Measuring the Mass of Thin Films and Adsorbates Using Magnetoelastic Techniques

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• 作者：Rong Zhang ; M. Isabel Tejedor-Tejedor ; Craig A. Grimes ; Marc A. Anderson
• 刊名：Analytical Chemistry
• 出版年：2007
• 出版时间：September 15, 2007
• 年：2007
• 卷：79
• 期：18
• 页码：7078 - 7086
• 全文大小：206K
• 年卷期：v.79,no.18(September 15, 2007)
• ISSN：1520-6882

文摘

Magnetoelastic sensor techniques have the unique characteristics of being able to wirelessly detect resonantfrequency shifts of a magnetoelastic foil in response todifferences in the foil mass. However, the mathematicalexpression that links the resonant frequency shift with thechange in the mass of the magnetoelastic foil is rarelyreported. Furthermore, this relationship is not easy toascertain due to potential changes in the Young's modulusof the sensor upon a change in mass loading. In thispaper, we have shown that adsorption of water vapor fromthe gas phase by magnetoelastic ribbons coated with a twolayer porous thin film (SiO₂/Pt-TiO₂) induces largechanges in the effective Young's modulus of the sensor.We also demonstrated that the change in Young's modulus upon mass loading can be eliminated from therelationship between mass loading and shifts in resonantfrequency by using a technique that we refer to as the twodifferent length sensor method (TDLS). This methodologypermits the conversion of the magnetoelastic sensor intoa microbalance. From data presented in this paper, weillustrate that the sensitivity for the same sensor can rangebetween 214 Hz/mg for mass loadings of Au to 438 kHz/mg for acetone. In the case of water adsorption, frequencyshifts varies from 20.0 kHz/mg when m 0.01 mg to2.00 kHz/mg for m values between 0.05 and 0.10 mg.