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Molecular Dynamics Simulations for the Extraction of Aromatics and Pesticide
Published in Papu Kumar Naik, Nikhil Kumar, Nabendu Paul, Tamal Banerjee, Deep Eutectic Solvents in Liquid–Liquid Extraction, 2023
Papu Kumar Naik, Nikhil Kumar, Nabendu Paul, Tamal Banerjee
RDFs are shown in Figure 3.20, where the selected atoms for different molecular species were O1 atom of nitenpyram, H51 and O5 atom of octanoic acid, H35 atom of DL-menthol, and H57 atom of the water molecule (notations as in Figure 3.2). It appeared that the well-defined first solvation shell for the DL-menthol and nitenpyram molecules was at 2 Å, suggesting a higher interaction between these two species (Figure 3.20a). The presence of water molecules at the first solvation shell (1.95 Å) was also observed, suggesting an interaction between nitenpyram and water. However, the coordination number of water molecules around nitenpyram moiety was 1.50, which was lower than DL-menthol around nitenpyram moiety (1.90), indicating a weaker interaction among them. For octanoic acid, it was at 3.35 Å (Figure 3.20a), justifying a relatively weaker interaction compared to nitenpyram–DL-menthol. A sharp peak was observed for DL-menthol and octanoic acid moiety at 2.05 Å (Figure 3.20b), reflecting a very strong HBA–HBD interaction and leading to the fact that the DES did not disintegrate in the presence of an aqueous environment. Moreover, a higher coordination number of HBA–HBD (5.50) compared to a very low value of HBD–water (0.75) strongly supports the higher stability of the DES in an aqueous medium.
Raman Spectroscopy of Surfaces
Published in Arthur T. Hubbard, The Handbook of Surface Imaging and Visualization, 2022
Trace amounts of water, which invariably exist in these solvents even if dried, are also seen in the surface spectra. Figure 47.13 shows spectra in the υ(O-H) region for this trace water in 1-butanol. Interestingly, four discrete bands labeled A, F, C, and H can be observed at different potentials. The A band is assigned to interfacial water molecules that are hydrogen bonded to specifically adsorbed anions. This band decreases in intensity as the PZC is reached, consistent with elimination of Br– from the electrode surface. The F band is assigned to free water in the interface. This may be water that is associated with the second solvation shell of the Li+. This band decreases in intensity as the PZC is reached at the expense of the cation band, or the C band, which grows in. The C band is attributed to water in the primary solvation shell of Li+, which interacts with the surface at negative potentials with its hydrogen end. This band becomes very intense at negative potentials as the Li+ species are electrostatically attracted to the negatively charged surface. At very negative potentials, the H band is observed. This band is thought to be due to OH- species in the interface that are produced by the reduction of water at these very negative potentials.
New Insights into the Recovery of Strategic and Critical Metals by Solvent Extraction
Published in Bruce A. Moyer, Ion Exchange and Solvent Extraction: Volume 23, 2019
Jason B. Love, Manuel Miguirditchian, Alexandre Chagnes
The existence of the predominant species UO2(HL)2L2S predicted by the physicochemical model was demonstrated by means of TRLFS. It is particularly interesting to highlight that the TOPO molecule in this species is located in the first solvation shell of uranium(VI), as it was also confirmed by DFT calculations (Figure 1.18). DFT calculation of the optimized geometry of UO2(HL)2L2(TOPO).H2O (TOPO in the first solvation shell). Hydrogen atoms were removed from the figure for the sake of readability. Red atoms: oxygen. Orange atoms: phosphorus. Blue atoms: uranium. Gray atoms: carbon.
Charge-transfer-to-solvent states provide a sensitive spectroscopic probe of the local solvent structure around anions
Published in Molecular Physics, 2023
Ronit Sarangi, Kaushik D. Nanda, Anna I. Krylov
We determined that the CIS spectrum needs at least 20 waters in the QM region for excitation energies to converge within 0.01 eV, as shown in Figure S1 in the SI. The first solvation shell of SCN contains 8 waters; 20 waters correspond roughly to two solvation shells. Given the importance of Pauli repulsion for these states (i.e. without it, the electron density can extend too far into the solvent), it is not surprising that at least two solvation shells are needed for an adequate description of the CTTS bands. For each snapshot, the QM system was determined by choosing 20 water molecules that are closest to the carbon atom of the anion. Because of the potential exchange between quantum and classical waters in the course of AIMD simulation, it means that the QM system in the calculation of spectra slightly differs from the QM system in the AIMD snapshot; our analysis indicates that these adjustments only affected a small number of snapshots and only affected the outermost water molecules.
Investigation of coarse-grained models across a glass transition
Published in Soft Materials, 2020
At the higher, glass phase density (left column), the AA rdf demonstrates the greatest structure at the lowest temperature ( = 270 K) and the least structure at the highest temperature ( = 400 K). However, the AA rdf calculated at the intermediate temperature = 330 K, which is near the glass transition, 343 K, appears distinct. This intermediate rdf appears very similar to the glass phase rdf in the first solvation shell, but more like the liquid phase rdf in the second solvation shell. Moreover, the MS-CG pair potential calculated near the glass transition temperature is more repulsive than the pair potentials calculated for temperatures below ( = 270 K) and above ( = 400 K) the glass transition.
The liquid structure of the solvents dimethylformamide (DMF) and dimethylacetamide (DMA)
Published in Molecular Physics, 2019
N. Basma, P. L. Cullen, A. J. Clancy, M. S. P. Shaffer, N. T. Skipper, T. F. Headen, C. A. Howard
For DMA, the aRDF (Figure 10) was calculated with the angle θ between the axes lying along the C2-O axis, i.e. the direction of the dipole moment (see Figure 8). As with DMF, there is little orientational preference beyond the first solvation shell; however, unlike DMF, there is a slight orientational preference in the first solvation shell for parallel interactions. This arrangement suggests that dipole-dipole interactions are less dominant in DMA than for DMF. To investigate further, the N … O and O … O partial g(r)s for DMA and DMF are plotted alongside spatial density functions for the 20% most likely locations of oxygen atoms in the first solvation shell in Figure 11. For DMF, there is a clear preference for short-range N … O interactions compared to DMA, with a large peak at ∼4 Å. Similarly, the O … O show shorter range correlations in DMF compare to DMA. Conversely, DMA shows greater N … O correlations at a slightly longer range, peaking at ∼6 Å. This trend is also evident from inspections of the oxygen spatial density functions, where a clear second shell is shown for DMA that is not present in DMF.