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Nosang V. Myung - One of the best experts on this subject based on the ideXlab platform.
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Galvanic Displacement reaction of nickel to form one-dimensional trigonal tellurium structures in acidic solutions
Electrochimica Acta, 2020Co-Authors: Jonathan Parker, Yong-ho Choa, Thien-toan Tran, Nosang V. MyungAbstract:Abstract Trigonal tellurium micro-wires and tubes were synthesized by Galvanic Displacement of nickel in acidic sulfate solutions where the growth mechanism was elucidated using various electroanalytical methods and material characterization. The effects of solution composition, including concentrations of tellurium precursor and sulfate, were studied. The transition from micro-wires to tubes with an increase in HTeO2+ concentration was observed, which might be attributed to the comparable diffusion length scale of tellurium on the cylindrical seed surface to the radius of the seed. On the other hand, increasing H2SO4 concentration led to transformation of microtubes to microwires owing to reduction deposition rate and limited mass transfer of HTeO2+ ions. The effect of other anions (i.e., Cl− and NO3−) on Galvanic Displacement reaction was also studied. As a strong oxidant, HNO3 dissolved nickel faster than SO4−2 and Cl−, but showed slower tellurium deposition tellurium nanowires, which might be due to co-reduction of nitrate ions. The preferential adsorption of Cl− increased both dissolution of nickel and the deposition of tellurium, resulting in larger tellurium microtubes.
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Controlled growth of gold nanocrystals on biogenic As-S nanotubes by Galvanic Displacement.
Nanotechnology, 2018Co-Authors: Fang Liu, Wilfred Chen, Nosang V. MyungAbstract:Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques while alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Here, gold (Au) nanocrystals were grown on the surface of the microbiologically formed As-S nanotubes through the process of Galvanic Displacement. The size and organization of the synthesized Au nanocrystals were affected by the pH dependent speciation of HAuCl4 precursors as well as the initial ratio of As-S/HAuCl4. We found that as pH increased, the Au nanocrystals grown on As-S nanotubes had smaller sizes but were more likely to assemble in one-dimension along the nanotubes. At a proper initial ratio of As-S/HAuCl4, Au nanotubes were formed at pH 6.0. The mechanism of Au nanostructures formation and the synthesis process at different pHs were proposed. The resulting Au nanoparticle/As-S nanotube and Au nanotube/As-S nanotube hetero-structures may provide important properties to be used for novel nano-electronic devices.
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Morphological Evolution of Te and Bi2Te3 Microstructures during Galvanic Displacement of Electrodeposited Co Thin Films
Electrochimica Acta, 2017Co-Authors: Hoyoung Suh, Nosang V. Myung, Kimin Hong, Jinseong Noh, Ji Hyun Lee, Seok-hoon Lee, Jin-gyu KimAbstract:Co thin films with different crystalline structures including preferred orientation and grain size were electrodeposited from electrolytes containing an additive N-Dimethyldithiocarbamic acid ester, sodium salt, (DPS). Subsequently, the Co electrodeposits were converted to Te and Bi2Te3 via Galvanic Displacement reaction (GDR) processes. The morphologies of the produced Te and Bi2Te3 exhibited granular structures including whiskers and dendrites. Structural analyses showed that the microstructures strongly depended on the crystalline structure of the original Co thin films, which were also affected by the concentration of DPS. The formation mechanism of the Te whiskers and Bi2Te3 dendrites were elucidated by various analyses.
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synthesis of pbte and pbte te nanostructures by Galvanic Displacement of cobalt thin films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
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Synthesis of PbTe and PbTe/Te Nanostructures by Galvanic Displacement of Cobalt Thin Films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
Yong-ho Choa - One of the best experts on this subject based on the ideXlab platform.
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Galvanic Displacement reaction of nickel to form one-dimensional trigonal tellurium structures in acidic solutions
Electrochimica Acta, 2020Co-Authors: Jonathan Parker, Yong-ho Choa, Thien-toan Tran, Nosang V. MyungAbstract:Abstract Trigonal tellurium micro-wires and tubes were synthesized by Galvanic Displacement of nickel in acidic sulfate solutions where the growth mechanism was elucidated using various electroanalytical methods and material characterization. The effects of solution composition, including concentrations of tellurium precursor and sulfate, were studied. The transition from micro-wires to tubes with an increase in HTeO2+ concentration was observed, which might be attributed to the comparable diffusion length scale of tellurium on the cylindrical seed surface to the radius of the seed. On the other hand, increasing H2SO4 concentration led to transformation of microtubes to microwires owing to reduction deposition rate and limited mass transfer of HTeO2+ ions. The effect of other anions (i.e., Cl− and NO3−) on Galvanic Displacement reaction was also studied. As a strong oxidant, HNO3 dissolved nickel faster than SO4−2 and Cl−, but showed slower tellurium deposition tellurium nanowires, which might be due to co-reduction of nitrate ions. The preferential adsorption of Cl− increased both dissolution of nickel and the deposition of tellurium, resulting in larger tellurium microtubes.
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synthesis of pbte and pbte te nanostructures by Galvanic Displacement of cobalt thin films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
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Synthesis of PbTe and PbTe/Te Nanostructures by Galvanic Displacement of Cobalt Thin Films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
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Branched tellurium hollow nanofibers by Galvanic Displacement reaction and their sensing performance toward nitrogen dioxide.
Nanoscale, 2013Co-Authors: Hosik Park, Chong Hyun Chang, Yong-ho Choa, Hyunsung Jung, Miluo Zhang, N. George Ndifor-angwafor, Nosang V. MyungAbstract:Electrospinning and Galvanic Displacement reaction were combined to synthesize ultra-long hollow tellurium (Te) nanofibers with controlled dimensions, morphology and crystallinity by simply tailoring the electrolyte concentration applied. Within different morphologies of nanofibers, the branched Te nanostructure shows the greatest sensing performance towards NO2 at room temperature.
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Template-free synthesis of vertically oriented tellurium nanowires via a Galvanic Displacement reaction
Electrochimica Acta, 2013Co-Authors: Da-bok Jeong, Yong-ho Choa, Hosik Park, Young-in Lee, Miluo Zhang, Jae-hong Lim, Joun Lee, Nosang V. MyungAbstract:Abstract The scalable, high-throughput, cost-effective synthesis of high-quality tetragonal tellurium (t-Te) nanowires by the Galvanic Displacement reaction of Si on a 4-in. Si wafer is demonstrated. This method does not require any heterogeneous seeds, physical templates, or surfactants. In addition, because seed nucleation and growth are both instantaneous, the synthesized nanowires had uniform lengths across the substrate. Furthermore, the effects of the deposition conditions, including the solution composition and reaction time and temperature, on the morphologies, dimensions, and crystallinities of the Te nanowires were analyzed to investigate the growth mechanism. The synthesized t-Te nanowires exhibited excellent piezoelectric properties, with the output current being as high as −75.0 nA.
Roya Maboudian - One of the best experts on this subject based on the ideXlab platform.
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Ultrasmooth gold thin films by self-limiting Galvanic Displacement on silicon.
ACS applied materials & interfaces, 2011Co-Authors: Albert Gutés, Carlo Carraro, Roya MaboudianAbstract:Galvanic Displacement (GD), a type of electroless deposition, has been used to obtain ultrasmooth gold thin films on silicon ⟨111⟩. The novel aspect of the method presented herein is the absence of fluoride ions in the liquid phase, and its principal advantage when compared to previous efforts is that the process is inherently self-limiting. The self-limiting factor is due to the fact that in the absence of fluorinated species, no silicon oxide is removed during the process. Thus, the maximum gold film thickness is achieved when elemental silicon is no longer available once the surface is oxidized completely during the Galvanic Displacement process. X-ray photoelectron spectroscopy has been used as a tool for thickness measurement, using the gold to silicon ratio as an analytical signal. Three gold plating solutions with different concentrations of KAuCl4 (2, 0.2, and 0.02 mM) have been used to obtain information about the formation rate of the gold film. This XPS analysis demonstrates the formation of go...
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Micellar block copolymer templated Galvanic Displacement for epitaxial nanowire device integration
Journal of Materials Chemistry, 2011Co-Authors: Gregory S. Doerk, Carlo Carraro, Ian Laboriante, Charles Dhong, Christine Politi, Roya MaboudianAbstract:New strategies for catalyst nanoparticle placement in arbitrary patterns and non-planar geometries will likely accelerate the large scale device integration of epitaxial semiconductor nanowires (NWs) grown through the vapor-liquid-solid (VLS) process. Herein we report a technique for rational metal catalyst nanoparticle deposition based on Galvanic Displacement onto semiconductor surfaces through block copolymer micelle templates. Nanoparticle volumes and areal densities are controlled by the time in the plating solution and by mixing homopolymer with the micelle suspension, respectively. Above a minimal nanoparticle diameter, the mean diameters of epitaxial VLS-grown Si NWs scale directly with mean sizes of the template deposited nanoparticle seeds from which they are grown. The substrate selectivity and conformality of Galvanic Displacement makes possible two-level micro/nano-patterning in a variety of geometries by applying micellar templates over photolithographically patterned masks; the growth of single sub-50 nm diameter Si NWs in 600–700 nm diameter wells demonstrates a feature size reduction greater than one order of magnitude. Two-point electrical measurements across single NWs or a few NWs epitaxially bridging silicon-on-insulator electrodes after ex situ doping demonstrate the viability of this approach for epitaxial NW device integration.
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A simple soft lithographic nanopatterning of gold on gallium arsenide via Galvanic Displacement.
Journal of nanoscience and nanotechnology, 2010Co-Authors: Hyuneui Lim, Jung Hyun Noh, Dae-geun Choi, Wan-doo Kim, Roya MaboudianAbstract:Nanoscale patterning of gold layers on GaAs substrate is demonstrated using a combination of soft lithographic molding and Galvanic Displacement deposition. First, an electroless deposition method has been developed to plate gold on GaAs with ease and cost-effectiveness. The electroless metallization process is performed by dipping the GaAs substrates into a gold salt solution without any reducing agents or additives. The deposition proceeds via Galvanic Displacement in which gold ions in the aqueous solution are reduced by electrons arising from the GaAs substrate itself. The deposition rate, surface morphology and adhesion property can be modulated by the plating parameters such as the choice of acids and the immersion time. Second, soft lithographic patterning of nanodots, nanorings, and nanolines are demonstrated on GaAs substrates with hard-polydimethylsiloxane (h-PDMS) mold and plasma etching. This method can be easily applied to the metallization and nanopatterning of gold on GaAs surfaces.
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Silver Nanostructures on Silicon Based on Galvanic Displacement Process
The Journal of Physical Chemistry C, 2009Co-Authors: Albert Gutés, Carlo Carraro, Ian Laboriante, Roya MaboudianAbstract:A simple and versatile process, based on a Galvanic Displacement reaction, is presented that provides controlled growth of different silver structures on silicon including thin films, nanocrystals, nanoparticles, and more complex structures termed nanodesert rose. Structure selection is achieved by choosing a suitable ratio of AgF:KF in the plating solution, in the absence of any other additive, and by changing immersion times and precursor concentrations. We demonstrate the usefulness of some of these nanostructures as reproducible surface-enhanced Raman spectroscopy substrates.
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Dynamics of Copper Deposition onto Silicon by Galvanic Displacement
Journal of The Electrochemical Society, 2008Co-Authors: Calvin P. Darosa, Enrique Iglesia, Roya MaboudianAbstract:Copper was deposited onto silicon rotating-disk electrodes in 3.0 M HF to determine the effects of boundary-layer mass transfer and surface reaction kinetics on Cu deposition rates. For all solution compositions tested ([CuSO 4 ] = 0.0010 - 0.020 M, [HF] = 3.0 M), the Cu deposition rate was proportional to the concentration of Cu 2+ and was under mixed diffusion and surface kinetic control. HF was used to dissolve oxidized Si, and a stoichiometry of one Cu atom deposited for each Si atom that is oxidized and dissolved was deduced from a combination of UV-visible spectroscopy and mass change experiments. These results indicate that Si dissolves as Si 2+ , not Si 4+ , as is commonly assumed for Galvanic Displacement. Mixed-potential theory was used to further analyze the reaction mechanism, and deposition rates and open-circuit potential values predicted from this method agreed well with experimental results during the initial stages of Cu deposition. Deposition rates decreased abruptly when film thicknesses exceeded 150 nm, and optical microscopy revealed buckling in these Cu films. This buckling occurred in response to compressive stresses in the films and decreased deposition rates by partially detaching Cu films from the Si substrate.
Chong Hyun Chang - One of the best experts on this subject based on the ideXlab platform.
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synthesis of pbte and pbte te nanostructures by Galvanic Displacement of cobalt thin films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
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Synthesis of PbTe and PbTe/Te Nanostructures by Galvanic Displacement of Cobalt Thin Films
Electrochimica Acta, 2014Co-Authors: Chong Hyun Chang, Yong-ho Choa, Miluo Zhang, Jae-hong Lim, Su-dong Park, Nosang V. MyungAbstract:Lead telluride (PbTe) nanostructures were synthesized by Galvanic Displacement reaction of electrodeposited Co thin films where the effect of [Pb2+]/[HTeO2+] ratio in the electrolyte, the thickness of sacrificial layer, and the reaction time on the surface morphology and composition were systematically investigated. The composition of PbTe nanostructures were strongly dependent on the [Pb2+]/[HTeO2+] ratio in the electrolyte where the deposited contents were varied from Te-rich (i.e., Pb20Te80) to Pb-rich (i.e., Pb69Te31) PbTe. The surface morphologies varied from x-shaped, cucumber-like, and flower-like to dendrite structures. TEM analysis showed that x-shaped PbTe nanostructures grew in a single crystalline face-centered cubic (FCC) structure along the [100] and [110] directions.
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Branched tellurium hollow nanofibers by Galvanic Displacement reaction and their sensing performance toward nitrogen dioxide.
Nanoscale, 2013Co-Authors: Hosik Park, Chong Hyun Chang, Yong-ho Choa, Hyunsung Jung, Miluo Zhang, N. George Ndifor-angwafor, Nosang V. MyungAbstract:Electrospinning and Galvanic Displacement reaction were combined to synthesize ultra-long hollow tellurium (Te) nanofibers with controlled dimensions, morphology and crystallinity by simply tailoring the electrolyte concentration applied. Within different morphologies of nanofibers, the branched Te nanostructure shows the greatest sensing performance towards NO2 at room temperature.
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Synthesis of tellurium nanotubes by Galvanic Displacement
Electrochimica Acta, 2010Co-Authors: Youngwoo Rheem, Chong Hyun Chang, Deok-yong Park, Kyu Hwan Lee, Carlos M. Hangarter, Yong-soo Jeong, Nosang V. MyungAbstract:Abstract Tellurium nanotubes with controlled diameter and wall thickness were synthesized by Galvanic Displacement of cobalt nanowires and their temperature dependent field effect transistor and magnetoresistance properties were systematically investigated. The nanotube diameter was slightly larger than the sacrificial cobalt nanowire diameter with a wall thickness of range from 15 to 30 nm depending on the diameter of cobalt nanowires. Te nanotubes show p-type semiconducting property with the field effect carrier mobility of approx. 0.01 cm 2 /V s which is relatively lower than other 1D nanostructure. Low mobility might be attributed to porous morphology with small grain size (
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Bi and Te thin films synthesized by Galvanic Displacement from acidic nitric baths
Electrochimica Acta, 2010Co-Authors: Chong Hyun Chang, Deok-yong Park, Youngwoo Rheem, Yong-ho Choa, Dong Hyuk Shin, Nosang V. MyungAbstract:Bismuth (Bi) and tellurium (Te) thin films were formed by Galvanic Displacement of different sacrificial iron group thin films [i.e. nickel (Ni), cobalt (Co) and iron (Fe)] where the formation was systematically investigated by monitoring the change of open circuit potential (OCP), surface morphology and microstructure. The surface morphologies and crystal structures of Galvanically displaced Bi or Te thin films strongly depended on the type and thickness of the sacrificial materials. Continuous Bi thin films were successfully deposited with the sacrificial Co. However, dendrites and nanoplatelets were formed from the Ni and Fe thin films. Te thin films were synthesized with all the three sacrificial thin films. Chemical dissolution rate of the sacrificial thin films and mixed potential strongly influenced formation of Bi or Te thin films.
Chan-hwa Chung - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of dendritic silver-coated copper powders by Galvanic Displacement reaction and their thermal stability against oxidation
Applied Surface Science, 2016Co-Authors: Yu Seon Park, Chang Yong An, Padmanathan Karthick Kannan, Nary Seo, Kai Zhuo, Tae Kyong Yoo, Chan-hwa ChungAbstract:Two steps of wet chemical processes have been developed for the preparation of core-shell nanostructures of copper and silver, which is a facile and low cost method for the production of large quantity of dendritic powders. First step involves a Galvanic Displacement reaction with hydrogen evolution which is the motive force of spontaneous electrochemical reaction. To achieve the core-shell structure, silver has been coated on the dendritic copper using the Galvanic Displacement reaction. The dendritic silver-coated copper powders exhibit high surface-area, excellent conductivity, and good oxidation resistance. It has been found that silver-coated copper powders maintain the electrical conductivity even after annealing at 150 °C for several to tens of minutes, thus it is a promising material and an alternative to pure silver powders in printed electronics application.
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Dendritic nanoporous nickel oxides for a supercapacitor prepared by a Galvanic Displacement reaction with chlorine ions as an accelerator
RSC Advances, 2013Co-Authors: Kai Zhuo, Myung-gi Jeong, Chan-hwa ChungAbstract:Dendritic nanoporous nickel oxide and tube-like nickel–tin oxide electrodes were prepared by a Galvanic Displacement reaction in an aqueous electrolyte containing chlorine ions which dramatically accelerated the reaction. The nanoporous nickel oxide showed a capacitance of 1242 F g−1, 97.4% of which was retained even after 5000 charge–discharge cycles.
