Nanomateriali, avanzano nuovi metodi

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L’annuncio del Trinity College di Dublino presenta un nuovo sistema, paragonabile al grafene, per la produzione di nanostrutture a scopi termoelettrici ed energetici. Potrebbe essere una svolta scientifico-applicativa molto importante per accelerare lo sviluppo e le applicazioni delle nanotecnologie

Sul numero odierno di «Science» un gruppo di ricercatori (del Trinity College di Dublino, dell’Università di Oxford, dell’Imperial College di Londra, dell’Università di Seoul e del College Station dell’Università del Texas), annunciano la messa a punto di un nuovo metodo per la produzione di strati nanomateriali, in particolare strati con spessore monoatomico, a partire da una serie di composti chimici o sostanze che si trovano nei comuni soventi.

La produzione di tali nanomateriali può essere effettuata con caratteristiche predeterminate e finalizzata, per esempio, al recupero energetico o all’accumulo di energia o ad altre applicazioni termoelettriche che aumentino l’efficienza energetica. Secondo i ricercatori il metodo da loro inventato può essere paragonato a quello messo a punto ed utilizzato per produrre il «grafene» che, come noto, ha vinto il premio nobel 2010.

Se i risultati di questa ricerca saranno confermati, si tratta di una svolta scientifico-applicativa molto importante per accelerare lo sviluppo e le applicazioni delle nanotecnologie, ma anche per lo sviluppo di sistemi energetici per l’utilizzazione delle energie rinnovabili in modo molto efficiente ed a costi competitivi. (V. F.)

Di seguito l’abstract dell’articolo e l’annuncio del Trinity College di Dublino

Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials

Coleman, J.N. et al. – Science,4 February 2011: Vol. 331, no. 6017, pp. 568-571. DOI: 10.1126/science.1194975

If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS2, WS2, MoSe2, MoTe2, TaSe2, NbSe2, NiTe2, BN, and Bi2Te3 can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS2 and MoS2 effectively reinforce polymers, whereas WS2/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.

Trinity College Dublin

New nanomaterials unlock new electronic and energy technologies

Atom-thick sheets unlock future technologies

A new way of splitting layered materials to give atom thin “nanosheets” has been discovered. This has led to a range of novel two-dimensional nanomaterials with chemical and electronic properties that have the potential to enable new electronic and energy storage technologies. The collaborative* international research led by the Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Ireland, and the University of Oxford has been published in this week’s Science.

The scientists have invented a versatile method for creating these atom thin nanosheets from a range of materials using common solvents and ultrasound, utilising devices similar to those used to clean jewellery. The new method is simple, fast, and inexpensive, and could be scaled up to work on an industrial scale.

“Of the many possible applications of these new nanosheets, perhaps the most important are as thermoelectric materials. These materials, when fabricated into devices, can generate electricity from waste heat. For example, in gas-fired power plants approximately 50% of energy produced is lost as waste heat while for coal and oil plants the figure is up to 70%. However, the development of efficient thermoelectric devices would allow some of this waste heat to be recycled cheaply and easily, something that has been beyond us, up until now,” explained Professor Jonathan Coleman, Principal Investigator at CRANN and the School of Physics, Trinity College Dublin who led the research along with Dr Valeria Nicolosi in the Department of Materials at the University of Oxford.

This research can be compared to the work regarding the two-dimensional material graphene, which won the Nobel Prize in 2010. Graphene has generated significant interest because when separated into individual flakes, it has exceptional electronic and mechanical properties that are very different to those of its parent crystal, graphite. However, graphite is just one of hundreds of layered materials, some of which may enable powerful new technologies.

Coleman’s work will open up over 150 similarly exotic layered materials – such as Boron Nitride, Molybdenum disulfide, and Bismuth telluride – that have the potential to be metallic, semiconducting or insulating, depending on their chemical composition and how their atoms are arranged. This new family of materials opens a whole range of new “super” materials.

For decades researchers have tried to create nanosheets from layered materials in order to unlock their unusual electronic and thermoelectric properties. However, previous methods were time consuming, laborious or of very low yield and so unsuited to most applications.

“Our new method offers low-costs, a very high yield and a very large throughput: within a couple of hours, and with just 1 mg of material, billions and billions of one-atom-thick nanosheets can be made at the same time from a wide variety of exotic layered materials,” explained Dr Nicolosi, from the University of Oxford.

These new materials are also suited for use in next generation batteries – “supercapacitors” – which can deliver energy thousands of times faster than standard batteries, enabling new applications such as electric cars. Many of these new atomic layered materials are very strong and can be added to plastics to produce super-strong composites. These will be useful in a range of industries from simple structural plastics to aeronautics.

Contact:

Prof. Jonathan Coleman

e-mail: colemaj@tcd.ie

tel: 003-538-778-34917

Centre for Research on Nanostructures (CRANN)

Trinity College Dublin

http://www.tcd.ie/

Prof. Valeria Nicolosi

valeria.nicolosi@materials.ox.ac.uk

Department of Materials

Oxford University

http://www.materials.ox.ac.uk/