Size-Selective FET Sensors Based on Semiconducting Single-Walled Carbon Nanotubes and Metal–Organic Frameworks

This study presents a universal method for fabricating size-selective, liquid-gated field-effect transistor (FET) sensors using semiconducting single-walled carbon nanotubes (scSWCNTs) combined with metal-organic frameworks (MOFs) and poly(vinylidene fluoride) (PVDF) polymer barriers. By employing a layer-by-layer architecture, scSWCNTs were coated with a single layer of MOF crystals followed by a PVDF thin film, which restricts the access to scSWCNTs to only through MOF pores. This design enables a gate capacitance modulation mechanism, where only analyte molecules small enough to enter the MOF pores can modulate the scSWCNT conductance. Four MOFs, namely UiO-66, UiO-67, ZIF-8, and MIL-96, were fabricated into the scSWCNT/MOF/PVDF FET sensors and tested for their sensing capabilities toward norfentanyl (NF) and dopamine (DA) in 0.1 M KCl solution. UiO-67 devices showed positive responses to NF due to favorable pore size matching, while devices fabricated with other MOFs exhibited negative responses due to pore size exclusion. Tests with DA also confirmed the size-selective sensing abilities of the sensors. Long-term stability tests revealed that weak interactions between MOFs and PVDF limit the sensor durability in aqueous solution. Despite this limitation, the proposed approach shows considerable potential for constructing diverse size-selective sensors that enhance specificity and selectivity in scSWCNT/MOF/polymer sensing platforms.