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171.
Schrade A Cao Z Landfester K Ziener U 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):6689-6700
Well-defined raspberry-like nanocapsules were prepared by the combination of Pickering emulsification and solvent displacement technique by using silica particles as stabilizer and hexadecane (HD) as soft template. The formation of the capsule morphology is caused by the phase separation of poly(styrene-co-4-vinyl pyridine) (poly(St-co-4-VP)) in the droplets due to the diffusion of good solvent for the (co)polymer to the aqueous continuous phase. The size of capsules was successfully reduced from tens of micrometers in the dispersion by simply stirring to the nanorange by the employment of sonication and Ostwald ripening. The formation of silica-particles-armored nanocapsules was confirmed by transmission electron microscopy (TEM), high-resolution scanning electron microscopy (HRSEM), dynamic light scattering (DLS), and zeta potential measurement. The colloidal stability and particle properties, including size and morphology, depend on the amount of HD, and copolymers, the sonication time, the dispersion pH value, the type of solvent, and the copolymer composition. 相似文献
172.
A. Al-Kahlout S. Heusing T. Mueller N. Aldahoudi M. Quilitz P. W. de Oliveira 《Journal of Sol-Gel Science and Technology》2011,59(3):532-538
Transparent semiconducting ITO:Ti thin films, prepared by a sol–gel process, has been deposited by spin-coating technique
onto alkali-free glass substrates. The as-coated films were annealed in ambient air at 550 °C for 1 h and further annealed
in a reducing atmosphere. The influences of the Ti content in the sol on the surface morphology, microstructure, optical properties
and electrical resistivity have been investigated. These properties were found to depend on the Ti content in the coating
sol. Ti addition led to dense smooth layers with larger crystallite size (20–30 nm). Double layers synthesized with Ti:ITO = 0.53 wt%
and submitted to reducing treatment in forming gas exhibited the lowest sheet resistance R□ = 60 Ω□ with an average transmittance of 87% at 550 nm. 相似文献
173.
Froimowicz P Klinger D Landfester K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(44):12465-12475
The use of reversible photo-cross-linkable nanoparticles as nano building blocks for the formulation of nanostructured self-healing thin hydrogel films is shown for the first time. This strategy for the fabrication of autonomous self-healing coatings consisted of various microgels bearing surface cinnamate moieties. The nanoparticles were formed by miniemulsion copolymerization, which was followed by surface functionalization with the cinnamate groups. These nanoparticles were then used to form films by drop-casting, followed by interparticle photo-cross-linking polymerization through the light-induced forward dimerization reaction of the previously incorporated cinnamate groups. The reversibility of this macroscopic network formation was also demonstrated by photoinducing the backward dimerization reaction and carrying out several cycles of photoinduced cross-linking and de-cross-linking. The self-healing ability through swelling of these films following surface damage was also demonstrated. Finally, the ability of these self-healing macroscopic films to incorporate additives of different chemical nature before photo-cross-linking was evaluated. 相似文献
174.
Bissinger P Braunschweig H Damme A Dewhurst RD Kupfer T Radacki K Wagner K 《Journal of the American Chemical Society》2011,133(47):19044-19047
A novel NHC adduct of a dihalodiborane(4), 1, is reduced by KC(8) with formation of the five-membered boracycle 2. The reaction most likely proceeds via C-H insertion of an intermediate NHC-stabilized free bora-borylene species. 相似文献
175.
Real-time PCR (qPCR) is the principal technique for the quantification of pathogen biomass in host tissue, yet no generic
methods exist for the determination of the limit of quantification (LOQ) and the limit of detection (LOD) in qPCR. We suggest
using the Youden index in the context of the receiver operating characteristic (ROC) curve analysis for this purpose. The
LOQ was defined as the amount of target DNA that maximizes the sum of sensitivity and specificity. The LOD was defined as
the lowest amount of target DNA that was amplified with a false-negative rate below a given threshold. We applied this concept
to qPCR assays for Fusarium verticillioides and Fusarium proliferatum DNA in maize kernels. Spiked matrix and field samples characterized by melting curve analysis of PCR products were used as
the source of true positives and true negatives. On the basis of the analysis of sensitivity and specificity of the assays,
we estimated the LOQ values as 0.11 pg of DNA for spiked matrix and 0.62 pg of DNA for field samples for F. verticillioides. The LOQ values for F. proliferatum were 0.03 pg for spiked matrix and 0.24 pg for field samples. The mean LOQ values correspond to approximately eight genomes
for F. verticillioides and three genomes for F. proliferatum. We demonstrated that the ROC analysis concept, developed for qualitative diagnostics, can be used for the determination
of performance parameters of quantitative PCR. 相似文献
176.
An automated real-time method for determination of ISE steady state value and response time is developed, following most recent IUPAC recommendations. Specifically, detection of the ‘steady state’ is related to (1) the time derivative of the emf as it reaches a limiting value (ΔE/Δtlimit, e.g., 0.1–1.0 mV min−1) and (2) the duration of time for which the absolute value of the time derivative remains less than this limiting value (stability window, denoted winst). A suite of representative ISEs, including glass, solid state, and polymer-based electrodes, is examined to determine sensitivity of results to parameterization choice. Measurements taken over a wide range of concentration values and in un-processed samples (i.e., without use of ionic strength adjustment) provide insight into behavior of ISEs in applications where analyte concentrations span a wide range and/or sample pre-processing may not be an option, e.g., use of sensors for in situ environmental sampling. Results show that declared steady state emf is strongly sensitive to variations in ΔE/Δtlimit but relatively unaffected by changes in the stability window when winst ≥30 s. Linearity of calibration curves produced, quantified by root mean squared error (RMSE) against a linear fit, improves as ΔE/Δtlimit decreases, however the percentage of measurements which reach a declared steady state within the prescribed sample window (∼6.5 min) falls with corresponding decreases in the ΔE/Δtlimit parameter. Response time, defined as the time required to reach declared steady emf, is also a strong function of parameterization. Dependence of response times on sample composition and/or ISE membrane composition and type are also discussed; results for ISEs in samples comprised exclusively of interfering ions are included. In general, limiting emf derivatives of {0.25–0.4 mV min−1} and stability windows of {30–40 s} achieve both good analytical accuracy and compliance with potentially short sampling window requirements. Methodology based on use of these parameters can improve sampling speed and accuracy as well as promote inter-comparison of data and ISE characterizations among research teams. 相似文献
177.
A series of trialkylphosphine-stabilized copper(I) phenylchalcogenolate complexes [(R(3)P)(m)(CuEPh)(n)] (R = Me, Et, (i)Pr, (t)Bu; E = S, Se, Te) has been prepared and structurally characterized by X-ray diffraction. Structures were found to be mono-, di-, tri-, tetra-, hexa-, hepta-, or decanuclear, depending mainly on size and amount of phosphine ligand. Several structural details were observed, including unusually long Cu-E bonds or secondary Cu-E connections, μ(4)-bridging, and planar bridging chalcogenolate ligands. Relatively rigid Cu-E-C angles were found to be of significant influence on the flexible molecular structures, especially for bridging chalcogenolate ligands, since in these cases a correlation results between the Cu-E-Cu angles and the inclination of the E-C bonds to their Cu-E-Cu planes. We further address some of these phenomena by means of density functional computations. 相似文献
178.
We have recently shown [Proc. Natl. Acad. Sci. U.S.A. 107, 4528 (2010)] that the discreteness and stochasticity of an electron transfer event on a resistively coupled nanoelectrode causes mesoscopic fluctuations in time of the electrode potential. These fluctuations give rise to a time-average faradaic current density substantially larger than in the macroscopic limit. The deviations result to a large extent from the potentiostatic control, which imposes a constraint on the evolution of the electrode potential that leads to non-normal distributions. The degree of freedom of the electrode potential requires a resistance between nanoelectrode and metallic support. In this article, we study the dependence of the mesoscopic stochastic dynamics on this resistance (assumed to be ohmic). We show that the enhancement of the reaction rate vanishes in both limits, zero and infinite resistance. The distribution of the electrode potential continuously transforms from a normal distribution at infinite resistance (the galvanostatic limit), through a more and more peaked distribution with increasingly important rare events to the deterministic behavior at zero resistance. 相似文献
179.
180.
Holger Braunschweig Manuela Gross Katharina Kraft 《Journal of organometallic chemistry》2011,696(2):568-571
The paramagnetic ansa-niobocene [(Me2Si)2(η5-C5H4)2NbCl2] (1) was obtained from the reaction of Li2[(Me2Si)2(C5H4)2] with [NbCl4(thf)2]. Further treatment with Li[AlH4] yielded [(Me2Si)2(η5-C5H4)2NbH3] (3), which is prone to decomposition within a few days at room temperature both in solution and in the solid-state, thus affording primarily an insoluble black material. However, after heating or irradiation of a solution of 3 small quantities of the dimeric niobium hydride species, [(Me2Si)2{μ-(η1:η5-C5H3)}(η5-C5H4)NbH]2 (4), were isolated and characterized by X-ray diffraction. 相似文献