We describe a simple and universal technique of controlled non-covalent assembly of metallic nanorods (NRs) using
self-assembled stacks of lyotropic chromonic molecules. Depending on the charge of the NRs, the chromonic stacks
assemble them either end-to-end or side-by-side through anisotropic attractive forces. The anisotropically aggregated
systems of NRs show pronounced changes in spectral properties as compared to those of individual NRs, with
longitudinal and transverse plasmon peaks shifting accordingly to the geometry of assembly. The length of chromonic
stacks is not fixed by covalent bonds and depends strongly on temperature, chromonic concentration, ionic content and
pH of the solution. As a result, all these parameters can be used to control the assembly of NRs through the control of
the linking agents. We also demonstrate that the process of NRs assembly can be quenched by adding a polyelectrolyte
to the solution of NRs and chromonic material. The NR assemblies arrested by the polyelectrolyte can be transferred
into a polymer film such as polyvinyl alcohol, preserving their structural and optical features.
Lyotropic chromonic liquid crystals (LCLCs) are formed by molecules with rigid polyaromatic cores and ionic groups
at the periphery that form aggregates while in water. Most of the LCLCs are not toxic to the biological cells and can be
used as an amplifying medium in real-time biosensors. The detector is based on the principle that the immune
aggregates growing in the LCLC bulk trigger the director distortions. Self-assembly of LCLC molecules into oriented
structures allows one to use them in various structured films. For example, layer-by-layer electrostatic deposition
produces monomolecular layers and stacks of layers of LCLC with long-range in-plane orientational order which sets
them apart from the standard Langmuir-Blodgett films. We demonstrate that divalent and multivalent salts as well as
acidic and basic materials that alter pH of the LCLC water solutions, are drastically modifying the phase diagrams of
LCLC, from shifting the phase transition temperatures by tens of degrees, to causing condensation of the LCLC
aggregates into more compact structures, such as birefringent bundles or formation of a columnar hexagonal phase from
the nematic phase.
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