On cluster kinetics and MBE growth

Based on the model of a so-called Near Surface Transition Layer (NSTL) proposed by HERMAN and ANDERSSON we discuss the possible role of clusters during MBE growth. Moreover, intentional use of small clusters instead of single atoms as beam constituents may contribute to improvements in crystal quality even at low substrate temperature and high growth rate.     

Unique emission from polymer based lanthanide alloys

The incorporation of metal-ligand interactions into macromolecules imparts them with unique and potentially useful properties. We report novel macromolecules prepared via ATRP that contain activated esters for subsequent incorporation of terpyridine. The addition of lanthanide ions (Eu3+ and Tb3+) gave metal functionalized polymers that exhibited excellent emission of either pink (Eu3+) or green (Tb3+) light. A unique yellow luminescence was generated when these two different metal ions were incorporated into the same molecular backbone at a 1:1 ratio, producing an alloy. Upon heating above 50 degrees C, selective thermochromism, from yellow to orange/pink, was observed.     

Tuning the hemolytic and antibacterial activities of amphiphilic polynorbornene derivatives

Amphiphilic cationic polynorbornene derivatives, soluble in water, were prepared from modular norbornene monomers, with a wide range of molecular weights (M(n) = 1600-137 500 g/mol) and narrow polydispersities (PDI = 1.1-1.3). The antibacterial activity determined by growth inhibition assays and the hemolytic activity against human red blood cells were measured and compared to determine the selectivity of the polymers for bacterial over mammalian cells. The effects of monomer repeat unit hydrophobicity and polymer molecular weight on antibacterial and hemolytic activities were determined. The hydrophobicity of the repeat unit was observed to have dramatic effects on antibacterial and hemolytic activities. Lipid membrane disruption activities of the polymers was confirmed by measuring polymer-induced dye leakage from large unilamellar vesicles. By tuning the overall hydrophobicity of the polymer through random copolymerizations of modular norbornene derivatives, highly selective, nonhemolytic antibacterial activities were obtained. For appropriate monomer composition, selectivity against bacteria versus human red blood cells was determined to be over 100.     

New correlation factors for explicitly correlated electronic wave functions

We have investigated the correlation factors exp(-zetar12), r12 exp(-zetar12), erfc(zetar12), and r12 erfc(zetar12) in place of the linear-r12 term for use in explicitly correlated electronic-structure methods. The accuracy obtained with all of these correlation factors is significantly greater than that obtained with the plain correlation factor r12. Polarization functions that are more diffuse than those of standard basis sets give even better results. The correlation factor exp(-zetar12) is very close to the optimum correlation factor for helium and outperforms the others.     

Synthesis of alkoxy-substituted ortho-phenylene ethynylene oligomers

[structure: see text] This Letter describes the first published synthesis and characterization of alkoxy-substituted ortho-phenylene ethynylene (o-PE) oligomers. Sonogashira coupling was used to assemble discrete chain lengths, using a key monomer with orthogonal groups. Deprotection or activation allowed stepwise coupling to produce the dimer, trimer, and tetramer, while convergent coupling of appropriately substituted trimers produced the hexamer. The placement of alkoxy side chains renders these oligomers soluble in common organic solvents permitting solution characterization. Absorption and emission spectra of the trimer, tetramer, and hexamer are provided.