Membrane chemically switchable

The immobilization of photoisomerizable host molecules immobilized onto an electrode surface can be used for the construction of novel ion-selective electrodes. A photoisomerizable calix[4]arene derivative was incorporated into a polymeric membrane on an electrode surface and the two different isomeric states of the host molecule provided responses selective to Li+ or Na+ ions depending on the state [102], Another photoisomerizable host molecule was constructed from spiropyran and crown-ether subunits [103]. Different binding affinities for Li+ were found depending on the isomeric state of the photoisomerizable component (54). The researchers suggested that this effect was caused by the coordination of the Li+ ion to the CT of the zwitterionic merocyanine form (Fig. 29). The photocontrolled host molecules were immobilized in a polymeric film onto an electrode surface resulting in a photo chemically switchable ion-selective electrode. 

Nishizawa, M. Menon, V. R Martin, C. R. Metal nanotubule membranes with electro-chemically switchable ion-transport selectivity. Science 1995, 268, 700. 

Burgmayer P and Murray R W 1984 Ion Gate Electrodes. Polypyrrole as a switchable ion conductor membrane J. Phys. Chem. 88 2515-21 Otero T F and de Larreta E 1988 Conductivity and capacity of polythiophene films impedance study J. Electroanal. Chem. 244 311-18 Sunde S, Hagen G and Odegird R 1993 Impedance analysis of the electrochemical doping of poly(3-methyl-thiophene) from aqueous nitrate solutions J. Electroanal. Chem. 345 59-82 Zaborsky O R 1973 Immobilized Enzymes (Cleveland, OH Chemical Rubber Company) (see especially pp 69,87)... 

Fig. 2 The signal-responsive membrane associated with an ITO electrode and coupled with the enzyme-based logic gates. (A) AFM topography images (10x10 pm ) of the membrane with the closed (a) and open (b) pores. (B) The electron transfer resistance, / et, of the switchable interface derived from the impedance spectroscopy measurements obtained upon different combinations of the input signals. The right and left bars correspond to the OR-Reset and AND-Reset systems, respectively. (Adapted from ref. 83, with permission Copyright American Chemical Society, 2009).

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