Preparation of nanosized TiO2 particles via ultrasonic irradiation and their photocatalytic activity on the decomposition of 4-nitrophenol

TiO₂ nanoparticles were prepared by hydrolysis of TTIP (titanium tetraisopropoxide) using an ultrasonication technique coupled with a sol-gel method. The physical properties of nanosized TiO₂ were investigated. The photocatalytic degradation of 4-nitrophenol was studied by using a batch reactor in the presence of UV light. The crystallite size of the anatase phase is increased with an increase of R_EtOH ratio (EtOH/H₂O molar ratio). The particles’ crystallite size prepared with and without ultrasonic irradiation is marginally different. Those particles prepared with ultrasonic irradiation show a higher activity on the photocatalytic decomposition of 4-nitrophenol compared to those prepared without ultrasonic irradiation. The photocatalytic activity decreases with an increase of R_EtOH ratio. In addition, the photocatalytic activity shows the highest value on the titania particle calcined at 500 ‡C. This paper was presented at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November 3 and 4,2004.     

Anatase-Titania Templated by Nanofibrillated Cellulose and Photocatalytic Degradation for Methyl Orange

In this work, novel titania (TiO₂) nanoparticles were designed as a high performance photocatalyst. It was obtained by a simple method of dispersing nanofibrillated cellulose (NFC) onto the surface of titanium tetrachloride (TiCl₄), inducing crystallization and removing NFC templates. Under UV light irradiation, The TiO₂ nanoparticles displayed excellent photocatalytic activity for the decomposition of methyl orange solution. It was found that TiO₂ after calcination had a more efficiency than that before calcination. The optimum calcination temperature for the removal of NFC templates was 300?°C. Methyl orange solution had been remarkably degraded by TiO₂ nanoparticles when the mass ratio of TiCl₄ and NFC was 12:1. These results indicate that the TiO₂ nanopartilces can be easily applied in the field of wastewater treatment.     

Preparation, Characterization and Photocatalytic Activities of F-doped TiO2 Nanotubes

F-doped TiO₂ nanotubes were prepared by impregnation method. The prepared catalysts were characterized by XRD, TEM, and XPS. The photocatalytic activity of F-doped TiO₂ nanotubes was evaluated through the photodegradation of aqueous methyl orange. The experiments demonstrated that the F-doped TiO₂ nanotubes calcined at 300 °C possessed the best photocatalytic activity. Compared with pure TiO₂ nanotubes, the doping with F⁻ significantly enhanced the photocatalytic efficiency. The high photocatalytic activity was ascribed to several beneficial effects produced by F-doping: creation of oxygen vacancies, presence of Ti³⁺, and so on. An erratum to this article can be found at     

Photocatalytic degradation of methylene blue and acetaldehyde by TiO<Subscript>2</Subscript>/glaze coated porous red clay tile

Nanosized TiO₂ sol synthesized by sol-gel method was successfully coated on the porous red clay tile (PRC tile) with micrometer sized pores. PRC tile was first coated with a low-firing glaze (glaze-coated PRC tile) and then TiO₂ sol was coated on the glaze layer. A low-fired glaze was prepared at various blending ratios with frit and feldspar, and a blending ratio glazed at 700 °C was selected as an optimum condition. Then TiO₂ sol synthesized from TTIP was dip-coated on the glazed layer (TiO₂/glaze-coated PRC tile), and it was calcined again at 500 °C. Here, these optimum calcination temperatures were selected to derive a strong bonding by a partial sintering between TiO₂ sol particles and glaze layer. Photocatalytic activity on the TiO₂/glaze-coated PRC tile was evaluated by the extent of photocatalytic degradation of methylene blue and acetaldehyde. Methylene blue with the high concentration of 150 mg/l on the surface of TiO₂/glaze-coated PRC tile was almost photodegraded within 5 hours under the condition of average UV intensity of 0.275 mW/cm₂, while no photodegradation reaction of methylene blue occurred on the glaze-coated PRC tile without TiO₂. Another photocatalytic activity was also evaluated by measuring the extent of photocatalytic degradation of gaseous acetaldehyde. The photodegradation efficiency in TiO₂/glaze-coated PRC tile showed about 77% photocatalytic degradation of acetaldehyde from 45,480 mg/l to 10,536 mg/l after the UV irradiation of 14 hours, but only about 16% in the case of the glaze-coated PRC tile.     

Crystallization and Photoactivity of Tio2 Films Formed on Soda Lime Glass by a Sol-Gel Dip-Coating Process

Transparent nanophase TiO₂ thin films on soda lime glass were prepared from titanium tetraisopropoxide (TTIP) by a sol-gel dip-coating method. The TiO₂ films had amorphous phase up to 400°C and anatase phase at 500°C. The amorphous TiO₂ films obtained at 300–400°C showed considerable photoactivity for the degradation of formic acid. The photoactivity of the TiO₂ films was enhanced with increasing calcination temperature from 300° to 500°C. The crystallinity of the anatase films at 500°C was improved with increasing calcination time up to 2 h and reduced with a further increase in calcination time to 4 h due to the significant formation of sodium titanate phase as a result of sodium diffusion. The four-time-dipping anatase films at 500°C exhibited the greatest photoactivity at the calcination time of 2 h. Sodium diffusion into TiO₂ films was retarded by a SiO₂ underlayer of 50 nm in thickness.     

Photocatalytic degradation of methylene blue with TiO2 nanoparticles prepared by a thermal decomposition process

The generation of TiO₂ nanoparticles by the thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out experimentally using a tubular electric furnace at various synthesis temperatures (700-1300 °C) and TTIP heating temperatures (80-110 °C). The photocatalytic activity of the resulting TiO₂ nanoparticles was examined by measuring the rate of methylene blue decomposition. The TiO₂ nanoparticles were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) measurements and transmission electron microscopy (TEM). The crystallite size and crystallinity increased with increasing synthesis temperature and TTIP heating temperature. A TTIP heating temperature and synthesis temperature of 95 °C and 900 °C, respectively, were found to be the optimal synthesis conditions. The primary particle diameter obtained under optimum synthesis conditions was considerably smaller than the commercial photocatalyst (Degussa, P25). The specific surface areas were more than 134.4 m² g^− 1. Under the optimal conditions, the photocatalytic activity for methylene blue was higher than that of the commercial photocatalyst.     

Synthesis of TiO<Subscript>2</Subscript> Nanoparticles by Microemulsion/Heat Treated Method and Photodegradation of Methylene Blue

In this work, TiO₂ nanoparticles were prepared by microemulsion (ME)/heat treated method and its photodecomposition property of methylene blue. Microemulsion (ME) consisted of water, cyclohexane and an anionic surfactant such as bis (2-ethylhexyl) sodium sulfosuccinate (AOT). Titanium tetraisopropoxide (TTIP) was dropped into the ME solution and then then TiO₂ nanoparticles were formed by the hydrolysis reaction between TTIP in the organic solvent and the water in the core of ME. The smallest diameter of the particles was 20 nm in the system of cyclohexane with surfactant when the molar ratio of water to surfactant was 2. The effect of the process parameters (water/surfactant ratio, different temperatures) on the final characteristics has been investigated, in terms of structural phase and particle size. The TiO₂ nanoparticles were characterized by means of X-ray diffraction, Transmission and scanning electron microscopy, Fourier-Transformed infrared and differential thermal analysis. TiO₂ nanoparticles prepared in this condition were collected as amorphous powder, and converted to anatase phase at less than 350 °C, which is lower than the ordinal phase transition temperature. The crystallite size and crystallinity increase with an increase of heat treated s temperature. The particles are shown to have a spherical shape and have a uniform size distribution. The size of nanoparticles raises with an increase of water/surfactant ratio. In the photocatalytic decomposition of methylene blue, the photocatalytic activity is mainly determined by the crystallinity of TiO₂. In addition, the TiO₂ heat treated at 350 °C shows the highest activity on the photocatalytic decomposition of methylene blue (k = 1.7 × 10⁻² min⁻¹).     

Electrospun Sn-doped TiO2: Synthesis,structural, optical and catalytic performance as a function of Sn loading and calcination temperatures

A series of tin (Sn)-doped titania (TiO₂) composites were prepared by electrospinning and then calcined at temperatures of 500 °C, 600 °C, and 700 °C. The morpho-structural and optical properties of the resulting composites were assesed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. In this way, the effect of the dopant amounts and calcination temperatures on the composition, morphology, band gap energy (E_g) of the prepared composites was established, as well as their photocatalytic activity towards ciprofloxacin (CIP) photodegradation. The kinetics of ciprofloxacin photodecomposition reactions was analyzed. Herein, it is reported that the nanostructured material based on ([1.5%]Sn:TiO₂) sintered at 500 °C shows a remarkable photocatalytic activity with a removal efficiency of about 100% and a rate constant of 9.685 × 10^?2 min^?1. The photocatalytic stability of this material was evaluated by reusability tests with five cycles under identical conditions for CIP photodegradation. In-depth structural investigations were undertaken to explain this remarkable photocatalytic activity towards water decontamination.     

Photocatalytic microreactor study using TiO2-coated porous ceramics

Two kinds of porous ceramic disks, having through-holes with diameters of 0.1 and 0.05 mm, were coated with TiO₂ using two different starting solutions: titanyl(IV)acetylacetonate and a commercial titania sol (STS-01). The morphology of these porous ceramics before and after TiO₂ coating was observed by SEM. The TiO₂-coated porous ceramics were examined as honeycomb photocatalytic microreactors. The photocatalytic activity was evaluated using the decomposition of methylene blue solution for radiation angles of 0° and 10° with respect to the pore axis. The highest photocatalytic activity was obtained for the porous ceramic having the pore diameter of 0.1 mm, coated with titanyl(IV)acetylacetonate and irradiated with a light angle of 0° with respect to the pore axis.     

A photocatalytic performance of TiO<Subscript>2</Subscript> photocatalyst prepared by the hydrothermal method

Anatase phase nanocrystalline TiO₂ powders were prepared by hydrothermal method with the TTIP (titanium tetra isopropoxide) at 200 oC in a stirred autoclave system. The effects of synthesis conditions on the physical properties of catalyst were investigated by using XRD, SEM, DLS, DSC and BET. The TiO₂ powders obtained from the optimum condition showed uniform spherical shape, crystalline structure, submicron size with a sharp size distribution and few agglomerates. The optimum synthesis conditions were obtained within the covered experimental ranges. The photocatalytic activity of TiO₂ powders prepared by the hydrothermal method was tested for photooxidation of methyl orange.     

Effect of calcination temperature on the structural properties and photocatalytic activities of solvothermal synthesized TiO2 hollow nanoparticles

TiO₂ hollow nanoparticles were prepared by the solvothermal method, calcined at different temperatures and characterized by XRD, BET, SEM, PL and FT-IR. The effects of morphology, size and calcination temperature on the photocatalytic activity of the prepared materials were discussed in detail. It was found that the calcination temperature altered the crystallinity, morphology, surface area, and the porous structure. The photocatalytic activity of the TiO₂ powders evaluated through photocatalytic degradation of gaseous acetone under UV-light irradiation, showed TiO₂ calcined at 250 °C to exhibit a higher photocatalytic activity than commercial powders (Degussa P25).     

Photocatalytic evolution of hydrogen over nanocrystalline mesoporous titania prepared by surfactant-assisted templating sol–gel process

Nanocrystalline mesoporous titania was synthesized via a combined sol–gel process with surfactant-assisted templating route and evaluated for photocatalytic activity of hydrogen evolution from an aqueous methanol solution. In this proposed method, applied surfactant template molecules advantageously behaved as both mesopore-forming and gel formation-assisting agent. The activity of the mesoporous titania thermally treated under appropriate conditions, i.e., at calcination temperature of 600 °C for 4 h, was considerably higher than that of commercial titania powders, Ishihara ST-01 and Degussa P-25. It is clearly revealed that introducing mesoporous framework into TiO₂ by this synthetic system provided much better photocatalytic performance.     

Inactivation of pathogenic Klebsiella pneumoniae by CuO/TiO2 nanofibers: A multifunctional nanomaterial via one-step electrospinning

The fabrication and characterization of one-dimensional CuO/TiO₂ nanofibers with high photocatalytic and antibacterial activities are presented. The CuO/TiO₂ nanofibers were prepared by electrospinning of colloid composed of titanium isopropoxide, poly(vinylpyrroliodine) (PVP) and copper nanoparticles and calcination at 700 °C in air for 1 h. The antibacterial activity was tested using Klebsiella pneumoniae as model organism by calculation of the minimum inhibitory concentration (MIC). The obtained CuO/TiO₂ nanofibers showed prominent photocatalytic activity under visible light to degrade reactive black5 and reactive orange16 dyes in aqueous solutions and effectively catalyze K. pneumoniae inactivation. The decomposition process of the cell wall and cell membrane was directly observed by TEM analysis after the exposure of the K. pneumoniae to the nanofibers. Interestingly, the introduced photocatalyst can be reused with the same photocatalytic activity. Overall, the combination of CuO and TiO₂ can be synergistic and resulted in CuO/TiO₂ composite nanofibers having superior photocatalytic and antimicrobial potential to impede K. pneumoniae growth which causes bacterium to die ultimately.     

Preparation, crystal structure, and photocatalytic activity of TiO2 films by chemical vapor deposition

Photocatalytic activities of TiO₂ films were experimentally studied. TiO₂ films with different crystal structures (amorphous, anatase, rutile) were prepared by a Low Pressure Metal Organic Chemical Vapor Deposition (LPMOCVD) at different reaction temperatures and also by a Sol-Gel method using TTIP (Titanium Tetra Iso-Pro-poxyde). The Effect of CVD preparation method, CVD reaction conditions, crystal structure and wave-length of UV light on the photocatalytic decomposition rate of methylene blue in aqueous solution were studied. First, the characteristics of CVD preparation of TiO₂ films, such as the CVD film growth rate, crystal structure and morphology of the grown TiO₂ films, were experimentally studied as a function of CVD reaction temperature. Secondly, photocatalytic activities of TiO₂ films were evaluated by using two types of photo-reactors. The results indicated that TiO₂ films prepared by CVD exhibit higher photocatalytic activity than a catalyst prepared by the Sol-Gel method. Among the CVD grown TiO₂ films, anatase and rutile showed high photocatalytic activities. However, amorphous TiO₂ films showed lower activities. The activity of the photocatalysts of anatase films was excellent under all types of UV-lamps. The activity of CVD-prepared anatase films was four to seven times higher than that of photocatalyst films prepared by the Sol-Gel method.     

TiO2 Nanoparticles with High Photocatalytic Activity Under Visible Light

TiO₂ nanoparticles (C-TNT) with high visible light activity were obtained by carbonization of titania nanotubes (TNT) in an ethanol atmosphere under elevated pressure at 180 and 220 °C. New material was characterised by means of UV–Vis/DR, FTIR/DRS, TEM, and XRD. The photocatalytic activity was tested during monoazo dye decomposition under artificial solar light irradiation. Modified photocatalyst (220 °C, 4 h) had higher photocatalytic activity than both the pristine and commercial P25 catalysts.     

Photoassisted mineralization of remazole red F3B over NiO/TiO2 and CdO/TiO2 nanoparticles under simulated sunlight

In this work, a series of titania-supported NiO and CdO materials were synthesized by a modified sol-gel process. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). The activities of titania-supported NiO and CdO photocatalysts for photocatalytic degradation of Remazole Red F3B (RR) dye, under simulated sunlight, were investigated. The photocatalytic mineralization of an RR dye solution over various NiO-x/TiO₂ and CdO-x/TiO₂ photocatalysts under simulated sunlight was investigated. It was worthy noticing that the photocatalytic activity of titania improved using the prepared catalysts. The prepared TiO₂, NiO-5/TiO₂, and CdO-2/TiO₂ photocatalysts exhibited higher photocatalytic activity under simulated sunlight than did commercial TiO₂. The prepared photocatalysts were stable after photocatalytic degradation of the dye. The observed photocatalytic mineralization of the dye was 51 and 71% over NiO-10/TiO₂ and CdO-2/TiO₂ after 180 min of irradiation, respectively. Juxtaposing a p-NiO-5/TiO₂ semiconductor provided a potential approach for decreasing charge recombination. The prepared photocatalystsNiO-5/TiO₂ and CdO-2/TiO₂ are promising composites for the solar detoxification of textile wastewater.     

Porous titania microspheres with uniform wall thickness and high photoactivity

Highly porous titania particles were prepared by depositing thin films of titania, using alternating reactions of TiCl₄ and hydrogen peroxide, on poly(styrene-divinylbenzene) (PS-DVB) template particles via atomic layer deposition (ALD) at 77 °C. The composition of the titania films was verified by XPS analysis and the titania films were directly observed by TEM. TGA/DSC was used to study the thermal decomposition of the polymer template. Porous titania particles with uniform wall thicknesses were successfully obtained after the template PS-DVB was removed by oxidation in air at 400 °C for 24 h. Verification of the resulting porous structure of the titania particles was done by cross-sectional SEM and nitrogen adsorption–desorption analysis. Porous titania particles were treated at different temperatures. XRD analysis was used to determine the microstructure and phase transformation of titania at elevated temperatures. The photocatalytic activity of these porous titania particles was studied by methylene blue decomposition under UV light at room temperature and was found to be comparable to that of commercial anatase titania nanoparticles (~20 nm). Depositing Na₂SO₄ on TiO₂ retarded the TiO₂ phase transformation from anatase to rutile during calcination and, thus, greatly increased the photoactivity of the porous titania particles.     

TiO2 nanofibers doped with rare earth elements and their photocatalytic activity

In the present study rare earth doped (Ln³⁺–TiO₂, Ln = La, Ce and Nd) TiO₂ nanofibers were prepared by the sol–gel electrospinning method and characterized by XRD, SEM, EDX, TEM, and UV-DRS. The photocatalytic activity of the samples was evaluated by Rhodamine 6G (R6G) dye degradation under UV light irradiation. XRD analysis showed that all the synthesized pure and doped titania nanofibers contain pure anatase phase at 500 °C but at 700 °C it shows both anatase and rutile phase. XRD result also shows that Ln³⁺-doped titania probably inhibits the phase transformation. The diameter of nanofibers for all samples ranges from 200 to 700 nm. It was also observed that the presence of rare-earth oxides in the host TiO₂ could decrease the band gap and accelerate the separation of photogenerated electron–hole pairs, which eventually led to higher photocatalytic activity. To sum up, our study demonstrates that Ln³⁺-doped TiO₂ samples exhibit higher photocatalytic activity than pure TiO₂ whereas Nd³⁺-doped TiO₂ catalyst showed the highest photocatalytic activity among the rare earth doped samples.     

Synthesis,analysis and characterization of ordered mesoporous TiO2/SBA-15 matrix: Effect of calcination temperature

Mesoporous TiO₂/SBA-15 matrix was prepared by the sol–gel synthesis of TiO₂ in previously prepared SBA-15 particles. Nonionic surfactant was used as liquid template and Na₂SiO₄ as SiO₂ precursor for the synthesis of mesoporous silica SBA-15 with high specific surface area. Different calcination temperature was used for the synthesis and analysis of TiO₂/SBA-15 matrix. The synthesized titania/silica composites were characterized by X-ray diffraction, FTIR, TEM, UV–vis spectroscopy, etc. TEM micrographs showed titania is successfully embedded in SBA-15 channel. Different calcination temperature indicates different size of particle formation and different photocatalytic properties. The activity test indicated that TiO₂/SBA-15 composite prepared by this method had better photocatalytic performance than pure TiO₂. The preparation method and the textural characteristics of mesoporous materials have great influence for the photocatalytic activity.     

Sol–gel derived mesoporous titania nanoparticles: Effects of calcination temperature and alcoholic solvent on the photocatalytic behavior

In this study, titania nanoparticles were successfully prepared by a sol–gel process, employing titanium (IV) tetraisopropoxide (Ti[OCH(CH₃)₂]₄; TIP) as a starting precursor. Either ethanol or isopropanol was used as an alcoholic solvent. The as-synthesized mesoporous titania was calcined at different temperatures in the range of 300–700 °C. The aim of this study is to investigate the effects of calcination temperature and the types of solvent on the photocatalytic behavior of titania. The results indicate that crystallinity and crystalline phase are important factors influencing the degree of photocatalytic activity of titania. It was found that the photocatalytic property of titania consisting predominantly of anatase crystallites has been markedly improved in the degradation of methylene blue under UVC light. Compared to ethanol, enhanced photocatalytic activity is obtained with isopropanol solvent through the thermal stability of anatase phase.