AVS 51st International Symposium
    Organic Films and Devices Tuesday Sessions
       Session OF-TuP

Paper OF-TuP12
Site Specific Binding of Analyte Gases on Metallophthalocyanine Thin Films: Dft Calculations and Sticking Probability Measurements

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: N.L. Tran, University of California, San Diego
Authors: N.L. Tran, University of California, San Diego
G.C. Poon, University of California, San Diego
S. Bishop, University of California, San Diego
A.C. Kummel, University of California, San Diego
Correspondent: Click to Email
Several groups report the use of metallophthalocyanines (MPcs) as thin film resistive sensors for analyte gases such as NO@sub x@, CO, O@sub 3@ and NH@sub 3@; however, the chemisorption energies and mechanisms for these gases reacting with various MPcs have not been studied. Density functional theory (DFT) calculations performed in this study show that chemisorption energies vary strongly with metal center and analyte. These calculations also investigate the mechanism of chemisorption. Four analyte binding sites on the MPcs were investigated computationally: (i) metal centers, (ii) inner ring nitrogen atoms, (iii) outer ring nitrogen atoms, and (iv) organic rings. For NO@sub 2@ on FePc and CoPc as well as NH@sub 3@ on FePc , the simulations show chemisorption onto the metal centers and physisorption onto the outer ring nitrogens and organic rings. These calculations also show a multi-step absorption mechanism in which NO@sub 2@ initially binds to the inner ring nitrogens and subsequently migrates to the deep chemisorption well on the metal centers for FePc and CoPc. In contrast, only physisorption was observed for any bonding sites of NO@sub 2@ on NiPc and NH@sub 3@ on CoPc and NiPc. Sticking experiments are being performed to investigate the chemisorption mechanism and selectivity.