Specific ion effects in non-aqueous solutions

Electrolyte solutions play a central role in life and technological processes because of their complexity. This complexity is yet to be described by a predictive theory of the specific effects that different ions induce in solution. The vast majority of investigations of specific-ion effects have been conducted in aqueous solutions. These studies have revealed that amongst the complexity, the effectiveness of the ions often follow trends that are apparent across a number of very different experiments, revealing an underlying order (e.g. the Hofmeister series). It is often assumed that water itself is intricately involved in these trends. Here I investigate specific-ion effects in non-aqueous solvents rather than water. By extending the investigation to a number of non-aqueous solvents, the role of the solvent in specific-ion effect trends can be elucidated and a better understanding of the general phenomenon gained. Firstly, a more definite terminology is developed for describing the specific-ion effects trends in order to address the current confusion in the literature and provide a basis for the following investigations. An extensive investigation of the scarce literature demonstrates that water is by no means a special solvent with regards to ion-specificity, and that within the complexity there is universality. An investigation of electrostriction under the conditions of infinite dilution shows that the same fundamental specific ion trends are observed across all solvents, demonstrating that ion-specificity arises from the ions themselves. In this regard the influence of solvents, surfaces and real concentrations of electrolytes can be seen as perturbations to this fundamental series. Further work shows that for systems that are perturbed, the trends in non-aqueous protic solvents can be expected to follow the same trend in water; and in aprotic solvents the cations are more likely to adhere to the trend in water than the anions. My experimental work focuses on specific-anion effects of seven Hofmeister sodium salts in the solvents: water, methanol, formamide, dimethyl sulfoxide and propylene carbonate. Two very different experiments were performed; the elution of electrolytes from a size-exclusion chromatography column and an investigation of the electrolyte moderated swelling of a cationic brush (PMETAC) using a Quartz Crystal Microbalance (QCM). The trends observed are consistent across these experiments. A forward or reverse Hofmeister series is observed in practically all salt-solvent combinations, and the reversal is attributed to the polarisability of the solvent. Finally, a qualitative model of ion specific trends is formulated, where the specific-ion effects are fundamentally a property of the ion, and the associated trends correspond to the Hofmeister series for anions and the lyotropic series for cations. When the concentration is increased, or surfaces introduced, the effects of ion-ion interactions and ion-surface interactions can perturb the fundamental series. The perturbation of the series is related to the proticity of the solvent for ion-ion interactions, whereas the polarisability of the solvent and ion are important when a surface is present. This work for the first time individuates the principal properties of the solvent that affect their ordering: proticity and polarisability

Volcano Plots Emerge from a Sea of Nonaqueous Solvents: The Law of Matching Water Affinities Extends to All Solvents

The properties of all electrolyte solutions, whether the solvent is aqueous or nonaqueous, are strongly dependent on the nature of the ions in solution. The consequences of these specific-ion effects are significant and manifest from biochemistry to battery technology. The "law of matching water affinities" (LMWA) has proven to be a powerful concept for understanding and predicting specific-ion effects in a wide range of systems, including the stability of proteins and colloids, solubility, the behavior of lipids, surfactants, and polyelectrolytes, and catalysis in water and ionic liquids. It provides a framework for considering how the ions of an electrolyte interact in manifestations of ion specificity and therefore represents a considerable conceptual advance on the Hofmeister or lyotropic series in understanding specific-ion effects. Underpinning the development of the law of matching water affinities were efforts to interpret the so-called "volcano plots". Volcano plots exhibit a stark inverted "V" shape trend for a range of electrolyte dependent solution properties when plotted against the difference in solvation energies of the ions that constitute the electrolyte. Here we test the hypothesis that volcano plots are also manifest in nonaqueous solvents in order to investigate whether the LMWA can be extended to nonaqueous solvents. First we examine the standard solvation energies of electrolytes in nonaqueous solvents for evidence of volcano trends and then extend this to include the solubility and the activity/osmotic coefficients of electrolytes, in order to explore real electrolyte concentrations. We find that with respect to the solvent volcano trends are universal, which brings into question the role of solvent affinity in the manifestation of specific-ion effects. We also show that the volcano trends are maintained when the ionic radii are used in place of the absolute solvation energies as the abscissa, thus showing that ion sizes, rather than the solvent affinities, fundamentally determine the manifestation of ion specificity. This leads us to propose that specific-ion effects across all solvents including water can be understood by considering the relative sizes of the anion and cation, provided the ions are spherical or tetrahedral. This is an extension of the LMWA to all solvents in which the "water affinity" is replaced with the relative size of the anion and cation.The authors recognize the great importance of the fundamental work of Y. Marcus to the data analysis presented here. V.S.J.C. gratefully acknowledges the financial support of the Australian Research Council (FT0991933)

Air trapping in COVID-19 patients following hospital discharge : retrospective evaluation with paired inspiratory/expiratory thin-section CT

The study reports our experience with paired inspiration/expiration thin-section computed tomographic (CT) scans in the follow-up of COVID-19 patients with persistent respiratory symptoms. From August 13, 2020, to May 31, 2021, 48 long-COVID patients with respiratory symptoms (27 men and 21 women; median age, 62.0 years; interquartile range: 54.0-69.0 years) underwent follow-up paired inspiration-expiration thin-section CT scans. Patient demographics, length of hospital stay, intensive care unit admission rate, and clinical and laboratory features of acute infection were also included. The scans were obtained on a median of 72.5 days after onset of symptoms (interquartile range: 58.5-86.5) and at least 30 days after hospital discharge. Thin-section CT findings included ground-glass opacity, mosaic attenuation pattern, consolidation, traction bronchiectasis, reticulation, parenchymal bands, bronchial wall thickening, and air trapping. We used a quantitative score to determine the degree of air trapping in the expiratory scans. Parenchymal abnormality was found in 50% (24/48) of patients and included air trapping (37/48, 77%), ground-glass opacities (19/48, 40%), reticulation (18/48, 38%), parenchymal bands (15/48, 31%), traction bronchiectasis (9/48, 19%), mosaic attenuation pattern (9/48, 19%), bronchial wall thickening (6/48, 13%), and consolidation (2/48, 4%). The absence of air trapping was observed in 11/48 (23%), mild air trapping in 20/48 (42%), moderate in 13/48 (27%), and severe in 4/48 (8%). Independent predictors of air trapping were, in decreasing order of importance, gender (p = 0.0085), and age (p = 0.0182). Our results, in a limited number of patients, suggest that follow-up with paired inspiratory/expiratory CT in long-COVID patients with persistent respiratory symptoms commonly displays air trapping. • Our experience indicates that paired inspiratory/expiratory CT in long-COVID patients with persistent respiratory symptoms commonly displays air trapping. • Iterative reconstruction and dose-reduction options are recommended for demonstrating air trapping in long-COVID patients

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Correction: What is the fundamental ion-specific series for anions and cations? Ion specificity in standard partial molar volumes of electrolytes and electrostriction in water and non-aqueous solvents

Correction for ‘What is the fundamental ion-specific series for anions and cations? Ion specificity in standard partial molar volumes of electrolytes and electrostriction in water and non-aqueous solvents’ by Virginia Mazzini et al., Chem. Sci., 2017, 8, 7052–7065

Corrigendum to “Specific-ion Effects in Non-Aqueous Systems” [Curr Opin Colloid Interface Sci 23 (June 2016) 82–93]

Due to our continued research in the field, we have realised that the ordering of ions of Figure 2 needs to be rectified

Probing the Hofmeister series beyond water: Specific-ion effects in non-aqueous solvents

with the aim of elucidating the role of the solvent in perturbing the fundamental ion-specific trend. The focus is on the anions: CH3COO−>F−>Cl−>Br−>I−>ClO4−>SCN− in the solvents water, methanol, formamide, dimethyl sulfoxide (DMSO), and propylene carbonate (PC). Two types of experiments are presented. The first experiment employs the technique of size exclusion chromatography to evaluate the elution times of electrolytes in the different solvents. We observe that the fundamental (Hofmeister) series is observed in water and methanol, whilst the series is reversed in DMSO and PC. No clear series is observed for formamide. The second experiment uses the quartz crystal microbalance technique to follow the ion-induced swelling and collapse of a polyelectrolyte brush. Here the fundamental series is observed in the protic solvents water, methanol, and formamide, and the series is once again reversed in DMSO and PC. These behaviours are not attributed to the protic/aprotic nature of the solvents, but rather to the polarisability of the solvents and are due to the competition between the interaction of ions with the solvent and the surface. A rule of thumb is proposed for ion specificity in non-aqueous solvents. In weakly polarisable solvents, the trends in specific-ion effects will follow those in water, whereas in strongly polarisable solvents the reverse trend will be observed. Solvents of intermediate polarisability will give weak specific-ion effects.V.S.J.C. acknowledges the Australian Research Council for funding. G.M.L. acknowledges the financial support of the National Natural Science Foundation of China (Nos. 21574121 and 21622405)