Microwave synthesis of highly aligned ultra narrow semiconductor rods and wires

We report on the rapid production, characterization, and spectral properties of highly uniform, ultra narrow semiconductor (ZnS, ZnSe, CdS, CdSe) nanorods and nanowires by microwave irradiation. Quantum-confinement effects are manifested in the light absorption and the PL of the rods and wires. The uniformity of the rods and of the wires is demonstrated in their spontaneous assembly into highly ordered 2D supercrystals. We also observed the stepwise growth of the rods originating from nearly spherical nuclei.     

Total Synthesis of Dragocins A−C through Electrochemical Cyclization

The first total synthesis of dragocins A−C, remarkable natural products containing an unusual C4’ oxidized ribose architecture bridged by a polyhydroxylated pyrrolidine, is presented through a route featuring a number of uncommon maneuvers. Several generations towards the target molecules are presented, including the spectacular failure of a key C−H oxidation on a late-stage intermediate. The final route features rapid, stereocontrolled access to a densely functionalized pyrrolidine and an unprecedented diastereoselective oxidative electrochemical cyclization to forge the hallmark 9-membered ring. Preliminary studies suggest this electrochemical oxidation protocol is generally useful.     

Optical and Electrophysical Properties of Thin Zinc Oxide Films Doped with Manganese Oxide and Obtained by Laser Deposition

Journal of Applied Spectroscopy - Nanostructured thin films on a silicon substrate were obtained on a ceramic of zinc oxide doped with manganese oxide by high-frequency periodic pulsed laser action...     

Simultaneous Hydrogen Generation and Exciplex Stimulated Emission in Photobasic Carbon Dots

Photocatalytic water splitting is a promising approach to generating sustainable hydrogen. However, the transport of photoelectrons to the catalyst sites, usually within ps-to-ns timescales, is much faster than proton delivery (∼μs), which limits the activity. Therefore, the acceleration of abstraction of protons from water molecules towards the catalytic sites to keep up with the electron transfer rate can significantly promote hydrogen production. The photobasic effect that is the increase in proton affinity upon excitation offers means to achieve this objective. Herein, we design photobasic carbon dots and identify that internal pyridinic N sites are intrinsically photobasic. This is supported by steady-state and ultrafast spectroscopic measurements that demonstrate proton abstraction within a few picoseconds of excitation. Furthermore, we show that in water, they form a unique four-level lasing scheme with optical gain and stimulated emission. The latter competes with photocatalysis, revealing a rather unique mechanism for efficiency loss, such that the stimulated emission can act as a toggle for photocatalytic activity. This provides additional means of controlling the photocatalytic process and helps the rational design of photocatalytic materials.     

Nickel-Catalyzed Enantioselective Decarboxylative Acylation: Rapid,Modular Access to α-Amino Ketones**

A new approach to the enantiocontrolled synthesis of α-amino ketone derivatives is disclosed by employing a decarboxylative acylation strategy. Thus, when an acyl chloride and an α-amido-containing redox-active ester are exposed to a nickel catalyst, chiral ligand, and metal reductant, α-amido ketones are produced in good yield and high ee. The reaction exhibits broad substrate scope, can be easily scaled up, and is applied to dramatically simplify the synthesis of several known structures.     

Effect of the Terminal Substituents on the Smectic Layer Spacings in 4-(trans-4′-n-Alkyleyelohexyl) Benzoates

The spacings of the smectic layers are compared with the lengths of molecules of p-substituted phenyl 4-(trans-4′-n-decylcyclohexyl) benzoates. It has been found that if the NO₂, CN or CHO groups are substituted in the p-position of the phenyl, then the smectic layers consist of dimers, whereas in the presence of the NCS, COCH₃, I, Cl, Br, F substituents the smectic layers reveal a monomolecular spacing.