Shape-Dependent Oriented Trapping and Scaffolding of Plasmonic Nanoparticles by Topological Defects for Self-Assembly of Colloidal Dimers in Liquid Crystals

Abstract

We demonstrate scaffolding of plasmonic nanoparticles by topological defects induced by colloidal microspheres to match their surface boundary conditions with a uniform far-field alignment in a liquid crystal host. Displacing energetically costly liquid crystal regions of reduced order, anisotropic nanoparticles with concave or convex shapes not only stably localize in defects but also self-orient with respect to the microsphere surface. Using laser tweezers, we manipulate the ensuing nanoparticlemicrosphere colloidal dimers, probing the strength of elastic binding and demonstrating self-assembly of hierarchical colloidal superstructures such as chains and arrays.Starting from the development of facile synthetic methods, gold nanoparticles have been the focus in the quest for understanding and exploiting their extraordinary optical properties arising from the localized surface plasmon resonance (SPR).

Optically and elastically assembled plasmonic nanoantennae for spatially resolved characterization of chemical composition in soft matter systems using surface enhanced spontaneous and stimulated Raman scattering

“…The RamanStokes signals from the sample were separated from the Rayleigh line using a long pass, edge filter before being sent to a spectrometer equipped with a grating of 600g/mm and finally recorded the spectra with an EMCCD detector. Laser trapping utilized 1064 nm laser light (guided to the microscope objective with a dichroic mirror) and could be based on a single stationary, focused laser beam and computer-controlled microscope stage or a holographic optical trapping setup (used in conjunction with CARS-PM and SRS-PM) described elsewhere 12 . Optical trapping of gold nanoparticles was characterized in dark field imaging mode using a darkfield condenser with NA = 1.2-1.4 (U-DCW) and an objective with NA = 0.6 (both from Olympus).…”

“…3 Short (20×40nm) gold nanorods (SR) with capping ligands polystyrene (PS) or methoxy poly(ethylene glycol) thiol (mPEG) and disc-shaped gold nanoparticles with sharp irregular edges called 'Nanobursts' (NB) 12,13 were obtained from Nanopartz Inc. The relatively poly-disperse NSOL-functionalized gold NB nanoparticles had average lateral size ~ 500 nm, as indicated by the TEM images shown in Fig 2(a).…”

Interfacial liquid-state surface-enhanced Raman spectroscopy

“…O riented assemblies of functional colloidal nanoparticles [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] are important for both fundamental science and technological applications. Such assemblies have been realized on two-dimensional (2D) solid substrates by utilizing evaporation-based convection 6,7 , capillary interaction 8 , electric fields 9,10 , substrate templating 11,12 and surface tailoring of nanoparticles 13,14 .…”

Self-assembly of colloidal particles in deformation landscapes of electrically driven layer undulations in cholesteric liquid crystals

“…We show that layer undulations also impinge on the dynamics of magnetically controlled superparamagnetic microparticles, enabling not only a robust control of equilibrium state patterning of particles but also nonequilibrium kinetic processes involving them. These findings are discussed from the standpoint of designing reconfigurable colloidal composites with potential applications in diffraction optics [43,45], nanophotonics [19], electro-optics [1], and other fields of science and engineering.…”