Bis-porphyrin films as ppb level chemiresistive sensors

We present chemiresistive sensing characteristics of spin-coated thin films of newly synthesized bis-porphyrin molecules that involves anchoring of two porphyrins to a benzene ring at meta positions through ester-linkages. The bis-porphyrin films are very smooth (rms roughness <2 nm) and exhibit high charge mobility (1.8 cm2/V s). These films are found to be highly selective to Cl2 with fast response (3 s) and recovery (∼8 min) times, and sensitivity in the 10–500 ppb range varies linearly between 278% and 1370%. However, for concentrations ⩾1000 ppb, the response becomes irreversible, which is attributed to the chemical reaction between Cl2 and bis-porphyrin films.