Efficient photocatalytic degradation of organics present in gas and liquid phases using Pt-TiO2/Zeolite (H-ZSM).

TiO2-encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO2 and zeolites. Pt was immobilized on the surface of the TiO2-encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5-10 wt% TiO2-encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO2-H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2-propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO2-H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO2-H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants.

Enhancement of adhesion strength and cellular stiffness of osteoblasts on mirror-polished titanium surface by UV-photofunctionalization.

Ultraviolet (UV)-photofunctionalization of titanium substantially enhances the strength and quality of osseointegration by promoting osteogenic cellular attachment and proliferation. However, the mechanism underlying the initial interaction between the cells and the surface of the material remains to be elucidated, especially where the influence of surface roughness is excluded as a factor. The effect of UV-photofunctionalization on the adhesive strength and cellular stiffness of a single osteoblast and its association with the extent of cell spread, cytoskeletal development and focal adhesion assembly on a very smooth titanium surface was evaluated. Rat bone marrow-derived osteoblasts were cultured on UV-treated or untreated mirror-polished titanium disks. The mean critical shear force required to initiate detachment of a single osteoblast (n=10) was >2000nN on a UV-treated surface at 3h incubation, which was 17 times greater than that on an untreated surface. The mean total energy required to complete the detachment of osteoblasts (n=10) was consistently >60pJ on a UV-treated titanium surface after 24h culture, which was up to 42 times greater than that on an untreated surface. Cellular shear modulus, which represents cellular stiffness, was consistently greater on a UV-treated surface than on an untreated surface after 24h incubation (n=10). This strengthening of cell adhesion and cellular mechanical properties on UV-treated titanium was accompanied by enhanced cell spread and actin fiber development and increased levels of vinculin expression. These results indicate that UV-photofunctionalization substantially strengthens osteoblast retention on titanium bulk material with no topographical features, and that this is associated with enhancement of intracellular structural development during the cell adhesion process.

Application of ion beam techniques for preparation of metal ion-implanted TiO2 thin film photocatalyst available under visible light irradiation: metal ion-implantation and ionized cluster beam method.

Transparent TiO2 thin film photocatalysts have been prepared on silica glass plate by an Ionized Cluster Beam (ICB) method. In order to improve the electronic properties of these photocatalysts, transition metal ions (V+, Cr+, Mn+, Fe+) were implanted into the TiO2 thin films at high energy acceleration using an advanced metal ion-implantation technique. The combination of these ion beam techniques can allow us to prepare the TiO2 thin film photocatalysts which can work effectively under visible light (lambda>450 nm) and/or solar light irradiation. The investigation using XAFS and ab initio molecular calculation suggests that the substitution of octahedrally coordinated Ti ions in TiO2 lattice with implanted metal ions is important to modify TiO2 to be able to adsorb visible light and operate under visible light irradiation.

Characterization of Ti-Beta zeolites and their reactivity for the photocatalytic reduction of CO2 with H2O.

A characterization of Ti-Beta zeolites synthesized under various conditions as well as an investigation of their photocatalytic properties for the reduction of CO2 with H2O at 323 K to produce CH4 and CH3OH were carried out. In situ XAFS spectra measurements indicated that a highly dispersed tetrahedral titanium oxide species was present in the zeolite framework and an increase in the coordination number of the titanium oxide species by the addition of H2O and CO2 molecules could be detected. The Ti-Beta zeolite having a hydrophilic property (Ti-Beta(OH)) exhibited a more dramatic increase in the coordination number than the Ti-Beta(F) zeolite which had a hydrophobic property. These results suggest that CO2 and H2O molecules can be adsorbed efficiently onto the highly dispersed tetrahedrally coordinated titanium oxide species. UV irradiation of these Ti-Beta zeolite catalysts in the presence of H2O and CO2 led to the formation of CH4 and CH3OH. Ti-Beta(OH) exhibited a higher reactivity than Ti-Beta(F), while the selectivity for the formation of CH3OH on Ti-Beta(F) was higher than that for Ti-Beta(OH). These results indicated that the reactivity and selectivity of the zeolite catalyst can be determined by the hydrophilic and hydrophobic properties of the zeolites.

Local structure of Pb(II) ion catalysts anchored within zeolite cavities and their photocatalytic reactivity for the elimination of N2O.

The Pb2+/ZSM-5 catalyst was prepared by an ion-exchange method and its photocatalytic activity for the decomposition of N2O under UV irradiation was investigated. In-situ UV-Vis absorption spectroscopy and XAFS (XANES and FT-EXAFS) investigations revealed that the Pb2+ ions exist in a highly dispersed state within the pores of the zeolites. UV irradiation of the catalysts in the presence of N2O led to the photocatalytic decomposition of N2O into N2 at temperatures as low as 298K. The effective wavelength of the irradiated UV light indicated that the excited state of the Pb2+ ions included within the zeolite cavities plays a significant role in the photocatalytic decomposition of N2O molecules.

Investigations on the local structure of Ag+/ZSM-5 catalysts and their photocatalytic reactivities for the decomposition of N2O at 298 K.

Ag+/ZSM-5 catalysts were prepared by an ion-exchange method and UV-irradiation of the catalysts in the presence of N2O led to the photocatalytic decomposition of N2O into N2 and O2 at 298 K. Investigations on the effective wavelength of irradiated UV-light for the reaction as well as the in-situ characterization of the catalysts by means of XAFS, UV-Vis, photoluminescence and FT-IR spectroscopies revealed that the photoexcitation of the Ag+-N2O complexes formed between gaseous N2O and the isolated Ag+ ions play a significant role in this reaction.

XAFS studies on the local structures of Ti-HMS mesoporous molecular sieves and their photocatalytic properties.

Various Ti-containing HMS mesoporous molecular sieves having high surface areas and pore volumes have been prepared at ambient temperature. The Ti-HMS samples exhibited a well-defined XRD pattern of typical hexagonal lattice. UV-vis and XAFS spectral for the calcined forms of Ti-HMS indicated that the Ti ions are tetrahedrally coordinated in the framework of HMS for the samples of Ti-HMS(1) and Ti-HMS(2), while at least a fraction of Ti-oxides in Ti-HMS(10) is in octahedral coordination. UV irradiation of the Ti-HMS catalysts in the presence of NO was found to lead to the decomposition of NO to form N2, O2, and N2O at 273 K with different yields and product distributions. The photocatalytic performance of Ti-oxides appears to be completely modified by their incorporation structure and reaction environment. High efficiency and selectivity for the formation of N2 and O2 in the photocatalytic decomposition of NO was achieved with the Ti-HMS(1) having highly dispersed isolated tetrahedral titanium oxide species, while the reactivity decreased with an increase in the Ti content.

Characterization and photocatalytic reduction of CO2 with H2O on Ti/FSM-16 synthesized by various preparation methods.

Ti/FSM-16 photocatalysts were prepared by various methods and their reactivity for the photocatalytic reduction of CO2 with H2O at 323 K was investigated. UV irradiation of Ti/FSM-16 in the presence of CO2 and H2O led to the formation of CH4 and CH3OH. The photocatalytic reactivity and selectivity differed remarkably by variations in the preparation method. Analyses of the UV-Vis absorption and XAFS spectra showed that the dispersion and local structure of the Ti-oxide species greatly depended on the preparation method. The formation of CH3OH was found to be related to the local structure of the Ti-oxide species while the yield of the photoluminescence was attributed to the charge transfer excited state of the highly dispersed tetrahedrally coordinated Ti-oxide species. Methanol formation was found to be more efficient on Ti/FSM-16 having such highly dispersed tetrahedrally coordinated Ti-oxide species.

Preparation of Ti-Si binary oxide thin film photocatalysts by the application of an ionized cluster beam method.

Ti-Si binary oxide thin films with various Ti contents were prepared in a dry process by using an Ionized Cluster Beam (ICB) deposition method with multi ion sources. From the results of UV-VIS measurements, the transmittance of these binary oxide thin films is very high compared to pure TiO2 thin films, indicating that the Ti-oxide exists in a highly dispersed state in the SiO2 matrices. The EXAFS spectra of these thin films with lower Ti content exhibited only a sharp preedge peak attributed to the highly dispersed Ti-oxide species which differs from the peaks of anatase TiO2 thin films. UV light irradiation of these Ti-Si binary oxide thin films in the presence of NO were found to lead to the evolution of N2 and O2 with a good linearity against the irradiation time. The lower the Ti content, the higher the reactivity and the selectivity for the formation of N2 were. These results clearly indicate that the highly dispersed Ti-oxide species plays an important role in the formation of N2 and O2 for the photocatalytic decomposition of NO under UV light irradiation.

Photoinduced superhydrophilic properties of Ti-B binary oxide thin films and their photocatalytic reactivity for the decomposition of NO.

Characterizations of Ti-B binary oxide thin films by means of various spectroscopic measurements have shown that Ti-B binary oxide thin films are formed by ultra fine TiO2 nanoparticles. A dramatic decrease in the contact angle of water droplets to 0 degree under ultraviolet (UV) light irradiation and a return to only half of its initial value under dark conditions were observed for the Ti-B binary oxide thin films. Moreover, ultraviolet irradiation of these thin film photocatalysts in the presence of NO led to photocatalytic decomposition of NO into N2 and O2. Especially when the Ti content was low, the size of the primary nanoparticles of the thin films was smaller and the photocatalytic reaction proceeded efficiently with a high selectivity for the formation of N2 and O2 from NO.