Highly selective room temperature NO2 detection via π-back bonding in CuTPP-functionalized conductive polymer sensors

Abstract

Nitrogen dioxide (NO₂), primarily emitted from transportation and industrial activities, poses significant threats to human health and environmental safety. However, reliable, repeatable, highly selective, and sensitive detection of NO₂ at room temperature remains challenging. In biological systems, metalloporphyrins are well known for their essential roles in gas transport, storage, and as catalytic centers in enzymatic redox reactions, demonstrating highly refined molecular recognition capabilities. Inspired by these unique gas-metal porphyrin interactions, we incorporated copper tetraphenylporphyrin (CuTPP) into a conductive polymer composite consisting of polyaniline (PANI) and Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) to construct a high-performance NO₂ sensor operating at room temperature. Upon exposure to NO₂, Cu²⁺ ions in CuTPP selectively adsorb NO₂ via a non-classical π-back bonding mechanism, which not only ensures high selectivity but also significantly facilitates charge transfer pathways centered around CuTPP, greatly enhancing electron extraction from PANI. For sensor recovery, ultraviolet (UV) was employed to promote the desorption of NO₂. The developed sensor exhibits excellent linearity (R² > 0.97) within an NO₂ concentration range of 0.2–1 ppm, and achieves a theoretical detection limit of approximately 0.4 ppb, suitable for monitoring concentrations of NO₂ in environmental settings. By exploiting the non-classical π-back bonding interaction between CuTPP and NO₂ within a conductive polymer matrix, our approach provides a versatile and low-power strategy for precise NO₂ detection, with potential applications in environmental monitoring and assessment.