Electrochemical Synthesis, Characterization And Influencing Factors Of Dendritic Micro-/Nano-materials

The branched structures have large surface areas, allow for heterostructures, and can easily form continuous networks compared with other structures. Therefore, the fabrication of the dendritic structures may pave a new pathway for wide applications of the future nanodevices. In this thesis, we designed a simple, fast, energy-efficient electrodeposition route to successfully synthesize dendritic metal and metal telluride micro/nanomaterials. The phase and morphology of the as-prepared products were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometer (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron pattern (SAED) and scanning electron microscopy (SEM). Some factors affecting the formation of dendritic micro-/nano-structures, such as the initial amount of reactants, complexing agents, surfactants, deposition current or voltage, were systematically investigated. The time-dependent shape-evolution process of the products was observed. The main contents are summarized as follows.1. Dendritic Bi nanostructures are synthesized via a facile galvanostatic electrodeposition route in air at room temperature, employing Bi(NO₃)₃·5H₂O as the reactant, employing the deposition current of 4 mA for 5 min. The time-dependent shape evolution experiments proved dendritic Bi nanostructures originated from the epitaxial growth of irregular nanoparticles. Experiments showed that the morphology of the final product could be markedly affected by some factors including the existence state of Bi(III) in the system, the depositing time and some complex agents. Also, the as-obtained product was found to have potential applications in the detection of trace metal such as Cd2+ ions in water resource.2. Hierarchical Pb microstructures have been successfully synthesized via a facile electrochemical deposition route in air at room temperature, employing Pb(NO₃)₂ as the precursor in the presence of tartaric acid. The time-dependent shape evolution proved hierarchical Pb microstructures originated from the epitaxial growth of irregular particles. It was found that tartaric acid and Pb(NO₃)₂ were indispensable in the formation of hierarchical Pb microstructures. Experiments also indicated that the anionic surfactant SDBS could strongly affect on the morphology of the final product; and the cationic surfactant CTAB could only slightly influenced.3. PbTe dendrites were synthesized via a simple potentiostatic electrochemical deposition method at room temperature, employing the deposition potential of -0.2 V for 5 min. It was found that the morphology of the product could be affected by some parameters including complexants, Pb²⁺ ion sources and deposition potentials. The morphology of PbTe microstructures could be tuned by the molar ratio of ethylendiaminetetraacetic acid (EDTA-2Na)/tartaric acid and the amount of tartaric acid. A time-dependent shape evolution process showed that the growth of feather-like PbTe dendrites underwent three stages from near-spherical nanoparticles, to flowerlike structures, finally to featherlike dendrites; while the growth of nanoflake-stacked thicket-like PbTe microstructures underwent a process from irregular nanoparticles, to near-spherical particles, to flowerlike particles built up of nanoplates, to undeveloped thicket-like microstructures, and finally to nanoflake-stacked thicket-like microstructures.4. Polycrystalline Cu₇Te₄ dendrites were successfully synthesized via a simple galvanostatic electrochemical deposition method at room temperature, employing a mixed solution containing Cu(CH₃COO)₂, Na2TeO3 and nitric acid as the electrolyte. Cu₇Te₄ dendrites were deposited at the current of 16 mA for 5 min. Some factors influencing the formation of dendritic Cu₇Te₄ microstructures were systematically investigated, including the depositing current, complexant, surfactant, the original amount of Cu(CH₃COO)₂, and Cu²⁺ ion sources. Experiments showed that the low deposition current and concentration of Cu(CH₃COO)₂ was unfavorable for the formation of dendritic Cu₇Te₄ microstructures constructed by nanoparticles. A time-dependent shape evolution process proved that dendritic Cu₇Te₄ microstructures originated from the oriented assembly of nanoparticles.