Nanocomposites and nanomaterials
Photo- and Thermoswitchability of plasmonic gold nanoparticles
Tomczyk E.1, Wójcik M.1
1 University of Warsaw, Faculty of Chemistry, Pasteura 1 Street, 02-093 Warsaw, Poland. 
E-mail: etomczyk@chem.uw.edu.pl
     The main goal of our research is to obtain first material made of liquid-crystalline nanoparticles exhibiting simultaneously UV-light and temperature responsive surface plasmon resonance in a condensed state.
     In order to obtain the material we grafted spherical gold nanoparticles with diameter of about 4 nm with two types of organic ligands: promesogenic, and azobenzene derivative. The former ligand is responsible for inducing rich polymorphism of  liquid crystal phases (reconfigurability of nanoparticle assemblies) while the latter endows nanoparticles with photoresponsive properties.
     What is unique, in comparison to previously described switchable nanoparticles assemblies, we show that nanoparticles covered with a mixture of these ligands assemble into long-range ordered structures which exhibit novel type of dual-responsivity. Structure and plasmonic properties of the assemblies can be controlled by temperature changes as well as by UV-light irradiation (Figure 1). Such dynamic, soft materials made of metallic nanoparticles and adaptable organic part constituate a huge advance in the study of dynamic and fast-reversible nanomaterials.
     Composition of obtained materials was confirmed using XPS and TGA methods, structural switchability was studied using temperature dependent SAXRD and TEM measurements, while changes of optical properties were determined using UV-VIS spectroscopy.

Figure 1. Schematic representation of possible organization states of the system and transitions between them.