Nanocomposites and Nanomaterials

Unusual odd-even effect in helical assemblies of metallic nanoparticles
Pawlak M.1
1 Faculty of Chemistry, University of Warsaw, ul. Pasteura 1, Warsaw, Poland. 
E-mail: mr.pawlak@student.uw.edu.pl

Functionalization of metallic nanoparticles (NPs) with organic ligands is a powerful tool for fabrication of complex plasmonic structures. For instance, NPs covered with liquid crystal like ligands can enhance formation of helical nanofilaments by liquid crystal (LC) molecules. When LC crystallizes, NPs assemble into a double helical structure by covering edges of the helical nanofilaments [1]. Such helical structures are especially interesting for applications in chiral optics, thus it is worth to deepen our knowledge of their formation.  
We report a surprising odd-even effect in helical assemblies of spherical, Au NPs and dimer liquid crystals. We noted that formation of helical nanofilaments is strongly correlated with the length of an alkyl linker in the central part of molecules. Surprisingly, we observed that helices decorated with NPs form only if the dimer has an even number of carbon atoms. That observation is in stark contrast to a commonly accepted model and observations made for purely organic materials [2]. These results highlight the importance of the formation of composite nanomaterials, and indicate that NPs can be used to control crystallization of organic matter. 

1.	Bagiński M. et al. Shaping Liquid Crystals with Gold Nanoparticles: Helical Assemblies with Tunable and Hierarchical Structures Via Thin-Film Cooperative Interactions // Adv Mat.-2020.-32.-1904581.
2.	Walba D. M. et al. On the Nature of the B4 Banana Phase:  Crystal or Not a Crystal?// Crystal Growth & Design.-2005.-5.-6. , -P. 2091–2099.