Observation of different charge transport regimes and large magnetoresistance in graphene oxide layers

Abstract

We report a systematic study on charge transport properties of thermally reduced graphene\ud oxide (rGO) layers, from room temperature to 2 K and in presence of magnetic fields up to\ud 7 T. The most conductive rGO sheets follow different transport regimes: at room temperature\ud they show an Arrhenius-like behavior. At lower temperature they exhibits a thermally\ud activated behavior with resistance R following a R = R0exp(T0/T)p law with p = 1/3, consistently\ud with 2D Mott Variable Range Hopping (VRH) transport mechanism. Below a given\ud temperature Tc, we observe a crossover from VHR to another regime, probably due to a\ud shortening of the characteristic lengths of the disordered 2D system. The temperature Tc\ud depends on the reduction grade of the rGO. Magnetoresistance DR/R of our rGO films shows\ud as well a crossover between positive and negative and below liquid He temperature DR/R\ud reaches values larger than 60%, surprisingly high for a – nominally – non magnetic\ud material

Systematic study of the correlation between surface chemistry, conductivity and electrocatalytic properties of graphene oxide nanosheets

“…Among the different methods used to such a purpose, the electrochemical approach allows fine tuning of the reduction level of the material, finally conditioning the surface chemistry and degree of interaction between adjacent graphene foils [11][12][13]. Correspondingly, the electrical conductivity of GO may be tuned from insulating to highly conductive [8,14], and the surface chemistry from highly hydrophilic to hydrophobic character [15]. Electrochemical methods can be also used for controlled functionalization of graphene nanosheets [16] as well for production of graphene-based electrodes [16] or of composite foams [17].…”

Charge transport mechanism of thermally reduced graphene oxide and their fabrication for high performance shield against electromagnetic pollution

“…The removal of oxygen can transform the material into a reduced graphene like semiconductor and ultimately to a graphene like semimetal [20]. Along with graphene, reduced graphene oxide has also gained tremendous attention due to its superior mechanical, electrical, optical, chemical and thermal properties [4,13,14]. Due to these superior properties, it is a promising candidate for many potential applications such as supercapacitor [21], non-volatile memory devices [22], electrochemical and electrochromic devices [23], gas sensors [24] and solar cell devices [25].…”

“…Due to these superior properties, it is a promising candidate for many potential applications such as supercapacitor [21], non-volatile memory devices [22], electrochemical and electrochromic devices [23], gas sensors [24] and solar cell devices [25]. Along with these applications, the excellent electrical properties and high surface area [4,13,14] can make reduced graphene oxide a potential material for the electromagnetic shield to absorb incident EM waves. Research suggests that chemically graphitized reduced graphene oxide/silicon dioxide composites exhibit EMI shielding efficiency of 38 dB at 8.5 GHz [2].The EMI shielding effectiveness of 37.58 dB in the frequency range of 12.4e18 GHz is observed in the composite of iron oxide infiltrated reduced graphene oxide with multiwalled carbon nanotubes forest sandwich network [3].…”

Electrochemical Functionalization of Graphene at the Nanoscale with Self-Assembling Diazonium Salts

“…In such a way, the conductivity of single sheets can be lowered leading to a transition from semi-metal to insulator. 5 Direct covalent functionalization of pristine graphene (without passing through GO intermediates) can also be obtained with different approaches, taking advantage of the large expertise acquired on the chemistry of carbon nanotubes and fullerenes. [6][7][8] However, the low reactivity of the graphene basal surface requires highly reactive conditions for its covalent modification.…”