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Electrochemical Synthesis of Nanomaterials and Their Properties Research

Author: ZhuJinBao
Tutor: YuanGaoQing
School: South China University of Technology
Course: Applied Chemistry
Keywords: Nanomaterials Cu2O ZnO Electrosynthesis Self-assembly Crystal Growth
CLC: TB383.1
Type: Master's thesis
Year: 2010
Downloads: 309
Quote: 2
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Abstract


Two simple and available electrochemical processes with H2O or H2O-EtOH (or polyol)as solvents and relevant metal (Cu, Zn) as sacrificial anode were developed to synthesizeuniform Cu2O (ZnO) nanoparticles in an undivided cell with a constant current in the roomtemperature. The obtained samples were characterized by XRD, SEM, TEM, HR-TEM,UV-Vis and PL.We successfully synthesized cuprous oxide nanocrystals with various shapes and sizesusing H2O or H2O–polyols (glycerol, ethylene glycol and polyethylene glycol 400)mix-solvent as media in the NaCl-NaOH-NaNO3 electrolytic system in the room temperature.The results indicated that electrolytic media and current density had a great influence on theshape of Cu2O nanocrystals. The mono-disperse and uniform sphere Cu2O solid nanospherescould be readily obtained in H2O–glycerol (or H2O–ethylene glycol) mix-solvent (1:1 volumeratio) and current density 5 mA/cm2. The sphere Cu2O solid nanospheres exhibit excellentadsorption ability for organic dyes (methyl orange, fuchsin acid and methyl blue), which isobviously superior to that of the plate-like shape Cu2O prepared in H2O–PEG400(polyethylene glycol 400) mix-solvent. The present work further confirmed that theadsorption ability of Cu2O crystals was related to their size and shape.We easily obtained ZnO hollow nanospheres by using H2O–EtOH mix-solvent as media inthe citrate sodium electrolyte in the room temperature. The mono-disperse and uniform ZnOhollow nanospheres could be obtained in H2O–EtOH mix-solvent (3:2 volume ratio) andcurrent density 5 mA/cm2. selected area electron diffraction (SAED) show as-prepared hollownanospheres exhibit poly-crystals, the influence of media and electrolyte was analyzed in theliterature. The possible mechanism and growth processing was also explainedWe prepared ZnO nanocrystals with various morphologies and sizes by controllingelectrolytic conditions in the citrate trisodium electrolyte. The results indicated that media,additives, pH, ionic liquids and electrolytical concentration could effectively change the shapeof ZnO nanocrystals. The pH value and ionic liquids would change the shape of ZnO fromnanorods to porous nanoflakes. With the increasing of electrolytical concentration, the shape of ZnO nanorods also transformed to poriferous nanoflakes. ZnO nanothreads, nanocubes andnanorods could be obtained via inputting different additives. The as-obtained ZnOnanostructures prepared in various additives exhibited excellent PL ability.In addition, ZnCdS2 (solid solution) nanocrystals with and without doping Ag2S or CuShave been synthesized via a solvothermal process with isopropanol as solvent and polyvinylpyrrolidone (PVP) as surfactant. The experimental results show that preparation conditionsand the nature and concentration of dopants have a great influence on the photoluminescence(PL) spectra of ZnCdS2 nanocrystals. The copper and silver doped ZnCdS2 nanocrystalsexhibit a stronger PL intensity and wider FWHM (full width at half maximum) in the visiblelight region compared with the undoped ZnCdS2. The as-synthesized ZnCdS2 nanocrystalshave selectively adsorption characteristic for methylene blue.

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