Graphene exfoliation in the presence of semiconducting polymers for improved film homogeneity and electrical performances

We report on the production of hybrid graphene/semiconducting polymer films in one step procedure by making use of ultrasound-assisted liquid-phase exfoliation of graphite powder in the presence of π-conjugated polymers, i.e. poly(3-hexylthiophene) (P3HT) or poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b']dithiophen-2-yl)-alt-[1,2,5]thiadiazolo-[3,4-c]pyridine] (PCDTPT). The polymers were chosen in view of their different propensity to form crystalline structures, their decoration with alkyl chains that are known to possess high affinity for the basal plane of graphene, the energy levels of their frontier orbitals which are extremely similar to the work function of graphene, and their high electrical performance when integrated in field-effect transistors (FETs). The polymers act as a dispersion-stabilizing agent and prevent the re-aggregation of the exfoliated graphene flakes, ultimately enabling the production of homogeneous bi-component dispersions. The electrical characterization of few-layer graphene/PCDTPT hybrids, when integrated as active layer in bottom-contact bottom-gate FETs, revealed an increase of the field-effect mobility compared to the π-conjugated-based pristine devices, a result which can be attributed to the joint effect of the few-layer graphene sheets and semiconducting polymers improving the charge-transport in the channel of the field-effect transistor. In particular, few-layer graphene/PCDTPT films displayed a 30-fold increase of PCDTPT's mobility if compared to pristine polymer samples. Such findings represent a step forward towards the optimization of graphene exfoliation and processing into electronic devices, as well as towards improved electrical performance in organic-based field-effect transistors

Morphology and Electronic Properties of Electrochemically Exfoliated Graphene

Electrochemically exfoliated graphene (EEG) possesses optical and electronic properties that are markedly different from those of the more explored graphene oxide in both its pristine and reduced forms. EEG also holds a unique advantage compared to other graphenes produced by exfoliation in liquid media: it can be obtained in large quantities in a short time. However, an in-depth understanding of the structure–properties relationship of this material is still lacking. In this work, we report physicochemical characterization of EEG combined with an investigation of the electronic properties of this material carried out both at the single flake level and on the films. Additionally, we use for the first time microwave irradiation to reduce the EEG and demonstrate that the oxygen functionalities are not the bottleneck for charge transport in EEG, which is rather hindered by the presence of structural defects within the basal plane

A 3D insight on the catalytic nanostructuration of few-layer graphene

The catalytic cutting of few-layer graphene is nowadays a hot topic in materials research due to its potential applications in the catalysis field and the graphene nanoribbons fabrication. We show here a 3D analysis of the nanostructuration of few-layer graphene by iron-based nanoparticles under hydrogen flow. The nanoparticles located at the edges or attached to the steps on the FLG sheets create trenches and tunnels with orientations, lengths and morphologies defined by the crystallography and the topography of the carbon substrate. The cross-sectional analysis of the 3D volumes highlights the role of the active nanoparticle identity on the trench size and shape, with emphasis on the topographical stability of the basal planes within the resulting trenches and channels, no matter the obstacle encountered. The actual study gives a deep insight on the impact of nanoparticles morphology and support topography on the 3D character of nanostructures built up by catalytic cutting