Study on Enhancement Mechanism of Conductivity Induced
by Graphene Oxide for Polypyrrole Nanocomposites
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Abstract
Polypyrrole
(PPy)/graphene oxide (GO) nanosheet composites with
different GO content have been successfully prepared. The morphology,
microstructure, defect property and conducting mechanism were examined
by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR),
field-emission scanning electron microscope (FE-SEM), X-ray photoelectron
spectra (XPS), positron annihilation technology (PAT), and electrical
conductivity measurements for PPy/GO conducting nanocomposites, respectively.
Experimental results indicated that PPy was deposited onto the GO
surface homogeneously. Four orders of magnitude increase in electrical
conductivity was successfully achieved with small quantities of GO
compared to pristine PPy. In order to elucidate the conducting mechanism,
an electron transfer model was used to describe bipolaronic formation,
which can be confirmed by XPS and positron annihilation parameters
measured including positron annihilation lifetimes, positron annihilation
Doppler broadening spectroscopy (DBS) and continuous distribution
of positron lifetime. Electronic conductivity enhancement can be attributed
to (a) the interfacial interaction between the GO layers and PPy results
in the electron transfer, which leads to the increase of bipolaronic
concentration, and (b) the π–π stacking between
the GO layers and PPy can improve the conjugation degree of the PPy
chains and the longer conjugation length makes the conducting particle
delocalization more easily, leading to the increase in electron mobility.
On the other hand, the continuous conducting network structure of
graphene nanosheets homogeneously dispersed in the PPy matrix and
carriers between localized states formed at the graphene–PPy
interfaces where hopping occurred, also result in increase of conductivity