(450e) Driven Assembly of Nanoparticles in Nematic Liquid Crystals | AIChE

(450e) Driven Assembly of Nanoparticles in Nematic Liquid Crystals


Abbott, N. L. - Presenter, University of Wisconsin-Madison
De Pablo, J.J - Presenter, University of Wisconsin-Madison

Nanoparticles are increasingly being used in optical sensors for chemicals and biomolecules [1]. Increased optical activity can be achieved by carefully controlling the size, shape and composition of the nanoparticles. Moreover, the binding affinities of the nanoparticles toward specific analytes can also be tailored via surface engineering [1,2]. Further increases in the sensitivity and selectivity of these assays can be achieved by the use of liquid crystals [3]. Analyte binding at the surface of the particles can perturb the local ordering of the liquid crystal, triggering the formation of inhomogeneous textures that can be communicated over several length scales, and thus be detected using a microscope and polarized light. The elastic distortions of the liquid crystal around the nanoparticles also give rise to long-range interparticle interactions, which can lead to spatial reorganization of the particles and changes in the collective optical properties of the system. By engineering the physical properties of the system, the way the particles assemble can also be controlled to obtain microemulsions and colloidal dispersions with improved physical properties [4]. These systems also have potential applications for development of new composite materials with improved physical properties.

Optimization of the applications mentioned above requires a theoretical formalism providing a link between macroscopic experimental measurements (collective optical properties) and events occurring at much smaller length scales (particle aggregation, liquid crystal reorganization and binding events at the surface of the particles). Due to the large disparity in relevant length scales, traditional atomistic and molecular simulation techniques are not suitable to study these systems. In this work, we perform numerical simulations of 3D systems of spherical colloids dispersed in a liquid crystal solvent, by adopting a hybrid strategy that includes particle-based modeling of the colloids but treats the liquid crystal as a continuous field. Such a hybrid strategy was used in the past in 2D simulations of similar systems [5]. The effect of relevant physical variables will be analyzed and discussed.

[1] N. L. Rosi and C. A. Mirkin, Chem. Rev. 105, 1547 (2005); C. J. Murphy, T. K. Sau, A. M. Gole, C. J. Orendorff, J. Gao, L. Gou, S. E. Hunyadi and T. Li, J. Phys. Chem. B 109, 13857 (2005); D. A. Schultz, Curr. Opin. Biotechnol. 14, 13 (2003).

[2] J. C. Love, L. A. Estroff, J. K. Kriebel, R. G. Nuzzo and G. M. Whitesides, Chem. Rev. 105, 1103 (2005); E. Katz and I. Willner, Angew. Chem. Int. Ed. 43, 6042 (2004).

[3] J. M. Brake, M. K. Daschner, Y. Y. Luk and N. L. Abbott, Science 302, 2094 (2003); R. R. Shah and N. L. Abbott, Science 293, 1296 (2001); V. K. Gupta, J. J. Skaife, T. B. Dubrovsky and N. L. Abbott, Science 279, 2077 (1998).

[4] J. C. Loudet, P. Barois, P. Auroy, P. Keller, H. Richard and P. Poulin, Langmuir 20, 11336 (2004); J. C. Loudet, P. Barois and P. Poulin, Nature (London) 407, 611 (2000); P. Poulin, H. Stark, T. C. Lubensky and D. A. Weitz, Science 275, 1770 (1997).

[5] R. Yamamoto, Y. Nakayama and K. Kim, J. Phys.: Condens. Matter 16, S1945 (2004); R. Yamamoto, Phys. Rev. Lett. 87, 075502 (2001).