Search

Abstract: Novel hierarchical rose bridal bouquet- and humming-top-like nanostructured TiO2 were successfully prepared by the simple process with the hydrothermal temperature as the morphology-controlling factor. The gradual transformation from layered titanate to brookite phase was well consistent with the formation mechanism of the hierarchical morphologies. The three-dimensional flower bouquets built from the bunches of roses with surrounding fern fronds displayed the best adsorptivity and completely degraded methylene blue within 60min under UV irradiation, whereas the humming-top geometry composed of anisotropically elongated spindle-like crystallites was detrimental to the dye photodegradation. [Copyright &y& Elsevier]

Abstract: Optical, structural and photocatalytic properties of TiO2 thin films obliquely deposited on quartz glass substrate using an electron-beam evaporation method were investigated. The photocatalytic activity of the films was evaluated by photodecomposition of methylene blue. An increase in incident deposition angle increased the porosity and surface roughness of the TiO2 films. As a result, the photocatalytic activity was enhanced with incident deposition angle up to 60°. However, a further increase in incident deposition angle to 75° reduced the photocatalytic activity due to a lack of the crystalline phase. [ABSTRACT FROM AUTHOR]

Abstract: TiO2/SiO x /TiO x multi-layers on quartz glass were prepared by electron-beam evaporation method and their structural and photocatalytic properties were investigated. The photocatalytic activity of the TiO2/SiO x /TiO x multi-layer was evaluated by the photodecomposition of methylene blue in aqueous solution. As the thickness of the SiO x inter-layer increased, the surface roughness of the TiO2/SiO x /TiO x multi-layer increased but the anatase crystallite size decreased. The TiO2/SiO x (80nm)/TiO x multi-layer exhibited excellent photocatalytic activity resulting from higher surface roughness and more trap levels in the SiO x (80nm) inter-layer. [ABSTRACT FROM AUTHOR]

Abstract: Acrylic, acetic and methacrylic acids which are short-chain carboxylic acids have been applied to modify the surface of oleic acid-coated TiO2 nanorods (NRs) and oleic acid/oleylamine-coated Fe3O4 nanoparticles (NPs). The short-chain carboxylic acids not only acted as modifying ligands but also as anti-solvents during the ligand exchange processes. The prepared products have been characterized using TEM, HRTEM and FTIR spectroscopy. The results show that the acrylic acid-exchanged TiO2 and Fe3O4 solution remain stable even after six months, showing no agglomeration. Such acrylic acid-exchanged nanocrystals (NCs) prepared in this work could also be well-dispersed in other polar solvents such as ethanol and ethanol/water mixtures. On the contrary acetic acid and methacrylic acid-exchanged TiO2 solutions were not stable due to the presence of remaining oleic acid on the TiO2 surface. This approach has been shown to be effective in making hydrophilic TiO2 NRs and Fe3O4 NPs and can also be applied to other NCs covered by different hydrophobic ligands. [Copyright &y& Elsevier]

M/TiO2 (M=metal; Ag, Cu) thin films on quartz glass were prepared by RF magnetron co-sputtering process and the calcination effects on their optical and structural properties were investigated. The as-deposited M/TiO2 films are amorphous, and they are the anatase phase at 300–700 °C. The Ag-doped films have the anatase phase at 900 °C, whereas the Cu-doped films contain the rutile phase at 900 °C, implying that metal doping affects the temperature of phase transformation from anatase to rutile. The crystallite size of the anatase phase and the agglomerates of primary particles of the metal-doped TiO2 thin films increase with increasing calcination temperature. The X-ray photoelectron spectroscopy (XPS) results show that doped-silver is present in the metal state, while doped-copper exists in the mixed metal/oxide state. The as-deposited thin films have high transparency in the visible range. The transmittance of Cu/TiO2 thin films calcined at 900 °C is considerably reduced due to the crystal phase transformation, the variation of film composition and the optical scattering effect resulting from increased crystallite size. The absorption edge of transmittance is red-shifted at 900 °C due to the change of the optical band gap energy. [Copyright &y& Elsevier]

TiO2 thin films were prepared on quartz glass by sol-gel process and their structural and optical properties were examined at various catalyst concentrations and calcination temperatures. The as-deposited TiO2 thin films are amorphous, and they transform into the anatase phase at 400–600 °C, and into the anatase–rutile phase at 800 °C, and further into the rutile phase at 1000 °C. The temperature of phase transformation is decreased with the concentration of catalyst HCl. The crystallite size of TiO2 thin films is increased with increasing calcination temperature and catalyst concentration. The secondary particles in the TiO2 thin films grow by intra-agglomerate densification below 800 °C, whereas they grow by inter-agglomerate densification above 800 °C. The deposited TiO2 thin films have high transparency in the visible range. The transmittance of the films calcined at 800 and 1000 °C are significantly reduced in the wavelength range of 300–800 nm due to the change of crystallite phase and increased particle size. The refractive index of TiO2 thin films is increased with increasing calcination temperature and catalyst concentration. On the other hand, the porosity of TiO2 thin film is decreased. [Copyright &y& Elsevier]

Abstract: Cerium and lanthanum-incorporated mesoporous TiO2 with up to 10mol% metal were synthesized by a sol–gel method using a neutral structure-directing agent. The textural properties and surface structure of samples were investigated by means of N2 sorption measurements, SEM images and XRD patterns. The doping of lanthanide elements resulted in not only an increase in the surface area, pore volume and average pore size of mesoporous TiO2, but also in inhibition of mesostructure collapse and the growth of TiO2 nanocrystallites. In both cerium and lanthanum-incorporated mesoporous TiO2, the fact that only the anatase TiO2 phase was present indicated substantial incorporation of metal species into the framework or significant dispersion inside the channel. However, Ce and La-incorporated mesoporous TiO2 differed with regard to the surface chemical states of the metal elements. According to XPS of xCe-TiO2 powders, Ti mainly existed in a coordinatively unsaturated titanium (IV) state for low doping amounts, whereas the Ti3+ state was observed when the Ce/Ti ratio exceeded one. In contrast, no apparent difference in peak intensity and position was seen for lanthanum samples. While only the La3+ state was found in xLa–TiO2, Ce 3d spectra showed a mixture of Ce3+/4+ oxidation states on the surface which led to changes in the chemical environment of oxygen. [Copyright &y& Elsevier]

TiO 2 hollow nanospheres assembled with single-crystalline anatase polyhedra have been prepared by a facile hydrothermal method. The supersaturation is found to significantly affect the crystallization habit of TiO 2 . Larger polyhedral single crystals are obtained at lower supersaturation, while higher supersaturation results in the formation of hollow nanospheres assembled with anatase polyhedra. The photocatalytic performance of produced TiO 2 crystals with various morphologies is tested for the photodecomposition of methylene blue. TiO 2 hollow nanospheres with higher surface area exhibit enhanced photocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: Morphological, structural and photocatalytic properties of graphene oxide (GO)/TiO2 thin-film deposited on quartz substrate were investigated. The TiO2 film was prepared by electron-beam evaporation and the GO film by spin coating method. The photocatalytic activities of the GO/TiO2 film were evaluated by photodecomposition of methylene blue. There was synergistic effect between TiO2 and GO which causes a rapid photo-induced charge separation and the reduction of the recombination of electron–hole pairs under the UV–visible light irradiation. GO on TiO2 film also promotes the properties of adsorption of the dye, photon scattering probability, and interacting surface area. As a result, it leads to the enhancement of the efficiency of the photodegradation in GO/TiO2 film. [Copyright &y& Elsevier]

Abstract: Reduced graphene oxide–TiO2 hybrids were successfully prepared by the hydrothermal approach using triethanolamine and acetylacetone as the chelating agents. Without any additive, large aggregated TiO2 clusters were randomly distributed dominantly at the edge and less on the basil plane of coagulated reduced graphene oxide (RGO) layers. The presence of chelating ligands remarkably facilitated the selective growth and regular spread of TiO2 nanocrystals onto individually exfoliated RGO sheet. Such sandwich-like structure with stronger coupling and chemical interaction resulted in the surface area increase, the rearrangement of energy level, the enhanced concentration of oxygen vacancies, leading to much higher adsorbability and photocatalytic degradation of Rhodamine B under both UV and visible irradiations. These RGO–TiO2 hybrid systems are potentially beneficial for widely practical applications in air/water purification, electronic devices, batteries, solar cells or supercapacitors. [Copyright &y& Elsevier]

Abstract: Titanium dioxide/graphene oxide composites were prepared using a simple colloidal blending method. Superior adsorption and photocatalysis performance under both UV and visible radiation were achieved in the presence of the composites rather than in pure TiO2. Gradually increasing the content of graphene oxide up to 10wt% promoted the removal efficiency and correspondingly, facilitated the photodegradation rate of methylene blue. The good photocatalytic performance on the TiO2–graphene oxide composite systems irrespective of light sources could be attributed to a synergy effects including the increase in specific surface area with graphene oxide amount as well as the formation of both π–π conjugations between dye molecules and aromatic rings and the ionic interactions between methylene blue and oxygen-containing functional groups at the edges or on the surfaces of carbon-based nanosheets. Graphene oxide worked as the adsorbent, electron acceptor and photosensitizer to efficiently enhance the dye photodecomposition. [Copyright &y& Elsevier]

Abstract: A series of vanadium-doped mesoporous titania with different metal contents was synthesized in the study via a sol–gel process with the assistance of a dodecylamine surfactant. The existence of vanadium ions not only suppressed crystallization and sintering but also enhanced the porosity of the mesoporous TiO2. Varying the vanadium concentration led to significant changes in the chemical oxidation state of each component. The presence of metal dopants significantly improved the removal efficiency of benzene and the doping the titania with 5mol% vanadium removed the most benzene, regardless of the adsorption temperature. The adsorption behavior was elucidated by the specific surface area, the interactions between surface hydroxyl groups and the π-electrons of benzene, and the formation of σ-bonding and d-π* back-donation between the adsorbent and organic compounds. [Copyright &y& Elsevier]

Abstract: Polyaniline–titanium dioxide (PANI–TiO2) hybrid materials were synthesized in supercritical CO2 using two different methods. In the first method, separately synthesized TiO2 particles were mixed with aniline to perform polymerization in supercritical CO2. The second method included the preparation of aniline–TiO2 hybrids through a sol–gel reaction of titanium isopropoxide in the presence of aniline. Further polymerization of aniline–TiO2 hybrids in supercritical CO2 produced PANI–TiO2 hybrid particles. The final products showed the intrusion of PANI into the internal structure of TiO2. The PANI–TiO2 hybrid materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), electrical conductivity (EC), Fourier-transform infrared (FT-IR) and X-ray diffraction (XRD) measurements. PANI–TiO2 nano-composites synthesized with the first method showed a relatively low electrical conductivity of 3.78×10−2 S/cm at 20°C. TGA suggested that the particles contained 40.6% TiO2 by mass and showed a strong interaction at the interface of TiO2 and PANI. The electrical conductivity of the hybrid particles produced using the second method increased to 7.75×10−2 S/cm and the TGA results showed 34.4% TiO2 by mass. Through SEM and TEM analyses it was confirmed that the PANI has been interpenetrated into the three-dimensional network of the TiO2 when the second method was used. [Copyright &y& Elsevier]

Abstract: Transparent nanocrystalline TiO2 thin films were deposited on soda lime glass (SLG) at a low temperature by a simple sol–gel dip-coating method. TiO2 sols were prepared from titanium alkoxide in acidic aqueous solutions and were subsequently refluxed at 80 °C for 8 h, leading to the formation of anatase crystallites. The as-deposited TiO2 films were heated at 115 °C for 15 min. The resulting films consisted of uniform spherical particles of about 20 nm in size and had excellent photoactivity for the degradation of ethanol. [Copyright &y& Elsevier]

TiO2 thin films were prepared by sol–gel dip coating and their structural and optical properties were examined at various calcination temperatures. The X-ray diffraction (XRD) results showed that TiO2 thin film calcined at 300 °C was amorphous, and transformed into the anatase phase at 400 °C, and further into rutile phase at 1000 °C. The phase transformation temperature has been dependent upon the concentration of catalyst HCl. The crystallite size of TiO2 thin films was increased with increasing calcination temperature. The micro-particles in the films grew by intra-agglomerate densification below 1000 °C, whereas they grew by inter-agglomerate densification above 1000 °C. The transmittance of the films calcined at 1000 and 1100 °C was reduced significantly in the wavelength range of about 300–700 nm due to the change of crystallite phase and composition in the films. The refractive index of TiO2 thin films was increased with increasing calcination temperature, and the film thickness and the porosity of TiO2 thin films were decreased. [Copyright &y& Elsevier]