Solution processed films and nanobelts of substituted zinc phthalocyanine as room temperature ppb level Cl2 sensors

• Room temperature ppb level Cl2 sensing characteristics of highly selective ZnPc(OBu)8 thin film and nanobelts.
• Fabrication of nanobelts by cost effective self-assembly technique.
• ZnPc(OBu)8 film as well as NBs are highly sensitive to Cl2 with response of 522% and 655% in 25 s and 15 s, respectively.
• Adsorption of Cl2 gas on film samples obeys Elovich equation.
• Predominant sites of interaction of Cl2 gas are Zn ions.

Room temperature Cl2 sensing characteristics of highly selective spin coated Zn (II) 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (ZnPc(OBu)8) film and self-assembled nanobelts (NBs) have been studied in the concentration range of 5–1500 ppb. UV–Visible absorption spectroscopic studies indicate the formation of J-type aggregates in case of ZnPc(OBu)8 film and H-type aggregates in NBs. The electrical conductance of NBs is found to be 60% more than ZnPc(OBu)8 film. For 1500 ppb of Cl2, the response of ZnPc(OBu)8 film and NBs is 522% and 655% with a response time of 25 s and 15 s, respectively. The detection limit of ZnPc film is lowered from 50 ppb to 5 ppb by making butoxy substitution. X-ray photoelectron spectroscopic studies reveal that absorption sites predominantly are the central metal ions of ZnPc(OBu)8 molecules. The results obtained are compared with Cl2 sensing characteristics of unsubstituted ZnPc film to show the effect of butoxy substitution and NBs formation.