Papers by Keyword: Photocatalytic Reaction

Abstract: Anatase-type TiO₂ films synthesised on quartz glass demonstrated cell adhesion control when illuminated from the backside with a 150 W Xe lamp emitting white light. The UV component was fully absorbed by the TiO₂ film, preventing cell exposure to it. By selectively applying localised light, non-contact control of cell adhesion areas was achieved. If non-toxic films responsive to conventional LED panels could be used, this would enable precise and easy control of cell adhesion areas. The purpose of this study was to synthesise inorganic semiconductor films with a narrower bandgap than TiO₂, responding to visible light from LED, and to investigate their photo-responsive properties. α-Fe₂O₃ films were deposited on borosilicate glass or ITO-coated quartz glass using RF sputtering with the corresponding metallic targets under an Ar or Ar/O₂ mixed atmosphere. XRD analysis showed sharp diffraction peaks, confirming the successful synthesis of the films. The absorption edges of the oxides shifted to longer wavelengths compared to that of TiO₂, corresponding to their bandgap differences. When a tablet device (HUAWEI MediaPad M3 Lite 10wp) displaying a white image was used as a light source, the oxide films showed a noticeable photocurrent. In the photocurrent profile during the on/off cycle of the light, a phenomenon of current flowing in the reverse direction when the light was turned off was observed. Moreover, this current reversal was more pronounced when the grains were fine. This suggests that the grain boundaries acted like a capacitor and induced polarisation behaviour.

Abstract: Several techniques have been employed to attach/detach cells to/from a substrate. Cells cultured on a substrate are generally detached from the substrate into a sheet by the destruction of protein between the cells and the substrate using enzymes such as trypsin. However, the enzymes also damage the adhesion molecules among the cells. TiO₂ is an n-type semiconductor with an energy band gap of 3.0-3.2 eV, which displays a photocatalytic activity under ultraviolet (UV) light. The purpose of this work was to fabricate photo-responsive cell culture vessel using TiO₂ film and to investigate adhesion behaviour of cells on it. TiO₂ films were prepared on SiO₂ plates by a sol-gel method using titanium tetraisopropoxide. Primary osteoblasts were seeded on the vessels and then incubated at 37 °C. During the incubation, UV irradiation was performed continuously from back-side of the vessels. Basically the number of cells monotonically increased with incubation periods under darkness. Previous light irradiation promoted the cell adhesion on the surface. The formation of Ti-OH groups on the TiO₂ seems to be facilitated by the UV irradiation. In contrast, the cells decreased under continuous light irradiation. The cells were not exposed to UV in the vessels since it was completely absorbed by the TiO₂ layer. It might be due to generated photocurrent or hydroxyl radicals on the TiO₂ surface. These results imply that the adhesion/proliferation/detachment behaviours of cells can be controlled by the photocatalytic reaction of TiO₂ and the irradiation patterns.

Abstract: Microfluidic technology has been increasingly applied in field of photo catalytic reactor because of the large surface to volume ratio, shorter diffusion distance of the reactant solution, higher mixing efficiency and lower cost. This article reviews the detail progress in fabrication of micro-reactor for degradation of dye in waste water. Importantly, dye degradation required uniform UV light exposure which could be resolved by carrying out degradation in a micro-reactor. This paper discussed several of potential and commercial photocatalytic micro-reactor fabrication and configurations, in particular, the polydimethyl siloxane (PDMS) photocatalytic reactors.

Abstract: This study utilized chemical method to reform titania nanopowder into larger surface area titania-based nanotubes (NTs). Various factors, such as reaction temperature, concentration, time, and aging time were investigated to determine their effects toward NT properties. The formation of the titania-based NTs was carried out under the conditions of 10N NaOH reaction medium, at reaction temperature and time of 116°C and 23 hours, respectively. Subsequent aging was done at 40°C for 24 hours. The NTs were further resintered at 400°C for 1 hour to improve their crystallinity and photocatalytic efficiency. Result indicates that aging process is significant for NT synthesis process. The treated titania-based NT has a surface area of 247.91 m²/g with nearly 100% photodecomposition of (MB) in 15 minutes.

Abstract: The Ag₃PO₄ crystal with 200-600 nm in diameter was successfully synthesized using co-precipitation method with AgNO₃ and Na₂HPO₄^.12H₂O as starting materials. The product was characterized using XRD, DRS, FTIR and SEM. The photocatalytic activities were evaluated under blue light irradiation assisted by Fe²⁺. The 1 mL of Fe²⁺ aqueous solutions consisted of 1.00, 0.10, 0.01, 0.001 and 0.0001 mM Fe²⁺ was added into a 100 mL solution of Rhodamine B, and the photocatalytic oxidation of Rhodamine B was carried out under visible light irradiation. The highest photocatalytic activity was observed when 1 ml of 0.001 mM of Fe²⁺ aqueous solution was added in the Rhodamine B solution. The result inferred the possibility of in-situ peroxide generation during the photocatalysis reaction.

Abstract: The objective of this study is to explore a method to improve hydrophilicity of the surface of formers that could be more easily dipped to produce high quality dipped rubber products. Photocatalytic TiO₂ composite films were prepared by sol-gel method. Glass formers were coated with nitrogen doped TiO₂ nanocomposite film by dipping method and annealed at 600°C for 1 h. Phase formation of TiO₂ was characterized by XRD. Morphology of the TiO₂ films was observed by using atomic force microscopy (AFM). Optical absorption of the films and degradation concentration of methylene blue had been measured employing UV-Vis spectrophotometer. The hydrophilicity of the thin films was determined in terms of the contact angles of water and NR rubber latex droplets on the coated TiO₂ composite films under visible light irradiation. It was found from the experimental study that the TiO₂ nano-composite film can improve wet-ability of the coated former surfaces.

Abstract: The objective of this study is to explore a method to improve hydrophilicity of the surface of formers that could be more easily dipped to produce high quality dipped rubber products. Photocatalytic TiO₂ composite films were prepared by sol-gel method. Glass formers were coated with the Ni/B/N/TiO₂ nanocomposite film by dipping method and annealed at 400°C for 1 h. Phase formation of TiO₂ was characterized by XRD. Morphology of the TiO₂ films was observed by using atomic force microscopy (AFM). Optical absorption of the films and degradation concentration of methylene blue had been measured employing UV-Vis spectrophotometer. The hydrophilicity of the thin films was determined in terms of the contact angles of water and NR rubber latex droplets on the coated TiO₂ composite films under visible light irradiation. It was found from the experimentally study that the Ni/B/N/TiO₂ nanocomposite film can improve wet-ability of the coated former surfaces.

Abstract: Nanocrystalline TiO₂ films were deposited on polymethylmethacrylate (PMMA) substrates by dip–coating process from colloidal anatase aqueous solutions. Microwave–hydrothermal process treating TiO₂ colloidal solutions was applied to enhance crystallization under a mild condition and avoid post–treatment. The as–prepared TiO₂ films were characterized and analysed by X–ray diffraction (XRD), UV–visible spectroscopy and atomic force microscopy (AFM). The photocatalytic degradation of Rhodamine B (RhB) under ultraviolet radiation was explored. Results show that pure anatase TiO₂ is achieved rapidly using microwave hydrothermal process. The TiO₂ suspension becomes uniformly disperse, stable and deposit-free after ultrasonic dispersion. The thin films deposited on unmodified PMMA substrates from the dispersive TiO₂ colloidal solution are dense, homogeneous, crack–free, without visible agglomerates and show high photocatalytic activity without post-treatment. Rhodamine B has been degraded over 99 % after 180 minutes under UV irradiation.

Abstract: Thin films with the high content of Ti coated on the stainless steel (SS) sieves were successfully prepared through the sol gel method. Photocatalytic reaction on the TiO₂-coated SS sieves with UVA (ultraviolet light with the range of 315-400 nm) radiation is effective to destroy three selected bacterial strains with log-phase period. As a result, bactericidal ability was achieved to 77% in aqueous media. Amount of bacterial numbers, 3.4×10⁷ CFU/ml can be removed in this study, compared with our previous study, 1.85×10³ CFU/ml in the air media. Good contribution of bactericidal ability in 385 nm UVA radiation or heavy metals including Fe, Mn, Cr, Ni and Ti from the SS sieve was obtained as the range of 30-76%. The percentage of 10-17% contribution of bactericidal ability was increased with the photocatalytic reaction additive. It concluded the performance of bactericidal ability in aqueous solution is ascribed to the combination of UVA radiation, heavy metals on the sieve and photocatalytic reaction. The SS sieve coated with TiO₂ particles can be applied as a disinfectant for the effluent of wastewater treatment plant or water supply system in the future.

Abstract: The effect of Ni doping in Ni and B co-doped TiO2 composite films on photocatalytic reaction and hydrophilic property were investigated. The TiO2 composite films were prepared by sol-gel and coated on glass substrates by dipping methods. These composite thin films were calcined at the temperatures of 400°C for 1 h. Phase formation of TiO2 was characterized by XRD. Morphology of TiO2 composite films were observed by using atomic force microscopy (AFM). The chemical composition and purity of the prepared films were analyzed by EDS, FTIR and FT-Raman spectrometers. The photoactivity of synthesized films was performed by means of degradation of methylene blue dye solution under UV and visible light irradiation. The hydrophilic property was measured in terms of a contact angle of water droplet on the films with and without the activation of UV irradiation. It was found that Ni doping seems to affect on TiO2 phase, crystallinity of the anatase phase, crystallite size of the composite films and band gap energy of the catalysts, resulting in their photocatalytic reaction and hydrophilic property. The crystallinity of anatase increased with an increase in Ni content varied from 0-3 mol% but decreased with an increase in Ni content above 3 mol%. It was found that 3 mol% Ni/B/TiO2 film, having highest crystallinity and smallest crystallite size shows the highest of photocatalytic reaction while 2 mol% Ni/B/TiO2 film provides the most hydrophilic effect. Only anatase phase was found at the calcination temperature of 400°C. The smooth film surfaces exhibits a high hydrophilic property. Super-hydrophilicity (contact angle equal to zero) of all B and Ni co-doped TiO2 films was found at UV irradiation for 25 minutes.