Engineering electrophilic atomic Ir sites on CeO_(2) colloidal spheres for selectivity control in hydrogenation of α,β-unsaturated carbonyl compounds

Selective hydrogenation of the carbonyl bond inα,β-unsaturated carbonyl compounds is rather challenging owing to the more feasible hydrogenation of ethylenic bond from both thermodynamic and kinetic aspects.Here,we demonstrate a facile emulsionbased molecule-nanoparticle self-assembly strategy for the atomic engineering of Ir species on three-dimensional CeO_(2)spheres(Ir1@CeO_(2)).When applied to the hydrogenation ofα,β-unsaturated aldehydes,Ir1@CeO_(2)catalyst remarkably exhibited~100%selectivity towards unsaturated alcohols,whereas the formation of Ir nanoparticles on CeO_(2)drastically decreased the selectivity for unsaturated alcohols.Spectroscopic studies revealed that strong metal-support interactions triggered the charge transfer from Ir to CeO_(2),leading to the partial reduction of Ce^(4+)to Ce^(3+)along with the formation new Ir^(δ+)-O_(2)--Ce^(3+)(OV)interfaces.The electrophilic atomic Ir species at the Ir^(δ+)-O_(2)--Ce^(3+)(OV)interfaces would therefore preferentially adsorb and facilitate hydrogenation of polar C=O bond to achieve exceptional selectivity.

A Mechanically Tunable Plasmonic Structure Composed of a Monolayer Array of Metal-Capped Colloidal Spheres on an Elastomeric Substrate

A highly stretchable plasmonic structure composed of a monolayer array of metal-capped colloidal spheres on an elastomeric substrate has been fabricated using simple and inexpensive self-assembly and transfer-printing techniques.This composite structure supports coupled surface plasmons whose wavelengths are sensitive to the arrangement of the metal-capped colloidal spheres.Upon stretching,the lattice of metal-capped colloidal spheres will be deformed,leading to a large wavelength shift of surface plasmon resonances and simultaneously an obvious color change.This stretchable plasmonic structure offers a promising approach to tune surface plasmon resonances and might be exploited in realizing flexible plasmonic devices with tunability of mechanical strain.

A SURFACTANT-ASSISTED APPROACH FOR PREPARING COLLOIDAL AZO POLYMER SPHERES WITH NARROW SIZE DISTRIBUTION

A surfactant-assisted method for preparing colloidal spheres with narrow size distribution from a polydispersed azo polymer has been developed in this work. The colloidal spheres were formed through gradual hydrophobic aggregation of the polymeric chains in THF-H2O dispersion media, which was induced by a steady increase in the water content. Results showed that the addition of a small amount of surfactant （SDBS） could significantly narrow the size distribution of the colloidal spheres. The size distribution of the colloidal spheres was determined by the concentrations of azo polymer and the amount of surfactant in the systems. When the concentrations of polymer and surfactant amount were in a proper range, colloidal spheres with narrow size distribution could be obtained. The colloidal spheres formed by this method could be elongated along the polarization direction of the laser beams to be a new type of the colloid-based functional materials. upon Ar^＋ laser irradiation. The colloidal spheres are considered

Transport coefficients and mechanical response in hard-disk colloidal suspensions

We investigate the transport properties and mechanical response of glassy hard disks using nonlinear Langevin equation theory.We derive expressions for the elastic shear modulus and viscosity in two dimensions on the basis of thermalactivated barrier-hopping dynamics and mechanically accelerated motion.Dense hard disks exhibit phenomena such as softening elasticity,shear-thinning of viscosity,and yielding upon deformation,which are qualitatively similar to dense hard-sphere colloidal suspensions in three dimensions.These phenomena can be ascribed to stress-induced ＂landscape tilting＂.Quantitative comparisons of these phenomena between hard disks and hard spheres are presented.Interestingly,we find that the density dependence of yield stress in hard disks is much more significant than in hard spheres.Our work provides a foundation for further generalizing the nonlinear Langevin equation theory to address slow dynamics and rheological behavior in binary or polydisperse mixtures of hard or soft disks.

Recent Progress in Exploiting Small Molecule Peptides as Supramolecular Hydrogelators

Small molecule peptides and their derivatives are an emerging class of supramolecular hydrogelators that have attracted rapidly growing interest in the fields of drug delivery and regenerative medicine due to their inherent biodegradability and biocompatibility, as well as versatility in molecular design and ease of synthesis. Built upon the directional, intermolecular interactions such as hydrogen bonding and π-π stacking, peptide-based molecular units can associate in aqueous solution into filamentous assemblies of various sizes and shapes. Under appropriate conditions, these filamentous assemblies can percolate into a 3D network with materials properties tailorable for specific biomedical applications. In this review, we survey the literature published over the past three years in the development of peptide-based hydrogelators for biomedical applications. We highlight several representative examples and center our discussion on the fundamentals of molecular design, assembly, and gelation conditions.