Electrically and Optically Tunable Plasmonic Guest–Host Liquid Crystals with Long-Range Ordered Nanoparticles

Abstract

Practical guest-host devices in which dichroic dye molecules follow electrical switching of a liquid crystal host remain elusive for decades despite promising efficient displays and emergent applications such as smart windows. This is mainly because of poor stability, surface precipitation, and limited means for property engineering of the dyes. To overcome these challenges, we develop plasmonic metal nanoparticle analogues of dichroic guest-host liquid crystals. Nematic dispersions of aligned anisotropic gold nanoparticles are obtained by polymer passivation of their surfaces to impose weak tangential boundary conditions for orientation of anisotropic host molecules. Control of the ensuing surface interactions leads to long-range ordered colloidal dispersions, allowing for collective optical and electrical switching of rod- and platelet-like nanoparticles. This facile control of mesostructured plasmonic medium's optical properties in visible and infrared spectral ranges is of interest for many applications.

Stability and Orientational Order of Gold Nanorods in Nematic Suspensions: A Small Angle X-ray Scattering Study

“…The orientational order parameter for the GNR(5400) is similar to the values reported from measurements based on dichroic ratios for similar size GNR also with 5kDa PEG [20]. A calculation based on weak tangential anchoring energy [20] has rationalized the measured order parameters from gold nanoparticles with different aspect ratios, but with the same 5kDa PEG stabilizer, using a single polar anchoring coefficient.…”

Repulsion–attraction switching of nematic colloids formed by liquid crystal dispersions of polygonal prisms

“…[5][6][7][8] LC colloids often manifest unusual elastic interactions, which cannot be realized in colloidal systems with isotropic fluid hosts. 1 Colloidal particles dispersed in LCs tend to deform an otherwise homogeneous director field 9 n(r) around them, depending on their shape and size, 10-17 topology 18,19 and surface anchoring boundary conditions.…”

Liquid Crystal Colloids

“…Other colloidal shapes studied recently include pyramids, spirals, shape-morphing elastomeric rods, gourd-shaped dimers, particles with nanoscale surface roughness, and so on (98)(99)(100)(101)(102)(103)(104)(105)(106)(107)(108)(109)(110)(111)(112)(113), in all cases demonstrating that the geometric shape pre-defines locations of topological defects and colloidal interactions. Facile control of nanoparticle and molecular organization and the ensuing composite properties can be achieved by applying electric, magnetic, and optical fields (80). In addition to the equilibrium structures and various crystal or LC colloidal phases, future designs of composite material behavior may also involve various types of LC colloidal dynamics (145-150), though 21 additional studies are still needed to make this possible.…”