Solid state spectroelectrochemistry of redox reactions in polypyrrole/oxide molecular heterojunctions

  1. Get@NRC: Solid state spectroelectrochemistry of redox reactions in polypyrrole/oxide molecular heterojunctions (Opens in a new window)
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Journal titleAnalytical Chemistry
Pages24592465; # of pages: 7
SubjectAbsorbance change; Applied bias; Carbon electrode; Imine formation; In-situ; Ion Mobility; Negative bias; Oxidation state; Oxide junction; Polaron formation; Polypyrrole (PPy); Positive bias; Resistance switching; Solid-state carbon; Spectral change; Surrounding environment; Acetonitrile; Electric resistance; Heterojunctions; Nitrogen compounds; Oxidation; Platinum; Polypyrroles; Redox reactions; Solid state devices; Spectroelectrochemistry; Ultraviolet spectroscopy; Polarons
AbstractTo understand the mechanism of bias-induced resistance switching observed in polypyrrole (PPy) based solid state junctions, in situ UV-vis absorption spectroscopy was employed to monitor oxidation states within PPy layers in solution and in PPy/metal oxide junctions. For PPy layers in acetonitrile, oxidation led primarily to cationic polaron formation, while oxidation in 0.1 M NaOH in H 2O resulted in imine formation, caused by deprotonation of polarons. On the basis of these results in solution, spectroelectrochemistry was used to monitor bias-induced formation of polarons and imines in PPy layers incorporated into solid state carbon/PPy/Al 2O 3/Pt junctions. A positive bias on the carbon electrode caused PPy oxidation, with the formation of polaron and imine species strongly dependent on the surrounding environment. The spectral changes associated with polarons or imines were stable for at least several hours after the applied bias, while a negative bias reversed the absorbance changes back to the initial PPy spectrum. These results indicate that PPy can be oxidized in nominally solid state devices, and the formation of stable polarons is dependent on the tendency for deprotonation of the polaron to the imine. Since PPy conductivity depends strongly on the polaron concentration, monitoring its concentration is critical to determining resistance switching mechanisms. Furthermore, the importance of ion mobility and OH - generation through H 2O reduction at the Pt contact are discussed. © 2012 American Chemical Society.
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AffiliationNational Research Council Canada (NRC-CNRC); National Institute for Nanotechnology (NINT-INNT)
Peer reviewedYes
NPARC number21269397
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Record identifier25df34b7-0d08-437d-8315-a50684bcf0a5
Record created2013-12-12
Record modified2016-05-09
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