Electrical transport properties of a single wall carbon nanotube network

Hwang, J. S.,Kim, H. T.,Kim, H. K.,Son, M. H.,Hwang, S. W.,Ahn, D. WILEY-VCH Verlag 2009 Physica Status Solidi. B Vol.246 No.4

<P>A single wall carbon nanotube (SWCNT) network is fabricated and its electronic transport properties are investigated. It shows a typical p-type field-effect-transistor (FET) behavior and nonlinearities in the source current-source bias characteristics. The network also exhibits incomplete turn-off and a small mobility. These characteristics are explained by the fact that the network is a mixture of metallic and semiconducting SWCNTs connecting with one another. Various cross junctions such as SWCNT (semiconducting)-SWCNT (semiconducting), SWCNT (semiconducting)-SWCNT (metallic) are the source of nonlinearities and the small mobility. Incomplete turn-off can be explained by the parallel conduction paths consisting of metallic SWCNTs which are insensitive to the gate bias. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Unprecedented N-Inserted Disulfide Ligand Stabilized by Coordination to the Electropositive Co^III Center

Yoo, Houng Sik,Yoon, Jung Hee,Kim, Jae Il,Koh, Eui Kwan,Hong, Chang Seop WILEY-VCH Verlag 2008 European journal of inorganic chemistry Vol.2008 No.20

<P>The reaction of Co<SUP>II</SUP> and 2,2′-dipyridyldisulfide (PySSPy) in the presence of azide produced a peculiar monomeric complex [Co<SUP>III</SUP>(PyS)(PyS-N-SPy)(N<SUB>3</SUB>)] (1). In this reaction, redox chemistry takes place, which is associated mainly with the oxidation of Co<SUP>II</SUP> to Co<SUP>III</SUP> and the reduction of PySSPy. During the reaction, the azide ion decomposes and donates a nitrogen atom to PySSPy. The crystal structure of 1 provides evidence that the unusual, N-inserted ligand PyS-N-SPy can be stabilized through coordination to the electropositive Co<SUP>III</SUP> ion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)</P> <B>Graphic Abstract</B> <P>The reaction of Co<SUP>II</SUP> and 2,2′-dipyridyldisulfide (PySSPy) in the presence of azide produced a monomeric complex [Co<SUP>III</SUP>(PyS)(PyS-N-SPy)(N<SUB>3</SUB>)] (1), which was characterized by means of UV/Vis, X-ray crystallography, XPS, and cyclic voltammetry. The unusual, N-inserted ligand PyS-N-SPy can be stabilized through coordination to the electropositive Co<SUP>III</SUP> ion. <img src='wiley_img/14341948-2008-2008-20-EJIC200800439-fig000.gif' alt='wiley_img/14341948-2008-2008-20-EJIC200800439-fig000'> </P>

QD technology and market prospects in the sectors of space exploration, biomedicine, defense, and security

Charitidis, C. A.,Golnas, A.,Chouliaras, F.,Arpatzanis, N.,Dimitriadis, C. A.,Lee, J. I.,Bakolias, C. WILEY-VCH Verlag 2008 Physica Status Solidi C Vol.5 No.12

<P>Quantum dots (QD) are a unique subset of nanomaterials characterized by their extraordinary quantum confinement behaviour. Even though the quantum dot industry is still in its infancy with revenues now reaching $10 million, it is expected to surpass $500 million in 2009. However, in order to leverage the full potential of the QD technology, new fabrication processes must be developed to attain high detectivity and high operating temperature (HOT) photodetector devices. The Quantum Dot Infrared Photodetectors (QDIPs) possess an immense potential for civilian and military applications due to the distinct characteristics stemming from their dimensionality – which provides 3D carrier confinement and the capacity for normal-incidence detection – and their amenability to bandgap engineering – which allows tailoring the peak and cutoff wavelengths according to custom needs. The QDIPs, especially when optimized to operate at higher temperatures, can become critical components in space exploration, defence and security, optical communication, quantum computing and cryptography, and medical imaging applications. Robust and reliable solutions for these fields will command a premium position in the marketplace as by responding to the societal need for secure electronic transactions, exponentially faster data processing, and higher quality diagnostic tools. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Reduction of low‐frequency noise in multilayer MoS₂ FETs using a Fermi‐level depinning layer

Kim, Yonghun,Park, Woojin,Yang, Jin Ho,Cho, Chunhum,Lee, Sang Kyung,Lee, Byoung Hun Wiley - VCH Verlag GmbH & Co. KGaA 2016 Physica Status Solidi. Rapid Research Letters Vol.10 No.8

<P>Two‐dimensional transition metal dichalcogenides (TMDCs) are potential candidate materials for future thin‐film field effect transistors (FETs). However, many aspects of this device must be optimized for practical applications. In addition, low‐frequency noise that limits the design window of electronic devices, in general, must be minimized for TMD‐based FETs. In this study, the low‐frequency noise characteristics of multilayer molybdenum disulphide (MoS<SUB>2</SUB>) FETs were investigated in detail, with two different contact structures: titanium (Ti) metal–MoS<SUB>2</SUB> channel and Ti metal–TiO<SUB>2</SUB> interlayer–MoS<SUB>2</SUB> channel. The results showed that the noise level of the device with a TiO<SUB>2</SUB> interlayer reduced by one order of magnitude compared with the device without the TiO<SUB>2</SUB> interlayer. This substantial improvement in the noise characteristics could be explained using the carrier number of fluctuation model. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)</P>

Estimating black hole masses in young radio sources using CFHT spectroscopy

Gu, M.F.,Pak, S.,Ho, L.C. WILEY-VCH Verlag 2009 Astronomische Nachrichten Vol.330 No.2

<P>The correlation between black hole masses and stellar velocity dispersions provides an efficient method to determine the masses of black holes in active galaxies. We obtained optical spectra of a Compact-Steep-Spectrum (CSS) galaxy 4C +29.70, using the Canada-France-Hawaii Telescope (CFHT) equipped with OSIS, in 2003 August 6. Several stellar absorption features, such asMg I (5175 Å), Ca E band (5269 Å) and Na D (5890 Å), were detected in the spectra. The stellar velocity dispersion, σ, of the host galaxy, measured from absorption features is ≈250 km s<SUP>–1</SUP>. If 4C +29.70 follows the M<SUB>BH</SUB>-σ relation established for nearby galaxies, then its central black hole has a mass of ≈3.3 × 10<SUP>8</SUP> M<SUB>⊙</SUB>. In combination with the black hole masses of seven GPS galaxies in Snellen et al. (2003), we find that the average black hole mass of these eight young radio sources is smaller than that of the Bettoni et al. (2003) sample of extended radio galaxies. This may indicate that young radio sources are likely at the early evolutionary stage of radio galaxies, at which the central black holes may still undergo rapid growth. However, this needs further investigations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Synthesis, Structure, Magnetic Properties and Aqueous Optical Citrate Detection of Chiral Dinuclear Cu^II Complexes

Khatua, Snehadrinarayan,Kim, Kibong,Kang, Jina,Huh, Jung Oh,Hong, Chang Seop,Churchill, David G. WILEY-VCH Verlag 2009 European journal of inorganic chemistry Vol.2009 No.22

<P>Two chiral dimeric Cu<SUP>II</SUP> Schiff base complexes, Na<SUB>2</SUB>[Cu(S-lys)<SUB>2</SUB>·(H<SUB>2</SUB>O)<SUB>2</SUB>]·(ClO<SUB>4</SUB>)<SUB>2</SUB> (1) and [Cu(S-ornH)<SUB>2</SUB>·(H<SUB>2</SUB>O)<SUB>2</SUB>]·(ClO<SUB>4</SUB>)<SUB>2</SUB> (2) have been prepared by an easy one-pot method in which the L-lysine and L-ornithine-based Schiff base ligands are generated in situ. These complexes have been characterized by various spectroscopic techniques and single-crystal X-ray diffraction. The molecular structures show that both complexes are indeed dimeric with Cu<SUP>II</SUP> centers that are phenolate-bridged. Variable-temperature magnetic analysis revealed that a strong antiferromagnetic coupling interaction was mediated through the phenolate bridge between the two Cu<SUP>II</SUP> centers. Since these compounds were highly soluble in water, we explored carboxylate sensing capability through colorimetric indicator displacement assays (IDAs). By using pyrocatechol violet (PV) as a displaceable colorimetric indicator, citrate ion selectivity was demonstrated in 100 % water solution in the physiological pH range.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)</P> <B>Graphic Abstract</B> <P>Two chiral dimeric Cu<SUP>2+</SUP> complexes 1 and 2 have been prepared by a one pot method in which the L-lysine- and L-ornithine-based Schiff base ligands are generated in situ. Variable-temperature magnetic susceptibility measurements reveal strong antiferromagnetic coupling interactions. Selective citrate ion sensing was enabled through colorimetric indicator displacement assays in water at physiological pH. <img src='wiley_img/14341948-2009-2009-22-EJIC200900357-fig000.gif' alt='wiley_img/14341948-2009-2009-22-EJIC200900357-fig000'> </P>

Change in Supramolecular Networks through In Situ Esterification of Porphyrins

Chen, Wentong,Fukuzumi, Shunichi WILEY-VCH Verlag 2009 European journal of inorganic chemistry Vol.2009 No.36

<P>A series of porphyrins, M[TCPP-Et<SUB>4</SUB>] [M = Zn (1), Cu (2), and Ni (3); Et = CH<SUB>2</SUB>CH<SUB>3</SUB>; TCPP = meso-tetra(4-carboxyphenyl)porphyrin], M[TCPP-Me<SUB>4</SUB>] [M = Zn (4), Cu (5), and Co (6); Me = CH<SUB>3</SUB>], and two nonmetalated compounds, TCPP-Et<SUB>4</SUB> (7) and TCPP-Me<SUB>4</SUB>·H<SUB>2</SUB>O (8), were synthesized by solvothermal reactions and characterized by single-crystal X-ray diffraction. Compounds 1–3 feature an isolated structure with a planar macrocycle and an embedded metal-ion coordinating to four pyrrole nitrogen atoms. Compound 4 is characterized as a two-dimensional coordination polymer, and the zinc ion coordinates to four nitrogen atoms and two oxygen atoms. Compound 4 possesses a large void space (361 Å<SUP>3</SUP>), which corresponds to 14 % of the unit-cell volume. Compounds 5 and 6 are characteristic of an isolated motif with a four-coordinate metal ion and a saddle-distorted nonplanar porphyrin macrocycle. Nonmetalated compounds 7 and 8 also show an isolated structure with a planar macrocycle. For compounds 1–3 and 7, the TCPP is esterified with ethanol, while for compounds 4–6 and 8, the TCPP is esterified with methanol. The molecules in 1 and 6–8 are interconnected by hydrogen bonds and π–π interactions to yield 3D supramolecular networks, while in 2–5, 2D supramolecular motifs are formed. The reaction mechanism was explored. Esterification plays an important role in changing the properties of the compounds as well as in the formation of different structural motifs and supramolecular networks. The UV/Vis, FTIR, fluorescence, phosphorescence, and MALDI-TOF MS spectra, quantum yields, luminescence lifetimes, and cyclic voltammograms were also studied in detail.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)</P> <B>Graphic Abstract</B> <P>Eight esterified TCPP compounds were successfully synthesized by solvothermal reactions and characterized. The reaction mechanism was investigated. Esterification plays a vital role in the properties, structural motifs and supramolecular networks. <img src='wiley_img/14341948-2009-2009-36-EJIC200900801-fig000.gif' alt='wiley_img/14341948-2009-2009-36-EJIC200900801-fig000'> </P>

Synthesis and Aqueous Colloidal Solutions of RE₂(OH)₅NO₃·nH₂O (RE = Nd and La)

Lee, Kyung-Hee,Byeon, Song-Ho WILEY-VCH Verlag 2009 European journal of inorganic chemistry Vol.2009 No.31

<P>A new, simple route leading to layered rare-earth hydroxy nitrates was developed. The pH-independent procedure uses ethanol containing alkali-metal hydroxide (KOH, RbOH, or CsOH) as a solvothermal medium. Two new, layered rare-earth hydroxy nitrates (LRHs), Nd<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O and La<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O, were prepared by this nonaqueous solvothermal reaction. Because the RE = Nd and La members have not yet been synthesized in an aqueous system, the successful synthesis of these compounds implies the completion of the RE<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O (RE = rare earths) series. The typical properties of a layered structure was demonstrated by ready ion-exchange reactions between NO<SUB>3</SUB><SUP>–</SUP> and some organic anions such as decanoate, decanesulfonate, and decyl sulfate. In particular, the as-synthesized hydroxide from solvothermal reaction, where the alkali-metal nitrates are partially intercalated in the interlayer gallery, form an aqueous colloidal solution under ultrasonic treatment. Hydration of the LRHs intercalated with alkali-metal salts results in the formation of colloidal LRH suspensions in water. The colloidal character of the LRH solutions is supported by the Tyndall effect, TEM, and AFM images.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)</P> <B>Graphic Abstract</B> <P>A new, simple route was developed to synthesize the complete rare-earth series of the RE<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O family. The hydration of La<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O and Nd<SUB>2</SUB>(OH)<SUB>5</SUB>NO<SUB>3</SUB>·nH<SUB>2</SUB>O synthesized by this nonaqueous solvothermal method yielded transparent aqueous colloidal solutions. <img src='wiley_img/14341948-2009-2009-31-EJIC200900635-fig000.gif' alt='wiley_img/14341948-2009-2009-31-EJIC200900635-fig000'> </P>

Electronic states and local structures of Cu ions in electrodeposited thin films of Cu and Cu₂O from X-ray absorption spectra

Wijesundera, R. P.,Hidaka, M.,Siripala, W.,Choi, Sun-Hee,Sung, Nark Eon,Kim, Min Gyu,Lee, Jay Min WILEY-VCH Verlag 2006 Physica status solidi. PSS. B, Basic solid state p Vol.243 No.8

<P>X-ray absorption spectra near Cu K edges have been obtained for Cu and Cu<SUB>2</SUB>O thin films potentiostatically electrodeposited in an acetate bath. The electronic states of Cu ions and the local structures around these ions are studied using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, respectively. The inner strains in micro-size crystals of the electrodeposited Cu thin film are less than those of a commercial Cu foil. The partial electronic states of Cu ions near the Fermi level (E <SUB>F</SUB>) and the local structure around these ions show a systematic transformation from a Cu<SUB>2</SUB>O single phase (Phase I), to a Cu<SUB>2</SUB>O–Cu intermediate phase (Phase II) and a Cu single phase (Phase III) in thin films electrodeposited on titanium substrates for the deposition potential range of –100 to –900 mV. Phase II consists of independent Cu<SUB>2</SUB>O-like and Cu-like local structures, but not a Cu<SUB>2</SUB>O–Cu complex. Phase II is also characterized by a transition region from the semiconductor Cu<SUB>2</SUB>O to the metal Cu for the Cu electronic state having a p-like character near the Fermi level in the oxygen O-2p conduction band. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Influence of stacking on optical characteristics of GaN/AlN self-organized quantum dots

Kwon, B. J.,Hwang, J. S.,Kwack, H. S.,Cho, Y. H.,Gogneau, N.,Daudin, B.,Dang, Le Si WILEY-VCH Verlag 2006 Physica Status Solidi C Vol.3 No.6

<P>The effect of stacking on the optical properties of self-organized GaN/AlN quantum dots (QDs) grown by plasma-assisted molecular beam epitaxy was investigated by photoluminescence (PL), PL excitation (PLE), and cathodoluminescence (CL) spectroscopic techniques. With an increase in the number of the GaN QDs stacking layer, we observed a red shift in the main QD PL peaks. A Stokes-like shift was observed between PL emission and PLE absorption edge for all the samples. From the depth-resolved CL of a 200-period GaN QD sample, we observed that the main QD CL emission peak energy position does not change much, while the higher-energy side CL peak around ∼3.7 eV shows a variation of its peak position with the accelerating voltage probably due to the change in either distribution of QD size/shape or wetting layer properties during the growth of multiple stacking of GaN QDs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>