Erich Plies

Time-gated transillumination of biological tissues and tissuelike phantoms

The applicability and limits of time-resolved transillumination to determine the internal details of biological tissues are investigated by phantom experiments. By means of line scans across a sharp edge, the spatial resolution (Δx) and its dependence on the time-gate width (Δt) can be determined. Additionally, measurements of completely absorbing bead pairs embedded in a turbid medium demonstrate the physical resolution in a more realistic case. The benefit of time resolution is especially high for a turbid medium with a comparatively small reduced scattering coefficient of approximately µ(s) = 0.12 mm(-1). Investigations with partially absorbing beads and filled plastic tubes demonstrate the high sensitivity of time-resolving techniques with respect to spatial variations in scattering or absorption coefficients that are due to the embedded disturber. In particular, it is shown that time gating is sensitive to variations in scattering coefficients.

New Inorganic–Organic Hybrid Materials for HPLC Separation Obtained by Direct Synthesis in the Presence of a Surfactant

Nanostructured, mesoporous inorganic–organic hybrid xerogels were reproducibly synthesized by a sol–gel procedure. For the introduction of long alkyl chains into inorganic polymers, trifunctional n-alkyltrialkoxysilanes of the type CH3(CH2)nSi(OR)3 (n = 7, 11, 17; R = CH3, C2H5) were co-condensed with Si(OEt)4 (TEOS). The synthetic pathway involves the employment of n-hexadecylamine as template and catalyst. The xerogels obtained by the present procedure consist of uniform spherical particles with a diameter of about 1 μm. The composition of the new materials was determined by 13C and 29Si cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. In addition, the degree of organization was investigated by small angle X-ray and electron diffraction. In accordance with 13C CP/MAS NMR spectroscopic measurements, the alkyl chains form a crystalline arrangement within the silica polymer. Brunauer–Emmett–Teller (BET) adsorption measurements confirm specific surface areas of up to 1400 m2/g. The material properties prove the xerogels to be suitable as stationary phases in high-performance liquid chromatography (HPLC). These novel mesoporous, nanostructured materials have been successfully employed in HPLC for the first time. Different standard reference materials (SRMs) containing polycyclic aromatic hydrocarbons have been separated with the xerogels described in the present work.

Low-voltage probe forming columns for electrons

Abstract A new low-voltage high-current column with a Schottky emission gun is presented, which generates an electron probe of 1 keV energy, 20 nA probe current and 50 nm in diameter. Additionally, the secondary electron detection is uniform for a large scan field which makes this column very suitable for wafer inspection and fast electron-beam testing of integrated circuits. A “low-voltage booster” is proposed which can be adapted to a conventional medium-voltage scanning electron microscope to improve its resolution for low-voltage operation. These new systems are compared with other existing low-voltage columns and components, and some principles of low-voltage electron optics are discussed.

Synthesis, characterization and HPLC-applications of novel phthalocyanine modified silica gel materials

2(3)-Tetrakisalkenyloxy substituted phthalocyanines 3–6 are synthesized from the corresponding 1,2-dicyano-4-alkenyloxybenzenes 2a–c. These phthalocyanines were hydrosilylated with trimethoxysilane to yield the phthalocyanines 7–10 which were reacted immediately with tetramethoxysilane (TMOS) as co-condensation agent or HPLC silica gel to obtain the new stationary phases 11–16 based on phthalocyanines. The phthalocyanines 3–10 and the corresponding stationary phases 11–16 were characterized by MS, UV/Vis, IR, nEA and NMR spectroscopy. Additionally, the stationary phase 16 was measured by suspended state NMR spectroscopy. With the PcInCl stationary phase 13c, scanning and transmission electron microscopic investigations were performed to obtain information about the morphology of the stationary phases. The modified HPLC silica gels 14–16 were tested successfully for the separation of two different aromatic test mixtures using methanol–water as eluent.

Investigations on the mobility of novel sol–gel processed inorganic–organic hybrid materials

Novel co-condensing agents of the type R′Si(OMe)2(CH2)3R2Si(CH2)3Si(OMe)2R′ {3[Me2Si(C3D0)2] n(3a), Rxa0=xa0Me, R′xa0=xa0Me; 3[Me2Si(C3T0)2] n(3b), Rxa0=xa0Me, R′xa0=xa0OMe; 4[Et2Si(C3D0)2] n(4a), Rxa0=xa0Et, R′xa0=xa0Me; 4[Et2Si(C3T0)2] n(4b), nRxa0=xa0Et, R′xa0=xa0OMe} were synthesised by hydrosilylation of the corresponding diallyldialkylsilanes 1, 2 with dichloro(methyl)silane and trichlorosilane, respectively, followed by treatment with trimethyl orthoformate. These precursors were sol–gel processed with or without PhSi(OMe)3 n[Ph(T0)] to give the xerogels X3a–d, X4a–d. The polysiloxane matrices, the degree of condensation and the integrity of the hydrocarbon backbone were investigated by means of solid state NMR spectroscopy (13C, 29Si). To study the polymer dynamics in the dry state 29Si nCP/MAS NMR measurements of relaxation times (T1ρH) and cross-polarisation parameters (TSiH) were carried out. 1H HR/MAS NMR experiments and T1ρH measurements in different solvents were undertaken to get information on the mobility of the polymers in suspension. Scanning electron microscopy (SEM) images show the morphology of the polymers and energy dispersive X-ray spectroscopy (EDX) suggests that the distribution of the elements agrees with the applied stoichiometry.

Initial resolution measurements of miniaturized electrostatic lenses for LVSEM.

Theoretical and experimental investigations on miniaturized electrostatic lenses for high-resolution low-voltage scanning electron microscopical applications are presented. The electron optical column consists of a Schottky emitter including the extraction anode and a miniaturized three electrode lens consisting of conventional (electron microscopical) platinum apertures. The lens has been optimized with respect to resolution and a value of about 5 nm at a working distance of 1 mm and a beam energy of 1 keV is predicted by simulation. Details on the resolution measurements are presented. An initial experimental value amounts to 31 nm. Specific problems encountered during building and alignment of the lens and measuring the resolution are discussed as well.

Accessibility Studies of Sol-Gel Processed Phosphane-Substituted Iridium(I) Complexes in the Interphase (‡)

The synthesis of the T-silyl functionalized, and therefore sol-gel processable, Vaska complex [IrCl(CO){(C6H5)2PC6H4(CH2)4Si(OMe)3}2] [4(T0)] succeeded by reaction of [Ir(μ-Cl)(COE)2]2 (COE = cyclooctene; 1) with the phosphane (C6H5)2PC6H4(CH2)4Si(OMe)3 [3(T0)] in the presence of carbon monoxide. Subsequently, 4(T0) was co-polycondensed with five equivalents of (MeO)3Si(CH2)3C6H4(CH2)3Si(OMe)3 {5[Ph(1,4-C3T0)2]} to give the polysiloxane-bound complex X1. For accessibility studies of the reactive centers, X1 was reacted in the interphase systems gas/solid and liquid/solid with HCl, Cl2, CH3I (13CH3I), Cl2HCCHCl2, SO2, O2, and NCC≡CCN, in the course of which the xerogels X2−X7 were formed. With the exception of the reversible species X5 (SO2) and X6 (O2) the reactions proceeded quantitatively. The composition of the polymers and the structures of the reactive centers were elucidated by means of multinuclear solid-state NMR (13C, 29Si, 31P), IR, EDX, and EXAFS spectroscopy.

Supported organometallic complexes. Part 27: novel sol–gel processed rhodium(I) complexes: synthesis, characterization, and catalytic reactions in interphases ☆

Abstract A novel T-silyl functionalized cationic (COD)(dppp)rhodium(I) complex was sol–gel processed with various amounts of the co-condensing agents MeSi(OMe) 2 (CH 2 ) 6 (OMe) 2 SiMe and MeSi(OMe) 2 (CH 2 ) 3 (C 6 H 4 )(CH 2 ) 3 (OMe) 2 SiMe to give novel stationary phases for ‘Chemistry in Interphases’. The polysiloxane matrices and the integrity of the rhodium(I) complex centers were investigated by means of multinuclear solid-state NMR ( 13 C, 29 Si, 31 P) and EXAFS spectroscopies. Dynamic NMR measurements show an increasing mobility of the matrix and the reactive centers with a higher amount of the co-condensing component. The accessibility of the anchored rhodium(I) centers was scrutinized by the metal catalyzed hydrogenation of 1-hexene. All applied xerogels show remarkable activities and selectivities. An enhancement of the activities is achieved when polar solvents are used. SEM micrographs reveal the morphology of the hybrid materials and energy dispersive X-ray spectroscopy (EDX) suggests that the distribution of the elements is in satisfying agreement with the applied composition.

Electrochemistry of transition metal complex catalysts. Part 8. One-electron oxidation of an iridium complex with a cyclohexane-derived tripod phosphine ligand - cyclic voltammetry and preparative electrolysis

Abstract The electrochemical oxidation of Ir(tdppcyme)(CO)Cl, tdppcyme= cis , cis -1,3,5-tris(di-phenylphosphine)- cis , cis -1,3,5-tris(methoxycarbonyl)cyclohexane, is investigated in dichloromethane–0.1 M tetrabutylammonium hexafluorophosphate at Pt electrodes with cyclic voltammetry, chronoamperometry and chronocoulometry, as well as preparative electrolysis. While the primary one-electron oxidation to Ir +II appears quasi-reversible in the electroanalytical experiments, the longer time scale of electrolysis allows the formation of an insoluble product by a follow-up reaction. By means of spectroscopic techniques as well as EXAFS and EDX experiments the structure of a dimeric di-μ-chloro di-iridium complex is deduced.

Unit cell determination of 2,3,9,10,16,17,23,24- octapentoxyphthalocyanine and its nickel derivative using electron and X-ray powder diffraction

2,3,9,10,16,17,23,24-Octapentoxyphthalocyanine and its nickel derivative have been studied by means of electron and X-ray powder diffraction. The results reveal that the metal-free compound forms monoclinic crystals (space group C2/c) with unit cell constants a = 4.202 nm, b = 0.4977 nm, c = 3.345 nm, β = 98.9 ° and Z = 4 molecules per unit cell. 2,3,9,10,16,17,23,24-Octapentoxyphthalocyaninatonickel(II) is likely to be isomorphous to its metal-free analogue, but occurs in a second phase which is also stable at room temperature. This is identified to be a crystalline primitive hexagonal phase with cell constants a = b = 2.50 nm and c = 0.33 nm. It is assumed that the molecules form a columnar structure along the c-axis, whereas the hexagonal cross-section in the ab-plane goes back to the molecular disc shape. Imaging of monoclinic crystals of 2,3,9,10,16,17,23,24-octapentoxyphthalocyanine in an energy-filtering transmission electron microscope (EFTEM) can be performed to resolve 2 nm structures only, owin...