Liquid Crystal Films as Active Substrates for Nanoparticle Control

Journal Article · Mon Jun 21 00:00:00 EDT 2021 · ACS Applied Nano Materials

DOI:https://doi.org/10.1021/acsanm.1c00680· OSTI ID:1847421

Gharbi, Ines ^[1]; Palacio-Betancur, Viviana ^[2]; Ayeb, Habib ^[3]; Demaille, Dominique ^[4]; de Pablo, Juan J. ^[5]; Kamien, Randall D. ^[6]; Lacaze, Emmanuelle ^[4]

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1. Sorbonne Univ., Paris (France); Univ. de Tunis El Manar (Tunisie)
2. Univ. of Chicago, IL (United States)
3. Univ. de Tunis El Manar (Tunisie)
4. Sorbonne Univ., Paris (France)
5. Univ. of Chicago, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
6. Univ. of Pennsylvania, Philadelphia, PA (United States)

Organizing nanoparticles in a controlled way allows us to monitor their optical properties. It is particularly interesting to organize them on top of liquid crystal films to take advantage, in a second step, of the easy actuation of liquid crystals with external parameters such as temperature, electric fields, and so forth. We show that despite their fluidity, nematic and smectic films allow the formation of well-ordered hexagonal domains of gold spherical nanoparticles (AuNPs) at their surface, but we also show that both nematic films and AuNP domains impact each other. Using optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectrophotometry, we compare nematic, polymer-stabilized nematic, and smectic films with AuNP domains made of NPs of diameter 6 nm. On the liquid crystal films, depressions are revealed below the AuNP domains, whereas the AuNP domains appear well-organized but with a hexagonal period shortened with respect to AuNP monolayers formed on hard substrates. We interpret these features by the anchoring tilt imposed by the AuNP domains on the liquid crystal molecules. The smectic-A layers characteristic of the nematic surface transform into smecticC layers, which induce the formation of depression. Here, the energy penalty associated with the local smectic-A/smectic-C transition induces the shortening of the AuNP domain period in order to decrease the AuNP domain surface. The observed large depth of the polymer-stabilized nematic depressions below AuNP domains may be explained either by an increased size of the polymer-stabilized smectic layers close to the surface or by an increased number of polymer-stabilized smectic liquid crystal smectic layers close to the surface with respect to pure nematic films.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); Simons Foundation
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1847421
• Journal Information: ACS Applied Nano Materials, Journal Name: ACS Applied Nano Materials Journal Issue: 7 Vol. 4; ISSN 2574-0970
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AFM
SEM
gold nanoparticle
layers
liquid crystal
metal nanoparticles
nanoparticle control
optical properties
plasmon extinction
polymer films
spectrophotometry