R.M. Mohamed

Enhancement of titania by doping rare earth for photodegradation of organic dye (Direct Blue)

Lanthanide ions (La(3+), Nd(3+), Sm(3+), Eu(3+), Gd(3+), and Yb(3+))/doped TiO2 nanoparticles were successfully synthesized by sol-gel method. Their photocatalytic activities were evaluated using Direct Blue dye (DB53) as a decomposition objective. The structural features of TiO2 and lanthanide ions/TiO2 were investigated by XRD, SEM, UV-diffuse reflectance, and nitrogen adsorption measurements. Our findings indicated that XRD data characteristic anatase phase reflections and also XRD analysis showed that lanthanides phase was not observed on Lanthanide ions/TiO2. The results indicated that Gd(3+)/TiO2 has the lowest bandgap and particle size and also the highest surface area and pore volume (V(p)) as well. Lanthanide ions can enhance the photocatalytic activity of TiO2 to some extent as compared with pure TiO2 and it was found that Gd(3+)/TiO2 is the most effective photocatalyst. The photocatalytic tests indicate that at the optimum conditions; illumination time 40 min, pH approximately 4, 0.3g/L photocatalyst loading and 100 ppm DB53; the dye removal efficiency was 100%. Details of the synthesis procedure and results of the characterization studies of the produced lanthanide ions/TiO2 are presented in this paper.

H2 Production with Low CO Selectivity from Photocatalytic Reforming of Glucose on Ni/TiO2-SiO2

Nano-sized Ni particles on TiO2-SiO2 were synthesized by the two methods of photo-assisted deposition (PAD) and impregnation. H2, which is a promising energy carrier, with a low CO concentration was produced by the photocatalytic reforming of glucose (a model biomass) on the Ni/TiO2-SiO2 catalyst. The supported Ni enhanced the rate of H2 production while it suppressed CO selectivity. The catalysts were characterized by X-ray diffraction, X-ray absorption fine structure, transmission electron microscope, and nitrogen adsorption analysis. Both H2 production and CO selectivity were strongly dependent on the preparation method, and PAD-Ni/TiO2-SiO2 was the better catalyst for H2 production with the lowest CO concentration.

Synthesis and characterization of P-doped TiO 2 thin-films for photocatalytic degradation of butyl benzyl phthalate under visible-light irradiation

P-doped TiO2 (PTIO) thin-films with different P contents were prepared using a sol-gel method. The thin-film samples were characterized using various techniques. The photocatalytic activity was evaluated by decomposing butyl benzyl phthalate under visible-light irradiation. The results showed that the transformation of anatase to the rutile phase was inhibited and grain growth of TiO2 was prevented by P doping. The results confirm that the doped P atoms existed in two chemical forms, and those incorporated in the TiO2 lattice may play a positive role in photocatalysis. The high photocatalytic activities of the PTIO thin-films may be the result of extrinsic absorption through the creation of oxygen vacancies, rather than excitation of the intrinsic absorption band of bulk TiO2. The PTIO can be recycled with little depression of the photocatalytic activity. After six cycles, the photocatalytic activity of the PTIO film was still higher than 98%.

Photocatalytic Degradation of Methylene Blue by Fe/ZnO/SiO2 Nanoparticles under Visiblelight

The photocatalytic activity of Fe/ZnO/SiO2 catalysts under visible-light irradiation for the degradation of methylene blue was evaluated. The effect of pH, illumination time, amount of catalyst loaded, and initial dye concentration on the degradation efficiency of methylene blue was investigated. The results reveal that the optimum photocatalytic oxidation conditions of methylene blue are as follows: pH=4 and illumination time is 30 min, the amount of catalyst loading is 0.075 g/L and 50 ppm methylene blue dye concentration. Under these conditions, the removal efficiency of methylene blue was 100%.

Characterization and Catalytic Properties of Nano-Sized Au Metal Catalyst on Titanium Containing High Mesoporous Silica (Ti-HMS) Synthesized by Photo-Assisted Deposition and Impregnation Methods

The photo-assisted deposition (PAD) and impregnation (img) synthesis of nano-sized Au metal on Ti-HMS are reported. The prepared catalysts were characterized by different techniques such as XRD, XAFS, TEM and nitrogen adsorption analysis. Photocatalytic reactivity using Au/Ti-HMS catalysts under visible-light condition on the oxidation of CO with O2 reaction was evaluated. The results have shown notable photocatalytic activity of PAD-Au/Ti-HMS which was 2.1 and 5.7 times higher than that of img-Au/Ti-HMS and Ti-HMS, respectively.

Photocatalytic Oxidation of Carbon Monoxide over NiO/SnO Nanocomposites under UV Irradiation

The NiO/SnO2 nanocomposites have been prepared by the simple coprecipitation method and further characterized by the XRD, SEM, TEM, UV-Vis, and BET. X-ray diffraction (XRD) data analyses indicate the exclusive formation of nanosized particles with rutile-type phase (tetragonal SnO2) for Ni contents below 10 mol%. Only above 10 mol% Ni, the formation of a second NiO-related phase has been determined. The particle size is in the range from 12 to 6 nm. It decreases with increasing amounts of doping NiO. The morphology of NiO-doped SnO2 nanocrystalline powders is spherical, and the distribution of particle size is uniform, as seen from transmission electron microscopy (TEM). The photocatalytic oxidation of CO over NiO/SnO2 photocatalyst has been investigated under UV irradiation. Effects of NiO loading on SnO2, photocatalyst loading, and reaction time on photocatalytic oxidation of CO have been systematically studied. Compared with pure SnO2, the 33.3 mol% NiO/SnO2 composite exhibited approximately twentyfold enhancement of photocatalytic oxidation of CO. Our results provide a method for pollutants removal. Due to simple preparation, high photocatalytic oxidation of CO, and low cost, the NiO/SnO2 photocatalyst will find wide application in the coming future of photocatalytic oxidation of CO.

Zeolite Y from rice husk ash encapsulated with Ag-TiO2: characterization and applications for photocatalytic degradation catalysts

AbstractA high level of efficiency in the photocatalytic reactions was achieved by increasing the surface area of the photocatalyst by supporting fine TiO2 particles on porous materials. Among various supports, zeolites seem to be an attractive candidate. Ti-incorporated Y zeolite was prepared by an ion-exchange method, while Ag was immobilized on the encapsulated titanium via impregnation method. The produced samples were characterized using X-ray diffraction, ultraviolet and visible spectroscopy, photoluminescence emission spectra, scanning electron microscopy, and surface area measurement. Furthermore, the catalytic performances of Ti-Ag/NaY tests were carried out for degradation of cyanide using visible light. The results reveal a good distribution of Ag on the zeolite. Ag doping can eliminate the recombination of electron-hole pairs in the catalyst. These results demonstrate that the optimum weight% of Ag to Ti-NaY is 0.3%; this weight% facilitates high performance by the photocatalyst, degrading 99%...

Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

Anisotropy in the mechanical properties of organic crystals: temperature dependence

The nanoindentation technique has recently been utilized for quantitative evaluation of the mechanical properties of molecular materials successfully, including their temperature (T) dependence. In this paper, we examine how the mechanical anisotropy varies with T in saccharin and L-alanine single crystals. Our results show that elastic modulus (E) decreases linearly in all the cases examined, with the T-dependence of E being anisotropic. Correspondence between directional dependence of the slopes of the E vs. T plots and the linear thermal expansion coefficients was found. The T-dependence of hardness (H), on the other hand, was found to be nonlinear and significant when (100) of saccharin and (001) of L-alanine are indented. While the anisotropies in E and H of saccharin and E of L-alanine enhance with T, the anisotropy in H of L-alanine was found to reduce with T. Possible mechanistic origins of these variations are discussed.

Enhancement of photocatalytic properties of Ga2O3-SiO2 nanoparticles by Pt deposition

Ga2O3-SiO2 nanoparticles were prepared by a sol-gel method and Pt was then immobilized on their surface via photo-assisted deposition (PAD). The produced samples were characterized using X-ray diffraction (XRD), ultraviolet and visible spectroscopy, photoluminescence emission spectroscopy, and surface area measurements. The catalytic performances of the Ga2O3-SiO2 and Pt/ Ga2O3-SiO2 samples were evaluated for the degradation of cyanide using visible light. XRD and EDX results showed that the Pt was well dispersed within the Ga2O3-SiO2 phase and was detected on the surface of the catalyst, which confirmed the successful loading of Pt ions by the PAD method. BET results revealed that the surface area of Ga2O3-SiO2 was higher than that of Pt/Ga2O3-SiO2. 0.3 wt% Pt/Ga2O3-SiO2 exhibited the highest photocatalytic activity for degradation of cyanide under visible light. The catalyst could be reused with no loss in activity for the first 10 cycles.