Gas Sensing Mechanism in Chemiresistive Cobalt and Metal-Free Phthalocyanine Thin Films

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• 作者：Forest I. Bohrer ; Amos Sharoni ; Corneliu Colesniuc ; Jeongwon Park ; Ivan K. Schuller ; Andrew C. Kummel ; William C. Trogler
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：May 2, 2007
• 年：2007
• 卷：129
• 期：17
• 页码：5640 - 5646
• 全文大小：299K
• 年卷期：v.129,no.17(May 2, 2007)
• ISSN：1520-5126

文摘

The gas sensing behaviors of cobalt phthalocyanine (CoPc) and metal-free phthalocyanine (H₂Pc) thin films were investigated with respect to analyte basicity. Chemiresistive sensors were fabricated bydeposition of 50 nm thick films on interdigitated gold electrodes via organic molecular beam epitaxy (OMBE).Time-dependent current responses of the films were measured at constant voltage during exposure toanalyte vapor doses. The analytes spanned a range of electron donor and hydrogen-bonding strengths. Itwas found that, when the analyte exceeded a critical base strength, the device responses for CoPc correlatedwith Lewis basicity, and device responses for H₂Pc correlated with hydrogen-bond basicity. This suggeststhat the analyte-phthalocyanine interaction is dominated by binding to the central cavity of thephthalocyanine with analyte coordination strength governing CoPc sensor responses and analyte hydrogen-bonding ability governing H₂Pc sensor responses. The interactions between the phthalocyanine films andanalytes were found to follow first-order kinetics. The influence of O₂ on the film response was found tosignificantly affect sensor response and recovery. The increase of resistance generally observed for analytebinding can be attributed to hole destruction in the semiconductor film by oxygen displacement, as well ashole trapping by electron donor ligands.