Effects of Ions on the OH Stretching Band of Water as Revealed by ATR-IR Spectroscopy

Selvakumar

et al. 2015

Chemistry A European J

Creating structure-property correlations at different distance scales is one of the important challenges to the rational design of molecular gelators. Here, a series of dihydroxylated derivatives of long-chain fatty acids, derived from three naturally occurring molecules-oleic, erucic and ricinoleic acids-are investigated as gelators of a wide variety of liquids. Conclusions about what constitutes a more (or less!) efficient gelator are based upon analyses of a variety of thermal, structural, molecular modeling, and rheological results. Correlations between the manner of molecular packing in the neat solid or gel states of the gelators and Hansen solubility data from the liquids leads to the conclusion that diol stereochemistry, the number of carbon atoms separating the two hydroxyl groups, and the length of the alkanoic chains are the most important structural parameters controlling efficiency of gel formation for these gelators. Some of the diol gelators are as efficient or even more efficient than the well-known, excellent gelator, (R)-12-hydroxystearic acid; others are much worse. The ability to form extensive intermolecular H-bonding networks along the alkyl chains appears to play a key role in promoting fiber growth and, thus, gelation. In toto, the results demonstrate how the efficiency of gelation can be modulated by very small structural changes and also suggest how other structural modifications may be exploited to create efficient gelators.

Section: Molecular Packing Arrangements Frompowder X-ray Diffraction supporting

confidence: 53%

Structural and Solubility Parameter Correlations of Gelation Abilities for Dihydroxylated Derivatives of Long‐Chain, Naturally Occurring Fatty Acids

Selvakumar

et al. 2015

Chemistry A European J

“…The relative difference in the contributions implies that the H‐bonding in the 9,12 R ‐diol solid state is stronger than that of HSA 41. 42 Based on FT‐IR spectra, the same conclusion is reached for the comparative hydroxyl H‐bonding strengths in the nitrobenzene gels of 9,12 R ‐diol and HSA. The similarities between the frequencies of the OH stretching (as well as the similarities in the XRD diffraction patterns; Figure 4 and Table 4) strongly suggest that the molecular packing within a SAFiN and the corresponding neat gelator are very similar.…”

Section: Resultsmentioning

confidence: 73%

Salicylato Titanocene Complexes as Cooperative Organometallic Lewis Acid and Brønsted Acid Catalysts for Three‐Component Mannich Reactions

Chen

Jia

et al. 2014

Chemistry A European J

A binary acid system has been developed that features an air-stable organometallic precursor, titanocene dichloride, and simple organic cooperative Brønsted acids, which allowed for mild and highly efficient Mannich reactions of both aryl and alkyl ketones with excellent yields and satisfactory diastereoselectivity. Mechanistic studies, including (1) H NMR titration, X-ray structure analyses as well as isolation of catalytically active species, elucidated the dramatic synergistic effects of this new binary acid system.

Diamond and Related Materials

“…Mochalin et al [31] reported a considerable shift of the bending vibration peak to lower wavenumbers as well as a decrease of its intensity upon annealing of acid oxidized DNDs up to 300°C. Such shift is probably a temperature effect since the higher the temperature the lower is the hydrogen bond strength resulting in a shift to lower frequencies [25]. It is important to mention that according to Mochalin et al [29], the bending vibration peak of water disappeared only after 15 min annealing at 425°C suggesting rather a strong, hydrophilic interaction of water with the surface of oxidized DNDs.…”

Section: Discussionmentioning

confidence: 97%

“…and sol.). As all the vibrational bands in liquid water originate from contributions of water molecules in different hydrogen bonded environments, the molecular stretch vibrations shift to higher frequency as hydrogen bonding weakens [25], whereas the molecular bending vibration peak shifts to lower frequencies and becomes both narrower and stronger [26]. Scatena et al [27] showed that the hydrogen bonding between adjacent water molecules at the hydrophobic-water interfaces is weak.…”

Section: Discussionmentioning

confidence: 99%

Water interaction with hydrogenated and oxidized detonation nanodiamonds — Microscopic and spectroscopic analyses

Stehlík

Glatzel

Pichot

et al. 2016

a b s t r a c tWater interaction with surface modified nanodiamonds (NDs) is critical for many possible applications of NDs e.g. in biomedicine. Here we report on investigation of water interaction with hydrogenated and oxidized detonation nanodiamonds (H-DNDs, O-DNDs) by means of Fourier transform infrared spectroscopy (FTIR), thermal analysis, and Kelvin probe force microscopy (KPFM). Higher water content (4.4%) as well as weaker interaction of water with H-DNDs are identified by thermal analysis. It is explained by hydrophobicity of the H-DND surface, as revealed by the analysis of bending and stretching vibrations of surface water in FTIR spectra. On the other hand, hydrophilic nature of O-DNDs leads to lower water content (3.1%) but stronger interaction with the O-DND surface. This is evidenced by as high as 300°C desorption temperature of the surface water from O-DNDs. KPFM analysis shows that the surface-bound water can have significant screening effect on contact potential difference (CPD) of nanodiamonds (up to 510 mV) as well as on the CPD difference between H-DNDs and O-DNDs (from 50 mV to 210 mV). Nevertheless, H-DNDs exhibit always lower work function.