Pure Anatase Nanoparticles Research Articles

One‐Step Synthesis of Sulfate‐Modified Titania Nanoparticles with Surface Acidic and Sustained Photocatalytic Properties via Solid‐State Thermolysis of Titanyl Sulfate

AbstractTitania nanoparticles surface‐functionalized with sulfate were prepared by thermal degradation of titanyl sulfate. At 600 °C pure anatase phase is obtained. X‐ray photoelectron spectroscopy (XPS) showed 1.4 at.% sulfur in the +6 oxidation state. At 700 °C anatase was still present, which is attributed to the presence of small amounts of stabilizing sulfate groups only detectable by high‐resolution XPS, segregating to the nanoparticle interfaces. Adsorption and photocatalytic degradation of acetaldehyde reactions were studied by in situ diffuse reflectance Fourier transform spectroscopy and 2D correlation spectroscopy, and compared with pure anatase nanoparticles. Aldol condensation of acetaldehyde and subsequent accumulation of crotonaldehyde was lower on sulfate‐modified titania. Butanoate was identified as an intermediate, which forms after dimerization and aldol condensation. Much more carboxylates and carbonates accumulated on pure anatase catalysts compared with sulfate‐modified anatase during photocatalysis. It is conjectured that surface acidic photocatalysts could be beneficial for achieving sustained activity for photodegradation of organic pollutants.

Semiconducting polypyrrole@TiO2 pure anatase nanoparticles for photodegradation of reactive red 120 azo dye

In the recent years, the development of new and efficient materials for photocatalytic processes has been of growing interest for applications in wastewater treatment. In this sense, TiCl4 stabilized with H2SO4 was precipitated with ammonium hydroxide in the presence of sodium dodecyl sulfate and calcined to obtain thermally stable TiO2 nanoparticles, which were subsequently coated with semiconducting polypyrrole (PPy) by chemical oxidation resulting in a composite of TiO2@PPy. TiO2 and TiO2@PPy composite were characterized by SEM, Raman, XRD, UV/Vis–NIR, FTIR and TGA. It was observed that TiO2 consisted of spherical nanoparticles with number-average particle diameter of 19.2 nm and polydispersity index in sizes of 1.2, whereas TiO2@PPy composite consisted of agglomerated spherical PPy nanoparticles of number-average diameter of 182.4 nm coating TiO2 nanoparticles. The calculated optical bandgap of TiO2 was 3.07 eV, and it was demonstrated by the Rietveld refinement method of the XRD spectrum and from the Raman analysis that synthesized TiO2 corresponds to highly pure rhombic anatase crystal structure. TiO2@PPy composite was tested in the photodegradation of the reactive red 120 azo dye in aqueous solutions under visible light irradiation. It was observed that photodegradation rate increased with decreasing the initial dye concentration and increasing the composite load. Almost 100% of dye removal was achieved after 45 min of reaction for 20 mg L−1 of initial dye concentration and 1.0 g L−1 of composite load.

Synthesis of Pure Brookite Nanorods in a Nonaqueous Growth Environment

Brookite TiO2 is the most difficult TiO2 polymorph to synthesize. The available methods in the literature to produce brookite nanostructures mostly use water-based techniques for the preparation of water-soluble Ti complexes first, followed by a hydrothermal growth of the brookite nanostructures. Besides its multi-step nature, achieving a single brookite phase and optimizing the aqueous growth environment are all issues to be hardly controlled. In this work, pure brookite TiO2 nanorods are synthesized using tetrabutyl titanate Ti(OBu)4 and Sodium Fluoride (NaF) as precursor materials in a simple non-aqueous one-pot solvothermal process. Alcoholysis of only Ti(OBu)4 in ethanol resulted in pure anatase nanoparticles, while the addition of NaF was essential to promote the growth of highly pure brookite nanorods. The phase purity is confirmed by X-Ray Diffraction, Raman Spectroscopy, and High-Resolution Transmission Electron Microscopy. The growth mechanism is explained according to the Ostwald’s step rule, where Na+ ions are anticipated to have a potential role in driving the growth process towards the brookite phase.

Firmness and bandgap engineered anatase TiO2 nanoparticles for enhanced visible light photocatalytic activity

Titanium dioxide is a standard semiconductor material plays a vital role in environmental and energy research. Anatase to rutile phase transformation in pure TiO2 nanoparticles usually occurs in the temperature range 600 °C–700 °C with it only absorbs UV light, owing to its large bandgap of 3.2 eV. Till date, researchers and industrialists have been trying to synthesize TiO2 nanoparticles with increased anatase phase stability with reducing the bandgap of pure anatase phase to the visible region, used dopant or H2O2 precursor modification, but the long time has taken photocatalytic activity under sunlight. Here, using a novel Photon Induce Method (PIM) has reported extending the anatase to a rutile transformation temperature, which in turn reflects on the stability of the material. PIM prepared oxygen-rich TiO2 nanoparticles exhibit enhanced temperature stable anatase phase, i.e. the sample remained as pure anatase phase even after calcinating at 1000 °C with a reduced bandgap of less than 2.91 eV, stretching towards the red region of the sunlight, whereas the standard Degussa P25-TiO2 and Others are reported to exist as 100% rutile at this temperature. By tuning the oxygen vacancy preparation conditions, we can reversibly improve oxygen-rich Titania via PIM. The absence of dopant or H2O2 of pure Titania anatase nanoparticles is high chemical reactivity has important implications for antibacterial, cancer cells kill, photocatalysis and solar energy conversion.

Enhanced photocatalytic removal of Cr(VI) over 0D/2D anatase/graphene and its synergism with organic pollutants under visible light irradiation

In this study, a novel anatase/graphene (0D/2D)-based composite photocatalyst is synthesized through a facile hydrothemal method using graphene oxide (GO), titanium sulfate (Ti(SO4)2) and hydrazine hydrate (N2H4·H2O) as precursors. The study reveals that the surface-dispersed anatase nanoparticles adhere well to the flake-like graphene. Compared with pure anatase nanoparticles, the anatase/graphene composite showed a significantly modified crystal structure in the crystallinity of the anatase phase and surface area. The involvement of graphene also dramatically enhanced the absorption of visible light and provided a shift in the absorption edge towards red wavelengths. From the analysis of the fluorescence spectra, it is demonstrated that the recombination dynamics of the photogenerated charge (electron-hole) pairs can be effectively inhibited by the compounded graphene and hence improve the efficiency of the charge carrier separation. The dramatically improved reduction of Cr(VI) is achieved through the visible light photocatalytic activity provided by the anatase/graphene composite. The rate of the reaction measured for the composite is 4.83-fold and 9.78-fold greater than that of the pure anatase under ultraviolet and visible light irradiation, respectively. Moreover, the synergism of the RhB degradation with the reduction of Cr(VI) also dramatically improves the latter. Additionally, we present an analysis of a potential alternate system for the improvement of photocatalytic activity.

Quantitative biokinetics of titanium dioxide nanoparticles after intravenous injection in rats: Part 1

Submicrometer TiO2 particles, including nanoparticulate fractions, are used in an increasing variety of consumer products, as food additives and also drug delivery applications are envisaged. Beyond exposure of occupational groups, this entails an exposure risk to the public. However, nanoparticle translocation from the organ of intake and potential accumulation in secondary organs are poorly understood and in many investigations excessive doses are applied. The present study investigates the biokinetics and clearance of a low single dose (typically 40–400 μg/kg BW) of 48V-radiolabeled, pure TiO2 anatase nanoparticles ([48V]TiO2NP) with a median aggregate/agglomerate size of 70 nm in aqueous suspension after intravenous (IV) injection into female Wistar rats. Biokinetics and clearance were followed from one-hour to 4-weeks. The use of radiolabeled nanoparticles allowed a quantitative [48V]TiO2NP balancing of all organs, tissues, carcass and excretions of each rat without having to account for chemical background levels possibly caused by dietary or environmental titanium exposure. Highest [48V]TiO2NP accumulations were found in liver (95.5%ID after one day), followed by spleen (2.5%), carcass (1%), skeleton (0.7%) and blood (0.4%). Detectable nanoparticle levels were found in all other organs. The [48V]TiO2NP content in blood decreased rapidly after 24 h while the distribution in other organs and tissues remained rather constant until day-28. The present biokinetics study is part 1 of a series of studies comparing biokinetics after three classical routes of intake (IV injection (part 1), ingestion (part 2), intratracheal instillation (part 3)) under identical laboratory conditions, in order to test the common hypothesis that IV-injection is a suitable predictor for the biokinetics fate of nanoparticles administered by different routes. This hypothesis is disproved by this series of studies.

Antimicrobial Activity of TiO2 Coatings Prepared by Direct Thermophoretic Deposition of Flame-Synthesized Nanoparticles

ABSTRACTThis study reports the development of a one-step method for the production of antimicrobial protective coatings for aluminum surfaces with titania nanoparticles. An aerosol flame synthesis system was used to produce monodisperse, ultra-fine TiO2 nanoparticles, which were directly deposited by thermophoresis onto plates of aluminum alloy by means of a rotating disc. Fuel-lean reactor conditions were used to synthesize pure anatase nanoparticles of 3.5 nm in diameter. Substrates were mounted onto the rotating disc that repetitively passes through the flame. Convection due to the rotational motion cooled the substrates, on which particles were deposited as films by thermophoresis. Such a system allowed to obtain submicron coatings of different thickness, by varying the total time of deposition. The antimicrobial activity of TiO2 coatings was tested against the Gram positive bacterium Staphylococcus aureus. To determine the inhibition of biofilms formation, microbes were plated on TiO2 coatings and a semi-quantitative colorimetric assay was performed using crystal violet. The tests showed that the TiO2 coating obtained with tdes=10 s inhibits up to 70-80% Staphylococcus aureus biofilm formation, and the inhibition of biofilms formation was confirmed by means of Scanning Electron Microscopy observation. Also, the antimicrobial properties of the coatings was enhanced by irradiating the samples in the UV region. The results of the present work are promising for using titania films as protective coatings for applications where an antimicrobial activity is required.

Nano-TiO2 coatings on aluminum surfaces by aerosol flame synthesis

Aluminum alloys are widely used in the aeronautic industry for their high mechanical properties; however, because they are very sensitive to corrosion, surface treatments are often required. TiO2 has excellent resistance to oxidation and it is often used to improve the corrosion resistance of aluminum surfaces. Several coating procedures have been proposed over the years, which are in some cases expensive in terms of production time and amount of deposited material. Moreover, they can damage aluminum alloys if thermal treatments are required. In this paper, a one-step method for the coating of aluminum surfaces with titania nanoparticles is presented. Narrowly sized, TiO2 nanoparticles are synthesized by flame aerosol and directly deposited by thermophoresis onto cold plates of aluminum AA2024. Submicron coatings of different thicknesses are obtained from two flame synthesis conditions by varying the total deposition time. A fuel-lean synthesis condition was used to produce 3.5nm pure anatase nanoparticles, while a mixture of rutile and anatase nanoparticles having 22nm diameter — rutile being the predominant phase —, was synthesized in a fuel-rich condition. Scanning electron microscopy is used to characterize morphology of titania films, while coating thickness is measured by confocal microscopy measurements. Electrochemical impedance spectroscopy is used to evaluate corrosion resistance of coated aluminum substrates. Results show an improvement of the electrochemical behavior of titania coated surfaces as compared to pristine aluminum surfaces. The best results are obtained by covering the substrates with 3.5nm anatase-phase nanoparticles and with lower deposition times, that assure a uniform surface coating.

Catalytic degradation of Acid Orange 7 by H2O2as promoted by either bare or V-loaded titania under UV light, in dark conditions, and after incubating the catalysts in ascorbic acid

AbstractPure and V-loaded mesoporous titania (with 2.5 wt-% V) were prepared by template-assisted synthesis and compared to commercial titania (Degussa P25), both as such and after vanadium loading. Mesoporous TiO2 occurred as pure anatase nanoparticles with higher surface area (SSA = 150 m2 g−1) than P25 (SSA = 56 m2 g−1).Degradation of the azo dye Acid Orange 7 by H2O2 was used as a test reaction: under UV light, no difference emerged between mesoporous TiO2 and P25, whereas in dark conditions, higher SSA of the mesoporous sample resulted in higher conversions. Under UV illumination, surface V5+ species inhibited photocatalytic activity, by forming inactive V4+ species. Similarly, in dark conditions, V5+ surface species reacted with H2O2, likely yielding ·O2H radicals and reducing to V4+. On the contrary, V-containing catalysts were very active after pretreatment with ascorbic acid, which reduced V5+ species to V3+species, the latter promoting very lively a Fenton-like reaction.

Morphological control of TiO2 anatase nanoparticles: What is the good surface property to obtain efficient photocatalysts?

The richness of titanium dioxide sol–gel syntheses described in literature provided a set of four different morphologies of pure anatase nanoparticles to study the impact of the exposed surfaces on the photocatalytic efficiency of the corresponding material. The selection of the experimental parameters such as the temperature, the heating method or organic additives allowed the synthesis of pure anatase materials with significantly different shapes. A thorough microscopic study of these particles gave the exposed crystallographic faces. The photocatalytic activity of the different materials was estimated following the degradation of the rhodamine B dye under UV-light and significantly different behaviors were observed. In the applied photodegradation conditions, two samples were shown to be more efficient than the reference photocatalyst P25. The rationalization of these results was done through the study of the oxide surface properties, using FT-IR spectroscopy with pyridine as a surface probe and the EPR analysis of photogenerated radicals under UV light. The most efficient photocatalyst for rhodamine B degradation was found to be the morphology presenting the stronger acidic surface sites.

Effect of nanostructured TiO₂ crystal phase on photoinduced apoptosis of breast cancer epithelial cells.

PurposeThe use of nanoparticles has seen exponential growth in the area of health care, due to the unique physicochemical properties of nanomaterials that make them desirable for medical applications. The aim of this study was to examine the effects of crystal phase-nanostructured titanium dioxide particles on bioactivity/cytotoxicity in breast cancer epithelial cells.Materials and methodsCultured Michigan Cancer Foundation (MCF)-7 and human breast adenocarcinoma (MDA-MB-468) breast cancer epithelial cells were exposed to ultraviolet A light (wavelength 350 nm) for 20 minutes in the presence of aqueous dispersions of two different nanostructured titanium dioxide (TiO2) crystal phases: anatase and an anatase–rutile mixture. Detailed characterization of each titanium dispersion was performed by dynamic light scattering. A 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) colorimetric assay was employed to estimate the percentage of viable cells after each treatment. Western blot analysis of protein expression and characterization, as well as a deoxyribonucleic acid (DNA)-laddering assay, were used to detect cell apoptosis.ResultsOur results documented that 100% anatase TiO2 nanoparticles (110–130 nm) exhibited significantly higher cytotoxicity in the highly malignant MDA-MB-468 cancer cells than anatase– rutile mixtures (75%/25%) with the same size. On the contrary, MCF-7 cells (characterized by low invasive properties) were not considerably affected. Exposure of MDA-MB-468 cells to pure anatase nanoparticles or anatase–rutile mixtures for 48 hours resulted in increased proapoptotic Bax expression, caspase-mediated poly(adenosine diphosphate ribose) polymerase (PARP) cleavage, DNA fragmentation, and programmed cell death/apoptosis.ConclusionThe obtained results indicated that pure anatase TiO2 nanoparticles exhibit superior cytotoxic effects compared to anatase–rutile mixtures of the same size. The molecular mechanism of TiO2 nanoparticle cytotoxicity involved increased Bax expression and caspase-mediated PARP inactivation, thus resulting in DNA fragmentation and cell apoptosis.

Anatase and brookite TiO2with various morphologies and their proposed building block

In this work, brookite TiO2 has been synthesized by a simple hydrothermal approach using sodium titanate as a precursor in the presence of a sodium fluoride aqueous solution. The ratio of brookite and anatase TiO2 can be tailored by the NaF concentration. In a concentrated NaF solution, high quality brookite TiO2 was acquired. Pure anatase nanoparticles were obtained in only deionized water. Moreover, the morphology and size of brookite TiO2 can be tailored by using various acid treated titanates which influence the stability of the building blocks and nucleation points of TiO2. Micro-sized flower-like brookite, submicro-sized urchin-like brookite and brookite nanorods with anatase nanoparticles were obtained. The micro-sized flower-like brookite remains the same shape and phase even at 800 °C, whereas obvious grains were formed on the matrix with brookite, rutile and anatase mixture phases at 900 °C. On the other hand, as the submicro-sized urchin-like brookite was heated, a rutile phase appeared at 750 °C and 100% grain-like rutile was obtained at 900 °C.

Controllable synthesis of TiO2 nanomaterials by assisting with l-cysteine and ethylenediamine

This paper reports a facile l-cysteine-assisted solvothermal synthesis of TiO2 nanomaterials using ethylenediamine (En) and distilled water as solvent. The influence of reaction time, temperature, l-cysteine and solvent was initially investigated. Results demonstrated the reaction temperature, l-cysteine and En significantly imposed impact on the phase and morphology of the particles. Amorphous nanosheets, mixed-crystal nanorods and pure anatase nanoparticles were controllably synthesized by varying reaction temperature. The formation of the amorphous nanosheets and mixed-crystal nanorods were directly affected by the presence of l-cysteine and En. And the presence of En distinctly affected the crystal phase of the products, which was rarely mentioned in other studies. Moreover, the photocatalytic activities of three typical samples were excellent. The possible formation mechanism of the sample was also discussed.

Preparation of highly photocatalytically active rutile titania nanorods decorated with anatase nanoparticles produced by a titanyl-oxalato complex solution

Rutile phase titania (TiO2) nanorods and anatase nanoparticles were successfully synthesized from a titanyl-oxalato complex solution prepared using titanium (IV) sulfate and oxalic acid by a hydrothermal process. The impact of various hydrothermal conditions on the formation, morphology, phase, and grain size of the TiO2 nanocrystals was investigated using fourier transformation infrared spectroscopy, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and nitrogen adsorption. The photocatalytic activities have been evaluated for the photo-decomposition of phenol under ultraviolet visible illumination. The results revealed that the TiO2 rutile nanorods decorated with anatase nanoparticles (with ~22% anatase) prepared at 160°C for 72h exhibit a higher photocatalytic activity than those pure anatase nanoparticles. This behavior was closely related to the better charge carrier separation in the cases of rutile–anatase mixtures. In addition, the possible growth mechanism and phase development of the rutile nanorods and anatase nanoparticles were illustrated.

Enhanced Photocatalytic Hydrogen Production with Synergistic Two-Phase Anatase/Brookite TiO2 Nanostructures

Highly crystalline pure brookite and two-phase anatase/brookite TiO2 nanostructures were synthesized via a simple hydrothermal method with titanium sulfide as the precursors in sodium hydroxide solutions. The control of the phase composition has been demonstrated via solution concentration and reaction time, and the phase transformation mechanism has been elucidated. Photocatalytic activities of the as-synthesized two-phase anatase/brookite TiO2, pure anatase nanoparticles, and pure brookite nanoplates were appraised via photocatalytic hydrogen evolution in aqueous methanol solution. Results have shown that the photocatalytic activity is higher for the two-phase anatase/brookite TiO2 and brookite nanoplates as compared to pure anatase nanoparticles despite the lower surface areas of the two-phase anatase/brookite TiO2 and brookite nanoplates. From the Mott–Schottky analysis, brookite phase is shown to have a more cathodic conduction band edge potential than anatase phase, which leads to more energetically...

Novel Preparation of Anatase TiO2@Reduced Graphene Oxide Hybrids for High-Performance Dye-Sensitized Solar Cells

An effective method was developed to prepare hybrid materials of TiO2 nanoparticles on reduced graphene oxide (RGO) sheets for application in solar cells. The morphology, size, and crystal phase of the TiO2 nanoparticles and TiO2@reduced graphene oxide (TiO2@RGO) hybrids were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis diffuse reflectance spectroscopy. A possible growth mechanism of TiO2@RGO hybrids is proposed based on observations of the TiO2 nanoparticles obtained from the hydrolysis process under different conditions. The effects of different reduced graphene oxide contents on the energy conversion efficiency of the dye-sensitized solar cells (DSSCs) based on J-V and incident photon-to-current conversion efficiency (IPCE) spectra are also discussed. DSSCs based on TiO2@RGO hybrid photoanodes with a graphene content of 1.6 wt % showed an overall light-to-electricity conversion efficiency of 7.68%, which is much higher than that of pure anatase nanoparticles (4.78%) accompanied by a short-circuit current density of 18.39 mA cm(2), an open-circuit voltage of 0.682 V, and a fill factor of 61.2%.

Enhancement of photocatalytic self-cleaning activity and antimicrobial properties of poly(ethylene terephthalate) fabrics

Fabrics with additional surface functions like self-cleaning, UV-protection or antimicrobial properties are highly desirable. TiO2 nanoparticles and composite nanoparticles consisting of AgI/AgCl/TiO2 were prepared. The particles were immobilized on PET fabric. The resulting materials showed proper photocatalytic self-cleaning activity measured by photochemical destruction of methylene blue and antimicrobial properties measured against Escherichia coli (E. coli). All properties of the PET bearing the AgI/AgCl/TiO2 nanocomposite particles are superior compared to the materials bearing the pure anatase nanoparticles.

Controlled fabrication of TiO2 rutile nanorod/anatase nanoparticle composite photoanodes for dye-sensitized solar cellapplication

We present a straightforward procedure to prepare composite photoanodes which consisted ofTiO2 rutile nanorods/anatase nanoparticles synthesized under hydrothermal conditions, with the ratioof rutile to anatase controlled simply by adjusting the volume of nitric acid. The as-preparedTiO2 composites exhibited high specific surface area, light-scattering effect,and good crystallinity. The dye-sensitized solar cells (DSCs) using theTiO2 composites showed higher short-circuit photocurrent and overall conversion efficiency than the DSCfrom pure-anatase nanoparticles. The highest conversion efficiency was achieved from the DSC basedon TiO2 nanocomposites with 24 wt% rutile nanorods, which was attributed to improved lightharvesting caused by the enhancement of specific surface area and scattering effect fromrutile nanorods.

Titania nano-photocatalysts synthesized by ultrasound and microwave methodologies: Application in depuration of water from 3-chloropyridine

The effect of aging the gel under ultrasonic (us) and microwave (mw) irradiation on the characteristics of the synthesized solids was studied. Sonication ensured the obtention of pure anatase nanoparticles in high crystalline state and generally led to obtain a high surface area and more active photocatalyst. Catalysts were characterized by a wide range of physical techniques (ICP-MS, N 2 isotherms, XRD, UV–vis and TEM). The total degradation of 3-chloropyridine was studied under titania-based photocatalysts, this degradation followed a zero-order kinetics respect to 3-chloropyridine. In our conditions, 100 ppm of 3-chloropyridine was degraded completely within ca. 8 h of UV-radiation (365 nm wavelength) on bare-titania systems. Some reactions intermediates were identified by SPME-GC–MS and a plausible mineralization route was suggested implying two parallel routes with hydroxylation and ring opening prior to or after the release of chloride ions. The modification of titania surface with metals (Fe, Pt, Pd) was detrimental for photocatalysis.

The Synthesis of Anatase TiO2 Nanoparticles by Solvothermal Method using Ionic Liquid as Additive

AbstractThe solvothermal reactions of Ti(OiPr)4 in alcohol using ionic liquid as additive were investigated. In the presence of [BMIM][Cl], [BMIM][Br], [BMIM][NTf2], [BMIM][SO3Me], [BMIM][SO4Me], or [BMIM][OTf] (BMIM = 1‐Butyl‐3‐methylimidazolium), pure anatase nanoparticles were obtained. The controlled hydrolysis of Ti(OiPr)4 in the presence of ionic liquids to form titanium oxo clusters plays a key role in the formation of anatase nanostructures, and ionic liquids can be repeatedly used to synthesise anatase nanoparticles. However, in the presence of [BMIM][PF6], [BMIM]2[Ti(OH)6] was obtained by an anion exchange reaction.