In this report, we demonstrate that self-aggregation is an intrinsic problem of bifunctional organocatalysts, especially in the case when the substrates do not have functional groups which are able to bind strongly with catalyst. Due to their self-association phenomena, the enantioselectivity of bifunctional catalysts dramatically decreases with increasing catalyst concentration or decreasing temperature. Thus, when the substrate concentration is kept constant, the enantioselectivity of bifunctional catalysts dramatically increases with decreasing catalyst loading. The ee values obtained at different catalyst concentrations are fairly consistent with the diffusion coefficients (D) of the catalysts, strongly indicating that their degree of self-association plays a crucial role in determining their enantioselectivity.

The bifunctional Cinchona-based sulfon-A C H T U N G T R E N N U N G amide catalysts showed the highest levels of enantioselectivity reported to date in the alcoholytic desymmetrization of meso-glutaric anhydrides. Density functional theory (DFT) computational studies provide detailed insight into the observed sense of enantioselectivity. Moreover, detailed experimental studies and single crystal X-ray analysis confirmed that these bifunctional organocatalysts 3 do not form Hbonded self-aggregates in both solution and solid state. The synthetic utility of this methodology was also demonstrated in the synthesis of pharmaceutically important g-amino acids, such as (S)-pregabalin. Of the many asymmetric syntheses of enantiomerically pure (S)-pregabalin reported to date, our synthesis requires the least number of and the simplest steps.

Here, we demonstrate the decoration of Ni nanoparticles (NPs) on graphene films by simple annealing for p-type doping of graphene. Scanning electron microscopy and atomic force microscopy revealed that high-density, uniformly sized Ni NPs were formed on the graphene films. The density of the Ni NPs increased gradually, whereas the size of the Ni NPs decreased with increasing NiCl2·6H2O solution concentration. The formation of Ni NPs on graphene films was explained by heat-driven dechlorination and subsequent nano-particlization, as investigated by X-ray photoelectron spectroscopy. The doping effect of Ni NPs onto graphene films was verified by Raman spectroscopy and electrical transport measurements. This method may provide a facile and universal way to obtain metal NPs on graphene if the metal forms a compound with Cl.

The use of graphene-based transparent conductive electrodes critically depends upon the enhancement of electrical conductivity with a negligible loss of optical transmittance of graphene. Hence, the hybridization of graphene and metal nanostructures has been intensively investigated to improve electrical conductivity. Here we demonstrate clusterization of PtCl2 on graphene by a facile method, MeV electron-beam irradiation (MEBI) under ambient conditions, as characterized by scanning electron microscopy, transmittance electron microscopy, and resonant Raman spectroscopy. The workfunction difference between PtCl2 nanoclusters and graphene results in p-type doping of graphene, to achieve a reduced sheet resistance of 69.1 % with respect to that of pristine graphene while maintaining transmittance of 91.7 %. The mechanism of formation of PtCl2 nanoclusters on graphene is likely to be defect-mediated clusterization due to the high energy electron-beam.