Nanoparticle-based hollow microstructures formed by two-stage nematic nucleation and phase separation

Nature Communications
Sheida T RiahinasabLinda S Hirst

Abstract

Rapid bulk assembly of nanoparticles into microstructures is challenging, but highly desirable for applications in controlled release, catalysis, and sensing. We report a method to form hollow microstructures via a two-stage nematic nucleation process, generating size-tunable closed-cell foams, spherical shells, and tubular networks composed of closely packed nanoparticles. Mesogen-modified nanoparticles are dispersed in liquid crystal above the nematic-isotropic transition temperature (TNI). On cooling through TNI, nanoparticles first segregate into shrinking isotropic domains where they locally depress the transition temperature. On further cooling, nematic domains nucleate inside the nanoparticle-rich isotropic domains, driving formation of hollow nanoparticle assemblies. Structural differentiation is controlled by nanoparticle density and cooling rate. Cahn-Hilliard simulations of phase separation in liquid crystal demonstrate qualitatively that partitioning of nanoparticles into isolated domains is strongly affected by cooling rate, supporting experimental observations that cooling rate controls aggregate size. Microscopy suggests the number and size of internal voids is controlled by second-stage nucleation.

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Citations

Jun 26, 2021·Microscopy and Microanalysis : the Official Journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada·Kamil SobczakMikołaj Donten
Jul 30, 2021·Soft Matter·Devika Gireesan SudhaLinda S Hirst

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Methods Mentioned

BETA
nuclear magnetic resonance
fluorescence microscopy
fluorescence imaging
column chromatography

Software Mentioned

ImageJ
Fiji

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