Quartz crystal microbalance 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)... 

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. 

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). 

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]. 

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. 

As the readers may see, quartz crystal resonator (QCR) sensors are out of the content of this chapter because their fundamentals are far from spectrometric aspects. These acoustic devices, especially applied in direct contact to an aqueous liquid, are commonly known as quartz crystal microbalance (QCM) [104] and used to convert a mass ora mass accumulation on the surface of the quartz crystal or, almost equivalent, the thickness or a thickness increase of a foreign layer on the crystal surface, into a frequency shift — a decrease in the ultrasonic frequency — then converted into an electrical signal. This unspecific response can be made selective, even specific, in the case of QCM immunosensors [105]. Despite non-gravimetric contributions have been attributed to the QCR response, such as the effect of single-film viscoelasticity [106], these contributions are also showed by a shift of the fixed US frequency applied to the resonator so, the spectrum of the system under study is never obtained and the methods developed with the help of these devices cannot be considered spectrometric. Recent studies on acoustic properties of living cells on the sub-second timescale have involved both a QCM and an impedance analyser thus susceptance and conductance spectra are obtained by the latter [107]. 

We will first describe briefly the main experimental techniques coupled with electrochemical methods Infrared Reflectance Spectroscopy (IRS), Electrochemical Quartz Crystal Microbalance (EQCM), Differential Electrochemical Mass Spectrometry (DEMS), Chemical Radiotracers and High Performance Liquid Chromatography (HPLC). 

In this work we studied the regularities of a horseradish peroxidase (HRP) layer formation from its aqueous solutions on bare gold surface and that modified with a polyethyleneimine/polystyrene sulfonate bilayer using the quartz crystal microbalance (QCM) technique in liquid phase allowing to achieve highly sensitive mass detection and obtain information on viscoelastic properties of the adsorbed layers [3,4]. 

There has been remarkable progress in the development and application of the quartz crystal microbalance (QCM) principle in sensitive devices for the detection and concentration measurement of specific molecules in gaseous and liquid media [1]. Since the behavior of quartz crystal resonator (QCR) sensors in gases is similar to quartz crystals technically used as frequency standards, a large set of circuit configurations is available, whose known properties can merely be adapted to particular applications [2-5]. In many cases quartz crystals used in electronic circuitry, sometimes even from mass production, are employed. 

Probing the Solid/Liquid Interface with the Quartz Crystal Microbalance... 

Abstract In this chapter we discuss the results of theoretical and experimental studies of the structure and dynamics at solid-liquid interfaces employing the quartz crystal microbalance (QCM). Various models for the mechanical contact between the oscillating quartz crystal and the liquid are described, and theoretical predictions are compared with the experimental results. Special attention is paid to consideration of the influence of slippage and surface roughness on the QCM response at the solid-liquid interface. The main question, which we would like to answer in this chapter, is what information on... 

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