Self-assembling and coordination of water nano-layers on polymeric coated long period gratings as promising tool for cation detection

In this work, polymeric coated Long Period Gratings (LPGs) working in transition mode have been used to monitor the coordination and self assembling of water nano layers providing new scenarios in chemical sensing applications. In particular, nano-scale layers of syndiotactic and atactic polystyrene (sPS and aPS) have been deposited by dip - coating onto LPGs to tune the devices at the transition point. Experimental results demonstrate the polymers capability to orient water molecules in proximity of their surfaces. The sPS and aPS interactions with water have been compared. Moreover, the high sensitivity of the coated LPGs was used to monitor the effect of disorder induced by different cations depending on their size and electrical charge. Experimental results show for the first time that, thanks to the water - polymer interaction, sPS coated LPGs could be successfully employed as high sensitivity cation sensors.