Pure Titania Research Articles

Synthesis of tin and molybdenum co-doped TiO2 nanotube arrays for the photoelectrocatalytic oxidation of phenol in aqueous solution

Tin and molybdenum co-doped titanium dioxide nanotube arrays was prepared by single-step anodization of titanium plate (Sn-Mo-TiO2 NTs/Ti electrode). The Sn-Mo-TiO2 NTs/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The length and inner diameter of nanotubes increased with the increase of anodization voltage. The influences of factors, such as anodization voltage, anodization time, concentrations of Sn4+ and Mo6+, and calcination temperature, on the preparation of the electrode were studied by chronoamperometry under simulated sunlight irradiation. The optical performance of Sn-Mo-TiO2 NTs/Ti electrode was tested by UV–vis spectrophotometer. Sn-Mo-TiO2 NTs/Ti electrode exhibited high adsorption in the visible region relative to pure titanium dioxide nanotube arrays. Additionally, the chronoamperometry test results highlighted that the doping of tin and molybdenum could enhance the photoelectrochemical performance of the electrode. The electrode exhibited good photoelectrocatalytic oxidation capacity on phenol at 0.5 V constant bias voltage. Applied bias voltage enhanced the photocatalytic efficiency of nanotube arrays via promoting the separation of photogenerated electron-hole pairs. A possible degradation process for phenol was proposed.

Synthesis and Characterisation of Mesoporous TiO2 Nanoparticles by Novel Surfactant Assisted Sol-gel Method for the Degradation of Organic Compounds

A sol-gel method was employed to synthesise pure titanium dioxide (TiO2) and surfactant assisted TiO2 nanoparticles (NPs). The effect of novel surfactant viz., Lauryl lactyl lactate on photocatalytic properties of TiO2 was studied. TiO2 NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-Vis Diffuse Reflectance spectra (DRS), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Thermo gravimetric analysis (TGA), and Brunauer – Emmet - Teller (BET) surface area. Anatase phase of TiO2 was confirmed by X-Ray diffraction pattern and the crystallite size was between 9–19 nm. Addition of surfactant improved the BET surface area, surface defects, while the agglomeration of particles was reduced. DRS results revealed that the addition of surfactant to TiO2 sol induced a red shift of the absorption edge which resulted in the reduction of band gap from 3.23 to 3.21 eV. These physicochemical properties of TiO2 NPs were correlated with photocatalytic degradation of phenol. About 92% of phenol degradation was observed for surfactant assisted TiO2 NPs (SA-TiO2). Salicylic acid and caffeine were also degraded using SA-TiO2 NPs.

Effects of S and Ta codoping on photocatalytic activity of rutile TiO2

In this study, pure titanium dioxide (TiO2), Ta-doped TiO2, S-doped TiO2, and Ta-S-codoped rutile TiO2 photocatalysts were prepared by a sol-gel method. To evaluate the properties of the synthesized samples, X-ray diffraction analysis (XRD) and X-ray photoelectron spectroscopy (XPS) were applied. XRD detection results showed that the samples contained rutile phase basically. Scanning electron microscope observation showed that the morphology of Ta-S-TiO2 was nearly spherical. Transmission electron microscope investigation indicated that Ta-S-TiO2 had a flower-shaped structure consisting of many nanorods. The measurement of Brunauer-Emmett-Teller (BET)-specific surface areas (SBET) showed that tantalum and sulfur codoping can effectively increase the SBET of TiO2. XPS results indicated that Ta was in the form of Ta5+ in the TiO2 structure. Finally, the photocatalytic activities of synthesized photocatalyst samples were measured for the degradation of methylene blue in ultraviolet and visible light irradiation. The results demonstrated that the Ta-S-codoped rutile TiO2 photocatalyst had better photocatalytic performance than pure rutile TiO2, Ta-doped rutile TiO2 and S-doped rutile TiO2 photocatalyst.

Titania nanotubes modified by a pyrolyzed metal-organic framework with zero valent iron centers as a photoanode with enhanced photoelectrochemical, photocatalytical activity and high capacitance

The paper discusses the synthesis, photoelectrochemical and electrochemical behaviour of titania nanotube arrays modified by a pyrolyzed metal-organic framework (MOF). A poly(3,4–ethylenedioxyphene) (PEDOT) matrix with an embedded inorganic network of iron hexacyanoferrate (BP) covering TiO2 nanotubes (TNT) is used as a MOF for the further sintering procedure, resulting in a novel, thin film of carbonaceous wrap supported Fe catalytic centers: TNT@C:Fe. UV–Vis and Raman spectroscopies were utilized to characterize the absorbance capability and the crystalline phase of titania, respectively. XPS was used for identification of the valence stage of iron Fe(0), Fe(II), Fe(III) in the shell part of the novel composite TNT@C:Fe. The electrochemical performance of the modified nanotubular TiO2 electrodes has been monitored by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge cycles in an aqueous electrolyte. TNT@C:Fe exhibited the capacitance of 9.1 mF cm−2 even after 5000 cycles, being much higher than pure titania (2.1 mF cm−2). The photocurrent density reached 304 μA cm−2 for TNT@C:Fe, whereas only 32 μAcm−2 was registered for pure titania nanotubes under simulated solar light illumination at a potential of +0.5 V. An improved decolorization rate of methylene blue in water confirms enhanced photoactivity of TNT@C:Fe in comparison with pristine titania nanotubes.

Effect of Substrates on Structural Properties of Pure Anatase Phase Titanium Dioxide Thin Films Prepared by Mist Chemical Vapor Deposition

Mist chemical vapor deposition method was used to synthesize pure anatase phase titanium dioxide thin films on glass, quartz glass, gallium doped zinc oxide film and p-type silicon substrates. The effects of substrates on the structural and optical properties of TiO2 thin films were investigated. TiO2 films deposited on all substrates had the same preferred growth along (101) orientation which crystallize in the anatase phase. The films grown on glass and quartz glass showed better crystallinity than those grown on gallium doped zinc oxide film and p-type silicon. From the morphological results, uniform TiO2 films with roughness below 10 nm were obtained on all substrates. The transmittance of obtained TiO2 films on transparent substrates was greater than 75% in the visible region.

Studies on optical and electrical properties of green synthesized TiO2@Ag core-shell nanocomposite material

Newly adopted green approach has been used to synthesize pure titanium dioxide (TiO2) nanoparticles (NPs) and silver deposited titanium dioxide (TiO2@Ag) core–shell nanocomposite (CSNC) from Nigella Sativa (black cumin) seed extract for the first time. The phytochemicals available in Nigella Sativa (NS) seed extract acts as reducing agent in the formation of nanoparticles as well as nanocomposite. The morphology, crystal structure, particle size and phase composition of green synthesized TiO2 NPs and TiO2@Ag CSNC are investigated by High Resolution Transmission Electron Microscopy (HRTEM), Field Emission Scanning Electron Microscopy (FESEM), Powder x-ray diffraction (PXRD), FT–Raman and Fourier Transform Infrared spectroscopy (FT-IR). The red shift in (from 333 nm to 342 nm) UV–Vis spectrum confirmed the deposition of Ag on TiO2. The reduced intensity peaks of Photoluminescence spectra (PL) also indicate the deposition of Ag on TiO2. Further the electrical properties of pure TiO2 and TiO2@Ag CSNC have studied by dielectric studies and ac conductivity measurements. The dielectric constant and the dielectric loss of TiO2@Ag CSNC are better than pure TiO2. From these improved results, the green synthesized TiO2@Ag CSNC from NS seed extract is may be a suitable material for device fabrication in the visible region.

Light‐emitting Diode‐assisted Determination of 2‐(1,1‐Dimethylethyl)‐1,4‐Benzenediol in Cosmetic Samples Exploiting TiO2 Sensitized with Lithium 7,7′,8,8′‐Tetracyanoquinodimethanide

AbstractThis paper reports a novel analytical device for the determination of 2‐(1,1‐dimethylethyl)‐1,4‐benzenediol antioxidant (TBHQ) in cosmetic samples exploiting a photoelectrochemical sensor based on titanium dioxide nanoparticles sensitized with lithium 7,7′,8,8′‐tetracyanoquinodimethanide on indium tin oxide electrode. The proposed photoelectrochemical sensor possesses the capacity of harvesting light energy from a commercial light‐emitting diode (LED) lamp for the determination of TBHQ molecules. The photoelectrochemical sensor presented photocurrent response to antioxidant about 2‐fold higher than pure titanium dioxide. The sensor shows high photocurrent response to TBHQ antioxidant in comparison to photocurrent response to 2,3‐t‐butyl‐4‐hydroxyanisole and 2,6‐Di‐tert‐butyl‐4‐methylphenol, indicating selectivity to TBHQ. Under optimized experimental conditions, the photoelectrochemical sensor presents two linear ranges of response for the analyte, the former from 0.6 to 200 μmol L−1, and the latter from 200 to 5000 μmol L−1. A low limit of detection of 0.17 μmol L−1 was obtained for the proposed photoelectrochemical sensor. The sensor was successfully employed to the analysis of cosmetic samples, with recovery values between 96 % and 98 %.

A multifaceted coating on titanium dictates osteoimmunomodulation and osteo/angio-genesis towards ameliorative osseointegration

A multifaceted coating for hard tissue implants, with favorable osteogenesis, angiogenesis, and osteoimmunomodulation abilities, would be of great value since it could improve osseointegration and alleviate prosthesis loosening. However, to date there are few coatings that fully satisfy these criteria. Herein we describe a microporous TiO2 coating decorated with hydroxyapatite (HA) nanoparticles that is generated by micro-arc oxidation of pure titanium (Ti) and followed annealing. By altering the annealing temperature, it is possible to simultaneously tune the coating's physical (morphology and wettability) and chemical (composites and crystallinity) properties. A coating produced with micro-arc oxidization (MAO) with an annealing temperature of 650 °C (MAO-650) exhibits numerous favorable physicochemical properties, such as hybrid micro-nano morphology, superhydrophilicity, and highly crystalline HA nanoparticles. In vitro experiments reveal that the MAO-650 coating not only supports proliferation and differentiation of both osteoblasts and endothelial cells, but also inhibits the inflammatory response of macrophages and enables a favorable osteoimmunomodulation to facilitate osteo/angio-genesis. In vivo evaluation mirrors these results, and shows that the MAO-650 coating results in ameliorative osseointegration when compared with the pristine MAO coating. These data highlight the profound effect of surface physicochemical properties on the regulation of osteo/angio-genesis and osteoimmunomodulation in the enhancement of osseointegration.

Development of SiO2@TiO2 core-shell nanospheres for catalytic applications

Silica-titania core-shell nanospheres, CSNp, were prepared via a simple and environmentally friendly two step route. First, silica cores were prepared through the hydrolysis-condensation reaction of silicic acid in the presence of hyperbranched poly(ethylene)imine (HBPEI) followed by repeating washing, centrifugation and, finally, calcination steps. To create the core-shell structure, various amounts of titanium isopropoxide were added to the cores and after that a HBPEI-water solution was added to hydrolyze the titanium precursor. Washing with ethanol and heat treatment followed. The optimization of processing parameters led to well-developed core-shell structures bearing a homogeneous nanocrystalline anatase coating over each silica core. The photocatalytic activity for NO was examined in a continuous flux photocatalytic reactor under real environmental conditions. The results revealed a very potent photocatalyst as the degradation percentage reached 84.27% for the core-shell material compared to the 82% of pure titania with the photodecomposition rates measured at 0.62 and 0.55 μg·m−2·s−1, respectively. In addition, catalytic activities of the CSNp and pure titania were investigated by monitoring the reduction of 4-nitrophenol to 4-aminophenol by an excess of NaBH4. Both materials exhibited excellent catalytic activity (100%), making the core-shell material a promising alternative catalyst to pure titania for various applications.

Effect of Substrates on Structural Properties of Pure Anatase Phase Titanium Dioxide Thin Films Prepared by Mist Chemical Vapor Deposition

The mist chemical vapor deposition method was used to synthesize pure anatase phase titanium dioxide thin films on quartz glass, glass, gallium oxide doped zinc oxide film and p-type silicon wafer substrates. The effects of substrates on the structural and optical properties of titanium dioxide thin films were investigated. Titanium dioxide films deposited on all substrates were anatase phase and showed the same dominant (101) growth orientation. The crystallinity of titanium dioxide films grown on different substrates increased in an order of glass, quartz glass, p-type silicon and gallium oxide doped zinc oxide. The titanium dioxide thin film deposited on p-type silicon showed the highest percentage of exposed {001} facets. The morphological results showed that the titanium dioxide films with good uniformity were obtained on all of the substrates. The surface area of titanium dioxide films deposited on p-type silicon substrate was larger than that of titanium dioxide films deposited on quartz glass, glass and gallium oxide doped zinc oxide substrates. The transmittance of obtained titanium dioxide films on transparent substrates was greater than 75% in visible region. The obtained pure anatase phase titanium dioxide thin film on p-type silicon is expected to be applicable to thin film gas sensors.

Преобразование солнечного света в ячейках с сенсибилизированным красителем на основе модифицированных кобальтом и иттрием нанотрубок TiO-=SUB=-2-=/SUB=-

AbstractThe solar-energy conversion in eosin-sensitized solar cells based on cobalt and yttrium modified TiO2 nanotubes has been studied.It is established that the doping with metal ions shifts the absorption edge for Co and Y doped titanium dioxide samples to longer and shorter wavelengths, respectively. The efficiency of solar energy conversion depends on the wide bandgap of the semiconductor anode and reaches a maximum (4.4%) for yttrium-doped TiO_2 in comparison to that (4.1%) for pure titanium dioxide.

Cobalt and Yttrium Modified TiO2 Nanotubes Based Dye-Sensitized Solar Cells for Solar-Energy Conversion

The solar-energy conversion in eosin-sensitized solar cells based on cobalt and yttrium modified TiO2 nanotubes has been studied.It is established that the doping with metal ions shifts the absorption edge for Co and Y doped titanium dioxide samples to longer and shorter wavelengths, respectively. The efficiency of solar energy conversion depends on the wide bandgap of the semiconductor anode and reaches a maximum (4.4%) for yttrium-doped TiO2 in comparison to that (4.1%) for pure titanium dioxide.

Photocatalytic Activity of Graphene – Titania Nanocomposite

In the past few years, carbon-based semiconductor nanocomposites have attracted great attention due to their unique combinations of chemical and physical properties. Incessant research interest has been devoted on preparing graphene-based TiO2 nanocomposites for photocatalytic application. The present study aims to examine the photocatalytic activity of graphene-titania nanocomposite prepared via hydrothermal method. For a comparison, the photocatalytic activity of pure titania was also investigated. The prepared systems are well characterized using XRD analysis, FTIR spectroscopy, UV-VIS diffuse reflectance spectroscopy, Transmission Electron Microscopy, Photoluminescense study and Surface area analysis by BET method. The Photocatalytic activity of the composite was studied by measuring the degradation of aqueous solution of Crystal Violet (CV) dye under UV and Visible light. Modification with graphene has commendably increased the photocatalytic activity of titania.

In English

The simple and fast route of the synthesis of platinum ions doped titania thin films is designed where platinum(II) acetylacetonate is used as a perspective doping agent due to the possibility of platinum incorporation in the form of the different valence states. Additionally, the multilayered films showing the varied properties are obtained. The increase in Pt content as well as the number of layers leads to the higher absorbance and the band edge shift to the red part of the spectrum. The indirect electronic transition is suggested and the calculated band gap values are depended on the film compositions as well as the number of layers. The significant decrease in the band gap value of titania is noted for 0.5 % Pt/TiO 2 films. Pure titania and doped titania films contain anatase phase only with the average crystallite size near 14 nm. The conversion percentage of photocatalytic dichromate ions reduction is increased in the presence of three-layered 0.5 % Pt/TiO 2 films under both UV and visible light. The activity of three-layered films is higher compare to the single layered samples. The film contained 0.1 % Pt exhibited the similar activity to titania one.

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.

Acidity in Titania–Alumina Mixed Metal Oxides

Titania–alumina mixed oxides were prepared with varying titania content. The catalysts contained sulfate which was introduced via titanyl sulfate used as precursor during the synthesis. Samples were characterized by IR spectroscopy of adsorbed pyridine to determine Lewis and Bronsted acidity. At titania loadings below about 5 wt% no protonation of pyridine was detected by IR spectroscopy. However, 2-methyl-2-pentene isomerization indicated an increase in medium strength acidity in these samples relative to pure alumina and titania as inferred from an increased methyl shift activity. IR spectroscopy revealed the generation of fourfold coordinated Ti4+ sites and mildly acidic Ti–OH groups that may be responsible for the enhanced olefin isomerization reactivity of the mixed oxides. Addition of small amounts of titania also increased the concentration of the type Ia Al–OH group on the alumina surface characterized by an IR band at 3771 cm−1. At titania loadings of about 8 wt% and above Bronsted acidity was generated by sulfate groups as detected by the protonation of pyridine. Deposition of 0.3 wt% Pt on the titania–alumina mixed oxides generated finely dispersed Pt as measured by H2 chemisorption and TEM. The benzene hydrogenation activity on the Pt–TiO2–Al2O3 catalysts showed a maximum for the sample containing about 1 wt% titania and correlated with the relative abundance of the type Ia Al–OH groups on the alumina surface.

Study on cytotoxicity and photocatalytic properties of different titania/hydroxyapatite nanocomposites prepared with a combination of sol–gel and precipitation methods

In the present study different titania/hydroxyapatite nanocomposites were successfully synthesized via a combination of sol–gel and precipitation methods. Titanium-tetra-isopropoxide, 1-propanol, calcium nitrate tetra-hydrate and orthophosphoric acid were the starting materials. In order to characterize samples, several techniques such as XRD, Raman spectroscopy, FE-SEM, and BET–BJH were used. The photocatalytic activity of nanocomposites was investigated by photodegradation of 10 mg L−1 methylene blue aqueous solution under UV irradiation for 120 min. The dye adsorption of titania in darkness was enhanced from 2.5 to 11.6% for 40 wt% titania/hydroxyapatite nanocomposite. The best photocatalytic efficiency was obtained for 50 wt% titania/hydoxyapatite nanocomposite (90.5%), and the reaction rate constant increased from 0.0186 min−1 for pure titania to 0.0213 min−1 for 50 wt% titania/hydroxyapatite nanocomposite. The improvement in photoactivity of nanocomposite samples is due to high adsorption of dye molecules on hydroxyapatite surfaces and less agglomeration of titania nanopoarticles, for which the last is in accordance with FE-SEM and BET results. The toxic potentials of TiO2 and 50 wt% titania/hydroxyapatite nanocomposite on human normal cell lines were also examined, and the results showed their insignificant effects on HUVEC proliferation.

Synthesis and characterization of silver-titania nanocomposites prepared by electrochemical method with enhanced photocatalytic characteristics, antifungal and antimicrobial activity

The paper deals with the synthesis of silver-titania (Ag-TiO2) nanocomposites with enhanced photocatalytic, antifungal and antimicrobial characteristics. Ag nanoparticles have been electrochemically deposited on the commercially available nano-TiO2 powders involving the so-called “sacrificial anode” technique. The obtained nanocomposites were characterized by X-ray diffraction, XPS and Raman spectroscopy to get information on their composition and structure. Particle size distribution and stability of Ag-TiO2 based colloidal solutions have been determined from dynamic light scattering and zeta potential measurements. The recorded UV–vis diffuse reflectance spectra evidenced the presence of an absorption band located in the range of 475–525nm and the presence of a tail as well, suggesting a better photocatalytic activity. The photoreactivity of the synthesized Ag-TiO2 nanocomposite as well as the influence of Ag content were evaluated for the degradation of Orange II dye under UV irradiation (λ=365nm). The heterogeneous photocatalytic degradation rate follows pseudo first order kinetics. Antifungal and antimicrobial efficacy evaluation showed that the synthesized Ag-TiO2 nanocomposites are significantly more active than pure titania.

Enhanced durability of Pt electrocatalyst with tantalum doped titania as catalyst support

The performance and durability of PEMFCs highly depend on the catalyst support material. Traditionally, carbon is being used as support but its susceptibility to corrosion makes it less favorable for fuel cell applications. The weak interaction between PtC leads to the non-uniform distribution of platinum nanoparticles over the surface of support and poor durability, which in turn lowers the overall performance of PEMFCs. In order to introduce a robust support, which is more stable and durable as compared to the carbon, tantalum doped titania nanoparticles are synthesized via modified sol-gel method and investigated as a catalyst support for Pt electrocatalysts. The optimum calcination temperature for doped titania preparation is found to be 800 °C. The support is characterized through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICPOES) and transmission electron microscopy (TEM). Electrochemical performance shows that tantalum doped titania has much improved electrical conductivity than that of pure titania. Furthermore, Pt/TaTiO2 exhibits higher ECSA retention and comparable ORR activity as compared to the Pt/C, indicating the desired durability.

Photocatalytic degradation of organic pollutant aldicarb by non-metal-doped nanotitania: synthesis and characterization.

The current study focused on pollution control by titania through photocatalytic degradation of aldicarb pesticide in aqueous medium. Titania, which is an efficient photocatalyst, can bring about degradation of aqueous organic pollutants under UV and visible light irradiation. Here, we prepared titania by sol-gel method from titanium tetraisopropoxide and doped non-metals like N and S from sources such as urea and thiourea, respectively. The prepared catalyst was characterized by XRD, UV-Vis.DRS, TEM, XPS, etc. Photocatalytic activity of the catalyst was evaluated from extend of degradation of aldicarb pesticide by measuring its concentration with the help of HPLC. It was found that the modified catalyst showed better photocatalytic degradation than pure titania in visible light.