Imaging the adsorption sites of organic molecules on metallic surfaces by an adaptive tunnelling current feedback.

Atomic force microscopy (AFM) allows submolecular resolution imaging of organic molecules deposited on a surface by using CO-functionalized qPlus sensors under ultrahigh vacuum and low temperature conditions. However, the experimental determination of the adsorption sites of these organic molecules requires the precise identification of the atomic structure of the surface on which they are adsorbed. Here, we develop an automation method for AFM imaging that provides in a single image both, submolecular resolution on organic molecules and atomic resolution on the surrounding metallic surface.

Highly Sensitive and Fast Responding Flexible Force Sensors Using ZnO/ZnMgO Coaxial Nanotubes on Graphene Layers for Breath Sensing.

The authors report the fabrication of highly sensitive, rapidly responding flexible force sensors using ZnO/ZnMgO coaxial nanotubes grown on graphene layers and their applications in sleep apnea monitoring. Flexible force sensors are fabricated by forming Schottky contacts to the nanotube array, followed by the mechanical release of the entire structure from the host substrate. The electrical characteristics of ZnO and ZnO/ZnMgO nanotube-based sensors are thoroughly investigated and compared.

Insights on aerosol properties using two decades-long ground-based remote sensing datasets in Moldova, Eastern Europe.

Aerosol optical properties were studied over Chisinau in Moldova, one of the longest running AERONET sites in Eastern Europe. During two decades (September 1999-November 2018), the mean aerosol optical depth (AOD) and Angstrom exponent (AE) were observed as 0.21 ± 0.

High-Precision Optical Coherence Tomography Navigated Laser Retinopexy for Retinal Breaks.

The prevalent cause of retinal detachment is a full-thickness retinal break and the ingress of fluid into the subretinal space. To prevent progression of the detachment, laser photocoagulation (LPC) lesions are placed around the break in clinical practice to seal the tissue. Unlike the usual application under indirect ophthalmoscopy, we developed a semi-automatic treatment planning software based on a sequence of optical coherence tomography (OCT) scans to perform navigated LPC treatment.

Chemical bond imaging using torsional and flexural higher eigenmodes of qPlus sensors.

Non-contact atomic force microscopy (AFM) with CO-functionalized tips allows visualization of the chemical structure of adsorbed molecules and identify individual inter- and intramolecular bonds. This technique enables in-depth studies of on-surface reactions and self-assembly processes. Herein, we analyze the suitability of qPlus sensors, which are commonly used for such studies, for the application of modern multifrequency AFM techniques.

Surface-controlled reversal of the selectivity of halogen bonds.

Intermolecular halogen bonds are ideally suited for designing new molecular assemblies because of their strong directionality and the possibility of tuning the interactions by using different types of halogens or molecular moieties. Due to these unique properties of the halogen bonds, numerous areas of application have recently been identified and are still emerging. Here, we present an approach for controlling the 2D self-assembly process of organic molecules by adsorption to reactive vs.

Single-asperity sliding friction across the superconducting phase transition.

In sliding friction, different energy dissipation channels have been proposed, including phonon and electron systems, plastic deformation, and crack formation. However, how energy is coupled into these channels is debated, and especially, the relevance of electronic dissipation remains elusive. Here, we present friction experiments of a single-asperity sliding on a high- superconductor from 40 to 300 kelvin.

On-Surface Synthesis and Characterization of a Cycloarene: C108 Graphene Ring.

The synthesis of cycloarenes in solution is challenging because of their low solubility and the often hindered cyclodehydrogenation reaction of their nonplanar precursors. Using an alternative on-surface synthesis protocol, we achieved an unprecedented double-stranded hexagonal cycloarene containing 108 sp carbon atoms. Its synthesis is based on hierarchical Ullmann coupling and cyclodehydrogenation of a specially designed precursor on a Au(111) surface.

Damping of surface waves due to crude oil/oil emulsion films on water.

In this paper results of laboratory studies of damping of gravity-capillary waves due to emulsified oil films (EOF) are presented and compared to crude oil films (COF). A laboratory method based on measuring the damping coefficient and the length of parametrically generated gravity-capillary waves is applied to a 50% EOF and to crude oil films. Measurements of wave damping were carried out in a range of surface wave lengths, corresponding to Bragg waves of X- to Ka-band radars.

Bond-Level Imaging of the 3D Conformation of Adsorbed Organic Molecules Using Atomic Force Microscopy with Simultaneous Tunneling Feedback.

The chemical structure and orientation of molecules on surfaces can be visualized using low temperature atomic force microscopy with CO-functionalized tips. Conventionally, this is done in constant-height mode by measuring the frequency shift of the oscillating force sensor. However, this method is unsuitable for analyzing 3D objects.

Precise Monoselective Aromatic C-H Bond Activation by Chemisorption of Meta-Aryne on a Metal Surface.

Aromatic C-H bond activation has attracted much attention due to its versatile applications in the synthesis of aryl-containing chemicals. The major challenge lies in the minimization of the activation barrier and maximization of the regioselectivity. Here, we report the highly selective activation of the central aromatic C-H bond in meta-aryne species anchored to a copper surface, which catalyzes the C-H bond dissociation.

Hierarchical Dehydrogenation Reactions on a Copper Surface.

Hierarchical control of chemical reactions is being considered as one of the most ambitious and challenging topics in modern organic chemistry. In this study, we have realized the one-by-one scission of the X-H bonds (X = N and C) of aromatic amines in a controlled fashion on the Cu(111) surface. Each dehydrogenation reaction leads to certain metal-organic supramolecular structures, which were monitored in single-bond resolution via scanning tunneling microscopy and noncontact atomic force microscopy.

Imaging Successive Intermediate States of the On-Surface Ullmann Reaction on Cu(111): Role of the Metal Coordination.

The in-depth knowledge about on-surface reaction mechanisms is crucial for the tailor-made design of covalently bonded organic frameworks, for applications such as nanoelectronic or -optical devices. Latest developments in atomic force microscopy, which rely on functionalizing the tip with single CO molecules at low temperatures, allow to image molecular systems with submolecular resolution. Here, we are using this technique to study the complete reaction pathway of the on-surface Ullmann-type coupling between bromotriphenylene molecules on a Cu(111) surface.

Universality of periodicity as revealed from interlayer-mediated cracks.

A crack and its propagation is a challenging multiscale materials phenomenon of broad interest, from nanoscience to exogeology. Particularly in fracture mechanics, periodicities are of high scientific interest. However, a full understanding of this phenomenon across various physical scales is lacking.

Novel roles for well-known players: from tobacco mosaic virus pests to enzymatically active assemblies.

The rod-shaped nanoparticles of the widespread plant pathogen tobacco mosaic virus (TMV) have been a matter of intense debates and cutting-edge research for more than a hundred years. During the late 19th century, their behavior in filtration tests applied to the agent causing the 'plant mosaic disease' eventually led to the discrimination of viruses from bacteria. Thereafter, they promoted the development of biophysical cornerstone techniques such as electron microscopy and ultracentrifugation.

Calibration of quartz tuning fork spring constants for non-contact atomic force microscopy: direct mechanical measurements and simulations.

Quartz tuning forks are being increasingly employed as sensors in non-contact atomic force microscopy especially in the "qPlus" design. In this study a new and easily applicable setup has been used to determine the static spring constant at several positions along the prong of the tuning fork. The results show a significant deviation from values calculated with the beam formula.

Scaling laws of structural lubricity.

"Structural lubricity" refers to a unique friction state in which two flat surfaces are sliding past each other with ultralow resistance due to incommensurate atomic lattice structures. In this case, theory anticipates sublinear scaling for the area dependence of friction. Here, we experimentally confirm these predictions by measuring the sliding resistance of amorphous antimony and crystalline gold nanoparticles on crystalline graphite.

Investigation of helicon ion source extraction systems.

Various versions of an extraction system for a helicon ion source have been investigated in high plasma density (>10(12) cm(-3)) modes. The measurements of the plasma density were carried out with a microwave interferometer. Experiments were performed with hydrogen and helium gases.