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Graphene oxide for transparent electronics

[color=Blue][b][Nano News]Researchers in the US have developed a new and simple solution-based method to deposit graphene oxide onto a variety of substrates in a controlled way at room temperature. The large-area ultrathin films produced are transparent and their electrical properties can be tuned from semiconducting to metallic by controlling their thickness. The technique shows promise for making devices like electrodes for solar cells.[/b][/color]+y(p{q7X`
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[color=Gray]Thin films of solution-processed graphene oxide. (a-c) Photographs of thin films on filtration membrane (a), glass (b) and plastic (c) substrates. Credit: Nature Nanotechnology.[/color]0M:R9Y6kIUwisC
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"The very thin films, which are essentially composed of atomically thin individual graphene oxide flakes covering the surface, are good semiconductors and increasing the number of layers comprising the films leads to metallic behaviour," team leader Manish Chhowalla of Rutgers University told nanotechweb.org.
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;h(`.ekgr`.`1i The technique is based on a vacuum filtration method, where a suspension containing the single layer graphene oxide sheets in water is filtered through a 25 nm pore filter paper. As the water filters through the pores, micron-sized sheets become trapped. As one pore clogs, the rate at which the water passes through that pore is greatly diminished while the suspension continues to filter through adjacent uncovered pores, explains Chhowalla. This continues until all of the pores are clogged.
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The method produces a uniform layer of graphene oxide sheets around 1–5 nm thick on the filter membrane. More layers can be deposited after the first layer is produced as more of the suspension is filtered. "By controlling the volume of suspension, it is possible to control the thickness of the film on the filter paper," said Chhowalla.
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The film is then transferred onto a suitable substrate, such as silica on silicon glass, or plastics. This is done by placing the membrane with the film side down on the substrate surface and dissolving the filter paper away with acetone. The films can be processed to make devices like organic solar cells or transistors. Although such devices still perform poorly, the proof-of-concept technique shows promise – especially for making flexible, transparent conductors.
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[g#t+k(w1EL l^N The team now plans to make the films more conducting and figure out ways to improve their mobility so that their final properties are more similar to those of graphene.'c,H3c%z7^m
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The work was reported in [url=http://www.nature.com/nnano/journal/v3/n5/abs/nnano.2008.83.html][i]Nature Nanotechnology[/i] [b]3[/b] 270[/url].
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Source:  nanotechweb.org