Ultrahigh vacuum and air observations of Pd clusters grown on clean graphite

Abstract

Comparison between UHV and air observations on Pd clusters deposited under UHV on a clean graphite surface is made. For the largest clusters (>10 nm), no dramatic influence of air exposure is observed. Quite surprisingly, we have been able to image in air the surface atomic arrangement of 1.5 nm Pd clusters. They have a tetrahedron shape with (111) facets and are epitaxially oriented: Pd (111)//graphite (00.1), Pd[112̄]//graphite [01.0].

High dispersion and electrocatalytic properties of palladium nanoparticles on single-walled carbon nanotubes

“…Palladium nanoparticles can be prepared by various deposition methods including chemical reduction of Pd complexes [2], ion exchange [3], vapor deposition [4][5][6], thermal evaporation in vacuum [7,8], and electrochemical deposition [9][10][11][12]. It is well known that the basic properties of impregnated catalysts are strongly affected by the impregnation method, the microstructure, the surface reactivity, and the metal precursor [13,14].…”

Lattice Fringe Signatures of Epitaxy on Nanotubes

“…According to diffraction data in the literature [9], epitaxy of FCC Pd on single crystal graphite (0002) planes typically takes place with (111) P d parallel to (0002) graphite in the growth direction, and [112] P d parallel to [01.0] graphene in the plane of the substrate. This fully specifies the expected fringe distributions.…”

Scanning tunneling microscopy study of a DNA fragment of known size and sequence

“…It is mounted inside a UHV chamber with base pressure of about 10 -10 torr, but the DNA molecules were imaged in a vacuum of 10-7 torr, as in electron microscopy (EM) studies. Atomic resolution is routinely achieved wfth this microscope on flat single crystal surfaces or three-dimensional (3D) clusters [19]. It allows the use of very small tunneling currents « 1 pA).…”

“…The scanning tunneling microscope used for these studies was designed by our group and previously used to image small metallic clusters deposited under ultra-high vacuum (UHV) on graphite surfaces [17][18][19]. It is mounted inside a UHV chamber with base pressure of about 10 -10 torr, but the DNA molecules were imaged in a vacuum of 10-7 torr, as in electron microscopy (EM) studies.…”

“…The [9], STM highresolution imaging is clearly a promising way to study DNA structures involved in gene activity [28]. It is now clear that sequence-dependent DNA curvature governs the accessibility of bases to DNA-binding proteins by determining their outwards or inwards orientation [19]. A main contribution of STM to nucleic acids research may be to allow the study of the intimate structure of binding sites within their general DNA structural environment.…”