Characterization and photoactivity of TiO2 sols prepared with triethylamine

Using triethylamine as a surface protective agent, a transparent and pale yellowish TiO₂ sol had been prepared at 90 °C. This method was very different from the traditional methods, which produced titanium dioxide nanoparticles with anatase crystalline structure either at high acid condition or high temperature. X-ray diffraction (XRD) and transmission electron spectroscopy (TEM) demonstrated that the as-prepared TiO₂ sol nanoparticles with anatase crystalline structure were uniformly distributed, and the average size was 3 nm. X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra showed that triethylamine was adsorbed on TiO₂ sol particles surface. FTIR spectroscopy noted that TiO₂ sol particles had the similar spectra with Degussa P25. Photoactivity of the as-prepared TiO₂ sol was studied by investigating the photodegradation of methyl violet in hydrosol reaction system under visible light irradiation.     

Synthesis and characterization of copper ions surface-doped titanium dioxide nanotubes

Copper ions surface-doped titanium dioxide nanotubes were prepared via an assembly process based on the reactions between Cu(NH₂CH₂CH₂NH₂)₂(OH)₂ and hydroxide radicals on the surface of TiO₂ nanotubes, followed by the heat treatment in air at 723 K. The as-prepared samples were characterized with infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and fluorescence spectroscopy (FL). The photocatalytic activity of the copper ions surface-doped titanium dioxide nanotubes was investigated by photodegradation of Rhodamine B. The results showed that copper ions were successfully introduced onto the surface of TiO₂ nanotubes. And two kinds of copper species of Cu(I) and Cu(II) were found on TiO₂ surface. Copper ions act as electron trappers facilitating the separation of electrons and holes on the surface of TiO₂ nanotubes, which allows more efficiency for the photodegradation of Rhodamine B.     

Biocompatibility and bioactivity of PDLLA/TiO2 and PDLLA/TiO2/Bioglass® nanocomposites

Biocompatibility and bioactivity of polymer matrix composites containing titanium dioxide (TiO₂) nanoparticles were investigated. The solvent casting method was used to prepare poly (d,l-lactic acid) (PDLLA) films with 0 and 20 wt.% TiO₂ nanoparticles and with 20 wt.% TiO₂ mixed with 5 wt.% micrometre-sized (< 5 μm) Bioglass® particles. The samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy Dispersive X-ray (EDX) analyses. A Zygo® light interferometer was used to examine the surface roughness of the samples. The bioactivity and the surface reactivity of the materials were determined by investigating the formation of hydroxyapatite (HA) on the surface of samples upon immersion in simulated body fluid (SBF) for up to 28 days. Heterogeneous distributed HA crystals were found on composite films containing TiO₂ after 21 days exposure to SBF. Cell cytotoxicity and viability were determined by using live/dead and MTS assay on osteoblast-like MG-63 cells. The PDLLA films containing different concentrations of TiO₂ and Bioglass® particulate inclusions showed no effect on cell viability in live/dead assay after incubation period of 7 days. All three groups of samples demonstrated significant increase in relative metabolic activity in MTS assay after 7 days incubation (while a slower proliferation rate was obtained for cells on the PDLLA film containing both TiO₂ and Bioglass® compared to the Thermanox® control). The bioactive behaviour of the nanocomposites may make them attractive materials for fabrication of tissue engineering scaffolds.     

Characterization and in vitro evaluation of an acid resistant nanosized dental eggshell-titanium dioxide material

This paper reports on novel nanosized acid resistant material base on the modification of eggshell powder and titanium dioxide (TiO₂-EB) for enamel remineralization. The TiO₂-EB was prepared by ball milling eggshell powder and titanium dioxide. Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), and ImageJ were used to characterise TiO₂-EB. A computation model using Material Studio Software was used to explain the mechanism of TiO₂-EB interaction. In addition, the acid resistant of TiO₂-EB was evaluated by comparison using three commercial toothpaste. The mean pressure value (kPa/s) was measured using a pressure sensor. The FTIR, XRD analysis confirmed the surface modification of TiO₂-EB. The SEM image revealed that pure TiO₂ particles are spread on the surface of eggshell powder. The TEM image revealed spherical particles in TiO₂-EB. The ImageJ showed the average particle size of TiO₂-EB to be 13 nm. In addition, the commercial toothpastes doped with TiO₂-EB showed an improved acid resistant. The salient features of this study indicate that TiO₂-EB will effectively remineralized enamel lesions while offering better protective covering to the enamel.     

Sol-gel synthesis of silver/titanium dioxide (Ag/TiO2) core-shell nanowires for photocatalytic applications

Silver/titanium dioxide (Ag/TiO₂) core-shell nanowires were synthesized by direct coating of TiO₂ shells on the surface of silver nanowires (AgNWs) through a simple sol-gel process. TEM image and EDX elemental analysis had confirmed the presence of TiO₂ coating on the surface of AgNWs. The thickness of titanium dioxide coating was about 10 nm. These Ag/TiO₂ core-shell nanowires showed good photocatalytic activities in the decomposition of methylene blue as a model organic dye in aqueous solution under UV light irradiation. Ag/TiO₂ core-shell nanowires are potentially useful in photocatalytic applications.     

Dry etching properties of TiO2 thin films in O2/CF4/Ar plasma

In this work, the etching properties of titanium dioxide (TiO₂) thin film in additions of O₂ at CF₄/Ar plasma were investigated. The maximum etch rate of 179.4 nm/min and selectivity of TiO₂ of 0.6 were obtained at an O₂/CF₄/Ar (=3:16:4 sccm) gas mixing ratio. In addition, the etch rate and selectivity were measured as a function of the etching parameters, such as the RF power, DC-bias voltage, and process pressure. The efficient destruction of the oxide bonds by ion bombardment, which was produced from the chemical reaction of the etched TiO₂ thin film, was investigated by X-ray photoelectron spectroscopy. To determine the re-deposition of sputter products and reorganization of such residues on the surface, the surface roughness of TiO₂ thin film were examined using atomic force microscopy.     

TiO2/Si nanowires hybrid system for efficient photocatalytic degradation of organic dye

Herein, titanium dioxide (TiO₂)-coated vertically aligned silicon nanowires (SiNWs/TiO₂) were fabricated and evaluated for photocatalytic degradation of organic dyes. Aligned SiNWs arrays were prepared by facile metal-assisted chemical-etching process with varying the etching time that was followed by TiO₂ nanoparticles coating using sputtering technique. The TiO₂ film crystallized in pure anatase phase with an average crystalline size of 50 nm, as was elucidated with X-ray diffraction studies. SEM analysis showed nanowires with varying lengths from 2.5 to 13.5 µm and confirmed the homogenous surface decoration with TiO₂. The homogeneous distribution of TiO₂ nanoparticles on nanowires was co-evidenced with Energy-Dispersive X-ray spectroscopy (EDX) and Raman spectra analysis. The developed SiNWs/TiO₂ was exploited for photocatalytic degradation of methylene blue; the role of hydrogen peroxide was also elucidated. The highest photocatalytic efficiency of 96% was achieved for SiNWs/TiO₂ with optimum nanowire length of 3.5 μm. The developed photocatalyst was found to be almost stable even after 190 days (~?5 months) and could be used as reusable and easily removable photocatalysts. The current study highlighted the SiNWs/TiO₂/H₂O₂ system as excellent candidate for water remediation applications.

     

Controlled growth of TiO2 nanorods capped with carboxylate groups by the solvothermal process

A solvothermal method is described for preparing nanomaterials of titanium dioxide (TiO₂) while controlling the growth of rod-shaped nanomaterials. Titanium (IV) isopropoxide (TTIP) and butyl ether were chosen as the precursor and solvent, respectively. Oleic acid and decanoic acid were used as the surfactant. TiO₂ nanospherical particles and nano-rods were synthesized in mass quantities by adjusting the kind of surfactant, the concentration of the precursor, and the solvothermal reaction temperature. The synthesized TiO₂ nanospherical particles and nanorods were uniform and transparent in the toluene. The TiO₂ nanospherical particles were about 3.5 nm in size. The TiO₂ nanospherical particles and nanorods were of a highly crystalline anatase structure. The direction of growth of the TiO₂ nanorods was [001] and the band gap energy of the TiO₂ nanorods, evaluated by optical absorption, was 3.34 eV.     

Optical studies of ZSM-5 crystals infiltrated with TiO2

ZSM-5 crystals, of which granule size is about 120 µm along c axis, are employed as a good host material for TiO₂ loading. Optical microscopy photographs, X-ray powder diffraction spectra and surface area calculated from nitrogen adsorption data at − 196 °C have been carried out and show that the titanium dioxide clusters are infiltrating into the pores of ZSM-5. TiO₂/ZSM-5 host-guest material, regardless of whether being prepared by microwave and water bath heating, shows similar features except for the TiO₂ contents. The materials have a photoluminescence emission peak at 2.85 eV, which is ascribed to the band edge emission. A red shift was observed on the photoluminescence emission spectra when NH₃ adsorbed into the pores of TiO₂/ZSM-5 material.     

Synthesis and photoelectric property of poly (3-octylthiophene)/titanium dioxide nano-composite material

A conducting polymer composite, poly (3-octylthiophene)/titanium dioxide nano-composite was first synthesized through the ultrasonic method. The results from X-ray diffraction, X-ray photoelectron spectroscopy and infrared spectroscopy show that there is chemical interaction in the composite, which indicates that TiO₂ was successfully coated by poly (3-octylthiophene) molecules. The energy gap of the poly (3-octylthiophene)/titanium dioxide composite is lower to 0.65 eV; and it also shows that the optical performance of the new material is far superior than POT or TiO₂ separately, by Ultraviolet–visible spectra and fluorescence spectroscopy.     

The influence of surfactants on the roughness of titania sol–gel films

Substrate dipping in a composite sol–gel solution was used to prepare both smooth and rough thin films of titanium dioxide (TiO₂) on commercial fiberglass. The deposition of a composite film was done in a beaker using a solution of titanium (IV) isopropoxide as the sol–gel precursor and cetyltrimethyl ammonium bromide as the surfactant. In order to establish a correlation between experimental conditions and the titanium oxide produced, as well as the film quality, the calcined samples were characterized using Raman spectroscopy, UV–vis spectrophotometry, scanning electron microscopy and atomic force microscopy. One of the most important results is that a 61-nm TiO₂ film was obtained with a short immersion of fiberglass into the sol–gel without surfactant. In other cases, the deposited film consisted of a titanium precursor gel encapsulating micelles of surfactant. The gel films were converted to only the anatase phase by calcining them at 500 °C. The resulting films were crystalline and exhibited a uniform surface topography. In the present paper, it was found that the TiO₂ films prepared from the sol–gel with a surfactant showed a granular microstructure, and are composed of irregular particles between 1.5 and 3 μm. Smooth TiO₂ films could have useful optical and corrosion-protective properties and, on other hand, roughness on the TiO₂ films can enhance the inherent photocatalytic activity.     

Preparation of TiO2 particles and surface silanization modification for electronic ink

In this study, a sol–gel method has been adopted to synthesize titanium dioxide (TiO₂) particles. In order to improve the surface properties of the TiO₂ particles, vinyl triethoxysilane (VTES) has been used for their modification by silanization. The particles have been characterized by FTIR, scanning electron microscope, transmission electron microscopy, and X-ray diffraction (XRD) techniques. The results confirmed that VTES had been successfully grafted onto the surface of the TiO₂ particles. The TiO₂ particle size was not changed by the silanization modification, remaining at 100–200 nm. XRD results have shown the crystalline phase of the TiO₂ particles to be of the anatase type, and this was also unaffected by the VTES modification. Dispersion properties and suspension stability characterization of TiO₂ particles showed that VTES-modified TiO₂ particles have better dispersion stability and suspension stability in the dispersant of tetrachloroethylene than that of unmodified TiO₂ particles.     

Particle size determination of sunscreens formulated with various forms of titanium dioxide

Background: There has been some apprehension expressed in the scientific literature that nanometer-sized titanium dioxide (TiO₂) and other nanoparticles, if able to penetrate the skin, may cause cytotoxicity. In light of a lack of data regarding dermal penetration of titanium dioxide from sunscreen formulations, the Food and Drug Administration Center for Drug Evaluation and Research initiated a study in collaboration with the National Center for Toxicology Research using minipigs to determine whether nanoscale TiO₂ in sunscreen products can penetrate intact skin. Four sunscreen products were manufactured. Method: The particle size distribution of three TiO₂ raw materials, a sunscreen blank (no TiO₂) and three sunscreen formulations containing uncoated nanometer-sized TiO₂, coated nanometer-sized TiO₂ or sub-micron TiO₂ were analyzed using scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and X-ray diffraction (XRD) to determine whether the formulation process caused a change in the size distributions (e.g., agglomeration or deagglomeration) of the TiO₂. Results: SEM and XRD of the formulated sunscreens containing nanometer TiO₂ show the TiO₂ particles to have the same size as that observed for the raw materials. This suggests that the formulation process did not affect the size or shape of the TiO₂ particles. Conclusion: Because of the resolution limit of optical microscopy, nanoparticles could not be accurately sized using LSCM, which allows for detection but not sizing of the particles. LSCM allows observation of dispersion profiles throughout the sample; therefore, LSCM can be used to verify that results observed from SEM experiments are not solely surface effects.     

Preparation and properties of composite particles made by nano zinc oxide coated with titanium dioxide

In this paper, composite particles of nano zinc oxide coated with titanium dioxide were prepared and characterized by TEM, XRD, XPS and FT-IR, and the properties of the composite particles for photo catalysis and light absorption were studied. Tetrabutyl titanate (TBT) was hydrolyzed in an alcoholic suspension of nano zinc oxide with diethanolamine (DEA) as an additive, resulting in a film with a thickness of 20–30 nm being coated on the surface of nano zinc oxide, and the composite particles contained ZnTiO₃ after drying and calcination. Photocatalysis capabilities of the composite particles for the degradation of phenol in an aqueous solution were greatly improved as compared with nano zinc oxide particles before coating, with pure nano ZnO and nano TiO₂ with similar average sizes, or with the mixture of nano ZnO and TiO₂ with the similar composition as the composite particles. The light absorption scope of the composite particles was enlarged when compared to nano titanium dioxide with same average size.     

Synthesis and characterization of rice grains like Nitrogen-doped TiO2 nanostructures by electrospinning–photocatalysis

Rice grain-shaped Nitrogen-doped titanium dioxide (N–TiO₂) nano/mesostructures were fabricated through a combination of sol–gel and electrospinning methods. As-spun nanofibers were continuous and upon thermal treatment at 500° C for 1 h in air, the continuous fibers break into rice grain-shaped TiO₂ nanostructures of average diameter 50–80 nm. The nanostructures were characterized by spectroscopy, microscopy and powder X-ray diffraction. The rice grains consist of spherical particles of average diameter of ~ 18 nm and with N doping, their average diameters decrease from ~ 18 to ~ 12 nm. The presence of N in the TiO₂ lattice was confirmed by X-ray photoelectron spectroscopy (XPS). The band-gap of TiO₂ reduced from 3.19 eV to 2.83 eV upon increasing doping level of N from 0% to 5% (w/w), respectively. The N–TiO₂ rice grains showed an enhanced UV light-assisted photocatalysis compared to pure TiO₂ in the photodegradation of Alizarin Red S dye, an industrially important anthraquinone dye.     

Comparison of magnetic-nanometer titanium dioxide/ferriferous oxide (TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>) composite photocatalyst prepared by acid–sol and homogeneous precipitation methods

Novel magnetic-nanometer titanium dioxide/ferriferous oxide (TiO₂/Fe₃O₄) composite photocatalyst was prepared using acid–sol and homogenous precipitation methods. The photocatalyst particle was made of a Fe₃O₄ core covered with nanocrystal anatase TiO₂, without a high-temperature heat-treatment step. The catalyst has been characterized by X-ray diffraction, transmission electron microscopy, differential thermal analysis measurements, and ultraviolet spectrum. The results suggested that titania was mainly presented as anatase and Fe₃O₄ did not appear on the surface of the composite particles when the molar ratio of TiO₂/Fe₃O₄ increased to 20:1 in the acid–sol method, but 5:1 in the homogeneous precipitin method. The size of the crystal was ranged from 2.4 to 3.6 nm prepared by both methods. In the catalytic test, the composite particles, which were prepared by acid–sol, had higher catalytic activity than that prepared by homogenous precipitation method due to the size difference of the composite particles.     

Effect of NaHCO3 on synthesis of anatase TiO2 nanopowders by thermal processing of the precursor

Titanium dioxide (TiO₂) nanopowders were successfully prepared by thermal processing of the precursor of titanium hydroxide, urea and sodium acid carbonate (NaHCO₃). The products were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that NaHCO₃ has a certain effect on the average crystallite size and dispersity of TiO₂ nanopowders, at the same time other phases (Na₂SO₄ and Na₂CO₃) will be introduced. However, Na₂SO₄ has distinctive intercalation ability and catalytic activity. TiO₂ (anatase) powders can be prepared at ?600 °C for 2 h with addition of 2–10 wt% NaHCO₃, and the average crystallite size is 20.0–22.3 nm. The surface of the sample mainly consists of Ti, O, C, Na and S five species elements.     

Enhanced photovoltaic performance of quantum dot sensitized solar cells with Ag-doped TiO2 nanocrystalline thin films

Ag-doped titanium dioxide (TiO₂) nanocrystalline thin films have been prepared by the sol–gel dip coating method and used as photoanode to fabricate quantum dot sensitized solar cells. The X-ray diffraction studies reveal the formation of anatase phase without any impurity phase. The surface morphology studied using scanning electron microscope shows uniform distribution of particles. The optical band gap was found to be 3.5 and 3.4 eV for CdS quantum dot sensitized TiO₂ and CdS quantum dot sensitized Ag-doped TiO₂ thin film respectively. The Ag-doped TiO₂ based solar cell exhibited a power conversion efficiency of 1.48 % which is higher than that of TiO₂ (0.9 %).     

Structural,morphological and photocatalytic characterisations of Ag-coated anatase TiO2 fabricated by the sol–gel dip-coating method

This study reports on the synthesis, characterisation and environmental applications of immobilised Titanium dioxide (TiO₂) as photocatalyst. Nanostructured thin films have been prepared on glass substrates using a layer-by-layer dip-coating method. The crystalline phase and surface morphology of the thin films were investigated by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM), respectively. The XRD results show that the TiO₂ thin films crystallise in anatase phase and we have found that the thin films consist of titanium dioxide nanocrystals. SEM shows that the nanoparticles are sintered together to form a compact structure and TiO₂ particles coated with silver nanoclusters were observed. Ag-coated TiO₂ films demonstrated photocatalysis performance when irradiated, and the Ag carrier further showed an electron-scavenging ability to mitigate electron–hole pair recombination, which can improve the photocatalytic efficiency. With the oxidisation and electron-scavenging ability of Ag and the photocatalysis ability of TiO₂, Ag-coated TiO₂ can decolour methyl orange (MO) more than bare TiO₂. It is a new approach to form Ag-coated TiO₂ nanoparticles with a simple system and non-toxic materials. The high photocatalytic effect of Ag-coated TiO₂ nanoparticles on pollutant (MO) suggests that it may have a promising future for water and wastewater treatments.     

Nano-crystalline titanium dioxide formed by reactive plasma synthesis

Nano-crystalline titanium dioxide finds extensive applications in photocatalytic degradation of harmful organic compounds pollutants in air and water. Synthesis and characterization of nano-crystalline TiO₂ powder by reactive thermal plasma synthesis is presented here. Processing was carried out in a plasma reactor designed and developed in our laboratory. TiH₂ powder was used as the precursor, which was injected into the thermal plasma jet along with air as the reactive gas. TiH₂ particles, as they traverse the plasma jet, react with oxygen to form nano-sized TiO₂ powder. Nano-sized TiO₂ was also synthesized using Ti powder as the precursor. X-ray diffraction results showed complete conversion of the precursor into oxide. More than 75% of TiO₂ formed was present as anatase. TEM showed well-resolved nano-sized particles with more than 70% lying in the range of a few nanometer to 20 nm. The powder has been used to study photocatalytic degradation of dye.