Enhancing EMF stability of solid-state ion-selective sensors by incorporating lipophilic silver-ligand complexes within polymeric films
✍ Scribed by Dong Liu; Ravi K. Meruva; Richard B. Brown; Mark E. Meyerhoff
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 761 KB
- Volume
- 321
- Category
- Article
- ISSN
- 0003-2670
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✦ Synopsis
The EMF stabilities of microfabricated ammonium and sodium ion-selective sensors prepared by incorporating a lipophilic silver-ligand complex and free iigand (either 1,3-(bis-phenylphosphine) propane (DPP) or thioether calix[4]arene (TDC)) along with appropriate ion-selective ionophores (nonactin or mcthylmonensin) within polymer films are examined. The sHver-ligand complex and free ligand are added to function as a reversible electron redox pair at a polymer film/conductor (Ag°-epoxy) interface. The resulting solid-state sensors exin'bit improved EMF ~ during the first 20 h of soaking in a solution of apalyte ion as well as over an extended 20-day period. Further, it is shown that the remaining initial EMF drift of the solid-state sensors, which results from water uptake by the film, can be further reduced by optimizing film plasficizers. With optimized plasticizer composition and a well-established electron transfer pair at the conductor/membrane interface, more stable potenfiometric responses are achieved. Impedance studies of the solM-state ion sensors support the existence of a reversible redox couple at the Ag°-epoxy/membrane interface.