Probing the Ire–Nc–I phase transitions in a lyotropic liquid crystal by the surface plasmon resonance of embedded gold nanoparticles

Abstract

ABSTRACTThe surface plasmon resonance of noble metal nanoparticles depends on properties of the nanoparticles and of the surrounding medium, which make it a suitable probe of the local ordering of anisotropic media. Besides that, no much attention was paid to the possibility of using the surface plasmon resonance as probe of phase transitions in liquid crystals. In this work, we have used the surface plasmon resonance of rather spherical Au nanoparticles of nm for studying the phase transitions of a lyotropic liquid crystal of potassium laurate, 1-decanol and water that exhibits the phase sequence IRE–NC–I on rising temperature. The wavelength of the surface plasmon resonance is blue-shifted sharply at the IRENC transition, remaining almost constant at the NCI transition. The behaviour at the low-temperature transition can be assigned to a change in the shape anisotropy of the micelles. On the contrary, at the higher temperature transition, the local environment of the nanoparticles remains unmodified.