Sylvain Clair

Single Layer of Polymeric Fe-Phthalocyanine: An Organometallic Sheet on Metal and Thin Insulating Film

Supramolecular chemistry on a surface has produced a large variety of atomically controlled systems, but practical applications are seriously restricted by the use of weakly cohesive non-covalent bonds and by the confinement to a metal surface. Here we report on the formation of a well-ordered organometallic sheet consisting of two-dimensional polymeric phthalocyanine. Remarkably, the growth demonstrated on a metal surface can be extended onto a thin insulating film. We thus expect the intrinsic properties to be preserved, and the system should be easily transferable to real devices.

Improving biocompatibility of implantable metals by nanoscale modification of surfaces: an overview of strategies, fabrication methods, and challenges.

The human body is an intricate biochemical-mechanical system, with an exceedingly precise hierarchical organization in which all components work together in harmony across a wide range of dimensions. Many fundamental biological processes take place at surfaces and interfaces (e.g., cell-matrix interactions), and these occur on the nanoscale. For this reason, current health-related research is actively following a biomimetic approach in learning how to create new biocompatible materials with nanostructured features. The ultimate aim is to reproduce and enhance the natural nanoscale elements present in the human body and to thereby develop new materials with improved biological activities. Progress in this area requires a multidisciplinary effort at the interface of biology, physics, and chemistry. In this Review, the major techniques that have been adopted to yield novel nanostructured versions of familiar biomaterials, focusing particularly on metals, are presented and the way in which nanometric surface cues can beneficially guide biological processes, exerting influence on cellular behavior, is illustrated.

Self-assembled monolayer of alkanephosphoric acid on nanotextured Ti

Surface modification of titanium and its alloys is of great importance for their practical application as biomedical implants. We have studied and compared assembly of dodecylphosphoric acid on commercial polished and on nanostructured titanium disks. The latter were produced by chemical etching that created nanoscale pits of typical size of about 20 nm. Enhanced hydrophobicity and high molecular density were obtained after functionalization of the nanotextured substrate. Aging tests showed a lifetime of the organic films of about one month in phosphate buffer. The samples were characterized by means of infrared spectroscopy, contact angle measurements, ellipsometry, and atomic force and scanning tunneling microscopies.

Tip- or electron beam-induced surface polymerization

Control on the formation of a two-dimensional polymer could be achieved in two different ways. Manipulation with the tip of a scanning tunneling microscope allowed for assigning the localization of the polymerization reaction. Additionally, electron irradiation could accelerate greatly the reaction kinetics.

Magnetic Coupling and Single-Ion Anisotropy in Surface-Supported Mn-Based Metal–Organic Networks

The electronic and magnetic properties of Mn coordinated to 1,2,4,5-tetracyanobenzene (TCNB) in Mn–TCNB two-dimensional metal–ligand networks have been investigated by combining scanning tunneling microscopy and X-ray magnetic circular dichroism (XMCD) performed at low temperature (3 K). When formed on Au(111) and Ag(111) substrates, the Mn–TCNB networks display similar geometric structures. Magnetization curves reveal ferromagnetic coupling of the Mn sites with similar single-ion anisotropy energies but different coupling constants. Low-temperature XMCD spectra show that the local environment of the Mn centers differs appreciably for the two substrates. Multiplet structure calculations were used to derive the corresponding ligand field parameters, confirming an in-plane uniaxial anisotropy. The observed interatomic coupling is discussed in terms of superexchange as well as substrate-mediated magnetic interactions.

Robust Supramolecular Network on Ag(111): Hydrogen-Bond Enhancement through Partial Alcohol Dehydrogenation

Alcohol oxidation and self-assembly: the in situ oxidation of hydroxyl functional groups to quinone groups promotes the formation of enhanced hydrogen bonds and allows reorganization of the resulting supramolecular self-assemblies, which evolve from a weakly bound dense phase to a strongly bound nanoporous open structure (see picture).

Side functionalization of diboronic acid precursors for covalent organic frameworks

A series of substituted 1,4-benzenediboronic acids (BDBA) was synthesized and their thermal properties investigated. Two diboronic acids were studied as building-blocks for covalent organic framework (COF) formation, namely 2,5-dimethoxy-1,4-benzenediboronic acid and 2-nitro-1,4-benzeneboronic acid. Interestingly, substitution of the BDBA core caused a dramatic decrease of the polymerization temperature leading to the formation of a less organized structure.

Substrate-induced array of quantum dots in a single-walled carbon nanotube.

Single-walled carbon nanotubes are model one-dimensional structures. They can also be made into zero-dimensional structures; quantum wells can be created in nanotubes by inserting metallofullerenes, by mechanical cutting or by the application of mechanical strain. Here, we report that quantum dot arrays can be produced inside nanotubes simply by causing a misalignment between the nanotube and the <100> direction of a supporting silver substrate. This method does not require chemical or physical treatment of either the substrate or the nanotube. A short quantum dot confinement length of 6 nm results in large energy splittings.

Two‐Dimensional Polymer as a Mask for Surface Nanopatterning

NaCl islands are used as a sacrificial layer to selectively deposit a boronic acid based two-dimensional polymer. The nanostructured polymer layer can be used as a negative mask to create Fe islands in a nanolithography mimicking process.

Steric and electronic selectivity in the synthesis of Fe-1,2,4,5-tetracyanobenzene (TCNB) complexes on Au(111): From topological confinement to bond formation

A study of the surface assisted self-assembly of 1,2,4,5-tetracyanobenzene (TCNB) acceptor molecules and Fe atoms on an Au(111) surface is presented. While conditions to get the two-dimensional arrays of stable Fe(TCNB)4 complexes are clearly identified, ultrahigh vacuum scanning tunneling microscopy and spectroscopy (STM/STS) coupled with first-principles calculations reveals that situations may occur where Fe and TCNB survive on the surface (as Fe-4TCNB entities) at a higher density than the original molecular monolayer without forming coordination bonds with each other. It is found that the square planar coordination of the Fe(TCNB)4 monomer complexes cannot fully develop in the presence of lateral strain due to growth-induced confinement. A phenomenon similar to steric hindrance involving a strongly modified chirality with a Fe-N-C bond angle of 120° compared to the 180° for the stable complex may then explain why the Fe atom keeps its metallic bond with the surface. The competition between steric and electronic effects, not reported before, may arise elsewhere in surface chemistry involved in the synthesis of new and potentially useful organic nanomaterials.