FET-based sensors with robust photosensitive polymer membranes for detection of ammonium ions and urea

The properties of a potentiometric held effect transistor (FET)based sensor with a robust polymer photo- and ion-sensitive membrane were studied. The membrane was fabricated from polyethylene terephthalate (PETPh) film modified by spiropyran (SP) and nonactin (NA) using the crazing method. This method makes it possible to impregnate local polymer defects with low molecular weight substances. The presence of spiropyran in the membrane upon the UV-irradiation provides the generation of membrane photopotential, whose value in the presence of NA becomes a function of NH4+ concentration in the solution. The sensor was shown to have the optimal working range 10(-6)-10(-4) M for NH4+ (pH 5.0 1mM LiH2PO4) and 10(-5) -10(-3) M (pH 6.4, 10 mM LiH2PO4) for urea with immobilized urease as a catalyst.