Synthesis and photocatalytic properties of Zn doped anatase TiO2 nanofibers

Zn²⁺ doped TiO₂ nanofibers were prepared by electrospinning followed by calcination. The results of TGA, FE-SEM, XRD and XPS indicated that the obtained nanofibers with diameter in range of 50–150 nm were composed of anatase TiO₂ phase and Zn²⁺ doping in TiO₂ did not distort the pristine crystal structure of TiO₂. Besides methylene blue (MB) was employed to investigate photocatalytic properties of the obtained samples. The results revealed that Zn²⁺ doped TiO₂ nanofibers had excellent photocatalytic activity, which was symbolized by an optimum photodegradation efficiency of 96.1% under Zn²⁺ doping concentration of 2 at.%. The photocatalytic efficiency of 2 at.% Zn²⁺ doped TiO₂ nanofibers still exceeded 95% after using for five times.     

Formation of TiO2 nano-fiber doped with Gd3+ and its photocatalytic activity

Titanium dioxide (TiO₂) nano-fibers doped with Gd³⁺ were synthesized by two-step synthesis method. The formed fibers were visualized from transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the average diameter of the TiO₂ nano-fibers was 60–80 nm and the length of fibers was in the range of 6–7 μm. The TiO₂ nano-fibers doped with Gd³⁺ heat treated in glycerol solvent had smaller crystal size than those without heat treatment. However, the size of TiO₂ nano-fibers decreased with increasing the heating temperature. The results obtained in the photocatalytic degradation of methyl orange indicated that the photocatalytic activity of the TiO₂ nano-fibers doped with Gd³⁺ appeared a little reduction relative to that of TiO₂ nanopowders.     

Photocatalytic activity of TiO2 doped with Zn2+ and V5+ transition metal ions: Influence of crystallite size and dopant electronic configuration on photocatalytic activity

Anatase TiO₂ was prepared by sol–gel method through the hydrolysis of titanium tetrachloride and doped with transition metal ions like V⁵⁺ and Zn²⁺. The photocatalysts were characterized by various analytical techniques. Powder X-ray diffraction studies revealed only anatase phase for the doped samples. The band gap absorption for the doped samples showed red shift to the visible region (～456 nm) as confirmed by UV–vis absorption spectroscopy and diffuse reflectance spectral studies. The surface area of the Zn²⁺ doped samples were higher than the V⁵⁺ doped samples as observed by BET surface area measurements due to their smaller crystallite size. Scanning electron microscopy showed almost similar morphology, while energy dispersive X-ray analysis confirmed the presence of dopant in the TiO₂ matrix. The photocatalytic activities of these catalysts were tested for the degradation of Congo Red under solar light. Although both the doped samples showed similar red shift in the band gap, Zn²⁺ (0.06 at.%) doped TiO₂ showed enhanced activity and its efficiency was five fold higher compared to Degussa P-25 TiO₂. This enhanced activity was attributed to smaller crystallite size and larger surface area. Further completely filled stable electronic configuration (d¹⁰) of Zn²⁺ shallowly traps the charge carriers and detraps the same to the surface adsorbed species thereby accelerating the interfacial charge transfer process.     

Synthesis and photochemical properties of Cu2+ doped layered hydrogen titanate

Cu²⁺ doped layered hydrogen titanate was prepared by the calcination of K₂CO₃, TiO₂ and CuO mixtures with the K₂CO₃:TiO₂:CuO molar ratio of 1:2.5(1−x):2.5x at 1200°C for 5 h followed by an ion-exchange reaction in 1 M HCl solution. The crystalline phase changed from monoclinic hydrogen tetratitanate to an orthorhombic lepidocrocite-type hydrogen titanate by increasing the amount of Cu²⁺ doped. Both compounds could be excited by visible light irradiation (λ>400 nm) and were capable of hydrogen gas evolution from an aqueous methanol solution, where the photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was slightly greater than that of Cu²⁺ doped lepidocrocite-type hydrogen titanate. The photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was enhanced by constructing Pt and TiO₂ pillars in the interlayer, and the incorporation of Pt in Cu²⁺ doped hydrogen tetratitanate enabled the cleavage of water into hydrogen and oxygen by irradiating visible light (λ>400 nm) without a sacrificial hole acceptor.     

Improving 1.54 μm emission by inducting Ti ion in Er3+/Yb3+ codoped phosphate glass ceramic

Er³⁺/Yb³⁺ doped phosphate glasses were prepared by high-temperature melting method. Under 975 nm excitation, the intensity of the visible light in the sample doped with TiO₂ is weaker compared to that of the sample un-doped with TiO₂ However, the intensity of the 1540 nm emission in the sample doped with TiO₂ is stronger than that in the sample un-doped with TiO₂ The sample can efficiently improve the 1540 nm emission by absorbing visible light.     

Synthesis of novel Cu doped anatase TiO<Subscript>2</Subscript> catalysts and assessment of the influence of Nb concentration on the photocatalytic and electrochemical properties

In the present study, Cu doped (Ti_0.8Cu_xO_2?x/2) and (Cu, Nb) co-doped (Ti_0.8Cu_x?y Nb_yO_2?(x?y/2+y)) TiO₂ photocatalysts were fabricated by sol–gel method. The catalysts were polycrystalline in nature with preferential orientation along (101) plane answering to anatase phase of TiO₂. Higher Nb concentration results in the formation of secondary phase (Nb₂O₅). A decrease in average crystallite size was noticed with the addition of Nb concentration in Cu doped TiO₂ photocatalyst. The formation of anatase phase was also fixed by Raman spectra. The TEM photograph confirmed the co-doped TiO₂ photocatalyst in nanometer range of about 15 nm and the particles were in hexagonal shape. The doping of Nb⁵⁺ ions inspired a shift in the absorption threshold towards the visible spectral range (red shift) compared to Cu doped TiO₂ catalyst. The photocatalysts have direct bandgaps of 3.253 to 2.974 eV. Semiconducting properties were investigated through electrochemical impedance spectroscopy. The results indicate that the presence of Nb⁵⁺ ions into Cu doped TiO₂ has enhanced the efficiency of electrochemical conductivity. Photocatalytic performance was assessed from the sample degradation by illuminating methylene blue dye under visible light exposure. It is found that TCN3 photocatalyst bleaches MB much faster than all others. Also it exhibits great improvement of photocatalytic activity (96.86%) within 120 min. The photocatalytic degradation process is explained using the pseudo first order kinetics and it fits well with higher correlation coefficient. All these analyses elucidate that the incorporation of Nb⁵⁺ ions might tune the structural, optical, electrochemical and phocatalytic properties of Cu doped TiO₂ photocatalysts.     

The gas sensitivity of nano TiO2-SnO2 film doped with Cd(II) ion

The nanocomposite oxide (0.2TiO₂-0.8SnO₂) doped with Cd²⁺ powder have been prepared and characterized by XRD and their gas-sensing sensitivity were characterized using gas sensing measurement. Experimental results show that, bicomponent nano anatase TiO₂ and rutile SnO₂ particulate thick film doped with Cd²⁺ behaves with good sensitivity to formaldehyde gas of 200 ppm in the air, and the optimum sensing temperature was reduced from 360 °C to 320 °C compared with the undoped Cd²⁺ thick film. The gas sensing thick films doped with Cd²⁺ also show good selectivity to formaldehyde among benzene, toluene, xylene and ammonia as disturbed gas and could be effectively used as an indoor formaldehyde sensor.     

Microstructures and photo-catalytic properties of B3+ and F− co-doped TiO2 films

The nano-crystalline B³⁺ and F^? co-doped titanium dioxide films were successfully prepared by the improved sol–gel process. The as-prepared specimens were characterised using X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FE-SEM), the Brunauer–Emmett–Teller (BET) surface area, X-ray photo-electron spectroscopy, photoluminescence spectra and UV–Vis diffuse reflectance spectroscopy. The photo-catalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. The results of XRD, FE-SEM and BET analysis indicated that the TiO₂ films were composed of nano-particles. B³⁺ and F^? co-doping could obviously not only suppress the formation of brookite phase but also inhibit the transformation of anatase to rutile at high temperature. Diffuse reflectance measurements showed that co-doping could clearly extend the absorbance spectra of TiO₂ into visible region. Compared with pure TiO₂, B³⁺ doped or F^? doped TiO₂ film, the B³⁺ and F^? co-doped TiO₂ film exhibited excellent photo-catalytic activity. It is believed that the surface microstructure of the films and the doping methods of the two ions are responsible for improving the photo-catalytic activity.     

Visible light-active iron-doped anatase nanocrystallites and their self-cleaning property

To extend and improve photocatalytic activity of TiO₂ in UV-visible region and reduce electron-hole recombination, Fe³⁺ doped anatase nanocrystallites were synthesized by a sol-gel process in an aqueous solution at a temperature of 60 °C with the addition of Fe³⁺ dopant. The Fe³⁺ dopant with various doping level was investigated. Superior self-cleaning performance was achieved for the optimal doped anatase nanocrystals when compared to that of the pure TiO₂ through the evaluation of colorant decomposition, the degradation of a coffee stain, and a red wine stain under UV and visible light irradiation. The study demonstrated that it is feasible to apply Fe³⁺ doped anatase nanocrystallites to materials with low thermal resistance, such as textiles and other biomaterials as the doped anatase nanocrystals were formed during the sol-gel process without the need of any post-thermal treatment and the use of aqueous based sol-gel process instead of previously reported solvent-based ones is more environmentally friendly and suitable for large-scale fabrication.     

Enhancement of titania by doping rare earth for photodegradation of organic dye (Direct Blue)

Lanthanide ions (La³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, and Yb³⁺)/doped TiO₂ nanoparticles were successfully synthesized by sol–gel method. Their photocatalytic activities were evaluated using Direct Blue dye (DB53) as a decomposition objective. The structural features of TiO₂ and lanthanide ions/TiO₂ were investigated by XRD, SEM, UV-diffuse reflectance, and nitrogen adsorption measurements. Our findings indicated that XRD data characteristic anatase phase reflections and also XRD analysis showed that lanthanides phase was not observed on Lanthanide ions/TiO₂. The results indicated that Gd³⁺/TiO₂ has the lowest bandgap and particle size and also the highest surface area and pore volume (V_p) as well. Lanthanide ions can enhance the photocatalytic activity of TiO₂ to some extent as compared with pure TiO₂ and it was found that Gd³⁺/TiO₂ is the most effective photocatalyst. The photocatalytic tests indicate that at the optimum conditions; illumination time 40 min, pH ∼4, 0.3 g/L photocatalyst loading and 100 ppm DB53; the dye removal efficiency was 100%. Details of the synthesis procedure and results of the characterization studies of the produced lanthanide ions/TiO₂ are presented in this paper.     

Photocatalytic Zn-doped TiO2 films prepared by DC reactive magnetron sputtering

Zn-doped TiO₂ films were prepared by means of pulsed DC reactive magnetron sputtering method using Ti and Zn mixed target. The deposition condition was optimized to produce uniform and transparent TiO₂ films. Titanium was in the Ti⁴⁺ oxidation state in all Zn-doped TiO₂ films. The zinc oxide deposited on the substrate was in the fully oxidized state of ZnO. Increase of zinc concentration inhibited the crystal growth in the TiO₂ films. The surface morphology gradually changed from crystalline to amorphous along with the increase of doped zinc concentration. The optical transmittances of these films decreased only slightly with increasing zinc concentration due to very similar band edges of ZnO and anatase TiO₂. The doped ZnO had weak influence on light absorption of the TiO₂ films. When zinc concentration was very low (<1 at%), the photocatalytic activities of the doped films had nearly no difference from that of pure TiO₂ film. Photocatalytic activities decreased obviously in the films containing high amount of zinc oxide.     

Preparation of doped TiO2 nanofiber membranes through electrospinning and their application for photocatalytic degradation of malachite green

Fe³⁺ doped TiO₂ composite nanofiber membranes and pure TiO₂ nanofiber membranes were prepared through electrospinning, and were applied to the photocatalytic degradation of malachite green (MG) in aqueous solutions under simulated sunlight. The effects of ferric ion content, initial concentration of MG, photocatalyst loading, and recycling behavior were studied. Microscopic characterization showed that the products have fiber morphology with bent property and favorable continuity. The degradation results showed that TiO₂ nanofiber membranes containing 0.8 mol% Fe³⁺ performed the best photocatalytic activity against MG under identical light irradiation. The TiO₂:Fe³⁺ composite nanofiber membranes maintained their photocatalytic efficiency through seven recycling processes.     

Effects of the co-addition of Zn and sodium dodecylbenzenesulfonate on photocatalytic activity and wetting performance of anatase TiO2 nanoparticle films

In this paper, doped and undoped anatase TiO₂ nanoparticle films on indium tin oxide glasses have been fabricated by spin coating sols containing Zn²⁺ or Zn²⁺ and sodium dodecylbenzenesulfonate (DBS), respectively. The effects of the co-addition of Zn²⁺ and DBS on the photocatalysis performance and wetting properties of the resulting TiO₂ nanoparticle films were investigated. The results showed that the addition of Zn²⁺ improved both the photocatalytic activity and the hydrophilicity, which was attributed to surface oxygen vacancies. The co-addition of Zn²⁺ and DBS resulted in an important increase of the surface roughness, resulting in films showing a superhydrophilic behavior. However, the photocatalytic activity was slightly decreased by co-adding Zn²⁺ and DBS. The DBS addition resulted in changes in the surface microstructure of the TiO₂ films, changing the photocatalytic activity and wetting performance.     

Enhanced optical and hydrophilic properties of Si and Cd co-doped TiO<Subscript>2</Subscript> thin films

In this study, preparation of Si and Cd co doped (5 mol% Si and 5–20 mol% Cd) TiO₂ dip-coated thin films on glass substrates via sol–gel process have been investigated. The samples were characterized by X-ray diffraction (XRD) and Scanning electron microscopy analysis after heat treatments. XRD results suggested that adding dopants has a great effect on crystallinity and particle size of TiO₂. Titania rutile phase formation was inhibited by Si⁴⁺ and promoted by Cd²⁺ doping. But the effect of Cd doped appeared at high concentration. Accordingly, the thin films showed various water contact angles. The water contact angles changed from 69.0° to 9.6° by changing the content of Cd doped.     

Photoluminescence of TiO2 films co-doped with Tb/ Gdand energy transfer from TiO2/Gd to Tb ions

Nanometer TiO₂ thin films doped with different concentration of Tb were prepared by sol-gel method and characterized by X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. XRD results show preferentially oriented (101) anatase films. TEM image indicates that the TiO₂ films consist of TiO₂ grains with diameter about 15 nm. Under room temperature, strong visible luminescence of Tb³⁺ ions due to intra-4f shell transitions are obtained and the PL intensity is found to have a well matching relation with the doping concentration of Tb³⁺ ions. Concentration quenching of PL occurs when Tb³⁺ concentration exceeds a certain value (9.2 mol%). Furthermore, the luminescence intensity is improved obviously after co-doping with Gd³⁺ ions because of the sensitization effects of Gd³⁺ ions to Tb³⁺ ions in TiO₂ system. The energy transfer mechanism from TiO₂ and Gd³⁺ ions to Tb³⁺ ions was proposed.     

Nanocrystalline sol–gel TiO2–SnO2 coatings: Preparation,characterization and photo-catalytic performance

In this study, preparation of SnO₂ (0–30 mol% SnO₂)–TiO₂ dip-coated thin films on glazed porcelain substrates via sol–gel process has been investigated. The effects of SnO₂ on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films were examined by atomic force microscopy and X-ray photoelectron spectroscopy. XRD patterns showed an increase in peak intensities of the rutile crystalline phase by increasing the SnO₂ content. The prepared Sn doped TiO₂ photo-catalyst films showed optical absorption in the visible light area exhibited excellent photo-catalytic ability for the degradation of methylene blue under visible light irradiation. Best photo-catalytic activity of Sn doped TiO₂ thin films was measured in the TiO₂–15 mol% SnO₂ sample by the Sn⁴⁺ dopants presented substitution Ti⁴⁺ into the lattice of TiO₂ increasing the surface oxygen vacancies and the surface hydroxyl groups.     

Structural and dielectric studies of Eu3+/Ag nanocrystallites: SiO2–TiO2 matrices

Silver nanocrystallites/Eu³⁺ doped SiO₂–TiO₂ matrices were synthesised through sol–gel route and the structural and dielectric properties of the matrices were studied. Structural characterizations were done using EDX, XRD, FTIR, AFM and TEM measurements. The TEM and XRD measurements confirm the presence of Ag and TiO₂ nanocrystals. The dielectric and electrical conductivity studies of the samples were done for a frequency range of 100 Hz–2 MHz. The conductivity variation with the Ag content in the Eu³⁺ doped SiO₂–TiO₂ system has been explained by correlating the presence of ionic contribution to the electrical conductivity process. Also, the frequency dependence of dielectric constant and conductivity were studied. The Cole–Cole parameters were calculated and the semicircles observed in the plots indicate a single relaxation process. This behaviour can be modelled by an equivalent parallel RC circuit.     

Multifunctional Gadolinium‐Doped Mesoporous TiO2 Nanobeads: Photoluminescence,Enhanced Spin Relaxation,and Reactive Oxygen Species Photogeneration,Beneficial for Cancer Diagnosis and Treatment

Materials with controllable multifunctional abilities for optical imaging (OI) and magnetic resonant imaging (MRI) that also can be used in photodynamic therapy are very interesting for future applications. Mesoporous TiO₂ sub‐micrometer particles are doped with gadolinium to improve photoluminescence functionality and spin relaxation for MRI, with the added benefit of enhanced generation of reactive oxygen species (ROS). The Gd‐doped TiO₂ exhibits red emission at 637 nm that is beneficial for OI and significantly improves MRI relaxation times, with a beneficial decrease in spin–lattice and spin–spin relaxation times. Density functional theory calculations show that Gd³⁺ ions introduce impurity energy levels inside the bandgap of anatase TiO₂, and also create dipoles that are beneficial for charge separation and decreased electron–hole recombination in the doped lattice. The Gd‐doped TiO₂ nanobeads (NBs) show enhanced ability for ROS monitored via ^?OH radical photogeneration, in comparison with undoped TiO₂ nanobeads and TiO₂ P25, for Gd‐doping up to 10%. Cellular internalization and biocompatibility of TiO₂@x Gd NBs are tested in vitro on MG‐63 human osteosarcoma cells, showing full biocompatibility. After photoactivation of the particles, anticancer trace by means of ROS photogeneration is observed just after 3 min irradiation.     

Structural properties of TiO2–WO3 thin films prepared by r.f. sputtering

TiO₂–WO₃ thin films were prepared by radio frequency (r.f.) reactive sputtering from metallic target. Structural and morphological properties of the thin films have been studied through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The influence of the annealing on the phase composition TiO₂–WO₃ system was studied. The binding energies of titanium and tungsten are characteristic for Ti⁴⁺ and W⁶⁺. The influence of tungsten on anatase–rutile phase transition in TiO₂ was observed. The structural modeling has been performed to account the preferred orientation in tungsten doped titanium oxide.     

Preparation, characterization and photocatalytic activity of in situ Fe-doped TiO2 thin films

Fe-doped TiO₂ thin films were prepared in situ on stainless steel substrates by liquid phase deposition, followed by calcination at various temperatures. It was found that some Fe³⁺ ions were in situ doped into the TiO₂ thin films. At 400 °C, the film became photoactive due to the formation of anatase phase. At 500 °C, the film showed the highest photocatalytic activity due to an optimal Fe³⁺ ion concentration in the film. At 900 °C, the photocatalytic activity of the films decreased significantly due to the further increase of Fe³⁺ ion concentration, the formation of rutile phase and the sintering and growth of TiO₂ crystallites.