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Synthesis of Magnetic, Metallic and Semiconductor Nanocrystals by Using Metal Acetylacetonates as Precursors

Author: LiXiaoMin
Tutor: LiLinSong
School: Henan University
Course: Physical and chemical
Keywords: metal acetylacetonate semiconductor magnetic nanocrystals
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 61
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Abstract


Nanocrystals have attracted a great deal of attention due to their fundamental size- and shape-dependent optical, magnetic, dielectric, and other unique properties, along with their many important technological applications in light emitting diodes （LED）, lasers, solar cells, and so on. Therefore, the development of new techniques to synthesize different kinds of high quality size- and shape- controlled nanocrystals has been widely studied in the last two decades. Until now, there have been many kinds of methods to synthesize the various nanomaterials, which include magnet, metal, and semiconductor nanomaterials, such as sol-gel, deposition, hydrothermal, solvothermal and so on. Though there are many routes to synthesize various nanomaterials, but up to the present there is no one appropriate activity metallic compound was found to synthesize all kinds of nanoparticles. In order to fully investigate the technological potentialities of nanomaterials, the availability of a universal route or metallic compound which can provide great convenience to both flask experiments and a large-scale industrial preparation is urgently required. In this work, metal acetylacetonate [M（acac）x] were choosen as an universal precursors to synthesize a wide variety of nanocrystalsThis thesis includes the following main aspects:In chapter 2, high-quality, monodisperse, and size-controlled Fe3O4, Ag, and bifunctional Fe3O4/Ag heterodimer nanocrystals （NCs） have been synthesized successfully. In the synthesis of Fe3O4 NCs, dodecanol was chosen as the substitute of 1, 2-hexadecanediol and“size control”was achieved by simply adjusting the proportion among the ligands instead of utilizing seed-mediated growth. In the synthesis of Ag NCs, organometallic silver acetylacetonate （Agacac） was used as precursors and tunable particle size could be easily obtained by adjusting the reaction temperatures. By using different sized Fe3O4 NCsasseeds, Fe3O4/Ag heterodimer NCs with particle sizes tuned from 5 to 16 nm for Fe3O4 and 4 to 8 nm for Ag were successfully synthesized and superparamagnetism were maintained.In chapter 3, a general method has been established for the syntheses of semiconductor nanocrystals by using metal acetylacetonates as universal precursors. Using this method, uniform-sized semiconductor nanocrystals including binary and ternary sulfide nanocrystals, binary and ternary selenide nanocrystals are successfully synthesized and the qualities of as-prepared nanocrystals were kept compared with the nanocrystals synthesized by using other sorts of precursors. The shapes of as-prepared nanocrystals are well-controlled by changing the type of organic ligands.In chapter 4, a facile, inexpensive, and reproducible route was demonstrated for the syntheses of self-assembled Cu2S 1D columnar, 2D raftlike, and 3D stratiform from anisotropic hexagonal nanoplates. It was found that Sn-X complex could inhibit the growth of <001> direction of monoclinic Cu2S nanocrystals which further induced the formation of the hexagonal lamellar. The conductivity of the self-assembled nanoplates was significantly improved because of the short interparticle spacing （1.0 nm） linked by the Sn-X complex. We believe that the methodology of constructing self-assembled nanostructures reported in this chapter may turn over a new leaf in device-level manipulation of nanocrystals and many nanocrystal-related potential applications.

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