Atmospheric pressure chemical vapour deposition of fluorine‐doped tin(IV) oxide from fluoroalkyltin precursors

Perfluoroalkytin compounds R_(4−n)Sn(R_f)_n (R = Me, Et, Bu, R_f = C₄F₉, n = 1; R = Bu, R_f = C₄F₉, n = 2, 3; R = Bu, R_f = C₆F₁₃, n = 1) have been synthesized, characterized by ¹H, ¹³C, ¹⁹F and ¹¹⁹Sn NMR, and evaluated as precursors for the atmospheric pressure chemical vapour deposition of fluorine‐doped SnO₂ thin films. All precursors were sufficiently volatile in the range 84–136 °C and glass substrate temperatures of ca 550 °C to yield high‐quality films with ca 0.79–2.02% fluorine incorporation, save for Bu₃SnC₆F₁₃, which incorporated <0.05% fluorine. Films were characterized by X‐ray diffraction, scanning electron microscopy, thickness, haze, emissivity, and sheet resistance. The fastest growth rates and highest quality films were obtained from Et₃SnC₄F₉. An electron diffraction study of Me₃SnC₄F₉ revealed four conformations, of which only the two of lowest abundance showed close F Sn contacts that could plausibly be associated with halogen transfer to tin, and in each case it was fluorine attached to either the γ‐ or δ‐carbon atoms of the R_f chain. Copyright © 2005 John Wiley & Sons, Ltd.     

Cyclosporin Measurement – who cares about inaccuracy?

Most medical laboratories measure the immunosuppressive drug cyclosporin using one of a number of commercial immunoassays, or high-performance liquid chromatography (HPLC). The calibration of these assays is based on material supplied by the kit manufacturers or prepared in-house. We have examined inaccuracy for the measurement of cyclosporin in samples spiked to known concentrations and the impact of any inaccuracy on the results for cyclosporin measurement in pooled samples from patients prescribed the drug. The data were from the International Cyclosporin Proficiency Testing Scheme, based on aliquots of cyclosporin-free blood to which known amounts of the drug had been added or aliquots of pooled samples collected from patients receiving cyclosporin. Compared with the results using HPLC, the immunoassays had a median bias which ranged from –4.5% to 8.2% for the spiked samples. When pooled samples from patients were analysed the percentage difference from the measured HPLC value, allowing for assay inaccuracy, was as high as 29.9%. It is concluded that inaccuracy is a factor in between-assay performance for this measurement and that proficiency testing schemes should attempt to put more emphasis on this aspect of assay performance.     

Metallostars: high-nuclearity linearly developed nanostructures containing multiple cluster motifs

Metallostars are complexes in which a single branching site bears a number of metallated arms. Although they are related to metallodendrimers, they have the advantage of being capable of extending in an unlimited sense; in contrast to metallodendrimers, steric interactions decrease with increasing generation number. In this paper a series of polyalkyne stars with four and six arms, based upon a single tetrahedral carbon core and a benzene core, respectively, are reported and their reactions with [Co2(CO)8] to give metallostars that contain multiple [C2Co2(CO)6] motifs are described.     

Structure elucidation with lanthanide-induced shifts. 4—Bound shifts vs relative shifts

The use of lanthanide shift reagents (LSR's) to obtain additional structural information from nuclear magnetic resonance studies has gained widespread acceptance. However, there has not been general agreement with regard to the most appropriate methodology for analysis of the shifted NMR spectra. We present arguments that only the bound shifts (Δ₁) corresponding to the LS complex should be used for correlation of lanthanide-induced shifts with molecular structure by means of the pseudocontact equation. Several examples are discussed of compounds for which the relative induced shifts are dependent on the concentration of LSR. For such cases it is not possible for both Δ₁ and Δ₂ (the bound shift corresponding to the LS₂ complex) to correlate successfully with the correct structure. Alternative methods of obtaining bound shifts are critically evaluated.     

Scattered-electron rejection in electron transmission spectroscopy

The rejection of scattered electrons in magnetically collimated transmission spectrometers which employ trochoidal monochromators is discussed. Two rejection mechanisms are described. We show that at low impact energies electrons backscattered into the monochromator contribute substantially to the rejection. At higher energies, rejection at the retarding plate following the collision chamber is the dominant mechanism. Under conditions in which the scattered electrons are only partly rejected, artifacts can appear in the measured spectra. We derive a simple model which qualitatively reproduces these features.     

The experimental gas-phase structures of 1,3,5-trisilylbenzene and hexasilylbenzene and the theoretical structures of all benzenes with three or more silyl substituents

The structures of 1,3,5-trisilylbenzene and hexasilylbenzene in the gas phase have been determined by electron diffraction, and that of 1,3,5-trisilylbenzene by X-ray crystallography. The structures of three trisilylbenzene isomers, three tetrasilylbenzenes, pentasilylbenzene and hexasilylbenzene have been computed, ab initio and using Density Functional Theory, at levels up to MP2/6-31G*. The primary effect of silyl substituents is to narrow the ring angle at the substituted carbon atoms. Steric interactions between silyl groups on neighbouring carbon atoms lead first to displacement of these groups away from one another, and then to displacement out of the ring plane, with alternate groups moving to opposite sides of the ring. In the extreme example, hexasilylbenzene, the SiCCSi dihedral angle is 17.8(8) degrees .     

Unidirectional current in a polyacetylene hetero-ionic junction

Unidirectional electronic current is reported for a device based on the interface between an anionically functionalized and a cationically functionalized polyacetylene. The unidirectional current in this mixed ionically/electronically conducting system is electronic but is regulated by asymmetry in the ionic processes.     

Thermodynamics of the spin- 1/2 antiferromagnetic uniform heisenberg chain

We present a new application of the traditional thermodynamic Bethe ansatz to the spin-1/2 antiferromagnetic uniform Heisenberg chain and derive exact nonlinear integral equations for just two functions describing the elementary excitations. By using this approach, the magnetic susceptibility chi and specific heat C versus temperature T are calculated to high accuracy for 5x10(-25)相似文献   

Selective targeting of antibody conjugated multifunctional nanoclusters (nanoroses) to epidermal growth factor receptors in cancer cells

The ability of smaller than 100 nm antibody (Ab) nanoparticle conjugates to target and modulate the biology of specific cell types may enable major advancements in cellular imaging and therapy in cancer. A key challenge is to load a high degree of targeting, imaging, and therapeutic functionality into small, yet stable particles. A versatile method called thin autocatalytic growth on substrate (TAGs) has been developed in our previous study to form ultrathin and asymmetric gold coatings on iron oxide nanocluster cores producing exceptional near-infrared (NIR) absorbance. AlexaFluor 488 labeled Abs were used to correlate the number of Abs conjugated to iron oxide/gold nanoclusters (nanoroses) with the hydrodynamic size. A transition from submonolayer to multilayer aggregates of Abs on the nanorose surface was observed for 54 Abs and an overall particle diameter of ～60-65 nm. The hydrodynamic diameter indicated coverage of a monolayer of 54 Abs, in agreement with the prediction of a geometric model, by assuming a circular footprint of 16.9 nm diameter per Ab molecule. The targeting efficacy of nanoclusters conjugated with monoclonal Abs specific for epidermal growth factor receptor (EGFR) was evaluated in A431 cancer cells using dark field microscopy and atomic absorbance spectrometry (AAS) analysis. Intense NIR scattering was achieved from both high uptake of nanoclusters in cells and high intrinsic NIR absorbance of individual nanoclusters. Dual mode imaging with dark field reflectance microscopy and fluorescence microscopy indicates the Abs remained attached to the Au surfaces upon the uptake by the cancer cells. The ability to load intense multifunctionality, specifically strong NIR absorbance, conjugation of an Ab monolayer in addition to a strong r2 MRI contrast that was previously demonstrated in a total particle size of only 63 nm, is an important step forward in development of theranostic agents for combined molecular specific imaging and therapy.