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

ABSTRACT

The 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 I_RE–N_C–I on rising temperature. The wavelength of the surface plasmon resonance is blue-shifted sharply at the I_REN_C transition, remaining almost constant at the N_CI 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.

GRAPHICAL ABSTRACT

KEYWORDS:

• plasmonic nanoparticle
• lyotropic liquid crystal
• phase transition

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work had the financial support of the Brazilian agencies CAPES, CNPq, Fundação Araucária and the Secretaria de Ciência, Tecnologia e Ensino Superior do Governo do Paraná, and of the National Institute of Science and Technology in Complex Fluids (INCT-FCx). V. M. Lenart also acknowledges fellowship from CAPES [Proc. n°2263-13-0].