Nanoplasmonics and surface enhanced spectroscopy:
Long-range ordered binary systems of plasmonic nanoparticles with temperature-dependent structure and optical properties
Piotr Szustakiewicz1, Wiktor Lewandowski.1
1University of Warsaw, Deprtment of Chemistry
Ludwika Pasteura 1,
02-093 Warsaw, Poland. 
E-mail: p.szustakiewicz@chem.uw.edu.pl

Localized surface plasmon resonance is one of the most interesting properties exhibited by metallic nanoparticles, allowing applications in various fields like medicine, optics or catalysis. By placing nanoparticles in distances supporting occurance of plasmon coupling, we are able to control the plasmonic response of the entire systems. Based on kinetics of these kinds of systems, we can divide them into two groups: static, which structure is fixed after the synthesis, and dynamic, where the structure changes under external stimuli, which makes them very attractive from the applicative stand. One possible way to obtain such dynamically switchable, plasmonic structures is to functionalize nanoparticles with thiol-ended liquid-crystalline (LC) ligands.
In our previous work [1-2], we presented a series of different LC ligands, which when combined with gold or silver nanoparticles formed systems with temperature-dependent structure. What is more, these structural changes were accompanied by the shift of plasmonic peak, confirming the optical properties switchability. Currently, we are exploring the idea of preparing systems with more than one type of LC-functionalized nanoparticles, e.g. two different sizes of nanoparticles in one system.
Using more than one type of nanoparticle allows us to expand current size limits of switchable, liquid crystal nanoparticles system when bigger NPs are used in system along with smaller NPs. This translates into better control over optical properties, as we can expect greater change in plasmonic response during the thermally induced structural change. These kind of properties are on high demand in areas like metamaterials, waveguiding and photonics.

1. 	Lewandowski, W.; Szustakiewicz, P.; Mieczkowski, J.; Pociecha, D. Reversible switching of structural and plasmonic properties of liquid-crystalline gold nanoparticle assemblies †. Nanoscale 2016, 8, 2656–2663.
2. 	Lewandowski, W.; Fruhnert, M.; Mieczkowski, J.; Rockstuhl, C.; Górecka, E. Dynamically self-assembled silver nanoparticles as a thermally tunable metamaterial. Nat. Commun. 2015, 6, 6590.