Showing papers by "Cinzia Casiraghi published in 2015"
TL;DR: A fundamental understanding on a straightforward supramolecular approach for producing homogenous dispersions of unfunctionalized and non-oxidized graphene nanosheets in four different solvents is attained and this approach relying on the synergistic effect of a ad-hoc solvent and molecules to promote the exfoliation of graphene in liquid media represents a promising and modular strategy towards the rational design of improved dispersion-stabilizing agents.
Abstract: Achieving the full control over the production as well as processability of high-quality graphene represents a major challenge with potential interest in the field of fabrication of multifunctional devices. The outstanding effort dedicated to tackle this challenge in the last decade revealed that certain organic molecules are capable of leveraging the exfoliation of graphite with different efficiencies. Here, a fundamental understanding on a straightforward supramolecular approach for producing homogenous dispersions of unfunctionalized and non-oxidized graphene nanosheets in four different solvents is attained, namely N-methyl-2-pyrrolidinone, N,N-dimethylformamide, ortho-dichlorobenzene, and 1,2,4-trichlorobenzene. In particular, a comparative study on the liquid-phase exfoliation of graphene in the presence of linear alkanes of different lengths terminated by a carboxylic-acid head group is performed. These molecules act as graphene dispersion-stabilizing agents during the exfoliation process. The efficiency of the exfoliation in terms of concentration of exfoliated graphene is found to be proportional to the length of the employed fatty acid. Importantly, a high percentage of single-layer graphene flakes is revealed by high-resolution transmission electron microscopy and Raman spectroscopy analyses. A simple yet effective thermodynamic model is developed to interpret the chain-length dependence of the exfoliation yield. This approach relying on the synergistic effect of a ad-hoc solvent and molecules to promote the exfoliation of graphene in liquid media represents a promising and modular strategy towards the rational design of improved dispersion-stabilizing agents.
88 citations
TL;DR: By tuning the ratio between organic solvents such as N-methyl-2-pyrrolidinone or ortho-dichlorobenzene, and n-octylbenzene molecules, the concentration of exfoliated graphene can be enhanced by 230% as a result of the high affinity of the latter molecules for the basal plane of graphene.
Abstract: Due to a unique combination of electrical and thermal conductivity, mechanical stiffness, strength and elasticity, graphene became a rising star on the horizon of materials science. This two-dimensional material has found applications in many areas of science ranging from electronics to composites. Making use of different approaches, unfunctionalized and non-oxidized graphene sheets can be produced; among them an inexpensive and scalable method based on liquid-phase exfoliation of graphite (LPE) holds potential for applications in opto-electronics and nanocomposites. Here we have used n-octylbenzene molecules as graphene dispersion-stabilizing agents during the graphite LPE process. We have demonstrated that by tuning the ratio between organic solvents such as N-methyl-2-pyrrolidinone or ortho-dichlorobenzene, and n-octylbenzene molecules, the concentration of exfoliated graphene can be enhanced by 230% as a result of the high affinity of the latter molecules for the basal plane of graphene. The LPE processed graphene dispersions were further deposited onto solid substrates by exploiting a new deposition technique called spin-controlled drop casting, which was shown to produce uniform highly conductive and transparent graphene films.
82 citations
1 citations