Carrier generation and carrier determination in dipyridyldiketopyrrolopyrrole-based H2 gas sensors

Operation mechanism of dipyridyldiketopyrrolopyrrole (DPPP)-based H-2 sensor has been investigated with special attention to the electric-field-assisted dissociation of H-2 in the presence of Pd or Pt, as well as the carrier generation and carrier determination. H-2 is found to dissociate exponentially with an increase of the electric field above 10(2-3)V/cm as monitored by an electric current. The dissociation is greatly enhanced by the presence of DPPP which serves as a proton acceptor due to its pyridyl-N atom. The detection of H-2 starts with dissociation of H-2, followed by protonation of atomic hydrogen (H) at the N atom of the pyridyl ring of DPPP, ending up with a release of an electron which contributes to the electrical conduction: H+ pyridyl ring. protonated pyridyl ring (N+-H)+e'. The electron conduction is confirmed by the Seebeck effect. Judging from the above process, the atomic hydrogen is pictured as an electron donor. However, the present doping is rather characterized by an instantaneous one, since the extent of doping depends on the ambient H-2 concentration. (c) 2006 American Institute of Physics