Dongmok Whang - Academia.edu (original) (raw)
Papers by Dongmok Whang
Physical chemistry chemical physics : PCCP, Jan 30, 2015
In this work, an easy method to etch monolayer graphene is shown by catalytic oxidation in the pr... more In this work, an easy method to etch monolayer graphene is shown by catalytic oxidation in the presence of ZnO nanoparticles (NPs). The catalytic etching of monolayer graphene, which was transferred to the channel of field-effect transistors (FETs), was performed at low temperature by heating the FETs several times under an inert gas atmosphere (ZnO + C → Zn + CO or CO2). As the etching process proceeded, diverse etched structures in the shape of nano-channels and pits were observed under microscopic observation. To confirm the evolution of etching, current-voltage characteristics of monolayer graphene were measured after every step of etching by catalytic oxidation. As a result, the conductance of monolayer graphene decreased with the development of etched structures. This decrease in conductance was analyzed by percolation theory in a honeycomb structure. Finally, well-patterned graphene was obtained by oxidizing graphene under air in the presence of NPs, where Al was deposited on...
Journal of the Chemical Society, Chemical Communications, 1993
ABSTRACT
Journal of the Chemical Society, Chemical Communications, 1994
Solid State Sciences, 2010
P-type Si nanowire (NW)-based nano-floating gate memory (NFGM) with Au nanoparticles (NPs) embedd... more P-type Si nanowire (NW)-based nano-floating gate memory (NFGM) with Au nanoparticles (NPs) embedded in Al 2 O 3 gate layers is characterized in this study. The electrical characteristics of a representative p-type Si NW-based NFGM exhibit a counterclockwise hysteresis loop indicating the trapping and detrapping of electrons in the Au NP nodes of the NFGM device. The threshold voltage shift of the device is 5.4 V and the device has good retention over a lapse of time of 5 Â 10 4 s. On the other hand, the p-type Si NW-based top-gate device without any Au NPs does not exhibit any significant threshold voltage shift. This observation reveals that the memory behavior of the p-type Si NW-based NFGM is due to the trapping and detrapping of charge carriers in the Au NPs.
Solid-State Electronics, 2011
Electronic characteristics of silicide/silicon interface were studied in the suspended, chemicall... more Electronic characteristics of silicide/silicon interface were studied in the suspended, chemically synthesized silicon nanowires (SiNWs). Step-by-step intrusion of a silicide/Si interface along the axial direction of a suspended silicon nanowire was performed by repeated thermal annealing cycles, and the currentvoltage (I-V) characteristics of the annealed silicide/SiNW/silicide structure were measured at each cycle. The intruded length of the silicide was found to be directly proportional to the total annealing time, but the rate of silicidation was much smaller than previous works on similar silicide/SiNWs. A structural kink with Ni atoms diffused along the sidewall created a secondary source of silicidation, resulting in anomalous I-V characteristics. The measured I-V including this unintentional silicidation in the Si channel was explained by various combinations of Schottky barriers and resistors.
2011 IEEE Nanotechnology Materials and Devices Conference, 2011
ABSTRACT We present the direct measurement of the gate capacitance of a silicon nanowire field ef... more ABSTRACT We present the direct measurement of the gate capacitance of a silicon nanowire field effect transistor using time-domain monitoring of the source current when the gate pulses with various frequencies and amplitudes are applied. The displacement current induced at the gate capacitance is proportional to the derivative of the gate pulse, and it becomes measurable when the rise time of the gate pulse is small enough. The gate capacitance of fF range was successfully measured using our method.
Polyhedron, 1994
A series of new hydridocarbonyl ruthenium(I1) complexes containing chelating diphosphine ligands ... more A series of new hydridocarbonyl ruthenium(I1) complexes containing chelating diphosphine ligands of the type [RuHCl(CO)(PPh,)(L-L)] [L-L = Ph2PCH,PPh, 2, Ph2PCH2CH2PPh2 3, Ph2PCH2CH2CH2PPh2 4, cis-Ph2PCH=CHPPhz 5 and Fe(q5-C5H4PPh2)2 6] has been prepared by the reactions of [RuHCl(CO)(PPh,),] 1 with Ph2PCH,PPh2 [dppm, bis(diphenylphosphino)methane], Ph2PCH2CH2PPh2 [dppe, 1,2bis(diphenylphosphino)ethane], Ph2PCH2CH2CH2PPh2 [dppp, 1,3_bis(diphenylphosphino)propane], cis-Ph2PCH=CHPPh, [dppv, cis-1,2-bis(diphenylphosphino)ethylene] and Fe(q'-C,H$Ph,), [(dppf, l,l'-bis(diphenylphosphino)ferrocene] in boiling PhMe. The compounds 2-6 are moderately stable in solution. The new compounds were characterized by elemental analysis, IR and 'H NMR spectroscopy. Compounds l-6 have been shown to catalyse the homogeneous hydrogenation of the C=C bond of cyclohexene ; some relations between structures and catalytic activities are described. The Arrhenius activation energy of cyclohexene for compound 4 is 33.0 kJ mol-'.
![Research paper thumbnail of The chemistry and catalytic activity of new cationic ruthenium(II) complexes in the hydrogenation of cyclohexene. Crystal structure of [RuH(CO)(PPh3)(P(OMe)3)(Ph2PCH2CH2AsPh2)]ClO4·n−C5H12](https://attachments.academia-assets.com/105534051/thumbnails/1.jpg)
](Polyhedron, 1996
Interaction of neutral ruthenium(II) complexes of the type [RuHCI(CO)(PPh3) (L-L')] [where L-L'= ... more Interaction of neutral ruthenium(II) complexes of the type [RuHCI(CO)(PPh3) (L-L')] [where L-L'= Ph2PCH2CH2PPh2 (dppe), 1; Ph2PCH2CH2CH2PPh2 (dppp), 2; Ph2PCH2CH2AsPh2 (arphos), 3] with AgCIO4 in the presence of L" [L" = P(OMe)3 or PMe3] yielded the new cationic ruthenium(II) complexes [RuH(CO)(PPh3)(L")(L-L')]C104 [where L-L' = dppe, 4; dppp, 5; arphos, 6; L" = PMea, 4; P(OMe)3, 5 and 6]. All the complexes have been characterized by both analytical and spectroscopic (IR and ~H NMR) methods. The structure of a cationic complex 6, [RuH(CO)(PPh3)(P(OMe)3) (arphos)]CIO4" n-C5H12, has been confirmed by single-crystal X-ray diffraction. The Ru atom is octahedrally coordinated with CO, PPh3 and arphos in the equatorial plane and H and P(OMe)3 in the axial positions. In the hydrogenation of cyclohexene, some relations between structures and catalytic activities have been studied. The cationic complexes have shown lower catalytic activities than their neutral analogues.
Organometallics, 1992
[ (3-tert-Butylnorbomadienyl)etho~ymethylene]Fe(CO)~, the iron(0) +inylcarbene complex 2, is obta... more [ (3-tert-Butylnorbomadienyl)etho~ymethylene]Fe(CO)~, the iron(0) +inylcarbene complex 2, is obtained from the reaction of [(3,3-dimethylb~tynyl)ethoxymethylene]Fe(CO)~ (la) with cyclopentadiene a t 25 OC. Complex 2 transforms into the ~3:q1-allylacyl complex 4a via a CO insertion reaction at the original carbene carbon by heating a t 50 "C for 1 h. However, direct formation of allylacyl acyl complexes is observed in reactions of cyclopentadiene with other alkynylcarbene complexes, l b (R = SiMe,), IC (R = cyclohexyl), Id (R = n-propyl), and le (R = phenyl), at 25 "C. Considerable interest has been focused on the chemistry of transition-metal vinylcarbene complexes. They have been involved as key species in a number of noticeable reactions such as alkyne polymerization,' the Diels-Alder reaction,2 formation of bicyclic lactones via a van Halban-White type double-cyclization,3 and reactions of alkynes with metal carbene complexes,4 including the Dotz reaction. There are two types of metal vinylcarbene complexes: T$-and ~7~-types.~ However, to our knowledge, there is no previous examples of iron(0) +vinylcarbene complexes, although iron(I1) 7'-vinylcarbene complexes are known.6 Recently, we have reported the synthesis of iron(0) alkynylcarbene complexes and formation of the q3-vinylcarbene complex 3 in the reaction of the trimethylsilyl-substituted alkynylcarbene complex l b with 2,3-dimethyl-1,3-buta
Microchimica Acta, 2010
Boron-doped diamond electrodes covered with a nanostructured Pt nanoparticle-polyaniline composit... more Boron-doped diamond electrodes covered with a nanostructured Pt nanoparticle-polyaniline composite have been fabricated and employed as sensitive amperometric sensors with low detection limit. A highly conductive borondoped diamond thin film (BDD) was prepared by chemical vapor deposition, and its morphology was characterized by scanning electron microscopy and transmission electron microscopy. The nanostructured composite layer was grown on the BDD electrode by electrochemical deposition of polyaniline and Pt nanoparticles. Glucose oxidase (GOx) was then adsorptively immobilized on the modified BDD electrode. The biosensor displays a large surface area, high catalytic activity of the Pt nanoparticles, efficient electron mediation through the conducting polymer, and low background current of the electrode. The biosensor exhibits an excellent response to glucose, with a broad linear range from 5.9 μM to 0.51 mM, a sensitivity of 5.5 μA•mM −1 , a correlation coefficient (R) of 0.9947, and a detection limit of 0.10 μM. The apparent Michaelis-Menten constant (K M app) and the maximum current density of the electrode are 4.1 mM and 0.021 mA, respectively. This suggests that the immobilized GOx possesses a higher affinity for glucose at the lower K M app , and that the enzymatic reaction rate constitutes the rate-limiting step of the response.
![Research paper thumbnail of Formation of 1,1,12,12-tetramethyl[1.1]silaferrocenophane and poly(ferrocenylsilane) in the reaction of ferrous chloride with the dilithium salt of dicyclopentadienyldimethylsilanes](https://attachments.academia-assets.com/105534050/thumbnails/1.jpg)
](Journal of Organometallic Chemistry, 1995
1,1,12,12-Tetramethyl[1.1]silaferrocenophane (1) and poly(ferrocenylsilane) (2) were formed as th... more 1,1,12,12-Tetramethyl[1.1]silaferrocenophane (1) and poly(ferrocenylsilane) (2) were formed as the major products in the reaction of FeCI z with the dilithium salt of (CsHs)2SiMe 2, and the X-ray crystallography for 1 revealed its molecular structure of an anti conformation.
The Journal of Organic Chemistry, 1994
The reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles 1 with excess (6 equiv) bulky dialky... more The reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles 1 with excess (6 equiv) bulky dialkylamines such as diethyl-, din -propyl-, and din -butylamines in CH2C12 a t room temperature gave 5-(arylimino)-4-(dialkylamino)-5H-l,2,3-dithiazoles 5 in 18-76% yields. Compounds 5 are formed via (ary1imino)cyanomethyl alkylamino disulfides 3. Nucleophilic addition of the amines to the carbon atom of the cyano group of 3 and subsequent cyclization afford 5. Since a synthesis of 5-(arylimino)-4-chloro-5H-l,2,3dithiazoles 1 was reported,l much attention has been focused on these compounds because of their potential synthetic utility2 and biological importance.'J Compounds 1 are heteroaromatic compounds having nucleophilic centers at the S1, S2, C4, and C5 positions. Several reactions involving either C5 or S1 as a nucleophilic center have been rep0rted.3~ The formation of dithiazolobenzoxazine 2 from the reaction of 4-chloro-5-[(0hydroxyphenyl)iminol-5H-1,2,3-dithiazole (1) (X = 2-OH, Y = H) with NaH in THF, reported by Rees et u Z. ,~~ was the first example of the intramolecular nucleophilic displacement of the chlorine atom a t C4 by phenoxide ion. Interestingly, the intermolecular equivalent of this 1 2 cyclization was reported to be unsuccessful with sodium phenoxide and 4-chloro-5-(phenylimino)-5H-1,2,3-dithiazole (1) (X = Y = HI even under more vigorous condition^.^^ Recently4 we have demonstrated the involvement of S2 as a nucleophilic center by isolation of a variety of (ary1imino)cyanomethyl (alky1)amino disulfides 3 from the reactions of 1 with either primary or secondary alkylamines as shown in Scheme 1. Further reactions of compounds 3 with alkylamines afforded either the corresponding cyanoformamidines 4 or complex mixtures, depending on the amines used and on the substituents on the N-phenyl group. When [(pnitrophenyl)iminolcyanomethyl (pentane-l&diylamino disulfide 3 (X = p-NO,, Y = H, R2 =-CH2(CHd3CH2-) was treated with a sterically bulky amine such as tertbutylamine (9 equiv) at reflux or diethylamine (4 equiv) +Seoul National University.
Journal of The Electrochemical Society, 2012
ABSTRACT High performance negative electrode materials for lithium-ion batteries were fabricated ... more ABSTRACT High performance negative electrode materials for lithium-ion batteries were fabricated using germanium nanowire (GeNW) and graphite nanofiber (GNF) composites prepared by a low-pressure chemical vapor deposition (CVD) method. The promising high power rate anode material GeNWs were grown on the surface of a GNF bundle to mutually form the entangled structure. The high contact area between the GeNWs and GNFs enabled electrons to be efficiently transported and the GeNWs entwined with GNFs minimized the degradation of the electrochemical characteristics. These composite materials for the anode of lithium-ion batteries showed a very constant high specific capacity of similar to 1,200 mAh g(-1) with little decline of the cycling performance while the rate capability was significantly improved.
Japanese Journal of Applied Physics, 2008
1School of Electrical Engineering, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 2Resear... more 1School of Electrical Engineering, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 2Research Center for Time-domain Nano-functional Devices, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 3School of Advanced Materials Science and ...
Inorganica Chimica Acta, 2000
A novel one-dimensional coordination polymer comprising a metal ion and a host-guest complex is d... more A novel one-dimensional coordination polymer comprising a metal ion and a host-guest complex is described. Cucurbituril, a barrel-shaped molecule and potassium ion form a columnar 1D coordination polymer in the solid state, formula of which is [(C 36 H 36 N 24 O 12)K 2 (OH) 2 •(C 4 H 8 O)] n. In the coordination polymer, cucurbituril molecules stack atop one another through coordination of their carbonyl groups to the potassium ions in between. A disordered THF molecule is encapsulated in the cavity of each of the cucurbituril molecule.
Inorganic Chemistry, 1993
The chemistry of early transition metal porphyrin complexes, especially, that of the second-and t... more The chemistry of early transition metal porphyrin complexes, especially, that of the second-and third-row metal complexes has not been developed much due in part to their high oxophilicity.2 We have been interested in exploring zirconium and hafnium porphyrin complexes because they may show a rich organometallic chemistry as zirconocene derivatives d0.j The key entry to the organometallic zirconium porphyrin complexes would be Zr-(porphyrin)Clz, analogous to ZrCpzClz. The dichloridecomplex may be converted to organometallic a-complexes such as dialkyl complexes by the reactions with alkyllithium or Grignard reagents. It may also form organometallic *-complexes by replacing the two chlorides with a cyclooctatetraenyl dianion or a dicarbollide dianion. Indeed, we have succeeded in preparing Zr(por)Ch (por = OEP, TPP)4 and their organometallic derivatives Zr(TPP)-Me2 and Zr(OEP)(q5-C2B9H1~). We have presented1 the preliminary results on their syntheses and characterization by spectroscopy but have been unable togrow X-ray-quality crystals of either of the organometallic complexes until recently. When we finished the structural characterization of Zr(OEP)($-C~B~H I 1) by X-ray crystallography, however, Arnold and coworkers published5 the synthesis and characterization of Zr-(OEP)CI2 and several organometallic complexes derived from it, including Zr(OEP)(CH2SiMe3)25a and Zr(OEP)(q5-C~BsH~ I) .~~ Here we present our results on the syntheses and characterization of Zr(por)C12 (por = OEP, TPP), Zr(TPP)Mez, and Zr(0EP)-($-CzBgHI I) and the X-ray structure of Zr(TPP)Cl*(THF). Experimental Section Chemicals. All chemicals wereof reagent gradeand were used without further purification except asnoted below. Argon was purified by passage through successive columns of activated molecular sieves 13X (Aldrich) and Ridox (Fisher). ZrC14(THF)2,6 L~z (O E P) ,~ and T I~(C~B~H I were prepared by literature procedures. All solvents were distilled from their
Inorganic Chemistry, 1996
Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.... more Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.2.1) = 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8.8.5]tricosane) are effective for the catalytic hydrolysis of bis(4-nitrophenyl) phosphate. Kinetic studies reveal that the europium(III) complex (1c) catalyzes the hydrolysis to produce 6 equiv of 4-nitrophenol with a significant rate (k(1) = 1.5 x 10(-)(4) s(-)(1) at 0.40 mM) at pH 8.5 and 50 degrees C. The catalytic activity of the complexes is increased with decreasing the ionic size, i.e, La < Ce < Eu. While the use of hydrogen peroxide further increase the activity of 1b (k(1) = 1.6 x 10(-)(3) s(-)(1) at 0.40 mM), the presence of molecular oxygen does not affect the activity at all. Crystal of 1a.CH(3)OH([La(2.2.1)(Cl)(2)](Cl)(CH(3)OH)) belongs to the space group Pnma with a = 17.072(3) Å, b = 19.037(3) Å, c = 14.725(2) Å, V = 4786(1) Å(3), Z = 8, D(x)() = 1.691 g cm(-)(3), &mgr; = 21.7 cm(-)(1). The encryptated metal ion is nine-coordinated, and all the heteroatoms of the cryptate (2.2.1) ligand coordinate the metal center to form a bowl-shaped structure. Two coordinating chloride anions are located on the open face with a cis geometry. The existence of coordinated water to the europium(III) complex 1c in the aqueous solution was confirmed by time-resolved Eu(III) luminescence spectroscopy. From the decay constants in H(2)O and D(2)O, the numbers of coordinated water molecules (q) are found to be 3.02 at pH of 5.0. The above kinetic and spectroscopic observation are supportive of mechanisms in which the metal complexes act as a center for binding and activation as well as a source of nucleophilic metal hydroxides.
IEICE Transactions on Electronics, 2010
Current controlled MOS current mode logic with auto-detection of threshold voltage fluctuation T.... more Current controlled MOS current mode logic with auto-detection of threshold voltage fluctuation T. Endoh, H. J. Na (Tohoku Univ.) 16:30-16:45 1A.7 A V-band injection-locked frequency divider with low supply voltage in 0.13µm Si RFCMOS technology S. W. Seo, J. S. Rieh (Korea Univ.) 16:45-17:00 1A.8 A statistical analysis of distributions of RTS characteristics by wide-range sampling frequencies
IEEE Transactions on Nanotechnology, 2008
We report the electrical characteristics of backgated silicon nanowire (SiNW) FETs at temperature... more We report the electrical characteristics of backgated silicon nanowire (SiNW) FETs at temperatures ranging from 300 to 160 K. The voltage drop along the intrinsic part of the silicon nanowire (SiNW) was obtained by modeling the source/drain contacts as Schottky diodes. The field effect mobility values obtained from the extracted intrinsic voltage drop showed activation behaviors in the given temperature range. The activation energy was smaller than that of previously reported Ge nanowires.
Physical chemistry chemical physics : PCCP, Jan 30, 2015
In this work, an easy method to etch monolayer graphene is shown by catalytic oxidation in the pr... more In this work, an easy method to etch monolayer graphene is shown by catalytic oxidation in the presence of ZnO nanoparticles (NPs). The catalytic etching of monolayer graphene, which was transferred to the channel of field-effect transistors (FETs), was performed at low temperature by heating the FETs several times under an inert gas atmosphere (ZnO + C → Zn + CO or CO2). As the etching process proceeded, diverse etched structures in the shape of nano-channels and pits were observed under microscopic observation. To confirm the evolution of etching, current-voltage characteristics of monolayer graphene were measured after every step of etching by catalytic oxidation. As a result, the conductance of monolayer graphene decreased with the development of etched structures. This decrease in conductance was analyzed by percolation theory in a honeycomb structure. Finally, well-patterned graphene was obtained by oxidizing graphene under air in the presence of NPs, where Al was deposited on...
Journal of the Chemical Society, Chemical Communications, 1993
ABSTRACT
Journal of the Chemical Society, Chemical Communications, 1994
Solid State Sciences, 2010
P-type Si nanowire (NW)-based nano-floating gate memory (NFGM) with Au nanoparticles (NPs) embedd... more P-type Si nanowire (NW)-based nano-floating gate memory (NFGM) with Au nanoparticles (NPs) embedded in Al 2 O 3 gate layers is characterized in this study. The electrical characteristics of a representative p-type Si NW-based NFGM exhibit a counterclockwise hysteresis loop indicating the trapping and detrapping of electrons in the Au NP nodes of the NFGM device. The threshold voltage shift of the device is 5.4 V and the device has good retention over a lapse of time of 5 Â 10 4 s. On the other hand, the p-type Si NW-based top-gate device without any Au NPs does not exhibit any significant threshold voltage shift. This observation reveals that the memory behavior of the p-type Si NW-based NFGM is due to the trapping and detrapping of charge carriers in the Au NPs.
Solid-State Electronics, 2011
Electronic characteristics of silicide/silicon interface were studied in the suspended, chemicall... more Electronic characteristics of silicide/silicon interface were studied in the suspended, chemically synthesized silicon nanowires (SiNWs). Step-by-step intrusion of a silicide/Si interface along the axial direction of a suspended silicon nanowire was performed by repeated thermal annealing cycles, and the currentvoltage (I-V) characteristics of the annealed silicide/SiNW/silicide structure were measured at each cycle. The intruded length of the silicide was found to be directly proportional to the total annealing time, but the rate of silicidation was much smaller than previous works on similar silicide/SiNWs. A structural kink with Ni atoms diffused along the sidewall created a secondary source of silicidation, resulting in anomalous I-V characteristics. The measured I-V including this unintentional silicidation in the Si channel was explained by various combinations of Schottky barriers and resistors.
2011 IEEE Nanotechnology Materials and Devices Conference, 2011
ABSTRACT We present the direct measurement of the gate capacitance of a silicon nanowire field ef... more ABSTRACT We present the direct measurement of the gate capacitance of a silicon nanowire field effect transistor using time-domain monitoring of the source current when the gate pulses with various frequencies and amplitudes are applied. The displacement current induced at the gate capacitance is proportional to the derivative of the gate pulse, and it becomes measurable when the rise time of the gate pulse is small enough. The gate capacitance of fF range was successfully measured using our method.
Polyhedron, 1994
A series of new hydridocarbonyl ruthenium(I1) complexes containing chelating diphosphine ligands ... more A series of new hydridocarbonyl ruthenium(I1) complexes containing chelating diphosphine ligands of the type [RuHCl(CO)(PPh,)(L-L)] [L-L = Ph2PCH,PPh, 2, Ph2PCH2CH2PPh2 3, Ph2PCH2CH2CH2PPh2 4, cis-Ph2PCH=CHPPhz 5 and Fe(q5-C5H4PPh2)2 6] has been prepared by the reactions of [RuHCl(CO)(PPh,),] 1 with Ph2PCH,PPh2 [dppm, bis(diphenylphosphino)methane], Ph2PCH2CH2PPh2 [dppe, 1,2bis(diphenylphosphino)ethane], Ph2PCH2CH2CH2PPh2 [dppp, 1,3_bis(diphenylphosphino)propane], cis-Ph2PCH=CHPPh, [dppv, cis-1,2-bis(diphenylphosphino)ethylene] and Fe(q'-C,H$Ph,), [(dppf, l,l'-bis(diphenylphosphino)ferrocene] in boiling PhMe. The compounds 2-6 are moderately stable in solution. The new compounds were characterized by elemental analysis, IR and 'H NMR spectroscopy. Compounds l-6 have been shown to catalyse the homogeneous hydrogenation of the C=C bond of cyclohexene ; some relations between structures and catalytic activities are described. The Arrhenius activation energy of cyclohexene for compound 4 is 33.0 kJ mol-'.
Polyhedron, 1996
Interaction of neutral ruthenium(II) complexes of the type [RuHCI(CO)(PPh3) (L-L')] [where L-L'= ... more Interaction of neutral ruthenium(II) complexes of the type [RuHCI(CO)(PPh3) (L-L')] [where L-L'= Ph2PCH2CH2PPh2 (dppe), 1; Ph2PCH2CH2CH2PPh2 (dppp), 2; Ph2PCH2CH2AsPh2 (arphos), 3] with AgCIO4 in the presence of L" [L" = P(OMe)3 or PMe3] yielded the new cationic ruthenium(II) complexes [RuH(CO)(PPh3)(L")(L-L')]C104 [where L-L' = dppe, 4; dppp, 5; arphos, 6; L" = PMea, 4; P(OMe)3, 5 and 6]. All the complexes have been characterized by both analytical and spectroscopic (IR and ~H NMR) methods. The structure of a cationic complex 6, [RuH(CO)(PPh3)(P(OMe)3) (arphos)]CIO4" n-C5H12, has been confirmed by single-crystal X-ray diffraction. The Ru atom is octahedrally coordinated with CO, PPh3 and arphos in the equatorial plane and H and P(OMe)3 in the axial positions. In the hydrogenation of cyclohexene, some relations between structures and catalytic activities have been studied. The cationic complexes have shown lower catalytic activities than their neutral analogues.
Organometallics, 1992
[ (3-tert-Butylnorbomadienyl)etho~ymethylene]Fe(CO)~, the iron(0) +inylcarbene complex 2, is obta... more [ (3-tert-Butylnorbomadienyl)etho~ymethylene]Fe(CO)~, the iron(0) +inylcarbene complex 2, is obtained from the reaction of [(3,3-dimethylb~tynyl)ethoxymethylene]Fe(CO)~ (la) with cyclopentadiene a t 25 OC. Complex 2 transforms into the ~3:q1-allylacyl complex 4a via a CO insertion reaction at the original carbene carbon by heating a t 50 "C for 1 h. However, direct formation of allylacyl acyl complexes is observed in reactions of cyclopentadiene with other alkynylcarbene complexes, l b (R = SiMe,), IC (R = cyclohexyl), Id (R = n-propyl), and le (R = phenyl), at 25 "C. Considerable interest has been focused on the chemistry of transition-metal vinylcarbene complexes. They have been involved as key species in a number of noticeable reactions such as alkyne polymerization,' the Diels-Alder reaction,2 formation of bicyclic lactones via a van Halban-White type double-cyclization,3 and reactions of alkynes with metal carbene complexes,4 including the Dotz reaction. There are two types of metal vinylcarbene complexes: T$-and ~7~-types.~ However, to our knowledge, there is no previous examples of iron(0) +vinylcarbene complexes, although iron(I1) 7'-vinylcarbene complexes are known.6 Recently, we have reported the synthesis of iron(0) alkynylcarbene complexes and formation of the q3-vinylcarbene complex 3 in the reaction of the trimethylsilyl-substituted alkynylcarbene complex l b with 2,3-dimethyl-1,3-buta
Microchimica Acta, 2010
Boron-doped diamond electrodes covered with a nanostructured Pt nanoparticle-polyaniline composit... more Boron-doped diamond electrodes covered with a nanostructured Pt nanoparticle-polyaniline composite have been fabricated and employed as sensitive amperometric sensors with low detection limit. A highly conductive borondoped diamond thin film (BDD) was prepared by chemical vapor deposition, and its morphology was characterized by scanning electron microscopy and transmission electron microscopy. The nanostructured composite layer was grown on the BDD electrode by electrochemical deposition of polyaniline and Pt nanoparticles. Glucose oxidase (GOx) was then adsorptively immobilized on the modified BDD electrode. The biosensor displays a large surface area, high catalytic activity of the Pt nanoparticles, efficient electron mediation through the conducting polymer, and low background current of the electrode. The biosensor exhibits an excellent response to glucose, with a broad linear range from 5.9 μM to 0.51 mM, a sensitivity of 5.5 μA•mM −1 , a correlation coefficient (R) of 0.9947, and a detection limit of 0.10 μM. The apparent Michaelis-Menten constant (K M app) and the maximum current density of the electrode are 4.1 mM and 0.021 mA, respectively. This suggests that the immobilized GOx possesses a higher affinity for glucose at the lower K M app , and that the enzymatic reaction rate constitutes the rate-limiting step of the response.
Journal of Organometallic Chemistry, 1995
1,1,12,12-Tetramethyl[1.1]silaferrocenophane (1) and poly(ferrocenylsilane) (2) were formed as th... more 1,1,12,12-Tetramethyl[1.1]silaferrocenophane (1) and poly(ferrocenylsilane) (2) were formed as the major products in the reaction of FeCI z with the dilithium salt of (CsHs)2SiMe 2, and the X-ray crystallography for 1 revealed its molecular structure of an anti conformation.
The Journal of Organic Chemistry, 1994
The reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles 1 with excess (6 equiv) bulky dialky... more The reactions of 5-(arylimino)-4-chloro-5H-1,2,3-dithiazoles 1 with excess (6 equiv) bulky dialkylamines such as diethyl-, din -propyl-, and din -butylamines in CH2C12 a t room temperature gave 5-(arylimino)-4-(dialkylamino)-5H-l,2,3-dithiazoles 5 in 18-76% yields. Compounds 5 are formed via (ary1imino)cyanomethyl alkylamino disulfides 3. Nucleophilic addition of the amines to the carbon atom of the cyano group of 3 and subsequent cyclization afford 5. Since a synthesis of 5-(arylimino)-4-chloro-5H-l,2,3dithiazoles 1 was reported,l much attention has been focused on these compounds because of their potential synthetic utility2 and biological importance.'J Compounds 1 are heteroaromatic compounds having nucleophilic centers at the S1, S2, C4, and C5 positions. Several reactions involving either C5 or S1 as a nucleophilic center have been rep0rted.3~ The formation of dithiazolobenzoxazine 2 from the reaction of 4-chloro-5-[(0hydroxyphenyl)iminol-5H-1,2,3-dithiazole (1) (X = 2-OH, Y = H) with NaH in THF, reported by Rees et u Z. ,~~ was the first example of the intramolecular nucleophilic displacement of the chlorine atom a t C4 by phenoxide ion. Interestingly, the intermolecular equivalent of this 1 2 cyclization was reported to be unsuccessful with sodium phenoxide and 4-chloro-5-(phenylimino)-5H-1,2,3-dithiazole (1) (X = Y = HI even under more vigorous condition^.^^ Recently4 we have demonstrated the involvement of S2 as a nucleophilic center by isolation of a variety of (ary1imino)cyanomethyl (alky1)amino disulfides 3 from the reactions of 1 with either primary or secondary alkylamines as shown in Scheme 1. Further reactions of compounds 3 with alkylamines afforded either the corresponding cyanoformamidines 4 or complex mixtures, depending on the amines used and on the substituents on the N-phenyl group. When [(pnitrophenyl)iminolcyanomethyl (pentane-l&diylamino disulfide 3 (X = p-NO,, Y = H, R2 =-CH2(CHd3CH2-) was treated with a sterically bulky amine such as tertbutylamine (9 equiv) at reflux or diethylamine (4 equiv) +Seoul National University.
Journal of The Electrochemical Society, 2012
ABSTRACT High performance negative electrode materials for lithium-ion batteries were fabricated ... more ABSTRACT High performance negative electrode materials for lithium-ion batteries were fabricated using germanium nanowire (GeNW) and graphite nanofiber (GNF) composites prepared by a low-pressure chemical vapor deposition (CVD) method. The promising high power rate anode material GeNWs were grown on the surface of a GNF bundle to mutually form the entangled structure. The high contact area between the GeNWs and GNFs enabled electrons to be efficiently transported and the GeNWs entwined with GNFs minimized the degradation of the electrochemical characteristics. These composite materials for the anode of lithium-ion batteries showed a very constant high specific capacity of similar to 1,200 mAh g(-1) with little decline of the cycling performance while the rate capability was significantly improved.
Japanese Journal of Applied Physics, 2008
1School of Electrical Engineering, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 2Resear... more 1School of Electrical Engineering, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 2Research Center for Time-domain Nano-functional Devices, Korea University, Anam, Seongbuk, Seoul 136-701, Korea 3School of Advanced Materials Science and ...
Inorganica Chimica Acta, 2000
A novel one-dimensional coordination polymer comprising a metal ion and a host-guest complex is d... more A novel one-dimensional coordination polymer comprising a metal ion and a host-guest complex is described. Cucurbituril, a barrel-shaped molecule and potassium ion form a columnar 1D coordination polymer in the solid state, formula of which is [(C 36 H 36 N 24 O 12)K 2 (OH) 2 •(C 4 H 8 O)] n. In the coordination polymer, cucurbituril molecules stack atop one another through coordination of their carbonyl groups to the potassium ions in between. A disordered THF molecule is encapsulated in the cavity of each of the cucurbituril molecule.
Inorganic Chemistry, 1993
The chemistry of early transition metal porphyrin complexes, especially, that of the second-and t... more The chemistry of early transition metal porphyrin complexes, especially, that of the second-and third-row metal complexes has not been developed much due in part to their high oxophilicity.2 We have been interested in exploring zirconium and hafnium porphyrin complexes because they may show a rich organometallic chemistry as zirconocene derivatives d0.j The key entry to the organometallic zirconium porphyrin complexes would be Zr-(porphyrin)Clz, analogous to ZrCpzClz. The dichloridecomplex may be converted to organometallic a-complexes such as dialkyl complexes by the reactions with alkyllithium or Grignard reagents. It may also form organometallic *-complexes by replacing the two chlorides with a cyclooctatetraenyl dianion or a dicarbollide dianion. Indeed, we have succeeded in preparing Zr(por)Ch (por = OEP, TPP)4 and their organometallic derivatives Zr(TPP)-Me2 and Zr(OEP)(q5-C2B9H1~). We have presented1 the preliminary results on their syntheses and characterization by spectroscopy but have been unable togrow X-ray-quality crystals of either of the organometallic complexes until recently. When we finished the structural characterization of Zr(OEP)($-C~B~H I 1) by X-ray crystallography, however, Arnold and coworkers published5 the synthesis and characterization of Zr-(OEP)CI2 and several organometallic complexes derived from it, including Zr(OEP)(CH2SiMe3)25a and Zr(OEP)(q5-C~BsH~ I) .~~ Here we present our results on the syntheses and characterization of Zr(por)C12 (por = OEP, TPP), Zr(TPP)Mez, and Zr(0EP)-($-CzBgHI I) and the X-ray structure of Zr(TPP)Cl*(THF). Experimental Section Chemicals. All chemicals wereof reagent gradeand were used without further purification except asnoted below. Argon was purified by passage through successive columns of activated molecular sieves 13X (Aldrich) and Ridox (Fisher). ZrC14(THF)2,6 L~z (O E P) ,~ and T I~(C~B~H I were prepared by literature procedures. All solvents were distilled from their
Inorganic Chemistry, 1996
Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.... more Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.2.1) = 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8.8.5]tricosane) are effective for the catalytic hydrolysis of bis(4-nitrophenyl) phosphate. Kinetic studies reveal that the europium(III) complex (1c) catalyzes the hydrolysis to produce 6 equiv of 4-nitrophenol with a significant rate (k(1) = 1.5 x 10(-)(4) s(-)(1) at 0.40 mM) at pH 8.5 and 50 degrees C. The catalytic activity of the complexes is increased with decreasing the ionic size, i.e, La < Ce < Eu. While the use of hydrogen peroxide further increase the activity of 1b (k(1) = 1.6 x 10(-)(3) s(-)(1) at 0.40 mM), the presence of molecular oxygen does not affect the activity at all. Crystal of 1a.CH(3)OH([La(2.2.1)(Cl)(2)](Cl)(CH(3)OH)) belongs to the space group Pnma with a = 17.072(3) Å, b = 19.037(3) Å, c = 14.725(2) Å, V = 4786(1) Å(3), Z = 8, D(x)() = 1.691 g cm(-)(3), &mgr; = 21.7 cm(-)(1). The encryptated metal ion is nine-coordinated, and all the heteroatoms of the cryptate (2.2.1) ligand coordinate the metal center to form a bowl-shaped structure. Two coordinating chloride anions are located on the open face with a cis geometry. The existence of coordinated water to the europium(III) complex 1c in the aqueous solution was confirmed by time-resolved Eu(III) luminescence spectroscopy. From the decay constants in H(2)O and D(2)O, the numbers of coordinated water molecules (q) are found to be 3.02 at pH of 5.0. The above kinetic and spectroscopic observation are supportive of mechanisms in which the metal complexes act as a center for binding and activation as well as a source of nucleophilic metal hydroxides.
IEICE Transactions on Electronics, 2010
Current controlled MOS current mode logic with auto-detection of threshold voltage fluctuation T.... more Current controlled MOS current mode logic with auto-detection of threshold voltage fluctuation T. Endoh, H. J. Na (Tohoku Univ.) 16:30-16:45 1A.7 A V-band injection-locked frequency divider with low supply voltage in 0.13µm Si RFCMOS technology S. W. Seo, J. S. Rieh (Korea Univ.) 16:45-17:00 1A.8 A statistical analysis of distributions of RTS characteristics by wide-range sampling frequencies
IEEE Transactions on Nanotechnology, 2008
We report the electrical characteristics of backgated silicon nanowire (SiNW) FETs at temperature... more We report the electrical characteristics of backgated silicon nanowire (SiNW) FETs at temperatures ranging from 300 to 160 K. The voltage drop along the intrinsic part of the silicon nanowire (SiNW) was obtained by modeling the source/drain contacts as Schottky diodes. The field effect mobility values obtained from the extracted intrinsic voltage drop showed activation behaviors in the given temperature range. The activation energy was smaller than that of previously reported Ge nanowires.