Solvation Shell Anatomy of H2S and CO Dissolved in Reline and Ethaline Deep Eutectic Solvents.

Rising atmospheric concentrations of anthropogenic hydrogen sulfide (H2S) and carbon monoxide (CO) as a result of industrialization have encouraged researchers to explore innovative technologies for capturing these gases. Deep eutectic solvents (DESs) are an alternative media for mitigating H2S and CO emissions. Herein, we have employed ab initio molecular dynamics simulations to investigate the structures of the nearest-neighbor solvation shells surrounding H2S and CO when they are dissolved in reline and ethaline DESs. We aim to delineate the structural arrangement responsible for favorable H2S and CO capture by analyzing the key interactions between H2S and CO solutes with various components of the DESs. We observe that in the reline-H2S system, chloride and carbonyl oxygen of urea are found to have the closest distance interaction with hydrogen atoms of the H2S solute. The sulfur atom of H2S is found to be predominantly solvated by hydrogen and oxygen atoms of urea molecules and the hydroxyl hydrogen of choline cations. The chloride ions and ethylene glycol molecules predominantly govern the solvation of H2S in the ethaline-H2S system. In both the DESs, H2S is solvated by the hydroxyl group of the choline cations rather than by their ammonium group. In the reline-CO system, all the atoms of urea along with chloride dominate the immediate solvation shell around CO. In the ethaline-CO system, hydroxyl oxygen and hydrogen atoms of ethylene glycol are found in the nearest solvation structure around CO. Both the DESs exhibit a stronger solvent-solute charge-transfer tendency toward the H2S solute compared to CO.

Origin of structural and dynamic heterogeneity in thymol and coumarin-based hydrophobic deep eutectic solvents as revealed by molecular dynamics.

Hydrophobic deep eutectic solvents (HDESs) have recently emerged as a class of water-immiscible solvents with greener starting materials and inherent hydrophobic character, opening the gates to various new promising applications. Herein, we have carried out all-atom molecular dynamics simulations to comprehend the bulk phase structural organization and dynamic behavior of thymol and coumarin-based HDESs at two molar ratios of the constituent components. The simulated X-ray and neutron scattering structure functions (S(q)s) indicate a prepeak signifying that these HDESs possess nanoscale heterogeneity or intermediate range ordering. The decomposition of the total S(q)s based on polarity reveals that clustering of the polar group present in thymol and coumarin leads to the presence of the prepeak which also has small contributions from the apolar-apolar correlations. The intermolecular hydrogen bonding network between thymol-coumarin and thymol-thymol mainly guides the arrangement of the HDESs. We find a stronger hydrogen bond between the carbonyl oxygen of coumarin and the hydroxyl hydrogen of thymol, marked by the longer hydrogen bond lifetime. In contrast, the shorter lifetime of the hydrogen bond between the hydroxyl oxygen and the hydroxyl hydrogen of thymol suggests a weaker hydrogen bonding. On changing the thymol : coumarin molar ratio from 1 : 1 to 2 : 1, the average lifetimes of both the hydrogen bonds decrease, suggesting stronger hydrogen bonds in the 1 : 1 HDES. The translational dynamics of thymol and coumarin become faster in the 2 : 1 thymol : coumarin HDES. A slightly stronger caging effect is observed for coumarin in comparison to thymol molecules. From the analysis of the non-Gaussian parameter, we observe the presence of heterogeneity in the translational displacements of thymol and coumarin molecules. Furthermore, the computed self-van Hove correlation functions reveal that thymol and coumarin molecules cover more distances than the ideal diffusive displacements, confirming the presence of dynamic heterogeneity.

Clinical outcome of testosterone supplementation assessed by andropausal male symptom scores in type 2 diabetes testosterone-deficient patients receiving testosterone compared to those not receiving testosterone: A nested case-control study.

BACKGROUND AND AIMS: This study aimed to explore the proportion of andropause in male patients with type 2 diabetes using an aging male symptoms scale and assess the clinical outcome of testosterone supplementation in patients with deficient testosterone levels at a tertiary care hospital. METHODS: Male patients with diabetes and total serum testosterone levels (≤12 nmol/L) were included in the study. Patients with testosterone supplementation, the standard of care among testosterone-deficient male patients, were included in the study (n = 35). Those not exposed to testosterone supplementation were considered controls (n = 35) and reassessed over 14 weeks for aging male symptom scores (AMS). RESULTS: The prevalence of andropause among the participants was 11% (117/1057). Data was analyzed as per protocol analysis. Exposure group had a frequency of 25.80%, and 19.35% in moderate and severe symptoms of AMS scores. Non-exposure group had frequency of 26.66% and 23.34% in moderate and severe symptoms of AMS scores. A significant mean difference (t = -2.93, P-value <0.05) was noted between exposure and non-exposure to testosterone supplementation. CONCLUSION: Results concluded that andropause is prevalent in patients with type 2 diabetes and low testosterone levels. Testosterone therapy affects aging andropausal symptoms such as the feeling of general well-being, joint pain and muscular ache, sleep problems, anxiety, and libido among patients with type 2 diabetes.

Solvation Shell Structures of Ammonia in Reline and Ethaline Deep Eutectic Solvents.

Because of increasing atmospheric anthropogenic ammonia (NH3) emission, researchers are devising new techniques to capture NH3. Deep eutectic solvents (DESs) are found as potential media for NH3 mitigation. In the present study, we have carried out ab initio molecular dynamics (AIMD) simulations to decipher the solvation shell structures of an ammonia solute in reline (1:2 mixture of choline chloride and urea) and ethaline (1:2 mixture of choline chloride and ethylene glycol) DESs. We aim to resolve the fundamental interactions which help stabilize NH3 in these DESs, focusing on the structural arrangement of the DES species in the nearest solvation shell around NH3 solute. In reline, the hydrogen atoms of NH3 are preferentially solvated by chloride anions and the carbonyl oxygen atoms of urea. The nitrogen atom of NH3 renders hydrogen bonding with hydroxyl hydrogen of the choline cation. The positively charged head groups of the choline cations prefer to stay away from NH3 solute. In ethaline, strong hydrogen bonding interaction exists between the nitrogen atom of NH3 and hydroxyl hydrogen atoms of ethylene glycol. The hydrogen atoms of NH3 are found to be solvated by hydroxyl oxygen atoms of ethylene glycol and choline cation. While ethylene glycol molecules play a crucial role in solvating NH3, the chloride anions remain passive in deciding the first solvation shell. In both the DESs, choline cations approach NH3 from their hydroxyl group side. We observe slightly stronger solute-solvent charge transfer and hydrogen bonding interaction in ethaline than those in reline.

Solvent Organization around Methane Dissolved in Archetypal Reline and Ethaline Deep Eutectic Solvents as Revealed by AIMD Investigation.

Because of the rising concentration of harmful greenhouse gases like methane in the atmosphere, researchers are striving for developing novel techniques for capturing these gases. Recently, neoteric liquids such as deep eutectic solvents (DESs) have emerged as an efficient means of sequestration of methane. Herein, we have performed ab initio molecular dynamics (AIMD) simulations to elucidate the solvation structure around a methane molecule dissolved in reline and ethaline DESs. We aim to elicit the structural organization of different constituents of the DESs in the vicinity of methane, particularly highlighting the key interactions that stabilize such gases in DESs. We observe quite different solvation structures of methane in the two DESs. In ethaline, chloride ions play an active role in solvating methane. Instead, in reline, chloride ions do not interact much with the methane molecule in the first solvation shell. In reline, choline cations approach the methane molecule from their hydroxyl group side, whereas urea molecules approach methane from their carbonyl oxygen as well as amide group sides. In ethaline, ethylene glycol and Cl- dominate the nearest neighbor solvation structure around the methane molecule. In both the DESs, we do not observe any significant methane-DES charge transfer interactions, apart from what is present between choline cation and Cl- anion.

An Overview of Structure and Dynamics Associated with Hydrophobic Deep Eutectic Solvents and Their Applications in Extraction Processes.

Recent development of novel water-immiscible green solvents known as hydrophobic deep eutectic solvents (HDESs) has opened the gates for applications requiring media where the presence of water is undesirable. Ever since they were prepared, researchers have used HDESs in diverse fields such as extraction processes, CO2 sequestration, membrane formation, and catalysis. The structure and dynamics associated with the species comprising HDESs guide their suitability for specific applications. For example, varying the alkyl tail length of the HDES components significantly affects the dynamics of the components and thus helps in tuning the efficiency of extraction processes. However, the development of HDESs is still in infancy, and very few theoretical studies are available in the literature that help in understanding the structure and dynamics of HDESs. This review highlights the recent studies focused on the microscopic structure and dynamics of HDESs and their potential applications, particularly in extraction processes. We have also provided a glimpse of how the integration of experiments and computational techniques can help delineate the mechanism of extraction processes.

Multiple evidences of dynamic heterogeneity in hydrophobic deep eutectic solvents.

Hydrophobic deep eutectic solvents (HDESs) have gained immense popularity because of their promising applications in extraction processes. Herein, we employ atomistic molecular dynamics simulations to unveil the dynamics of DL-menthol (DLM) based HDESs with hexanoic (C6), octanoic (C8), and decanoic (C10) acids as hydrogen bond donors. The particular focus is on understanding the nature of dynamics with changing acid tail length. For all three HDESs, two modes of hydrogen bond relaxations are observed. We observe longer hydrogen bond lifetimes of the inter-molecular hydrogen bonding interactions between the carbonyl oxygen of the acid and hydroxyl oxygen of menthol with hydroxyl hydrogen of both acids and menthol. We infer strong hydrogen bonding between them compared to that between hydroxyl oxygen of acids and hydroxyl hydrogens of menthol and acids, marked by a faster decay rate and shorter hydrogen bond lifetime. The translational dynamics of the species in the HDES becomes slower with increasing tail length of the organic acid. Slightly enhanced caging is also observed for the HDES with a longer tail length of the acids. The evidence of dynamic heterogeneity in the displacements of the component molecules is observed in all the HDESs. From the values of the α-relaxation time scale, we observe that the molecular displacements become random in a shorter time scale for DLM-C6. The analysis of the self-van Hove function reveals that the overall distance covered by DLM and acid molecules in the respective HDES is more than what is expected from ideal diffusion. As marked by the shorter time scale associated with hole filling, the diffusion of the oxygen atom of menthol and the carbonyl oxygen of acid from one site to the other is fastest for hexanoic acid containing HDES.

Distinct Solvation Structures of CO2 and SO2 in Reline and Ethaline Deep Eutectic Solvents Revealed by AIMD Simulations.

Deep eutectic solvents (DESs) are emerging as an alternative media for the sequestration of greenhouse gases such as CO2 and SO2. Herein, we performed ab initio molecular dynamics (AIMD) simulations to elucidate the solvation structure around CO2 and SO2 in choline chloride-based DESs, namely, reline and ethaline. We show that in all four systems the structures of the nearest neighbor shells around these molecules are distinct. We observe that because of the electrophilic character, the carbon atom of CO2 and the sulfur atom of SO2 are preferentially solvated by the chloride anions. The strength of the correlation between the chloride anions and the sulfur atom is much stronger because of charge transfer, which is more profound in ethaline DES. In both DESs, the choline cations are found to be closer to the oxygen atoms of CO2 and SO2. We observe that upon changing the solute from CO2 to SO2, the nearest neighbor solvation structure changes drastically; while the chloride anions prefer to stay in a circular shell around the carbon atom of CO2, they are found to be much more localized near the sulfur atom of SO2. The solvation shells formed by the urea molecules in reline and EG molecules in ethaline also overlap with that of the chloride anion around CO2. In ethaline, the hydroxyl group of the choline cation is found to be closer to the solute molecules as compared to its ammonium headgroup.

Heterogeneity in hydrophobic deep eutectic solvents: SAXS prepeak and local environments.

Recently, the introduction of novel deep eutectic solvents having a hydrophobic character with greener starting materials has motivated researchers to explore these water-immiscible solvents, owing to their new potential applications. In this regard, herein atomistic molecular dynamics simulations have been performed to understand the bulk phase morphology present in dl-menthol based hydrophobic deep eutectic solvents (HDESs) with organic acids of different chain lengths used as hydrogen bond donors. From the appearance of a prepeak in the simulated total X-ray scattering structure function (S(q)), we found an evidence of intermediate-range structural organization in these HDESs. We show that the prepeak originates from the self-segregation of dl-menthol and the polar hydroxyl groups of the acids, as witnessed from partitioning of the total S(q). Surprisingly, even for a very long tail containing HDES, the apolar-apolar component shows only nominal contribution to the prepeak. We show that the structure of these HDESs is dominated by a set of very strong intermolecular hydrogen bonding between menthol-menthol, acid-acid, and menthol-acid molecules. Our results show that there is competition between the hydroxyl hydrogen of the acids and menthol to form an intermolecular hydrogen bond with the carbonyl oxygen of the acids and hydroxyl oxygen of menthol.

Molecular dynamics investigation of wetting-dewetting behavior of reline DES nanodroplet at model carbon material.

Deep eutectic solvents (DESs) have emerged as a promising class of solvents for application in nanotechnology, particularly for designing new functional nanomaterials based on carbon. Here, we have employed molecular dynamics simulations to understand the structuring of choline chloride and urea-based DES, reline, nanodroplets on carbon sheets with varying strength of the DES-sheet interaction potentials. The wetting-dewetting nature of reline has been investigated by analyzing simulated contact angles formed by its nanodroplets on the carbon sheets. Through this investigation, we find that at the lowest DES-sheet interaction strength, the contact angle formed by the reline nanodroplet on the carbon surface exceeds 150°, indicating that the surface is supersolvophobic. On the other hand, at the higher interaction potentials, reline DES wets the surface of the sheets, forming an adlayer primarily consisting of urea molecules. The choline cation and urea molecules are observed to exhibit stronger interactions with the carbon surface as compared to that of chloride anions. At the supersolvophobic carbon surface, the urea molecules have relatively higher density in the bulk of the nanodroplet, whereas the choline cation and chloride have major contributions to the outer layers of the droplets. Moreover, at the solvophilic surfaces, urea molecules are present in the adlayer, as well as in the bulk of the droplets, whereas the reline-vapor interface majorly consists of choline and chloride ions.

Anatomy of Microscopic Structure of Ethaline Deep Eutectic Solvent Decoded through Molecular Dynamics Simulations.

Atomistic molecular dynamics simulations have been performed to investigate the microscopic structure of ethaline deep eutectic solvent (DES), a mixture of choline chloride ([Ch][Cl]) and ethylene glycol (EG) in molar ratio of 1:2, respectively. As much as the structure of a DES is derived by the composition of the species present in it, the chemical nature of the hydrogen bond donor species involved also plays a crucial role in laying down the microscopic structure of DESs. By virtue of its inherent chemical structure, EG renders both intra- and intermolecular hydrogen bonds. Therefore, the molecular level structural landscape of DESs containing EG as hydrogen bond donor is reckoned to be a bit complex. In the present study, we aim to understand the structural morphology of ethaline using optimum force-field parameters for EG recently proposed by our group. After an initial assessment of the refined force-field parameters for ethaline DES, we have presented an in-depth analysis of the arrangement and ordering of its components at the molecular level. Simulated X-ray scattering structure function and its partial components reveal the presence of short-range as well as long-range interactions in ethaline. The role of hydrogen bonding interactions among all the three species [Ch]+, [Cl]-, and EG was predominantly observed through radial and radial-angular distribution functions and substantiated by spatial distribution functions. The observation of the competitive nature of [Ch]+ and EG to form a hydrogen bond with the anion is one of the major outcomes of the present study. Also, weaker intra- and intermolecular hydrogen bonding interactions between EG molecules were seen along with their simultaneous involvement with the ammonium group of the choline cation.