Prepared TiO2 Samples Research Articles

Effects of TiO2 Nanoparticles Synthesized via Microwave Assistance on Adsorption and Photocatalytic Degradation of Ciprofloxacin.

In this study, the optimal microwave-assisted sol-gel synthesis parameters for achieving TiO2 nanoparticles with the highest specific surface area and photocatalytic activity were determined. Titanium isopropoxide was used as a precursor to prepare the sol (colloidal solution) of TiO2. Isopropanol was used as a solvent; acetylacetone was used as a complexation moderator; and nitric acid was used as a catalyst. Four samples of titanium dioxide were synthesized from the prepared colloidal solution in a microwave reactor at a temperature of 150 °C for 30 min and at a temperature of 200 °C for 10, 20, and 30 min. The phase composition of the TiO2 samples was determined by X-ray diffraction analysis (XRD) and Fourier-transform infrared spectroscopy (FTIR). Nitrogen adsorption/desorption isotherms were used to determine the specific surface area and pore size distributions using the Brunauer-Emmett-Teller (BET) method. The band-gap energy values of the TiO2 samples were determined by diffuse reflectance spectroscopy (DRS). The distribution of Ti and O in the TiO2 samples was determined by SEM-EDS analysis. The effects of adsorption and photocatalytic activity of the prepared TiO2 samples were evaluated by the degradation of ciprofloxacin (CIP) as an emerging organic pollutant (EOP) under UV-A light (365 nm). The results of the photocatalytic activity of the synthesized TiO2 nanoparticles were compared to the benchmark Degussa P25 TiO2. Kinetic parameters of adsorption and photocatalysis were determined and analyzed. It was found that crystalline TiO2 nanoparticles with the highest specific surface area, the lowest energy band gap, and the highest photocatalytic degradation were the samples synthesized at 200 °C for 10 min. The results indicate that CIP degradation by all TiO2 samples prepared at 200 °C show a synergistic effect of adsorption and photocatalytic degradation in the removal process.

Direct Photocatalytic Methane Oxidation to Formaldehyde by N Doping Co-Decorated Mixed Crystal TiO2.

In this paper, N-doped TiO2 mixed crystals are prepared via direct calcination of TiN for highly selective oxidation of CH4 to HCHO at room temperature. The structures of the prepared TiO2 samples are characterized to be N-doped TiO2 of anatase and rutile mixed crystals. The crystal structures of TiO2 samples are determined by XRD spectra and Raman spectra, while N doping is demonstrated by TEM mapping, ONH inorganic element analysis, and high-resolution XPS results. Significantly, the production rate of HCHO is as high as 23.5 mmol·g-1·h-1 with a selectivity over 90%. Mechanism studies reveal that H2O is the main oxygen source and acts through the formation of ·OH. DFT calculations indicate that the construction of a mixed crystal structure and N-doping modification mainly act by increasing the adsorption capacity of H2O. An efficient photocatalyst was prepared by us to convert CH4 to HCHO with high yield and selectivity, greatly promoting the development of the photocatalytic CH4 conversion study.

Electrochromic TiO2 films by a facile solvothermal process: Effect of ethanol content on growth and performance

The TiO2 films are directly prepared on FTO-coated substrates by a facile solvothermal method. The influence of ethanol content in precursor on the microstructure and electrochromic performance of TiO2 films is studied. The X-Ray diffraction result shows that the prepared TiO2 samples are crystalline. When the ethanol contents of 20% and 30%, the TiO2 films show (010) preferred orientation and fluffy porous structure. Analysis results of electrochromic performance indicate that the TiO2 film synthesized with the ethanol content of 20% exhibits the highest transmittance modulation (ΔT780 nm = 75.4%), the fastest switching times (bleaching time: 8.9 s, coloration time: 12.2 s) and the largest coloration efficiency (CE = 78 cm2/C). In addition, the cyclic voltammetry measurements confirm that the film synthesized with the ethanol content of 20% exhibits high cyclic stability (1000 cycles).

Characterization of Co2+- and Fe3+-Codoped TiO2 Nanomaterials for Photocatalytic Degradation of Organic Pollutants under Visible Light Irradiation

In this study, TiO2 nanomaterials were prepared using a solvothermal method and codoped with Co2+ and Fe3+ ions for the photocatalytic degradation of organic pollutants under visible light. The physicochemical properties of the obtained materials were studied by powder X-ray diffraction, field emission electron scanning microscopy, energy-dispersive X-ray spectroscopy, and nitrogen adsorption isotherms. Optical absorption was characterized by UV-vis absorption spectroscopy. The photocatalytic activities of the prepared materials were evaluated through methylene blue (MB) degradation under visible light irradiation. Results showed the excellent performance of MB degradation investigated on TiO2 samples codoped with Co2+ and Fe3+ in comparison with undoped and Co2+-doped TiO2 samples. The codoped TiO2 samples degraded 85%–90% of MB after 120 min, whereas all the prepared TiO2 samples were composed of pure anatase phase and had a spherical-like shape and mean crystalline size ranging from 6.2 nm to 7.8 determined by Scherrer’s equation. The optical absorption of the TiO2 codoped with Co2+ and Fe3+ was significantly enhanced toward the visible light region. The pseudo-second-order kinetic model fits well for the degradation of MB on as-prepared TiO2 codoped with Co2+ and Fe3+.

Effect of solvents on the morphology of TiO2 nanoparticles prepared by microwave method

In this study, titanium dioxide (TiO2) was synthesized using microwave method as rapid, uncostly and effective method. In order to study the effect of the solvent on the morphology of the prepared samples, two different solvents were used. The first solvent was ethylene glycol (EG, 99.8%) and the other was deionized water (DIW), while titanium isopropoxideTi[OCH(CH3)2]4 was used as TiO2 precursor. A commercial microwave oven was used with a power of 750 W and 5 minutes was selected as a duration of time preparation. The prepared specimens were annealed at 400 °C for 1 h. Diverse techniques were used in this study, such as X-Ray diffraction (XRD), field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (FESEM-EDX) and Fourier transforms infrared spectroscopy (FTIR) to study the structures and morphology of the prepared TiO2. Surface area was measured using Brunaner EmmettTeller (BET) technique. The XRD results revealed that the prepared samples were a pure TiO2 in anataseface.Noticeably, FESEM results show that the prepared TiO2 samples were nanorods-like shape with a length varied from 2 μm to 30 μm and a diameter varied from 500 nm to 6 μm when EG was used as a solvent. In contrast, spherical agglomerated nanoparticles with average diameters 20 nm were obtained when DIW was used as a solvent. The BET analysis revealed that the surface area of TiO2 nanorods was 151.413 m2/g, while it was 103.365 m2/gfor TiO2 nanoparticles.

Study on Effect of the Solvothermal Temperature on Synthesis of 3D Hierarchical TiO2 Nanoflower and Its Application as Photocatalyst in Degradation of Organic Pollutants in Wastewater

3D TiO2 hierarchical nanoflower was synthesized by template-free solvothermal alcoholysis of TiCl3 with the variation of reaction temperatures (130–200 °C). XRD, SEM, BET surface analysis, UV–VIS DR spectroscopy, FTIR analysis were performed to characterize the prepared TiO2 samples. Photocatalytic degradation of model organic pollutant such as methylene blue (MB) dye was investigated using all prepared samples under UV light illumination. Results show that reaction temperature directly affects the anatase phase content of TiO2 samples, crystal structures, crystalline size, particle size, surface area, pore structure, UV absorption capacity, and band gap of the synthesized samples. The sample prepared at reaction temperature 150 °C seems to be most efficient photocatalyst for degradation of MB with rate constant 0.0287 min−1 [~ 20.5 times higher than the sample prepared at 130 °C (0.0014 min−1) and 6.83 times higher than the sample prepared at 200 °C, (0.0042 min−1)]. Optimization of reaction temperature at 150 °C was performed by testing different properties of the synthesized TiO2 nanoflower such as its surface area, organized morphology, bimodal pore-size distribution, and porosity which were synthesized at different solvothermal temperatures (130–200 °C).

A simple and novel synthetic route to prepare anatase TiO2 nanopowders from natural ilmenite via the H3PO4/NH3 process

A simple and novel technique for the preparation of anatase TiO2 nanopowders using natural ilmenite (FeTiO3) as the starting material is reported. Digesting ilmenite with concentrated H3PO4 under refluxing conditions yields a white α-titanium bismonohydrogen orthophosphate monohydrate (TOP), Ti(HPO4)2·H2O, which can be easily isolated via gravity separation from unreacted ilmenite. The addition of ammonia to the separated TOP followed by calcination at 500°C completes the preparation of anatase TiO2. Calcination at temperatures above 800°C converts the anatase form of TiO2 to the stable rutile phase. The removal of iron from ilmenite during the commercial production of synthetic TiO2 is problematic and environmentally unfriendly. In the present study, the removal of iron was found to be markedly simple due to the high solubility of iron phosphate species in concentrated H3PO4 with the precipitation of TOP. The titanium content of the prepared samples on metal basis with silica and phosphorous as major impurities was over 90%. Prepared TiO2 samples were characterized using X-ray fluorescence, Fourier-transform infrared spectroscopy, Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, high-resolution transmission electron microscopy, and X-ray diffraction analyses. The photocatalytic potentials of the commercial and as-prepared TiO2 samples were assessed by the photodegradation of rhodamine B dye.

Base-free glycerol oxidation over N-TiO2 supported Au–Pt catalysts

N-Doped TiO2 materials were used as support for the bimetallic gold-platinum nanoparticles catalysts. Via the sol immobilization technique, the metal particle dimension varied during the immobilization on the different supports. The prepared TiO2 samples were characterized by X-ray diffraction (XRD), N2 physisorption (BET) and X-ray photoelectron spectroscopy (XPS), while the AuPt-TiO2 catalysts were characterized by transmission electron microscopy (TEM). The oxidation of glycerol by molecular oxygen in the aqueous phase over AuPt/N-TiO2 was investigated in a continuous upflow batch reactor under base-free conditions. The difference in the catalyst activities could be ascribed to the different support. The results revealed that N-doped TiO2 based catalyst support showed a higher activity in the oxidation of glycerol compared to the unfunctionalized one. The highest conversion (92% after 6 h) and the highest selectivity to glyceric acid (79.9%) were achieved using AuPt on TiO2 prepared with chitosan.

Effects of calcination temperature on organic functional groups of TiO2 and the adsorption performance of the TiO2 for methylene blue

ABSTRACTHerein, TiO2 was prepared by the hydrolysis method in critic acid (with both carboxyl and hydroxyl groups) solution firstly. And then, the as-prepared TiO2 was calcined at 50, 150, 250, 350, and 450°C, respectively, in order to investigate the effects of the calcination temperature on the physicochemical property and the adsorption performance of TiO2. The adsorption performance of the prepared TiO2 samples for cationic dye-Methylene Blue (MB) was also studied. The results indicated that high calcination temperature can destroy the organic moieties on the TiO2 samples and further influence the adsorption performance of TiO2 for the removal of cationic dye-MB.

Enhanced Solar Water Splitting Performance of 50-100 nm Pore Sized TiO2 Nanotubes

Herein, we report the fabrication of titanium dioxide nanotubes via anodization technique through with and without hydrofluoric acid . The impact of hydrofluoric acid followed by annealing effect on TiO2 nanotubes for the solar water splitting performance was examined. Prepared TiO2 samples exhibited a diameter of about 50 to 100 nm sized nanotubes and hierarchical structures and they subjected to annealing. Synthesis and annealing effects on chemical, physical and photoelectrochemical water splitting activity of TiO2 samples were scrutinized. The crystalline nature, structure and surface morphologies of prepared TiO2 photocatalysts were explored by X-ray diffraction, scanning electron microscope, and the oxidation states of both titanium and oxygen was determined by X-ray photoelectron spectroscopy. As a consequence, after annealing at 500 ºC, TiO2 thin films treated with hydrofluoric acid solution (HF-TiO2) were found to exhibit a remarkable photoelectrochemical performance than bare TiO2 nanotubes under UV light irradiation. Moreover, the mechanistic insights acquired in the current research would be beneficial to design a novel and highly efficient photocatalyst for solar water splitting systems.

Effect of the Preparation Method (Sol-Gel or Hydrothermal) and Conditions on the TiO₂ Properties and Activity for Propene Oxidation.

Since the two most commonly used methods for TiO2 preparation are sol-gel (SG) and hydrothermal (HT) synthesis, this study attempts to compare both methods in order to determine which one is the most suitable to prepare photocatalysts for propene oxidation. In addition, this work studies how the concentration of the HCl used for hydrolysis of the TiO2 precursor affects the properties of the obtained materials. Also, the effect of avoiding the post-synthesis heat-treatment in a selection of samples is investigated. The photocatalysts are characterized by XRD, N2 adsorption-desorption isotherms and UV-vis spectroscopy, and the study tries to correlate the properties with the photocatalytic performance of the prepared TiO2 samples in propene oxidation. TiO2 materials with high crystallinity, between 67% and 81%, and surface area (up to 134 m2/g) have been obtained both by SG and HT methods. In general, the surface area and pore volume of the TiO2-HT samples are larger than those of TiO2-SG ones. The TiO2-HT catalysts are, in general, more active than TiO2-SG materials or P25 in the photo-oxidation of propene. The effect of HCl presence during the TiO2 synthesis and of the post synthesis heat treatment are much more marked in the case of the SG materials.

Direct access to highly crystalline mesoporous nano TiO2 using sterically bulky organic acid templates

Sterically bulky monocarboxylic acid templates pivalic acid and phenoxyacetic acid are reported for the first time as organic templates in the sol-gel synthesis of TiO2. Mesoporous nanoparticulates of pure anatase phase and of well defined size were synthesized. The characterization of the materials prepared was done by various methods such as XRD, SEM, TEM, FTIR, UV-DRS, BET, etc. The prepared TiO2 samples were evaluated for the day light photodegradation of methylene blue by comparing with Degussa P25 and templates free synthesized TiO2 and were found to be more efficient.

Next generation of pure titania nanoparticles for enhanced solar-light photocatalytic activity

TiO2 nanoparticles are renowned for its photocatalytic degradation. Herein, Oxygen-rich TiO2 nanosphere and TiO2 nanorods have been prepared by photon induced method (PIM). This facial preparation method is cost effective and produce pure anatase phased TiO2 nanoparticles with high stability. The morphology of the prepared TiO2 samples for various preparation times have been analyzed using HRTEM and HRSEM. As the preparation time is increased, a morphological transformation from nanorods to nanospheres is witnessed. The possible reason behind this transformation has also been discussed. The nature of the samples have been investigated using XRD, FTIR, PL, XPS and UV–Vis spectroscopy. The PIM prepared sample for 8 days show pure anatase phase stability even at a higher calcination temperature of 800 °C. This is correlated with the oxygen richness of the sample. A clear discussion regarding this enhanced phase stability is also presented here. Also, the photocatalytic activity of both the samples have been investigated through the degradation of methylene blue dye. The degradation of methylene blue under sunlight by pure TiO2 nanosphere is quicker when compared with TiO2 nanorods and Degussa P25. The reason for the enhanced photodegradation activity of pure TiO2 nanospheres has also been discussed in detail.

Investigation of amino acids as templates for the sol–gel synthesis of mesoporous nano TiO2 for photocatalysis

TiO2 nanoparticulates of well-defined size were synthesized using amino acid templates employing sol–gel method. Eight different amino acids were studied. The samples were characterized by various methods such as X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area measurement, and transmission electron microscopy. Of the amino acids used, catalyst employing aspartic acid was found to have minimum particle size of 10.4 nm and maximum surface area of 95.3 m2/g. The catalytic activity of the prepared TiO2 samples was compared with Degussa-P25 catalyst for direct sunlight photodegradation of methylene blue and calmagite dyes. Catalyst prepared form branched amino acids, proline, valine, and aspartic acids, were found to give better results. Based on infrared spectroscopy studies, it is proposed that amino acids act as a surfactant by hydrogen bonding between the hydrogen of the ammonium ion and the surface hydroxyl group of the colloid.

Antibacterial Applications of Anatase TiO<SUB>2</SUB> Nanoparticle

Many methods have been used for the preparation of nanostructured metal oxides. Here we report the synthesis of TiO2 nanoparticles by facile hydrothermal process by varying the concentration of the precursor and reaction temperature while keeping the process time constant. Morphological, structural and optical studies were carried out by scanning electron microscopy equipped with energy dispersive spectroscopy, X-ray powder diffraction spectroscopy and VU-Vis-NIR spectroscopy. Morphological and compositional analysis reveal that the prepared nanoparticles are highly pure with an approximate average particle size 5-15nm. XRD studies showed their crystalline structure and the sizes around 5 nm, while the optical absorption studies in the photon wavelength range 300-600 nm reveal that the strong absorbance peak is positioned at around 3.5 eV nm whereas visible energy is almost transparent for the materials. Finally, the antibacterial effect of TiO2 nanoparticles has been studied. Plating technique was used to determine lowest concentration that prevent or inhibit growth of bacteria. This technique of TiO2 nanoparticle was used against most common organisms which cause wound infection including: MRSA, E. coli and Pseudomonas aeruginosa. Different concentrations of TiO2 nanoparticles were used 100 μg/ml, 200 μg/ml, 400 μg/ml, 600 μg/ml and 800 μg/ml. Inhibition of bacteria was different for prepared TiO2 samples due to different concentration of the precursors and synthesis temperature.

Effects of vanadium doping on microstructures and optical properties of TiO2

To improve the photocatalytic activity of titanium dioxide (TiO2), the vanadium (V) was selected to modify TiO2. Pure and V-doped TiO2 samples were first synthesized, then effects of the V doping on microstructures and optical properties of TiO2 were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible light diffuse reflectance spectra (UV–vis DRS). Results indicated that the prepared TiO2 samples only contained anatase phase. The V dopant was uniformly dispersed in TiO2 lattices, not affecting the crystal phase structures of TiO2. The crystallite sizes of TiO2 were decreased first and then increased with the increase in V dopant content within the diameter range from 12 to 16nm. The V dopant inhibited the increase in TiO2 crystallite size. Also, the dispersity of TiO2 nanoparticles was improved with the increase in V dopant content. The V doping brought more defects in TiO2 lattices to capture charge carriers, and to decrease the recombination of electron–hole pairs. Additionally, the prepared TiO2 included such elements as Ti, V and oxygen (O). V consisted of two chemical states of V4+ and V5+, which were served as trapping centers of photo-generated electrons to promote the photocatalytic oxidation process. Ti existed in the form of Ti4+, and O presented in the form of such chemical bonds as Ti-O, Ti-OH and Ti-O-V in V-doped TiO2. Finally, the optical absorption edges of V-doped TiO2 show obvious red shift. The optimal V dopant content is 1.0% for pure TiO2 sample. The V dopant could introduce the doping energy level and narrow the band gap of TiO2, extending the absorption spectral range of TiO2. The V doping was an effective method to improve optical absorption properties of TiO2 in visible light region.

Fabrication of phase and morphology controlled pure rutile and rutile/anatase TiO2 nanostructures in functional ionic liquid/water

In this paper, pure rutile and anatase-rutile TiO2 nanoparticles have been successfully synthesised via a green route by hydrolysis of titanium tetrachloride with room temperature acidic ionic liquid 3-methyl-1-(3-sulfonylpropyl) imidazolium trifluoromethanesulfonate [HO3S(CH2)3MIM][CF3SO3] in aqueous medium. The influence of pH of the solution by varying molar ratio of substrate and ionic liquid has been investigated in both sol⿿gel and hydrothermal synthesis of TiO2 with significant variation in phase, phase composition (ratio of rutile to anatase) and morphology as indicated by various structural analysis such as XRD, TEM, BET, Raman and UV⿿vis absorption spectroscopy. The results indicate formation of a bunch of aligned thin flaky nano-rods of TiO2 which look like nano-flowers with a crystal size of 3⿿5nm by sol⿿gel method, while in case of hydrothermal method well-defined rutile solid nanorods of TiO2 were formed with variable length in the range of 120⿿170nm and 20⿿24nm in width. The photocatalytic activity of the prepared TiO2 samples has been determined by the photodegradation of methyl orange dye (20ppm) under UV light. Best photocatalytic activity was exhibited by sample S-2 prepared via sol⿿gel method.

Characterisation of water-soluble TiO2 and its photocatalytic activity under visible light

Highly crystalline and highly specific surface area TiO2 nanocrystals were successfully prepared using a non-hydrolytic sol–gel method that involves the titanium tetrachloride (TiCl4) as the metal oxide precursor with n-butanol as the oxygen donor at a low temperature without subsequent thermal procedure. The prepared TiO2 samples were about 10 nm in diameter on the basis of characterisations with X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy. Evaluation of the photocatalytic activity of the synthesised TiO2 was performed based on decomposition of organic dye rhodamine B under artificial solar light. It turned out that the as-synthesised TiO2 exhibits higher photocatalytic activities in degradation rhodamine B than the famous commercial photocatalyst P25. This is mainly attributed to the synthesis of anatase TiO2 having a good water dispersion and high specific surface area, which can be widely used in various fields.

Natural dye sensitized TiO2 nanorods assembly of broccoli shape based solar cells

TiO2 nanorods based thin films with rutile phase have been synthesized using template free low temperature hydrothermal method. The scanning electron microscope images showed that the prepared TiO2 samples were made of TiO2 nanorods and the nanorods had arranged by itself to form a broccoli like shape. The X-ray diffraction studies revealed that the prepared TiO2 samples exhibit rutile phase. The grown TiO2 nanorods had been sensitized using the flowers of Sesbania (S) grandiflora, leaves of Camellia (C) sinensis and roots of Rubia (R) tinctorum. Dye sensitized solar cells had been fabricated using the natural dye sensitized TiO2 nanorods based thin film photoelectrode and the open circuit voltage and short circuit current density were found to lie in the range of 0.45–0.6V and 5.6–6.4mA/cm2 respectively. The photovoltaic performance of all the fabricated natural dye sensitized TiO2 solar cells indicate that natural dyes have the potential to be used as effective sensitizer in dye sensitized solar cells.

Deep and Shallow TiO2 Gap States on Cleaved Anatase Single Crystal (101) Surfaces, Nanocrystalline Anatase Films, and ALD Titania Ante and Post Annealing

Using photoelectron spectroscopy (PES), deep (around 1.2 eV below Fermi level) and shallow (around 0.2 eV below Fermi level) gap states are investigated in differently prepared TiO2 samples: In situ cleaved single anatase crystal TiO2 (101) surface, sintered slurry of nanocrystalline anatase, amorphous atomic layer deposited (ALD) titania, and nanocrystalline anatase transformed by annealing from ALD titania. Deep gap states are generally attributed to under-coordinated Ti atoms due to oxygen defects. The origin of shallow gap states is unclear. PES on in situ cleaved anatase TiO2 (101) surfaces show in part no or weak emission from deep, but always weak emission from shallow gap states. Amorphous ALD titania initially is free of gap states, but deep gap states are easily induced by exposure to synchrotron radiation, while shallow gap states do not form. Exposure to synchrotron radiation also induced deep gap states in in situ cleaved single crystal (101) surfaces and in the nanoporous anatase films, wher...