This work reports the preparation of porous and visible-light absorbing Bi2WO6/TiO2 heterojunction films as a photoelectrode and their photoelectrochemical and photocatalytic performances. The Bi2WO6 underlayers with high surface roughness were prepared by a superhydrophilicity-assisted method. The Bi2WO6/TiO2 bilayer films showed high interface area between the Bi2WO6 and TiO2 layers. Significant enhancement in visible light photocurrent generation on the optimal Bi2WO6/TiO2 film was observed as compared with unmodified Bi2WO6 (a factor of 2) and unmodified TiO2 (a factor of 13) films. The optimal visible-light photocatalytic activity of the Bi2WO6/TiO2 film was 15.1 nm of stearic acid degraded, which was 6 and 4.6 times higher than that of unmodified Bi2WO6 and TiO2 films, respectively. The enhanced photoelectrochemical and photocatalytic performances of Bi2WO6/TiO2 films were attributed to the improved charge separation efficiency derived from the suitable valence band interaction between the two semiconductors, as well as high interface area and porous structure of the heterojunction bilayer films. Charge separation between Bi2WO6 (underlayer) and TiO2 (overlayer) was verified by photoluminescence (PL) and current−voltage (I−V) characteristics studies.

A novel and environmental friendly method was developed to prepare transparent, uniform, crack-free and visible light activated nitrogen doped (N-doped) titania thin films without the use of organic Ti precursors and organic solvents. The N-doped titania films were prepared from heating aqueous peroxotitanate thin films deposited uniformly on superhydrophilic uncoated glass substrates. The pure glass substrates were superhydrophilic after being heated at 500 degrees C for 1 h. Nitrogen concentrations in the titania films were adjusted by changing the amount of ammonia solution. The optimal photocatalytic activity of the N-doped titania films was about 14 times higher than that of a commercial self-cleaning glass under the same visible light illumination. The current reported preparative technique is generally applicable for the preparation of other thin films.

No abstract

No abstract

No abstract

C-N-codoped TiO 2 (CNTO) photocatalysts were successfully synthesized by using "green" method peroxo sol-gel. XRD results revealed the presence of anatase phase only for all samples. The result of Scanning Electron Microscope-Electron Dispersive X-Ray (SEM-EDX) showed surface morphology of CNTO10 was spherical (44 nm) and homogeneous. Diffuse Reflectance Spectra UV-Vis (DRS UV-Vis) result showed red shift in absorbance indicating successful modification of TiO 2 by C and N. The result of photocatalytic activity in reducing Cr(VI) showed that the Cr(VI) reduction increase with the increase of irradiation time and photocatalyst's mass. The highest Cr(VI) reduction was 90.07% for CNTO10 sample. This is due to the synergistic effects of C and N dopants that improves TiO 2 photocatalytic activity under visible light irradiation.

Hydroxyapatite (HAp) has been used for various applications such as orthopedics, drug delivery material, and bone tissue engineering. It is well known that HAp has a good biocompatibility and osteoconductivity, so HAp can be used in biomedical applications. Hydroxyapatite can be combined with other materials, in particular polymer, to expand its range of applications. In this study, the polymer that will be used as a support for the HAp composite is alginate (Alg). The HAp/Alg composite has been synthesized by the precipitation method. The XRD results show that the crystal system of HAp was hexagonal. The spheric-like shaped particles can be observed from SEM images, and particle size distribution spread from 400 to 1100 nm. The EDS spectrum exhibited the peak of Ca, C, P, and O elements, indicating that alginate had interacted with hydroxyapatite in the synthesized composite. The as-fabricated composite showed not only good crystallinity but also high thermal resistance. Thermogravimetric-differential thermal analysis (TGA-DTA) revealed that the HAp/Alg composites have a constant weight at 750 °C, so it might be applied in advanced applications such as bioimaging, drug carrier, and other cancer treatments.

AbstrakZat warna direct red-23 merupakan pewarna sintetik dengan struktur senyawa organik yang bersifat nonbiodegradable. Zat warna direct red-23 mengandung senyawa azo dan bersifat karsinogenik. Zat warna direct red-23 didegradasi secara fotolisis menggunakan sinar UV (ultraviolet), sinar matahari, tanpa dan dengan penambahan katalis C-N-codoped TiO2. Larutan zat warna direct red-23setelah dan sebelum didegradasi diukur dengan spektrofotometer UV-Vis pada panjang gelombang 400-800 nm. Penentuan berat optimum katalis C-Ncodoped TiO2 dilakukan dengan metode fotolisis sinar UV dan didapatkan berat optimum 15 mg. Persen degradasi zat warna direct red-23 secara fotolisis sinar UV dan sinar matahari tanpa katalis C-N-codoped TiO2 27.47% dan 13.74%. Persen degradasi meningkat menjadi 68.68% dan 28.57% dengan penambahan 15 mg katalis C-N-codoped selama 120 menit fotolisis. Dari penelitian dapat disimpulkan metode fotolisis dengan sinar UV lebih efisien dibandingkan dengan sinar matahari.Kata kunci: Direct red-23, sinar UV, sinar matahari, C-N-codoped TiO2. AbstractDirect red-23 dye is a synthetic dye that is widely used in textile industry. Wastes generated from textile industrial processes are generally non-biodegradable organic compounds containing azo compounds and carcinogenic. Direct red-23 dye was degraded by photolysis UV Light method, solar irradiation, without and addition of C-N-codoped TiO2 catalyst. The results degradation of direct red-23 were measured with a UV-Vis spectrophotometer at wavelength of 400-800 nm. Determination of optimum weight of the C-N-codoped TiO2 catalyst was performed by photolysisUV Light method and the optimum C-N-codoped TiO2 catalyst is obtained 15 mg. Percent degradation of direct red-23 dye by photolysis of UV light and solar irradiation without C-Ncodoped TiO2 to 27.47% and 13.74%. Percent degradation increased to 68.68% and 28.57% by adding C-Ncodoped TiO2 catalyst was adding 120 menutes of photolysis. From the research it can be concluded by photolysis with UV Light methodis more efficient compared to solar radiation.