Structural and Dynamic Properties of Hydrophobic Eutectic Solvents Based on Menthol and Fatty Acids: a Molecular Dynamics Simulation Study

The structural and dynamical properties of the binary mixture of Menthol (MEN) and Fatty acids (FAs) were investigated using molecular dynamics simulations. We focused on the relationship between the structural and dynamical properties of the eutectic mixtures of MEN and FAs with different molar percentages of FAs. Structural properties of the eutectic mixtures were characterized by calculating the combined distribution functions(CDFs), the radial distribution functions (RDFs), and the angular distribution functions (ADFs), and the Hydrogen bonding network between species and Spatial distribution functions (SDF). Further interaction between menthol and Caprylic acid molecules was confirmed by the results of these analyzes. Also, the transport properties of the mixtures were investigated by using the mean square displacement (MSD) of the centers of mass of the species, self-diffusion coefficients and vector reorientation dynamics (VRD) of bonds. The simulation results indicated that intermolecular interactions have a significant effect on the dynamic properties of species.

On the Mutual Relationships between Molecular Probe Mobility and Free Volume and Polymer Dynamics in Organic Glass Formers: cis-1,4-poly(isoprene)

We report on the reorientation dynamics of small spin probe 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) in cis-1,4-poly(isoprene) (cis-1,4-PIP10k) from electron spin resonance (ESR) and the free volume of cis-1,4-PIP10k from positron annihilation lifetime spectroscopy (PALS) in relation to the high-frequency relaxations of cis-1,4-PIP10k using light scattering (LS) as well as to the slow and fast processes from broadband dielectric spectroscopy (BDS) and neutron scattering (NS). The hyperfine coupling constant, 2Azz′(T), and the correlation times, τc(T), of cis-1,4-PIP10k/TEMPO system as a function of temperature exhibit several regions of the distinct spin probe TEMPO dynamics over a wide temperature range from 100 K up to 350 K. The characteristic ESR temperatures of changes in the spin probe dynamics in cis-1,4-PIP10k/TEMPO system are closely related to the characteristic PALS ones reflecting changes in the free volume expansion from PALS measurement. Finally, the time scales of the slow and fast dynamics of TEMPO in cis-1,4-PIP10k are compared with all of the six known slow and fast relaxation modes from BDS, LS and NS techniques with the aim to discuss the controlling factors of the spin probe reorientation mobility in polymer, oligomer and small molecular organic glass-formers.

Water reorientation dynamics in colloidal water–oil emulsions

Polarization resolved pump–probe infrared spectroscopy of colloidal oil-in-water emulsions demonstrates that the total surface area of oil droplets is independent of the average droplet size, indicating that the oil droplets are strongly corrugated.

Motion Restricted by Hydration Shell: A Self-Reporting System for Visualizing Electrolyte Interactions

<div><div><div><p>Electrolyte interaction is of pivotal importance for chemical, biochemical, and environmental processes, including cellular signal transduction, DNA attraction, and protein dynamics. Although its investigation has been at the focus of extensive research, direct visualization of electrolyte interaction at the molecular level is exceptionally challenging. Here, we report a highly sensitive and readily-accessible technique to visualize the electrolyte interactions in water through molecular design and fluorescence spectroscopy. Two water-soluble luminogens with either cationic or anionic groups are designed as electrolyte models. The hydration shell of isolated luminogens is able to restrict their intramolecular motion, which enhances the emission. Consequently, the occurred electrolyte interactions can be optically detected since they affect the reorientation dynamics of water molecules in the hydration shell and vary the restriction strength on the intramolecular motion of the luminogens. Moreover, this technology allows us to reveal how electrolyte interaction affects the internal motion of an electrolyte within its hydration shell, which has rarely been achieved through experimental approaches.</p></div></div></div>

Motion Restricted by Hydration Shell: A Self-Reporting System for Visualizing Electrolyte Interactions

<div><div><div><p>Electrolyte interaction is of pivotal importance for chemical, biochemical, and environmental processes, including cellular signal transduction, DNA attraction, and protein dynamics. Although its investigation has been at the focus of extensive research, direct visualization of electrolyte interaction at the molecular level is exceptionally challenging. Here, we report a highly sensitive and readily-accessible technique to visualize the electrolyte interactions in water through molecular design and fluorescence spectroscopy. Two water-soluble luminogens with either cationic or anionic groups are designed as electrolyte models. The hydration shell of isolated luminogens is able to restrict their intramolecular motion, which enhances the emission. Consequently, the occurred electrolyte interactions can be optically detected since they affect the reorientation dynamics of water molecules in the hydration shell and vary the restriction strength on the intramolecular motion of the luminogens. Moreover, this technology allows us to reveal how electrolyte interaction affects the internal motion of an electrolyte within its hydration shell, which has rarely been achieved through experimental approaches.</p></div></div></div>

A new ultrafast energy funneling material harvests three times more diffusive solar energy for GaInP photovoltaics

There is no theoretical limit in using molecular networks to harvest diffusive sun photons on large areas and funnel them onto much smaller areas of highly efficient but also precious energy-converting materials. The most effective concept reported so far is based on a pool of randomly oriented, light-harvesting donor molecules that funnel all excitation quanta by ultrafast energy transfer to individual light-redirecting acceptor molecules oriented parallel to the energy converters. However, the best practical light-harvesting system could only be discovered by empirical screening of molecules that either align or not within stretched polymers and the maximum absorption wavelength of the empirical system was far away from the solar maximum. No molecular property was known explaining why certain molecules would align very effectively whereas similar molecules did not. Here, we first explore what molecular properties are responsible for a molecule to be aligned. We found a parameter derived directly from the molecular structure with a high predictive power for the alignability. In addition, we found a set of ultrafast funneling molecules that harvest three times more energy in the solar’s spectrum peak for GaInP photovoltaics. A detailed study on the ultrafast dipole moment reorientation dynamics demonstrates that refocusing of the diffusive light is based on ∼15-ps initial dipole moment depolarization followed by ∼50-ps repolarization into desired directions. This provides a detailed understanding of the molecular depolarization/repolarization processes responsible for refocusing diffusively scattered photons without violating the second law of thermodynamics.