The effect of water on gold supported chiral graphene nanoribbons: rupture of conjugation by an alternating hydrogenation pattern

In the last few years we have observed a breakpoint in the development of graphene-derived technologies, such as liquid phase filtering and their application to electronics. In most of these cases, they imply exposure of the material to solvents and ambient moisture, either in the fabrication of the material or the final device. The present study demonstrates the sensitivity of graphene nanoribbon (GNR) zigzag edges to water, even in extremely low concentrations. We have addressed the unique reactivity of (3,1)-chiral GNR with moisture on Au(111). Water shows a reductive behaviour, hydrogenating the central carbon of the zigzag segments. By combining scanning tunnelling microscopy (STM) with simulations, we demonstrate how their reactivity reaches a thermodynamic limit when half of the unit cells are reduced, resulting in an alternating pattern of hydrogenated and pristine unit cells starting from the terminal segments. Once a quasi-perfect alternation is reached, the reaction stops regardless of the water concentration. The hydrogenated segments limit the electronic conjugation of the GNR, but the reduction can be reversed both by tip manipulation and annealing. Selective tip-induced dehydrogenation allowed the stabilization of radical states at the edges of the ribbons, while the annealing of the sample completely recovered the original, pristine GNR.

Coverage-modulated halogen bond geometry transformation in supramolecular assemblies

Halogen bonding (HB) has emerged as a promising route for designing supramolecular assemblies due to its directional nature and versatility in modifying interactions through the choice of halogens and molecular entities. Despite this, methods for tuning these interactions on surfaces, particularly in terms of directionality, are limited. In this study, we present a strategy for tuning the directionality of self-assembly processes in homomolecular organic compounds on inert metal surfaces. A variety of halogen-halogen geometries can promote highly-extended one-dimensional or two-dimensional self-assembly depending on the molecular coverage. Our results indicate that under lower molecular coverage conditions, robust one-dimensional (1D) structures promote the self-assembly of halogen-bonded molecules on Au(111). At certain coverage, a transformation from type-I to synthon halogen bonding is observed, leading to an extended hexagonal pattern of molecular assembly. The atomistic details of the structures are experimentally studied using high-resolution atomic force microscopy and supported by first-principle calculations. We employed DFT to evaluate the interplay between electrostatics and dispersion forces driving both type-I and synthon assemblies. The results reveal a halogen-bond geometry transformation induced by a subtle balance of molecule-molecule interaction. Finally, we investigate the capability of the halogen-bonded supramolecular assembly to periodically confine electronic quantum states and single atoms. Our findings demonstrate the versatility of sigma-bonding in regulating molecular assembly and provide new insights for tailoring functional molecular structures on an inert metal substrate.

Visualization of π-hole in molecules by means of Kelvin probe force microscopy

Submolecular charge distribution significantly affects the physical-chemical properties of molecules and their mutual interaction. One example is the presence of a π-electron-deficient cavity in halogen-substituted polyaromatic hydrocarbon compounds, the so-called π-holes, the existence of which was predicted theoretically, but the direct experimental observation is still missing. Here we present the resolution of the π-hole on a single molecule using the Kelvin probe force microscopy, which supports the theoretical prediction of its existence. In addition, experimental measurements supported by theoretical calculations show the importance of π-holes in the process of adsorption of molecules on solid-state surfaces. This study expands our understanding of the π-hole systems and, at the same time, opens up possibilities for studying the influence of submolecular charge distribution on the chemical properties of molecules and their mutual interaction.

On-surface synthesis of non-benzenoid conjugated polymers by selective atomic rearrangement of ethynylarenes

Here, we report a new on-surface synthetic strategy to precisely introduce five-membered units into conjugated polymers from specifically designed precursor molecules that give rise to low-bandgap fulvalene-bridged bisanthene polymers. The selective formation of non-benzenoid units is finely controlled by the annealing parameters, which govern the initiation of atomic rearrangements that efficiently transform previously formed diethynyl bridges into fulvalene moieties. The atomically precise structures and electronic properties have been unmistakably characterized by STM, nc-AFM, and STS and the results are supported by DFT theoretical calculations. Interestingly, the fulvalene-bridged bisanthene polymers exhibit experimental narrow frontier electronic gaps of 1.2 eV on Au(111) with fully conjugated units. This on-surface synthetic strategy can potentially be extended to other conjugated polymers to tune their optoelectronic properties by integrating five-membered rings at precise sites.

Distal biceps ruptures repair: Experience with 80 cases

INTRODUCTION AND OBJECTIVES

Rupture of distal biceps has a frequency of 1.2 cases per 100,000 population. Conservative treatment presents a loss in supination of 40% and flexion of 30%, like transfers to the brachialis. Our goal is to review our experience with anatomical reattachment.

MATERIAL AND METHODS

Cohorts study. We analized an historic cohort, although recent, treated with double approach (Boyd-Anderson) compared to another prospective cohort (treated with single and double approach). Sample size of 80 patients. Mean age of 48.9±5.9years. We analyzed laterality, time to diagnosis, presurgery time, surgery time, approach, type of reintegration, rehabilitation time, Mayo Elbow Performance Score (MEPS), biomechanical study and complications. Follow up from 2 years to 7years.

RESULTS

Time for diagnosis was about 4days. Preoperative time: 12.2±6.4 days. Surgical time: 61.9±15.7minutes. We used the two-way surgical approach (Boyd-Anderson-Morrey) in 78.8% of patients, and the anterior surgical approach (Henry) in 21.2% of cases. Transosseous reinsertion was made in 45% of cases, with screw anchor in 40% and with cortical button in 15%. Rehabilitation time: 91±29.7 days. MEPS: 88±11.7 points. There was loss of flexor strength of 28±16.6%.

COMPLICATIONS

1case of proximal radioulnar synostosis, 2 radial transient paralysis and 5 cases with residual stiffness. Hypothesis contrast: We reached best results in MEPS with double surgical approach (P=.009), with fewer complications (P=.008). We observed increased pain with cortical buttons (P<.05) and less surgical time if patient was operated before 1week (P=.03). Relative risk of 0.2 when we compared type of approach with radial nerve lesion risk, considering that double approach had less cases, what it would be consider as a protective factor.

CONCLUSIONS

In our experience, we believe that anatomic reattachment is an effective treatment. Double surgical approach presents best result in MEPS, with fewer complications than with anterior approach.

A Betting- and Lottery-Based Method for Fuzzy Probability Elicitation

It is very common to use linguistic term scales, whose terms are previously associated with different fuzzy numbers to assign probabilities to events in decision-making processes. However, the rigidity of such scales generates bias in the probability elicitation process and does not allow experts to adequately express their probabilistic judgments. We propose a betting and lottery-based method for eliciting a fuzzy number from the expert that represents his/her probabilistic judgments for a given event, along with a quality measure of the probabilistic judgments based on precision and consistency measures. We also enact a simulation process to analyze possible biases in the proposed fuzzy probability elicitation method.