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RISS 인기검색어
- 검색키워드
- 저자 : Nosang V. Myung (검색결과 50 건)
- 무료
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- 유료
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Electrodeposition of Dense Lead Telluride Thick Films in Alkaline Solutions
Wu, Tingjun,Lee, Hong-Kee,Myung, Nosang V. The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.14
<P>Dense PbTe thick films were electrodeposited in alkaline solutions by an underpotential deposition mechanism of Pb on overpotential deposited Te. The composition of Pb is critical for the material properties. The composition of the electrodeposited PbTe films was Te-rich. Although the applied potential had no substantial effect on the Pb composition, it needs to be in the proper range (from -0.8 to -1.1 V vs. sat. Ag/AgCl) to avoid further reduction of Te to Te-2(2-) or keep the reduction of Te to Te-2(2-) at a low reaction rate. To deposit dense thick films the pH must be maintained in the range 10.5 to 12.3. Higher TeO32- concentrations and lower pH values decreased the Pb composition but increased deposition rates. Varying the TeO32- concentration changed the surface morphology of thick PbTe films, but all the thick films were found to be dense in the SEM cross section images. The ratio of EDTA(4-)/Pb2+ is also a critical effect, and the data showed that 7.5 was the optimum ratio with the given conditions, where the electrodeposited PbTe film was dense without cracks. A high deposition rate (approx. 163 mu m/h) was achieved by high TeO32- concentrations (i.e., 550 mM) and at the deposition potential of 1.05 V vs sat. Ag/AgCl. The as-deposited PbTe films have relatively high Seebeck coefficient (i.e., 524 mu V/K), but low electrical conductivity compared to bulk counterpart which might be attributed to lower crystallinity of PbTe with embedded Te nanocrystals. (C) 2016 The Electrochemical Society. All rights reserved.</P>
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Zhang, Miluo,Brooks, Lauren L.,Chartuprayoon, Nicha,Bosze, Wayne,Choa, Yong-ho,Myung, Nosang V. American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.1
<P>A Schottky contact-based hydrogen (H<SUB>2</SUB>) gas sensor operable at room temperature was constructed by assembling single-walled carbon nanotubes (SWNTs) on a Si/SiO<SUB>2</SUB> substrate bridged by Pd microelectrodes in a chemiresistive/chemical field effect transistor (chemFET) configuration. The Schottky barrier (SB) is formed by exposing the Pd–SWNT interfacial contacts to H<SUB>2</SUB> gas, the analyte it was designed to detect. Because a Schottky barrier height (SBH) acts as an exponential bottleneck to current flow, the electrical response of the sensor can be particularly sensitive to small changes in SBH, yielding an enhanced response to H<SUB>2</SUB> gas. The sensing mechanism was analyzed by <I>I–V</I> and FET properties before and during H<SUB>2</SUB> exposure. <I>I–V</I><SUB><I>sd</I></SUB> characteristics clearly displayed an equivalent back-to-back Schottky diode configuration and demonstrated the formation of a SB during H<SUB>2</SUB> exposure. The <I>I–V</I><SUB><I>g</I></SUB> characteristics revealed a decrease in the carrier mobility without a change in carrier concentration; thus, it corroborates that modulation of a SB via H<SUB>2</SUB> adsorption at the Pd–SWNT interface is the main sensing mechanism.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-1/am404328g/production/images/medium/am-2013-04328g_0008.gif'></P>
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Xiao, Feng,Yoo, Bongyoung,Lee, Kyu-Hwan,Myung, Nosang V IOP Pub 2007 Nanotechnology Vol.18 No.33
<P>A wide range of (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> thin films and nanowires were electrodeposited from acidic tartaric–nitric baths. Initially, (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> thin films were electrodeposited on gold substrates to investigate the effect of the deposition potential and electrolyte composition on film composition. After these investigations, (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> nanowires were potentiostatically electrodeposited using polycarbonate templates as scaffolds. The deposition conditions strongly influenced the deposit composition, crystal structures, and electrical properties of the nanowires. The preferential crystal orientation of the nanowires shifted from a {110} orientation at −20 mV to a {015} orientation at −100 mV. The temperature dependent <I>I–V</I> characteristics of bundle nanowires indicated that the nanowires were semiconductors with negative temperature coefficient of resistivity. The thermal activation energies were 0.20 eV for Bi<SUB>1.8</SUB>Sb<SUB>0.1</SUB>Te<SUB>3.1</SUB> and 0.49 eV for (Bi<SUB>0.3</SUB>Sb<SUB>0.7</SUB>)<SUB>2</SUB>Te<SUB>3</SUB> nanowires, respectively.</P>
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Kim, Jiwon,Lee, Joo-Youl,Lim, Jae-Hong,Myung, Nosang V. Elsevier 2016 ELECTROCHIMICA ACTA Vol.196 No.-
<P><B>Abstract</B></P> <P>Silver antimony telluride (AgSbTe<SUB>2</SUB>) thin films were fabricated by a simple and cost-effective electrodeposition method for the first time. To investigate the effects of crystallinity and composition on the films’ thermoelectric (TE) properties, amorphous Ag<SUB>x</SUB>Sb<SUB>y</SUB>Te<SUB>z</SUB> solid solutions of various compositions were electrodeposited by tailoring the [Ag<SUP>+</SUP>] concentration in the electrolytes, followed by a thermally driven solid-state amorphous-to-nanocrystalline phase transition. Because of the lower carrier concentration in the nanocrystalline phases, higher Hall mobility and Seebeck coefficients, almost twice as high as those observed in the bulk materials, resulted in enhanced power factors of 90–553μW/mK<SUP>2</SUP>. The maximum power factor was obtained from stoichiometric AgSbTe<SUB>2</SUB> thin films. The reported power factors are highly comparable to other values reported for electrodeposited p-type V–VI compounds. The improvement achieved in the TE properties of electrodeposited AgSbTe<SUB>2</SUB> thin films demonstrates the feasibility of the use of these films as p-type legs in room-temperature operations.</P>
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Zhang, Miluo,Kim, Jiwon,Kim, Seil,Park, Hosik,Jung, Hyunsung,Ndifor-Angwafor, N. George,Lim, Jaehong,Choa, Yongho,Myung, Nosang V. American Chemical Society 2014 Chemistry of materials Vol.26 No.8
<P>A cost-effective process that combines electrospinning and a galvanic displacement reaction was utilized to synthesize ultralong hollow Pb<SUB><I>x</I></SUB>Se<SUB><I>y</I></SUB>Ni<SUB><I>z</I></SUB> nanofibers with controlled dimensions, morphology, composition, and crystal structure. Ni nanofibers were electrospun with an average diameter of 150 nm and were used as the sacrificial material for the galvanic displacement reaction. The composition and morphology of the Pb<SUB><I>x</I></SUB>Se<SUB><I>y</I></SUB>Ni<SUB><I>z</I></SUB> nanofibers were controlled during the reaction by tuning the concentration of HSeO<SUB>2</SUB><SUP>+</SUP> in the electrolytes. Hollow Pb<SUB><I>x</I></SUB>Se<SUB><I>y</I></SUB>Ni<SUB><I>z</I></SUB> nanofibers with smooth surfaces were obtained from the low-concentration HSeO<SUB>2</SUB><SUP>+</SUP> solution (i.e., 0.01 and 0.05 mM), but the hollow nanofibers synthesized from the high-concentration HSeO<SUB>2</SUB><SUP>+</SUP> solution (i.e., 1 mM) have rough outer surfaces with nanocrystal protrusions. The Pb content of the nanofibers’ composition was varied from 3 to 42% by adjusting the HSeO<SUB>2</SUB><SUP>+</SUP> concentration. The thermoelectric properties of the nanofiber mats were characterized, and the highest Seebeck coefficient of approximately 449 μV/K at 300 K was found for the Pb<SUB>37</SUB>Se<SUB>59</SUB>Ni<SUB>4</SUB> nanofiber mat.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-8/cm4041067/production/images/medium/cm-2013-041067_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm4041067'>ACS Electronic Supporting Info</A></P>
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Biogenic Formation of As-S Nanotubes by Diverse Shewanella Strains
Jiang, Shenghua,Lee, Ji-Hoon,Kim, Min-Gyu,Myung, Nosang V.,Fredrickson, James K.,Sadowsky, Michael J.,Hur, Hor-Gil American Society for Microbiology 2009 Applied and environmental microbiology Vol.75 No.21
<B>ABSTRACT</B><P><I>Shewanella</I> sp. strain HN-41 was previously shown to produce novel, photoactive, As-S nanotubes via the reduction of As(V) and S2O3<SUP>2−</SUP> under anaerobic conditions. To determine if this ability was unique to this bacterium, 10 different <I>Shewanella</I> strains, including <I>Shewanella</I> sp. strain HN-41, <I>Shewanella</I> sp. strain PV-4, <I>Shewanella alga</I> BrY, <I>Shewanella amazonensis</I> SB2B, <I>Shewanella denitrificans</I> OS217, <I>Shewanella oneidensis</I> MR-1, <I>Shewanella putrefaciens</I> CN-32, <I>S. putrefaciens</I> IR-1, <I>S. putrefaciens</I> SP200, and <I>S. putrefaciens</I> W3-6-1, were examined for production of As-S nanotubes under standardized conditions. Of the 10 strains examined, three formed As-S nanotubes like those of strain HN-41. While <I>Shewanella</I> sp. strain HN-41 and <I>S. putrefaciens</I> CN-32 rapidly formed As-S precipitates in 7 days, strains <I>S. alga</I> BrY and <I>S. oneidensis</I> MR-1 reduced As(V) at a much lower rate and formed yellow As-S after 30 days. Electron microscopy, energy-dispersive X-ray spectroscopy, and extended X-ray absorption fine-structure spectroscopy analyses showed that the morphological and chemical properties of As-S formed by strains <I>S. putrefaciens</I> CN-32, <I>S. alga</I> BrY, and <I>S. oneidensis</I> MR-1 were similar to those previously determined for <I>Shewanella</I> sp. strain HN-41 As-S nanotubes. These studies indicated that the formation of As-S nanotubes is widespread among <I>Shewanella</I> strains and is closely related to bacterial growth and the reduction rate of As(V) and thiosulfate.</P>
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