Array Of Chains Research Articles

Nanoscale phase separation of a binary molecular system of copper phthalocyanine and di-indenoperylene on Ag(111)

Alternating copper phthalocyanine (CuPc) and di-indenoperylene (DIP) molecular chain arrays have been fabricated via nanoscale phase separation of this CuPc:DIP binary molecular system on Ag(111). In situ low-temperature scanning tunneling microscopy has been used to investigate the molecular self-assembling processes on surface and the structural property of the well-ordered nanostructure arrays. The results show that the formation of these supramolecular structures is governed by the noncovalent molecule-molecule interactions.

Magnetism and Structure in Chains of Copper Dinuclear Paddlewheel Units

An anhydrous copper carboxylate compound of formula [Cu(trans-2-butenoate)(2)](n) has been characterized. X-ray analysis reveals a structure built by paddlewheel units bridged by pairs of Cu...O axial bonds to give infinite chains arranged in a new topological motif. Susceptibility measurements in the 10-300 K temperature range, and isothermal magnetization curves at 2, 5, 10, and 50 K with fields up to 5 T, were obtained. Electron Paramagnetic Resonance (EPR) spectra of powder samples were measured at 33.9 GHz at 300 K, and at 9.60 GHz at temperatures in the range 90 <or= T <or= 350 K. Fitting the susceptibility data to a chain model of alternating paddlewheel and [Cu(mu-O)(2)Cu] dinuclear units yielded exchange interactions J(1) = -330.6(1) cm(-1) and J(2) = 5.9(2) cm(-1). The EPR spectra reflect the usual antiferromagnetic dinuclear behavior, with zero field splitting parameters of the excited spin triplet, D = -0.329(3) cm(-1) and E approximately 0, plus a central peak not expected for isolated dinuclear units. We interpret this peak as arising from the stochastic spin dynamics of the chain introduced by exchange couplings between spins in neighbor dinuclear units, which averages out the zero field splitting. Interactions of the units with the rest of the chain acting as a spin bath give rise to a quantum transition between localized dinuclear states and states of the spin chain. This effect competes with the condensation of the antiferromagnetic dinuclear units into the singlet ground state, producing a characteristic temperature dependence of the shape of the powder EPR spectra. We interpret these features in terms of basic theories of magnetic resonance in coupled spin systems applied to the chain array of dinuclear units.

Magnetic ordering in arrays of one-dimensional nanoparticle chains

The magnetic order in parallel-aligned one-dimensional (1D) chains of magnetic nanoparticles is studied using a Monte Carlo technique. If the easy anisotropy axes are collinear along the chains a macroscopic mean-field approach indicates antiferromagnetic (AFM) order even when no interparticle interactions are taken into account, which evidences that a mean-field treatment is inadequate for the study of the magnetic order in these highly anisotropic systems. From the direct microscopic analysis of the evolution of the magnetic moments, we observe spontaneous intra-chain ferromagnetic (FM)-type and inter-chain AFM-type ordering at low temperatures (although not completely regular) for the easy-axes collinear case, whereas a random distribution of the anisotropy axes leads to a sort of intra-chain AFM arrangement with no inter-chain regular order. When the magnetic anisotropy is neglected a perfectly regular intra-chain FM-like order is attained. Therefore it is shown that the magnetic anisotropy, and particularly the spatial distribution of the easy axes, is a key parameter governing the magnetic ordering type of 1D-nanoparticle chains.

Metal nanoparticle chains embedded in TiO 2 nanotubes prepared by one-step electrodeposition

Arrays of Ni nanoparticle chains embedded in TiO 2 nanotubes (TiO 2/Ni) were fabricated by one-step electrodeposition in anodic aluminum oxide membranes. The formation of spacing Ni nanoparticles or continuous nanorods in the TiO 2 nanotubes depends on the deposition potential, the potential waveform, and the pH value in the electrolyte. The growth mechanism is attributed to the generation of H 2 bubbles and their periodical evolution outside of the TiO 2 nanotubes.

Structural modulation of Cd(II) supramolecular frameworks with a versatile 2,4-dipyridyl-type building block and different dicarboxylate ligands

A series of Cd(II) coordination complexes with an elongated 2,4-dipyridyl-type building block trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (bpe) and different dicarboxylate ligands have been presented. Generally, bpe shows the unidentate coordination mode and serves as the terminal pendant, whereas the dicarboxylate ligands display various binding fashions to interlink the metal centers to form 1-D comb-like chain, ribbon, and fishbone arrays, as well as 2-D 44 and 4.82 layered networks. Notably, the bpe building block is also involved in secondary interactions such as hydrogen bonding and aromatic stacking to construct the resulting supramolecular architectures. Thermal stability of these complexes has been studied by TG-DTA technique.

Thermosensitive Spherical Organosilicate Hybrid Particles with a Multilayered Structure

Abstract A simple one-pot synthesis of thermosensitive spherical organosilicate hybrid particles is described. These organosilicate hybrid particles exhibit solid–liquid transition behaviors whose temperature can be changed by the modification of interdigitated arrays of long alkyl chains.

Synthesis, Spectroscopic Characterization and Crystal Structure of a New Acetyl phosphorylamidate P(O)[NHC(O)C6H4(4-NO2)][N(CH(CH3)2)(CH2C6H5)

A new acetyl phosphorylamidate P(O)[NHC(O)C6H4(4-NO2)][N(CH(CH3)2)(CH2C6H5)]2 has been synthesized and characterized by elemental analysis, 1H, 13C and 31P NMR, IR and single crystal X-ray diffraction. Single crystal X-ray analysis shows that it belongs to triclinic system, space group $$ P\bar{1} $$ , with a = 10.5868(16) A, b = 11.8058(18) A, c = 12.4364(19) A, α = 65.410(3)°, β = 67.492(4)°, γ = 85.879(3)°, V = 1,298.6(3) A3, and Z = 2. The intermolecular PO···HN hydrogen bond makes H-bonded dimer of molecule with Ci symmetry. In the crystal network, the dimers are aggregated in the chain arrays through π-stacking between p-NO2–C6H4–C(O)–NH– moieties. Moreover, weak C–H···O and C–H···π interactions exist in the crystal network. In the crystal network of P(O)[NHC(O)C6H4(4-NO2)][N(CH(CH3)2)(CH2C6H5)]2, the H-bonded dimers with Ci symmetry are aggregated in the chain arrays through π-stacking between p-NO2–C6H4–C(O)–NH– moieties.

Spin-Crossover Behavior in Cyanide-Bridged Iron(II)−Copper(I) Bimetallic 1−3D Metal−Organic Frameworks

The synthesis and characterization of a series of 1-3D cyanide-bridged iron(II)-copper(I) bimetallic coordination polymers formulated as {Fe(3-Xpy)(2)[Cu(3-Xpy)(z)(CN)(2)](2)}, where 3-Xpy is a 3-halogenpyridine ligand with X = F (z = 1.5, 1), Cl (z = 1, 2 and 3), Br (z = 1, 4), and I (z = 1, 5), are reported. In all derivatives, the Fe(II) ion lies in pseudoctahedral [FeN(6)] sites defined by four in situ formed [Cu(3-Xpy)(z)(CN)(2)](-) bridging ligands and two 3-Xpy terminal ligands occupying the equatorial and axial positions, respectively. 1 consists of stacks of corrugated grids whose square windows are defined by pseudotrigonal and pseudotetrahedral [Cu(3-Fpy)(CN)(2)](-) and [Cu(3-Fpy)(2)(CN)(2)](-) units, respectively. 2 is a 3D coordination polymer with the topology of the open-framework CdSO(4). The [Cu(3-Clpy)(CN)(2)](-) rods connecting the pseudooctahedral Fe(II) sites are arranged in such a way that interpenetration is avoided. 3, an architectural isomer of 2, is defined by arrays of linear chains. 4 and 5 are isostructural to 3. Polymer 1 is essentially a low-spin (LS) compound with ca. 19% of residual Fe(II) ions in the high-spin (HS) state at 293 K. It undergoes an irreversible spin transition at T(c) = 356 K. Subsequent cooling-warming cycles give a new spin-crossover behavior characterized by T(c) = 187 K. The structural analysis at 130 and 293 K and at 293 K after irreversible transformation (293 K*) reveals a large unit cell volume variation of 67 A(3) per Fe atom. In addition to the volume change associated with the spin-state conversion, remarkable bond and angle modifications around the Cu(I) sites account for the high flexible nature of the crystal. 2 displays a complete not well-resolved two-step spin conversion, T(c1) = 169 K and T(c2) = 210 K, reflecting the occurrence of two distinct crystallographically Fe(II) sites. The large unit cell volume variation per Fe atom in 2, 59 A(3), has been rationalized in terms similar to those for 1. 1D polymers 3-5 are HS compounds.

High speed magneto-optical valve: Rapid control of the optical transmittance of aqueous solutions by magnetically induced self-assembly of superparamagnetic particle chains

Magneto-optical effects of magnetorheological fluids are of interest for applications including magnetic field sensors and optical modulators. Here, we describe the rapid control of the optical transmittance of a magnetorheological fluids by rotating columnar arrays of self-assembled superparamagnetic bead (SPB) chains by applying an external field using a permanent magnet. The columnar arrays of chains of magnetic beads acted as optical valves exhibiting distinct “on” and “off” states. For a given magnetic field, the maxima/minima of transmittance occurred when the applied field was parallel/perpendicular to light path and the intensity of light at the maxima varied with the strength of the applied field. Importantly, the response time for rotating the columnar arrays of magnetic chains was very rapid, and in the millisecond range. Our procedure provides a simple means for producing fast, magneto-optical switches that does not require cumbersome and power consuming electromagnetic coils and related peripheral equipment.

A Fluxless and Low-Temperature Flip Chip Process Based on Insertion Technique

For heterogeneous materials assembly, the thermal expansion mismatch between the chip and the substrate is a roadblock for flip chip bonding of ultrafine-pitch ( les 10 mum) and large diagonal devices ( ges 20 mm). Residual strains in bumps and device warpage have been calculated to evaluate the thermomechanical limits of a conventional flip chip soldering process using micro bumping. As a solution to overcome these limits, this paper describes a new patented flip-chip technology representing a technological breakthrough compared to conventional methods such as soldering or bonding through conductive adhesives. Electrical connections are performed by the insertion of metallic micro-tips in a ductile material. As a low-temperature process and fluxless technology, this method is adapted to fine-pitch and large devices. As a proof of concept, we present the bonding results obtained on fine-pitch large arrays of daisy chains with 500 times 500 contacts and 30 -mum pitch. The electrical contact has been demonstrated and characterized in terms of resistance and yield.

Synthesis and Structure of a Cyanoaurate-Based Organotin Polymer Exhibiting Unusual Ion-Exchange Properties

We synthesized and structurally characterized the first cyanoaurate-based organotin polymer Me(3)Sn[Au(CN)(2)] (1), which exhibits unusual ion-exchange properties. In the structure of 1, the void space of the 2D grids formed via Au...Au bonding is filled by arrays of zigzag chains joined by weak Au...Au interactions. Interestingly, the practically insoluble polymer 1 shows unusual ion-exchange properties. The polymer Me(2)Sn[Au(CN)(2)](2) (2) was obtained in the metathesis reaction of 1 with Me(2)SnCl(2). Compound 2 displays cyanide-bridged uninodal four-connected 3D nets with 6(5).8 topology corresponding to the CdSO(4) prototype. Interestingly, 2 can be converted back into 1 by metathesis with Me(3)SnCl. Moreover, we performed a series of metal-exchange experiments in which 1 was soaked in aqueous solutions of bivalent transition-metal cations M(2+) (M = Co, Ni, Cu, Zn). As a result, 1 was completely converted into transition-metal cyanoaurates. To our knowledge, this represents the first study revealing the metal-exchange properties of a cyanoaurate-based heterometallic polymer.

Assembly of two new polyoxometalate-templated supramolecular compounds by utilizing a ligand with a combination of rigidness and flexibility

Two new polyoxometalate-templated compounds, (bix)[Cu(bix)]3[PW12O40]·4H2O (1), and [Cu(bix)]3[PMo12O40] (2) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were hydrothermally synthesized, and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and single X-ray diffraction. In compound 1, the Keggin polyanions [PW12O40]3− direct the [Cu(bix)] coordination polymeric chains to form a 3D supramolecular framework with grid-like 2D channels. By changing the polyanions into [PMo12O40]3−, compound 2 is obtained, in which the [Cu(bix)] coordination polymeric chains array around the polyanions to construct a 3D supramolecular framework with 1D hexagon-like channels. Their different structures show the template effect of the polyanions. Additionally, the cyclic voltammetry measurements indicate that the supramolecular compounds keep the redox properties of their parent polyanions.

Silicon adatom chains and one-dimensionally confined electrons on 4H-SiC [formula omitted]: The (2 × 1) reconstruction

The electronic and atomic structure of the 4H-SiC ( 1 1 ¯ 02 ) - ( 2 × 1 ) surface was investigated. Photoemission data indicate that the surface contains about 2 Si layers on top of the bulk layers. Scanning tunneling microscopy images show that these adlayers are terminated by an ordered array of adatom chains separated by the unit cell size. An electronic surface state located at a binding energy of 0.8 eV shows one-dimensional confinement with dispersion only along the chains. Based on the experimental observations, a tentative (2 × 1) surface model is derived with the surface terminated by alternating chains of Si adatoms and Si dimers in between.

One-Dimensional3dElectronic Bands of Monatomic Cu Chains

The electronic structure of an array of monatomic Cu chains grown on the Pt(997) surface has been examined by angle-resolved photoemission. The monatomic wires exhibit properties associated with 3d electron confinement in one dimension. Along the wire direction, the 3d bands states display a dispersive character, with periodicity in reciprocal space defined by the wire array geometry. These observations are compared and analyzed with ab initio calculations based on the full-potential linearized augmented plane-wave method.

KDP/PEDOT:PSS mixture as a new alternative in the fabrication of pressure sensing devices

In this work we studied the mixture of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a commercial polymer, with monobasic potassium phosphate (KDP), a piezoelectric salt, as a possible novel material in the fabrication of a low cost, easy-to-make, flexible pressure sensing device. The mixture between KDP and PEDOT:PSS was painted in a flexible polyester substrate and dried. Afterwards, I × V curves were carried out. The samples containing KDP presented higher values of current in smaller voltages than the PEDOT:PSS without KDP. This can mean a change in the chain arrays. Other results showed that the material responds to directly applied pressure to the sample that can be useful to sensors fabrication.

Periodic Arrays of Cu-Phthalocyanine Chains on Au(110)

The structure of ultrathin Cu-phthalocyanine (Cu-Pc) films on the (1 × 2)-Au(110) surface has been studied. The overlayer deposition has been monitored in real time by helium atom scattering (HAS) and low energy electron diffraction (LEED). Throughout the monolayer regime the Cu-Pc molecules are systematically observed to line-up edge-to-edge along the [11̅0] direction of the Au substrate, yielding a commensurate 5-fold periodicity (14.4 Å). Cu-Pc chains deconstruct the 2-fold Au missing row order in the early stage of deposition. A set of higher order periodicities (5-, 7-, and 3-fold) are progressively observed along [001] with increasing Cu-Pc deposition, the 3-fold phase appearing at the monolayer saturation coverage. The corresponding molecular orientation has been studied by variable polarization absorption spectroscopy (XAS), whereas the Au substrate structure has been determined by out-of-plane surface X-ray diffraction. The (5 × 5) phase is found to be rather corrugated, and it exhibits a high degree of long-range order yielding the most prominent diffraction pattern. In the (5 × 5) phase, the Cu-Pc chains are found to lift the underneath missing row reconstruction, being separated by residual Au rows. Similarly, in the more compressed 3-fold monolayer phase, the Cu-Pc molecules were formerly found to lie within a shallow (1 × 3) Au reconstruction [Cossaro, A.; et al. J. Phys. Chem. B 2004, 108, 14671]. From comparison of the different deposition stages, as measured in real time by HAS, we can draw a comprehensive picture of the system evolution. In fact, the observed periodicities at different coverage are always formed by an array of Cu-Pc chains in shallow troughs that are equally spaced by a number of uncovered Au rows, as dictated by the Cu-Pc coverage. The growth of Cu-Pc arrays in the submonolayer range is thus driven by an interchain repulsion mechanism.

Dispersion and extinction of surface plasmons in an array of gold nanoparticle chains: influence of the air/glass interface

We investigate the dispersion relation and extinction properties of surface plasmons in an array of gold nanoparticle chains under s-polarized plane wave excitations, through experiment and simulation. Our results reveal that the dispersion and extinction properties of gold nanoparticle chains at an air/glass interface are significantly different from those in a uniform medium. Under total internal reflection, the dispersion is much larger than that above total internal reflection and 100% extinction can be reached. We show that the large dispersion under total internal reflection can be explained by dipole fields and coupling at the air/glass interface.

Unveiling new systematics in the self-assembly of atomic chains on Si(111)

Self-assembled arrays of atomic chains on Si(111) represent a fascinating family of nanostructures with quasi-one-dimensional electronic properties. These surface reconstructions are stabilized by a variety of adsorbates ranging from alkali and alkaline earth metals to noble and rare earth metals. Combining the complementary strength of dynamical low-energy electron diffraction, scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we recently showed that besides monovalent and divalent adsorbates, trivalent adsorbates are also able to stabilize silicon honeycomb chains. Consequently silicon honeycomb chains emerge as a most stable, universal building block shared by many atomic chain structures. We here present the systematics behind the self-assembly mechanism of these chain systems and relate the valence state of the adsorbate to the accessible symmetries of the chains.

Development of a miniaturised microarray-based assay for the rapid identification of antimicrobial resistance genes in Gram-negative bacteria

We describe the development of a miniaturised microarray for the detection of antimicrobial resistance genes in Gram-negative bacteria. Included on the array are genes encoding resistance to aminoglycosides, trimethoprim, sulphonamides, tetracyclines and β-lactams, including extended-spectrum β-lactamases. Validation of the array with control strains demonstrated a 99% correlation between polymerase chain reaction and array results. There was also good correlation between phenotypic and genotypic results for a large panel of Escherichia coli and Salmonella isolates. Some differences were also seen in the number and type of resistance genes harboured by E. coli and Salmonella strains. The array provides an effective, fast and simple method for detection of resistance genes in clinical isolates suitable for use in diagnostic laboratories, which in future will help to understand the epidemiology of isolates and to detect gene linkage in bacterial populations.

Peierls instability in Pt chains on Ge(0 0 1)

We have studied the structural and electronic properties of atomic Pt chains on a Pt modified Ge(001) substrate. Using scanning tunneling microscopy we show that these Pt chains undergo a phase transition from a 2× periodicity at room temperature to a 4× periodicity at low temperature. The coupling between the atomic chains turns out to be of essential importance, since isolated Pt chains and chains located at the edge of an array of chains maintain their 2× periodicity at temperatures as low as 4.7K. The 2× to 4× transition is accompanied by an opening of an energy gap and is interpreted in terms of a Peierls instability.