Kinetics of solvent supported tubule formation of Lotus () wax on highly oriented pyrolytic graphite (HOPG) investigated by atomic force microscopy.

The time dependence of the formation of lotus wax tubules after recrystallization from various chloroform-based solutions on an HOPG surface at room temperature was studied by atomic force microscopy (magnetic AC mode) taking series of consecutive images of the formation process. The growth of the tubules oriented in an upright fashion follows a sequential rodlet→ring→tubule behavior. The influence of a number of factors, e.

Phthalocyanine adsorption on Au(1 1 0): 1D ordering and adaptive reconstruction.

The adsorption of metal-free phthalocyanine molecules on an anisotropic Au(1 1 0)(1  ×  2) surface has been studied with ultraviolet (UV) photoemission, low-energy electron diffraction and low-temperature scanning tunneling microscopy. In all cases, the molecules form rows in the [1 [Formula: see text] 0] direction, i.e.

Distribution of Pd clusters on ultrathin, epitaxial TiO x films on Pt3Ti(111).

Scanning tunnelling microscopy (STM) was used to investigate the nucleation and growth of palladium clusters on two different, ultrathin, epitaxial, titania films grown on a Pt3Ti(111) surface. The first oxide phase, z'-TiO x , is anisotropic and consists of parallel stripes separated by trenches. Defects (i.

In situ scanning tunneling microscopy study of Ca-modified rutile TiO2(110) in bulk water.

Despite the rising technological interest in the use of calcium-modified TiO2 surfaces in biomedical implants, the Ca/TiO2 interface has not been studied in an aqueous environment. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water. The TiO2 surface was prepared under ultrahigh vacuum (UHV) with repeated sputtering/annealing cycles.

Redox-activity and self-organization of iron-porphyrin monolayers at a copper/electrolyte interface.

The electrochemical behaviour and molecular structure of a layer of water-soluble 5,10,15,20-Tetrakis-(N-methyl-4-pyridyl)-porphyrin-Fe(III) pentatosylate, abbreviated as FeTMPyP, on a chloride modified Cu(100) electrode surface were investigated by means of cyclic voltammetry (CV) and in-situ electrochemical scanning tunneling microscopy. Voltammetric results of HOPG in an electrolyte containing FeTMPyP molecules indicate three distinguishable redox steps involving both the central iron metal and the π-conjugated ring system. However, only the first two reduction steps are observable within the narrow potential window of CVs of Cu(100) measured in the same electrolyte.

Chloride-induced morphology transformations of the Cu(110) surface in dilute HCl.

Morphological changes of a bare Cu(110) substrate in 10 mM HCl aqueous solution have been studied using cyclic voltammetry (CV), electrochemical scanning tunneling microscopy (EC-STM), and reflectance anisotropy spectroscopy (RAS). At cathodic potentials more positive than the hydrogen evolution reaction, a bare copper surface (1 × 1) structure is found by EC-STM. At anodic potentials more negative than the copper(II) dissolution reaction, a furrowed structure is found.

Molecular self-assembly at metal-electrolyte interfaces.

The self-assembly of molecular layers has become an important strategy in modern design of functional materials. However, in particular, large organic molecules may no longer be sufficiently volatile to be deposited by vapor deposition. In this case, deposition from solution may be a promising route; in ionic form, these molecules may even be soluble in water.

Structural and compositional characterization of ultrathin titanium oxide films grown on Pt3Ti(111).

We have investigated the growth of ultrathin titanium oxide (TiO(x)) films on a Pt(3)Ti(111) single crystal surface as a function of oxidation temperature (300-1000 K) and oxygen exposure (up to 4500 l) by means of Auger electron spectroscopy, low-energy electron diffraction, ultraviolet photoelectron spectroscopy and high-resolution electron energy loss spectroscopy (HREELS). Both the surface composition and the surface structure of the resulting TiO(x) films exhibit a strong dependence on the preparation conditions. Loss of the chemical order and Ti segregation are observed at the Pt(3)Ti(111) surface upon oxygen exposures of more than 135 l at 1000 K.

Electrochemical scanning tunneling microscopy.

The electrochemical scanning tunneling microscope was the first tool for the investigation of solid-liquid interfaces that allowed in situ real space imaging of electrode surfaces at the atomic level. Therefore it quickly became an important addition to the repertoire of methods for the determination of the local surface structure as well as the dynamics of reactions and processes taking place at surfaces in an electrolytic environment. In this short overview we present several examples to illustrate the powerful capabilities of the EC-STM, including the observation of clean metal surfaces as well as the adsorption of thin metal layers, specifically adsorbed anions and non-specifically adsorbed organic cations.

Recrystallization of tubules from natural lotus (Nelumbo nucifera) wax on a Au(111) surface.

We present here the first results on the self-assembly of tubules of natural wax from lotus leaves on a single crystal Au(111) surface. A comparison of the tubule growth on Au(111) to that on HOPG is discussed. Although the tubule formation on both Au(111) and HOPG takes place on an intermediate wax film which should mask the substrate properties, the tubule orientations differ.

Molecular structures of dicarboxylated viologens on a Cu(100) surface during an ongoing charge transfer reaction.

Molecular structures of dicarboxylated viologens (1,1'-bis (7-carboxyheptyl)-4,4'-bipyridinium dibromide molecules, V-(C(7)-COOH)(2)) on a Cu(100) surface are studied by means of in situ scanning tunneling microscopy (STM) in combination with cyclic voltammetry (CV). Self-assembled monolayers of adsorbed dicarboxylated viologens form during an ongoing charge transfer reaction. Mainly six structures of the organic molecules are observed, including a dot array, metastable phases, stripe patterns, a closed stacking stripe pattern, chloride desorption, and a dimer phase.

Redox activity and structural transition of heptyl viologen adlayers on Cu(100).

The redox behaviour and potential-dependent adsorption structure of heptyl viologen (1,1'-diheptyl-4,4'-bipyridinium dichloride, DHV(2+)) on a Cu(100) electrode was investigated in a chloride-containing electrolyte solution by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). The dicationic DHV molecules generate a few pairs of current waves in CV measurements which are ascribed to two typical one-electron transfer steps. STM images obtained in a KCl-containing electrolyte solution disclose a well-ordered c(2x2) chloride adlayer on a Cu(100) electrode surface.

Electrochemical reactions at a porphyrin-copper interface.

The structure and reactivity of a Cu(100) single crystal electrode surface covered with free base meso-tetra (N-methyl-4-pyridinium) porphyrin (abbreviated as H(2)TMPyP) as a function of electrode potential have been investigated with cyclic voltammetry (CV), electrochemical scanning tunneling microscopy (ECSTM), and UV-Vis and Raman spectroscopy. The well-ordered self-assembled layer of the porphyrin is consistent with the adsorption of the reduced porphyrin species after the first two-electron reduction step. The copper dissolution reaction in the presence of the stable self-assembled porphyrin layer starts at step edges on both upper and lower terraces and coincides with the preferential oxidation of reduced porphyrin species at step sites.

Surfaces: two-dimensional templates.

Producing nanoscale structures on solid surfaces in a controlled way is a technologicalchallenge that has an important impact on a variety of fields such as microelectronics, magnetic storagetechnology, and heterogeneous catalysis. Currently most processes are based on a top-down approach,which relies on an active patterning of a surface by, for example, lithography or imprinting. As thedesired structures become smaller these top-down processes will reach the physical limit of their resolution.

Copper sulfide nanostripe patterns at the Au(111)/electrolyte interface studied by in situ STM.

One monolayer of Cu was prepared on Au(111) by underpotential deposition from CuSO4/H2SO4 solution and, by two electrolyte exchanges for (i) Cu-free H2SO4 and (ii) NaOH/Na2S solution, exposed to bisulfide. This procedure leads to several incommensurate phases with characteristic stripe patterns. These are irreversibly displaced upon cathodic potential sweeps by different structures, which, after returning to the initial potential, transform into the rectangular CuxS phase already known for the sulfidation of a Cu submonolayer on Au(111).

Disorder or complexity? Understanding a nanoscale template structure on alumina.

One strategy in creating functional nanostructures is templating where active nanoparticles are arranged on a regular nanoscale array of anchor sites on an inert substrate. An extraordinarily well ordered substrate with a 4.2 nm template periodicity is an alumina (aluminum oxide) film grown on a Ni3Al(111) metallic alloy support.

X-ray diffraction and STM study of reactive surfaces under electrochemical control: Cl and I on Cu(100).

The surface structure of Cu(100) modified by chloride and iodide has been studied in an electrochemical environment by means of in-situ scanning tunneling microscopy in combination with in-situ surface X-ray diffraction with a particular focus on adsorbate and potential dependent surface relaxation phenomena. For positive potentials close to the on-set of the copper dissolution reaction, the X-ray data disclose an extraordinarily large Cu-Cl bond length of 2.61 A for the c(2 x 2)-Cl phase.

Surface structure of an ultrathin alumina film on Ni3Al(111): a dynamic scanning force microscopy study.

The surface structure of an ultrathin alumina film on a Ni3Al(111) substrate has been studied by dynamic scanning force microscopy. The alumina film exhibits a hexagonal superstructure with a lattice parameter of 4.14 nm and a (1/sqrt[3] x 1/sqrt[3])R30 degrees substructure.

On the existence of ordered organic adlayers at the Cu(111)/electrolyte interface.

We have reinvestigated the behavior of a Cu(111) electrode in pure and cinchonidine containing aqueous 0.1 M HClO4 solution by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (STM). In contrast to previous publications by Wan et al.

Thin alumina films on Ni3Al(111): a template for nanostructured Pd cluster growth.

The growth of vapor deposited palladium on a well-ordered thin alumina film grown on a Ni3Al(111) surface was studied as a function of the sample temperature during deposition and the palladium flux. The superstructure of the oxide film turns out to be an excellent template for the growth of nanostructured palladium cluster arrays. By taking advantage of the growth steering properties of the alumina film we were able to prepare nearly perfectly ordered hexagonal arrays of palladium clusters with a uniform distance of 4.