Quartz crystal AT-cut

Fig. 6.1 Natural frequency as a function of temperature in an AT cut quartz crystal...

Schafer and coworkers [23] developed a QCM-IL sensor for use as an artificial nose using the ubiquitous [C4Cilm][PFg]. The IL was spin coated onto the surface of a 10 MHz AT-cut quartz crystal with gold electrodes. The work specifically studied the response of the sensor to ethyl acetate. The deposition of the IL on the surface of the electrode decreased the resonance frequency of the QCM by 2017 Hz. Exposure to increasing amounts of ethyl acetate vapor produced a linear increase in frequency, which was attributed to a progressive decrease in viscosity of the IL upon adsorption of the analyte. The response time, given as the time to full saturation of the... 

For AT-cut quartz crystals operating in the shear mode, the oscillation frequency, /o, is inversely proportional to the thickness d of the crystal, as described by the following equation ... 

An AT-cut quartz crystal having base frequency of 8 MHz (Sunny Electronics Co., Korea) is utilized to prepare the sensor. The electrode of the crystal is silver finished. Two... 

Measurements were performed using a 24-channel acoustic-wave sensor array system shown in Fig. 19.3. The sensor system was arranged on two printed circuit boards (Fig. 19.3a). One circuit board contained sensor resonators arranged as a 6 x 4 array (Fig. 19.3b), compatible with available 24-well plates with 16-mm well diameter and positioned onto a Z-stage. Sensor resonators were 8-mm diameter polished AT-cut quartz crystals and operated at 20MHz. The crystals had 3-mm diameter Au electrode plated in the center of each face of the crystal. The mass resolution for a 20-MHz crystal was lOng. 

A review appeared on piezoelectric quartz crystals used as detectors for phenols in air, after coating with Triton X-100 and 4-aminoantipyrine (78), or with activated carbon cloth impregnated with various compounds, such as poly(vinyl pyrrolidone). A piezoelectric sensor was proposed for determination of trace amounts of phenol and alkylphenols in air. The problems attaining selectivity of the adsoption membranes and operating conditions were addressed . An AT-cut quartz crystal, coated with a hydrophobic PVC layer and operating in the thickness shear mode, has been used to detect 4-aminophenol, after conversion to a hydrophobic indophenol dye and adsorption on the polymer layer. The mode of preparation of the PVC coating affects the sensitivity of the detector , a... 

Acoustic wave devices, also known as shear mode resonating quartz crystal microbalances, employ an AT-cut quartz crystal operating in a shear mode for transduction of ssDNA-cDNA hybridization events. This transduction is monitored as mass change... 

The most used devices in biosensors are generally bulk acoustic wave (BAW)-based employing AT-cut quartz crystals. 

The plot of impedance Z = R+jX with R = Rg and X = j(coLs - ) is shown in terms of impedance magnitude, Z = y/R +X, and phase, tan cp = X/R in Fig. 9. The values given in Table 1 for a 10 MHz AT-cut quartz crystal have been taken for computation. The quartz impedance is inductive (phase shift + 90°) between/s and/p, and capacitive (phase shift -90°) outside this interval. The phase shift is very steep. 

Fig. 1 Typical sensorgram recorded with a 10 MHz AT-cut quartz crystal coated with gold electrodes, during a hybridization cycle between the immobilized probe and the target oligonucleotide in solution. The frequency spikes are due to the replacement of the different solutions by pipetting...

Fig.l The QCM principle. An applied voltage over an (AT-cut) quartz crystal induces a shear strain in the quartz. The direction of the strain depends on the polarity of the applied field, which means that a mechanical resonance can be excited if the frequency of the applied voltage generates a standing wave with antinodes at the crystal s interfaces... 

Fig. 9 REVS assay. A An AT-cut quartz crystal was coated successively with a chromium layer, a gold layer, a chemical linker layer, and a receptor that mediated specific attachment of the particle. The crystal was then transversely oscillated by applying a RE voltage at the main resonant frequency to the gold electrodes on either side of the disc. B Increasing the applied voltage results in a transverse oscillation of greater amplitude which, in principle, leads to greater inertial forces between the particle and the surface and concomitant deformation of the surface and the particle. Ultimately the bond between particle and receptor surface breaks and vibrations in the quartz are excited. These vibrations can be detected by using the quartz as a sensitive microphone. Note that the figures are not to scale...

Finally, a continuous flow cell system was designed, and a comprehensive analysis of the interaction between an 11-MHz AT-Cut quartz crystal and viscous liquids was studied (98). The derived equation was basically identical with that reported earlier (94,95) assuming that the solution height is sufficiently large. 

Piezoelectric sensors are generally based on the use of AT-cut quartz crystals (+ 35°15 orientation of the plate relative to the crystal plane) because of their excellent temperature coefficients [3]. The generated acoustic wave depends on the crystal cut, thickness of the material used, and the geometry and configuration of the metal electrodes used to produce the electric field [5]. 

The QCM crystals used in this study are 1 inch diameter, AT-cut quartz crystals with thicknesses adjusted so drat di have resonant frequencies near 5 MHz (Valpey-Fisher). The central region of die crystal is sandwiched between two vapor deposited gold electrodes of ca. 300 nm thkkness widi a ca. 30 nm layer of Or applied prior to the gold to promote adhesion to die quartz substrate. A diagomiatical representation of die crystal is shown in Rgure 2. The area of die central, circular pad (i.e. the area of the crystal which is sandwiched between die gold electrodes) is 0.28 cm. This is die piezoelectrically active area of the crystal, a only mass changes which occur there are sensed by the QCM. 

Generally, on the basis of the above compromises, the operating frequency is in the range 5 to 10 MHz. For resonators using AT-cut quartz crystals with /o = 10 MHz, the Sauerbrey equation reduces to... 

Fig. 9 Calibration experiment for a combined EQCM/PBD instrument, using the electrodeposition of Ag. Panels (a), (b), and (c), respectively, show current, mass change, and beam deflection responses to a cyclic voltammetric experiment (scan rate 20 mV s ). Working electrode Au (area 0.22 cm ) on a 10-MHz AT-cut quartz crystal. Probe beam 633 nm He-Ne laser parallel to Au electrode at a distance of 155 pm. Solution 1 mmol dm AgNO3/0.2 mol dm HCIO4. (Reproduced from Ref [43] with permission from Elsevier.)...

Fig. 15 Mass changes of Zn films at open-circuit potential exposed to new (full line) and used (dash-dot line) alkaline cleaning solution. Electrodes Zn film on Au (with Cu overlayer) supported on 10-MHz AT-cut quartz crystal. Solution RIDOLINE industrial alkaline cleaner, pH 12.43. Temperature 316 K. (Reproduced from Ref [92] with permission from the Royal Society of Chemistry.)...

Fig. 16 Data from a voltammetric deposition study of the Cu2 xSe system (a) current versus potential and (b) frequency change versus charge plots. Electrode Au (area = 0.236 cm ) on 5-MHz AT-cut quartz crystal. Solution 50 mmol dm CuCi + 1 mmol dm Se02 + 4 mol dm KSCN/pH 3. Potential scan rate 10 mV s (Reproduced from Ref [103] with permission from Elsevier.)...

Fig. 17 Current (left panel) and mass change (right panel) responses during the first redox cycle of Prussian Blue films (deposition charge 10 mC cm ). Electrodes Au (area = 0.32 cm ) on 6-MHz AT-cut quartz crystals. Solution 0.5 mol dm KNO3 in H2O (full lines) or D2O (dotted lines). Potential scan rate 10 mV s T (Reproduced from Ref [108] with permission from Elsevier.)...

Fig. 19 Mass change versus charge plots for redox cycling under voltammetric conditions of a polythionine film (f = 13.8 nmol cm ) in aqueous acetate solution. Electrode Au (area = 0.23 cm ) on 10-MHz AT-cut quartz crystals. Solution 0.1 mol dm total acetate, buffered to pH 4.5. Potential scan rates 5 ( ), 50 (A), 100 ( ) mV s (Reproduced from Ref [124] with permission from the American Chemical Society.)...

Fig. 21 Changes in resonant frequency (panel A) and resonant resistance (panel B) for a poly(vinylferrocene-co-/ /-isopropylacrylamide) film (VF NIPAA = 1 13 dry film thickness ca. 5 pm) as a function of temperature, with the film maintained in the reduced state ( = 0.0 V dashed line) and in the oxidized state (E = 0.5 V full line). Electrode Pt (area = 0.2 cm ) on 9-MHz AT-cut quartz crystal. Solution 0.1 moldm NaCl04. Temperature scanned from 35 to 10 °C over the course of ca. 1 h. (Reproduced from Ref [137] with permission from the American Chemical Society.)...

Fig. 24 Variation of EQCM resonant frequency with simultaneously ellipsometrically determined film thickness during deposition of polyaniline. Electrode Ron 5-M Hz AT-cut quartz crystal. Solution ...

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