Fluorinated Iron and Cobalt Phthalocyanine Nanowire Chemiresistors for Environmental Gas Monitoring at Parts-per-Billion Levels

Herein, a single-step production for the development of gas sensing devices from unsubstituted and hexadecafluorinated metal phthalocyanines (MPc, M = Fe2+ and Co2+) is explained. The preparation of sensor devices by the direct growth of nanowires on interdigitated electrodes by the vapor transport of the synthesized MPc precursors is discussed, emphasizing a single-step approach. Results using as-prepared devices for the detection of NH3 and NO2 in the ppb range are shown. In agreement with similar MPc sensing materials, response and recovery times fitted using a double-exponential model gave two rate constants: a short one, on the order of minutes for concentrations above 500 ppb, and a long one, on the order of hours. These rate constants are suitable for environmental monitoring of gases in recovery zones, where longer exposure times are critical in the sampling process. Our F16FePc-NW sensor prototypes show a ∼10% normalized response toward NH3 at 40 ppb for a measuring time of ∼2.5 h at room temperature and measurable responses to concentrations as low as 5 ppb, rendering them applicable to environmental studies.