The SiO2 gate of an ion-sensitive field-effect transistor, (ISFET), is functionalized with a TiO2 film that includes imprinted molecular sites for 4-chlorophenoxy acetic acid, (1), or 2,4-dichlorophenoxy acetic acid, (2). The functionalized devices that include the imprinted interfaces reveal an impressive selectivity in the sensing of the imprinted substrates Na+-1 or Na+-2. The detection limit for Na+-1 is (5 ± 2) × 10-4 M, which corresponds to 38 mV·dec-1 in the concentration range of 0.5 to 6 mM. The detection limit for the analysis of Na+-2 is (1.0 ± 0.2) × 10-5 M, which corresponds to 28 mV·dec-1 in the concentration range 0.1-9.0 mM. The equilibration time of the devices is ca. 5 min.
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