首页|Paramagnetic transitions and weak-diamagnetism in sulfur-doped buckypapers and graphene-oxide composites
Paramagnetic transitions and weak-diamagnetism in sulfur-doped buckypapers and graphene-oxide composites
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NSTL
Elsevier
? 2022The appearance of coexisting ferromagnetic and superconductive phenomena in graphite?sulfur and amorphous carbon?sulfur composites has recently attracted an important attention. In this work we propose a novel re-investigation of the carbon?sulfur doping mechanism performed by employing carbon nanotube networks (cm-scale buckypapers) and graphene-oxide films as host-materials. In the buckypaper-case, the presence of multiple sulfidation processes involving formation of 1) carbon?sulfur and 2) metal-sulfide phases was demonstrated. Presence of carbon?sulfur bonding was identified by employing both Raman spectroscopy and X-ray photoelectron spectroscopy. The conductive and magnetic properties of the sulfur-rich areas within the buckypaper were also investigated. An enhanced carbon?sulfur bonding was then identified in sulfur-doped graphene-oxide films. In this latter case we demonstrate an almost complete annihilation of ferromagnetic-signals. ESR-spectroscopy of this second-type of system revealed the appearance of a paramagnetic transition for g ~ 2.08 at T ~ 77 K, possibly originating from the carbon?sulfur bonding. A weak enhancement in the diamagnetic component could be interestingly detected below T ~ 60 K as a consequence of sulfur doping, after subtraction of the percolative ferromagnetic signals.
NSTL
Elsevier
