The new nanoscale manufacturing process draws zinc to the surface of a liquid, where it forms sheets just a few atoms thick. Credit: Xudong Wang
After 6 yrs of painstaking effort, Uni of Wisconsin-Madison materials scientists believe the tiny sheets of the semiconductor zinc oxide they’re growing could have huge implications for the future of a host of electronic and biomedical devices. Xudong Wang et al have developed a technique for creating nearly 2D sheets of compounds that do not naturally form such thin materials. Nanomaterials have unique electronic and chemical properties compared to identically composed materials at larger, conventional scales. Until now, they were limited to working with naturally occurring 2-D nanosheets eg graphene. Developing a reliable method to synthesize 2D nanosheets from other materials has been a goal of materials researchers and nanotechnology industry for years.
METHOD: They applied a specially formulated surfactant onto the surface of a liquid containing zinc ions. The surfactant assembles itself into a single layer at the surface of the liquid, with -ve sulfate ions pointed in the direction of the liquid. Those sulfate ions draw the positively charged zinc ions from within the liquid to the surface, and within a couple hours enough Zn ions are drawn up to form continuous zinc oxide nanosheets only a few atomic layers thick. After 5 years of trial and error with different surfactant solutions, the idea paid off.
The 2D zinc oxide nanosheets can function as semiconductor transistors called a p-type, the opposite electronic behavior of naturally occurring zinc oxide. Researchers have for some time attempted to produce zinc oxide with reliable p-type semiconductor properties.
Zinc oxide is a very useful component of electronic materials, and the new nanosheets have potential for use in sensors,transducers and optical devices.
But the zinc oxide nanosheets are only the first of what could be a revolution in 2D nanomaterials. The team is applying its surfactant method to growing 2-D nanosheets of gold and palladium, and the technique holds promise for growing nanosheets from all sorts of metals that wouldn’t form them naturally. http://news.wisc.edu/nanosheet-growth-technique-could-revolutionize-nanomaterial-production/
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