Recently, Professor Yu Shuhong of the University of Science and Technology of China, in collaboration with the Li Zhenyu Group, has made new progress in the design, synthesis, and photoelectric conversion applications of polymorphic sulfide semiconductors. The research paper was published on the September 26th issue of the American Chemical Society (J. Am. Chem. Soc. 2016, 138(39), 12913-12919) and was selected by JACS Spotlights as a research highlight.
The synthesis and formation mechanism of novel nanocrystalline materials is the focus of the current research on colloidal wet chemical synthesis of nanocrystals. Copper sulfide (Cu2-xS) is a kind of traditional semiconductor material. With the change of x value, it shows different crystal structure. When the value of x increases, the bandgap width decreases and the surface plasmon resonance effect increases. Sex to metal transition. People have done a lot of work on single-component and different phases of Cu2-xS. The synthesis of nano-heterojunctions has received widespread attention because of its ability to integrate the advantages of different material components to achieve synergistic effects over single components. In contrast, research on polymorphic nanoheterojunctions is relatively rare. If semiconducting Cu2-xS and metallic CuS can be compounded together, it is expected to exhibit more peculiar properties.
In order to achieve this goal, the researchers developed a colloid wet chemical "precursor induction" method for the first time successfully prepared a unique polymorphic heterojunction Cu1.94S-CuS, namely the one-dimensional semiconductor Cu1.94S and two-dimensional The metallic CuS complexes together to form a special "self-interaction" interface. In the synthesis process, the precursor Mn(S2CNEt2)2 plays a crucial role, it can induce and control the phase transition from Cu1.94S to CuS, and make the copper sulfide polymorph Cu1.94S-CuS nano heterogeneous. The knot can be stable. This unique Cu1.94S-CuS nanoheterojunction can effectively absorb the visible and near-infrared regions of sunlight. The density functional theory calculations show that this special interface can be constructed similar to the "metal-semiconductor" interface structure, thus building a similar type-II heterostructure, which effectively promotes the separation of electrons and holes in the system. Improves the photoelectric conversion performance of the system material.
This method based on precursor-induced synthesis of sulfide heterogeneous nanostructures helps one to precisely control the structure of nanomaterials and gain an in-depth understanding of its formation mechanism. At the same time, this strategy of synthesis of heterogeneous nanostructures with no precious metals participation will provide new ideas for improving and optimizing the photoelectric conversion performance of traditional semiconductors.
Previously, Yu Shuhong's research group also discovered the phenomenon that organic phosphines were complexed with Ag+ and Bi3+ and then reduced at high temperatures into simple silver and gallium. Based on this, a silver-based and thiol-based mechanism was developed. A general synthesis method of nanocrystals and their heterogeneous nanostructures has successfully synthesized a series of silver-based and samarium-based nanomaterials such as Ag, Bi, Ag-Ni3S2, Ag-ZnS, Ag-AgInS2, Ag-Bi, and Bi-Cu7S4. This is a powerful addition to the synthesis of colloidal nanocrystals. The researchers found that silver and antimony chalcogenides have a solubility balance in organic amines. According to Lewis' theory, the organic phosphine in the solution can be complexed with Ag+ and Bi3+, breaking its dissolution balance and releasing more. More Ag+ and Bi3+, in turn, are reduced by organic amines to silver and gallium at high temperatures. Nanocrystals and heterojunctions synthesized by this method have potential applications in catalysis, photoelectric conversion, and biosensing. The results of the relevant studies are published in the American Chemical Society (J. Am. Chem. Soc. 2015, 137(16), 5390-5396).
The above research work has been supported by the National Natural Science Foundation of China's Innovation Research Group, the National Natural Science Foundation of China, the National Major Scientific Research Project, the Frontier Science Key Research Project of the Chinese Academy of Sciences, the Suzhou Nanometer Science and Technology Collaborative Innovation Center, the Nanoscience Excellence Innovation Center of the Chinese Academy of Sciences, and the Hefei University of Science Funding for the Center for Excellence in User Funds.
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