First Freestanding Gold Sheets Less Than a Nanometer Thick

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  • Published: 12 August 2019
  • Copyright: Wiley-VCH Verlag GmbH & Co. KGaA
  • Source / Publisher: Advanced Science/Wiley-VCH
thumbnail image: First Freestanding Gold Sheets Less Than a Nanometer Thick

Two-dimensional materials such as graphene, which have thicknesses of a single to a few atomic layers, often have useful properties for a range of applications. 2D sheets of metals, for example, could be used in bioimaging, therapy, sensing, and catalysis. However, the production of freestanding 2D metal sheets without a substrate as support is challenging.

Stephen D. Evans, University of Leeds, UK, and colleagues have synthesized freestanding gold nanosheets with a thickness of less than 0.5 nm. This is the first preparation of freestanding 2D gold with sub‐nanometer thickness. The team used methyl orange as a "confining agent" for the synthesis of the nanosheets. They added aqueous solutions of HAuCl4 and sodium citrate to an aqueous solution of methyl orange at 20 °C. The solution was left standing for 12 h and the products were collected by centrifugation.

Using transmission electron microscopy (TEM), the researchers found that 2D nanostructures with a “seaweed‐like" shape were formed (pictured). The thickness was measured using atomic force microscope (AFM) and found to be (0.47 ± 0.01) nm. The team suspects that stacking of methyl orange along the surface directs the growth of the nanosheets.

The Au nanosheets have a high surface‐area‐to‐volume ratio, which makes them good catalysts. The team found excellent catalytic performance for the reduction of 4‐nitrophenol as well as for the degradation of H2O2. According to the researchers, the work could provide a new pathway toward atomically‐thin metal nanomaterials.


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