Über Oxorhodate der Alkalimetalle: β-LiRhO2

On Oxorhodates of Alkali Metals: β-LiRhO₂ We prepared hitherto unknown β-LiRhO₂ in form of black, cubic single crystals, O⁴–F4₁32, a = 841.27(6) pm, Z = 16. For a first time in case of such metal oxides we find one of the possible variants of order between the NaCl-type with random distribution and the complete ordered types like α-NaFeO₂ as a single crystal (four-circle-diffractometer PW 1100, AgKα, 100 von 109 I₀(hkl), R = 9.10%, R_w = 5.46%). The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, were calculated and discussed.     

Fortschritte in der analytischen Chemie seltener Metalle

Ohne Zusammenfassung     

Nanoparticles as macromolecules

A review of recent trends in the dispersion, purification, and assembly of colloidal nanoparticles highlights a number of growing analogies with ideas borrowed from polymer science. Beyond the similar scales of size, several key concepts lying at the foundation of polymer physics—such as polydispersity, fractionation, phase ordering, and viscoelasticity—are taking on new and unique significance in the contemporary realm of nanotechnology. Leveraging “soft matter” at the nanoscale to simplify materials processing and improve material performance is becoming a reality, with potentially profound implications for a number of emerging technologies. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013 , 51, 1195–1208     

Shear rheology of carbon nanotube suspensions

The shear rheology of carbon nanotube suspensions is reviewed from the perspective of colloid and polymer science. In the semi-dilute to concentrated regimes, the nature of the equilibrium or quiescent state is often dominated by nanotube entanglement and strong attractive inter-particle interactions that favor the formation of a disordered network or gel. The strength of this network with respect to the applied stress dictates the development of mesoscale structural anisotropy, first through a global yield stress and then through a critical stress for homogenization. For concentrated suspensions, the nematic liquid-crystalline order anticipated for high-aspect-ratio rigid rods has been observed in a few select scenarios. The opportunity for deeper theoretical insight is emphasized and intuitive physical arguments are offered that might serve as a foundation for future study.     

Equilibrium structure of hydrogen-bonded polymer blends

Deuterium-labeled polystyrene modified by random distributions of the comonomer p-(1,1,1,3,3,3-hexaflouro-2-hydroxyisopropyl)-α-methyl-styrene [DPS(OH)] has been blended with poly(butyl methacrylate) (PBMA) and studied with small-angle neutron scattering (SANS). Miscibility is induced via hydrogen bonding between the DPS(OH) hydroxyl group and PBMA carbonyl groups. The data suggest that the nature of the miscible-phase structure in these blends differs from that of the usual homopolymer blends at small scattering angles, which we attribute to the short-range site specific nature of the hydrogen bond interaction. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2745–2750, 1998     

Optical anisotropy of nanotube suspensions

A semimacroscopic model of an optically anisotropic nanotube suspension is derived perturbatively from Maxwell's equations in a dielectric medium. We calculate leading-order expressions, valid in the dilute and semidilute limits, for the intrinsic and form contributions to the complex dielectric tensor in terms of the volume fraction, mean orientation, aspect ratio, optical anisotropy, and optical contrast of the nanotubes. The birefringence and dichroism are derived explicitly to leading order in fluctuations, and the connection with depolarized light scattering is established. The results are generalized to include tube deformation.     

Synthesis of 1,2,3‐Triazole Analogues of Lincomycin

In search for new antibiotics we replaced the amide moiety of lincomycin 1 by a 1,2,3‐triazole ring. The 1,2,3‐triazoles 10a – 10k were obtained as single regioisomers by ‘click reaction’ of azide 5 with the alkyne 9k , derived from propyl hygric acid, and the alkyl, aryl, or cycloalkyl alkynes ribosomes 9a – 9j . The new analogues proved inactive towards wild‐type and A2058G mutant.     

Length-dependent optical effects in single-wall carbon nanotubes

Among the novel chemical and physical attributes of single-wall carbon nanotubes (SWCNTs), the optical properties are perhaps the most compelling. Although much is known about how such characteristics depend on nanotube chirality and diameter, relatively little is known about how the optical response depends on length, the next most obvious and fundamental nanotube trait. We show here that the intrinsic optical response of single-wall carbon nanotubes exhibits a strong dependence on nanotube length, and we offer a simple explanation that relates this behavior to the localization of a bound exciton along the length of a nanotube. The results presented here suggest that, for a given volume fraction, the longest nanotubes display significantly enhanced absorption, near-infrared fluorescence, and Raman scattering, which has important practical implications for potential applications that seek to exploit the unique optical characteristics of SWCNTs.