The asymmetric epoxidation of unfunctionalized prochiral olefins catalyzed by chiral (salen)Mn(III) complexes is an important viable route to obtain chiral epoxides. Recently we proposed a monolayer of (salen)Mn(III) molecules on functionalized flat silica substrates as an active heterogeneous catalyst for enantioselective epoxidation of 6-cyano-2,2-dimethylchromene with huge turnover values. In the present study we synthesized a monolayer of modified (salen)Mn(III) molecules on previously functionalized glass bead substrates in order to increase the active surface area. The catalyst activity of this system was tested with different olefins and in some cases we observed enantioselectivity higher than in solution. The system was reused up to seven times with no variation in performance.
A uranyl complex monolayer that easily allows the optical detection of a nerve gas simulant, namely, dimethyl methylphosphonate, is reported. Both UV/Vis spectroscopy and photoelectron data confirm that the functional hybrid material coordinates a Lewis base by means of the P=O group, which interacts with the uranium equatorial site available for complexation.
Transparent conducting metal oxides
(TCOs) combine the properties
of optical transparency in the visible region with a high electrical
conductivity. They are a critical component as the window electrode
in liquid crystal and electroluminescent display devices, as well
as in many designs of solar cells now under development. Sn-doped
In2O3 is currently the most important TCO, but
it suffers from some drawbacks. These include the high cost of indium,
weak optical absorption in the blue-green region, as well as chemical
instability that leads to corrosion phenomena in organic light-emitting
devices. Indium tin oxide (ITO) films are also brittle and of relatively
low durability. A number of other systems are therefore of interest
as potential alternatives to Sn-doped In2O3.
Recently, CdO has received considerable attention because of its high
intrinsic dopability, which coupled with excellent Hall mobilities
gives a high electrical conductivity. In the present study we have
explored the structure, electronic, and electrical properties of CdO
thin films prepared by a simple metalloorganic chemical vapor deposition
route. The techniques employed include X-ray diffraction, atomic force
microscopy, photoelectron spectroscopy, optical absorption spectroscopy,
and luminescence measurements. Electrical properties were characterized
by four-point probe and Hall effect measurements in the temperature
range between 80 and 460 K. The electrical measurements demonstrated
that the CdO thin films are degenerate semiconductors, with free-electron
concentrations of around 7 × 1020 cm–3 provided by native donors.
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