Understanding directed assembly of concentrated nanoparticles at energetically heterogeneous interfaces of cholesteric liquid crystal droplets

Nanoparticle-Assisted Liquid Crystal Droplet Sensors Enable Analysis of Low-Concentration Species in Aqueous Medium

“…One candidate explanation of the change in the configuration distribution of the droplets upon dilution, as presented in Figure , is also the reorganization of the nanoparticles at the interfaces of the LC droplets (including the desorption of the nanoparticles from the interface or separation of the nanoparticles at the interface upon dilution of the dye). First, as observed in our past studies , and consistent with the experiments in Figure , we do not observe desorption of the nanoparticles from the droplet interface upon dilution. This is consistent with the significant adsorption energy of the ∼100 nm particles that can be estimated as ∼10 5 k B T .…”

“…First, as observed in our past studies 56,58 and consistent with the experiments in Figure 3, we do not observe desorption of the nanoparticles from the droplet interface upon dilution. This is consistent with the significant adsorption energy of the ∼100 nm particles that can be estimated as ∼10 5 k B T. 66 Second, we observe the −COOH/DMOAP silica nanoparticles to form dense aggregates at the LC−water interfaces with and without the presence of the dye in the suspension medium (Figure 3 and refs 56,58). Dilution of the aqueous medium would then not result in the separation of the interfacially adsorbed nanoparticles from each other.…”

“…During the dilution steps, the overall concentrations of the nanoparticles were also decreased; however, as we showed in Figure 2 (and also in past studies), the adsorbed nanoparticles do not desorb from the droplet interfaces during such modifications. 56,58 Thus, the configuration distributions we measured dominantly resulted from the interactions of LCs with the same nanoparticles adsorbed at the interfaces of the droplets. The configuration distributions of the droplets in these samples were collected every 30 min and reported in Figure 4.…”

“…Nanoparticles are used in various fields, such as food, biomedicine, agriculture, and sensors. − Their large surface area and the significant knowledge on their surface modifications (with e.g., DNA aptamers, antibodies and ligands) to increase their chemical affinity toward target species make them promising candidates to add more flexibility to the sensing capabilities of LC-based platforms. − The interactions of the LC interfaces with colloidal species have been studied in the past, which showed that the interactions of nanoparticles at the interfaces are influenced significantly by the specific anchoring conditions at colloid interfaces and the energetical landscape of the underlying elastic interaction. − Recently, we showed that the droplets of the nematic LCs respond to the adsorption of the nanoparticles from the aqueous phases, and the response is dependent on the concentration of the nanoparticle and the chemistry and physicochemical properties of their interfaces . Given these past studies, we seek to develop nanoparticles with chemically modified interfaces that can be employed to facilitate the interactions of the nonamphiphilic solutes present in the aqueous phases, which may not readily cause a direct ordering transition at the interfaces that LCs make with aqueous phases.…”