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Abstract: The deposition of potassium onto TiO2(110) surface at 330K and the effects of post-annealing are investigated by scanning tunneling microscopy (STM), thermal desorption spectroscopy (TDS) and Auger-electron spectroscopy (AES). At lower K coverages (a few percentage of a monolayer), 3–4nm long and 1–2nm wide islands appear which can be identified with K covered regions. At higher K coverages, the surface exhibits disordered structures. Depending on the initial K coverage, the annealing above 700K in UHV results in ordering of the surface. For app. 1/3 monolayer K and annealing at around 900K, the entire surface reconstructs into a (1×2) phase accompanied by the appearance of pits with an average diameter of 20–30nm. This morphology is characteristic up to 1000K. Above this temperature, the recovery of the (1×1) phase was observed. At low K coverages (<0.2ML) the annealing at 1000K resulted in the formation of protruding islands of approximately 2×2nm2 which were identified with a strongly bonded surface compound containing K. [Copyright &y& Elsevier]

Abstract: Tunneling induced decomposition of Mo(CO)6 from the gas phase was studied on TiO2(110) surface by scanning tunneling microscopy (STM) and spectroscopy (STS). The efficiency of the procedure was followed by measuring the dot volume as a proportional indicator of the amount of the decomposed precursor. It was found that below 1 × 10−5 Pa background pressure of Mo(CO)6, there is no measurable effect and above 1 × 10−4 Pa, the nanodot size is too large compared to the curvature of the tip (20–40 nm). A threshold bias of +3.1(±0.1) V on the sample was measured for the decomposition of Mo(CO)6 in gas ambient. In the absence of the precursor, dot formation was observed only above +3.7(±0.2) V, in good agreement with the results reported in our earlier work about nanolithography on clean TiO2(110) substrate (E. Kriván, A. Berkó: J. Vac. Sci. & Tech. B 15(1) (1997)25). By applying voltages in the range of 3.1–3.5 V, a systematic enlargement of the created nanodots was found in the range of 2–20 s of duration and 0.01–1.0 nA of tunneling current. The I–V curves detected on the top of the nanodots have shown that the created features are of insulator character. This observation indicates that the decomposition of Mo(CO)6 is also accompanied by oxidation of the deposited Mo species. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) calculations were used to study the adsorption of rhodium on a TiO2(110)-1×1 surface as a function of coverage. It was found that Rh atom prefers the hollow site between a bridging oxygen atom, a threefold oxygen atom and a fivefold coordinated Ti atom, regardless of the coverage used. DFT calculations also suggest that Rh–Rh interaction is attractive along the [001] direction, implying that the Rh 1D nanostructure should grow preferentially along this direction. Simulated Rh dimer clusters resemble strongly Pd dimers resolved in STM experiments suggesting that both metals occupy the same adsorption site at the TiO2(110) surface. [Copyright &y& Elsevier]

For nearly 50 years, the vision of using single molecules in circuits has been seen as providing the ultimate miniaturization of electronic chips. An advanced example of such a molecular electronics chip is presented here, with the important distinction that the molecular circuit elements play the role of general-purpose single-molecule sensors. The device consists of a semiconductor chip with a scalable array architecture. Each array element contains a synthetic molecular wire assembled to span nanoelectrodes in a current monitoring circuit. A central conjugation site is used to attach a single probe molecule that defines the target of the sensor. The chip digitizes the resulting picoamp-scale current-versus-time readout from each sensor element of the array at a rate of 1,000 frames per second. This provides detailed electrical signatures of the single-molecule interactions between the probe and targets present in a solution-phase test sample. This platform is used to measure the interaction kinetics of single molecules, without the use of labels, in a massively parallel fashion. To demonstrate broad applicability, examples are shown for probe molecule binding, including DNA oligos, aptamers, antibodies, and antigens, and the activity of enzymes relevant to diagnostics and sequencing, including a CRISPR/Cas enzyme binding a target DNA, and a DNA polymerase enzyme incorporating nucleotides as it copies a DNA template. All of these applications are accomplished with high sensitivity and resolution, on a manufacturable, scalable, all-electronic semiconductor chip device, thereby bringing the power of modern chips to these diverse areas of biosensing., Competing Interests: Competing interest statement: All authors having the Roswell affiliation (affiliation “a”) are employed by Roswell Biotechnologies, San Diego, CA 92121., (Copyright © 2022 the Author(s). Published by PNAS.)

Scaling up community-based participatory research (CBPR) remains challenging. This case-study reports on how, and under which conditions, a CBPR project aiming at promoting exercise among socially disadvantaged women (BIG) scaled up at four project sites. As part of BIG, researchers support city administrations in implementing a participatory project to reach socially disadvantaged women for exercise. The case study was conducted in winter 2020 in southern Germany and is based on a co-creative process involving city administrators and researchers. Following Kohl and Cooley's scaling up dimensions, scaling up BIG was investigated at the four sites using a mixed-method approach. Course registrations and offers were analysed, and qualitative interviews ( n = 4) with administrative staff members were conducted and analysed using content analysis. The geographical coverage of exercise classes, the addressed groups, and the utilisation of participatory methods by city administrations are described. All four sites managed to scale-up project activities. Three of the four sites reported that further growth of the project was no longer possible due to limited resources. All sites attempted to reach a larger number of, and more diverse, women. One site managed to scale-up the use of participatory methods within the city administration. The following important facilitators for scaling up CBPR projects were reported: advertisements tailored to the needs of the addressed women, utilising participatory approaches, and equipping project coordinators with sufficient resources.

Four decades after the first (and only) reported synthesis of kekulene, this emblematic cycloarene has been obtained again through an improved route involving the construction of a key synthetic intermediate, 5,6,8,9-tetrahydrobenzo[ m ]tetraphene, by means of a double Diels-Alder reaction between styrene and a versatile benzodiyne synthon. Ultra-high-resolution AFM imaging of single molecules of kekulene and computational calculations provide additional support for a molecular structure with a significant degree of bond localization in accordance with the resonance structure predicted by the Clar model.

The synthesis of a threefold symmetric nanographene with 19 cata-fused benzene rings distributed within six branches is reported. This flat dendritic starphene, which is the largest unsubstituted cata-condensed PAH that has been obtained to date, was prepared in solution by means of a palladium-catalyzed aryne cyclotrimerization reaction and it was characterized on surface by scanning probe microscopy with atomic resolution., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Rearrangements that change the connectivity of a carbon skeleton are often useful in synthesis, but it can be difficult to follow their mechanisms. Scanning probe microscopy can be used to manipulate a skeletal rearrangement at the single-molecule level, while monitoring the geometry of reactants, intermediates and final products with atomic resolution. We studied the reductive rearrangement of 1,1-dibromo alkenes to polyynes on a NaCl surface at 5 K, a reaction that resembles the Fritsch-Buttenberg-Wiechell rearrangement. Voltage pulses were used to cleave one C-Br bond, forming a radical, then to cleave the remaining C • -Br bond, triggering the rearrangement. These experiments provide structural insight into the bromo-vinyl radical intermediates, showing that the C=C • -Br unit is nonlinear. Long polyynes, up to the octayne Ph-(C≡C) 8 -Ph, have been prepared in this way. The control of skeletal rearrangements opens a new window on carbon-rich materials and extends the toolbox for molecular synthesis by atom manipulation.

Using scanning probe microscopy techniques, at low temperatures and in ultrahigh vacuum, individual molecules adsorbed on surfaces can be probed with ultrahigh resolution to determine their structure and details of their conformation, configuration, charge states, aromaticity, and the contributions of resonance structures. Functionalizing the tip of an atomic force microscope with a CO molecule enabled atomic-resolution imaging of single molecules, and measurement of their adsorption geometry and bond-order relations. In addition, by using scanning tunneling microscopy and Kelvin probe force microscopy, the density of the molecular frontier orbitals and the electric charge distribution within molecules can be mapped. Combining these techniques yields a high-resolution tool for the identification and characterization of individual molecules. The single-molecule sensitivity and the possibility of atom manipulation to induce chemical reactions with the tip of the microscope open up unique applications in chemistry, and differentiate scanning probe microscopy from conventional methods for molecular structure elucidation. Besides being an aid for challenging cases in natural product identification, atomic force microscopy has been shown to be a powerful tool for the investigation of on-surface reactions and the characterization of radicals and molecular mixtures. Herein we review the progress that high-resolution scanning probe microscopy with functionalized tips has made for molecular structure identification and characterization, and discuss the challenges it will face in the years to come., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Antiaromatic and open-shell molecules are attractive because of their distinct electronic and magnetic behaviour. However, their increased reactivity creates a challenge for probing their properties. Here, we describe the on-surface and in-solution generation and characterisation of a highly reactive antiaromatic molecule: indeno[1,2-b]fluorene (IF). In solution, we generated IF by KI-induced dehalogenation of a dibromo-substituted precursor molecule and found that IF survives for minutes at ambient conditions. Using atom manipulation at low temperatures we generated IF on Cu(111) and on bilayer NaCl. On these surfaces, we characterised IF by bond-order analysis using non-contact atomic force microscopy with CO-functionalised tips and by orbital imaging using scanning tunnelling microscopy. We found that the closed-shell configuration and antiaromatic character predicted for gas-phase IF are preserved on the NaCl film. On Cu(111), we observed significant bond-order reorganisation within the s-indacene moiety because of chemisorption, highlighting the importance of molecule surface interactions on the π-electron distribution.

We describe the generation of a meta-aryne at low temperature (T = 5 K) using atomic manipulation on Cu(111) and on bilayer NaCl on Cu(111). We observe different voltage thresholds for dehalogenation of the precursor and different reaction products depending on the substrate surface. The chemical structure is resolved by atomic force microscopy with CO-terminated tips, revealing the radical positions and confirming a diradical rather than an anti-Bredt olefin structure for this meta-aryne on NaCl.

Aiming to study new motifs, potentially active as functional materials, we performed the synthesis of a naphthodiazaborinine (the BN isostere of the phenalenyl anion) that is bonded to a hindered di-ortho-substituted aryl system (9-anthracene). We used atomic force microscopy (AFM) and succeeded in both the verification of the original nonplanar structure of the molecule and the planarization of the skeleton by removing H atoms that cause steric hindrance. This study demonstrated that planarization by atomic manipulation is a possible route for extending molecular identification by AFM to nonplanar molecular systems that are difficult to probe with AFM directly.

We investigated single-layer graphene on SiC(0001) by atomic force and tunneling current microscopy, to separate the topographic and electronic contributions from the overall landscape. The analysis revealed that the roughness evaluated from the atomic force maps is very low, in accord with theoretical simulations. We also observed that characteristic electron scattering effects on graphene edges and defects are not accompanied by any out-of-plane relaxations of carbon atoms.

In this paper, we show that simultaneous noncontact atomic force microscopy (nc-AFM) and scanning tunneling microscopy (STM) is a powerful tool for molecular discrimination on the Si(111)-7 × 7 surface, even at room temperature. Using density functional theory modeling, we justify this approach and show that the force response allows us to distinguish straightforwardly between molecular adsorbates and common defects, such as vacancies. Finally, we prove that STM/nc-AFM method is able to determine attachment sites of molecules deposited on semiconductor surface at room temperature.

In this paper we present a comparison of three different methods that can be used for estimating the stiffness of qPlus sensors. The first method is based on continuum theory of elasticity. The second (Cleveland's method) uses the change in the eigenfrequency that is induced by the loading of small masses. Finally, the stiffness is obtained by analysis of the thermal noise spectrum. We show that all three methods give very similar results. Surprisingly, neither the gold wire nor the gluing give rise to significant changes of the stiffness in the case of our home-built sensors. Furthermore we describe a fast and cost-effective way to perform Cleveland's method. This method is based on gluing small pieces of a tungsten wire; the mass is obtained from the volume of the wire, which is measured by optical microscopy. To facilitate detection of oscillation eigenfrequencies under ambient conditions, we designed and built a device for testing qPlus sensors.

Chemical identification of individual atoms in mixed In-Sn chains grown on a Si(100)-(2 × 1) surface was investigated by means of room temperature dynamic noncontact AFM measurements and DFT calculations. We demonstrate that the chemical nature of each atom in the chain can be identified by means of measurements of the short-range forces acting between an AFM tip and the atom. On the basis of this method, we revealed incorporation of silicon atoms from the substrate into the metal chains. Analysis of the measured and calculated short-range forces indicates that even different chemical states of a single atom can be distinguished.

We present the results of simultaneous scanning-tunneling and frequency-modulated dynamic atomic force microscopy measurements with a qPlus setup. The qPlus sensor is a purely electrical sensor based on a quartz tuning fork. If both the tunneling current and the force signal are to be measured at the tip, a cross-talk of the tunneling current with the force signal can easily occur. The origin and general features of the capacitive cross-talk will be discussed in detail in this contribution. Furthermore, we describe an experimental setup that improves the level of decoupling between the tunneling-current and the deflection signal. The efficiency of this experimental setup is demonstrated through topography and site-specific force/tunneling-spectroscopy measurements on the Si(111) 7×7 surface. The results show an excellent agreement with previously reported data measured by optical interferometric deflection.

Rh-Au core-shell nanoparticles were fabricated on TiO(2)(110) surface by physical vapor deposition (PVD) of Rh followed by exposure of Au at elevated sample temperature (500 K). The morphology of the bimetallic particles was checked by scanning tunneling microscopy (STM). The chemical composition of the particles was characterized by low energy ion scattering (LEIS) method. It was shown that the "seeding + growing" method described previously for growth of monometallic particles in narrow size distribution (Berko, A. et al. J. Catal. 1999, 182, 511) can also be applied for fabrication of bimetallic nanoparticles. The large mean free path of surface diffusion of gold on the oxide support makes the accumulation of Au possible exclusively on the Rh seeds formed in the first step of the procedure. By performing careful STM and LEIS experiments, it was proven that, for appropriate Au and Rh coverages, the postdeposited Au completely and uniformly covers the Rh nanoparticles.