| Quartz crystal microbalance (QCM) is a commonly used piezoelectric chemicalsensor that has a high sensitivity to the surface mass loading change. Usually,Sauerbery's Equation is used to estimate the mass change for a rigid, homogeneous andthin film. If a non-rigid film is deposited on the surface of the sensor, the response ofthe sensor can not be interpreted by Sauerbery's Equation. Hence, it is of interest toinvestigate the responses of piezoelectric sensor under the condition of non-rigid film.The results are helpful in the data treatments and new applications for the piezoelectricsensors. After reviewed the works in references, the following research works weredone in this dissertation.1．Influence of an immersion angle on the resonant frequency of a quartz crystalmicrobaiance with one side facing liquid.Since 2002, Japan scholar Yoshimoto has published six articles in Anal. Chem.,Anal. Chim. Acta. In the six articles, they report repeatedly the results of the influenceof an immersion angle on the resonant frequency of a quartz crystal microbaiance withone side facing liquid. The six articles are very similar and seem to be from onemanuscript. It is very serious that his experimental results can not be repeated in ourlaboratory. His relation is also wrong. In this work, the influence of an immersionangle on the resonant frequencies of QCMs with one side facing liquid was tested.Completely different experimental results were reported. The experimental resultsshow that the immersion angle is an added factor that may influence the frequency ofthe QCM sensor. This type of influence is caused by variation of the reflectioncondition of the longitudinal wave between the QCM sensor and the walls of thedetection cell. The frequency shifts, measured by varyingθ, are related to the QCMsensor used. When a QCM sensor with a weak longitudinal wave is used, its resonantfrequency is nearly independent ofθ. But, if a QCM sensor with a strong longitudinalwave is employed, the immersion angle is a potential error source for themeasurements performed on the QCM sensor. When the reflection conditions of the longitudinal wave are reduced, the influence ofθon the resonant frequency of theQCM sensor is negligible. The slope of the plot of frequency shifts (ΔF) versus (ρη)1/2 ,the square root of the product of solution density (ρ) and viscosity (η), may beinfluenced byθin a single experiment for the QCM sensor with a strong longitudinalwave in low viscous liquids, which can however, be effectively weakened by using theaveraged values of reduplicated experiments. In solutions with a large (ρη)1/2 region(0-55 wt% sucrose solution as an example, with p value from 1．00 to 1．26 g.cm-3 andηvalue from 0．01 to 0．22g.cm-1 .s-1 , respectively), the slope of the plot ofΔF versus(p?)1/2 is independent ofθeven for the QCM sensor with a strong longitudinal wave ina single experiment. The influence ofθon the resonant frequency of the QCM sensorshould be taken into consideration in its applications in liquid phase.2．Responses of QCM to viscosity of non-Newtonic liquidsWe investigated the responses of QCM to the viscosity of non-Newtonic liquidsbecause this kind of behavior is not reported in references. It. was shown that theenergy loss of a QCM in some high viscous non-Newtonic liquids was much less thanthat from the theory in Newtonic liquids. Thus, it may be possible to apply QCMsensors in high viscous macromolecule solutions. In this work, we measured theviscosity changes of a series of Newtonic and non-Newtonic liquids, including glycerin,sucrose, several surfactants, sodium carboxymethyl cellulose,glutin, polyacrylamides,polypropylene glycol and so on, by the motional resistance of QCM, Ubbloholeviscosimeter, rheometer. The typical results are reported.3．Monitor the adsorption of acetone vapor onto room temperature ionic liquid bya langasite crystal resonator.The responses of a Y-cut langasite crystal resonator (LCR) in liquid phases wereinvestigated by an impedance analysis method. The resonant frequency (fs) of the LCRdecreases with increasing mass loading on the active surface of the resonator. The LCRcan. be operated at the resonant frequency that is down to about 60% of thefundamental frequency (f0) under foreign mass loading. The frequency-mass coefficient of the Y-cut LCR is theoretically derived to be-1．282×10-6 ?02, which issupported by the experimental results. The resonant frequency of the LCR decreaseslinearly while its motional resistance (Rm) increases linearly with increasing (ρη)1/2 ,whereηandρare the viscosity and density of the liquid phase, respectively. Theslopes of the plots of fS versus (ρη)1/2 and Rm versus (ρ?)1/2 are related to the region of(ρη)1/2 because of the influence of surface roughness of the LCR. The changes inviscodensity of a room temperature ionic liquid (RTIL), 1-octyl-3-methylimidazoliumbromide ([C2MIM][Br]), were investigated in acetone vapor adsorption and ascendingtemperature processes by the LCR. The adsorption of acetone into [C8MIM][Br]causes a significant drop in viscosity of the [C8MIM][Br] film, which induces anincrease in fS and a decrease in Rm for the RTIL modified. When the thickness of[C8MIM][Br] film is less than the decay distance of the thickness-shear wave, a masseffect model is observed in the early adsorption process. Based on the responses of theLCR, the viscodensity of the [C8MIM][Br] film as well as the adsorbed amounts ofacetone into film were monitored in real time during the adsorption or desorptionprocesses.4．Investigation the adsorption characteristics of silane surface by piezoelectricsensorSilane reagent KH-500 was applied to make the surface of quartz crystal silanize.The silane surface of amidocyanogen terminal is positively charged and can adsorbanion surfactant, anion polyelectrolyte and protein with negative charge. Theadsorption is a mass increase process, which wan be monitored from the frequencydecrease of an electrode-separated piezoelectric sensor. The bound mass at silanesurface was monitored in real time by the piezoelectric sensors. |
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