Liquid-expanded spectroscopy

An Oven/iew of a Rapidly Expanding Area in Chemistry Exploring the future in chemical analysis research, Ionic Liquids in Chemical Analysis focuses on materials that promise entirely new ways to perform solution chemistry. It provides a broad overview of the applications of ionic liquids in various areas of analytical chemistry, including separation science, spectroscopy, mass spectrometry, and sensors. 

Figure 10.17—Cells used for mid IR spectroscopy, a) Gas cell with direct optical path (reproduced with permission of Wilmad) b) expanded view of a liquid cell with a fixed path-length (from Eurolabo document).

This molecular argument may explain the earlier-described and repeatedly observed finding with concentrated gas-in-liquid emulsions (see Section 10.4) that, following a period of microbubble growth, the average hydrodynamic diameters (detected by photon correlation spectroscopy) of the microbubble and micellar populations simultaneously decreased. In such situations, microbubble fission may have occurred (following microbubble collision) and the surfactant molecules needed for the expanding... 

Liquid carbon dioxide (purity 99, 95 Vol %) was undercooled (W2) to avoid cavitation in the membran pump (P). After the compression to pre-expansion pressure, the fluid is heated to the extraction temperature (W3). The supercritical fluid loaded with anthracene leaves the extractor (V = 0,6 1). With a additional heat exchanger (W4), the solution is heated to pre-expansion temperature. In the separation vessel, the supercritical solution is expanded through a nozzle. The expanded gas will be condensed (Wl) and recompressed or let off. After the experiment, the separation vessel is opened and the particles were collected. The particle size is measured by laser diffraction spectroscopy (Malvern Master Sizer X). 

The studies presented here illuminate just a few of the exciting possibilities for the use of VSFS to study chemistry at liquid/liquid surfaces. Solvents and adsorbates can be probed and orientations and conformations obtained. Molecular dynamics has recently been employed to gain additional information using the constraints provided by the spectroscopy. The future of this technique lies in expanding the spectrum to longer wavelengths so that more vibrations can be probed in each molecule and more complicated molecules can be studied. The study of interfacial dynamics will also offer exciting opportunities for the future. 

This narrative echoes the themes addressed in our recent review on the properties of uncommon solvent anions. We do not pretend to be comprehensive or inclusive, as the literature on electron solvation is vast and rapidly expanding. This increase is cnrrently driven by ultrafast laser spectroscopy studies of electron injection and relaxation dynamics (see Chap. 2), and by gas phase studies of anion clusters by photoelectron and IR spectroscopy. Despite the great importance of the solvated/ hydrated electron for radiation chemistry (as this species is a common reducing agent in radiolysis of liquids and solids), pulse radiolysis studies of solvated electrons are becoming less frequent perhaps due to the insufficient time resolution of the method (picoseconds) as compared to state-of-the-art laser studies (time resolution to 5 fs ). The welcome exceptions are the recent spectroscopic and kinetic studies of hydrated electrons in supercriticaF and supercooled water. As the theoretical models for high-temperature hydrated electrons and the reaction mechanisms for these species are still rmder debate, we will exclude such extreme conditions from this review. 

Guadagno, T. and S.G. Kazarian, High-pressure C02-expanded solvents Simultaneous measurement of C02 sorption and swelling of liquid polymers with in-situ near-IR spectroscopy. Journal of Physical Chemistry B, 2004. 108(37) p. 13995-13999. 

Sampling, sample handling, and storage and sample preparation methods are extensively covered, and modern methods such as accelerated solvent extraction, solid-phase microextraction (SPME), QuEChERS, and microwave techniques are included. Instrumentation, the analysis of liquids and solids, and applications of NMR are discussed in detail. A section on hyphenated NMR techniques is included, along with an expanded section on MRI and advanced imaging. The IR instrumentation section is focused on FTIR instrumentation. Absorption, emission, and reflectance spectroscopy are discussed, as is ETIR microscopy. ATR has been expanded. Near-IR instrumentation and applications are presented, and the topic of chemometrics is introduced. Coverage of Raman spectroscopy includes resonance Raman, surface-enhanced Raman, and Raman microscopy. 

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