Design of Enhanced Catalysts by Coupling of Noble Metals (Au,Ag) with Semiconductor SnO2 for Catalytic Reduction of 4‐Nitrophenol

The reduction of 4‐nitrophenol (Nip) into 4‐aminophenol (Amp) by NaBH₄, which is catalyzed by both binary and ternary yolk–shell noble‐metal/SnO₂ heterostructures, is reported. The binary heterostructures contain individual Au or Ag nanoparticles (NPs) and the ternary heterostructures contain both Au and Ag NPs. The Au@SnO₂ yolk–shell NPs are synthesized via a silica seeds‐mediated hydrothermal method. Subsequently, the Au@SnO₂@Ag and Au@SnO₂@Au yolk–shell–shell (YSS) NPs are synthesized, whereby SnO₂ is located between the Au and Ag NPs. The morphology, composition, and optical properties of the as‐prepared samples are analyzed. For the binary heterostructures, the rate of the reduction reaction increases with decreasing particle size. The catalytic results demonstrate the synergistic effect of Au and Ag in the ternary metal–semiconductor heterostructures, which is beneficial to the catalytic reduction of Nip into Amp. Both the binary and ternary heterostructures exhibit significantly better catalytic performances than the corresponding bare Au and Ag NPs. It is envisaged that the current synthesized strategy will promote further interest in the field of bimetal NP‐based catalysis.     

Analysis of the dynamics of laser induced plume propagation from liquid matrix using fast photography

Glycerol, a liquid matrix material for matrix-assisted laser desorption ionization mass spectrometry, was irradiated by a tunable pulsed infrared laser at wavelengths of 2.80 μ.m, 2.94 μ.m, 3.10 μ.m and 3.50 μ.m, covering the OH and CH stretch vibrations. A fast photography system was introduced to analyze the dynamic process of plume propagation induced by laser ablation up to 1000 μ.s of the delay time. Propagation distance of the plume front was measured and the corresponding velocities were calculated; they varied with the wavelength and decreased with the delay time. At the tunable wavelength of the peak of the OH absorption (3.0 μ.m), theoretical calculations indicate that energy deposition from the pulsed laser is in the regime of stress confinement. The mode of energy deposition depends on the wavelength of the OH vibration and its distance from the absorption maxima. However, stages after a 10 μ.s delay at various wavelengths show a certain similarity in the distance of plume propagation, which can be well fitted by a drag model.     

Effects of surface residual species in SBA-16 on encapsulated chiral (1S,2S)-DPEN-RuCl<Subscript>2</Subscript>(TPP)<Subscript>2</Subscript> in asymmetric hydrogenation of acetophenone

The SBA-16 obtained by different routes of elimination of organic templates were used as the hosts for encapsulation of chiral Ru complex (1S,2S)-DPEN-RuCl₂(TPP)₂ (1) (DPEN = 1,2-diphenylethylene-diamine, TPP = triphenyl phosphine). The methods for removing templates had distinct effects on the amount of residual template in SBA-16, which made the SBA-16 with different surface and structure properties. 1 encapsulated in SBA-16 extracted with the mixture of pyridine and ethanol showed higher activity and enantioselectivity for acetophenone asymmetric hydrogenation.     

Preparation and photocatalytic activity of nonmetal Co-doped titanium dioxide photocatalyst

A series of boron and sulfur co-doped titanium dioxide (TiO₂) photocatalysts were prepared by a sol-gel method using boric acid, thiourea and tetrabutyl titanate [Ti(OC₄H₉)₄] as precursors. The photoabsorbance of as-prepared photocatalysts was measured by UV–Vis diffuse reflectance spectroscopy (DRS), and its microstructure was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and N₂ adsorption-desorption measurements. The prepared photocatalysts consisted of the anatase phase mainly in the form of spherical particles. The photocatalytic performance was studied by photodegradation of methyl blue (MB) in water under UV and visible light irradiation. The calcination temperature and the codoping content influenced the photoactivity. The synergistic effect of boron and sulfur co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of codoped TiO₂ was also confirmed, the photocatalytic activity of TiO₂ remained above 91% of that of the fresh sample after being used four times. It was shown that the co-doped TiO₂ could be activated by visible light and could thus be potentially applied for the treatment of water contaminated by organic pollutants.     

Banach空间上变分不等式的一个超梯度方法

把王宜举等人[Modified extragradient—type method for variational inequali—ties and verification of the existence of solutions,J.Optim.Theory Appl.,2003,119:167-183]在欧氏空间上求解变分不等式的一个超梯度型方法推广到Banach空间.变分不等式中的算子不要求是一致连续的,其主要优点在于不管变分不等式是否有解,算法都是可执行的.此外,变分不等式的可解性可以通过算法产生的序列的性态来刻画.在适当的条件下,算法产生的序列强收敛于变分不等式的一个解,这是Bregman距离意义下离初始点最近的解.本文的主要结果推广和改善了近来文献中的相应结果.