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71.
Men Y Rieger J Roth SV Gehrke R Kong X 《Langmuir : the ACS journal of surfaces and colloids》2006,22(20):8285-8288
A polymer dispersion consisting of soft latex spheres with a diameter of 135 nm was used to produce a crystalline film with face-centered cubic (fcc) packing of the spheres. Different from conventional small-molecule and hard-sphere colloidal crystals, the crystalline latex film in the present case is soft (i.e., easily deformable). The structural evolution of this soft colloidal latex film under stretching was investigated by in-situ synchrotron ultra-small-angle X-ray scattering. The film exhibits polycrystalline scattering behavior corresponding to fcc structure. Stretching results not only in a large deformation of the crystallographic structure but also in considerable nonaffine deformation at high draw ratios. The unexpected nonaffine deformation was attributed to slippage between rows of particles and crystalline grain boundaries. The crystalline structure remains intact even at high deformation, suggesting that directional anisotropic colloidal crystallites can be easily produced. 相似文献
72.
PLD-assisted VLS growth of aligned ferrite nanorods, nanowires, and nanobelts-synthesis, and properties 总被引:4,自引:0,他引:4
Morber JR Ding Y Haluska MS Li Y Liu JP Wang ZL Snyder RL 《The journal of physical chemistry. B》2006,110(43):21672-21679
We report here a systematic synthesis and characterization of aligned alpha-Fe2O3 (hematite), epsilon-Fe2O3, and Fe3O4 (magnetite) nanorods, nanobelts, and nanowires on alumina substrates using a pulsed laser deposition (PLD) method. The presence of spherical gold catalyst particles at the tips of the nanostructures indicates selective growth via the vapor-liquid-solid (VLS) mechanism. Through a series of experiments, we have produced a primitive "phase diagram" for growing these structures based on several designed pressure and temperature parameters. Transmission electron microscopy (TEM) analysis has shown that the rods, wires, and belts are single-crystalline and grow along <111>m or <110>h directions. X-ray diffraction (XRD) measurements confirm phase and structural analysis. Superconducting quantum interference device (SQUID) measurements show that the iron oxide structures exhibit interesting magnetic behavior, particularly at room temperature. This work is the first known report of magnetite 1D nanostructure growth via the vapor-liquid-solid (VLS) mechanism without using a template, as well as the first known synthesis of long epsilon-Fe2O3 nanobelts and nanowires. 相似文献
73.
74.
Multidimensional nano-HPLC coupled with tandem mass spectrometry for analyzing biotinylated proteins
Jens Sproß Sebastian Brauch Friedrich Mandel Moritz Wagner Stephan Buckenmaier Bernhard Westermann Andrea Sinz 《Analytical and bioanalytical chemistry》2013,405(7):2163-2173
Multidimensional high-performance liquid chromatography (HPLC) is a key method in shotgun proteomics approaches for analyzing highly complex protein mixtures by complementary chromatographic separation principles. Here, we describe an integrated 3D-nano-HPLC/nano-electrospray ionization quadrupole time-of-flight mass spectrometry system that allows an enzymatic digestion of proteins followed by an enrichment and subsequent separation of the created peptide mixtures. The online 3D-nano-HPLC system is composed of a monolithic trypsin reactor in the first dimension, a monolithic affinity column with immobilized monomeric avidin in the second dimension, and a reversed phase C18 HPLC-Chip in the third dimension that is coupled to a nano-ESI-Q-TOF mass spectrometer. The 3D-LC/MS setup is exemplified for the identification of biotinylated proteins from a simple protein mixture. Additionally, we describe an online 2D-nano-HPLC/nano-ESI-LTQ-Orbitrap-MS/MS setup for the enrichment, separation, and identification of cross-linked, biotinylated species from chemical cross-linking of cytochrome c and a calmodulin/peptide complex using a novel trifunctional cross-linker with two amine-reactive groups and a biotin label. Figure
Schematic representations of the online 3D-nano-HPLC/nano-ESI-Q-TOF-MS/MS setup; LP loading pump, NP nano-pump 相似文献
75.
Maotong Xu Andrew R. Jupp Douglas W. Stephan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3586-3590
The analogy of the reactivity of group 1 phosphides to that of FLPs is further demonstrated by reactions with CO, affording a new synthetic route to acyl‐phosphide anions. The reaction of [K(18‐crown‐6)][PtBu2] ( 1 ) with CO affords [(18‐crown‐6)K?THF2][Z‐tBuP=C(tBu)O] ( 2?THF2 ) as the major product, and the minor product [K6(18‐crown‐6)][(tBu2PCO)2]3 ( 3 ). Species 2 reacts with either BPh3 or additional CO to give [K(18‐crown‐6)][(Ph3B)tBuPC(tBu)O] ( 4 ) and [K(18‐crown‐6)][(OCtBu)2P] ( 5 ), respectively. The acyl‐phosphide anion 2 is thought to be formed by a photochemically induced radical process involving a transient species with triplet carbene character, prompting 1,2‐tert‐butyl group migration. A similar process is proposed for the subsequent reaction of 2 with CO to give 5 . 相似文献
76.
Lukas Fischer Alexander K. Strzelczyk Nils Wedler Christian Kropf Stephan Schmidt Laura Hartmann 《Chemical science》2020,11(36):9919
Catechol and amine residues, both abundantly present in mussel adhesion proteins, are known to act cooperatively by displacing hydration barriers before binding to mineral surfaces. In spite of synthetic efforts toward mussel-inspired adhesives, the effect of positioning of the involved functional groups along a polymer chain is not well understood. By using sequence-defined oligomers grafted to soft hydrogel particles as adhesion probes, we study the effect of catechol–amine spacing, as well as positioning relative to the oligomer terminus. We demonstrate that the catechol–amine spacing has a significant effect on adhesion, while shifting their position has a small effect. Notably, combinations of non-charged amides and catechols can achieve similar cooperative effects on adhesion when compared to amine and catechol residues. Thus, these findings provide a blueprint for the design of next generation mussel-inspired adhesives.The catechol driven adhesion of precision macromolecules on glass surfaces is quantified by soft colloidal probe readout. Catechol moieties are shown to synergize with amine and amide residues depending on residue spacing and residue order. 相似文献
77.
Martin Piesch Dr. Fabian Dielmann Stephan Reichl Prof. Dr. Manfred Scheer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1518-1524
A systematic study on the reactivity of the triple-decker complex [(Cp’’’Co)2(μ,η4:η4-C7H8)] ( A ) (Cp’’’=1,2,4-tritertbutyl-cyclopentadienyl) towards sandwich complexes containing cyclo-P3, cyclo-P4, and cyclo-P5 ligands under mild conditions is presented. The heterobimetallic triple-decker sandwich complexes [(Cp*Fe)(Cp’’’Co)(μ,η5:η4-P5)] ( 1 ) and [(Cp’’’Co)(Cp’’’Ni)(μ,η3:η3-P3)] ( 3 ) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)5} fragments, leading to the complexes [(Cp*Fe)(Cp’’’Co)(μ3,η5:η4:η1-P5){W(CO)5}] ( 2 a ), [(Cp*Fe)(Cp’’’Co)(μ4,η5:η4:η1:η1-P5){(W(CO)5)2}] ( 2 b ), and [(Cp’’’Co)(Cp’’’Ni)(μ3,η3:η2:η1-P3){W(CO)5}] ( 4 ), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp’’’Ni)2(μ,η2:η2-P2)] ( 5 ). All compounds were fully characterized using single-crystal X-ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis. 相似文献
78.
Lehenmeier MW Bruckmeier C Klaus S Dengler JE Deglmann P Ott AK Rieger B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(32):8858-8869
The homogeneous dinuclear zinc catalyst going back to the work of Williams et al. is to date the most active catalyst for the copolymerisation of cyclohexene oxide and CO2 at one atmosphere of carbon dioxide. However, this catalyst shows no copolymer formation in the copolymerisation reaction of propylene oxide and carbon dioxide, instead only cyclic carbonate is found. This behaviour is known for many zinc‐based catalysts, although the reasons are still unidentified. Within our studies, we focus on the parameters that are responsible for this typical behaviour. A deactivation of the catalyst due to a reaction with propylene oxide turns out to be negligible. Furthermore, the catalyst still shows poly(cyclohexene carbonate) formation in the presence of cyclic propylene carbonate, but the catalyst activity is dramatically reduced. In terpolymerisation reactions of CO2 with different ratios of cyclohexene oxide to propylene oxide, no incorporation of propylene oxide can be detected, which can only be explained by a very fast back‐biting reaction. Kinetic investigations indicate a complex reaction network, which can be manifested by theoretical investigations. DFT calculations show that the ring strains of both epoxides are comparable and the kinetic barriers for the chain propagation even favour the poly(propylene carbonate) over the poly(cyclohexene carbonate) formation. Therefore, the crucial step in the copolymerisation of propylene oxide and carbon dioxide is the back‐biting reaction in the case of the studied zinc catalyst. The depolymerisation is several orders of magnitude faster for poly(propylene carbonate) than for poly(cyclohexene carbonate). 相似文献
79.
Katrin Loeschner Jana Navratilova Carsten Købler Kristian Mølhave Stephan Wagner Frank von der Kammer Erik H. Larsen 《Analytical and bioanalytical chemistry》2013,405(25):8185-8195
A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry (ICP-MS) in single particle mode were used to characterize the number-based size distribution of AgNPs in the meat digestate. Because similar size distributions were found in the meat digestate and in the aqueous suspension of AgNPs used for spiking the meat, it was shown that no detectable dissolution of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF4) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two smaller peaks eluting close to the void volume. The recovery of silver contained in the large AgNP peak was around 80 %. Size determination of AgNPs in the meat matrix, based on external size calibration of the AF4 channel, was hampered by non-ideal (early elution) behavior of the AgNPs. Single particle ICP-MS was applied for determination of the number-based particle size distribution of AgNPs in collected fractions. The presented work describes for the first time the coupling of AF4 and ICP-MS for AgNP separation in a food matrix. 相似文献
80.