Conventional Titania Research Articles

Cooperative and fully reversible color switching activation in hybrid graphene decorated nanocages and copper-TiO2 nanoparticles

Nanostructured systems showing reversible color switching are envisaged to play a significant role in photo-switches, photo-optical sensors, smart windows, displays, optical storage memories. Most of the materials exhibiting reversible color switching are organic molecules. However, their UV-light activation, low thermal and chemical stability, as well as harmful synthesis methods, limit their extensive use. In this research, we have created an inorganic switchable photochromic material exploiting TiO2 ability of creating an exciton upon excitation, copper as the chromophore, and graphene's extraordinarily high electron mobility. Spatially-resolved electron energy-loss spectroscopy and aberration-corrected transmission electron microscopy imaging highlight the high sp2 content of the graphene flakes as well as the presence of few-layers nanocage graphene decorating the surface of the flakes. Our material showed itself to be able to work under visible-light, its photochromic property being three times faster than conventional titania based photochromic materials, reaching a stable change in coloration after only 30 min of visible-light irradiation (vs. > 120 min in conventional Cu–TiO2). With the addition of just 1 wt% graphene, the material exhibited a staggeringly stable photochromic switching over repeated cycles. These results relate to the best previously reported values for any form of TiO2-based photochromic material. This is therefore an excellent candidate for smart-windows, light-sensitive information and energy storage devices, and other chromic devices and applications.

Graphene reduction of P25 titania: Ti3+- doped titania/graphene nanohybrids for enhanced photocatalytic hydrogen production

Ti3+-doped titania has attracted great attention in recent years by its enhanced photocatalytic performance as compared to the conventional titania systems. In this work, solvothermally reduced hydroxy graphene (RHG), derived from fluorographite (FGT), is used to reduce commercially available P25 titania to produce Ti3+-doped, TiO2-x/RHG nanocomposites, via a facile solid-state route. These nanohybrids exhibit high performance towards photocatalytic hydrogen generation under broad-band irradiation, with a 3497 μmol/g/h hydrogen production rate, without the assistance of any noble metal co-catalyst. This enhanced rate can be attributed to the surface defects generated by Ti3+-doping as well as the ability of RHG to perform as a highly efficient scavenger for the photogenerated electrons. It is hypothesized that RHG could serve as one of the most suitable co-catalysts for the semiconductor-based photocatalysts.

Enhancement in photoelectrochemical ability via re-engineering the band gap of multi-podal titania nanotubes on functionalizing with copper oxide nano-cubes

In this study, multi-podal titania nanotube array (anatase) were fabricated via electrochemical anodization technique on employing third generation electrolyte with suitable and sharp optimization of every anodization parameter. In comparison to conventional titania nanotubes, these nanotubes offer sufficient nanotube wall/electrolyte interface and thereby makes the appreciable reduction in electron hole pair recombination rate by immediate involvement of holes and electrons in oxidation and reduction process, respectively. Furthermore, 85 nm diameter variation in these nanotubes from base diameter 263 nm to top diameter 348 nm makes the incoming light to undergo through graded refractive index which in corresponding increases their light harnessing ability. Although morphological advantage of these nanotubes is being efficiently harnessed in the scattering of incident light but the large band gap 3.2 eV still confines their utility to UV region only. To increase their photo-electrochemical potential under visible light as well, these nanotubes were functionalized suitably with Cu2O nano-cubes without disturbing the nanotube morphology. Under the analysis of their photo-electrochemical potential, the photocurrent density recorded for bare and Cu2O functionalized multi-podal titania nanotube array under visible light source 300 W Xenon lamp (1 sun illumination) was 0.27 mAcm−2 and 0.39 mAcm−2, respectively. The enhancement of ~45% in photocurrent density under visible light illumination is attributed to suitable band edge positions in Cu2O with respect to the band edge positions in TiO2 which in corresponding leads the formation of effective visible light active band gap in the resulting hybrid structure.

Enhancement in photo-electrochemical efficiency by reducing recombination rate in branched TiO2 nanotube array on functionalizing with ZnO micro crystals

In this study, branched TiO2 nanotube array were fabricated through electrochemical anodization process at constant voltage using third generation electrolyte. On account of morphological advantage, these nanotubes shows significant enhancement in photo-electrochemical property than compact or conventional titania nanotube array. However, their photo-electrochemical efficiency intensifies on coating with ZnO micro-crystals. ZnO coated branched TiO2 nanotube array shows a photocurrent density of 27.8 mA cm−2 which is 1.55 times the photocurrent density (17.2 mA cm−2) shown by bare branched titania nanotubes. The significant enhancement in photocurrent density shown by the resulting ZnO/TiO2 hybrid structure is attributed to suppression in electron–hole recombination phenomenon by offering smooth pathway to photo generated excitons on account of staggered band edge positions in individual semiconductors.

Flexible composite via rapid titania coating by microwave-assisted hydrothermal synthesis

The aim of this work was to prepare a flexible nanocomposite from ultra-fine titanium oxide ( $$\hbox {TiO}_{2}$$ ) growth on carbon fibre via microwave-assisted hydrothermal synthesis (MHS) and to evaluate its photocatalytic properties. The $$\hbox {TiO}_{2}$$ nanoparticles were directly grown on the carbon fibre (CF). Thus, a study comparing the conventional titania coating vs. the MHS were performed. The significant layer interaction as a function of the coating method on the visible and dark dye photodegradation performance was observed. Techniques such as X-ray diffraction, electron microscopy (field-emission scanning electron microscope (FESEM)), Raman spectroscopy, among others were used aiming to characterize the different route samples. This study reports a reproducible and single method to manufacture of nanocomposites through the growth of $$\hbox {TiO}_{2}$$ nanoparticle on CF by MHS that allow controlling the thickness layer. Similar procedure of synthesized nanocomposite could be applied in different chemical compositions to advanced applications, based on the electrochemical nanostructure.

Incorporation of graphene into SnO2 photoanodes for dye-sensitized solar cells

In dye-sensitized solar cell (DSSC) photoanodes, tin dioxide (SnO2) structures present a promising alternative semiconducting oxide to the conventional titania (TiO2), but they suffer from poor photovoltaic (PV) efficiency caused by insufficient dye adsorption and low energy value of the conduction band. A hybrid structure consisting of SnO2 and reduced graphene oxide (SnO2-RGO) was synthesized via a microwave-assisted method and has been employed as a photoanode in DSSCs. Incorporation of RGO into the SnO2 photoanode enhanced the power conversion efficiency of DSSC device by 91.5%, as compared to the device assembled without RGO. This efficiency improvement can be attributed to increased dye loading, enhanced electron transfer and addition of suitable energy levels in the photoanode. Finally, the use of RGO addresses the major shortcoming of SnO2 when employed as a DSSC photoanode, namely poor dye adsorption and slow electron transfer rate.

Ammonia/water vapor-induced internal hydrolysis synthesis of sulfated TiO2/SBA-15 solid acid

Sulfated titania loaded mesoporous silica solid acid catalyst was successfully obtained by a facile ammonia/water vapor-induced internal hydrolysis route. Ti(SO4)2 used as titania precursor and the supplier of SO4 2− ions. By controlling the hydrolysis rate of precursor under ammonia/water vapor ambience, a thin titania layer formed and coated on the pore internal surface of SBA-15. The solid acid catalyst was characterized by powder X-ray diffraction, N2 adsorption–desorption and transmission electron microscopy, and the results showed that such catalyst retained the ordered mesoporous structure, relatively high surface area, connected and open pore channel without pore blocking. Fourier transform infrared spectroscopy and energy dispersive spectrum analysis results indicated that the resultant catalyst possessed higher connect of sulfate groups and more catalytically active sites than those of unloaded sulfated titania and sulfated titania loaded SBA-15 hydrolyzed by ammonia aqueous solution. Meanwhile, the catalyzing results suggested such solid acid catalyst exhibited improved catalytic property for esterification of oleic acid with methanol compared to conventional sulfated titania solid acid. In addition, the experimental parameters including reaction time, reaction temperature and the molar ratio of reactants were optimized, and ca. 85 % of catalytic activity were remained after three consecutive cycles.

Nanohybrid materials of titania nanosheets and plasmonic gold nanoparticles for effective hydrogen evolution

A new type of nanocomposites containing titania and gold were prepared via the coupling between exfoliated Ti0.91O2 nanosheets and surfactant-capped Au nanoparticles, followed by flocculation and calcination. After hybridization with Ti0.91O2 nanosheets, octahedral Au nanoparticles were embedded intimately into the matrix of titania, leading to a broad absorption peak assigned to surface plasmon resonance (SPR) effect in the visible region. The obtained nanocomposite exhibited remarkably improved photocatalytic hydrogen evolution performance compared to naked titania and conventional titania with photodeposited Au co-catalyst, due to the special SPR effect of the relatively large octahedral Au nanoparticles. Through control experiments, we demonstrated that the octahedral Au nanoparticles mainly functioned as local light intensifier and photon scattering agent.

Frontispiece: Is TiO2 (B) the Future of Titanium-Based Battery Materials?

The upper part of the frontispiece shows the operating potential vs. the practical specific charge capacity of different positive and negative Li-ion battery materials. The stability window of todays liquid electrolyte solutions is confined by the formation of the cathode electrolyte interphase (CEI) and the solid electrolyte interphase (SEI). In the lower part of the frontispiece, the overall performance of conventional carbonaceous and titania based materials are compared. In this mini review, Fehse and Ventosa illustrate the promising role of TiO2 (B) as battery material with enhanced safety, cycle stability and rate performance.

Dry Sliding Wear Behavior of SiC Reinforced Titania Coating Deposited by High Velocity Oxy Fuel Spraying

The Conventional Titania (TiO2) and Titania blends with 10% SiC powder was thermally sprayed on commercially pure titanium substrate using High Velocity Oxy-Fuel (HVOF) spraying. The microhardness value of these coatings was measured by Vickers microhardness tester. The coating porosity, cross sectional morphology and wear surface morphologies was observed in Optical Micrograph (OM) and Scanning Electron Micrograph (SEM). The X-Ray Diffraction analysis was made to observe the phase composition of these coatings. The wear behavior of these coatings was studied in Pin-on-Disk arrangement as per ASTM G99 standard. It was found that addition of SiC enhances the hardness and wear resistance of the coating. Further, wear surface morphology was analysed and possible wear mechanisms were discussed.

Visible‐Light Photocatalytic Hydrogen Generation by Using Dye‐Sensitized Graphene Oxide as a Photocatalyst

Dye-sensitized graphene oxide is able to generate hydrogen from water/methanol mixtures (80:20) by using visible or solar light. The most efficient photocatalyst tested contained a tris(2,2-bipyridyl) ruthenium(II) complex incorporated in the interlayer spaces of a few layers of graphene oxide with a moderate degree of oxidation. The graphene oxide-based photocatalyst does not contain noble metals and we have determined that it is two orders of magnitude more active than catalysts based on conventional titania.

Nanostructured Titanium: The Ideal Material for Improving Orthopedic Implant Efficacy?

Titanium (Ti) and its alloys have been widely used as implant materials for orthopedic applications owing to their excellent wear, corrosion resistance, light weight but strong mechanical and acceptable biocompatibility properties. However, such implants still widely experience lifetimes of less than 20 years owing to a variety of reasons eventually leading to implant separation from bone. In 1999, Webster et al. provided the first evidence that osteoblast (bone-forming cells) adhesion and bone formation significantly increases on nanostructured titania compared with conventional titania [1]. Since then, nanotechnology (or the use of materials with dimensions less than 100 nm in at least 1D) have been proposed to improve the quality of orthopedic implants by better mimicking the nanoscale properties of native bone tissue.

Coupling Titania Nanotubes and Carbon Nanotubes To Create Photocatalytic Nanocomposites

A titania nanotube/single-wall carbon nanotube composite was prepared by a simple hydration dehydration process. These composites were characterized using X-ray diffraction and spectroscopic techniques (UV–visible diffuse reflectance, Raman, photoluminescence, and EPR) as well as electron microscopy (SEM, TEM). SEM and TEM images indicated that single-wall carbon nanotubes (SWCNTs) were interwoven with the titania nanotubes. Raman spectra further confirmed the chemical interaction between the titania nanotube and the SWCNT in the composites. The photoactivity of these composites was tested by the photooxidation of acetaldehyde. The composites showed enhanced photoactivity under both visible and UV light in comparison with conventional titania (P25) and controls. The composite having a mass ratio of 1:50 (SWCNT/TiNT) showed the maximum photocatalytic activity for acetaldehyde decay under visible light. XPS and EPR spectra indicated the creation of Ti–O–C bonds between the titania nanotube and the SWCNTs during the hydration dehydration process, which explains the visible light photoactivity.

Hydrothermal Synthesis of High Electron Mobility Zn-doped SnO2 Nanoflowers as Photoanode Material for Efficient Dye-Sensitized Solar Cells

This paper demonstrates the potential of a new photoanode material Zn-doped SnO2 nanoflower for efficient dye-sensitized solar cells. The nanoflower structure is synthesized using a hydrothermal method and is shown to have electron mobility higher than that of the conventional titania photoanode. The overall power conversion efficiency for the Zn-doped SnO2 nanoflower dye-sensitized solar cell reaches 3.00% with a Voc of 0.78 V and increases to 6.78% after TiCl4 treatment. Electrochemical impedance spectroscopy measurement showed that the Zn-doped SnO2 nanoflower film has a large intrinsic electron mobility that favors the fast charge transport. This work shows that Zn-doped SnO2 nanoflower material is a most interesting material and has good potential for application in solar cells.

Ni(OH)2 modified CdS nanorods for highly efficient visible-light-driven photocatalytic H2 generation

Conventional titania photocatalysts possess good activity and stability, but require near-ultraviolet (UV) irradiation (about 4% of the solar spectrum) for effective photocatalysis, which severely limits their practical applications. Here we report the synthesis of new visible-light-driven Ni(OH)2-modified CdS nanorod-type composite photocatalysts by a simple precipitation method using CdS nanorods as a support and Ni(NO3)2 as a nickel hydroxide precursor. A special emphasis is placed on the effect of Ni(OH)2 content in this composite photocatalyst on the photocatalytic rate of H2 production in triethanolamine aqueous solutions under visible light irradiation. This study shows that the photocatalytic H2-production activity of CdS nanorods is significantly enhanced by modifying them with Ni(OH)2. The optimal Ni(OH)2 loading was found to be 23 mol%, which resulted in a visible-light H2-production rate of 5085 μmol h−1 g−1 corresponding to 28% quantum efficiency (QE) at 420 nm, exceeding that of pure CdS and 1wt% Pt loaded CdS nanorods by a factor of 145 and 1.3 times, respectively. This enhanced photocatalytic H2-production activity was achieved because the potential of Ni2+/Ni (Ni2+ + 2e− = Ni, E° = −0.23 V) is less negative than the conduction band (CB) (−0.7 V) of CdS, meanwhile this potential is more negative than the reduction potential of H+/H2 (2H+ + 2e− = H2, E° = 0.0 V), which favors the transfer of CB electrons from CdS to Ni(OH)2 and the reduction of Ni2+ to Ni0. The role of Ni0 is to help the charge separation and to act as a co-catalyst for water reduction, thus enhancing the photocatalytic H2-production activity. This work not only shows a possibility for the utilization of low cost Ni(OH)2 as a substitute for noble metal Pt in photocatalytic H2-production but also demonstrates its capability for the consumption of the pollutant triethanolamine, used as a sacrificial reagent in this process.

Preparing titania aerogel monolithic chromatography columns using supercritical carbon dioxide

The search for a method to fabricate monolithic inorganic columns has attracted significant recent attention due to their unique ability in separation applications of various biomolecules. Silica and polymer based monolithic columns have been prepared, but titania and other metal oxide monoliths have been elusive, primarily due to their fragility. This article describes a new approach for preparing nanostructured titania based columns, which offer better performance over conventional particle packed columns for separating a wide variety of biomolecules including phosphopeptides. TiO(2) monolithic aerogels were synthesized in separation columns using in situ sol-gel reactions in supercritical carbon dioxide (scCO(2)) followed by calcination, and compared to those prepared in heptanes. The characterization results show that scCO(2) is a better solvent for the sol-gel reactions, providing lower shrinkage with the anatase TiO(2) monolith composed of nanofibers with very high surface areas. The monolithic columns show the ability to isolate phosphopeptides with little flow resistance compared to conventional titania particle based microcolumns.

Effect of ethanol washing of titania clay mineral composites on photocatalysis for phenol decomposition

A mesoporous material of titania and clay minerals was prepared from TiOSO 4 and Laponite, hectorite, beidellite and saponite. The impact of ethanol washing before calcination on the structure and photocatalytic activity for phenol decomposition was investigated. As comparison, conventional titania pillared clay minerals were also prepared. The mesoporous material had more mesopores and better crystallized anatase particles than conventional pillared clay minerals. The photocatalytic activity of the mesoporous material was far better than that of the conventional pillared clay minerals. Thus, mesopores and larger anatase crystals were beneficial to the photocatalysis. The specific surface area and pore volume of the mesoporous material, which was obtained by washing with ethanol, were larger than those of the sample without ethanol washing. The photocatalytic activity of the ethanol washed samples was 2–6 times higher than that of the corresponding sample without ethanol washing. The main reasons for the high activity were the ethanol washed samples had larger specific surface area and pore volume, and they could be readily dispersed in water. The structure of samples was investigated by XRD, TEM equipped with EDS and N 2 adsorption–desorption method.

High bone-like apatite-forming ability of mesoporous titania films

In vitro bioactivity of Ti alloy can be enhanced by mesoporous titania films (MTFs), which were prepared on Ti6Al4V substrates by evaporation-induced self-assembly (EISA) process. In vitro bioactivity tests of the MTFs were studied by immersing them in simulated body fluid (SBF). The effect of the mesostructure on improving the apatite-forming ability of the MTFs was investigated through XRD, SEM, TEM and FTIR. The MTFs showed a mesoporous anatase structure with large surface area, high pore volume, and a narrow pore size distribution. Calcium-deficient hydroxycarbonate apatites were observed after soaking the MTFs in SBF for 7 days, rather than 14 days for conventional titania films (TFs). These demonstrated that the mesostructure greatly improved the bioactivity of the MTFs, which was attributed to high specific surface area, suitable pore size and high pore volume. The induced apatite by the MTFs was very similar to bone-like apatite, including Mg, Na ions, carbonated structure and ordered nano-network structure. In this work, the MG63 cell proliferation experiment indicated that the MTFs had a good biocompatibility and can provide surface suitable for the MG63 cell proliferation. Such MTFs on Ti alloys have potential application in implanting and bone regeneration materials in the future.

Surface properties and thermal stability of SiO2-crystalline TiO2 nano-composites

TiO2/SiO2 nanocomposites are synthesized and fully characterized after thermal stabilization at temperatures between 400 °C and 800 °C. The control of the impregnation media is crucial to obtain nanocomposites of satisfactory quality, i.e. presenting no segregation of titania particles outside the silica pore structure. Characterization shows that pore size and pore volume decrease linearly with an increase in titania loading, and remain close to the theoretical values calculated assuming the formation of a non-porous coating. Surface area remains unchanged whatever the titania loading (always comprised between 450 and 480 m2 g−1), and micropore volume evolution suggests the formation of nanometric particles within the silica pores. While X-ray diffraction is inefficient to identify the titania phase, Raman spectroscopy showed the formation of anatase particles, with crystal sizes in the nanometric range (<4.5 nm, when stabilized at 400 °C). Satisfying thermal stability is obtained on the low titania loading nanocomposites (20 wt% TiO2), with only minor anatase crystal growth up to 800 °C. Further characterization by FT-IR of the surface chemical properties of the nanocomposites showed properties similar to that of conventional titania, while improved oxygen mobilities (as evaluated by the 18O/16O exchange reaction) are reported on the low titania loading, thermally stable, composites.

Catalytic inactivation of bacteria using Pd-modified titania

Abstract Pd and Pt-modified TiO 2 were compared with un-modified TiO 2 for the photocatalytic sterilization of Escherichia coli in water. Pd/TiO 2 was found to work significantly faster than Pt/TiO 2 , and was also active in the absence of light; indicating an alternative mechanism to conventional titania photocatalysis. The Pd/TiO 2 catalyst temporarily lost bactericidal activity after each use, but was re-activated by exposure to air prior to reuse. A direct correlation between oxidation state and antimicrobial activity was indicated for Pd/TiO 2 . XPS analysis confirmed the oxidation of Pd on the catalyst after exposure to air and the subsequent reduction when immersed in water.