Room temperature ammonia sensor based on jaw like bis-porphyrin molecules

A jaw-like bis-porphyrin (bis-TPP) molecule was synthesized anchoring of two porphyrin molecules to a benzene ring at the meta positions through the ester linkage. The bis-TPP molecule and its zinc-derivative (Zn-bis-TPP) were spin-coated on glass surfaces to construct two chemiresistive room temperature NH3 gas sensors. Both the films showed high selectivity, reproducibility and reversibility in sensing NH3 gas (5–40 ppm) in air. The sensing characteristics of the Zn-bis-TPP films (response (2 s) and recovery (2.5 min) times; linear response (952%)) were better than that of the bis-TPP films (response (8 s) and recovery (7.5 min) times; linear response (131%)). This is attributed to the amorphous nature of the former.

Graphical abstractWe have constructed two highly selective ammonia gas (5–40 ppm) thin film sensors by spin coating a bis-porphyrin (bis-TPP) and its zinc derivative as the active layers. Both the sensors functioned at room temperature reversibly and showed fast response, the Zn-bis-TPP films being more efficient.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Demonstration of two bis-porphyrin-based spin-coated thin-film chemi-resistive room temperature NH3 gas (ppm) sensors. ► Fast and long range of linear response, complete recovery and high selectivity of the sensors. ► Better performance by the Zn–bisporphyrin films due to their rough nature and free entry and exit of NH3 gas.