Piezoelectric pH sensors

AT-cut quartz resonators with amphoteric polymer films

Juan Wang, Michael Ward, Richard C. Ebersole, Robert P. Foss

Research output: Contribution to journalArticle

Abstract

Piezoelectric AT-cut quartz resonators immersed in aqueous media, coated with cross-linked films of the random copolymer-{[CH2CH(CO2H)]a-[CH 2C(CH3)(CO2CH3)] b-[CH2C(CH3)(CO2CH 2CH2NMe2)]c}n (1), exhibit large frequency changes when the pH is changed in the vicinity of the isoelectric point of the polymer film. The frequency changes are attributed to changes in the viscoelastic properties of the films that occur during phase transitions between the isoelectric form and the cationic polymer ( 1-NMe2H+) present at low pH or the anionic polymer (1-CO2-) present at high pH. These phase transitions are accompanied by dramatic changes in acoustic energy attenuation, film thickness changes, and film surface energy, as indicated by acoustic impedance analysis, phase measurement interferometric microscopy, and contact angle measurements. The results are consistent with pH-dependent segregation of the isolectric and ionic phases within the bulk and between the bulk and the surface. The unique pH-sensing capabilities of the coated resonators, combined with their robustness, ease of fabrication, and low cost, provide a convenient approach for the measurement of "threshold" pH changes. Real-time measurements of enzymatic activity and microbe metabolism are demonstrated as examples of potential applications of these sensors.

Original languageEnglish (US)
Pages (from-to)2553-2562
Number of pages10
JournalAnalytical Chemistry
Volume65
Issue number19
StatePublished - Oct 1 1993

Fingerprint

pH sensors
Quartz
Polymer films
Resonators
Polymers
Phase transitions
Acoustic impedance
Phase measurement
Angle measurement
Time measurement
Interfacial energy
Metabolism
Contact angle
Film thickness
Microscopic examination
Copolymers
Acoustics
Fabrication
Sensors
Costs

ASJC Scopus subject areas

  • Analytical Chemistry

Cite this

Piezoelectric pH sensors : AT-cut quartz resonators with amphoteric polymer films. / Wang, Juan; Ward, Michael; Ebersole, Richard C.; Foss, Robert P.

In: Analytical Chemistry, Vol. 65, No. 19, 01.10.1993, p. 2553-2562.

Research output: Contribution to journalArticle

Wang, J, Ward, M, Ebersole, RC & Foss, RP 1993, 'Piezoelectric pH sensors: AT-cut quartz resonators with amphoteric polymer films', Analytical Chemistry, vol. 65, no. 19, pp. 2553-2562.
Wang, Juan ; Ward, Michael ; Ebersole, Richard C. ; Foss, Robert P. / Piezoelectric pH sensors : AT-cut quartz resonators with amphoteric polymer films. In: Analytical Chemistry. 1993 ; Vol. 65, No. 19. pp. 2553-2562.
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