The conductivity of graphite oxide films is modulated using reducing agents. It is found that the sheet resistance of graphite oxide film reduced using sodium borohydride (NaBH4) is much lower than that of films reduced using hydrazine (N2H4). This is attributed to the formation of CN groups in the N2H4 case, which may act as donors compensating the hole carriers in reduced graphite oxide. In the case of NaBH4 reduction, the interlayer distance is first slightly expanded by the formation of intermediate boron oxide complexes and then contracted by the gradual removal of carbonyl and hydroxyl groups along with the boron oxide complexes. The fabricated conducting film comprising a NaBH4‐reduced graphite oxide reveals a sheet resistance comparable to that of dispersed graphene.
To modify oxide structure and introduce a thin conductive film on Li4Ti5O12, thermal nitridation was adopted for the first time. NH3 decomposes surface Li4Ti5O12 to conductive TiN at high temperature, and surprisingly, it also modifies the surface structure in a way to accommodate the single phase Li insertion and extraction. The electrochemically induced Li4+deltaTi5O12 with a TiN coating layer shows great electrochemical properties at high current densities.
We investigated the modulation of optical properties of single-walled carbon nanotubes (SWCNTs) by AuCl 3 doping. The van Hove singularity transitions (E 11 (S), E 22 (S), E 11 (M)) in absorption spectroscopy disappeared gradually with an increasing doping concentration and a new peak appeared at a high doping concentration. The work function was downshifted up to 0.42 eV by a strong charge transfer from the SWCNTs to AuCl 3 by a high level of p-doping. We propose that this large work function shift forces the Fermi level of the SWCNTs to be located deep in the valence band, i.e., highly degenerate, creating empty van Hove singularity states, and hence the work function shift invokes a new asymmetric transition in the absorption spectroscopy from a deeper level to newly generated empty states.
Poly(3,4-ethylenedioxythiophene)
(PEDOT) is certainly the most
known and most used conductive polymer because it is commercially
available and shows great potential for organic electronic, photovoltaic,
and thermoelectric applications. Studies dedicated to PEDOT films
have led to high conductivity enhancements. However, an exhaustive
understanding of the mechanisms governing such enhancement is still
lacking, hindered by the semicrystalline nature of the material itself.
In this article, we report the development of highly conductive PEDOT
films by controlling the crystallization of the PEDOT chains and by
a subsequent dopant engineering approach using iron(III) trifluoromethanesulfonate
as oxidant, N-methyl pyrrolidone as polymerization
rate controller and sulfuric acid as dopant. XRD, HRTEM, Synchrotron
GIWAXS analyses and conductivity measurements down to 3 K allowed
us to unravel the organization, doping, and transport mechanism of
these highly conductive PEDOT materials. N-methyl
pyrrolidone promotes bigger crystallites and structure enhancement
during polymerization, whereas sulfuric acid treatment allows the
replacement of triflate anions by hydrogenosulfate and increases the
charge carrier concentration. We finally propose a charge transport
model that fully corroborates our experimental observations. These
polymers exhibit conductivities up to 5400 S cm–1 and thus show great promise for room temperature thermoelectric
applications or ITO alternative for transparent electrodes.
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