Atomic Scale Modelling of Two-Dimensional Molecular Self-Assembly on a Passivated Si Surface

International audienceThe self-assembly of two-dimensional (2D) molecular structures on a solid surface relies on the subtle balance between non covalent intermolecular and molecule-surface forces. The energetics of 2D molecular lattices forming different patterns on a passivated semiconductor surface are here investigated by a combination of atomistic simulation methods. Density-functional theory provides structure and charges of the molecules, while metadynamics with empirical forces provides a best guess for the lowest-energy adsorption sites of single molecules and dimers. Subsequently, molecular dynamics simulations of extended molecular assemblies with empirical forces yield the most favorable lattice structures at finite temperature and pressure.The theoretical results are in good agreement with scanning tunneling microscopy observations of self-assembled molecular monolayers on a B-doped Si(111) surface, thus allowing to rationalize the competition of long-range dispersion forces between the molecules and the surface. Such a result demonstrates the interest of this predictive approach for further progress in supramolecular chemistry on semiconductor surface

Photochemistry highlights on-surface synthesis

International audienceOn-surface chemistry is promising way in order 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. The fabrication of these nanostructures was mainly obtained in ultrahigh vacuum (UHV) environment on single-crystal surfaces, i. e. noble metal surfaces, by thermal annealing as stimulus to provoke the polymerisation with a "catalytic" role of the surfaces 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 photoinduced 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

Droplet ejector using Surface Acoustic Waves.

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A love-wave sensor for direct detection of biofunctionalized nanoparticles

In this work, we have designed and manufactured Love wave sensors equipped with a liquid cell for the detection of bio-functionalized nano-particules in water. Measurements using these devices are based on the determination of velocity and propagation loss changes of a guided acoustic shear wave generated by Inter-Digital Transducers (IDTs) patterned on a (YX1t)/36 degrees/90 degrees cut of quartz and passivated by a silica overlay. The so-called Love mode acoustic wave sensors are known to he compatible with operation in liquid medium but requires and adapted fluidic packaging. The SU-8-based liquid cell is patterned atop the SiO2 guiding layer. We then describe the use of these sensors for the time resolved identification of the presence of nanoparticles in suspension. Silane surface chemistry for non-selective detection of most bio-functionalized nanoparticles health hazards is demonstrated by analyzing the gravimetrie signal associated with the binding of avidin-functionalized gold nanoparticles

A stable room-temperature molecular assembly of zwitterionic organic dipoles guided by a Si(111)-7 x 7 template effect

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A stable room-temperature molecular assembly of zwitterionic organic dipoles guided by a Si(111)-7 x 7 template effect

International audienc