This review aims at giving the readers the basic concepts needed to understand two-dimensional bimolecular organizations at the vacuum–solid interface. The first part describes and analyzes molecules–molecules and molecules–substrates interactions. The current limitations and needs in the understanding of these forces are also detailed. Then, a critical analysis of the past and recent advances in the field is presented by discussing most of the key papers describing bicomponents self-assembly on solid surface in an ultrahigh vacuum environment. These sections are organized by considering decreasing molecule–molecule interaction strengths (i.e. starting from strong directional multiple H bonds up to weaker nondirectional bonds taking into account the increasing fundamental role played by the surface). Finally, we conclude with some research directions (predicting self-assembly, multi-components systems, and nonmetallic surfaces) and potential applications (porous networks and organic surfaces).

Traumatic SAH frequently occurs in patients with TBI, but it is difficult to detect and grade. Traumatic SAH is associated with more severe CT findings and a worse patient outcome.

Based on a low-temperature scanning tunneling microscopy study, we present a direct visualization of a cycloaddition reaction performed for some specific fluorinated maleimide molecules deposited on graphene. Up to now, it was widely admitted that such a cycloaddition reaction can not happen without pre-existing defects. However, our study shows that the cycloaddition reaction can be carried out on a defect-free basal graphene plane at room temperature. In the course of covalently grafting the molecules to graphene, the sp conjugation of carbon atoms was broken, and local sp bonds were created. The grafted molecules perturbed the graphene lattice, generating a standing-wave pattern with an anisotropy which was attributed to a (1,2) cycloaddition, as revealed by T-matrix approximation calculations. DFT calculations showed that while both (1,4) and (1,2) cycloadditions were possible on free-standing graphene, only the (1,2) cycloaddition could be obtained for graphene on SiC(0001). Globally averaging spectroscopic techniques, XPS and ARPES, were used to determine the modification in the elemental composition of the samples induced by the reaction, indicating an opening of an electronic gap in graphene.

Chemical reactions converting sp 2 to sp 3 hybridization have been demonstrated to be a fascinating yet challenging route to functionalize graphene. So far, it has not been possible to precisely control the reaction sites nor their lateral order at the atomic/molecular scale. The application prospects have been limited for reactions requiring long soaking, heating, electric pulses, or probe tip press.Herein, we demonstrate a spatially-selective photocycloaddition reaction of a two-dimensional (2D) molecular network with defect-free basal plane of single-layer graphene. Directly visualized at the sub-molecular level, the cycloaddition is triggered by ultraviolet irradiation in ultrahigh vacuum, requiring no aid of the graphene Moiré pattern. The reaction involves both [2+2] and [2+4] cycloaddition, with the reaction sites aligned into a 2D extended and well-ordered array, inducing a bandgap for the reacted graphene layer. This work provides a solid base for designing and engineering graphene-based optoelectronic and microelectronic devices.

Gold nanoparticles protected with thiolate Calix[4]arenes hosts were synthesized through an exchange reaction in toluene, starting from tetraoctyl ammonium bromide stabilized gold nanoparticles having a mean core size of ∼6 nm. In low polar solvents, these new Calix[4]arene-coated nanoparticles are able to self-assemble through supramolecular interactions with dialkyl dipyridinium-based guests (2−3). The guest-induced self-assembly process between nanoparticles has been studied using UV−vis spectroscopy, dynamic light scattering, and TEM measurements. The size and the solubility of the aggregates strongly depend on the length and rigidity of the bifunctional guest used as “supramolecular linker” between the nanoparticles. In particular, the long and flexible guest 2 gives rise to superaggregates of nanoparticles that remain soluble in common low polar solvents.

The conformations and the self-assembly process of tetrathiafulvalene (TTF) derivatives functionalized by lateral alkylthio chains deposited on graphene/SiC(0001) in ultrahigh vacuum (UHV) and at the solid–liquid interface are studied by scanning tunneling microscopy (STM). The study in UHV evidences a “molecular fastener” effect induced by the increase of van der Waals interactions between the alkylthio side chains which forces the major part of the molecules to self-organize in π–π stacked edge-on conformation. The study at the solid–liquid interface reveals a drastically different behavior with molecules lying flat on the surface as the solvent is involved in the stabilization of the molecular layer. This work raises a burning issue concerning the choice of the deposition method for graphene functionalization with such molecules.

On-surface synthesis (OSS) involving relatively high energy barriers remains challenging due to a typical dilemma: firm molecular anchor is required to prevent molecular desorption upon the reaction, whereas sufficient lateral mobility is crucial for subsequent coupling and assembly. By locking the molecular precursors on the substrate then unlocking them during the reaction, we present a strategy to address this challenge. High-yield synthesis based on well-defined decarboxylation, intermediate transition, and hexamerization is demonstrated, resulting in an extended and ordered network exclusively composed of the newly synthesized macrocyclic compound. Thanks to the steric hindrance of its maleimide group, we attain a preferential selection of the coupling. This work unlocks a promising path to enrich the reaction types and improve the coupling selectivity hence the structual homogeneity of the final product for OSS.

Transition-metal carbides have sparked unprecedented enthusiasm as high-performance catalysts in recent years. Still, the catalytic properties of copper carbide remain unexplored. By introducing subsurface carbon to Cu(111), a displacement reaction of a proton in a carboxyl acid group with a single Cu atom is demonstrated at the atomic scale and room temperature. Its occurrence is attributed to the C-dopinginduced local charge of surface Cu atoms (up to + 0.30 e/ atom), which accelerates the rate of on-surface deprotonation via reduction of the corresponding energy barrier, thus enabling the instant displacement of a proton with a Cu atom when the molecules adsorb on the surface. This well-defined and robust Cu d+ surface based on subsurface-carbon doping offers a novel catalytic platform for on-surface synthesis.In recent years, transition metal carbides (TMCs), for example, molybdenum carbide, titanium carbide, etc. have shown considerable potential as high-performance catalysts in hydrogen evolution, [1] carbon dioxide reduction, [2] deoxygenation of biomass, [3] and methane dehydroaromatization. [4] TMC catalysts not only accelerate the reaction rate, alter the pathway, but also improve the reaction selectivity, [5] and even enable reactions that cannot be triggered by conventional metal catalysts. [6] However, the reported work has substantially focused on the fabrication of TMCs and their catalytic performance based on spectroscopic measurements, whilst intuitive studies of catalytic reactions on TMCs at the atomic/ molecular scales are rather scarce.Copper (Cu), as one of the most classical catalysts, has been applied extensively in selective oxidation, [7] coupling reaction, [8] carbon dioxide reduction, [9] etc. It has been proposed that charge localization on Cu (Cu d+ ) achieved by doping nonmetals (e.g. oxygen, [9b, 10] boron, [11] nitrogen [12] ) can significantly boost the catalytic activities of the parent metal and modify the reaction process, for example, enhance the Faradaic efficiency for C 2 hydrocarbons in carbon dioxide reduction. [11a] Since the extrinsic species on top of a Cu surface have a high probability to be removed or modified upon chemical reactions, which results in the reduction of Cu d+ to Cu 0 , [9b, 13] subsurface doping is believed to be advantageous for long-term, stable catalytic performance. [10b, 11a] In regard to compatibility with Cu, carbon (C), one of the typical minorities in natural Cu bulk, certainly holds advantages over other elements. [14] However, local charge of Cu surface induced by C-doping and the catalytic properties of Cu carbide or C-doped Cu are still unexplored.Herein, we report a locally charged Cu surface layer induced by subsurface C (C-Cu d+ ) and its catalytic application for an on-surface displacement reaction (Scheme 1). Applying 3,5-bis(carboxyl acid)-phenyl-3-maleimide (C 12 H 7 NO 6 , denoted as BCPM) on C-Cu d+ , efficient substitution of the proton in each carboxylic acid (CA) group of BCPM by a single Cu atom is demonstrated at ...