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41.
Heltberg Mathias L. Krishna Sandeep Jensen Mogens H. 《Journal of statistical physics》2017,167(3-4):792-805
Journal of Statistical Physics - We study the dynamics in a system of coupled oscillators when Arnold Tongues overlap. By varying the initial conditions, the deterministic system can be attracted... 相似文献
42.
Tyrsted C Pauw BR Jensen KM Becker J Christensen M Iversen BB 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(18):5759-5766
Understanding nanoparticle-formation reactions requires multi-technique in situ characterisation, since no single characterisation technique provides adequate information. Here, the first combined small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering (WAXS)/total-scattering study of nanoparticle formation is presented. We report on the formation and growth of yttria-stabilised zirconia (YSZ) under the extreme conditions of supercritical methanol for particles with Y(2)O(3) equivalent molar fractions of 0, 4, 8, 12 and 25 %. Simultaneous in situ SAXS and WAXS reveals a quick formation (seconds) of sub-nanometre amorphous material forming larger agglomerates with subsequent slow crystallisation (minutes) into nanocrystallites. The amount of yttria dopant is shown to strongly affect the crystallite size and unit-cell dimensions. At yttria-doping levels larger than 8 %, which is known to be the stoichiometry with maximum ionic conductivity, the strain on the crystal lattice is significantly increased. Time-resolved nanoparticle size distributions are calculated based on whole-powder-pattern modelling of the WAXS data, which reveals that concurrent with increasing average particle sizes, a broadening of the particle-size distributions occur. In situ total scattering provides structural insight into the sub-nanometre amorphous phase prior to crystallite growth, and the data reveal an atomic rearrangement from six-coordinated zirconium atoms in the initial amorphous clusters to eight-coordinated zirconia atoms in stable crystallites. Representative samples prepared ex situ and investigated by transmission electron microscopy confirm a transformation from an amorphous material to crystalline nanoparticles upon increased synthesis duration. 相似文献
43.
Suitably functionalized vinylheptafulvenes (VHFs) act as thermoswitches undergoing ring closure to the corresponding dihydroazulenes (DHAs). Here we present the synthesis of a new such thermoswitch incorporating two heptafulvene rings on a dicyanoethylene unit. The synthetic protocol explores both the tropylium species as an electrophile and as a leaving group in the generation of the heptafulvene units. The thermally induced ring closure was enhanced as a result of two accessible sites for the reaction to occur. 相似文献
44.
C Tyrsted KM Ornsbjerg Jensen ED Bøjesen N Lock M Christensen SJ Billinge B Brummerstedt Iversen 《Angewandte Chemie (International ed. in English)》2012,51(36):9030-9033
Supercritical growth: The formation and evolution of ceria nanoparticles during hydrothermal synthesis was investigated by in?situ total scattering and powder diffraction. The nucleation of pristine crystalline ceria nanoparticles originated from previously unknown cerium dimer complexes. The nanoparticle growth was highly accelerated under supercritical conditions. 相似文献
45.
Anders?LundEmail author Karin?Vels?Hansen Torben?Jacobsen Mogens?Mogensen 《Journal of Solid State Electrochemistry》2012,16(3):1161-1168
Porous platinum electrodes impregnated with Gd
x
Ce1−x
O2−δ (CGO) are investigated to characterise how nano-sized CGO grains affect the oxygen reaction. Impedance measurements were
performed at temperatures between 450 and 750 °C and at oxygen partial pressures of 0.2 and 5 × 10−5 bar for electrodes with various CGO loadings and electrodes annealed at various temperatures. The morphology was characterised
by scanning electron microscopy and the CGO grain size was determined from X-ray diffraction peak broadening. The results
showed that the polarisation resistance decreased with increasing CGO loading and increasing annealing temperature. CGO facilitates
transport of oxygen ions thereby increasing the effective triple-phase boundary. 相似文献
46.
Rebecka M. L. Werchmeister Kent Kammer Hansen Mogens Mogensen 《Journal of Solid State Electrochemistry》2012,16(2):703-714
The possibility of using electrochemical cells for removal of NO
x
from an exhaust gas with excess O2 has been examined. (La1−x
Sr
x
)
s
MnO3 (LSM) and ceria doped with Pr or Gd were selected as electrode materials and investigated in three-electrode cells. The electrodes
were characterised electrochemically with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and the
gas composition monitored while the electrodes were polarised. The electrodes of (La0.5Sr0.5)0.99MnO3 (LSM50) and Ce0.8Pr0.2O2−δ
exhibit higher current densities in 0.1% NO in Ar than in air at 300 to 400 °C during CV. This indicates some apparent selectivity
towards NO compared to O2. The electrodes can remove NO, when polarised to at least −0.6 V vs. Pt/Air at 600 °C, and EIS measurements under polarisation
indicate that the kinetics of the electrodes change, when the electrode potential gets below −0.6 V vs. Pt/Air. 相似文献
47.
Bousquet A Ceccato M Hinge M Pedersen SU Daasbjerg K 《Langmuir : the ACS journal of surfaces and colloids》2012,28(2):1267-1275
Thick conductive layers containing anthraquinone moieties are covalently immobilized on gold using redox grafting of the diazonium salt of anthraquinone (i.e., 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate). This grafting procedure is based on using consecutive voltammetric sweeping and through this exploiting fast electron transfer reactions that are mediated by the anthraquinone redox moieties in the film. The fast film growth, which is followed by infrared reflection absorption spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and coverage calculation, results in a mushroom-like structure. In addition to varying the number of sweeps, layer thickness control can easily be exerted through appropriate choice of the switching potential and sweep rate. It is shown that the grafting of the diazonium salt is essentially a diffusion-controlled process but also that desorption of physisorbed material during the sweeping process is essentially for avoiding blocking of the film due to clogging of the electrolyte channels in the film. In general, sweep rates higher than 0.5 V s(-1) are required if thick, porous, and conducting films should be formed. 相似文献
48.
Martina Cacciarini Mogens Brøndsted NielsenElisa Martinez de Castro Lavinia MarinescuMikael Bols 《Tetrahedron letters》2012,53(8):973-976
The green fluorescent protein (GFP) chromophore has been anchored to β-cyclodextrin (βCD) via a copper(I)-catalyzed azide-alkyne cycloaddition. The photophysical properties of this new GFP-CD derivative have been evaluated, showing the formation of a self-inclusion complex and enhancement of fluorescence of the GFP-chromophore covalently bound to the βCD. This enhancement of fluorescence by encapsulation and hence fixation of the chromophore in a binding pocket mimics the effect exerted by the natural protein environment. 相似文献
49.
Pyridyl-based triazole-linked calix[4]arene conjugates, viz. L(1) and L(2), were synthesized and characterized. These two conjugates were shown to be selective and sensitive for Zn(2+) among the 12 metal ions studied in HEPES buffer medium by fluorescence, absorption, and visual color change with the detection limit of ~31 and ~112 ppb, respectively, by L(1) and L(2). Moreover, the utility of the conjugates L(1) and L(2) in showing the zinc recognition in live cells has also been demonstrated using HeLa cells as monitored by fluorescence imaging. The zinc complexes of L(1) and L(2) were isolated, and the structure of [ZnL(1)] has been established by single-crystal XRD and that of [ZnL(2)] by DFT calculations. TDDFT calculations were performed in order to demonstrate the electronic properties of receptors and their zinc complexes. The isolated zinc complexes, viz. [ZnL(1)] and [ZnL(2)], have been used as molecular tools for the recognition of anions on the basis of their binding affinities toward Zn(2+). [ZnL(2)] was found to be sensitive and selective toward phosphate-bearing ions and molecules and in particular to pyrophosphate (PPi) and ATP among the other 18 anions studied; however, [ZnL(1)] was not sensitive toward any of the anions studied. The selectivity has been shown on the basis of the changes observed in the emission and absorption spectral studies through the removal of Zn(2+) from [ZnL(2)] by PPi. Thus, [ZnL(2)] has been shown to detect PPi up to 278 ± 10 ppb at pH 7.4 in aqueous methanolic (1/2 v/v) HEPES buffer. 相似文献
50.
Dessingou J Tabbasum K Mitra A Hinge VK Rao CP 《The Journal of organic chemistry》2012,77(3):1406-1413
The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest. 相似文献