CNTs based improved chlorine sensor from non-covalently anchored multi-walled carbon nanotubes with hexa-decafluorinated cobalt phthalocyanines

Abstract

To study the effect of synergetic interactions between metal-phthalocyanine and carbon nanotubes for gas sensing characteristics of carbon nanotubes, we synthesized a hybrid of cobalt(II)-1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexa-decafluoro-29H,31H-phthalocyanine/multi-walled carbon nanotubes (F₁₆CoPc/MWCNTs–COOH). The as-prepared hybrid was characterized through spectroscopic (FT-IR, UV-vis and Raman), electron microscopic (TEM and FE-SEM) and TGA investigations that confirmed the successful non-covalent anchoring of F₁₆CoPc onto MWCNTs–COOH through π–π stacking interactions. Further, a highly reversible, reproducible, sensitive and Cl₂ selective chemiresistive sensor was fabricated using F₁₆CoPc/MWCNTs–COOH hybrid, which exhibited a sensitivity of ∼63% for 2 ppm of Cl₂ and a limit of detection as low as 0.05 ppb. A plausible gas sensing mechanism for improved gas sensing characteristics of F₁₆CoPc/MWCNTs–COOH sensor towards Cl₂ was explained using Raman, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS) studies. Herein, cobalt metal ion is found to play an important role in enhancing gas sensing characteristics of the fabricated sensor.