Probing water interactions and vacancy production on gadolinia-doped ceria surfaces using electron stimulated desorption

Polycrystalline gadolinia-doped ceria (GDC) surfaces were studied using low-energy (5-400 eV) electron stimulated desorption (ESD). H(+), O(+), and H(3)O(+) were the primary cationic desorption products with H(+) as the dominant channel. H(+), H(3)O(+), and O(+) have a 22 eV threshold followed by a yield change around 40 eV. H(+) also has an additional yield change approximately 75 eV and O(+) has an additional change approximately 150 eV. The O(+) ESD yield change approximately 150 eV may indicate bond breaking of Gd-O and the involvement of oxygen vacancies. The H(+) and H(3)O(+) threshold data collectively indicate the presence of hydroxyl groups and chemisorbed water molecules on the GDC surfaces. ESD temperature dependence measurements show that the interaction of water with GDC surface defect sites, mainly oxygen vacancies, influences the desorption of H(+), O(+), and H(3)O(+). The temperature dependence of the O(+) ESD at 400 eV incident electron energy yields a 0.21 eV activation energy. This is close to the energy needed for oxygen vacancy production next to a pair of Ce(3+) on a CeO(2) surface. These results may indicate a correlation between the O(+) ESD yield and oxygen vacancy density on GDC surfaces and a potential correlation of O(+) ESD and GDC ionic conductivity.     

Photodynamic therapy based on organic small molecular fluorescent dyes

This review aims to provide a summary of the progress in organic small molecular fluorescent dyes for photodynamic therapy in recent years and it is classified according to the structures of dyes including cyanines, phthalocyanine, BODIPYs and other agents.     

Resonance Rayleigh scattering determination of trace amounts of Al in natural waters and biological samples based on the formation of an Al(III)-morin-surfactant complex

A novel method for the determination of trace amounts of Al(III) based on resonance Rayleigh scattering (RRS) has been developed. In the presence of some surfactants, Al(III) can react with morin and form an Al(III)-morin-surfactant complex, which results in the enhancement of RRS intensity and the appearance of the corresponding RRS spectral characteristics. Their maximum scatter peaks are at 476 nm for the cetyltrimethylammonium bromide (CTAB) system, 489 nm for the cetylpyridinium chloride (CPC) system, 474 nm for the Triton X-100 system, and 473 nm for the Tween-20 system. The enhanced RRS intensity is directly proportional to the concentration of Al(III). The detection limits are in the range of (0.50-1.2)×10⁻⁷ mol l⁻¹ depending on the surfactant. The characteristics of RRS spectra of the complexes, the optimum conditions of these reactions and the influencing factors have been investigated. The method has high selectivity, and was successfully applied to the determination of Al(III) in natural and biological samples. Furthermore, according to different complexation capacity of Al(III)-morin-CTAB system under two pH conditions, speciation analysis of Al(III) in natural waters was explored. The labile monomeric Al fraction (mainly inorganic Al, Al_i) is determined at acidic pH and the total monomeric Al fraction (Al_a) is determined at alkaline pH. The results are in agreement with those obtained by Driscoll’s 8-hydroxyquinoline extraction-ion exchange method.     

Parallel iterative reaction path optimization in ab initio quantum mechanical/molecular mechanical modeling of enzyme reactions

The determination of reaction paths for enzyme systems remains a great challenge for current computational methods. In this paper we present an efficient method for the determination of minimum energy reaction paths with the ab initio quantum mechanical/molecular mechanical approach. Our method is based on an adaptation of the path optimization procedure by Ayala and Schlegel for small molecules in gas phase, the iterative quantum mechanical/molecular mechanical (QM/MM) optimization method developed earlier in our laboratory and the introduction of a new metric defining the distance between different structures in the configuration space. In this method we represent the reaction path by a discrete set of structures. For each structure we partition the atoms into a core set that usually includes the QM subsystem and an environment set that usually includes the MM subsystem. These two sets are optimized iteratively: the core set is optimized to approximate the reaction path while the environment set is optimized to the corresponding energy minimum. In the optimization of the core set of atoms for the reaction path, we introduce a new metric to define the distances between the points on the reaction path, which excludes the soft degrees of freedom from the environment set and includes extra weights on coordinates describing chemical changes. Because the reaction path is represented by discrete structures and the optimization for each can be performed individually with very limited coupling, our method can be executed in a natural and efficient parallelization, with each processor handling one of the structures. We demonstrate the applicability and efficiency of our method by testing it on two systems previously studied by our group, triosephosphate isomerase and 4-oxalocrotonate tautomerase. In both cases the minimum energy paths for both enzymes agree with the previously reported paths.     

三维网状的4-羧基苯氧乙酸锶(Ⅱ)配位聚合物[Sr2(4-CPOA)2(H2O)5]n的合成、结构与热稳定性研究

A novel coordination polymer of [Sr₂(4-CPOA)₂(H₂O)₅]_n (where 4-CPOA^2- is 4-carboxylphenoxyacetate) has been synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. The title complex belongs to monoclinic system with space group C2/c, a=2.563 9(5) nm, b=1.162 7(2) nm, c=0.742 96(15) nm, β=99.64(3)°. V=2.183 5(7) nm³, Z=4, M_r=653.60, D_c=1.988 g·cm^-3, R=0.027 8, wR=0.058 1. The strontium atom has a bicapped triangular prismatic coordination geometry, involving four oxoacetate oxygen atoms, one ether oxygen atom from different 4-CPOA^2- ligands and three water molecules. The strontium(Ⅱ) ions are linked by 4-CPOA^2- ligands and water molecules to form a 3D network structure. CCDC: 223313.     

A New Method to Investigate the Clustering Phenomena in Supercritical Fluids

EstimationoflocaldensityofsolventaboutthesoluteSolvatochromicbehaviorsofspectroscopicprobesarewidelyusedtoestimatethesol-ventstrengthofsupercriticalfluids(SCF,).i-3lnthiswork,thesolvatochrondcshiftofthen-n*transitionbandforacetone(O.o37mo1.L-')insupercrihcal(SC)CO2wasde-terminedbyUVspectroscopytostUdythesolvationeffect.TheMcRae-BaylissexpressionbasedonthedielectriccontinUUInmodelgivestherelahonshipbetWeenso1vatochromicshiftandpo1arizabilityofnonPolarsolvents4-5asfollows:wherevisthewave…     

A MATHEMATICAL STUDY OF THE SEVEN GRAPTOLITE BIOZONES OF THE LOWER SILURIAN LONGMAXIAN STAGE IN CHINA

With the aid of matrix theory and computer a series of data can be obtained such as the total number of localities in which r species of graptolites appears, the common number of localities in which both i and j species of graptolites appear, the total number of species of graptolites in one locality, the common number of species of graptolites found in both i and j localities, the total number of zones in which r species of graptolites appears, the common number of zones in which both i and j species appear, the total number of species of graptolites found in one zone, the common number of species of graptolites found in both i and j zones. Based on these data a common problem in biostratigraphy may be solved, that is, in the absence of the zonal graptolite which species of graptolites can be chosen to replace the zonal graptolite, or how to detect the zonal graptolite of a graptolite biozone. The result of matrix treatment not only detects the graptolite biozone but is useful to infer the paleo-biogeo     

Synthesis, Crystal Structure and Properties of [Co(1,3- bdoaH)_2·4H_2O]·4H_2O with Benzene-1,3-dioxyacetate Ligand

1INTRODUCTIONTheorganicaromaticcarboxylatemetalcom-plexeshavearousedmuchattentionandbeenwidelyinvestigated.However,thestrategyofdesignandsynthesisofthesecomplexesismostlyfocusedonrigidligands,suchasterephthalicacidandbenzenetricarboxylicacid,etc.[1～5].Theassemblyofcom-plexesbyusingflexiblearomaticcarboxylateli-gandsisfarlessdeveloped[6,.Phenylenedioxydia-7]ceticacids(bdoaH2)withbiologicalactivitiesandwideapplicationsinagriculture[8]areafamilyofmultidentateflexibleligandswithversatilebind…     

Selective oxidation of isobutane over Mo-V-Te mixed oxide catalysts with different tellurium contents

A series of MoV_0.3Te_x (x = 0−0.3) mixed oxides were prepared and investigated for the selective oxidation of isobutane. Among them, MoV_0.3Te_0.23 showed the best methacrolein and methacrylic acid selectivity (as high as 17% and 16%, respectively), and the yield to methacrolein and methacrylic acid reached 3.6% and 3.5%, respectively, at 21.3% isobutane conversion at 440°C.     

Synthesis and Crystal Structure of a 1-D Chain Zinc（Ⅱ） Coordinated Polymer with N-p-Tolysulfonyl-glutamine

A novel coordination polymer {[Zn(ts-gln)(bipy)]3H2O}n (ts-glnH2=N-p-toly-sulfonyl-glutamine,bipy=2,2-bipyridine) has been prepared and structurally characterized by X-ray diffraction method. It crystallizes in orthorhombic,space group P212121 with a=8.2622(5),b=16.6244(10),c=18.2807(10) ,V=2510.9(3) 3,C22H28N4O8SZn,Mr=573.91,Z=4,Dc= 1.518 g/cm3,μ(MoKa)=1.115 mm-1,F(000)=1192,the final R=0.0262 and wR=0.0662 for 5691 independent reflections with Rint=0.0240. The zinc(Ⅱ) atom is coordinated by N(3) and N(4) atoms of a bipy molecule,two carboxylate O(1) and O(2A) and amino N(1) atoms of ts-gln ligands,resulting in a square-pyramidal geometry. The title complex consists of an infinite zigzag chain of zinc(Ⅱ) ions linked by the carboxylate of N-p-tolysulfonyl-glutamine.