Interface structure and composition of MoO/GaAs(0 0 1).

We studied growth, structure, stress, oxidation state as well as surface and interface structure and composition of thermally-evaporated thin MoO films on the technologically important III/V-semiconductor substrate GaAs(0 0 1). The MoO films grow with Mo in the 6+  oxidation state. The electrical resistance is tunable by the oxygen partial pressure during deposition from transparent insulating to semi-transparant halfmetallic.

Radio frequency surface plasma oscillations: electrical excitation and detection by Ar/Ag(111).

We electrically excite surface plasma oscillations on a Ag(111) single crystal by alternating electric charging at radio frequency. The radio frequency signal energy of 2.2 μeV, used to induce surface plasma oscillations, is about 5 to 6 orders of magnitude lower than the plasmon energies reachable by optical excitation or electron impact.

On-Surface Site-Selective Cyclization of Corrole Radicals.

Radical cyclization is among the most powerful and versatile reactions for constructing mono- and polycyclic systems, but has, to date, remained unexplored in the context of on-surface synthesis. We report the controlled on-surface synthesis of stable corrole radicals on Ag(111) via site-specific dehydrogenation of a pyrrole N-H bond in the 5,10,15-tris(pentafluoro-phenyl)-corrole triggered by annealing at 330 K under ultrahigh-vacuum conditions. We reveal a thermally induced regioselective cyclization reaction mediated by a radical cascade and resolve the reaction mechanism of the pertaining cyclodefluorination reaction at the single-molecule level.

A Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions in Water.

Oxygen reduction and water oxidation are two key processes in fuel cell applications. The oxidation of water to dioxygen is a 4 H/4 e process, while oxygen can be fully reduced to water by a 4 e/4 H process or partially reduced by fewer electrons to reactive oxygen species such as HO and O. We demonstrate that a novel manganese corrole complex behaves as a bifunctional catalyst for both the electrocatalytic generation of dioxygen as well as the reduction of dioxygen in aqueous media.

Bilayer of Terbium Double-Decker Single-Molecule Magnets.

We report a low-temperature scanning tunneling microscopy and spectroscopy study of the structural and electronic properties of a bilayer of terbium double-decker (bis(phthalocyaninato)terbium(III), TbPc) molecules on Au(111) at 5 K. The TbPc molecules are found to adsorb flat on top of a first compact TbPc monolayer on Au(111), forming a square-like packing similar to the underlying first layer. Their frontier-orbital electronic structure, measured by tunneling conductance spectroscopy, clearly differs from that of the underlying first monolayer.

A Bifunctional Electrocatalyst for Oxygen Evolution and Oxygen Reduction Reactions in Water.

Oxygen reduction and water oxidation are two key processes in fuel cell applications. The oxidation of water to dioxygen is a 4 H(+)/4 e(-) process, while oxygen can be fully reduced to water by a 4 e(-)/4 H(+) process or partially reduced by fewer electrons to reactive oxygen species such as H2O2 and O2(-). We demonstrate that a novel manganese corrole complex behaves as a bifunctional catalyst for both the electrocatalytic generation of dioxygen as well as the reduction of dioxygen in aqueous media.

Manipulation resolves non-trivial structure of corrole monolayer on Ag(111).

Non-trivial arrangement of molecules within a molecular network complicates structure determination due to interdigitation, partial overlap, or stacking. We demonstrate that combined imaging and lateral manipulation with a scanning tunneling microscope resolves the intricate structure of a molecular network in two-dimensions in a straightforward manner. The network, formed by a monolayer of 5,10,15-tris(pentafluorophenyl)-corrole molecules on Ag(111), is manipulated for the first time with single-molecule precision.

Ultrathin MgO diffusion barriers for ferromagnetic electrodes on GaAs(001).

Ultrathin MgO(100) films serving as a diffusion barrier between ferromagnetic electrodes and GaAs(001) semiconductor templates have been investigated. Using Fe as an exemplary ferromagnetic material, heterostructures of Fe/MgO/GaAs(001) were prepared at 200 °C with the MgO thickness ranging from 1.5 to 3 nm.

Radio frequency scanning tunneling spectroscopy for single-molecule spin resonance.

We probe nuclear and electron spins in a single molecule even beyond the electromagnetic dipole selection rules, at readily accessible magnetic fields (few mT) and temperatures (5 K) by resonant radio-frequency current from a scanning tunneling microscope. We achieve subnanometer spatial resolution combined with single-spin sensitivity, representing a 10 orders of magnitude improvement compared to existing magnetic resonance techniques. We demonstrate the successful resonant spectroscopy of the complete manifold of nuclear and electronic magnetic transitions of up to ΔI(z)=±3 and ΔJ(z)=±12 of single quantum spins in a single molecule.

Radio-wave oscillations of molecular-chain resonators.

We report a new type of nanomechanical resonator system based on one-dimensional chains of only 4 to 7 weakly coupled small molecules. Experimental characterization of the truly nanoscopic resonators is achieved by means of a novel radio-frequency scanning tunneling microscopy detection technique at cryogenic temperatures. Above 20 K we observe concerted oscillations of the individual molecules in chains, reminiscent of the first and second eigenmodes of a one-dimensional harmonic resonator.

Radio-frequency excitation of single molecules by scanning tunnelling microscopy.

We have upgraded a low-temperature scanning tunnelling microscope (STM) with a radio-frequency (RF) modulation system to extend STM spectroscopy to the range of low energy excitations (<1 meV). We studied single molecules of a stable hydrocarbon π-radical weakly physisorbed on Au(111). At 5 K thermal excitation of the adsorbed molecules is inhibited due to the lack of short-wavelength phonons of the substrate.

Surface-Supported Hydrocarbon π Radicals Show Kondo Behavior.

Stable hydrocarbon radicals are utilized as spin standards and prototype metal-free molecular magnets able to withstand ambient conditions. Our study presents experimental results obtained with submolecular resolution by scanning tunneling microscopy and spectroscopy from monomers and dimers of stable hydrocarbon π radicals adsorbed on the Au(111) surface at 7-50 K. We provide conclusive evidence of the preservation of the radical spin-1/2 state, aiming to establish α,γ-bisdiphenylene-β-phenylallyl (BDPA) on Au(111) as a novel Kondo system, where the impurity spin is localized in a metal-free π molecular orbital of a neutral radical state in gas phase preserved on a metal support.

Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support.

Stable hydrocarbon radicals are able to withstand ambient conditions. Their combination with a supporting surface is a promising route toward novel functionalities or carbon-based magnetic systems. This will remain elusive until the interplay of radical-radical interactions and interface effects is fundamentally explored.

A population pharmacokinetic/pharmacodynamic model of thrombocytopenia characterizing the effect of trastuzumab emtansine (T-DM1) on platelet counts in patients with HER2-positive metastatic breast cancer.

Purpose: Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate in the development for the treatment of human epidermal growth factor receptor 2-positive cancers. Thrombocytopenia (TCP) is the dose-limiting toxicity of T-DM1. A semimechanistic population pharmacokinetic/pharmacodynamic (PK/PD) model was developed to characterize the effect of T-DM1 on patient platelet counts.

Nanopatterning of Si(001) for bottom-up fabrication of nanostructures.

The epitaxial growth of Si on Si(001) under conditions at which the (2 × n) superstructure is forming has been investigated by scanning tunneling microscopy and Monte Carlo simulations. Our experiments reveal a periodic change of the surface morphology with the surface coverage of Si. A regular (2 × n) stripe pattern is observed at coverages of 0.

Spectroscopic scanning tunneling microscopy studies of single surface-supported free-base corroles.

Corroles are versatile chemically active agents in solution. Expanding their applications toward surface-supported systems requires a fundamental knowledge of corrole-surface interactions. We employed the tip of a low-temperature scanning tunneling microscope as local probe to investigate at the single-molecule level the electronic and geometric properties of surface-supported free-base corrole molecules.

Preserving charge and oxidation state of Au(III) ions in an agent-functionalized nanocrystal model system.

Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of the active center is indispensable. We present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support with potential impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery.

Spectroscopic STM studies of single gold(III) porphyrin molecules.

Low-temperature scanning tunneling microscopy, a well-established technique for single-molecule investigations in an ultrahigh vacuum environment, has been used to study the electronic properties of Au(III) 5,10,15,20-tetraphenylporphyrin (AuTPP) molecules on Au(111) at the submolecular scale. AuTPP serves as a model system for chemotherapeutically relevant Au(III) porphyrins. For the first time, real-space images and local scanning tunneling spectroscopy data of the frontier molecular orbitals of AuTPP are presented.

Expression profiling of mammalian male meiosis and gametogenesis identifies novel candidate genes for roles in the regulation of fertility.

We report a comprehensive large-scale expression profiling analysis of mammalian male germ cells undergoing mitotic growth, meiosis, and gametogenesis by using high-density oligonucleotide microarrays and highly enriched cell populations. Among 11,955 rat loci investigated, 1268 were identified as differentially transcribed in germ cells at subsequent developmental stages compared with total testis, somatic Sertoli cells as well as brain and skeletal muscle controls. The loci were organized into four expression clusters that correspond to somatic, mitotic, meiotic, and postmeiotic cell types.

Acoustoelastic effect in stressed heterostructures.

Mechanical stresses influence the phase velocity of acoustic waves, known as the AE (acoustoelastic) effect. In order to calculate the AE effect of biaxially stressed layered systems, we extended the transfer matrix method for acoustic wave propagation by considering the change of the density, the influence of residual stress, and the modification of the elastic stiffness tensor by residual strain and by third-order constants. The generalized method is applied to the calculation of the angular dispersion of the AE effect for transverse bulk modes and surface acoustic waves on Ge(001).