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Substrate has great influences on materials syntheses, properties, and applications. The influences are particularly crucial for atomically thin 2-dimensional (2D) semiconductors. Their thicknesses are less than 1 nm; however, the lateral sizes can reach up to several inches or more. Therefore, these materials must be placed onto a variety of substrates before subsequent post-processing techniques for final electronic or optoelectronic devices. Recent studies reveal that substrates have been employed as ways to modulate the optical, electrical, mechanical, and chemical properties of 2D semiconductors. In this review, we summarize recent progress upon the effects of substrates on properties of 2D semiconductors, mostly focused on 2D transition metal dichalcogenides, through viewpoints of both fundamental physics and device applications. First, we discuss various effects of substrates, including interface strain, charge transfer, dielectric screening, and optical interference. Second, we show the modulation of 2D semiconductors by substrate engineering, including novel substrates (patterned substrates, 2D-material substrates, etc.) and active substrates (phase transition materials, ferroelectric materials, flexible substrates, etc.). Last, we present prospectives and challenges in this research field. This review provides a comprehensive understanding of the substrate effects, and may inspire new ideas of novel 2D devices based on substrate engineering. [ABSTRACT FROM AUTHOR]

Assume that an insurer can control it's surplus by paying dividends, purchasing reinsurance and injecting capital. The exponential premium principle is used when pricing insurance contract instead of the expected value principle. Under the objective of maximizing the company's value, we identify the optimal strategies with liquidation value and transaction costs. The results illustrate that the insurer should buy less reinsurance when the surplus increases, capital injection should be considered if and only if the transaction costs and the liquidation value are relatively low, dividends are paid according to barrier strategy if the dividend rate is unrestricted or threshold strategy if the dividend rate is bounded. [ABSTRACT FROM AUTHOR]

The assembly of a fluorescent dicarboxylate ligand with a barium ion resulted in the formation of a 3D metal-organic framework, Ba5(ADDA)5(EtOH)2(H2O)3•5DMF (UPC-17), based on a 1D rod-shaped secondary building unit. The unprecedented solvent-dependent sensitivities of UPC-17 for the detection of Fe3+/Al3+ ions and 4-nitrophenol with high efficiency were observed for the first time. Significantly, UPC-17 exhibits superior "turn-off" detection for the Fe3+ ion in methanol and acetone emulsions but shows "turn-on" detection in tetrahydrofuran emulsion. Furthermore, the visible color changes in the detection process make them easy to distinguish by the naked eye, which further increases its application potential. [ABSTRACT FROM AUTHOR]

A three-dimensional porous Zn metal-organic framework (UPC-12) with high thermal and chemical stability was isolated in high yield and purity from a hydrothermal reaction. UPC-12 exhibits high selectivity for CO2 due to the formation of hydrogen bonds between CO2 molecules and the −COOH groups exposed inside the channels and the effective π-π interactions between CO2 molecules and the pillared bipyridine moieties of the MOF. The adsorption-desorption process was studied, for the first time, by both 13C CP-TOSS NMR spectroscopy and in situ DRIFTS. [ABSTRACT FROM AUTHOR]

A new hexanuclear iron-selenium nitrosyl cluster, [(n-Bu)4N]2[Fe6Se6(NO)6] (1), and a hexanuclear iron-suttur nitrosyl cluster, [(n-Bu)4N]2[Fe6S6(NO)6] (2), were synthesized by the solvent-thermal reactions at [(n-Bu)4N][Fe-(CO)3NO] with selenium or suttur in methanol, while a tetranuclear iron-sultur nitrosyt cluster, (Me4N)[Fe4S3(NO)7] (3), was also prepared by the solvent-thermal reaction at FeCI2·4H2O with thiourea in the presence at (CH3)4NCI, NaNO2, and methanol. Complexes 1-3 were characterized by IA, UV-vis, ¹H NMR, electrochemistry, and single- crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 1694 and 1698 cm-1, respectively, white the ebsorptions at complex 3 appear at 1799, 1744, and 1710 cm-1. The UV-vis spectra at complexes 1-3 show different bands in the range at 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metat charge transfer, πNO-dFe, and the metal-to-tigand charge transfer, dFe-π*NO. Single-crystal X-ray structural analysis reveals that complex I crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel "chair-shaped" structures, consisfing of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 Å; each iron center is banded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further etectrochemical investigations demonstrated that the intensity of the unusually strong peak is a result of at leant three processes. One is the quasi-reversible reduction, and the other two are from an irreveraible electrochemical procera, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reveraible reductions. [ABSTRACT FROM AUTHOR]

Three new dinitrosyl iron complexes LFe(NO)2 (L = 2,2‱-bipyridine (bipy) (1), 2,2‱,2‱‱-terpyridine (terpy) (2) and 1,10-phenathroline (phen) (3)) were synthesized by the reaction of Fe(NO)2(CO)2 with corresponding ligands in tetrahydrofuran. Complexes 1-3 were studied using IR, UV-vis, MS, NMR, and electrochemical techniques. Complexes 1 and 2 were also characterized using single crystal X-ray diffraction analysis. IR spectra of complexes 1-3 display two strong characteristic NO stretching frequencies (vNO) in the region reflecting donor properties of the ligands. Cyclic voltammetry studies show two quasi-reversible one-electron reductions for all complexes. Electrochemical investigations using different concentrations show that an irreversible one-electron reduction at -1.85 V for complex 2 and -1.80 V for complex 3 are from solvated species. Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the triclinic P space group and the asymmetric unit consists of one Fe(NO)2(bipy) molecule with the two NO groups located on two sides of Fe(bipy) plane. Complex 2 crystallizes in monoclinic PI- space group, and the asymmetric unit contains one Fe(NO)2(terpy) molecule, in which the NO groups are located on two sides of the plane consisted of Fe and two coordinated pyridyl rings, but almost parallel to the uncoordinated pyridyl ring. The crystal packings of both complexes 1 and 2 show intermolecular H-bonding and strong π-π stacking interactions. [ABSTRACT FROM AUTHOR]

Three novel complexes of formula [Co5(OH)2(cht)2(H2O)10]n∙2nH2O (1) (H4cht = cyclohexane-1,2,4,5-tetracarboxylic acid), [Zn2(cht)(H2O)3]n∙nH2O (2), and [Cd2(cht)(H2O)5]n∙2nH2O (3) were synthesized by a hydrothermal reaction of cyclohexane-1,2,4,5-tetracarboxylic acid in the presence of sodium hydroxide wih Co(NO3)2∙6H2O, Zn(NO3)2∙6H2O, and Cd(NO3)2∙4H2O, respectively. These complexes were obtained by controlling the molar ratios of starting materials and the pH values of reaction mixtures with an initial pH of 5.87 for 1, 5.50 for 2, and 5.57 for 3, respectively. The single-crystal X-ray investigations reveal that the cht ligands change their conformations exclusively to the a,e,e,a form in all three complexes. Complex 1 features a two-dimensional (2D) metal-organic framework (MOF) with an axis surrounded by two zigzag structures, a rectangular channel surrounded by two a-carboxylate-metal-a-carboxylate and two e-carboxylate-metal-e-carboxylate chains, and two smaller distorted square-pyramidal channels surrounded by hydroxyl oxygen, cyclohexane, and its two a-carboxyaltes. Each ligand connects five cobalt atoms and each cobalt atom is six-coordinated with carboxylate-oxygen, hydroxyl, and water molecules. Complex 2 possesses a three-dimensional (3D) MOF structure that consists of the cht ligands and two types of cobalt; one is four-coordinated with carboxylate-oxygens and the other is six-coordinated with carboxylate-oxygens and water molecules. Each cht ligands is bonded to seven zinc atoms. Complex 3 is also a 2D MOF structure constructed by seven-coordinated cadmium atoms and cht ligands. the e-carboxyalates of two parallel cht ligands are connected to a type of cadmium atoms to form 1D chains, and this chains are further connected through a-carboxylates of the ligands and another type of cadmium atoms to give 2D structure. Extensive hydrogen bonding interactions involving carboxylate—oxygen atoms and crystallization water molecules afford 3D supramolecular networks in complexes 1 and 2. Magnetic susceptibility measurement of 1 confirmed a six-coordinated high-spin cobalt(II) ion and the presence of magnetic exchange coupling among the three hyrdoxyl-oxygen bridged cobalt ions. Fluorescence spectra of complexes 2 and 3 show strong fluorescent emissions in the blue region. [ABSTRACT FROM AUTHOR]

A series of Roussin''s red salt esters [Fe2(μ-RS)2(NO)4] (R = n-Pr (1), t-Bu (2), 6-methyl-2-pyridyl (3) and 4,6-dimethyl-2-pyrimidyl (4)) were synthesized by the reaction of Fe(NO)2(CO)2with thiols or thiolates. Complexes 1–4were characterized by IR, UV-vis, 1H-NMR, electrochemistry, and single-crystal X-ray diffraction analysis. The IR spectra of complexes 1–4display one weak and two strong NO stretching frequencies (νNO) in solution, but only two strong νNOin the solid. Density functional theoretical (DFT) calculations using complex 1as model suggest that two spatial isomers of these complexes bear a 3 kcal energy difference in solution. Frequency calculations of the two isomers provide insight on the origin of the vibrational bands and explain the IR observation of complexes 1–4in the solid state and in solution. Cyclic voltammetry shows two quasi-reversible, one-electron reductions for complexes 1–2and one quasi-reversible, one-electron reduction for complexes 3–4. The paramagnetic complexes [Fe2(μ-RS)2(NO)4]−(1−–4−), which are prepared by the chemical reduction of neutral complexes [Fe2(μ-RS)2(NO)4] (1–4), have also been investigated by EPR spectroscopy. Interestingly, the EPR spectra of complexes [Fe2(μ-RS)2(NO)4]−(1−–4−) exhibit an isotropic signal of g= 1.998–2.004 without hyperfine splitting in the temperature range 180–298 K. The observations are consistent with the results of the calculations, which reveal that the unpaired electron is dominantly delocalized over the two sulfur and two iron atoms. The difference of the gvalues between the reduced form of Roussin''s red ester and the typical dinitrosyl iron complexes is explained, for the first time, by the difference in unpaired electron distributions between the two types of complexes, which provides the theoretical bases for the use of gvalues as a spectroscopic tool to differentiate these biologically active complexes. [ABSTRACT FROM AUTHOR]

The Raman spectroscopic data in the range of 500–1800 cm−1 for two series of thirty homoleptic bis(phthalocyaninato) rare earth complexes M(Pc)2 and M[Pc(OC8H17)8]2 [M = Y, La–Lu except Pm; H2Pc = unsubstituted phthalocyanine, H2Pc(OC8H17)8 = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine] have been collected and comparatively studied using laser excitation sources emitting at 633 and 785 nm. Under both laser excitations, the marker Raman band of Pc2− and [Pc(OC8H17)8]2− in the Raman spectra of Ce(Pc)2 and Ce[Pc(OC8H17)8]2 appears as a strong scattering at 1498–1501 cm−1 with contributions from both pyrrole C𝄗C and aza C𝄗N stretches together with isoindole stretchings. This band has been found to upshift to 1502–1528 cm−1 in the Raman spectra of MIII(Pc)2 and MIII[Pc(OC8H17)8]2 as the marker Raman band of phthalocyanine monoanion radicals, Pc•− or [Pc(OC8H17)8]•−. With laser excitation at 633 nm, Raman vibrations derived from isoindole ring and aza stretchings in the range of 1300–1600 cm−1 for both series are selectively intensified. In contrast, when excited with laser radiation of 785 nm, the ring radial vibrations of isoindole moieties and dihedral plane deformations between 500 and 1000 cm−1 for M(Pc)2 and M[Pc(OC8H17)8]2 intensify to become the strongest scatterings. The present Raman results also reveal that the frequencies of Pc breathing, pyrrole stretching, isoindole stretchings, aza stretchings and coupling of pyrrole and aza stretchings depend on the rare earth ionic size, shifting to higher wavenumbers along with the lanthanide contraction due to the increased ring–ring interaction across the series. Moreover, under these laser excitations, in particular under 785 nm laser line, the Raman spectrum appearance, i.e., the pattern of relative intensities, also changes systematically depending on the rare earth ionic size. [Copyright &y& Elsevier]

A novel one-pot procedure starting from the corresponding M(acac)3·nH2O, metal-free phthalocyanine H2Pc', and naphthalonitrile in the presence of DBU in n-octanol has been developed to prepare heteroleptic (naphthalocyaninato)(phthalocyaninato) rare earth double-decker complexes. A series of six sandwich compounds with different naphthalocyaninato ligands, phthalocyaninato ligands, and central rare earth metals, namely, Sm[Nc(tBu)4](Pc) [Nc(tBu)4 = 3(4),12(13),21(22),30(31)-tetra(tert-butyl)naphthalocyaninato; Pc = unsubstituted phthalocyaninato] (1), Sm(Nc)(Pc') [Pc' = Pc(OC5H11)4, Pc(OC8H17)8; Nc = 2,3-naphthalocyaninato; Pc(OC5H11)4= 2(3),9(10),16(17),24(25)-tetrakis(3-pentyloxy)phthalocyaninato; Pc(OC8H17)8 = 2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyaninato] (2, 3), and M(Nc)[Pc(α-OC5H11)4 ][M = Sm, Eu, Y; Pc((α-OO5H11)11 -= 1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato] (4-6), have been isolated in good yields from this one-pot procedure demonstrating the generality of this synthetic pathway. In addition to spectroscopic analyses, the electrochemistry of these novel compounds has also been studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. [ABSTRACT FROM AUTHOR]

A pair of framework-catenation isomers (UPC-19 and UPC-20) based on an anthracene-functionality dicarboxylate ligand were synthesized and characterized for the first time through tuning of the dimensionality of interpenetration. The interpenetration dimensionality significantly influences the properties including the porosity, gas-uptake capacity, and fluorescent sensing ability: UPC-19 with 5-fold interpenetration is nonporous, whereas the 3-fold interpenetration form of UPC-20 is porous and exhibits selective adsorption of CO2 and fluorescent sensing of Cu2+ and Fe3+ through fluorescence quenching. [ABSTRACT FROM AUTHOR]

A new porous zirconium metal--organic frame work (Zr MOF), Zr6 (μ3 - 0)4(/irOH)4(OH)6(H2O)6(BTB)2.6DMFH6O (1; H3BTB = 5'- (4-carboxyphenyl) [1,1' :3' 1"-terphenyl] -4,4"-dicarboxylic acid), based on Zr6 clusters and tricarboxylate ligands has been constructed and characterized. The Zr6 dusters were linked by BTB ligands to generate a 2D network of kgd topology. The interpénétrations among the 2D networks gave rise to a 3D porous framework, which represents the first Zr MOF constructed from 2D → 3D interpénétration. The gas uptake and catalytic properties for 1 have also been studied. [ABSTRACT FROM AUTHOR]

Ultrathin ZnS nanobelts were assembled by ultrasmall nanocrystals with oriented self assembly, which were then transformed into their single-crystal counterparts by thermal treatment in N2. ZnO/ZnS heterostructures were also obtained at elevated temperature in open air, where well aligned ZnO nanocones were grown along the ZnS nanobelts with a definite orientation relationship described as [0001]ZnS∥[0001]ZnO and (1010)ZnS∥(1010)ZnO. Mixed transition and tuned band gaps of the heterostructure were experimentally observed, which was in good agreement with the theoretical predications and can be interpreted based on the model of a strained staggered type-II band structure. [ABSTRACT FROM AUTHOR]

Catalysis by supported single metal atoms has demonstrated tremendous potential for practical applications due to their unique catalytic properties. Unless they are strongly anchored to the support surfaces, supported single atoms, however, are thermodynamically unstable, which poses a major obstacle for broad applications of single-atom catalysts (SACs). In order to develop strategies to improve the stability of SACs, we need to understand the intrinsic nature of the sintering processes of supported single metal atoms, especially under various gas environments that are relevant to important catalytic reactions. We report on the synthesis of high number density Pt1/Fe2O3 SACs using a facial strong adsorption method and the study of the mobility of these supported Pt single atoms at 250 °C under various gas environments that are relevant to CO oxidation, water–gas shift, and hydrogenation reactions. Under the oxidative gas environment, Fe2O3 supported Pt single atoms are stable even at high temperatures. The presence of either CO or H2 molecules in the gas environment, however, facilitates the movement of the Pt atoms. The strong interaction between CO and Pt weakens the binding between the Pt atoms and the support, facilitating the movement of the Pt single atoms. The dissociation of H2 molecules on the Pt atoms and their subsequent interaction with the oxygen species of the support surfaces dislodge the surface oxygen anchored Pt atoms, resulting in the formation of Pt clusters. The addition of H2O molecules to the CO or H2 significantly accelerates the sintering of the Fe2O3 supported Pt single atoms. An anchoring-site determined sintering mechanism is further proposed, which is related to the metal–support interaction. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy (TERS), a combination of Raman spectroscopy and apertureless near-field scanning optical microscopy using a metallic tip which resonates with the local mode of the surface plasmon, can provide a high-sensitive and high-spatial-resolution optical analytical approach. The basic principle of TERS, common experimental setups, various SPM technologies, and excitation/collection configurations are introduced as well as recent research progress with respect to TERS. [ABSTRACT FROM AUTHOR]

The article presents a study which revealed the effects of the state and structure of catalysts on the growth modes of single-walled carbon nanotubes (SWCNTs). Topics discussed include diameter correlation between SWCNTs and catalyst nanoparticles through ex situ transmission electron microscope (TEM), in situ ETEM characterization of SWCNTs grown from solid and molten cobalt (Co) catalysts, and comparison of chiral angle distributions of SWCNTs grown on different catalysts.

An open terbium-organic framework(UPC-11) based ona rigid tetracarboxylate ligand was successfully assembled, whichexhibits excellent solvent-dependent photoluminescence (PL). Moreover, UPC-11displays rapid and selective sensing of nitroaromaticcompounds (NACs), especially for 4-nitrophenol (4-NP), which representsthe first Tb MOF that can be used as fluorescence detection of 4-NP. [ABSTRACT FROM AUTHOR]

Two 2-fold interpenetrating metal-organic frameworks based on 1,3,5-tris[2-(4-carboxyphenyl)-1-ethynyl]-2,4,6-trimethylbenzene(H3LMe), [Mn3(LMe)2(DMF)4(H2O)]∙1.5DMF∙3.5H2O (1) and [Cd3(LMe)2(DMF)][Cd3(LMe)2(DMF)2(H2O)]∙5DMF∙3.5H2O (2), have been synthesized by using rigid trigonal H3LMe and nitrate under solvothermal conditions. Complex 1 displays a three-dimensional open framework with rare (3,6)-connected 2-nodal sit topology, whereas complex 2 features a new (3,3,6)-connected topology. Both 1 and 2 are blue fluorescent, and the magnetic measurement of 1 indicates that metal centers within the trinuclear cluster exhibit antiferromagnetic coupling interactions. Significantly, although complexes 1 and 2 have similar total solvent-accessible volumes, 2 demonstrates a higher Brunauer-Emmett-Teller surface area than that of 1, further indicating the influence of pore structure on gas absorption. [ABSTRACT FROM AUTHOR]

Five coordination polymers based on 5,5'-(2,3,6,7-tetramethoxyanthracene-9,10-diyl)diisophthalic acid (H4LOMe): [Mn4(LOMe)(OAc)2(μ3-OH)2(NMP)4(H2O)2].2H2O (1), [Ni2(LOMe)0.5(H2LOMe)0.5(μ3-OH)(H2O)3].6H2O (2), [Cd2(LOMe)(H2O)2(NMP)].2DMF.NMP.H2O (3), [Co2(LOMe)(H2O)2].2NMP.DMA.2H2O (4), [Zn2(LOMe)(H2O)2].2NMP.2H2O.DOE (5) (NMP = N-methylpyrrolidone, DMF = N,N'-dimethylformamide, DMA = N,N'-dimethylacetamide, DOE = 1,4-dioxane) were prepared by solvothermal methods and characterized by elemental analysis (EA), single-crystal X-ray crystallography, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), and thermogravimetric analyses (TGA). X-ray crystallography analysis shows that complex 1 bears a two-dimensional (2D) (4,4) network based on tetranuclear secondary building units, which are further assembled into a three-dimensional supramolecular structure via π...π stacking interaction; complex 2 displays a 3D framework with fsc topology based on 2D 44-sql layers and tetranuclear SBUs; complex 3 reveals a 3D PtS network via the LOMe bridging dimetal {Cd2O11} units; complexes 4 and 5 possess 3D open frameworks with a rarely reported 3-nodal (4,4,4)-connected nou network. Moreover, magnetic susceptibility measurement of complexes 1 and 2 confirm the presence of magnetic exchange coupling among the metal ions of tetranuclear clusters, and fluorescent spectra of complexes 1, 3 and 5 show emission signals in the blue region. [ABSTRACT FROM AUTHOR]

Enantioselective Michael addition of 1,3-diketones to alkylideneindolenines generated in situ from arenesulfonylalkylindoles is described, and a series of optically active C3-alkylsubstituted indole derivatives has been obtained. The resulting adducts can be readily converted into 3-sec-alkyl-substituted indoles containing a pyrazole skeleton, with direct connection between the a- and 4-positions, without decrease of the enantioselectivity. [ABSTRACT FROM AUTHOR]

In this article, we consider the optimal reinsurance and dividend strategy for an insurer. We model the surplus process of the insurer by the classical compound Poisson risk model modulated by an observable continuous-time Markov chain. The object of the insurer is to select the reinsurance and dividend strategy that maximizes the expected total discounted dividend payments until ruin. We give the definition of viscosity solution in the presence of regime switching. The optimal value function is characterized as the unique viscosity solution of the associated Hamilton-Jacobi-Bellman equation and a verification theorem is also obtained. [ABSTRACT FROM AUTHOR]

A series of four amphiphilic heteroleptic tris(phthalocyaninato) europium complexes with different lengths of hydrophobic alkoxy substituents on one outer phthalocyanine ligand Pc(15C5)4EuPc(15C5)4EuPc(OCnH2n1)8(n4, 6, 10,12) (1, 2, 4, and 5) was designed and prepared. Their film forming and organic field effect transistor properties have been systematically studied in comparison with analogous Pc(15C5)4EuPc(15C5)4EuPc(OC8H17)8(3). Experimental results showed that all these typical amphiphilic sandwich triple-decker molecules have been fabricated into highly ordered films by the Langmuir−Blodgett (LB) technique, which displays carrier mobility in the direction parallel to the aromatic phthalocyanine rings in the range of 0.0032−0.60 cm2V-1s-1depending on the length of the hydrophobic alkoxy substituents. This is rationalized on the basis of comparative morphology analysis results of the LB films by the atomic force microscopy technique. [ABSTRACT FROM AUTHOR]

The article presents a study which explores about the single-molecule field effect and conductance switching driven by electric field and proton transfer. It mentions that single-molecule junctions (SMJs) offer a novel strategy for miniaturization of electronic devices, along with deciphering the intrinsic properties of matters at the molecular scale.

High-density ZnO nanowires (ZnONWs) were aligned onto Au-catalyzed Si substrate through a simple low-temperature physical vapor deposition method. Scanning electron microscope (SEM) observations, x-ray diffraction (XRD) analysis, and photoluminescence spectra showed that the ZnONWs were single-crystalline, with a hexagonal wurzite structure. All of the results inferred from the SEM observations, the XRD rocking curves, and the Raman spectra for the investigated samples confirm that the ZnONWs are well aligned and c-axis oriented. The Raman spectra also indicated that the ZnONWs on Si substrates are under the biaxial compressive stress. Since it takes the advantage of low-cost, easily controlled deposition spot (due to the selective deposition trait of the Au layer), potential for scale-up production, and ability to integrate with Si substrate, this technique has a potential in future for fabricating the ZnONW array-based optoelectronic devices. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The (Au,Ag)/Nb-1.0 wt %-doped SrTiO3 (NSTO), i.e., Au/NSTO, Ag/NSTO, Ag/Au/NSTO, and Au/Ag/NSTO junctions were fabricated by magnetic controlled sputtering and annealing process. Backward diodelike behaviors were observed in all as-prepared samples, and forward rectifying characteristics were gradually developed in the four junctions after annealed in oxygen at 400 °C, 550 °C, 700 °C, and 850 °C, respectively. Compared with the Ag/NSTO junctions, the Au/NSTO junctions showed higher temperature evolving procedure of forward rectifying behavior. Moreover, ideal Schottky behaviors appeared in the samples annealed at 850 °C, which were attributed to the formation of interface states. X-ray photoelectron spectroscopy and secondary ion mass spectrometry analysis showed that the interface states mainly originated from the migration of metal into NSTO matrix and the changes in chemical composition at the metal/NSTO interfaces. The results of current-voltage measurements reveal that annealing at higher temperature alters the interface barrier and thereby ameliorates the stability of leakage current remarkably. [ABSTRACT FROM AUTHOR]

Au/TbMnO3(TMO)/YBa2Cu3O7-x(YBCO) capacitors were fabricated on LaAlO3 (LAO) and SrTiO3 (STO) substrates under identical conditions. Dielectric properties were measured in the temperature range from 20 to 350 K. High dielectric constants and single dielectric transition peaks were found in both TMO films. The dielectric constants of TMO film on STO substrate were larger than those of TMO film on LAO substrate; correspondingly, the transition temperature of TMO film on STO substrate was higher than that of TMO film on LAO substrate. Although x-ray diffraction showed both TMO films had the same epitaxial orientation, atom force microscopy revealed that the films had different surface morphologies, which originated from the YBCO layers on different substrates. The good surface morphology of YBCO layer and the element diffusion between TMO and YBCO layers may be suggested to be responsible for the significant improvement in the dielectric properties of TMO thin film. [ABSTRACT FROM AUTHOR]

The electroresistance (ER) of La0.36Pr0.265Ca0.375MnO3 (LPCMO) epitaxial thin film was studied under various dc currents. The current effect was compared for the unpatterned film and patterned microbridge with a width of 50 µm. The value of ER in the unpatterned LPCMO film could reach 0.54 under a 1-mA current, which is much higher than ER under 1 mA for the patterned weak phase-separated La0.67Ca0.33MnO3 and La0.85Sr0.15MnO3 microbridges with 50-µm width. More interestingly, for the patterned LPCMO microbridge, the maximum of ER can reach 0.6 under a small current of 100 µA. The results were explained by considering the coexistence of ferromagnetic metallic phase with the charge-ordered phase, and the variation of the phase separation with electric current. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined the tuning interactions between ligands in double-decker (DD) molecules, where parallel porphyrin or phthalocyanine rings are connected by rare earth cations. The study examined how additional three dimensional (3D) complexities affect the self-assembly of 3D structures. The increase in the size of the top ligand in DD molecules resulted to the expansion of the lattice in the adlayer.

In the past few years, tubular nanostructures have aroused considerable interest due to their exceptional properties and potential applications in catalysis, composite materials, and optoelectronics. The discovery of carbon nanotubes in 1991 has sprawled the belief that other layered materials may also roll up into tubes just as the graphite sheets do. This is reasonable because the layered structures tend to bend to eliminate dangling bonds by the intralayer linkage. Here, the article demonstrates a simple solution-phase approach for the synthesis of novel nanotubes of a nickel complex.

The Blocking temperature (TB) of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT) to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (Heb) was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of TB in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance TB and Heb. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200) texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices. [ABSTRACT FROM AUTHOR]

We report on the structural evolution and atomic inter-diffusion characteristics of the bimetallic Ni-Au nanocrystals (NCs) by molecular dynamics simulations studies. Our results reveal that the thermal stability dynamics of Ni-Au NCs strongly depends on the atomic configurations. By engineering the structural construction with Ni:Au = 1:1 atomic composition, compared with core-shell Au@Ni and alloy NCs, the melting point of core-shell Ni@Au NCs is significantly enhanced up to 1215 K. Unexpectedly, with atomic ratio of Au:Ni= 1:9, the melting process initiates from the atoms in the shell of Ni@Au and alloy NCs, while starts from the core of Au@Ni NCs. The corresponding features and evolution process of structural motifs, mixing and segregation are illustrated via a series of dynamic simulations videos. Moreover, our results revealed that the face centered cubic phase Au0.75Ni0.25 favorably stabilizes in NCs form but does not exist in the bulk counterpart, which elucidates the anomalies of previously reported experimental results on such bimetallic NCs. [ABSTRACT FROM AUTHOR]

Strong nonlinear resistance has been found in the charge ordered ferroelectric iron oxyborate (Fe2OBO3) with a high dielectric constant and giant converse magne-toelectric effect. In low temperature range the I-V nonlinearity increases quickly with decreasing temperature. Transport measurements on polycrystalline and single crystal Fe2OBO3 indicate that the nonlinearity is not induced by grain boundaries. The nonlinear I-V behavior is intrinsically correlated with the charge order phase melting in Fe2OBO3 by detailed in-situ TEM investigations. These results provide an insight into structure-activity relationship of resistance switching effects at atomic and electric scales, which is essential for its potential application as varistors and storage media [ABSTRACT FROM AUTHOR]

Zinc paddlewheel metal-organic frameworks (MOFs) frequently exhibit low stability or complete collapse upon the removal of axial ligands. Hence, there are very few reports on gas adsorption of zinc paddlewheel MOFs. In this work, the N2 and H2 adsorption measurements were carried out for a zinc MOF (namely, SDU-1) based on two types of paddlewheel secondary building units (SBUs): [Zn2(COO)3] and [Zn2(COO)4]. Because of the existence of inherent surface instability upon removal of solvates in zinc paddlewheel SBU, SDU-1 possesses a very low surface area. Through metal-ion metathesis in a single-crystal-to-single-crystal fashion, the Zn2+ ions in SDU-1 were exchanged by Cu2+ ions to generate Cu-SDU-1. Through the measurements of gas adsorption and catalytic test, the porosity and catalytic capacity of Cu-SDU-1 have been improved significantly, compared to SDU-1. [ABSTRACT FROM AUTHOR]

We report on ordered nanoporous films exhibiting a unique magneto-plasmon based response, fabricated by nanosphere-assisted physical deposition. This work focuses on multi-layer Ag/CoFeB/Ag films as examples of such structures. Their microstructure dependent magnetic properties, localized surface plasmon resonance (LSPR) and magneto-optical Kerr effect were investigated. The observed effects of nanopores and Ag layers on the magnetic properties indicate the synergistic interaction between nanopores and Ag layers leading to an enhancement of the ferromagnetic character of the CoFeB film. LSPR spectra reveal that the introduction of Ag layers enhances the light transmission in the nanoporous CoFeB films (having pore sizes exceeding the wavelength of light) due to an enhanced interaction of light with surface plasmons. Periodic nanoporous Ag/CoFeB/Ag films covered by Ag capped nanospheres show a much larger extinction than uncovered nanoporous Ag/CoFeB/Ag films. The correlation between the magneto-optical Kerr effect and the nanostructures suggests a field-tunable Kerr effect owing to the magneto-electric coupling between the magnetic layer and the Ag layers, which is enhanced by the nanopores. These hybrid nanostructures are expected to offer potential applications in photovoltaic cells and for magneto-optic sensors. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) is a thermodynamically stable crystallographic phase of iron oxide and has attractive applications in many areas. By using a simple hydrothermal method, we synthesized smooth hematite microcubes and porous hematite microcubes. The as-synthesized microcubes have uniform edge lengths of about 1 μm. The magnetic, electrochemical properties and gas sensing performance to some organic gases were investigated, revealing the potential applications in various fields. By tuning the experimental parameters, such as source and solvent, we are able to tunably produce goethite (FeOOH) nanowires, and hematite nanoparticles, nanorods, and nanoplatelets and the formation mechanism was also discussed. [ABSTRACT FROM AUTHOR]

One-dimensional Ni/Ni 3C core–shell nanoball chains with an average diameter by around 30 nm were synthesized by means of a mild chemical solution method using a soft template of trioctylphosphine oxide (TOPO). It was revealed that the uniform Ni nanochains were capped with Ni 3C thin shells by about 1−4 nm in thickness and each Ni core consists of polygrains. The coercivity of the core–shell nanochains is much enhanced (600 Oe at 5 K) and comparable with single Ni nanowires due to the one-dimensional shape anisotropy. Deriving from the distinctive structure of Ni core and Ni 3C shell, this architecture may possess a possible bifunctionality. This unique architecture is also useful for the study on the magnetization reversal mechanism of one-dimensional magnetic nanostructure. [ABSTRACT FROM AUTHOR]

A new type of 3D "strongly" self-catenated metal--organic framework (SDU-9) has been constructed from [Cu2(COO)4] paddlewheel secondary building units and a tripodal carboxylate linker. SDU-9 ([Cu6(H2O)6L4]-24H2O, where [H3L = 4,4',4"-(hydroxysilanetriyl)tris-(triphenyl-4-carboxylic acid), represents a rare example of a highly symmetrical coordination network and extremely tight self-catenation. To the best of our knowledge, SDU-9 has the highest topological density among all known 3,4-coordinated nets. [ABSTRACT FROM AUTHOR]

Pt-based one-dimensional hollow nanostructures are promising catalysts in fuel cells with excellent activity. Herein, one-dimensional hollow FePt nanochains were shown to be efficient nanocatalysts in the hydrolysis of NaBH4. The characterization of composition, structure and morphology identifies an ultrathin shell (∼3 nm) with uniformly distributed Fe30Pt70 constituents. The H2 generation rate of hollow Fe30Pt70 nanochains achieves 16.9 l/(min · g) at room temperature, while the activation energy is as low as 17.6 kJ mol−1 based on the fitting over the whole reaction time span. After the catalysis of NaBH4 hydrolysis, the morphology and composition of hollow FePt nanochains remain unchanged. Furthermore, the structural stability of hollow FePt nanochains under Ga+ ion irradiation is clarified. Theoretical simulation indicates that the stopping range of such a Fe30Pt70 shell is 7.7 keV, which offers a prediction that structure evolves diversely under Ga+ ions below and above such energy. The Ga+ ion irradiation experiments show a consistent trend with the simulation, where Ga+ ions with kinetic energy of 30 keV make the hollow architecture subside and sputter away, while Ga+ ions with kinetic energy of 5 keV only etch the top and lead to an eggshell structure. [ABSTRACT FROM AUTHOR]

We demonstrate the synthesis of single-crystalline star-shaped ZnO microcrystals with six arms by a simple solution method. Microscopic and diffraction data reveal that the as-grown products have a wurtzite structure. Each arm of the ZnO microstars has a sharp tip of several nanometers. Under moderate optical excitation, stimulated emission was observed at 388.4 nm with a full width at half-maximum (FWHM) of less than 3 nm and a threshold of 318 kW/cm2. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) sheets were synthesized via a modified Hummers method. GO dispersion with a high concentration of 6 mg ml−1 was chosen to form GO hydrogel, followed by chemical reduction to derive a free–standing reduced GO (rGO) film. According to the x-ray diffraction (XRD) analysis, it has a [0 0 1] crystalline orientation in the film thickness direction. The rGO film has a densely stacked laminated structure and highly anisotropic characteristic of electrical conductivities. The light-weight rGO wire also demonstrates its excellent flexible and fire-retardant characteristics. Stress–strain measurements revealed the mechanical properties of the GO film can got further improved after chemical reduction. Electrical transport measurement indicates that rGO film exhibit semiconducting behavior with negative temperature coefficient characteristic. A temperature dependence of the conductivity from 20 to 297 K reveals that the carrier transport mechanism is thermally activated band conduction above 200 K and three-dimensional (3D) Mott’s variable range hopping below 100 K. The parameters such as a density of the localized electron states and a localization length of the wave function have been determined from the plot of conductivity versus (versus) temperature. [ABSTRACT FROM AUTHOR]

Uniform and aligned nickel nanochains with interlaced-nanodiscs structure were first synthesized by using a template-free magnetic-field-assisted method at room temperature. The interlaced-disc nanochains were composed of nanodiscs with diameters of [?]90 nm and thicknesses of [?]10 nm. An attachment process has been proposed to explain the observed growth of the nanodiscs. With concentration of the OH[?] increased, the morphology of the products transforms from star- to interlaced-nanodisc-like nanochains. Systematic magnetic measurements demonstrate that the well-aligned interlaced-nanodisc-like Ni nanochains have coercivity of about 300 Oe and effective anisotropy of about five times more than the bulk value. [ABSTRACT FROM AUTHOR]