Optical “Blinking” Triggered by Collisions of Single Supramolecular Assemblies of Amphiphilic Molecules with Interfaces of Liquid Crystals

Abstract

We report that incubation of aqueous dispersions of supramolecular assemblies formed by synthetic alkyl triazole-based amphiphiles against interfaces of thermotropic liquid crystals (LCs; 4cyano-4′-pentylbiphenyl) triggers spatially localized (micrometerscale) and transient (subsecond) flashes of light to be transmitted through the LC. Analysis of the spatiotemporal response of the LC supports our proposal that each optical "blinking" event results from collision of a single supramolecular assembly with the LC interface. Particle tracking at the LC interface confirmed that collision and subsequent spreading of amphiphiles at the interface generates a surface pressure-driven interfacial flow (Marangoni flow) that causes transient reorientation of LC and generation of a bright optical flash between crossed polarizers. We also found that dispersions of phospholipid vesicles cause "blinks". When using vesicles formed from 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), we measured the frequency of blinking to decrease proportionally with the number density of vesicles in the aqueous phase, consistent with single vesicle events, with the lifetime of each blink dependent on vesicle size (800 ± 80 nm to 150 ± 30 nm). For 100 μM of DLPC, we measured vesicles with a diameter of 940 ± 290 nm to generate 47 ± 9 blinks min −1 mm −2 , revealing that the fraction of vesicle collisions resulting in fusion with the LC interface is ∼10 −3 . Overall, the results in this paper unmask new nonequilibrium behaviors of amphiphiles at LC interfaces, and provide fresh approaches for exploring the dynamic interactions of supramolecular assemblies of amphiphiles with fluid interfaces at the single-event level.

Optically Anisotropic Topical Hemostatic Coacervate for Naked‐Eye Identification of Blood Coagulation

“…In general, intermolecular binding of LCs with surfactants or other ligand molecules can cause optical configurational changes in LC. [ 22 ] Thus, the TA shell might lead to configurational changes in the CLC core. Interestingly, although most of the CLCE alone had nematic configurations with irregular orientation (Figure 2f, top), the addition of TA increased the number of radial configurations of CLC, which have four‐leaf clover shaped orientation (Figure 2f, bottom), from 12.9 ± 1.1% (without TA) to 28.6 ± 1.8% (30 m m of TA) (Figure 2g, red bars); in contrast, the nematic configuration of CLC decreased to 27.5 ± 0.9% (46.2 ± 3.1% for CLCE alone) (Figure 2g, black bars).…”

Areas of opportunity related to design of chemical and biological sensors based on liquid crystals

“…Whereas the majority of past efforts to develop biomolecular sensors at LC-aqueous interfaces have focused on driving the LC between two equilibrium states (with or without the target), recent studies highlight the opportunity to create LC sensors that operate beyond equilibrium. To illustrate the approach, we describe recent observations of non-equilibrium behaviours of LC interfaces that are incubated against aqueous dispersions of amphiphilic assemblies [53]. In these studies, the LCs (e.g.…”

“…The complex dynamic responses of LC to non-equilibrium states offer a range of pathways towards adaptive and self-regulating chemical systems, where the responses to multiple stimuli are computed by the LC thus giving rise to a level of autonomy and function that is increasingly similar to living biological systems (e.g. function of a biological membrane) [53,57].…”

Controlling Liquid Crystal Configuration and Phase Using Multiple Molecular Triggers

“…Furthermore, their optical properties are incredibly useful for displays and other read-outs of their state. Recently, liquid crystals have been used as a model system that is responsive to the molecular nature of the environment [ 12 , 13 , 14 , 15 , 16 ]. The self-organization and long-range elasticity enable liquid crystal systems to sense environmental fluctuations and react accordingly—all without a brain or a central communication network.…”