Optical Characterizations and Gas Detection Study of Metalo-Phthalocyanine Thin Film Species

Copper and zinc phthalocyanines (CuPc and ZnPc) were deposited onto glass slides and platinum-interdigitated electrodes using spin coating technique to investigate the optical properties and sensing capability towards some odorants. The optical properties have been studied using UV-Visible absorption spectroscopy. The red shift in the absorption band in case of thin films indicated that phthalocyanines tend to make aggregation of dimer and trimmer in comparison to solution where only monomers exist. Energy gap calculations, utilizing Tauc plot, show that the CuPc and ZnPc having band gaps of 3.87 ev and 3.93 ev respectively and the transition of charge carriers is direct transition. Detection of some gases has been carried out using resistive based sensor measurements. ZnPc has shown no obvious behavior towards chloroform, dimethylformamide and nitrogen dioxide gases, while CuPc was selective to nitrogen dioxide gas and shown very high sensitivity and reversibility. The response and recovery times of copper phthalocyanine thin film due 100 ppm nitrogen dioxide were 20 and 142.6 sec respectively.