TiO2 Solution Research Articles

Study on the effect of Fe and N co-doped supported TiO2/GF photocatalytic oxidation of nitrobenzene wastewater

This research aims to treat the refractory nitrobenzene wastewater in the industrial water treatment industry with modified supported TiO2, and to study its influence on the treatment effect.Experiments have found that by preparing Fe and N co-doped TiO2/GF supported catalysts, it has better catalytic performance. Under the same conditions, Fe and N co-doped TiO2/GF can degrade nitrobenzene wastewater better than single Doped with Fe-TiO2/GF and N-TiO2/GF, the removal rates of nitrobenzene and COD are as high as 97.2% and 92.5%, respectively.The Fe and N co-doped TiO2/GF catalyst overcomes the agglomeration of traditional powdered TiO2 in solution, and has a good removal effect on nitrobenzene wastewater.

Preprogrammed microfluidic system for parallel anti-reflection coating by layer-by-layer assembly.

Layer-by-layer (LbL) assembly is a widely used method of nanofilm coating in various technology applications; however, the coating process is typically time-consuming and labor-intensive. This study presents a microfluidic platform that performs LbL assembly in a fast, parallel, preprogrammed manner, with only water-head pressure as the driving force. The platform generates periodic sequential outflows with four solutions (TiO2 and SiO2 nanoparticle solutions and two washing solutions), and simultaneously applies 12 different conditions of coating period (0.6-4 min) and shear stress (0.7-15 dyn cm-2) for anti-reflection coating in the visual spectrum. The thickness and roughness of the coated films are well regulated at the nanoscale using shear stress, coating period, and the number of bilayers. In this way, our study reveals the substantial influence of shear stress on the relative composition of the nanoparticles and void volume in the films, thereby varying the film transmittance with a maximum value of 98%. Compared to the conventional immersive coating method, the coating duration of our method was 15 times faster. This parallel coating method is highly effective for determining optimized coating conditions.

Visible-Light Sensitive Photocatalytic Activity of FeO<i><sub>x</sub></i>- and P-Modified TiO<sub>2</sub> with Rutile Structure

Nanocrystalline rutile TiO2 particles were prepared via hydrothermal treatment of Ti-containing precursors obtained by low-temperature aging for a transparent diluted HCl solution of amorphous TiO2. The products were modified with FeOx and phosphoric acid, and the photocatalytic activities of the obtained catalysts under visible-light irradiation were examined. By the addition of FeOx or phosphoric acid, the photocatalytic activity of the rutile TiO2 was slightly increased. On the contrary, by the FeOx loading and subsequent addition of phosphoric acid, significant increases in the photocatalytic activity were attained. Results of UV-vis suggest that the iron oxides formed on the surface of rutile TiO2 were changed into highly dispersed iron phosphate species by the addition of phosphoric acid. It was presumed that these species effectively suppress the recombination reaction between the photogenerated electrons and holes and contribute to the high photocatalytic activity of the rutile TiO2 photocatalysts modified with FeOx and phosphoric acid.

Studies on high refractive index amorphous TiO2 thin film for possible improvement of light extraction efficiency in organic light emitting diodes

Studies on low-cost sol–gel spin-coated TiO2 thin film with high refractive index (HRI), which may be used as an intermediate layer to enhance the light extraction efficiency (LEE) of a typical bottom-emitting organic light emitting diode (OLED), are reported. The TiO2 solution is prepared using titanium tetra iso-propoxide, acetic acid, and ethanol. Spin coating method is used to deposit TiO2 thin films on glass substrate. Different optical characterizations of as-deposited and annealed (150°C, 300°C, and 450°C) TiO2 thin films on glass substrate are done, from which different properties of the film are derived. Ellipsometric measurement shows shrinkage in the thickness of the as-deposited TiO2 films after annealing at different temperatures. X-ray diffraction reveals amorphous TiO2 formation for all the samples. The RI of the coated film increases with the increase in annealing temperatures. Its value at 633 nm wavelength for the as-deposited film is found to be 2.1, which is quite high and it is seen that this RI can be further increased to 2.78 by annealing the samples at 450°C. This value is comparatively high compared to several other reported values of other researchers. The as-deposited sample reveals highest porosity, which further decreases with rise in annealing temperature. Our calculation of LEE for a typical OLED with the intermediate layer of this HRI as-deposited TiO2 film shows improvement of the LEE. However for annealed films, the experimentally obtained thicknesses are not adequate for this improvement, but it is shown that by increasing the film thickness, further improvement of LEE is possible.

Photocatalytic Reactivity of Carbon–Nitrogen–Sulfur-Doped TiO2 Upconversion Phosphor Composites

Sol–gel synthesized N-doped and carbon–nitrogen–sulfur (CNS)-doped TiO2 solutions were deposited on upconversion phosphor using a dip coating method. Scanning electron microscopy (SEM) imaging showed that there was a change in the morphology of TiO2 coated on NaYF4:Yb,Er from spherical to nanorods caused by additional urea and thiourea doping reagents. Fourier transform infrared (FTIR) spectroscopy further verified the existence of nitrate–hyponitrite, carboxylate, and SO42− because of the doping effect. NaYF4:Yb,Er composites coated with N- and CNS-doped TiO2 exhibited a slight shift of UV-Vis spectra towards the visible light region. Photodecomposition of methylene blue (MB) was evaluated under 254 nm germicidal lamps and a 300 W Xe lamp with UV/Vis cut off filters. The photodegradation of toluene was evaluated on TiO2/NaYF4:Yb,Er and CNS-doped TiO2/NaYF4:Yb,Er samples under UV light illumination. The photocatalytic reactivity with CNS-doped TiO2/NaYF4:Yb,Er surpassed that of the undoped TiO2/NaYF4:Yb,Er for the MB solution and toluene. Photocatalytic activity is increased by CNS doping of TiO2, which improves light sensitization as a result of band gap narrowing due to impurity sites.

Shear Induced TiO2 Nano Structure Using Brush-Coating for Liquid Crystal Alignment

We have developed a very useful and cost-effective liquid crystal (LC) alignment layer of brush-coated TiO2 that is solution-processable for twisted nematic (TN) LC cells. TiO2 was prepared via the sol-gel method. The TiO2 solution was brush-coated on the substrate, followed by an annealing process. During the brush-coating process, a retracting force is generated on the deposited TiO solutions along the coating direction. The annealing process hardens the TiO2 and generates shearing stress arising from the retracting force along the brush-coating direction. The shearing stress created highly oriented nano/microstructure and uniformly aligned LCs with a stable pretilt angle of 0.6°. TN mode LC cells based on brush-coated TiO2 exhibited a performance of 12.5 ms of response and a threshold voltage of 1.8 V. Our brush-coated TiO2 incorporates two steps of the film deposition and alignment process into one step.

Large-sized nano-TiO2/SiO2 mesoporous nanofilmconstructed macroporous photocatalysts with excellent photocatalytic performance

Novel large-sized mesoporous nanofilm-constructed macroporous SiO2 (LMNCMS) with two sets of well-defined 3D continuous pass-through macropores (pore size of 0.5–1.0 μm, wall thickness of 40–50 nm) was prepared through a dual-templating approach, and used as an advanced support for TiO2 nanocrystalline photocatalyst. The structural and optical properties of the as-prepared materials were investigated by various characterization techniques in order to explore the connections between catalysts’ features and catalytic performance. The photocatalytic activities were evaluated by degradations of methylene blue (MB) and phenol under the simulated sunlight irradiation. To gain insight into the impact of preparation and operation conditions on photocatalytic degradation processes, experiments were conducted at wide ranges of the TiO2 loading content, calcination temperature, solution pH, and photocatalyst dosage. Nano-TiO2/LMNCMS exhibited high photocatalytic activity and stability. Rapid matter transport, good accessibility of pollutants to TiO2 and high light harvesting could mainly account for the superior photocatalytic performance. The trapping experiments were performed to identify the main reactive species in the catalytic reactions.

Application of FeCl3 and TiO2-coated algae as innovative biophotocatalysts for Cr(VI) removal from aqueous solution: A process intensification strategy

Chromium is a metal that could be both toxic and essential dependent on its oxidation state. While Cr(VI) is toxic to plants, animals and microorganisms, Cr(III) at low levels is an essential dietary nutrient for human beings. In this study, novel biophotocatalysts were developed and applied for Cr(VI) reduction and removal from aqueous solution. The biophotocatalysts were successfully prepared by the direct coating of the raw and protonated (immersion into 0.2 M HNO3) brown algae Laminaria hyperborea with FeCl3, AlCl3, and TiO2 solutions. The products of each treatment were characterized and utilized in an equilibrium study for Cr(VI) removal, which revealed a low efficiency for algae coated with aluminum. The Cr(VI) removal via the synergic effect of photocatalysis and adsorption was investigated through kinetic studies in the presence and in the absence of UV radiation using protonated algae, protonated algae coated with iron and protonated algae coated with titanium as biophotocatalysts. The results showed that the material previously protonated and coated with iron presented the best Cr(VI) removal results, reaching an efficiency removal of 100% after 90 min. The UV radiation improves the removal efficiency of the chromium species for the experiments carried out with protonated algae coated with titanium. The scale-up of the combined process was successfully performed on a radial photoreactor with a concentric UV radiation using the protonated algae coated with iron and titanium as biophotocatalysts. Protonated algae coated with iron, the Cr(VI) species disappeared completely after 120 min, while for protonated algae coated with titanium, the Cr(VI) was still in the solution even after 210 min. The reuse of the biophotocatalysts in consecutive Cr(VI) treatment cycles without regeneration was also performed, indicating that the protonated algae coated with iron have the potential to be used in as biophotocatalysts in the treatment of wastewaters contaminated with Cr(VI), reaching the restricted discharge limit of this metal.

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

New Chemoresistive Gas Sensor Arrays for Outdoor Air Quality Monitoring: A Combined R&D and Outreach Activities

Development of functional TiO2 coatings deposited on cementitious materials

This present paper evaluates the functionality of different TiO2 coatings deposited on the exposed surface of Portland cement pastes. Cement pastes coated from a crystalline TiO2 suspension (CS) and an amorphous TiO2 solution (AS) were compared. Some samples with film deposition from AS were submitted to autoclave treatment. Film deposition was carried out by spin-coating with 1, 2, 3 or 5 coating layers. The coating morphology was observed by SEM and the possible presence of TiO2 crystalline phase was confirmed by XRD. Static water contact angle and RhB degradation were used to assess the photo-induced activity of the films. All the films deposited from CS exhibits both photo-induced superhydrophilicity and photoactivity. The samples coated from AS display only a minor increase in the rate of degradation of rhodamine B. The results suggest that the autoclave treatment did not favor the formation of crystalline TiO2 phases.

Effect of Concentration Variation on Optical and Structural Properties of TiO2 Thin Films

Concentrations in weight percent (5- 25 wt %) of TiO2 films used to optimize the film formation. The TiO2 films on glass substrates successfully obtained by spin-coating process using TiO2 nanopowder as precursor. Ultraviolet-Visible (UV-Vis), Scanning Electron Microscopy (SEM) equipped with Electron Diffraction X-ray (EDX) and X-ray Diffractometer (XRD) techniques used to characterize the films. The result of electron transport material (TiO2) showed that film prepared from 15 wt % of TiO2 solution and annealed at 450 has highest transmittance at visible light region with indirect optical band gap of 3.24 eV which corresponds to wavelength of 382 nm whereas 20 wt % has indirect band gap of 2.99 nm equivalent to 414.7 nm . The chemical analysis from Electron Diffraction Spectroscopy (EDS) of the material shows titanium and oxygen present at L and K-shells, respectively. The sample crystallized with preferred orientation at (101) from XRD analysis.

Preparation of TiO2 thin layer on ceramics using dip coating method for degradation humic acid

TiO2 thin layer on ceramic with dip coating method and photocatalyst activity test in humic acid. One of the photocatalysts used for the degradation of humic acid is TiO2 because TiO2 has several advantages, including non-toxic, stable, high activity, relatively inexpensive and environmentally friendly. This study was performed using TTIP as a precursor and MEA as an additive in isopropanol. Addition of MEA influences the stability of the titanium oxane solution. Ceramics were coated in a 0.5 M TiO2 solution by a dip coating method, then dried in an oven at 110°C for 10 minutes and difugeice at 400 ° C for 2 hours. Maximum degradation of 0.5 M TiO2 is 59.94% over 24 hours using 8 watt fluorescent lamps with 4 TiO2 coatings on ceramic.

Enhanced Transport of TiO2-Reduced Graphene Oxide Nanocomposites in Saturated Porous Media: the Impact of Loaded TiO2 Shape and Solution Conditions

Laboratory sand column experiments were conducted to model the transport behavior of TiO₂ nanoparticle-reduced graphene oxide nanocomposite (TiO₂ NP/rGO) and TiO₂ nanowire-reduced graphene oxide nanocomposite (TiO₂ NW/rGO) using different electrolyte solutions and pH values. The breakthrough curve of TiO₂/rGO nanocomposite shows that the mobility is highly sensitive to ionic strength and pH. Experimental results found that the zeta potential of TiO₂ NW/rGO is more negative due to more hydroxide ions in solution from the TiO₂ NWs. The mobility of TiO₂ NW/rGO is slightly greater than that of TiO₂ NP/rGO at lower ionic strength (1–50 mM NaCl and 1–5 mM CaCl₂), whereas at 10 mM CaCl₂, TiO₂ NW/rGO had weak transport because of physical straining. The ratio of the hydrodynamic diameter (4214 nm) to sand diameter was as high as 0.83. Mobility increased for both TiO₂ NP/rGO and TiO₂ NW/rGO with respect to ionic strength because of electrostatic repulsions. When the pH was 9 with a 10 mM NaCl background solution, the stronger energy barrier between the nanocomposite and sand contributed to the enhanced transport behavior. However, with a solution at pH 3–6, the ripening effect controlled the transport of TiO₂ NW/rGO. The normalized concentrations rapidly climbed to a maximum (0.05 and 0.14) and then decreased gradually after 2 pore volumes. In general, these behaviors may well predict the fate of carbon-based nanoparticles with tailwater or wastewater flowing into soil environments. Graphical Abstract

Electrodeposited MoS2 counter electrode for flexible dye sensitized solar cell module with ionic liquid assisted photoelectrode

Dye-sensitized solar cell (DSSC) offers great advantages includes low cost materials, economic fabrication, suitable for low-light conversion, flexibility option, color design possibilities, etc. In the present study, a semi-transparent, molybdenum disulphide (MoS2) flexible counter electrode (CE) is realized through electrodeposition method. Low temperature processed TiO2 solution is used for photoelectrode (PE) preparation. Conductive ionic liquid (BVImI + LiI) is used to modify the surface of photoelectrode for alteration of conduction band level of PE, towards enriched electron injection rate into TiO2. Flexible dye-sensitized solar cell (f-DSSC) fabricated by sandwich the photoelectrode and counter electrodes, and an ionic liquid electrolyte is injected. The surface modified photoelectrode (SM-PE) assisted test cell (0.16 cm2 active area) witnessed an enhanced current density value 12.46 mA/cm2 and power conversion efficiency (PCE) 4.84% is higher than the normal PE based f-DSSC (11.56 mA/cm2 and 4.35%). For comparison, platinum-based f-DSSC with SM-PE is fabricated, is attained 6.08% of PCE. The f-DSSC sub-module with MoS2-CE gave 4.21% of PCE, the results are presented.

Degradation kinetics of isoproturon and its subsequent products in contact with TiO2 functionalized silica nanofibers

A challenge for the photodegradation of (organic) micro-pollutants in waste water treatment is the mechanistic and kinetic understanding beyond the degradation of the initial (parent) harmful product, e.g. the phenylurea herbicide isoproturon (IPU). By combining liquid chromatography–mass spectrometry and kinetic Monte Carlo modeling, we demonstrate that upon optimizing the dip-coating conditions (0.34 mol L−1 TiO2 solution at a coating speed of 160 mm min−1) for the functionalization of a superhydrophilic electrospun silica nanofibrous membrane (i) hydroxylation is a dominant reaction pathway and (ii) once IPU reacts on the surface of the TiO2 nanoparticles, further hydroxylation occurs sufficiently fast, with complete IPU removal under the detection limit (5–10 mg Lsolution−1) as a result of UV irradiation within 8 h. As hydroxylation is dominant, degradation intermediates with a higher water solubility are formed and therefore a decreased toxicity is obtained upon reintroducing the treated solution into the environment. This is confirmed by respirometry, with an increase in the oxygen uptake rate of an activated sludge from 5.9 mg O2 gactivated sludge−1h−1 for an untreated 10 mg L−1 IPU solution to 8.2 mg O2 gactivated sludge−1 h−1 for a solution irradiated for 8 h, in line with a blank solution.

Sintering Temperature Dependent Magnetic and Dielectric Properties of Polycrystalline xBa<sub>0.95</sub>Sr<sub>0.05</sub>TiO<sub>3</sub>-(1 - x)BiFe<sub>0.90</sub>Gd<sub>0.10</sub>O<sub>3</sub> Ceramics

Polycrystalline xBa0.95Sr0.05TiO3-(1 - x)BiFe0.90Gd0.10O3 ceramics were prepared by standard solid state reaction technique using the solid solution of BaCO3, SrCO3, TiO2, Bi2O3, Fe2O3 and Gd2O3. The compound is a BiFeO3 based multiferroic material which contains both magnetic and electric properties. The synthesized ceramics noticed better properties than xBaTiO3-(1 - x)BiFeO3 because of adding rare earth element Gd which have higher magnetic moment than Fe. The prepared samples were sintered at 900˚C, 950˚C and 1000˚C for 1 h. The effect of sintering temperature on density of the compound, complex initial permeability, dielectric properties and complex impedance analysis was reported in this article. Density of the ceramics was found to be enhanced with the rise in sintering temperature which implied porosity of the compound decreased when sintering temperature was increased. Enhanced complex initial permeability was noticed for the samples up to 950˚C and this might be attributed to reducing the motion of domain wall when the ceramics were sintered above 950˚C. Value of dielectric constant increased whereas dielectric loss decreased and these modifications might be expected because of changing density and grain size due to the variation of sintering temperature. Grain resistance (resistance due to grains) was determined from complex impedance analysis and it reduced with the rise in sintering temperature. The studied multiferroic material exhibited weak ferromagnetism but is an alternative product of environmental hazard lead (Pb) based multiferroic material and it is expected to be environment friendly.

Optimization of Self-Cleaning Thin-Film Layer for Photovoltaic Applications.

To improve the productivity of a photovoltaic (PV) module, TiO₂ thin films of different thicknesses were applied as a self-cleaning layer on soda-lime glass and a Si PV module by spray-coating a TiO₂ solution. The structural, optical, and wettability characteristics of the TiO₂ thin films were investigated with respect to the thickness. Thermogravimetric-differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, contact-angle analysis, ultraviolet-visible spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and a solar simulator were used to analyze the prepared TiO₂ thin films. The optimal thickness was determined to be 100 nm. The TiO₂ thin film exhibited a self-cleaning ability even after post-annealing at 250 °C. After the self-cleaning ability was confirmed, the TiO₂ thin film was applied to the PV module.

Lemon-Fruit-Based Green Synthesis of Zinc Oxide Nanoparticles and Titanium Dioxide Nanoparticles against Soft Rot Bacterial Pathogen Dickeya dadantii.

Edible plant fruits are safe raw materials free of toxicants and rich in biomolecules for reducing metal ions and stabilizing nanoparticles. Zinc oxide nanoparticles (ZnONPs) and titanium dioxide nanoparticles (TiO2NPs) are the most produced consumer nanomaterials and have known antibacterial activities but have rarely been used against phytopathogenic bacteria. Here, we synthesized ZnONPs and TiO2NPs simply by mixing ZnO or TiO2 solution with a lemon fruit extract at room temperature and showed their antibacterial activities against Dickeya dadantii, which causes sweet potato stem and root rot disease occurring in major sweet potato planting areas in China. Ultraviolet–visible spectrometry and energy dispersive spectroscopy determined their physiochemical characteristics. Transmission electron microscopy, scanning electron microscopy, and X-ray diffraction spectroscopy revealed the nanoscale size and polymorphic crystalline structures of the ZnONPs and TiO2NPs. Fourier-transform infrared spectroscopy revealed their surface stabilization groups from the lemon fruit extract. In contrast to ZnO and TiO2, which had no antibacterial activity against D. dadantii, ZnONPs and TiO2NPs showed inhibitions on D. dadantii growth, swimming motility, biofilm formation, and maceration of sweet potato tuber slices. ZnONPs and TiO2NPs showed similar extents of antibacterial activities, which increased with the increase of nanoparticle concentrations, and inhibited about 60% of D. dadantii activities at the concentration of 50 µg∙mL−1. The green synthetic ZnONPs and TiO2NPs can be used to control the sweet potato soft rot disease by control of pathogen contamination of seed tubers.

The investigation on structural, optical and morphological behavior of pure and co-doped TiO2 nanoparticles developed via sol-gel approach for biological activity

In the present work, the effect of pure and different weight % of Cobalt (Co) doped titanium dioxide (TiO2) nanoparticles (NPs) were developed from sol–gel approach. The powder x-ray diffraction pattern of pure and 1%, 3%, and 5% Co-doped TiO2 NPs confirms the anatase phase structure and average crystallite size was obtained from 37, 38, 42 and 48 nm respectively for pure TiO2 and 1%, 3%, and 5% Co-doped TiO2. The spherical-like morphology was observed from the prepared materials which were primarily confirmed by the FESEM analysis. The optical behaviour of the developed material was investigated by UV–vis spectrum and energy band gab was achieved to be 1.95 eV, 3.96 eV, 3.89 eV and 3.62 eV respectively for pure TiO2, 1 wt%, 3 wt% and 5 wt% Co-doped TiO2 NP. The Kirby Bauer Agar Well Diffusion Assay method was employed to explore antimicrobial activity of nanosized pure and Co-doped TiO2 colloidal suspension against the test microorganisms two Gram positive bacteria (Staphylococcus aureus, Bacillus subtilis), two Gram negative Bacteria (Escherichia coli, Pseudomonas aeruginosa), and two fungi (Candida albicans, Aspergillus niger). It shows that the Co-doped TiO2 NPs inhibited the multiplication and growth of the above mentioned test bacteria and fungi. Antimicrobial activity was found against all tested microorganisms and confirmed that Co-doped TiO2 NPs possess higher antimicrobial activity at various concentration range of 25 μg, 50 μg, 75 μg and100 μg respectively for 1 wt%, 3 wt% and 5 wt% Co-doped TiO2 solutions.

Influence of PbS Quantum Dots-Doped TiO2 Nanotubes in TiO2 Film as an Electron Transport Layer for Enhanced Perovskite Solar Cell Performance

Lead sulfide quantum dots-doped titanium dioxide nanotubes (PbS QDs-doped TNTs) were successfully prepared by the hydrothermal and impregnation methods. A thin layer of titanium dioxide (TiO2) comprising of PbS QDs-doped TNTs was applied as an electron transport layer (ETL) in order to improve the planar perovskite solar cell efficiency. The role of incorporating a high surface area of one-dimensional nanotube structure of TiO2 in the conventional TiO2 layer provided a special unidirectional charge transport and a high charge collection. Moreover, doping PbS QDs onto the surface of TNTs modified the electronic and optical properties of the ETL by downshifting the conduction band of TiO2 from −4.22 to −4.58 eV, therefore promoting the driving force of an electron injection to the transparent conductive electrode. By varying the concentration of PbS QDs-doped TNTs dispersed in 2-butanol from 0.1 to 0.9 mg/mL, a concentration of 0.3 mg/mL PbS QDs-doped TNTs was the optimum concentration to be mixed with TiO2 solution for the ETL deposition. The best perovskite solar cell performance with the optimum loading of PbS QDs-doped TNTs provided 14.95% power conversion efficiency, which was increased from 12.82% obtained from the cell with pristine TiO2 film as ETL.