Tailored chemosensors for chloroaromatic acids using molecular imprinted TiO₂ thin films on ion-sensitive field-effect transistors

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.