Influence of preparation conditions on the depth-dependent composition of AuPd nanoparticles grown on planar oxide surfaces

The high resolution depth profiling capabilities of medium energy ion scattering are employed to determine the depth dependent composition of Au/Pd nanoparticles grown on thin silica films on Si(100) as functions of Au/Pd composition, total metal loading and annealing temperature. We show that, despite the fact that Au is deposited prior to Pd, the surface of the particles is generally enriched in Au compared to the bulk composition. The extent of this Au enrichment decreases with annealing temperature. In addition, we examine the influence of the adsorption of acetic acid on the surface composition of Au/Pd particles grown on thin alumina films on NiAl(110). We find that acetic acid causes limited segregation of Pd to the bimetallic surface of relatively Au-rich particles.     

(S)-Lysine adsorption induces the formation of gold nanofingers on Au{111}

STM imaging following the adsorption of (S)-lysine on Au{111} leads to the observation of Au nanofingers whose growth directions correlate with the unit cell vectors of ordered 2-D phases of lysine. The likely mechanism of surface restructuring is discussed.     

Chiral recognition at one-dimensional metal-organic coordination networks initiates the ordering of prochiral catalytic reagent methylacetoacetate on Au{111}

A scanning tunnelling microscopy investigation is reported of the adsorption of methylacetoacetate on Au{111} surfaces templated by the growth of 1-D chains of nickel pyroglutamate. The symmetry of the Au{111}-herringbone reconstruction and the chirality of the pyroglutamate species influence the preferred growth directions of pyroglutamate chains. The interaction of methylacetoacetate with the various chain types reveals details of the symmetry and conformation of the chains. In addition, the docking of methylacetoacetate initiates the growth of ordered domains of methylacetoacetate not observed on either Au{111} or Ni/Au{111} surfaces. The possibilities to utilize such chiral recognition and amplification effects in the design of enantioselective heterogeneous catalysts are discussed.