Semiconductor photocatalysts have recently attracted much interest because of their possible applicability to detoxification of environmental pollutants [1] and solar-energy conversion. [2] Among the photocatalysts, TiO 2 is believed to be the most promising presently known material because of its superior photoreactivity, nontoxicity, long-term stability, and low price. The photocatalytic activity of TiO 2 depends on various parameters, including crystallinity, impurities, surface area, and density of surface hydroxy groups; however, the most significant factor is its crystal form. [3] TiO 2 is usually used as a photocatalyst in two crystal structures: rutile and anatase. Anatase generally has much higher activity than rutile. [4] More interesting is the fact that the activity of P-25 (Degussa), which consists of anatase and rutile (4/1 w/w), exceeds that of pure anatase in several reaction systems. [3b, 5] Indeed, P-25 has frequently been used as a benchmark for photocatalysts.However, the origin of the high photocatalytic activity of P-25 remains unclear. Here we report on the fundamental mechanism and present a highly active photocatalyst film designed on the basis thereof. Thin films of photocatalysts not only serve as models of particulate systems but also aid in the development of their applications. [1b] Addition of 1-phenyl-1,3-butanedione (BzCH 2 Ac) to a solution of Ti(OC 4 H 9 ) 4 in methanol led to a red shift of the absorption peak for the p ± p* transition of BzCH 2 Ac from 310 to 360 nm, owing to chelation of Ti 4 . After hydrolysis, the resultant sol was used to form a gel film in which the chelate bonds were kept intact. Significant lower solubility of the gel film in alcohol was induced by photoexcitation of the p ± p* absorption band. [6] Patterned (pat-) TiO 2 films were prepared by utilizing this phenomenon. The dimensions of the patterning are expressed by the width w of the stripes of the TiO 2 film and their spacing s. Figure 1 shows a 3D surface-structure photograph of a sample formed on quartz by using a photomask with slits of 0.2 mm in width. Regularly spaced, Figure 1. Three-dimensional surface-structure photograph of pat-TiO 2 (A)/ quartz (w s 0.2 mm). 0.2 mm wide stripes of TiO 2 film with a thickness of about 65 nm are present on the substrate with a spacing of 0.2 mm (TiO 2 /quartz; w s 0.2 mm).X-ray diffraction (XRD) patterns are shown in Figure 2 A for a sputter-deposited TiO 2 (sp-TiO 2 ) film (a) and a sol ± gel TiO 2 (sg-TiO 2 ) film overlaid on the sp-TiO 2 film (b). In pattern (a), the diffraction peaks from the (110) and (211) Figure 2. A) X-ray diffraction patterns of the sp-TiO 2 film (a) and the sg-TiO 2 /sp-TiO 2 film (b). B) Plots of (ahn) 1/2 vs photon energy for the sg-TiO 2 (a) and sp-TiO 2 (b) films. planes of rutile are observed at 2 q 27.4 and 54.38, respectively. The peak intensity ratio I(211)/I(110) is much smaller than that of randomly oriented rutile powder (ca. 0.6) [7] and suggests that the sp-TiO 2 film has a preferred orientation towards the [001]...

Semiconductor photocatalysts have recently attracted much interest because of their possible applicability to detoxification of environmental pollutants [1] and solar-energy conversion. [2] Among the photocatalysts, TiO 2 is believed to be the most promising presently known material because of its superior photoreactivity, nontoxicity, long-term stability, and low price. The photocatalytic activity of TiO 2 depends on various parameters, including crystallinity, impurities, surface area, and density of surface hydroxy groups; however, the most significant factor is its crystal form. [3] TiO 2 is usually used as a photocatalyst in two crystal structures: rutile and anatase. Anatase generally has much higher activity than rutile. [4] More interesting is the fact that the activity of P-25 (Degussa), which consists of anatase and rutile (4/1 w/w), exceeds that of pure anatase in several reaction systems. [3b, 5] Indeed, P-25 has frequently been used as a benchmark for photocatalysts.However, the origin of the high photocatalytic activity of P-25 remains unclear. Here we report on the fundamental mechanism and present a highly active photocatalyst film designed on the basis thereof. Thin films of photocatalysts not only serve as models of particulate systems but also aid in the development of their applications. [1b] Addition of 1-phenyl-1,3-butanedione (BzCH 2 Ac) to a solution of Ti(OC 4 H 9 ) 4 in methanol led to a red shift of the absorption peak for the p ± p* transition of BzCH 2 Ac from 310 to 360 nm, owing to chelation of Ti 4 . After hydrolysis, the resultant sol was used to form a gel film in which the chelate bonds were kept intact. Significant lower solubility of the gel film in alcohol was induced by photoexcitation of the p ± p* absorption band. [6] Patterned (pat-) TiO 2 films were prepared by utilizing this phenomenon. The dimensions of the patterning are expressed by the width w of the stripes of the TiO 2 film and their spacing s. Figure 1 shows a 3D surface-structure photograph of a sample formed on quartz by using a photomask with slits of 0.2 mm in width. Regularly spaced, Figure 1. Three-dimensional surface-structure photograph of pat-TiO 2 (A)/ quartz (w s 0.2 mm). 0.2 mm wide stripes of TiO 2 film with a thickness of about 65 nm are present on the substrate with a spacing of 0.2 mm (TiO 2 /quartz; w s 0.2 mm).X-ray diffraction (XRD) patterns are shown in Figure 2 A for a sputter-deposited TiO 2 (sp-TiO 2 ) film (a) and a sol ± gel TiO 2 (sg-TiO 2 ) film overlaid on the sp-TiO 2 film (b). In pattern (a), the diffraction peaks from the (110) and (211) Figure 2. A) X-ray diffraction patterns of the sp-TiO 2 film (a) and the sgTiO 2 /sp-TiO 2 film (b). B) Plots of (ahn) 1/2 vs photon energy for the sg-TiO 2 (a) and sp-TiO 2 (b) films. planes of rutile are observed at 2 q 27.4 and 54.38, respectively. The peak intensity ratio I(211)/I(110) is much smaller than that of randomly oriented rutile powder (ca. 0.6) [7] and suggests that the sp-TiO 2 film has a preferred orientation towards the [001] ...

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Autoimmune mechanism may be involved in some patients with idiopathic pancreatitis associated with hypergammaglobulinemia.

Catheter US probe EUS findings for cardial vascular structures before treatment are useful for predicting the likelihood of recurrence of esophageal varices.

Novel nanoparticles with unique physicochemical characteristics are being developed with increasing frequency, leading to higher probability of nanoparticle release and environmental accumulation. Therefore, it is important to assess the potential environmental and biological adverse effects of nanoparticles. In this study, we investigated the toxicity and behavior of surface-functionalized nanoparticles toward yeast (Saccharomyces cerevisiae). The colony count method and confocal microscopy were used to examine the cytotoxicity of manufactured polystyrene latex (PSL) nanoparticles with various functional groups (amine, carboxyl, sulfate, and nonmodified). S. cerevisiae were exposed to PSL nanoparticles (40 mg/L) dispersed in 5-154 mM NaCl solutions for 1 h. Negatively charged nanoparticles had little or no toxic effect. Interestingly, nanoparticles with positively charged amine groups (p-Amine) were not toxic in 154 mM NaCl, but highly toxic in 5 mM NaCl. Confocal microscopy indicated that in 154 mM NaCl, the p-Amine nanoparticles were internalized by endocytosis, whereas in 5 mM NaCl they covered the dead cell surfaces. This demonstrates that nanoparticle-induced cell death might to be related to their adhesion to cells rather than their internalization. Together, these findings identify important factors in determining nanoparticle toxicity that might affect their impact on the environment and human health.