Chemical detection phosphonate sensors

For the detection of ionic species other than protons, it is necessary to introduce receptor molecules which can selectively bind guest species on top of the gate of the ISFET. Direct attachment of ion-selective moieties to the surface, e.g. by silylation with (3-cyanopropyl)dimethyl(dimethylamino)silane resulted in some sensitivity towards Ag+ ions (20 mV decade" ), but the sensor was still sensitive towards protons (15 mV decade" ) [10]. Chemical grafting with ammonium phosphonate (1-3) and phosphate sites (4) (Figure 2) or with phthalocyanine-based ionophores bearing crown-ether moieties resulted in a sensitivity towards alkaline (earth) ions, but the pH dependency remained [11,12]. 

Huang J, Miragliotta J, Becknell A, Katz HE (2007) Hydroxy-terminated organic semiconductor-based field-effect transistors for phosphonate vapor detection. J Am Chem Soc 129 9366-9376 Janata J, Josowicz M (1998) Chemical modulation of work function as a transduction mechanism for chemiceil sensors. Acc Chem Res 31 241-248... 

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