Two-dimensional conducting polymers: synthetic strategies and emerging applications in sensor technologies

Abstract

Two-dimensional conducting polymers (2DCPs) are characterized by suppressed chain entanglement and interchain disorder, enabling continuous in-plane charge transport, enhanced specific surface area, and retained mechanical compliance. This review provides a structured overview of interfacial synthesis, space-confined growth, template-assisted synthesis, epitaxial polymerization, and self-assembly. The focus is placed on their mechanisms for achieving precise thickness control, high crystallinity, and long-range order. Interfacial routes (air/liquid, liquid/liquid, solid/liquid, quasi-liquid ice layers) afford monolayer-to-multilayer films with diffusion-limited crystallization and wafer-scale continuity, while surfactant monolayers enforce pre-organization. Space confinement within layered hosts (FeOCl, MXenes, layered double hydroxides, and montmorillonite) acts as 2D nanoreactors to direct intercalation, chain alignment, and lamellar superlattices. Template‑assisted approaches program pore architecture and lateral order using hard/soft templates and vapor routes. Epitaxial strategies on graphene and MnOx templates leverage lattice matching, π-π stacking, and interfacial bonding to planarize backbones. Moreover, acid-modulated self-assembly unlocks free-standing PEDOT:PSS nanosheets with enhanced order and stiffness. These structural controls translate into sensor performance. Gas sensors achieving 10 ppt NH3 detection with fast response. Pressure/distance devices exploiting quasi-2D anisotropy for high sensitivity and stability. Electrochemical platforms deliver broad linear ranges and low detection limits, including chiral recognition and enzyme-free detection. Leveraging their unique combination of intrinsic in‑plane charge transport, molecular programmability, and mechanical compliance, 2DCPs are poised to serve as foundational materials for next‑generation flexible and bio‑integrated sensors. In particular, these materials enable miniaturized, low‑noise, and energy‑efficient platforms for healthcare monitoring, human–machine interfaces, and distributed environmental sensing.