(N, F)-codoped TiO2 Nanocrystals as Visible Light-activated Photocatalyst

(N, F)-codoped anatase TiO₂ nanocrystals with active visible light response were prepared by using a simple sol-gel approach. X-ray photoelectron spectroscopy measurements suggested that the substitutional N and F species replaced the lattice oxygen atoms in TiO₂ nanocrystals. Such nanocrystals showed strong absorption from 400 to 550 nm, which was mainly induced by nitrogen doping. The phase transformation from anatase to rutile was hindered by fluorine doping at high calcination temperatures, which was verified by XRD patterns. The N2 adsorption-desorption isotherms revealed the absence of mesopores in these nanocrystals. The (N, F)- codoped TiO₂ nanocrystals showed satisfying photocatalytic activity on the photo-degradation of methylene blue under visible light.     

Hydrothermal preparation and characterization of TiO2:AC composites

A new photocatalyst titania:activated carbon (TiO₂:AC) composite was prepared by impregnating anatase type TiO₂ nanoparticulates onto the activated carbon surface through a mild hydrothermal route. A varied ratio of TiO₂ to AC was considered for impregnation. As-prepared TiO₂:AC composite was characterized by various techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), BET surface area and positron annihilation lifetime spectroscopy (PALS). Powder XRD results showed the persisting nature of anatase phase of TiO₂ deposited on the activated carbon surface. The BET, FTIR and PALS results revealed the impregnation threshold. The TiO₂ particulates were well adhered and uniformly dispersed on the carbon surface as confirmed by SEM.     

Structural,morphological and photocatalytic characterisations of Ag-coated anatase TiO2 fabricated by the sol–gel dip-coating method

This study reports on the synthesis, characterisation and environmental applications of immobilised Titanium dioxide (TiO₂) as photocatalyst. Nanostructured thin films have been prepared on glass substrates using a layer-by-layer dip-coating method. The crystalline phase and surface morphology of the thin films were investigated by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM), respectively. The XRD results show that the TiO₂ thin films crystallise in anatase phase and we have found that the thin films consist of titanium dioxide nanocrystals. SEM shows that the nanoparticles are sintered together to form a compact structure and TiO₂ particles coated with silver nanoclusters were observed. Ag-coated TiO₂ films demonstrated photocatalysis performance when irradiated, and the Ag carrier further showed an electron-scavenging ability to mitigate electron–hole pair recombination, which can improve the photocatalytic efficiency. With the oxidisation and electron-scavenging ability of Ag and the photocatalysis ability of TiO₂, Ag-coated TiO₂ can decolour methyl orange (MO) more than bare TiO₂. It is a new approach to form Ag-coated TiO₂ nanoparticles with a simple system and non-toxic materials. The high photocatalytic effect of Ag-coated TiO₂ nanoparticles on pollutant (MO) suggests that it may have a promising future for water and wastewater treatments.     

Controlled synthesis of anatase TiO2 octahedra with enhanced photocatalytic activity

Titanium dioxide (TiO₂) nanocrystals with specific exposed crystal facet have attracted considerable interest due to their promising applications in the fields of energy and environment. In this paper, we report on a simple solvothermal approach for the synthesis of anatase TiO₂ octahedra with high yield, using titanium(IV) sulfate and hydrazine hydrate as the starting materials. The formation mechanism of anatase TiO₂ octahedra is suggested. The samples were characterized with XRD, Raman, SEM, TEM, FTIR, XPS, and UV/vis techniques, and further tested as a candidate in photocatalysis to decompose methyl orange in aqueous solution at room temperature. The results show that SO₄²⁻ ions not only benefit the formation of octahedral nanocrystals, but also inhibit nitrogen doping into TiO₂ matrix. More importantly, it is found that the octahedral TiO₂ nanocrystals show enhanced photocatalytic activity compared to TiO₂ P25 and anatase TiO₂ counterparts.     

A novel approach to synthesis of high-dispersed anatase titania nanocrystals

A novel approach was employed in the synthesis of high-dispersed anatase titania (TiO₂) nanocrystals by sol–gel process with NH₄NO₃ (AN) as solid substrates. Further calcination was conducted after the hydrous TiO₂ nanoparticles were adsorbed onto the surface of AN particles. The products were investigated by TGA, XRD, and TEM. The results indicated that AN was melting and decomposing during the calcining process, which was very important to inhibit the agglomeration of anatase TiO₂ nanocrystals. The highly dispersed anatase TiO₂ nanocrystals were in needle-shape having lengths about 16–20 nm and diameter of 6–9 nm.     

Facile synthesis of rice-like anatase TiO2 nanocrystals

Rice-like anatase TiO₂ nanocrystals have been synthesized by hydrothermal treating Ti(OH)₃ precursor in deionized water, which is easy to form in-situ a stable TiO₂ aqueous dispersion and no post-synthetic purification process is required. The influences of synthetic parameters, such as reaction time and pH value, on the morphologies of the resulting nanocrystals have been investigated. It is found that the crystallinity and sizes of TiO₂ nanocrystals increase with the reaction time increased. The pH value is important for controlling the sizes and shapes of TiO₂ nanocrystals. As pH value increases from 2 to 11, spherical, rice-like, and rod-like TiO₂ nanocrystals are obtained, respectively. The formation mechanism of rice-like anatase TiO₂ nanocrystals is supposed to be a hydrothermal crystallization and Ostwald ripening process.     

Synthesis and spectroscopic characterization of nanostructured anatase titania: A photocatalyst

Nanocrystalline TiO₂ was synthesized by the sol-gel process by controlling the crystallite size through calcination. The resulting nanocrystals were characterized using XRD, FT-Raman, SEM/EDX, DSC/TGA and UV–Vis spectroscopic techniques. XRD patterns confirmed the presence of only pure 100% anatase phase TiO₂. The surface morphology of the nanotitania was evaluated with Scanning Electron Microscopy. The purity of the sol-gel-derived TiO₂ was confirmed through EDX measurements. The band gap of the nanotitania was found to be 3.6 eV from UV–Vis measurements. The pHzpc of the titania sample was measured as 5.90.     

Synthesis of highly-active single-crystalline TiO2 nanorods and its application in environmental photocatalysis

Highly-active anatase TiO₂ nanorods have been successfully synthesized via a simple two-step method, hydrothermal treatment of anatase/rutile titanium dioxide nanoparticle powder in a composite-hydroxide eutectic system of 1:1 M KOH/NaOH, followed by acid post-treatment. The morphology and crystalline structure of the obtained nanorods were characterized using XRD, TEM, SEM/EDX and BET surface area analyzer. The obtained TiO₂ nanorods have a good crystallinity and a size distribution (about 4-16 nm); with the dimensions of 200-300 nm length and of 30-50 nm diameter. Compared with its precursor anatase/rutile TiO₂ nanoparticles and the titanate nanotubes, the pure anatase TiO₂ nanorods have a large specific surface area with a mesoporous structure. The photocatalytic performance of the prepared nanorods was tested in the degradation of the commercial Cibacrown Red (FN-R) textile dye, under UV irradiation. Single-crystalline anatase TiO₂ nanorods are more efficient for the dye removal.     

An easier method of preparation of mesoporous anatase TiO2 nanoparticles via ultrasonic irradiation

Mesoporous anatase TiO₂ nanopowder was synthesised by the sol–gel method using ultrasonic irradiation. This method is simple and faster for the synthesis of phase pure mesoporous anatase TiO₂ nanopowder. The product is characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron spectroscopy (TEM), thermo gravimetric analysis, Brunauer–Emmett–Teller (BET) surface area, UV–visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy. Analysis of XRD patterns, SEM and TEM image shows that the average particles size is of 19.9 nm and has an anatase structure. The mesoporous nature was determined by the BET method using the Barrett–Joyner–Halenda (BJH) model.     

Sonochemical preparation of TiO2 nanoparticles in the ionic liquid 1-(3-hydroxypropyl)-3-methylimidazolium-bis(trifluoromethylsulfonyl)amide

Spherical shaped anatase nanoparticles (ø 5 nm) have been synthesized in the ionic liquid 1-(3-hydroxypropyl)-3-methylimidazolium-bis(trifluoromethanesulfonyl)amide from titanium tetraisopropoxide by ultrasound assisted synthesis under ambient conditions. XRD, EDX, TEM, XPS, Raman, UV–vis, PL and BET measurements have been employed for characterization of the nanostructure of as-prepared TiO₂. XRD and Raman measurements both show that the obtained material is crystalline with anatase structure. The morphology of TiO₂ nanoparticles was characterized by transmission electron microscopy (TEM). The bandgap of the TiO₂ nanocrystals estimated from XRD and UV–vis measurements is about 3.3 eV. The surface area of a typical sample is 177 m² g⁻¹. The synthesized anatase nanocrystals show good photocatalytic activity in the degradation of methylorange.     

Glycerol as an efficient mesopore-controlling agent for synthesis of mesoporous-assembled TiO2 nanocrystals and their remarkable photocatalytic H2 production activity

In this work, the mesoporous-assembled TiO₂ nanocrystals were successfully synthesized by a modified sol–gel process under mild conditions with the aid of glycerol, which is a main by-product from biodiesel production via the transesterification of vegetable oils. The synthesized TiO₂ nanocrystals were characterized by various techniques, i.e. N₂ adsorption–desorption, SEM, high resolution TEM, and XRD. The characterization results clearly showed that the glycerol could behave as an efficient mesopore-controlling agent, which induced the mesoporous-assembled characteristic of the synthesized TiO₂ nanocrystals with very narrow pore size distribution. The synthesized mesoporous-assembled TiO₂ nanocrystals were applied for hydrogen production from the photocatalytic water splitting. The photocatalytic activity results revealed that the synthesized mesoporous-assembled TiO₂ nanocrystals possessed much higher hydrogen production activity than the commercially available P-25 TiO₂ and ST-01 TiO₂ powders.     

TiO2 nanowires sensitized with CdS quantum dots and the surface photovoltage properties

TiO₂ nanowires prepared by thermal annealing of anodized Ti foil were sensitized with CdS quantum dots (QDs) via chemical bath deposition (CBD). Microstructural characterizations by SEM, TEM and XRD show that the CdS nanocrystals with the cubic structure have intimate contact to the TiO₂ nanowires. The amount of CdS QDs can be controlled by varying the CBD cycles. The experiment results demonstrate that the surface photovoltage (SPV) response intensity was significantly enhanced and the surface photovoltage response region was also expanded obviously for the TiO₂ NWs sensitized by CdS QDs.     

Synthesis and characterization of pure anatase TiO<Subscript>2</Subscript> nanoparticles

Pure anatase TiO₂ nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO₂ nanoparticles were porous structure. The XRD patterns indicated that TiO₂ after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.     

Synthesis and photocatalytic oxidation properties of titania hollow spheres

The hollow spheres of anatase TiO₂ with higher photocatalytic activity have been fabricated by spherical CaCO₃ nanoparticles as a template, and titanium sulfate (Ti(SO₄)₂) as a precursor, and the CaCO₃ templates were dissolved subsequently in dilute HNO₃ solution. The TiO₂ hollow spheres samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and N₂ adsorption-desorption isotherms. The characterization results indicate that as prepared TiO₂ hollow spheres sample was transformed to anatase phase in calcined at 400 °C, and the anatase TiO₂ hollow spheres have a higher specific surface area and show much better photocatalytic activity than commercial P25 in the photodegradation of Rhodamine B under the UV irradiation.     

The effects of synthesis procedures on the structure and morphology of multiwalled carbon nanotubes (MWNTs)/titania (TiO2) nanocomposites prepared by hydrothermal method

The nanocomposites of multiwalled carbon nanotubes (MWNTs)/titania (TiO₂) were prepared by direct growth of TiO₂ nanocrystals onto carboxyl-modified MWNTs under hydrothermal condition. The structure and morphology of TiO₂ nanocrystals growing on MWNTs were tuned by adjusting acidity, reaction temperature, and reactant ratio. The results showed that a uniform layer of anatase TiO₂ nanocrystals on MWNTs could be achieved at proper synthesis parameters. Flowerlike assemblage of rutile TiO₂ nanocrystals was dispersed on MWNTs. The formation mechanism of MWNTs/TiO₂ nanocomposites was further provided.     

Preparation and photocatalytic activity of anatase TiO2 nanocrystallites with high thermal stability

Anatase TiO₂ nanocrystallites were prepared from TiCl₄ with addition of aqueous ammonia by changing Ti(OH)₄ hydrogel into its corresponding alcogel followed by supercritical drying in ethanol medium. The as-prepared TiO₂ was characterized by XRD, TG and BET. The results show that the prepared anatase TiO₂ has remarkable high thermal stability. The anatase structure of the prepared TiO₂ is maintained even after calcination up to temperatures as high as 800 °C. The photocatalytic activity of the prepared TiO₂ calcined at 800 °C in degradation of reactive brilliant red X-3B is comparable to commercially available nanosized P25 TiO₂.     

Low temperature facile synthesis of anatase TiO2 coated multiwalled carbon nanotube nanocomposites

Anatase TiO₂ coated multiwalled carbon nanotube (MWNT) nanocomposites were prepared by combining the sol-gel method with a self assembly technique at a low temperature. XRD, TEM, FTIR and XPS spectra were applied to characterize the crystal phase, microstructure, and other physicochemical properties of the sample. The results showed that MWNTs were covered with a 12-20 nm thickness layer of anatase TiO₂ or surrounded by a 30 -290 nm thickness coating of anatase TiO₂. The layer or coating is constructed of TiO₂ nanoparticles about 5.8 nm. Furthermore, as-prepared composite was rich in surface hydroxyl groups.     

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.     

Preparation of anatase nanocrystals deposited on hydroxyapatite by hydrothermal treatment

TiO₂-deposited hydroxyapatite (HAp) crystals have been successfully synthesized by hydrothermal treatment of nearly neutral suspension of HAp powders in 10 vol.% of TAS-FINE™ (Titanium amine complex) solutions at 120 or 180 °C. Resultant products were characterized by XRD, SEM–EDX, Vis-Raman and TEM. SEM and TEM observation showed that small rodlike TiO₂, identified as anatase crystals of 100–150 nm in length, were deposited on HAp plates/crystals. The anatase crystals seem to be formed by heterogeneous nucleation on the surfaces of HAp crystals. A higher temperature and a longer reaction period promoted the cystallization of anatase TiO₂.     

Synthesis and characterization of anatase and rutile TiO2 nanorods by template-assisted method

Well-aligned anatase and rutile TiO₂ nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method. The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The XRD results indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time from 0.2 to 10 h.