Identification of high performance solvents for the sustainable processing of graphene

Nanomaterials have many advanced applications, from bio-medicine to flexible electronics to energy storage, and the broad interest in graphene-based materials and devices means that high annual tonnages will be required to meet this demand. However, manufacturing at the required scale remains unfeasible until economic and environmental obstacles are resolved. Liquid exfoliation of graphite is the preferred scalable method to prepare large quantities of good quality graphene, but only low concentrations are achieved and the solvents habitually employed are toxic. Furthermore, good dispersions of nanomaterials in organic solvents are crucial for the synthesis of many types of nanocomposites. To address the performance and safety issues of solvent use, a bespoke approach to solvent selection was developed and the renewable solvent Cyrene was identified as having excellent properties. Graphene dispersions in Cyrene were found to be an order of magnitude more concentrated than those achieved in N-methylpyrrolidinone (NMP). Key attributes to this success are optimum solvent polarity, and importantly a high viscosity. We report the role of viscosity as crucial for the creation of larger and less defective graphene flakes. These findings can equally be applied to the dispersion of other layered bi-dimensional materials, where alternative solvent options could be used as drop-in replacements for established processes without disruption or the need to use specialized equipment. Thus, the discovery of a benign yet high performance graphene processing solvent enhances the efficiency, sustainability and commercial potential of this ever-growing field, particularly in the area of bulk material processing for large volume applications

Graphene and polyethylene. A strong combination towards multifunctional nanocomposites

The key to the preparation of polymer nanocomposites with new or improved properties resides in the homogeneous dispersion of the filler and in the efficient load transfer between components through strong filler/polymer interfacial interactions. This paper reports on the preparation of a series of nanocomposites of graphene and a polyolefin using different experimental approaches, with the final goal of obtaining multifunctional materials. A high-density polyethylene (HDPE) is employed as the matrix, while unmodified and chemically modified graphene fillers are used. By selecting the correct combination as well as the adequate preparation process, the nanocomposites display optimized thermal and mechanical properties, while also conferring good gas barrier properties and significant levels of electrical conductivity

Phase shift of amplitude-modulated optical signals in graphene oxide water dispersions due to thermal lens focal length oscillation

We analyze the phase shift induced in an amplitude-modulated laser beam propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. This phase shift arises from the thermally induced nonlinear refraction in the sample. The system exhibits strong optical limiting performance for weak continuous-wave signals. A theoretical model including beam propagation and thermal lens focal length oscillation reproduces the experimental findings

Monolithic mesoporous graphitic composites as super capacitors : From Starbons to Starenes®

In this study, we present a new class of monolithic mesoporous carbonaceous materials produced via the carbonisation of a mesoporous starch aerogel highly doped with graphite. Consecutive ball milling, microwave assisted gelation and carbonization treatment produced a high concentration of dispersed graphite. These treatments induce a strong interaction between the graphite particles and the developing carbonaceous matrix, including partial delamination of graphite and the merging of the nanoflakes into the carbonaceous structure. From a combination of SEM and TEM it was found that the graphite particles reduced in size to 24 and 37 nm, matching the pore wall sizes of the produced materials. From XRD, ball milling and heating helped reduce the number of graphene layers by 40%, with presence within the porous starch matrix reducing this a further 13%. The high degree of graphite dispersion/incorporation induces a pronounced increase in conductivity, and excellent capacitance retention, in excess of 10 000 charge-discharge cycles, offering a cost efficient and sustainably produced alternative to activated carbon based EDLCs and importantly, the resultant monolithic structures mitigate the need for additional binders

Fabrication of highly ordered arrays of platinum nanoparticles using direct laser interference patterning

Highly ordered electrode arrays composed by lines of platinum nanoparticles deposited onto gold substrates have been made by direct laser interference patterning (DLIP) of polyaniline (PANI) thin films, followed by electrochemical deposition of platinum nanoparticles. Nanostructured arrays of electrocatalytic Pt particles are built in that way.The Alfred Krupp Foundation, Alexander von Humboldt Foundation, BMBF (Germany) FONCYT (Grants PICT R03/453, PICT04/25521, and PAE0422711), CONICET (Grant PIP5221), SECYT-UNRC (Argentina), and MEC (Grant MAT2007-60621) (Spain)

Mesoporous materials from nanoparticle enhanced polysaccharides

There is described a mesoporous composite material comprising carbon nanoparticles dispersed in a mesoporous carbonaceous material.Peer reviewedUniversity of York, Consejo Superior de Investigaciones Científicas (España)A1 Solicitud de patente con informe sobre el estado de la técnic

Effect of click-chemistry approaches for graphene modification on the electrical, thermal, and mechanical properties of polyethylene/graphene nanocomposites

The effect of the type of chemical route used to functionalize graphene with short-chain polyethylene on the final properties of graphene-based high density polyethylene nanocomposites is reported. Three different click reactions, namely copper-catalyzed alkyne-azide (CuAAC), thiol-ene and thiol-yne have been addressed. The nanocomposites were prepared using a method that we denominate >gradient interphase>. The electrical and thermal conductivity and the mechanical properties strongly depend on the click reaction used to modify graphene, the thiol-ene reaction giving the best results. This study demonstrates that the election of the chemical strategy to provide graphene with functionalities common to the polymer matrix and the engineering of the interface are crucial to obtain nanocomposites with improved properties. © 2013 American Chemical Society.Peer Reviewe