Alloying effect on grain-size dependent deformation twinning in nanocrystalline Cu–Zn alloys

Grain-size dependency of deformation twinning has been previously reported in nanocrystalline face-centred-cubic metals, which results in an optimum grain-size range for twin formation. Here, we report, for the first time in experiments, the observed optimum grain sizes for deformation twins in nanocrystalline Cu–Zn alloys which slightly increase with increasing Zn content. This result agrees with the reported trend but is much weaker than predicted by stacking-fault-energy based models. Our results indicate that alloying changes the relationship between the stacking-fault and twin-fault energy and therefore affects the optimum grain size for deformation twinning. These observations should be also applicable to other alloy systems.     

Electrosensing Platform for Varenicline Based on Reduced Graphene Oxide

Graphene oxide (GO) was synthesized and reduced by chemical, hydrothermal and electrochemical methods. The GO and reduced GO was characterized by XRD, FTIR, absorption, Raman, FESEM and AFM methods. Chemically reduced GO (CrGO) was observed to efficiently enhance the electron transfer kinetics of varenicline compared to hydrothermally and electrochemically reduced GO. Hence, CrGO was used for the fabrication of an electrochemical sensor for the determination of varenicline in the concentration range of 0.03–50 µM with a limit of detection of 7.03 nM. The applicability of the proposed sensor was demonstrated by analyzing the biological samples containing varenicline.     

Photocatalytic Au–Bi2S3 Heteronanostructures

Au–Bi₂S₃ heteronanostructure photocatalysts were designed in which the coupling of a metal plasmon and a semiconductor exciton aids the absorption of solar light, enhances charge separation, and results in improved catalytic activity. Furthermore, these nanostructures show a unique pattern of structural combination, with Au nanoparticles positioned at the center of Bi₂S₃ nanorods. The chemistry of formation of these nanostructures, their epitaxy at the junction, and their photoconductance were studied, as well as their photoresponse properties.     

Chemistry of the 2,3-oxaphosphabicyclo[2.2.2]octene ring system: Extrusion of metaphosphates

The 2,3-oxaphosphabicyclo[2.2.2]octene 3-oxide (or sulfide) ring system is of considerable value because it easily fragments on being heated or irradiated (254 nm) to provide three-coordinate phosphoryl species. The system is synthesized by O-insertion with peracids into a C P bond of 7-phosphanorbornene derivatives with a variety of P-substituents. With rare exception, the insertion has been found to proceed with retention of the configuration at phosphorus, as established by X-ray and NMR techniques. The thermal fragmentation that produces the metaphosphate derivatives EtO PO₂, EtO P(S)O, and Et₂N PO₂ follows first-order kinetics, and is independent of the concentration of a trapping agent for these species. Solvent effects and activation parameters join in defining a retrocycloaddition mechanism that ejects the free metaphosphate. The species Ph PO₂ can also be easily generated either thermally or photochemically. Metaphosphates have been found to attack ethereal oxygen in epoxides and oxetanes, and may undergo anchimeric participation with a properly placed methoxy group on the substituent used in the 2,3-oxaphosphabicyclo[2.2.2]octene precursor.     

Synthesis and characterization of new O,O‐diethyl phosphorothioates derived from substituted tetrazolo[1,5‐a]quinolin‐ 4‐ylmethanol derivatives

A simple and convenient method is developed for the synthesis of new O,O‐diethyl O‐(substituted tetrazolo[1,5‐a]quinolin‐4‐yl)methyl phosphorothioates, which has been synthesized for the first time from tetrazolo[1,5‐a] quinolines via tetrazolo[1,5‐a]quinolin‐4‐ylmethanol derivatives. The structures of the all newly synthesized compounds were elucidated by analytical and spectral methods. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:436–441, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20570