Improving selectivity of ion-sensitive membrane by polyethylene glycol doping

•Reduction of interference from hydrophobic ions by doping PEG into sensing membrane.•More than 10 times improvement in selectivity coefficient for Na+ detection.•Greatly expanded range in multiplexed detection of Na+ and MB+ on SiNW-ISFET array. Hydrophobic ions can generate considerable interference to ion detection in a complex analyte with membrane-based ion-selective sensors, due to the hydrophobic interaction. In this paper, we demonstrate that the interference from the hydrophobic interaction to the sensors can be significantly reduced by incorporating hydrophilic polyethylene glycol (PEG) into the membrane. The sensor is a silicon nanowire field-effect transistor (SiNWFET) with its surface functionalized with an ionophore-doped mixed-matrix membrane (MMM), where the ionophore is either a commercial Na-ionophore Ⅲ or a novel synthetic metal-organic supercontainer. The incorporation of PEG suppresses the partitioning of hydrophobic ions into the MMM and thus reduces their interference to the detection of target ions. This is evidenced with an improvement in selectivity for Na+ detection in the presence of interfering methylene blue (MB+) ion by more than an order of magnitude. It further enables detection of Na+ and MB+ using a SiNWFET sensor array in a multiplexed manner with controlled susceptivity to cross-interference and a greatly expanded dynamic range.