A MESOMORPHIC AMPHIPHILIC PHTHALOCYANINE DERIVATIVE USED FOR THE FUNCTIONALIZATION OF THE GRID SURFACE OF A FIELD-EFFECT TRANSISTOR

A phthalocyanine subunit substituted with four hydroxy- and four metho xy-terminated polyoxyethylene sidechains has been synthesized. Optical microscopy and X-ray diffraction at small angles demonstrate the form ation of a birefringent non-crystalline phase. The reaction of the ter minal hydroxy groups with methacryloyl chloride affords an amphiphilic photopolymerizable phthalocyanine derivative. This latter has been re acted with the grid surface of a held effect transistor (FET) previous ly treated with (trimethoxysilyl)propyl methacrylate. The photo-copoly merized membrane has been shown to be approximately 360 Angstrom thick by atomic force microscopy (AFM). The covalently linked polyoxyethyle ne phthalocyanine derivative has been used as an ion complexing membra ne in an ion selective held effect transistor (ISFET). The ISFET chara cteristics have been determined in water and in a methanol-water mixtu re (90 :10; v: v) for Na+ and K+. The pH sensitivity of the device has also been measured. The experimental results have been compared with theoretical ones. The model allowed us to determine the total number o f binding sites (N-TOT) and the corresponding ion-site complexation co nstants.