  Monodisperse rod-like colloidal particles are known for spontaneously forming
both nematic and smectic liquid crystal phases, but their self-assembly was
typically exploited from the fundamental soft condensed matter physics
perspective. Here we demonstrate that depletion interactions, driven by
non-adsorbing polymers like dextran and surfactants, can be used to enrich
self-organization of photon-upconversion nanorods into orientationally ordered
nematic and smectic-like membrane colloidal superstructures. We study
thermodynamic phase diagrams and demonstrate polarization-dependent photon
upconversion exhibited by the ensuing composites, which arises from the
superposition of unique properties of the solid nanostructures and the
long-range ordering enabled by liquid crystalline self-organization. Finally,
we discuss how our method of utilizing self-assembly due to the steric and
electrostatic interactions, along with attractive depletion forces, can enable
technological uses of lyotropic colloidal liquid crystals and mesostructured
composite materials enabled by them, even when they are formed by anisotropic
nanoparticles with relatively small aspect ratios.
