Quartz crystal liquids

Fundamental frequency of the resonator Correlation function for surface roughness Root mean square height of a roughness Wave vector of shear waves in quartz, (Uy pq//rq Correlation length of surface roughness Thickness of the liquid film Thickness of interfacial layer Molecular dynamics Pressure in a liquid Quartz crystal microbalance Hydrodynamic roughness factor Electrochemical roughness factor Coordinates (normal and lateral)... 

Figure 8.28 shows how the X-rays fall on the solid or liquid sample which then emits X-ray fluorescence in the region 0.2-20 A. The fluorescence is dispersed by a flat crystal, often of lithium fluoride, which acts as a diffraction grating (rather like the quartz crystal in the X-ray monochromator in Figure 8.3). The fluorescence may be detected by a scintillation counter, a semiconductor detector or a gas flow proportional detector in which the X-rays ionize a gas such as argon and the resulting ions are counted.

Film-forming chemical reactions and the chemical composition of the film formed on lithium in nonaqueous aprotic liquid electrolytes are reviewed by Dominey [7], SEI formation on carbon and graphite anodes in liquid electrolytes has been reviewed by Dahn et al. [8], In addition to the evolution of new systems, new techniques have recently been adapted to the study of the electrode surface and the chemical and physical properties of the SEI. The most important of these are X-ray photoelectron spectroscopy (XPS), SEM, X-ray diffraction (XRD), Raman spectroscopy, scanning tunneling microscopy (STM), energy-dispersive X-ray spectroscopy (EDS), FTIR, NMR, EPR, calorimetry, DSC, TGA, use of quartz-crystal microbalance (QCMB) and atomic force microscopy (AFM). 

SJ. Martin, V.E. Granstaff, and G.C. Frye, Characterization of a quartz crystal microbalance with simultaneous mass and liquid loading. Anal. Chem. 63, 2272-2281 (1991). 

Slip is not always a purely dissipative process, and some energy can be stored at the solid-liquid interface. In the case that storage and dissipation at the interface are independent processes, a two-parameter slip model can be used. This can occur for a surface oscillating in the shear direction. Such a situation involves bulk-mode acoustic wave devices operating in liquid, which is where our interest in hydrodynamic couphng effects stems from. This type of sensor, an example of which is the transverse-shear mode acoustic wave device, the oft-quoted quartz crystal microbalance (QCM), measures changes in acoustic properties, such as resonant frequency and dissipation, in response to perturbations at the surface-liquid interface of the device. 

Liang, C., Yuan, C.Y, Warmack, R.J., Barnes, C.E., and Dai, S., Ionic liquids A new class of sensing materials for detection of organic vapors based on the use of a quartz crystal microbalance. Anal. Chem., 74,2172-2176, 2002. 

Shafer, T., Di Francesco, F., and Fuoco, R., Ionic liquids as selective depositions on quartz crystal microbalances for artificial olfactory systems A feasibility study, Microchem. ]., 85, 52-56, 2007. 

Goubaidoulline, L, Vidrich, G., and Johannsmann, D., Organic vapor sensing with ionic liquids entrapped in alumina nanopores on quartz crystal resonators. Anal. Chem., 77,615-619,2005. 

Baltus, R. E. et al.. Low-pressure solubility of carbon dioxide in room-temperature ionic liquids measured with a quartz crystal microbalance, J. Phys. Chem. B, 108, 721,2004. 

Acoustic Wave Sensors. Another emerging physical transduction technique involves the use of acoustic waves to detect the accumulation of species in or on a chemically sensitive film. This technique originated with the use of quartz resonators excited into thickness-shear resonance to monitor vacuum deposition of metals (11). The device is operated in an oscillator configuration. Changes in resonant frequency are simply related to the areal mass density accumulated on the crystal face. These sensors, often referred to as quartz crystal microbalances (QCMs), have been coated with chemically sensitive films to produce gas and vapor detectors (12), and have been operated in solution as liquid-phase microbalances (13). A dual QCM that has one smooth surface and one textured surface can be used to measure both the density and viscosity of many liquids in real time (14). 

In 1892, Biot confirmed that the colors on propagating white light parallel to the optical axis of a quartz crystal placed between crossed polarizers arise from two distinct effects, the rotation of the plane of polarization of monochromatic light and dispersion of the rotation with respect to wavelength. Biot s discovery was extended to the optical rotation of natural products in solution or in the liquid phase, and this is of chemical significance, as it indicates that rotation is a molecular effect. 

Endres et al. [82] have demonstrated the suitability of an air- and water-stable ionic liquid for the electropolymerization of benzene. This synthesis is normally restricted to media such as concentrated sulfuric acid, liquid SO2 or liquid HF as the solution must be completely anhydrous. The ionic liquid used, l-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, can be dried to below 3 ppm water, and this ionic liquid is also exceptionally stable, particularly in the anodic regime. Using this ionic liquid, poly(para-phenylene) was successfully deposited onto platinum as a coherent, electroactive film. Electrochemical quartz crystal microbalance techniques were also used to study the deposition and redox behavior of the polymer from this ionic liquid (Section 7.4.1) [83]. 

Quartz crystals have a characteristic oscillation frequency which varies according to their mass. Although crystal wafers have been used as mass sensors in vacuum and gas-phase experiments for many years, it is only recently that they have been employed in contact with liquids or solutions. Quartz crystal wafers can be used as electrodes by depositing a thin film of electrode material on the exposed surface, and interfacial mass changes can then be monitored. It is then known as the electrochemical QCM or EQCM. It is a direct, but non-selective, probe of mass transport. 

Since the early work of Kanazawa [1] and Bruckenstein in 1985 [2], quartz crystal resonators have been used for more than 12 years in contact with liquids to assess changes in mass during electrochemical surface processes. Extensive use of the electrochemical quartz crystal microbalance (EQCM) has been done in the study of electrode processes with change of mass simultaneous to charge transfer. 

In addition to mass changes at the quartz crystal surface and, liquid density and viscosity the resonant frequency can be affected by several other factors such as the liquid conductivity [10], the hydrostatic pressure... 

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