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Figure 1. Schematic and Characterization of Small Molecular Bilayer Lamellar Hydrogels
Figure 2. Morphology and structural characterization of ultra-thin single crystal gold films
The single crystal ultra-thin film is a two-dimensional single-crystal material with macroscopic lateral dimensions and nano-scale or even atomic-scale thickness. Since its dimension in the thickness dimension is much smaller than the other two dimensions, the electronic energy level and state of the material are caused. Density changes significantly compared to the bulk material and thus exhibits unique physical and chemical properties.
The in-depth research on the physical properties of single-crystal ultra-thin films and the development and exploration of their applications depend on the development of controllable, high-quality methods for the preparation of various single-crystal ultra-thin films. In accordance with the stripping process of graphene, the recently developed stripping technology was used to prepare various semiconductor-type single crystal ultra-thin films such as MoS2, GaN, and MxM1-x(OH)2. However, this method is applicable to bulk materials with a layered structure. It is still a great challenge to obtain monolayer ultra-thin films of non-lamellar structure with nanometer or even atomically controllable thickness.
Recently, Jian Jian, a researcher at the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences, proposed a method for preparing large-area metal ultra-thin films using two-dimensional limited-domain reactions. The method uses a liquid crystal bilayer membrane as a template system to make the bilayer membrane and water form an alternating layered ordered structure of bilayer membrane/water layer/bilayer membrane.
Since the thickness of the water layer is in the nanometer size and can be precisely controlled by changing its mass, the reduction reaction of the metal single crystal can be controlled in the water layer, and a large area single layer with controllable thickness of several nanometers to several tens of nanometers can be prepared. Crystal gold ultra thin film. The research team collaborated with Prof. Dongchuan Wu, Prof. Xu Ke, and Prof. Ren Bin of Xiamen University to further study the surface plasmon effect of ultra-thin gold film on single crystal. The relevant results were published in J. Am. Chem. Soc. 2013, 135, On the 12544.
On the basis of the above work, in order to obtain even thinner single crystal thin films, the team designed the amphiphilic small molecules to form a strong hydrogen bond between them and water molecules. Since the fluidity of water is extremely limited, a bilayer/water/bimolecular membrane hydrogel system is obtained, which maintains the original layered and ordered structure.
Using this hydrogel system as a reaction field, a single-crystal ultrathin gold film having a thickness of only 3.6 nm and an area of ​​more than 100 square microns was prepared. The research team collaborated with Zhang Hao, a researcher at Suzhou Institute of Nanotechnology, Ni Weihai, and Professor Li Youyong from Suzhou University to theoretically calculate and test the optoelectronic properties of single-crystal gold films. The relevant results were published on Nat. Commun. 2014, 5, 3313.
This work was strongly supported by the National Natural Science Foundation of China (50973080, 21273270) and the national "973" major scientific research project (2013CB933002).
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