Modifying Thermal Switchability of Liquid Crystalline Nanoparticles by Alkyl Ligands Variation

Abstract

By coating plasmonic nanoparticles (NPs) with thermally responsive liquid crystals (LCs) it is possible to prepare reversibly reconfigurable plasmonic nanomaterials with prospective applications in optoelectronic devices. However, simple and versatile methods to precisely tailor properties of liquid-crystalline nanoparticles (LC NPs) are still required. Here, we report a new method for tuning structural properties of assemblies of nanoparticles grafted with a mixture of promesogenic and alkyl thiols, by varying design of the latter. As a model system, we used Ag and Au nanoparticles that were coated with three-ring promesogenic molecules and dodecanethiol ligand. These LC NPs self-assemble into switchable lamellar (Ag NPs) or tetragonal (Au NPs) aggregates, as determined with small angle X-ray diffraction and transmission electron microscopy. Reconfigurable assemblies of Au NPs with different unit cell symmetry (orthorombic) are formed if hexadecanethiol and 1H,1H,2H,2H-perfluorodecanethiol were used in the place of dodecanethiol; in the case of Ag NPs the use of 11-hydroxyundecanethiol promotes formation of a lamellar structure as in the reference system, although with substantially broader range of thermal stability (140 vs. 90 °C). Our results underline the importance of alkyl ligand functionalities in determining structural properties of liquid-crystalline nanoparticles, and, more generally, broaden the scope of synthetic tools available for tailoring properties of reversibly reconfigurable plasmonic nanomaterials.

Shaping Liquid Crystals with Gold Nanoparticles: Helical Assemblies with Tunable and Hierarchical Structures Via Thin‐Film Cooperative Interactions

“…TEM images of the heat annealed Au1 sample (Figure 1f) revealed rows of NPs with an interrow spacing of ≈7.8 nm, which corresponds to the XRD-derived data. The observed temperature-dependent reconfigurability exhibited by Au1 is in agreement with our previous results on mesogenic NPs, [47,48,50] attests that L ligands are efficiently exposed at the Au1 nanocrystal surfaces (structural reconfigurability is driven by the change in the shape of the organic corona of the NPs) and translates to tunable plasmonic properties of thin films made of Au1 (Figure S4f, Supporting Information). [48][49][50] As described above, dropcasting and heat annealing of L-L or Au1 materials did not result in efficient formation of helical nanostructures.…”

Achieving Highly Stable, Reversibly Reconfigurable Plasmonic Nanocrystal Superlattices through the Use of Semifluorinated Surface Ligands

“…Thus, efficient interactions between fluorinated parts of ligands attached to the same and neighboring nanoparticles were assured. It is worth noting that in our previous research we used semilfuorinated thiols to modify reconfigurable behavior of nanoparticle assemblies; however, the fluorinated moieties were grafted onto the NPs surface directly; thus, interactions between these moieties from neighbor NPs were hindered and did not allow us to achieve efficient changes in reconfigurability.…”

“…Here, we rely on organic chemistry to design LC-ligand coated nanoparticles that form a reversibly reconfigurable plasmonic nanomaterial with long-term stability. The underlying philosophy for preparing the material was based on the concept of hydro- and oleo-phobic nature of fluorinated chains that provide access to materials with self-cleaning properties, recently gained much interest in responsive technologies at the micro/nano-scale. − By optimizing the LC ligand structure, we identified principles enabling us to achieve a material with a unique structural characteristic; namely it exhibits three long-range ordered phases with quick reconfiguration properties surpassing the current state-of-the-art. These structural properties translate to a relatively strong optical response.…”

Unconventional-Phase Crystalline Materials Constructed from Multiscale Building Blocks

“…Besides the commonly used organic hydrocarbon-based ligands, other types of ligands, including polymers, − liquid-crystalline molecules, − and biomolecules such as peptides , and DNA, can also be functionalized on the inorganic spherical nanoparticle surfaces, which contribute to the formation of nanoparticle superlattices with unconventional phases. For example, during the self-assembly of polystyrene-coated Au nanoparticles at the liquid–air interface, with increasing softness, defined as the stretched length of polymer chains over the radius of Au core, which was experimentally tuned by modifying the nanoparticle size and the polystyrene molecular weight, the phase of the resultant superlattices changes from hcp to bct to bcc .…”