The Growth of Silver on an Ordered Alumina Surface

Synthesis of Highly Active Sub-Nanometer Pt@Rh Core-Shell Nanocatalyst via a Photochemical Route: Porous Titania Nanoplates as a Superior Photoactive Support

Sub-nanometer Pt@Rh nanoparticles highly dispersed on MIL-125-derived porous TiO₂ nanoplates are successfully prepared for the first time by a photochemical route, where the porous TiO₂ nanoplates with a relatively high specific surface area play a dual role as both effective photoreductant and catalyst support. The resulting Pt@Rh/p-TiO₂ can be utilized as a highly active catalyst.

Effect of polar surface on the growth of Au

The Au particles are more thermally stable on faceted MgO(111) than on MgO(100).

Enhanced reactivity and related optical changes of Ag nanoparticles on amorphous Al₂O₃ supports

Pairs of samples containing Ag nanoparticles (NPs) of different dimensions have been produced under the same conditions but on different substrates, namely standard glass slides and a thin layer of amorphous aluminum oxide (a-Al₂O₃) on-glass. Upon storage in ambient conditions (air and room temperature) the color of samples changed and a blue-shift and damping of the surface plasmon resonance was observed. The changes are weaker for the samples on-glass and tend to saturate after 12 months. In contrast, the changes for the samples on a-Al₂O₃ appear to be still progressing after 25 months. While x-ray photoelectron spectroscopy shows a slight sulfurization and negligible oxidation of the Ag for the on-glass samples upon 25 months aging, it shows that Ag is strongly oxidized for the on a-Al₂O₃ samples and sulfurization is negligible. Both optical and chemical results are consistent with the production of a shell at the expense of a reduction of the metal core dimensions, the latter being responsible for the blue-shift and related to the small (<10 nm initial diameter) of the NPs. The enhanced reactivity of the Ag NPs on the a-Al₂O₃ supports goes along with specific morphological changes of the Ag NPs and the observation of nitrogen.

Synthesis of modified carbon nanotube-supported Pd and the catalytic performance for hydrodehalogenation of aryl halides

The effects of surface functionalization on the deposition of Pd nanoparticles on multi-walled carbon nanotubes (CNTs) have been studied. Two methods were used for the functionalization of CNTs: one employed a 1:1 (v/v) mixture of concentrated H2SO4/HNO3, sonicated at RT; the other employed a 3:1 (v/v) mixture of concentrated H2SO4/HNO3, sonicated at 60 °C. A large number of surface oxide groups were introduced on the surface of functionalized CNTs, especially in strong oxidation power (H2SO4/HNO3 = 3:1, 60 °C). The dispersion of Pd nanoparticles on CNTs was found to depend on the amount of surface oxide groups, with larger amounts of surface oxide groups resulting in higher dispersion of Pd nanoparticles. The effects of CNT surface functionalization on the performance of Pd/CNTs catalysts were studied, and the reaction conditions optimized, using the hydrodebromination of bromobenzene as model reaction. Under optimal conditions, the hydrodehalogenation of various aryl halides were tested over Pd/CNTs catalysts.

Bond order resolved 3d5/2 and valence band chemical shifts of ag surfaces and nanoclusters

Incorporating the tight-binding theory and the bond order-length-strength (BOLS) correlation into the X-ray photoelectron spectra of Ag(111) and (100) surfaces and the Auger electron spectra of Ag nanoparticles deposited on Al2O3 and CeO2 substrates has led to quantitative information of the 3d5/2 and the valence binding energies of an isolated Ag atom and their shifts upon bulk, defect, surface, and nanocrystal formation. It is clarified that the globally positive energy shifts originate from the undercoordination-induced Goldschmidt-Pauling bond contraction and the associated local quantum entrapment and the heterocoordination-induced bond nature alteration at the particle-substrate interfaces. Perturbation to the Hamiltonian by atomic ill-coordination dictates the energy shift that is proportional to the bond energy at equilibrium. Theoretical reproduction of the measured spectroscopic data derived that the 3d5/2 energy of an isolated Ag atom shifts from 363.02 to 367.65 eV and the valence band center from 0.36 to 8.32 eV upon bulk formation. The extended Wagner plots revealed the coefficients of valence recharging and potential screening to be 1.21 and 1.56 for Ag interacting with Al2O3 substrate and 1.15 and 1.50 for Ag with CeO2, respectively. Exercises exemplify the enhanced capabilities of XPS and AES in determining quantitative information regarding the evolution of the local bond length, bond energy, binding energy density, and atomic cohesive energy, with the coordination and chemical environment.

Initial oxidation and interfacial diffusion of Zn on faceted MgO(111) films

The interaction of zinc and faceted MgO(111) thin films prepared on a Mo(110) substrate was investigated in situ by using various surface analysis techniques, including X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and low-energy electron diffraction. The results revealed that three-dimensional Zn islands exist on the faceted MgO(111) films and that no chemical interaction takes place at the interface at room temperature. Initially, deposited Zn is stable at temperatures below 400 K and diffuses into MgO at temperatures above 425 K. A portion of Zn is oxidized at approximately 10 (-6) mbar O 2 at room temperature. An interfacial phase of Zn x Mg 1- x O was formed after Zn was exposed to approximately 10 (-6) mbar O 2 at temperatures >or=500 K. The faceted structure on the MgO(111) surface is of a disadvantage for the epitaxial growth of ZnO films.