An article exploring the specific-ion effects on local electric fields in aqueous electrolyte solutions is published at JPCB.

A collaborative, multi-perspective investigation gives rise to the molecular level detailed picture of ions’ influence on the vibrational stark effect of various molecular probes. Salts containing well-hydrated cations like Mg2+ or Li+ led to the most notable Stark shift for the carbonyl group, while poorly hydrated cations (Cs+) had the greatest impact on the nitrile groups.

An unforeseen feature of water as a biological fluid is demonstrated. Hyaluronan, a highly hydrated natural biopolymer, has an impact on the structure of water molecules in its extended hydration shells.

In this work, we explored the extended hydration shell structure of hyaluronan in aqueous solutions . Hyaluronan is a highly hydrated biopolymer found in the extracelular environment, such as synovial fluid between joints. Angle-resolved fs-ESHS measurements and nonlinear optical modeling show that hyaluronan behaves like a flexible chain surrounded by extended shells of orientationally correlated water. The spatial extent of the hydration shell is determined via temperature-dependent measurements and can reach up to 475 nm. (read more…)

Cationic Hofmeister series on the ion – macromolecule interactions is finally making sense!

In a recent collaborative work, the molecular mechanism of the interactions between macromolecules and Hofmeister cations is elucidated. Although all metal cations are on average depleted from the macromolecule/water interface, more strongly hydrated metal cations (Ca2+, Mg2+) are able to locally accumulate around the amide oxygen. Such weakly favorable interactions aided partially offset of the salting-out effect. Surprisingly, the cations approach the interface together with chloride counter anions as solvent-shared ion pairs. (read more…)

A new article on exploring the surface propensity of molecular ions in ionic liquid mixtures.

In this study, in collaboration with Suzer Lab, we have demonstrated the surface propensity of TFSI anion over BF4 anion in mixture of ionic liquids. We have developed a new methodology including measurements of angle-resolved X-Ray photoelectron spectroscopy and contact angle along with a signal attenuated modeling to report on the specific surface enrichment of different species in liquid mixtures. This new multi-instrumental method is applicable to various liquid systems. (Read more)