Anisotropic growth of the thiophene-based layer on Si(111)-B

International audienceThe formation of large assemblies on the Si(111)-B surface is discussed with the help of STM simulations and DFT calculations. Although highly regular assemblies of DTB10B along the Si row direction are observed, the existence of two herringbone isomers introduces a lower periodicity within the 2D molecular network. The formation of herringbone units is explained by weak intermolecular interactions while the 1D assembling depends mainly on the interactions of the C10 side chains with the Si(111)-B surface

Comprendre la cytotoxicité des nanoparticules métalliques

National audienceLe stress oxydant est l’un des processus incriminés dans la genèse de nombreuses maladies, comme les cancers. Ce stress oxydant est caractérisé par la production d’espèces oxydantes appelées ROS (reactive oxygene species), qui peuvent altérer l’ADN dans les cellules, via deux mécanismes d’échanges d’électrons parfaitement décrits. Ainsi, pour contrer ce phénomène, les cellules contiennent certaines molécules, telles que des catéchols, qui jouent le rôle de systèmes efficaces d’auto-défense en inhibant la formation des ROS. Les nanoparticules sont suspectées d’être à l’origine d’un stress oxydant très agressif. Mais si la toxicité des nanoparticules d’oxyde métalliques est expliquée par les deux mécanismes classiques d’échange d’électrons, le mécanisme d’action des nanoparticules métalliques reste méconnu alors qu’elles sont pourtant plus toxiques que leurs alter-ego à base d’oxydes. Pour comprendre le rôle de la surface des nanoparticules métalliques dans la production de ROS, nous avons étudié une surface de cuivre interagissant avec une couche moléculaire de catéchol, sous ultra-haut vide. Les observations de molécules individuelles par microscopie à effet tunnel, par l’analyse à haute résolution de la composition de chaque molécule, et par des calculs ab initio, ont révélé le mécanisme permettant la formation des ROS par une surface de cuivre. Nous avons montré que la surface de cuivre est le siège d’une réaction d’oxydo-réduction très particulière, dit “intramoléculaire”. Les molécules de catéchol voient leurs fonctions alcool oxydées alors que d’autres fonctions sont réduites, grâce à un transfert d’électrons entre les substituants d’une même molécule. Cette transformation est gouvernée par l’alignement des niveaux électroniques de la surface de cuivre et des molécules, la surface de cuivre « forçant » la molécule à se transformer pour permettre son adsorption. Ainsi, la cytotoxicité des nanoparticules métalliques semble être expliquée via ce nouveau mécanisme d’action, même si des expériences in vitro sont nécessaires pour le confirmer

Molecular self-assembled networks on silicon surface

International audienceNowadays more than 90% of published results show molecules adsorbed onto metallic or HOPG surfaces. This is explained by the low reactivity between molecules and these surfaces which induce a molecular diffusion and the possibility to observe large and perfect self-assemblies. Nevertheless, there are a real economic and technological interests to develop molecular self-assembled layers onto semiconductors and in particular onto silicon surfaces. Actually, due to the existence of Si dangling bonds which induce a strong interaction between molecules and substrates, the formation of such molecular layers is still a real challenge. To circumvent this problem, we need atomically passivated Si surface. Here, an original unreactive silicon surface is presented: the high boron doped silicon √3x√3-SiB (111) reconstruction. Since 10 years, very amazing results have been obtained showing large and perfect molecular self-assemblies by deposition of home-made and specifically designed aromatic molecules on this silicon surface [See Fig. 1]. The morphology of each supramolecular network is explained by the competition between molecule-moleucle and molecuel-surface interactions [1-4]

Photochemistry Highlights on On‐Surface Synthesis

International audienceOn‐surface chemistry is a promising way to achieve the bottom‐up construction of covalently‐bonded molecular precursors into extended atomically‐precise polymers adsorbed on surfaces. These polymers exhibit unprecedented physical or chemical properties which are of great interest for various potential applications. These nanostructures were mainly obtained in ultra‐high vacuum (UHV) on noble metal single‐crystal surfaces by thermal annealing as stimulus to provoke the polymerization with a catalytic role of the surface adatoms. Nevertheless, photons are also a powerful source of energy to induce the formation of covalent architectures, even if it is less‐used on surfaces than in solution. In this minireview, we discuss the photo‐induced on‐surface polymerization from the basic mechanisms of photochemistry to the formation of extended polymers on different kinds of surfaces, which are characterized by scanning probe microscopies

On-Surface Chemistry on Low-Reactive Surfaces

International audience<span style="font-size:11.0pt;line-height: 115%;font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin; mso-fareast-font-family:&quot;Times New Roman&quot;;mso-fareast-theme-font:minor-fareast; mso-hansi-theme-font:minor-latin;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language: FR;mso-bidi-language:AR-SA"lang="EN-US" xml:lang="EN-US"&gtzero-dimensional (0D),mono-dimensional (1D), or two-dimensional (2D) nanostructures withwell-defined properties fabricated directly on surfaces are ofgrowing interest. The fabrication of covalently boundnanostructures on non-metallic surfaces is very promising in termsof applications, but the lack of surface-assistance during theirsynthesis is still a challenge to achieve the fabrication oflarge-scale and defect-free nanostructures. We discuss thestate-of-the-art approaches recently developed in order to providecovalently bounded nanoarchitectures on passivated metallicsurfaces, semiconductors and insulators.</span&g

On-Surface Chemistry on Low-Reactive Surfaces

International audience<span style="font-size:11.0pt;line-height: 115%;font-family:&quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin; mso-fareast-font-family:&quot;Times New Roman&quot;;mso-fareast-theme-font:minor-fareast; mso-hansi-theme-font:minor-latin;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language: FR;mso-bidi-language:AR-SA"lang="EN-US" xml:lang="EN-US"&gtzero-dimensional (0D),mono-dimensional (1D), or two-dimensional (2D) nanostructures withwell-defined properties fabricated directly on surfaces are ofgrowing interest. The fabrication of covalently boundnanostructures on non-metallic surfaces is very promising in termsof applications, but the lack of surface-assistance during theirsynthesis is still a challenge to achieve the fabrication oflarge-scale and defect-free nanostructures. We discuss thestate-of-the-art approaches recently developed in order to providecovalently bounded nanoarchitectures on passivated metallicsurfaces, semiconductors and insulators.</span&g

On-surface fabrication of covalently bounded nanostructures monitored by HR-AFM at ambient conditions

International audienceThe fabrication of extended and compact nanostructures based on on-surface polymerisation has emerged a widespread research objective because these nanostructures can be integrated as nanocomponents in functional devices due to their electronic and photo physical proprieties. Most of onsurface reactions require catalytic role of the metal surface, which prevent the formation of extended nanostructures due to the presence of organo-metallic intermediate or on surface-defects which strongly hinder the formation of compact and well-ordered nanostructures. Here, we propose to use reactions promoted by thermal or light stimuli without any role of metal atom as “catalyst”. Herein we present onsurface [4 + 2] cycloaddition of 1,4-bis-(4’-vinyl)-2,5-bis(decyloxy)benzene (VINYL) molecules initiated by thermal polymerization and light-induced homo-polymerisation of 4-[(S,S)-2,3- Epoxyhexyloxy]phenyl-4-decyloxy)benzoate (EPOXY) molecules deposited on HOPG surface and monitored by high-resolution AFM at ambient conditions. After deposition of the two type of molecules on HOPG, we observed the formation of periodic, compact and large extended 2D supramolecular networks (see Fig.1a and 1.d). After UV-light exposure of the network constituted by EPOXY molecules or thermal annealing of those constituted by VINYL molecules, we observed a modification of the periodicity of the nanostructures. The difference in periodicity might be contribute to the formation of ether bridge between two adjacent molecules. We shall propose molecular adsorption models corresponding to network before and after polymerization. The chemical nature of resulting polymers is currently investigated

On-Surface Reactivity of Disubstituted-Bianthryl Molecules on Cu(111) and Au(111) Surfaces

International audienceOn-surface π-conjugated 1D polymers, like graphene nanoribbons, have emerged as a class of promising materials. On-surface chemical properties of 9,9′-bianthryl molecules are widely developed as they can be used as starting building blocks to provide graphene nanoribbons. Here, we propose to investigate the chemical behavior of 10,10′-disubstituted-9,9′-bianthryl molecules on Cu(111) and Au(111) surfaces by using scanning tunneling microscopy under ultra-high vacuum. We demonstrated that the balance between molecule-molecule interaction, molecule-substrate interaction, and molecular rearrangement, drastically alter the chemical properties of the adsorbed molecule by thermal annealing

Stable self-assembly of dipolar molecules on an Au(111) surface under UHV and an inert-atmosphere

International audienceThe growth of an extended supramolecular network using dipolar molecules as the building blocks is of great technological interest. We investigated the self-assembly of a dipolar molecule on an Au(111) surface. The formation of an extended two-dimensional network was demonstrated by scanning tunnelling microscopy under ultra-high vacuum and explained in terms of molecule–molecule interactions. This 2D-network is still stable under the pressure of one atmosphere of nitrogen, which demonstrated its interest for the development of submolecular-precisely polyfunctional smart surfaces

Etudes de réactions de photopolymérisation en surface de cristaux ioniques isolants par nc-AFM sous UHV

National audienceL’une des stratégies bien maitrisée et répandue en solution est fondée sur l’emploi d’un photo-initiateur qui absorbe fortement la lumière et se transforme en agent déclencheur d’une réaction radicalaire de polymérisation des monomères dispersés en solution. Notre travail s’inspire de ce comportement en solution pour tenter de le reproduire sur surface. La première étape consiste à trouver une combinaison d’un monomère et d’une surface permettant le développement d’une phase supramoléculaire métastable garantissant la diffusion des monomères pour réagir. La deuxième étape consiste à déposer sur la phase supramoléculaire précédemment créée un photo-initiateur capable de s’y adsorber et de déclencher la réaction de polymérisation photo-induite