Showing papers by "Xiamen University published in 2004"

Magnetite-Containing Spherical Silica Nanoparticles for Biocatalysis and Bioseparations

Abstract: The simultaneous entrapment of biological macromolecules and nanostructured silica-coated magnetite in sol−gel materials using a reverse-micelle technique leads to a bioactive, mechanically stable, nanometer-sized, and magnetically separable particles. These spherical particles have a typical diameter of 53 ± 4 nm, a large surface area of 330 m2/g, an average pore diameter of 1.5 nm, a total pore volume of 1.427 cm3/g and a saturated magnetization (MS) of 3.2 emu/g. Peroxidase entrapped in these particles shows Michaelis−Mentan kinetics and high activity. The catalytic reaction will take place immediately after adding these particles to the reaction solution. These enzyme entrapping particles catalysts can be easily separated from the reaction mixture by simply using an external magnetic field. Experiments have proved that these catalysts have a long-term stability toward temperature and pH change, as compared to free enzyme molecules. To further prove the application of this novel magnetic biomaterial in...

Adsorption and reaction at electrochemical interfaces as probed by surface-enhanced Raman spectroscopy.

Abstract: Over the past three decades, surface-enhanced Raman spectroscopy (SERS) has gone through a tortuous pathway to develop into a powerful surface diagnostic technique for in situ investigation of surface adsorption and reactions on electrodes. This review presents the recent progress achieved mainly in our laboratory on the improvement of detection sensitivities as well as spectral, temporal, and spatial resolutions. Various surface roughening procedures for electrodes of different metals coupled with maximum use of a high-sensitivity confocal Raman microscope enable us to obtain good-quality SER spectra on the electrode surfaces made from net Pt, Ni, Co, Fe, Pd, Rh, Ru, and their alloys that were traditionally considered to be non-SERS active. A novel technique called potential-averaged SERS (PASERS) has been developed for the quantitative study of electrochemical sorption. Applications are exemplified on extensively studied areas such as coadsorption, electrocatalysis, corrosion, and fuel cells, and several advantages of in situ electrochemical SERS are demonstrated. Finally, further developments in this field are briefly discussed with emphasis on the emerging methodology.

Capturing the labile fullerene[50] as C50Cl10

Abstract: 地址: 1. Xiamen Univ, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 2. Xiamen Univ, Dept Chem, Xiamen 361005, Peoples R China 3. Chinese Acad Sci, Inst Chem, Beijing 100080, Peoples R China 4. Chinese Acad Sci, Wuhan Inst Phys & Math, State Key Lab Magnet Resonance & Mol Phys, Wuhan 430071, Peoples R China 电子邮件地址: syxie@jingxian.xmu.edu.cn

A Simple and Effective Route for the Synthesis of Crystalline Silver Nanorods and Nanowires

Abstract: A simple and effective approach to the aqueous-phase synthesis of crystalline silver nanorods and nanowires is demonstrated, using which their diameters and aspect ratios can be effectively controlled. The synthesis involves a template-less and non-seed process to high-quality nanoparticles, which is low-cost and proceeds at moderate temperatures. The nanorods and nanowires were synthesized by the reduction of silver nitrate with tri-sodium citrate in the presence of sodium dodecylsulfonate. The concentration of tri-sodium citrate plays a critical role while sodium dodecylsulfonate, as a capping agent, only plays an assistant role in controlling the diameters and aspect ratios of the products. High-resolution transmission electron microscopy (HRTEM) and selected-area electron diffraction (SAED) investigations show that the silver nanocrystals are generated with a twinned crystalline structure. We also put forward a primary experimental model to shed light on their growth mechanisms.

Origin of deterioration for LiNiO2 cathode material during storage in air

Abstract: Lithium nickel oxide, a potential candidate for cathode material for lithium-ion batteries, showed a distinct deterioration after storage in air for a time. The origin of this deterioration was explored by investigating surface structure, surface species, and ionic oxidation state of fresh and stored LiNiO 2 materials. Rietveld analysis of X-ray diffraction patterns showed not only the formation of Li 2 CO 3 on the surface, but also a weakening of ordered layered structure for the stored materials. X-ray photoelectron spectroscopy revealed that Ni 3 + transforms to Ni 2 + and active oxygen species exist on the surface of stored materials. Temperature programmed desorption-mass spectroscopy measurements gave evidence that active oxygen species (O-, O - 2) occur on the surface of LiNiO 2 after storage. A surface reaction mechanism based on the transformation of Ni 3 + /Ni 2 + and the evolution of active oxygen species is proposed.

Studies on glass transition temperature of chitosan with four techniques

Abstract: Studies on the glass transition temperature (Tg) of chitosan are difficult to pursue because of the difficulty in sample preparation and the hydroscopicity of samples. There are a few works concerning this principal relaxation of chitosan. Among them, several quite different values (150°C, 161°C, and 203°C) have been reported. In this paper, the Tg of chitosan (140 ∼ 150°C) was determined by means of four techniques, namely, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), thermally simulated current spectroscopy (TSC), and dilatometry (DIL). DSC measurement has been assumed not to be sensitive enough to detect the relaxation temperature of polysaccharides. We propose a new method to improve the sensitivity of the DSC measurement. After a physical aging treatment of samples, the transition in DSC traces became much more distinct because of the enthalpy relaxation. This technique was also used to distinguish the Tg from other relaxations. The Tg of chitosan with different degree of deacetylation (D.D.) was examined by DSC. No influence of D.D. on Tg was found. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1553–1558, 2004

Synthesis and Characterization of a Tetrazolate-Bridged Coordination Framework Encapsulating D2h-Symmetric Cyclic (H2O)4 Cluster Arrays

Abstract: Reaction of 5,5‘-(1,4-phenylene)bis(1H-tetrazole), which was prepared in two steps, with cadmium nitrate in DMF produced a three-dimensional framework with one-dimensional channels (35% void volume), in which unprecedented hydrogen-bond-supported D2h tetrameric cyclic water clusters ranked

A well-resolved uudd cyclic water tetramer in the crystal host of [Cu(adipate)(4,4-bipyridine)].(H2O)2.

Abstract: A well-resolved uudd cyclic water tetramer was reported in the crystal host of [Cu(adipate)(4,4-bipyridine)]·(H2O)2, showing the contribution of the water cluster to the stability of the crystal host and the role of cooperative association of the water cluster and the crystal host in the formation of the water cluster.

Axin stimulates p53 functions by activation of HIPK2 kinase through multimeric complex formation.

Abstract: Axin and p53 are tumor suppressors, controlling cell growth, apoptosis, and development. We show that Axin interacts with homeodomain-interacting protein kinase-2 (HIPK2), which is linked to UV-induced p53-dependent apoptosis by interacting with, and phosphorylating Ser 46 of, p53. In addition to association with p53 via HIPK2, Axin contains a separate domain that directly interacts with p53 at their physiological concentrations. Axin stimulates p53-dependent reporter transcription in 293 cells, but not in 293T, H1299, or SaOS-2 cells that are defective in p53 signaling. Axin, but not AxinΔHIPK2, activates HIPK2-mediated p53 phosphorylation at Ser 46, facilitating p53-dependent transcriptional activity and apoptosis. Specific knockdown of Axin by siRNA reduced UV-induced Ser-46 phosphorylation and apoptosis. Kinase-dead HIPK2 reduced Axin-induced p53-dependent transcriptional activity, indicating that Axin stimulates p53 function through HIPK2 kinase activity. Interestingly, HIPK2ΔAxin that lacks its Axin-binding region acts as a dominant-positive form in p53 activation, suggesting that the Axin-binding region of HIPK2 is a putative autoinhibitory domain. These results show that Axin acts as a tumor suppressor by facilitating p53 function through integration of multiple factors.

Synthesis of a symmetrical tetrasubstituted cucurbit[6]uril and its host-guest inclusion complex with 2,2 ′-bipyridine

Abstract: Synthesis of a symmetrical tetrasubstituted cucurbit[6]uril has been achieved by using the diether of dimethylglycoluril (1) and the dimmer of glycoluril (2). The structure of the symmetrical tetramethylcucurbit[6]uril (TMeQ[6]) has been determined by single crystal X-ray diffraction, 1H NMR spectroscopy and ESMS. The 1H NMR spectra of 2,2′-bipyridine added to TMeQ[6] reveal that the host-guest inclusion complex was easily formed.

Hydrothermal Syntheses, Crystal Structures and Photoluminescent Properties of Three Metal‐Cluster Based Coordination Polymers Containing Mixed Organic Ligands

Abstract: Three novel metal-cluster based coordination polymers (MCCPs) with formulae [Zn4(μ3-OH)2(H2O)2(sip)2(4,4′-bpy)2]·3H2O (MCCP-4), [Cd4(μ3-OH)2(H2O)2(sip)2(4,4′-bpy)4]·H2O (MCCP-5) and [Cd6(μ3-OH)4(μ2-OH2)2(OH2)2 (nip)4(4,4′-bpy)3]·3H2O (MCCP-6) [H2sip = 5-sulfoisophthalic acid, H2nip = 5-nitroisophthalic acid and 4,4′-bpy = 4,4′-bipyridyl] were hydrothermally synthesized and characterized by single-crystal X-ray diffraction studies. MCCP-4 crystallizes in the triclinic space group P with a = 10.106(2), b = 10.851(2), c = 11.125(2) A, α = 105.66(3), β = 112.63(3), γ = 98.18(3)°, V = 1041.8(4) A3, and Z = 2. MCCP-5 crystallizes in the monoclinic space group C2/c with a = 25.602(1), b = 16.571(1), c = 13.322(1) A, β = 92.524(1)°, V = 5646.4(2) A3, and Z = 4. MCCP-4 and -5 consist of similar [M4(μ3-OH)2]6+ tetranuclear building units that are joined through sip and 4,4′-bpy ligands to generate a two-dimensional structure (MCCP-4) and a three-dimensional structure (MCCP-5), respectively. MCCP-6 crystallizes in the triclinic space group P with a = 14.295(2), b = 14.472(2), c = 20.204(3) A, α = 73.362(3), β = 82.200(3), γ = 62.769(2)°, V = 3560.9(10) A3, and Z = 2. MCCP-6 contains unprecedented [Cd6(μ3-OH)4(μ2-OH2)2]8+ hexanuclear building units which are linked through nip and 4,4′-bpy ligands to afford a two-dimensional structure. The infrared spectroscopy, thermal stability and photoluminescence of the three complexes were studied. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Investigation on modification of Ru/CNTs catalyst for the generation of COx-free hydrogen from ammonia

Abstract: The modification of Ru/CNTs (CNTs denotes carbon nanotubes) with rare earth, alkali, and alkaline earth compounds were systematically studied. The loading of modifying agents leads to decrease in pore volume and surface area; but improvement in thermal stability of Ru/CNTs. The size and morphology of Ru particles are not affected by the modification. For the catalysts modified by metal nitrates, activities were found in the order of K–Ru>Na–Ru>Li–Ru>Ce–Ru>Ba–Ru>La–Ru>Ca–Ru>Ru, signifying that within the same groups (K, Na and Li; Ba and Ca), the higher the electronegativity of the promoter, the lower is the NH3 conversion. Of all the potassium salts adopted, KNO3, KOH, and KCO3 show similar promotional effect, suggesting that KOH is the active promoter for catalytic activity. The maximum promotional effect was observed at an atomic ratio of K/Ru=2. The electron-withdrawing groups, F−1, Cl−1, Br−1, SO42−, and PO43− are inhibitors of Ru catalysts. The results of N2-TPD investigation revealed that the promotional effects of a modifier is a combined result of: (i) enhancing combinative desorption of nitrogen atoms, and (ii) decreasing of the apparent activation energy of the decomposition reaction.

The extended Perdew-Burke-Ernzerhof functional with improved accuracy for thermodynamic and electronic properties of molecular systems

Abstract: Density functional theory (DFT) has become the method of choice for many applications of quantum mechanics to the study of the electronic properties of molecules and solids. Despite the enormous progress in improving the functionals, the current generation is inadequate for many important applications. As part of the quest of finding better functionals, we consider in this paper the Perdew-Burke-Ernzerhof (PBE) functional, which we believe to have the best theoretical foundation, but which leads to unacceptable errors in predicting thermochemical data (heats of formation) of molecular systems [mean absolute deviation (MAD)=16.9 kcal/mol against the extended G2 data set of 148 molecules]. Much improved thermochemistry is obtained with hybrid DFT methods that include part of the Hartree-Fock exchange [thus B3LYP (Becke's three parameter scheme combining Hartree-Fock exchange, Becke gradient corrected exchange functional and Lee-Yang-Parr correlational functional) with MAD=3.1 kcal/mol and PBE0 (Perdew's hybrid scheme using PBE exchange and correlation functionals) with MAD=4.8 kcal/mol]. However we wish to continue the quest for a pure density-based DFT. Thus we optimized the four free parameters (µ, kappa, alpha, and beta) in PBE theory against experimental atomic data and the van der Waals interaction properties of Ne2, leading to the xPBE extended functional, which significantly outperforms PBE for thermochemical properties MAD reduced to 8.0 kcal/mol while being competitive or better than PBE for predictions of geometric parameters, ionization potentials, electron affinities, and proton affinities and for the description of van der Waals and hydrogen bond interactions. Thus xPBE significantly enlarges the field of applications available for pure DFT. The functional forms thus obtained for the exchange and correlational functionals may be useful for discovering new improved functionals or formalisms.

Molecularly Imprinted Sol−Gel Nanotubes Membrane for Biochemical Separations

Abstract: In this study, we report a simple procedure for applying molecular imprinting functional groups to the inner surfaces of the template-synthesized sol−gel nanotubes for chemical separation of estrone. The silica nanotubes were synthesized within the pores of nanopore alumina template membranes using a sol−gel method by simultaneous hydrolysis of a silica monomer−imprinted molecule complex and tetraethoxysilane (TEOS). A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of the isocyanate group of 3-(triethoxysilyl)propyl isocyanate and a phenol moiety of estrone to form a thermally cleavable urethane bond. This allowed us to remove the imprinted estrone by simple thermal reaction and to simultaneously introduce functional groups into the cavity formed by the silica nanotubes. Experiments indicated that estrone could be bound selectively by such an approach and have a binding affinity of 864 ± 137 (n = 3).

Fabrication of core-shell Au-Pt nanoparticle film and its potential application as catalysis and SERS substrate

Abstract: In this paper we report the rational design and fabrication of high-quality core-shell Au-Pt nanoparticle film. Such film shows highly efficient catalytic properties and excellent surface-enhanced Raman scattering (SERS) ability.

Synthesis and properties of tadpole-shaped gold nanoparticles

Abstract: In this communication, gold nanoparticles with a tadpole shape were synthesized by a simple aqueous-phase chemical method. The unusual three-dimensional and crystallized structures were demonstrated by TEM, AFM, and HRTEM methods. The SEM and UV-visible absorption measurements and electrophoresis experiments revealed that the tadpoles had novel optical and electrical properties. These attractive structures and properties are expected to find uses in many fields such as electrics, optics, electrochemistry, and biological sensing.

Simulation of water exchange in Jiaozhou Bay by average residence time approach

Abstract: A dispersion model coupled with the Princeton Ocean Model was used to estimate the average residence time of the water in Jiaozhou Bay. The tidal simulation agreed quite well with drift experiments and water elevation observations at the Dagang tide station in the east coast of the bay. In particular, in situ measurements of 228Ra and salinity were carried out to calibrate the dispersion model. The modelled average residence time was about 52 days, ranging from less than 20 days in the deep part near the bay channel, the only passage connecting the bay to the Yellow Sea, to over 100 days in the shallow area in the northwest. The spatial difference of average residence time was controlled by tidal residual currents and the distance to the bay channel. The modelled tidal exchange rate was uneven in the bay, and consistent with 228Ra observations. The temporal evolution of the passive tracer accords with the evolution of the rain fraction after the rainstorm in August 2001.