Chemistry

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Browsing Chemistry by Author "Khan, Malik Dilshas"

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    Novel Precursors for the Synthesis of Metal Selenide Nanoparticles, Thin Films and Alloys
    (University of Zululand, 2018) Khan, Malik Dilshas
    Metal selenides are important semiconducting materials and are highly useful in various electronic and/or thermoelectric devices. Different synthetic protocols are available for preparation of metal selenide nanoparticles and/or thin films. Nonetheless, the use of single source precursors is usually advantageous, as they can be used for the synthesis of metal chalcogenide nanocrystals, and are equally suitable for the deposition of thin films. Furthermore, a better control over stoichiometry and phase can be achieved, due to preformed bonds between metal and chalcogen atom. Numerous sulfur based single source precursors have been used successfully for synthesis of variety of metal sulfide nanoparticles and/or deposition of thin films. However, the use of single source precursors with higher chalcogeno congeners, are not well explored. The prime reason is the difficulty in the synthesis of Se/Te based precursors. Only a limited starting material is available and that too are usually highly toxic, such as, phosphines and/or carbon disulfide. Hence, a facile synthetic route, using comparatively less toxic aterials, is highly desired for the synthesis of selenium containing molecular recursors. In this thesis, we have introduced a new one-pot synthesis of metal (Bi, Sn and Sb) selenobenzoate complexes and established their suitability for the synthesis of respective metal selenide nanoparticles, thin films and alloys. The thesis is divided into seven chapters, in which the first chapter gives a comprehensive literature review of all the selenium based single source precursors used until the present for the synthesis of metal selenide nanocrystals and/or thin films. The second chapter describes the synthesis of selenobenzoate ligand and its antimony complex i.e. tris(selenobenzoato)Sb(III) complex. The crystal structure of the complex was elucidated and the complex was used as a suitable single source precursor for the synthesis of Sb2Se3 nanorods by hot injection method and thin films were deposited by the aerosol assisted chemical vapor deposition (AACVD) method. The nanorods synthesized by colloidal method were used for water splitting application. In third chapter, the similar synthetic strategy was used to prepare tris(selenobenzoato)Bi(III) complex and the decomposition of the molecular precursor by hot injection method yields Bi2Se3 nanosheets. Thin films were also deposited at different temperatures on glass substrates and the water splitting efficiency of the oleylamine capped nanosheets was investigated. Both Sb2Se3 and Bi2Se3 shows p-type behavior as cathodic currents were observed for both materials. Similarly, the fourth chapter entails the detail about the use of bis(selenobenzoato)Sn(IV) for the deposition of SnSe thin films and nanosheets. The electrochemical studies indicate bifunctional behavior and the material can behave either as cathodic material and/or anodic material by changing the voltage. In chapter 5 and 6, thio- analogues of bis(selenobenzoato)Sn(IV) and tris(selenobenzoato)Sb(III) i.e. bis(thiobenzoato)Sn(IV) and tris(thiobenzoato)Sb(III) complexes were synthesized and mixture of both chalcogeno- complexes were used to prepare solid solutions (Sb2(SxSe1-x)3 and SnSxSe1-x) in entire range with excellent stoichiometric control. Sb2(SxSe1-x)3 was prepared by colloidal route using oleylamine as solvent and capping agent, band gap tuning was observed. For SnSxSe1-x solid solution, in addition to colloidal synthesis, solvent-less route was also used and the effect of both routes on structural behavior was investigated. Chapter 7 gives a brief summary of all the chapters and the potential future research plan.
University of Zululand