydrogen chemisorption. Reactions of toluene to methylcyclohexane and selective o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) hydrogenation were used as the tests of systems’ catalytic activity. The application of Al2O3-TiO2 as a support has enabled the obtaining of platinum catalysts showing high activities for hydrogenation of toluene and selective hydrogenation of o-chloronitrobenzene to o-chloroaniline in the liquid phase. The highest activity in both reactions has been found for Pt/Al2O3-0.5TiO2 catalyst and the highest selectivity for Pt/Al2O3-. The activity of Pt/Al2O3-TiO2 catalysts was higher than that of alumina-supported ones.

Preparation of Polymer-Immobilized Polyimide Films Using Hot Pressing and Titania Coatings.

Recent studies have revealed that polymer molecules at film surfaces exhibit unique physical properties compared to those in bulk. On the other hand, such a topic has not been extensively focused for the cases of rigid polymers such as polyimide (PI). This study investigated whether hot pressing could induce the immobilization of other polymers, poly(4-vinylphenol) (PVP), on PI film surfaces. Results supported the immobilization of PVP on the PI film surfaces, and the increase of hot-press temperature resulted in the increase of the immobilization amount of PVP. The mechanism of immobilization is discussed considering the effects of hot pressing on the interactions between PVP and PI at the interfaces of their films. Sol–gel titania coatings were further conducted to the obtained PVP-immobilized PI films. The effect of PVP immobilization on formability and the adhesion of titania layers on the film surfaces were evaluated. These results demonstrate that hot pressing of other polymers is a useful approach for the surface modification of PI films, particularly introducing certain functional groups, and indicate that the polymer immobilization mechanism might be correlated with the surface physical properties of PI films.

Development of Sunscreen Products Containing Titanium Dioxide and &lt;i&gt;Aloe vera&lt;/i&gt; Gel

This study aimed to develop sunscreen emulsion from natural sunscreening agents, titanium dioxide and Aloe vera gel extract that have good sun protection efficacy. The effects of formulation variables i.e., particle size and amount of titanium dioxide, amount of Aloe vera gel extract (spray dried powder) and combination of sunscreening agents (titanium dioxide and Aloe vera gel extract) on physical properties and sun protection efficacy (e.g., SPF, UVA/UVB ratio, critical wavelength) of sunscreen products were evaluated. The results showed that the smaller particle size of titanium dioxide improved the sun protection efficacy and increased the UVB absorption edge of the products. SPF of the formulations could be ranked as Nanofine TiO2 (particle size 25–30 nm) &gt; Kingruti T-01 TiO2 (particle size 200 nm) &gt; Pigment TiO2 (particle size &lt; 45,000 nm) and UVA/UVB ratio and critical wavelength of the formulations could be arranged in order as follows: Nanofine TiO2 &lt; Kingruti T-01 TiO2 &lt; Pigment TiO2. Increasing amount of titanium dioxide from 5 to 15 %w/w increased significantly viscosity and SPF of formulations. Aloe vera gel extract itself did not significantly affect SPF, however, combination of Aloe vera gel extract and titanium dioxide seemed to have synergistic effect on sun protection efficacy and decreased viscosity of the formulation. According to the results, the good sunscreen formulation consisted of 15 %w/w Nanofine TiO2, 5 %w/w Aloe vera gel spray dried powder in emulsion base because it was broad spectrum sunscreen and showed high SPF (27.53±1.92), high UVA/UVB ratio with critical wavelength higher than 370 nm.

In-plane stress development in sol–gel-derived titania and silica thin films on Si(100) substrates

In order to study (i) how the in-plane stress develops in alkoxide-derived oxide gel films on heating and (ii) how the residual stress changes with firing temperature, we prepared titania and silica gel films on Si(100) wafers from alkoxide solutions. The intrinsic stress was previously measured in situ during heating up to 500 °C for the gel films, where the stress was calculated from the radius of curvature of the substrate bending. Because the commercialized apparatus that measures the substrate bending has an upper limitation of temperature at 500 °C, we devised a method for estimating the intrinsic stress over 500 °C in the present work. The gel films were heated from 100 °C up to 900 or 1000 °C successively and cumulatively. Then we estimated the intrinsic stress over 500 °C by monitoring the changes in stress in situ during heating and cooling for the cumulatively fired films. Combining the estimated data over 500 °C with those measured below 500 °C, we found that the intrinsic stress increases and then decreases around to zero with temperature for both titania and silica gel films, which we recognized as a general trend in alkoxide-derived oxide thin films in conjunction with our previous work on yttria stabilized zirconia (YSZ) films. Regarding the residual stress, the titania and silica films exhibited different behaviors. The titania film showed an increase followed by a slight decrease, and finally a significant increase in residual tensile stress with increasing firing temperature. The silica films also exhibited an increase and a decrease in residual tensile stress with increasing firing temperature, but the stress continued to decrease and turned into compressive one at ca 800 °C. The last decrease in residual tensile stress that turned into compressive one resulted from the development of compressive thermal stress during cooling, which is due to the smaller thermal expansion coefficient of silica than silicon. It was thus clarified that the difference in thermal expansion coefficient between the film and the substrate becomes prominent in residual stress when the films are fired at high temperatures like 800 °C. Thus we could successfully obtain a general view on how the residual stress changes with firing temperature as well as on how the in-plane stress develops during heating thanks to the information on the stress development in the sol–gel-derived titania and silica films that was added to the information on the YSZ films.

The synergistic role of pH and calcination temperature in sol–gel titanium dioxide powders

Titanium dioxide (TiO2) nanoparticles were prepared by the sol–gel method starting from a volume of 1.5 mL of titanium tetraisopropoxide (TTIP) dissolved in 10 mL of ultrapure water milliQ grade (pH 5). The pH of the solution was adjusted by adding HNO3 and NaOH to reach an acidic and basic character of the sol, respectively. A wide pH range from 1 to 10 was explored. The prepared TiO2 nanopowders were annealed at three different calcination temperatures, 100, 450 and 800 °C for 3 h. The synergic effect of pH and calcination temperature on the structural and morphological properties of TiO2 nanoparticles was investigated by XRD and Raman analyses. At the lowest (100 °C) and highest (800 °C) calcination temperatures, we observed the dominance of anatase and rutile phases, respectively. A mixture of these phases was observed for the titania powders calcinated at 450 °C. In particular, the nanoparticles produced in strong acidic medium showed a coexistence of anatase and rutile with a dominance of rutile, whereas the anatase was the crystalline phase favored in alkaline medium environment.

Thermoplastic polyurethane/poly(methyl methacrylate)/titania gel electrolyte film with high voltage and coulombic efficiency for lithium-ion battery

Polymer films composed of thermoplastic polyurethane (TPU), poly (methyl methacrylate) (PMMA), and titania were developed by solution-casting method. Accordingly, gel polymer electrolytes (GPEs) were prepared by soaking the films in commercial liquid electrolytes for 8 h. The prepared GPEs could fix the liquid electrolytes inside and kept the shape stable. The hybrid GPEs exhibited a maximum ionic conductivity of 3.9 × 10−3 S‌‌‍ cm−1 at room temperature, with an electrochemical stability of up to 4.8 V versus Li+/Li. The compatibility test demonstrated that the introduction of PMMA and TiO2 improved the interfacial compatibility between lithium and GPEs. In battery test, the Li/GPE/LiFePO4 cell delivered the first discharge capacity of 169.2 mAh g−1 at 0.1 C and stable cycle performance (the retention of capacity is nearly 92% after 60 cycles) with high coulombic efficiency. All results demonstrated that the hybrid GPE was promising to satisfy the application in the future.

Flexible Dye-sensitized Solar Cell Using Titanium Gel at Low Temperature

Flexible dye-sensitized solar cells using binder free TiO2 paste for low temperature sintering are developed. In this paste a small amount of titanium gel is added to a paste of TiO2 nanoparticle. Analysis of titanium gel paste prepared at 150 °C shows that it has a pure anatase phase in XRD and mesoporous structure in SEM. The formation of the titanium gel 1- 2 nm coated layer is confirmed by comparing the TEM image analysis of the titanium gel paste and the pristine paste. This coating layer improves the excited electron transfer and electrical contact between particles. The J-V curves of the organic binder DSSCs fabricated at 150 °C shows a current density of 0.12 mA/cm2 and an open-circuit voltage of 0.47 V, while the titanium gel DSSCs improves electrical characteristics to 5.04 mA/cm2 and 0.74 V. As a result, the photoelectric conversion efficiency of the organic binder DSSC prepared at low temperature is as low as 0.02 %, but the titanium gel paste DSSCs has a measured effciency of 2.76%.

Fluorescent perylene derivative functionalized titanium oxide gel for sensitive and portable ascorbic acid detection.

An inorganic titanium oxide (TiO) gel sensor was demonstrated for convenient detection of ascorbic acid (AA). It is composed of TiO (PI–TiO) functionalized with a perylene diimide derivative containing carboxylic groups as a new soft dopant material. A traditional solvothermal reaction is adopted to prepare the PI–TiO composite, which exhibits a different spectrum according to the reaction time. The final gel possesses a strong chelating affinity with AA molecules, in which phenol hydroxyl groups are shown to compete with those already present in PI. We further utilize the functionalized gel to prepare a series of films with a simple and portable AA response. A visual colour variation can be recognized by the naked eye, together with obvious fluorescence changes for selective and sensitive AA detection. Finally, the as-prepared gel film displays good stability and reproducibility for real sample responses with satisfying results.

色素分散チタニアゲルにおける色素分子のナノ粒子表面との相互作用と蛍光特性

色素分散チタニアゲルにおける色素分子のナノ粒子表面との相互作用と蛍光特性

Structural and Thermal Studies of Titanium Dioxide Gel Modified with Anatase Isostructural Zircon Silicate

Important changes in anatase crystal structure are responsible for the consequent anatase-to-rutile phase transition in titanium dioxide powders. In order to investigate several structural rearrangements occurring in anatase phase obtained by hydrolysis-based method such as Sol-Gel method the X-ray diffraction techniques followed by Rietveld method seems to better approach. Several alterations in anatase lattice parameters can occur by doping insertion and the investigation of isostructural zircon silicate can provide interesting ones. In the present paper, the monitoring of anatase structure reordering and the consequent anatase-to-rutile phase transition along the thermal treatment up to higher temperatures were monitored carrying out DSC and XRD characterizations. The insertion of 6 mol% of zircon silicate leads to the fully anatase stabilization up to 900 °C due the control of ordering process, even that a continuous increasing in anatase tetragonality is present during the entire process. We can conclude the reconstructive anatase-to-rutile phase transition is delayed to very higher temperatures can consequence of more stable cross-linked metal oxide bond in anatase phase.

Phase transition and crystal growth of a titania layer on a titanium metal plate

A titanium metal surface was heated with an alkali metal chloride in order to produce a phase transition from amorphous titania to crystalline titania on the surface. The crystalline phase was identified by XRD and Raman spectroscopic analyses. The anatase-type titania phase was formed by heating the surface with KCl or CsCl at 500–550 °C for 3 h. The heating at a higher temperature caused a transition to the rutile-type titania. The amorphous titania layer on the surface of the titanium metal was reduced with assistance of the alkali metal chloride and re-oxidized to transform into the metastable anatase-type titania phase under certain conditions. The surface layer having the anatase titania phase exhibited the faster photocatalytic degradation of acetaldehyde, which was demonstrated by gas chromatography and FTIR spectroscopic measurement. Furthermore, the titanium metal coated with KCl and subsequent titanium alkoxide sol was heated in order to form a thicker titania film. The structural characterization of the film surface was conducted by XRD, Raman spectroscopy, and XPS analyses. Larger anatase-type titania crystallites were clearly formed on the titanium metal surface, to which they strongly adhered by heating at 500–550 °C for 30 min. The deposited KCl promoted the crystallization of the original amorphous titania and coated titania gel layers. The particle size of the titania film was also confirmed by SEM and TEM observations. The surface layer having the thicker anatase titania phase exhibited the faster photocatalytic degradation of acetaldehyde.

Development and Characterization of Titanium Dioxide Gel with Encapsulated Bacteriorhodopsin for Hydrogen Production.

We study bacteriorhodopsin (BR) in its native purple membrane encapsulated within amorphous titanium dioxide, or titania, gels and in the presence of titania sol particles to explore this system for hydrogen production. Förster resonance energy transfer between BR and titanium dioxide sol particles was used to conclude that there is nanometer-scale proximity of bacteriorhodopsin to the titanium dioxide. The detection of BR-titania sol aggregates by fluorescence anisotropy and particle sizing indicated the affinity amorphous titania has for BR without the use of additional cross-linkers. UV-vis spectroscopy of BR-titania gels shows that methanol addition did not denature BR at a 25 mM concentration presence as a sacrificial electron donor. Additionally, confinement of BR in the gels significantly limited protein denaturation at higher concentration of added methanol or ethanol. Subsequently, titania gels fabricated through the sol-gel process using a titanium ethoxide precursor, water, and the addition of 25 mM methanol were used to encapsulate BR and a platinum reduction catalyst for the production of hydrogen gas under white light irradiation. The inclusion of 5 μM bacteriorhodopsin resulted in a hydrogen production rate of about 3.8 μmol hydrogen mL-1 h-1, an increase of 52% compared to gels containing no protein. Electron transfer and proton pumping by BR in close proximity to the titania gel surface are feasible explanations for the enhanced production of hydrogen without the need to cross-link BR to the titania gel. This work sets the stage for further developments of amorphous, rather than crystalline, titania-encapsulated bacteriorhodopsin for solar-driven hydrogen production through water splitting.

Characterization of Surface-Treated NiTi Alloy by Various Electrochemical Techniques in Phosphate-Buffered Saline

Sol–gel titania thin film coating was prepared on NiTi surfaces, modified with acidified ferric chloride solution. Nanogrids formed on chemical treatment were uniformly covered with titania coating. Cyclic voltammetry studies in phosphate-buffered saline solution revealed that sol–gel titania-coated surface displayed electrochemical properties which were similar to those observed for pure titanium. During polarization, the passive layer formed on modified NiTi was stable for potentials greater than 0.9 V. The overall resistance measured by electrochemical impedance spectroscopy for sol–gel titania surface was in the order of 105 Ω, which was approximately two orders higher than bare NiTi surface. The current noise analyzed using electrochemical noise measurements was minimum after sol–gel coating, which emphasizes the better protection power of the surface from the attack of corrosive species. Dynamic impedance studies carried out on bare and titania-coated NiTi also supports the results obtained from cyclic polarization.