Rutile Particles Research Articles

Preparation of highly porous TiO2nanotubes and their catalytic applications

A simple procedure for preparing highly porous TiO2 nanotubes is reported. The nanotubes were prepared in the form of a nonwoven mat by emulsion electrospinning a solution containing poly(vinyl pyrrolidone), titanium tetraisopropoxide and oil, followed by calcination in air at 500 °C. The mixed crystalline material comprised anatase and rutile TiO2 particles, whose diameters were about 11 nm and 21 nm, respectively. The highly porous TiO2 nanotube membranes, which had large specific surface areas and excellent ratios of anatase phase to rutile phase, were shown to have excellent catalytic activities. Also the mixture of crystal forms improved the efficiency of photocatalysis because at the mixed interface electrons and holes are separated effectively. The new method for producing highly porous TiO2 nanotubes is versatile and could be extended to the fabrication of various types of highly porous nanotubes.

Formation of TiO2 photoanodes by simultaneous electrophoretic deposition of anatase and rutile particles for photoassisted electrolytic copper ions removal

The influence of Anatasa/Rutile ratio on TiO2 films, grown by electrophoretic deposition was studied in the photoassisted electrolytic copper ions removal from cyanide solutions. The proper dispersant dosage allowing the simultaneous electrophoretic deposition of Anatase and Rutile was chosen based on electrokinetic measurements; evidenced by the XRD spectra of the formed films. The evaluation of films photoassisted electrolytic copper ion removal showeds that it is possible to enhance the activity of Anatase films by adding some Rutile exploiting the synergetic interaction between these two materials, achieve by its proper deposition.

Preparation of TiO2-Fullerene Composites and Their Photocatalytic Activity under Visible Light

The development of visible light-sensitive photocatalytic materials is being investigated. In this study, the anatase and rutile-C60composites were prepared by solution process. The characterization of the samples was conducted by using XRD, UV-vis, FT-IR, Raman, and TEM. The photocatalytic activity of the samples was evaluated by the decolorization of the methylene blue. From the results of the Raman, FT-IR, and XRD, the existence of the C60was confirmed in the samples. The C60was modified on the anatase or rutile particle as a cluster. The C60didn't have the photocatalytic activity under UV and visible light. The anatase and rutile-C60composites exhibited lower photocatalytic activity than the anatase and rutile under UV light. The anatase-C60exhibited also lower activity than the anatase under visible light. On the other hand, the rutile-C60exhibited higher activity than the rutile under visible light. It is considered that the photogenerated electrons can transfer from the C60to the rutile under visible light irradiation.

Supramolecular polymer micelles self-assembled from α-cyclodextrin and PLLA–PCL based copolymers

Accumulation of macrophages and neutrophil granulocytes in the lung are key events in the inflammatory response to inhaled particles. The present study aims at the time course of chemotaxis in vitro in response to the challenge of various biopersistent particles and its functional relation to the transcription of inflammatory mediators.NR8383 rat alveolar macrophages were challenged with particles of coarse quartz, barium sulfate, and nanosized silica for one, four, and 16 h and with coarse and nanosized titanium dioxide particles (rutile and anatase) for 16 h only. The cell supernatants were used to investigate the chemotaxis of unexposed NR8383 macrophages. The transcription of inflammatory mediators in cells exposed to quartz, silica, and barium sulfate was analyzed by quantitative real-time PCR.Challenge with quartz, silica, and rutile particles induced significant chemotaxis of unexposed NR8383 macrophages. Chemotaxis caused by quartz and silica was accompanied by an elevated transcription of CCL3, CCL4, CXCL1, CXCL3, and TNFα. Quartz exposure showed an earlier onset of both effects compared to the nanosized silica. The strength of this response roughly paralleled the cytotoxic effects. Barium sulfate and anatase did not induce chemotaxis and barium sulfate as well caused no elevated transcription.In conclusion, NR8383 macrophages respond to the challenge with inflammatory particles with the release of chemotactic compounds that act on unexposed macrophages. The kinetics of the response differs between the various particles.

Explaining the High Photocatalytic Activity of a Mixed Phase TiO2: A Combined Effect of O2 and Crystallinity

The synergistic effect between anatase and rutile TiO2 particles for organic photodegradation in an aerated aqueous suspension has been widely reported, ascribed to the charge transfer between two ...

Preparation and Photocatalytic Activity of TiO<sub>2</sub>/Fe<sub>2</sub>O<sub>3 </sub>Nanocomposite

TiO2/Fe2O3 nanocomposite was fabricated by a hydrolysis-precipitation approach, with TiCl4 as precursor and Fe2O3 as support. The crystal phase, diameter and morphology of the sample particle were characterized by X-ray diffraction, transmission electron microscope. The results show that the samples are composed of haematite and rutile. The morphology and diameter of rutile particle, coating effect and weight percentages of haematite and rutile are related to the preparing temperature and molar ratio of Fe/Ti. The photocatalytic activity of the prepared photocatalyst was estimated in an aqueous solution at ambient temperature of 303K. The results imply that the photocatalytic activity of the sample is higher than that of phase pure rutile, related to Fe/Ti molar ratio and its preparing temperature. These results can be attribute to the microsturcture of the sample. A synergistic effect exists between titania and haematite in the nanocomposite.

Microstructures and electrical properties of CaCu3Ti4O12thin films on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition

Abstract

On the selective growth of titania polymorphs in acidic aqueous medium

The influence of preparation conditions on the phase composition and morphology of titania was studied for the solids synthesized by hydrothermal treatment (HT) and peptizing of hydrous TiO 2 sols in acidic medium. Mutual influence of peptizing and of additive anions (SO 4 2−, Cl −) on the nature of obtained polymorphs was for the first time systematically studied and coherently explained. The solids were characterized by XRD, Raman spectroscopy, and transmission electron microscopy. It was found that peptizing step preceding HT and the presence of anions play a crucial role for the selective formation of TiO 2 anatase or rutile polymorphs. Low temperature peptizing leads to acicular rutile particles, whereas HT produces highly dispersed anatase. However if the HT was preceded by peptizing step, rutile was obtained in most cases. The influence of additives strongly depends on the moment of their introduction. Sulfate and chloride species can act as phase growth controllers, or as morphology modifiers. Sulfate hindered formation of rutile and favored anatase al low temperatures, but for already formed rutile seed, sulfate acted only as a shape controller. By contrast, chloride showed a strong tendency to promote rutile growth, whatever the conditions. A qualitative model was proposed explaining the effects observed, supported by ground state DFT and semi-empirical calculations of the aqueous Ti species.

Growth mode transition of atomic layer deposited Al 2O 3 on porous TiO 2 electrodes of dye-sensitized solar cells

This study investigates the growth behavior of atomic-layer-deposited (ALD) Al 2O 3 overlayers on porous TiO 2 electrodes, which comprise an anatase nanoparticle layer and a rutile particle layer, for optimizing dye-sensitized solar cells. The growth mode of the ALD Al 2O 3 overlayers changes from island growth to layer-by-layer growth during the first few ALD reaction cycles, and the growth mode transition is much more pronounced for the anatase electrode layer. The transition is likely a result of the reduction in the contractive lattice strain of the TiO 2 nanoparticles. The lattice strain in the hydroxylated TiO 2 nanoparticles is progressively reduced during the ALD Al 2O 3 deposition, resulting in the growth mode transition.

Human primary bronchial epithelial cells respond differently to titanium dioxide nanoparticles than the lung epithelial cell lines A549 and BEAS-2B

We have compared the cellular uptake and responses of five preparations of nanocrystalline titanium dioxide (TiO2) between normal human bronchial epithelial (NHBE) cells and epithelial cell lines (A549 and BEAS-2B). The P25 nanoparticles, containing both anatase and rutile modifications, induced reactive oxygen species (ROS) and secretion of the neutrophil chemoattractant IL-8 in all three cell types used. Pure anatase and rutile particles provoked differential IL-8 response in A549 and no response in BEAS-2B cells despite similar formation of ROS. The pure TiO2 modifications also provoked release of the inflammatory mediators: IL-6, G-CSF and VEGF, in NHBE cells but not in the two cell lines. We conclude that the responsiveness of lung epithelial cells is strongly dependent on both the physicochemical properties of TiO2 nanoparticles and the type of responder cells. The differential pro-inflammatory responsiveness of primary lung epithelial cells compared with immortalized cell lines should be considered in the assessment of adverse reactions to inhaled nanoparticles.

A Real Time Observation of Phase Transition of Anatase TiO2 Nanotubes into Rutile Particles by in situ Joule Heating Inside Transmission Electron Microscope

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Photovoltaic performance of dye sensitized solar cell based on rutile TiO 2 scaffold electrode prepared by a 2 step bi-layer process using molten salt matrices

Dye sensitized solar cells were made on TiO 2 scaffold anodes of rutile particles. These TiO 2 scaffold anodes were grown from rutile seeds by using a molten salt synthesis technique. Different thickness coatings of mixed amorphous titanium hydroxide and NaCl–KCl eutectic salt mixture on the rutile seeds were heat treated at different temperatures. The rutile whiskers of different aspect ratios were grown depending on the growth temperature. The best photovoltaic performances were obtained for the device made from the scaffold of 20–50 nm diameter and 0.5–1 μm length nanowhiskers obtained at 700 °C for 5 h of treatment.

Photocatalytic activity of predominantly rutile mixed phase Ag/TiV oxide nanoparticles under visible light irradiation

Nanoscale synthesis of silver sensitized titanium vanadium mixed-metal (Ag/TiV) oxides was done employing sol–gel technique. The physico–chemical properties of the material were examined using XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDAX (Energy Dispersive X-ray Spectroscopy), HR-TEM (High Resolution Transmission Electron Microscopy), XPS (X-ray Photoelectron Spectroscopy), UV-DRS and Photoluminescence analysis (PL). The results indicated the presence of predominantly rutile mixed phase particles of 20–30 nm grain size. Identically prepared TiV as well as Ag/TiV oxide catalyst showed enhanced and extended visible light absorption with an absorption upper limit, λ ≥ 550 nm. The visible light photocatalytic activity of Ag/TiV oxide showed an increase of about three and seven times compared to TiV oxide and Degussa P25 respectively, in the rate of degradation of phenol. The reason for the enhanced visible light activity of Ag/TiV oxide may be ascribed to elevated and extended absorption due to combined effect of dopant induced band gap reduction and visible light induced surface plasmon resonance of the Ag nanoparticles. The photocatalytic activity is complemented by localized charge traps and Ag assisted charge separation in the system as well.

Adsorption and Surface Complexation Study of L-DOPA on Rutile (α-TiO2) in NaCl Solutions

Dihydroxyphenylalanine (DOPA) and similar molecules are of considerable interest in studies of bioadhesion to minerals, solar cells involving titanium dioxide, and biomedical imaging. However, the extent and mechanisms of DOPA adsorption on oxides in salt solutions are unknown. We report measurements of DOPA adsorption on well-characterized rutile (α-TiO₂) particles over a range of pH, ionic strength, and surface coverage as well as a surface complexation model analysis establishing the stoichiometry, model surface speciation, and thermodynamic equilibrium constants, which permits predictions in more complex systems. DOPA forms two surface species on rutile, the proportions of which vary strongly with pH but weakly with ionic strength and surface loading. At pH < 4.5 a species involving four attachment points ("lying down") is important, whereas at pH > 4.5 a species involving only two attachment points via the phenolic oxygens ("standing up") predominates. Based on evidence of strong attachment of DOPA to titanium dioxide from single molecule AFM (Lee, H. et al., Proc. Natl. Acad. Sci.2006, 103, 12999-12003) and studies of catechol adsorption, one or more of the DOPA attachments for each species is inner-sphere, the others are likely to be H-bonds.

Temperature‐dependent grain growth and phase transformation in mixed anatase‐rutile nanocrystalline TiO2 films

AbstractNanocrystalline TiO2 films were prepared from colloidal suspensions using a mixture of anatase and rutile TiO2 particles. Their structure was examined by X‐ray diffraction (XRD). The as‐prepared specimens exhibit the presence of both anatase and rutile crystallites with average sizes of ∼30 and ∼50 nm, respectively, as determined from their characteristic diffraction peaks in XRD. Isochronal annealing of the films for 90 min in air at temperatures of up to 1270 K effected clear structural changes: between 470 and 870 K, the crystallite sizes do not change, with the crystallites remaining in their original phase. For annealing temperatures Ta ≥ 970 K the anatase and rutile grain sizes increase, while above ∼1170 K, the anatase phase disappears and only crystallites in the rutile phase of TiO2 are observed. Their size increases further with increasing annealing temperature and reaches ∼150 nm at 1270 K. Concurrently, the weight fraction of rutile changes from an initial value of ∼0.09 (for 470−870 K) to unity (above 1170 K). At Ta = 970 K, the increase of the duration of annealing from 90 to 360 min leads to a moderate increase of the crystallite size. The results indicate that the transformation of anatase particles is governed by the concurrent occurrence of interface and surface nucleation processes.

Binding of Human Serum Proteins to Titanium Dioxide Particles In Vitro

To determine the capacity of human serum proteins to bind to titanium dioxide (TiO(2)) particles of different polymorphs and sizes. TiO(2) particles were mixed with diluted human serum, purified human serum albumin (HSA) or purified human serum gamma-globulin (HGG) solutions. After incubation at 37°C for 1 h, the particles were sedimented by centrifugation, and proteins in the supernatant, as well as those bound to the particles, were analyzed. The total protein concentration in the supernatant was lowered by TiO(2), whereas the albumin/globulin ratio was elevated by the particles. Incubation with TiO(2) also lowered the immunoglobulin, pre-albumin, beta2-microglobulin, ceruloplasmin and retinol-binding protein levels, but not ferritin levels, in the supernatant. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), proteins in the supernatant, especially HGG, were observed to decrease, while those released from the particles (after adding 1% SDS and heating) increased, depending on the dose of TiO(2). Purified HGG and HSA were also bound to TiO(2), although the former appeared to have a higher affinity. All the proteins tested showed the highest binding potency to the amorphous particles (<50 nm) and the lowest to the rutile particles (<5,000 nm), while binding to anatase particles was intermediate. The affinity to the larger anatase was higher than that to smaller anatase particles in most cases. Human serum proteins, including the two major components, HSA and HGG, are bound by TiO(2) particles. The polymorph of the particles seems to be important for determining the binding capacity of the particles and it may affect distribution of the particles in the body.

Synthesis of TiO 2 scaffold by a 2 step bi-layer process using a molten salt synthesis technique

TiO 2 scaffolds of anisotropic rutile particles were grown from rutile seeds by using molten salt synthesis techniques. The rutile seeds were either in the form of a separate layer applied on a substrate or a sintered bulk pellet. Mixtures of amorphous titanium hydroxide and salt applied as coatings on the rutile seeds were heat treated. Depending on the morphology of the seed layer, heat treatment temperature, time and salt medium, rutile was grown with different morphologies and microstructures. For NaCl–KCl eutectic salt mixture and heat treatment at 700 °C for 5 h, nano-whiskers of 20–50 nm diameter and 0.5–1 μm length were obtained. For the NaCl salt sample treated at 850 ºC for 20 h, rutile platelets of 2–5 μm thick, 2–10 μm wide and 5–25 μm in length were produced. X-ray diffraction and Raman scattering were used to identify and characterize the rutile phase of the nanowhiskers.

Effect of particle size on the phase behavior of Li-intercalated TiO 2-rutile

With the aid of ab initio calculations, we compare the phase behavior upon lithiation of rutile particles of different sizes and morphologies. A rationale for the differences in their structural behavior is provided by combining concepts from Crystal Field Theory and semi-empirical concepts, such as bond length variation, minimal volume expansion, with accounts for the effects of diffusion and the anisotropy of the Li-distribution. It is shown that the phase behavior of spaghetti-like nano-particles differs from bulk rutile as a result of an extended single phase insertion domain and increased disorder of Li-ions. As Li-ions strive to minimize their repulsions by increasing their mutual separation a regular network of Li-ions is formed, being a precursor to the transformation of the rutile host lattice into spinel.

Single-step fabrication of phase-controllable nanocrystalline TiO2 films for enhanced photoelectrochemical water splitting and dye-sensitized solar cells

We introduce a single-step procedure for growing a phase-controllable bilayer-structured TiO2 film directly onto transparent conductive oxide glass by precipitation from hydrolysis of TiCl4 in acid solution containing sulfate ions. The obtained bilayer-structured film with anatase nanoparticles in the inner layer which provide high surface area, and an outer layer of larger rutile particles for incident light scattering. In both the water splitting and the dye-sensitized solar cells under AM 1.5 simulated solar light, the bilayer-structured film outperformed the single layer-structured films with either anatase or rutile TiO2 alone by at least 50%.

Synthesis and photocatalytic activity of small brookite particles by self-hydrolysis of TiOCl2

The preparation of brookite particles was tried by self-hydrolysis of TiOCl2 with HCl addition. When 0.1 M TiOCl2 solution was heated at 100°C by reflux method, the precipitate was obtained within 15 min and was identified as brookite and anatase. By addition of HCl, the starting time of precipitation was delayed and small brookite formed beside rutile large rod particles. These results suggest that deprotonation at the early stage of reaction was suppressed but crystal growth at the late stage was promoted because of an increase in the solubility of TiO2 sols.When the TiOCl2 solution was heated at 100°C for 24 h in autoclave, rutile large particles and brookite small particles formed separately. The small brookite particles could be separated by centrifugation. The photocatalytic activity of synthesized brookite particles was lower compared to commercial brookite particles. When hydrothermal treatment was carried out for synthesized brookite, the photocatalytic activity was enhanced. This was due to improvement of crystallinity of brookite.