Flexible carbon nanotube-based electrolyte-gated field-effect transistor for spermidine detection

In this work, we realized a flexible electrolyte-gated field-effect transistor (EG-FET) based on a spray-coated semi-conducting single-walled carbon nanotube (SWCNTs) network. The device was functionalized with anti-spermidine antibodies for a specific detection of polyamine spermidine - a well-known chemical indicator of food quality. The spray-coated SWCNTs films were modified with a bifunctional molecule, which binds to the nanotubes via non-covalent π−π interactions and leaves a free NHS-ester group for amide coupling of the antibodies, ensuring controlled immobilization. Transfer and output curves were recorded for device characterization, showing a typical p-type behavior with an on–off ratio of 190 A/A and a threshold voltage around 0 V. The calibration curve of the fabricated EG-FET immunosensor shows a linear detection range for spermidine from 0.001 to 100 nM, with 99.83% coefficient of determination.