378 research outputs found
Growth of Ag icosahedral nanocrystals on a SrTiO3(001) support
No full textWe have investigated the structure and morphology of self-assembled silver nanocrystals supported on a SrTiO3(001)-(2x1) substrate using scanning tunneling microscopy. Ag forms nanocrystals with five-fold symmetry which have an icosahedral shape. Nanocrystals with point, edge, and face orientation (five-fold, two-fold, and three-fold symmetry, respectively) have been studied. The images of these nanocrystals allow a crystallographic identification of the supported shape of the icosahedral form.Citation: Silly, F. & Castell, M. R. (2005). 'Growth of Ag icosahedral nanocrystals on a SrTiO3(001) support', Applied Physics Letters, 87(21), 213107. [Available at http://apl.aip.org/]. © 2005 American Institute of Physics
Two-Dimensional 1,3,5-Tris(4-carboxyphenyl)benzene Self-Assembly at the 1-Phenyloctane/Graphite Interface Revisited
No full textInternational audienceTwo-dimensional (2D) self-assembly of star-shaped 1,3,5-tris(4-carboxyphenyl)benzene molecules is investigated. Scanning tunneling microscopy reveals that this molecule can form three hydrogen-bonded networks at the 1-phenyloctane/graphite interface. One of these structures is close-packed and the two other ones are porous structures, with hexagonal and rectangular cavities. The network with rectangular cavities appears to be the most stable structure
Concentration-Dependent Two-Dimensional Halogen-Bonded Self-Assembly of 1,3,5-Tris(4-iodophenyl)benzene Molecules at the Solid–Liquid Interface
No full textInternational audienceThe concentration-dependent self-assembly of star-shaped 1,3,5-tris(4-iodophenyl)benzene at the 1-phenyl-octane/graphite interface is investigated using scanning tunneling microscopy. The molecules self-assemble into a hexagonal porous halogen-bonded nanoarchitecture at low concentration. This structure is stabilized by X synthons. The molecules are oriented along the same direction in this arrangement. At higher concentration two molecular orientations are observed. The molecules then form a porous parallelogram halogen-bonded structure stabilized by X synthons. The density of molecular packing is thus higher at high solution concentration. High solution concentration also leads to the appearance of domain boundary in the parallelogram structure. Iodine bonds appear to be a promising alternative to hydrogen bonds to engineer tunable organic porous structures on flat surfaces
A robust method for processing scanning probe microscopy images and determining nanoobject position and dimensions
No full textP>Processing of scanning probe microscopy (SPM) images is essential to explore nanoscale phenomena. Image processing and pattern recognition techniques are developed to improve the accuracy and consistency of nanoobject and surface characterization. We present a robust and versatile method to process SPM images and reproducibly estimate nanoobject position and dimensions. This method is using dedicated fits based on the least-square method and the matrix operations. The corresponding algorithms have been implemented in the FabViewer portable application. We illustrate how these algorithms permit not only to correct SPM images but also to precisely determine the position and dimensions of nanocrystals and adatoms on surface. A robustness test is successfully performed using distorted SPM images
Moiré pattern induced by the electronic coupling between 1-octanol self-assembled monolayers and graphite surface
No full textInternational audienceTwo-dimensional self-assembly of 1-octanol molecules on a graphite surface is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM images reveal that this molecule self-assembles into a compact hydrogen-bonded herringbone nanoarchitecture. Molecules are preferentially arranged in a head-to-head and tail-to-tail fashion. A Moir'e pattern appears in the STM images when the 1-octanol layer is covering the graphite surface. The large Moir'e stripes are perpendicular to the 1-octanol lamellae. Interpretation of the STM images suggests that the Moir'e periodicity is governed by the electronic properties of the graphite surface and the 1-octanol layer periodici
Elucidating the intramolecular contrast in the STM images of 2,4,6-tris(4′,4′′,4′′′-trimethylphenyl)-1,3,5-triazine molecules recorded at room-temperature and at the liquid-solid interface
No full textInternational audienc
Two-Dimensional Self-Assembly of 2,4,6-Tris(4,4,4-trimethylphenyl)-1,3,5-triazine Star-Shaped Molecules: Nanoarchitecture Structure and Domain Boundaries
No full textInternational audienceThe self-assembly of the star-shaped 2,4,6-tris(4′,4″,4‴-trimethylphenyl)-1,3,5-triazine molecule is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. This molecule self-assembles into a large-scale close-packed nanoarchitecture stabilized by van der Waals interactions on graphite. High-resolution STM images reveal intramolecular features; i.e., the molecular central ring appears brighter in the high-resolution STM images where nitrogen atoms are located. In addition, STM images show that molecules are mobile at the domain boundary when neighboring domains are aligned. In comparison, the molecular close packing is preserved at the boundary where neighboring domains are shifted
Selecting Two-Dimensional Halogen–Halogen Bonded Self-Assembled 1,3,5-Tris(4-iodophenyl)benzene Porous Nanoarchitectures at the Solid–Liquid Interface
No full textInternational audienceThe self-assembly of the star-shaped 1,3,5-tris(4-iodophenyl)benzene molecule is investigated using scanning tunneling microscopy (STM) at the solid–liquid interface. This molecule forms dimers that self-assemble into two-dimensional porous halogen–halogen bonded nanoarchitectures on the graphite surface. STM shows that the structure of the porous organic network can be tailored using different solvents. Neighboring dimers are binded to each other through two iodine···iodine bonds in 1-phenyloctane, whereas 1-octanol solvent leads to the formation of I4 synthons connecting together four molecular dimers. Iodine bonds appear to be a promising alternative to hydrogen bonds to engineer new organic porous structures on surfaces
Temperature-Triggered Sequential On-Surface Synthesis of One and Two Covalently Bonded Porous Organic Nanoarchitectures on Au(111)
No full textInternational audienceSubtle variations of surface temperature can drastically influence the on-surface synthesis of two-dimensional covalent graphene nanoarchitectures. The structure of the engineered nanoarchitectures not only results from the temperature-activation of the catalytic process, but it is also governed by the temperature-dependent geometry of intermolecular assembly. The sequential engineering of porous organic nanoarchitectures based on the covalent Ullmann coupling of star-shaped 1,3,5-tris(3,5-dibromophenyl)benzene molecules on Au(111) in vacuum is investigated using scanning tunneling microscopy and X-ray photoemission spectroscopy. This molecule can form one-covalent-bond or two-covalent-bonds with neighboring molecules. At room temperature, the molecules self-assemble into a porous halogen-bonded network stabilized by two types of X 3 synthons. One-covalent-bond dimers appear on the surface after annealing at 145 °C. One-covalent-bond chains are created after annealing at 170 °C. Most of the molecules are bonded to two neighbors. One-covalent-bond hexagons as well as two-covalent-bond dimers are appearing on the surface after annealing at 175 °C. Annealing at 275 °C leads to the formation of a porous 2D hexagonal two-covalent-bond nanoarchitecture. STM images show that the number of intermolecular covalent bonds as well as the number of covalently bonded molecular neighbors increases as the temperature rises. Core level spectroscopy shows that the molecules are fully dehalogenated after annealing at 260 °C. These observations show that dibromophenyl-based molecules are promising organic compounds to hierarchically and selectively engineer covalent porous graphene nanoarchitectures having different structures
On-Surface Synthesis of Two-Dimensional Covalent Organic Structures versus Halogen-Bonded Self-Assembly: Competing Formation of Organic Nanoarchitectures
No full textInternational audienceThe competition between the on-surface synthesis of covalent nanoarchitectures and the self-assembly of star-shaped 1,3,5-Tris(4-iodophenyl)benzene molecules on Au(111) in vacuum is investigated using scanning tunneling microscopy above room temperature. The molecules form covalent polygonal nanoachitectures at the gold surface step edges and at the elbows of the gold reconstruction at low coverage. With coverage increasing two-dimensional halogen-bonded structures appear and grow on the surface terraces. Two different halogen-bonded nanoarchitectures are coexisting on the surface and hybrid covalent-halogen bonded structures are locally observed. At high coverage covalent nanoarchitectures are squeezed at the domain boundary of the halogen-bonded structures. The competitive growth between the covalent and halogen-bonded nanoarchitectures leads to formation of a two-layer film above one monolayer deposition. For this coverage, the covalent nanoarchitectures are propelled on top of the halogen-bonded first layer. These observations open up new opportunities for decoupling covalent nanoarchitectures from catalytically active and metal surfaces in vacuum
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