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| Accueil>La recherche>nMat>cristaux liquides>ncs | ||||||||||||||
NANOPARTICLE SELF-ASSEMBLY
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Research
area |
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| Patterning nanoobjects is an exciting interdisciplinary
research area in current material sciences due to new optical and
optoelectronic properties and the need to miniaturize electronic
components. |
Many techniques have been developed for assembling
nanoparticles into two- and three-dimensional arrays. Most of studies
involving liquid crystals as templates have dealt with colloidal
particles and nematic and smectic phases. |
Our
contribution |
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| We have provided evidence of a long range ordering of nanoparticle assemblies which adopt the helical configuration of the cholesteric liquid crystalline phase. Due to glass forming cholesterics, the investigation of nanostructures is made possible by transmission electron microscopy. The platinum nanoparticles form periodic ribbons which mimic the well-known fingerprint cholesteric texture. The nanoparticles do not decorate the cholesteric texture but create a novel helical structure with a larger helical pitch. By varying the molar fraction of cholesterol containing mesogen in the liquid crystal host, we have shown that the distance between the ribbons is directly correlated to the pitch. |
Therefore this inherent length scale becomes
a simple control parameter to tune the structuring of nanoparticles.
Investigations of cross-sections show how the particles are arranged
in the volume; a selective segregation proceeds at the periphery
of the film and specific patterns are localized close to the film-air
interface. These results demonstrate the modularity of such an
assembly process which provides a versatile route to new materials
systems. |
 Structuring of metallic nanoparticles by mimicry of a cholesteric liquid crystal (TEM micrograph): fingerprint-like patterns of nanoparticles when embedded in a glassy cholesteric. The distance between lines is correlated to the molecular chirality (and the helical pitch) of the LC. |
Disclination-like pattern in the fingerprint texture made up of solid particles (TEM micrograph). |
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