[Spectral Characteristics and Catalytic Performances of SO2-4/Ce-TiO2 with Visible Light Response].

Ce doped TiO2 was prepared via sol-gel method. The as-prepared Ce doped TiO2 was impregnated with diluted H2SO4 to obtain a H2SO4-treated Ce doped TiO2. In succession, the characterizations of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), pyridine adsorption-FTIR (Py-FTIR), ultraviolet-visible spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS) were carried out to analyze the reasons for the improvement of the light response performance. The visible light photocatalytic degradation of Rhodamine B (RhB) in an aqueous solution was used as a probe reaction to evaluate the photocatalytic activity of the obtained samples. According to the XRD analysis, Ce doping created the lattice defects in TiO2 and minimized the particle size, which promoted the transfer of photo-generated electrons and then improved catalyst activity. The bridged bidentate coordination mode of SO2-4 was proposed based on the FTIR spectra. The pyridine FTIR spectra showed that both Lewis and Brnsted acid sites were formed on the sample surface. The characteristic absorption band as Lewis acid was more intense than that of the Brnsted acid, exhibiting the major Lewis acidity. The presence of the Lewis acid sites resulted in the transfer of photogenerated electrons to the Lewis acid center because of the electron deficiency of the Lewis acid sites, which contributed greatly to the transport of the photogenerated electrons, inhibiting the recombination of the photogenerated electron/hole pairs and leading to the enhancement of the photocatalytic activity of samples. From UV-Vis results, Ce-doping introduced an impurity energy level in the band gap, narrowing the TiO2 band gap. The impurity energy level could capture the photogenerated electrons on the conduct band and photogenerated holes on the valence band, reducing the recombination probability of photogenerated carriers and exciting the electrons captured on the impurity energy band by the photons with lower energy, thus expanding the light response range of TiO2. The XPS results indicated that the doped Ce existed as a mixture of Ce3+/Ce4+ states, which facilitated the efficient separation of the photo-generated electrons and holes because of the electron transfer, enhancing the system's quantum efficiency. The sulfated Ce doped TiO2 catalysts were very active for the visible photocatalytic degradation of RhB. Results showed that the synergetic effects of Ce doping and acid-treatment improved the visible light response for sulfated Ce-doped TiO2, enhancing the visible photocatalytic activity.

Theoretical Investigation of the Electronic Structure and Optical Properties of CuSin and CuSi-n Clusters (n=4～10).

The electronic structure and UV-Vis properties of ground state CuSin (n=4～10) and CuSin anion clusters were studied using B3LYP density functional theory (DFT) at a 6-311+G (d) level. Calculations indicate that: (1) the band gap of neutral CuSin clusters is narrower than their anion, indicating anion clusters are relatively stable; (2) the energy gap and electronic structure calculations indicate that the anion CuSi5 cluster is more stable than neighboring clusters; and (3) the UV-Vis spectrum of CuSin clusters and CuSin anions suggests that the neutral clusters are weakly absorbing; the anion clusters are strongly absorbing, and anion clusters with increasing size of the Si atoms experience a redshift in the absorption spectra.

[Effects of tetrapod-like zinc oxide whiskers incorporation on antibacterial activity of composite resin].

OBJECTIVE: To evaluate effects of incorporating tetrapod-like zinc oxide whisker (T-ZnOw) antibacterial agent on the antibacterial activity of composite resin, compared with that of the silver-based inorganic antibacterial agent. METHODS: The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the two different antibacterial agents against Streptococcus mutans were investigated using the broth dilution test. Then the antibacterial activities of the self-cured composite resin specimens with different incorporating concentrations of the two antibacterial agents were evaluated using direct contact test. And the antibacterial activities of the resin specimens were examined again after 3 months of accelerating aging. RESULTS: The MIC (MBC) of the T-ZnOw antibacterial agent and silver-based inorganic antibacterial agent were 0.15625 (0.3125) g/L and 0.15625 (0.15625) g/L. When the concentrations of T-ZnOw added to composite resin were 3%, 5%, and 10% (w/w), the antibacterial ratios of the resin specimens were (84.85+/-5.16)%, (94.22+/-3.73)%, and (99.43+/-0.48)% respectively. When the concentrations of the silver-based antibacterial agent added to composite resin were 1%, 3%, and 5%, the antibacterial ratios were (71.01+/-7.67)%, (90.76+/-5.91)%, and (97.19+/-4.10)% respectively. The antibacterial ratios of the resin specimens containing 5% of both antibacterial agents were (89.89+/-5.55)% and (78.79+/-7.81)% respectively after 3 months of accelerating aging. CONCLUSIONS: Incorporation of the T-ZnOw antibacterial agent in composite resin can improve the antibacterial performance of the resin, and the resin exhibits better antibacterial performance than that incorporating silver-based inorganic antibacterial agent after 3 months of aging.

[Effects of three different zinc oxide incorporation on the antibacterial activity against Streptococcus mutans of composite resin].

OBJECTIVE: To investigate the effects of incorporating three different zinc oxide (ZnO) on the antibacterial activity of composite resin. METHODS: The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of nano-ZnO, tetrapod-like zinc oxide whiskers (T-ZnOw), micro-ZnO against Streptococcus mutans were examined by the broth dilution test. Then the three different ZnO were added to the powder of one kind of bicomponent self-cured composite resin at 5% respectively, and the antibacterial activities of the resin specimens were evaluated using the membrane covering method before and after 3-month accelerating aging. RESULTS: The MIC values of the three different ZnO against Streptococcus mutans were 78.13, 312.50 and 1 250.00 microg/mL respectively and the MBC values were 156.25, 625.00, 1,250.00 microg/mL respectively. The antibacterial ratios of the resin specimens incorporating with 5% of the three different ZnO were (93.58+/-5.95)%, (89.42+/-4.11)% and (78.97+/-3.90)% respectively, while after 3-month accelerating aging those were (89.01+/-7.91)%, (84.63+/-4.72)% and (72.27+/-3.89)%. CONCLUSION: The three different ZnO could improve the antibacterial activity of the composite resin. The nano-ZnO exhibit the strongest antibacterial activity, while the micro-ZnO weakest. The T-ZnOw presents comparatively strong antibacterial activity although with smaller specific surface area.

[Effect of Candida albicans growth on silicone elastomer containing nano-TiO2].

OBJECTIVE: To study the antibacterial effect against Candida albicans of the A-2186 silicone elastomer containing nano-TiO2 in vitro. METHODS: Antibacterial agent of nano-TiO2 was added into A-2186 silicone elastomer with incorporating percentages of 0.5%, 1.0%, 1.5%, and 2.0% (W/W). There was no nano-TiO2 in the control group. The antibacterial effect of the A-2186 silicone elastomer was determined using the film contact method with lighting and without lighting. RESULTS: Either with lighting or without lighting, there were significances between the experiment groups and the control group (P < 0.05). When the incorporating percent was 2.0%, the inhibitory effect was the best among the experiment groups. Without lighting, the inhibitory rate was 53.7% and with lighting, the inhibitory rate was 85.9%. CONCLUSIONS: The A-2186 silicone elastomer containing nano-TiO2 has antibacterial properties against Candida albicans, which enhances with increases of nano-TiO2 percent in the material. With the same incorporating percentage, the antibacterial effect with lighting is better than that without lighting.

Silicon hydride clusters Si5Hn (n = 3-12) and their anions: structures, thermochemistry, and electron affinities.

The molecular structures, electron affinities, and dissociation energies of the Si(5)H(n)/Si(5)H(n)(-) (n = 3-12) species have been calculated by means of three density functional theory (DFT) methods. The basis set used in this work is of double-zeta plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. The geometries are fully optimized with each DFT method independently. Three different types of the neutral-anion energy separations presented in this work are the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). The first Si-H dissociation energies for neutral Si(5)H(n) and its anion have also been reported.