Mixed Langmuir–Blodgett monolayers containing carboxylic ionophores. Application to Na+ and Ca2+ ISFET-based sensors

Novel ISFET devices coated with ultrathin membranes are suitable for cation detection in liquids. Deposition of Na+-ion and Ca2+-ion sensitive Langmuir–Blodgett films onto ISFET surfaces has been achieved. In this work, we present first experimental results about ISFET devices coated with LB mixed films. The sensitive material is a carboxylic ionophore (monensin or calcimycin) included in a phospholipid matrix. The sensors showed a linear response with a slope of 19 mV/pNa in the range 10−2/10−6 mol/l and a slope 23 mV/pCa in the range of 10−2/10−4 mol/l. The results have demonstred the transferability of mixed films onto structured semiconductor devices like ISFETs. This response let us expect further improvements.