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    Home > Professor Yu Shuhong and his collaborators have made important progress in the field of pulsed axial epitaxial growth of colloidal quantum dots nanowire segmented heterojunction

    Professor Yu Shuhong and his collaborators have made important progress in the field of pulsed axial epitaxial growth of colloidal quantum dots nanowire segmented heterojunction

    • Last Update: 2018-12-10
    • Source: Internet
    • Author: User
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    The design of new semiconductor nano materials to capture solar energy and achieve efficient photochemical conversion is one of the ideal ways to solve the current global energy and environmental crisis As an important photocatalyst material, colloidal quantum dots have been widely used in the field of solar energy conversion due to their tunable optical and electrical properties However, the suspended bonds on the surface of the QDs will lead to a large number of trap states, which will strongly localize the carriers and prevent them from further participating in the surface chemical reactions At present, how to achieve both surface passivation and charge transfer is still a challenge Recently, Professor Yu Shuhong of University of science and technology of China and Professor Sargent of University of Toronto have designed a "pulsed axial epitaxial growth" method, and successfully prepared one-dimensional colloidal quantum dot nanowire segmented heterojunction with adjustable size and structure In this paper, ZnS nanowires are used to selectively passivate the crystal surface of CdS quantum dots At the same time, the effective passivation of the quantum dot surface and the effective transfer of photogenerated carriers are realized The research results were published in nature communications (DOI: 10.1038 / s41467-018-07422-4) under the title of "pulsed axial affinity of massive quantum dots in nanowires enablesfacet selective passage" The first author of this paper is Li Yi, a doctoral student, and Zhuang Taotao, a postdoctoral student at the University of Toronto Researchers use nanowires to selectively passivate the (111) crystal surface with high defect concentration, and at the same time to ensure the efficient transfer of photo generated carriers to the side of the quantum dot for oxidation-reduction reaction, so as to achieve high-efficiency photochemical conversion However, epitaxial growth of quantum dots and nanowires requires periodic switching of reaction precursors to alternately grow quantum dots and nanowires, which is usually difficult to achieve in the traditional one pot colloidal chemical synthesis Based on their previous work in Liquid-Solid-Solid catalytic growth of one-dimensional nanostructures, the research team proposed a new strategy of "pulse axial epitaxial growth" to synthesize colloidal semiconductor nanocrystals The theoretical calculation shows that the difference of embedded energy between Zn and CD atoms in Ag 2S solid-phase catalyst makes CDs grow preferentially in the presence of CD precursor, so the structure parameters of CdS quantum dots ZnS nanowires can be adjusted by controlling the addition of CD precursor This method has high flexibility and can control the size, quantity, spacing and crystal phase of quantum dots precisely Taking photocatalytic water decomposition as an example, the researchers found that the photocatalytic hydrogen production efficiency of this quantum dot nanowire structure was significantly improved compared with that of pure CdS quantum dots, and the catalytic activity of unit mass CDs was one order of magnitude higher than that of pure quantum dots Combining with the time-resolved pump probe technique and theoretical calculation, the researchers found that after ZnS nanowires selectively passivated the crystal surface of CdS quantum dots (111), the trap state density of (111) surface was significantly reduced, thus the carrier localization degree was reduced, the carrier lifetime was prolonged, and the carrier migration to the catalyst surface was favorable for the reaction In this study, a new strategy of "pulse axial epitaxial growth" was proposed to synthesize colloidal semiconductor nanocrystals One dimensional colloidal quantum dot nanowire segmented heterojunction with adjustable size and structure was successfully prepared through crystal surface selective passivation, which provides a new way for the design and development of new efficient Photocatalysts in the future In addition, the synthesis strategy is expected to expand to other colloidal quantum dot systems and realize the fine control of its structural parameters by improving the synthesis method, which is expected to show unique application value in laser, single photon source and single electron detection This research is supported by the innovation research group of NSFC, NSFC key fund, national major scientific research plan, key research project of cutting edge science of Chinese Academy of Sciences, nanoscience excellence and innovation center of Chinese Academy of Sciences, Suzhou nanotechnology Collaborative Innovation Center, Hefei University Science Center excellent user fund, etc.
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