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971.
972.
Michael Höfner Björn Kobin Prof. Dr. Stefan Hecht Prof. Dr. Fritz Henneberger 《Chemphyschem》2014,15(17):3805-3808
We investigate the coupling of ladder‐type quarterphenyl to the photon modes of a dielectric ZrOx/SiOx microcavity at ultraviolet wavelengths. For a relatively long cavity (≈10 μm) with high‐reflectivity mirrors (0.998), optically pumped laser action is demonstrated in the weak‐coupling regime. We observe single‐mode operation with a threshold of 0.4 mJ cm?2. Strong coupling is achieved by using a short λ/2 cavity. We find pronounced anti‐crossing features of the molecular (0,0) and (0,1) vibronic transitions and the cavity mode in angle‐dependent reflectivity measurements providing Rabi splittings of (90±10) meV. All these features occur spectrally resonant to the exciton transition of ZnO demonstrating the potential of ladder‐type oligo(p‐phenylene)s for the construction of inorganic/organic hybrid microcavities. 相似文献
973.
J. Huub Adriaanse Sven H.C. Askes Yorrick van Bree Stefan van Oudheusden Eelke D. van den Bos Esref Günay Ilpo Mutikainen Urho Turpeinen Gerard A. van Albada Jaap G. Haasnoot Jan Reedijk 《Polyhedron》2009,28(14):3143-3149
A variety of new coordination compounds with transition-metal salts and the ligand trimethyl[1,2,4]triazolo[1,5-a]pyrimidine (abbreviated as tmtp) is described, together with several of their 3D crystal structures and spectroscopic and magnetic properties. The compounds were selected based on the coordination ability of the counterion, halide, nitrate, sulfate, thiocyanate and perchlorate. The formed coordination compounds and their coordination numbers were found to be strongly dependent on both the cation and the used counter-anion. The several compounds studied have the following structural formulae: [CuCl2(tmtp)2], [CuBr2(tmtp)2], [ZnBr2(tmtp)2], [Cu(NO3)2(tmtp)2], [CuSO4(tmtp)2]2(H2O)(MeOH), [Cu(H2O)(NCS)2(tmtp)2], [Zn(NCS)2(tmtp)2], [Cd(NCS)2(tmtp)2] and [M(H2O)2(tmtp)4](BF4)2, in which M = Co, Ni, Zn.The new coordination compounds have been further characterized by NMR, (far-)IR and LF spectra, as well as by C, H, N element analyses, and EPR spectra for the Cu(II) compounds. The coordination around the metal varies from 4 (Zn, Cu), via 5 (Cu) to 6 (for Co, Cu and Cd). The anions usually complete the coordination sphere; only the Co and Zn compounds with the tetrafluoridoborate anions have no coordinated anions, but water ligands complete the octahedral coordination sphere. In the 5-coordinated [Cu(H2O)(NCS)2(tmtp)2] water completes the square pyramid geometry. 相似文献
974.
Martin Röder Stefan Vieths Thomas Holzhauser 《Analytical and bioanalytical chemistry》2009,395(1):103-109
Lateral flow devices (LFDs) are qualitative immunochromatographic tests for the rapid and specific detection of target analytes.
We investigated commercially available LFDs for their ability to detect potentially allergenic peanut and hazelnut in raw
cookie dough and chocolate, two important food matrices in the industrial production of cookies. Each three commercial LFDs
for the detection of hazelnut and peanut were performed according to the manufacturers’ instructions. All LFDs had comparably
satisfactory specificity that was investigated with a variety of characteristic foods and food ingredients used in the production
of cookies. In concordance with hazelnut-specific enzyme-linked immunosorbent assays (ELISAs), walnut was the most cross-reactive
food for hazelnut-specific LFD. The sensitivity was verified in raw cookie doughs and chocolates that were either spiked with
peanut or hazelnut between 1 and 25 mg/kg, respectively. Two hazelnut-specific LFDs detected hazelnut at a level of 3.5 mg/kg
in both matrices, whereas the third LFD detected hazelnut at a level of 3.9 mg/kg in dough and 12.5 mg/kg in chocolate. Two
peanut-specific LFDs detected peanut at a level of 1 mg/kg in both matrices. The third LFD detected peanut at a level of 14.2 mg/kg
in chocolate and 4 mg/kg in dough. In conclusion, specific and sensitive LFD were identified for each hazelnut and peanut,
having a level of sensitivity that is comparable to commercial ELISA for the investigated matrices. Such sensitive, specific,
and rapid tests are useful analytical tools for allergen screening and sanitation in the industrial manufacture of foods. 相似文献
975.
Cell Tracking with Caged Xenon: Using Cryptophanes as MRI Reporters upon Cellular Internalization 下载免费PDF全文
Stefan Klippel Jörg Döpfert Dr. Jabadurai Jayapaul Martin Kunth Federica Rossella Matthias Schnurr Dr. Christopher Witte Dr. Christian Freund Dr. Leif Schröder 《Angewandte Chemie (International ed. in English)》2014,53(2):493-496
Caged xenon has great potential in overcoming sensitivity limitations for solution‐state NMR detection of dilute molecules. However, no application of such a system as a magnetic resonance imaging (MRI) contrast agent has yet been performed with live cells. We demonstrate MRI localization of cells labeled with caged xenon in a packed‐bed bioreactor working under perfusion with hyperpolarized‐xenon‐saturated medium. Xenon hosts enable NMR/MRI experiments with switchable contrast and selectivity for cell‐associated versus unbound cages. We present MR images with 103‐fold sensitivity enhancement for cell‐internalized, dual‐mode (fluorescence/MRI) xenon hosts at low micromolar concentrations. Our results illustrate the capability of functionalized xenon to act as a highly sensitive cell tracer for MRI detection even without signal averaging. The method will bridge the challenging gap for translation to in vivo studies for the optimization of targeted biosensors and their multiplexing applications. 相似文献
976.
The Activation of Sulfur Hexafluoride at Highly Reduced Low‐Coordinate Nickel Dinitrogen Complexes 下载免费PDF全文
Dipl.‐Chem. Patrick Holze Dipl.‐Chem. Bettina Horn Prof. Dr. Christian Limberg Dipl.‐Chem. Corinna Matlachowski Dr. Stefan Mebs 《Angewandte Chemie (International ed. in English)》2014,53(10):2750-2753
The greenhouse gas sulfur hexafluoride is the common standard example in the literature of a very inert inorganic small molecule that is even stable against O2 in an electric discharge. However, a reduced β‐diketiminate nickel species proved to be capable of converting SF6 into sulfide and fluoride compounds at ambient standard conditions. The fluoride product complex features an unprecedented [NiF]+ unit, where the Ni atom is only three‐coordinate, while the sulfide product exhibits a rare almost linear [Ni(μ‐S)Ni]2+ moiety. The reaction was monitored applying 1H NMR, IR and EPR spectroscopic techniques resulting in the identification of an intermediate nickel complex that gave insight into the mechanism of the eight‐electron reduction of SF6. 相似文献
977.
Back Cover: Cell Tracking with Caged Xenon: Using Cryptophanes as MRI Reporters upon Cellular Internalization (Angew. Chem. Int. Ed. 2/2014) 下载免费PDF全文
978.
Dipl.‐Chem. Robert Göstl Prof. Stefan Hecht 《Angewandte Chemie (International ed. in English)》2014,53(33):8784-8787
The on‐going need for feature miniaturization and the growing complexity of structures for use in nanotechnology demand the precise and controlled formation of covalent bonds at the molecular level. Such control requires the use of external stimuli that offer outstanding spatial, temporal, as well as energetic resolution. Thus, photoaddressable switches are excellent candidates for creating a system that allows reversible photocontrol over covalent chemical connection and disconnection. Here we show that the formation of covalent bonds between two reagents and their scission in the resulting product can be controlled exclusively by illumination with differently colored light. A furyl‐substituted photoswitchable diarylethene was shown to undergo a reversible Diels–Alder reaction with maleimide to afford the corresponding Diels–Alder adduct. Our system is potentially applicable in any field already relying on the benefits of reversible Diels–Alder reactions. 相似文献
979.
De Witte PA Hernando J Neuteboom EE van Dijk EM Meskers SC Janssen RA van Hulst NF Nolte RJ García-Parajó MF Rowan AE 《The journal of physical chemistry. B》2006,110(15):7803-7812
The synthesis and characterization of perylenediimide polyisocyanides is reported. In addition to short oligomers, our synthetic approach results in the formation of extremely long, well-defined, and rigid perylenediimide polymers. Ordering and close-packing of the chromophores in these long polymers is guaranteed by attachment to a polyisocyanide backbone with amino acid side chains. Hydrogen bonding interactions between those groups stabilize and rigidify the helical polymer structure. The rodlike nature of the synthesized long perylenediimide pendant polyisocyanides as well as the helical arrangement of the chromophores is demonstrated by means of atomic force microscopy. Remarkably, polymer fibers up to 1 mum in length have been visualized, containing several thousands of perylenediimide molecules. Circular dichroism spectroscopy reveals the chiral organization of the chromophore units in the polymer, whereas absorption and emission measurements prove the occurrence of excited-state interactions between those moieties due to the close packing of the chromophore groups. However, an intricate optical behavior is encountered in bulk as a result of the coexistence of short oligomers and long polymers of perylenediimide, a situation subsequently uncovered by means of single-molecule experiments. Individual long helical perylenediimide polyisocyanides exhibit a typical red-shifted fluorescence spectrum, which, together with depolarized emission continuously decreasing in time, demonstrate that fluorescence arises from multiple excimer-like species in the polymer. Upon continuous irradiation of these long polymers, a fast decay in fluorescence lifetime is observed, a situation explained by photoinduced creation of quenching sites. Radical/ion formation by intramolecular electron transfer between close-by perylenediimide moieties is the most probable mechanism for this process. Appropriate control of the electron-transfer process might open the possibility of applying these polymers as perylenediimide-based supramolecular nanowires. 相似文献
980.
Phosphorescent iridium(III) complexes are being widely explored for their utility in diverse photophysical applications. The performance of these materials in such roles depends heavily on their excited-state properties, which can be tuned through ligand and substituent effects. This concept article focuses on methods for synthetically tailoring the properties of bis-cyclometalated iridium(III) materials, and explores the factors governing the nature of their lowest excited state. 相似文献