Long period gratings coated with syndiotactic polystirene as highly sensitive chemical sensors

In this work, a novel fiber optic sensor able to measure the concentration of organic analytes, in aqueous environment is presented. Long period gratings were selected as high sensitive refractive index transducers and syndiotactic polystyrene in the nanoporous crystalline δ form was used as sensitive polymeric layer due to its high sorption properties towards chlorinated and aromatic compounds. In particular, a thin semi-crystalline syndiotactic polystyrene film with crystalline nanoporous δ form was deposited along the sensing element by using dip-coating technique. Chemical detection has been carried out by measuring the wavelength shift and the amplitude change in the attenuation bands of the long period grating due to analytes sorption. Experimental results demonstrate the capability of the proposed sensor to detect very low concentrations (in the range of few ppm) of chloroform in water.