Temperature-Dependent Constrained Diffusion of Micro-Confined Alkylimidazolium Chloride Ionic Liquids

Ionogels for flexible conductive substrates and their application in biosensing

Ionogels are highly conductive gels made from ionic liquids dispersed in a matrix made of organic or inorganic materials. Ionogels are known for high ionic conductivity, flexibility, high thermal and electrochemical stability. These characteristics make them suitable for sensing and biosensing applications. This review discusses about the two main constituents, ionic liquids and matrix, used to make ionogels and effect of these materials on the characteristics of ionogels. Here, the material properties like mechanical, electrochemical and stability are discussed for both polymer matrix and ionic liquid. We have briefly described about the fabrication methods like 3D printing, sol-gel, blade coating, spin coating, aerosol jet printing etc., used to make films or coating of these ionogels. The advantages and disadvantages of each method are also briefly summarized. Finally, the last section provides a few examples of application of flexible ionogels in areas like wearables, human-machine interface, electronic skin and detection of biological molecules.

Predicting Gaseous Solute Diffusion in Viscous Multivalent Ionic Liquid Solvents

Calculating solute diffusion in dense, viscous solvents can be particularly challenging in molecular dynamics simulations due to the long time scales involved. Here, a new scaling approach is developed for predicting solute diffusion based on analyses of CO2 and SO2 diffusion in two different multivalent ionic liquid solvents. Various scaling approaches are initially evaluated, including single and separate thermostats for the solute and solvent, as well as the application of the Arrhenius relationship and the Speedy-Angell power law. A very strong logarithmic correlation is established between the solvent-accessible surface area and solute diffusion. This relationship, reflecting Danckwerts' surface renewal theory and the Vrentas-Duda free volume model, presents a valuable method for estimating diffusion behavior from short simulation trajectories at elevated temperatures. The approach may be beneficial for enhancing predictive modeling in similar challenging systems and should be more broadly evaluated.

Does Viscosity Decoupling Guarantee Dynamic Heterogeneity? A Clue through an Excitation and Emission Wavelength-Dependent Time-Resolved Fluorescence Anisotropy Study

Traditionally, deviation from Stokes-Einstein-Debye (SED) relation in terms of viscosity dependence of medium dynamics, i.e., τ x ∝ ( η T ) p with p ≠ 1, is taken as a signature of dynamic heterogeneity. However, it does not guarantee medium heterogeneity, as the decoupling may also originate from the deviation of the basic assumption of SED. Here, we developed a method to find a stronger relation between viscosity decoupling (p ≠ 1) and dynamic heterogeneity in terms of rotational motion. Our approach exploited the fact that in heterogeneous media, a solvatochromic probe will be solvated to a different extent at different microdomains (subpopulations), and photoselection of these subpopulations can be achieved by excitation or emission wavelength-dependent measurements. We hypothesized that the dynamics of a homogeneous system might show viscosity decoupling, but the extent of decoupling at different excitations (or at different emissions) should not be different. On the other hand, in a heterogeneous medium, this extent of viscosity decoupling (p-value) should be different at different excitations (or at different emissions). As proof of concept, we investigated three versatile solvent media: squalane (viscous molecular liquid), 1-ethyle-3-methylimidazolium ethyl sulfate ionic liquid (IL), and [0.78 acetamide + 0.22 LiNO3] deep eutectic solvent (DES). We found that squalane is homogeneous, although it shows fractional viscosity dependence (p ≠ 1). Interestingly, mild heterogeneity in IL and significant heterogeneity in the DES were observed. Overall, we conclude that the difference in the p-value as a function of excitation (or emission) wavelength-dependent might be a superior way for the detection of dynamic heterogeneity.