High performance conductimetric sensor for detection of trace triethylamine based on the metalloporphyrin 2D-conjugated polymer assisted with a phosphating strategy

Abstract

Porphyrin conjugated polymers (PorCPs) have emerged as next-generation semiconducting materials with pre-designed π-electronic skeletons and highly ordered topological structures, especially for gas sensing applications. In this study, two porphyrin conjugated polymers M-PorCPs (M = Fe and Co) with highly dispersed central metal active adsorption sites were prepared, and the band gaps of the M-PorCP were adjusted by phosphating process. Both M-PorCP and the resulted P @ M-PorCP are characterized by a wide range of methods including FT-IR, Raman, X-ray diffraction, SEM, TEM, UPS, UV–vis diffuse reflectance spectra, BET, and current–voltage (I–V) measurements. The experimental results indicate that subsequent phosphating improves electrical conductivity of the parent M-PorCPs by an order of magnitude (from ∼10−5 S cm−1 to 10−4 S cm−1) thanks to the smaller band gap of the resulted P @ M-PorCPs than their parent polymer M-PorCPs but the structures of polymer are maintained. Moreover, the sensing behavior of the both P @ M-PorCPs and M-PorCPs was investigated towards triethylamine (TEA) vapor in the 1–10 ppm range. High sensitive responses to TEA are obtained for the four sensors with the increasing degree in the order of Co-PorCP < Fe-PorCP < P @ Co-PorCP < P @ Fe-PorCP. The highest sensitivity (5.27%ppm−1) to the response of 1–10 ppm TEA was obtained for the P @ Fe-PorCP with a low limit of detection (LOD) of 0.17 ppm among the four sensors, which are attributed to larger specific surface area of its parent Fe-PorCP and importantly stronger N-Fe binding energy of TEA to FePor metal center at the air/Fe-PorCP interface relative to those of the Co-PorCP, combined with the highest electrical conductivity among the four sensors. Moreover, P @ Fe-PorCP also showed excellent selectivity, good repeatability and humidity stability. The present works not only represent the first example for TEA sensor based on porphyrin-based organic semiconductor materials, but importantly the sensing performances in terms of LOD and sensitivity for the P @ Fe-PorCP are superior to those of the TEA sensors based on inorganic semiconductor-based nanomaterials.