Honeycomb Network Research Articles

Localization in quantum walks on a honeycomb network

We systematically study the localization effect in discrete-time quantum walks on a honeycomb network and establish the mathematical framework. We focus on the Grover walk first and rigorously derive the limit form of the walker's state, showing it has a certain probability to be localized at the starting position. The relationship between localization and the initial coin state is concisely represented by a linear map. We also define and calculate the average probability of localization by generating random initial states. Further, coin operators varying with positions are considered and the sufficient condition for localization is discussed. We also similarly analyze another four-state Grover walk. Theoretical predictions are all in accord with numerical simulation results. Finally, our results are compared with previous works to demonstrate the unusual trapping effect of quantum walks on a honeycomb network, as well as the advantages of our method.

An Adaptation of the Hoshen-Kopelman Cluster Counting Algorithm for Honeycomb Networks

We develop a simplified implementation of the Hoshen-Kopelman cluster countingalgorithm adapted for honeycomb networks.In our implementation of the algorithm we assume that all nodes in the networkare occupied and links between nodes can be intact or broken. The algorithm counts how many clusters there are in the network and determineswhich nodes belong to each cluster. The network information is stored intotwo sets of data. The first one is related to the connectivity of the nodes andthe second one to the state of links. The algorithm finds all clusters in onlyone scan across the network and thereafter cluster relabeling operates on avector whose size is much smaller than the size of the network. Countingthe number of clusters of each size, the algorithm determines the clustersize probability distribution from which the mean cluster size parameter canbe estimated. Although our implementation of the Hoshen-Kopelman algorithmworks only for networks with a honeycomb (hexagonal) structure, itcan be easily changed to be applied for networks with arbitrary connectivitybetween the nodes (triangular, square, etc.).The proposed adaptation of the Hoshen-Kopelman cluster counting algorithmis applied to studying the thermal degradation of a graphene-like honeycombmembrane by means of Molecular Dynamics simulation with a Langevin thermostat.ACM Computing Classification System (1998): F.2.2, I.5.3.

Room temperature formaldehyde sensor with enhanced performance based on reduced graphene oxide/titanium dioxide

Reduced graphene oxide/titanium dioxide (rGO/TiO2) layered film deposition on the interdigital electrode substrate has been developed through simple thermal treatment for trace detection of formaldehyde (HCHO) at room temperature. The layered film was characterized by UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy, and the formaldehyde sensing performances of rGO/TiO2 layered film were investigated over low detection concentrations from 0.1ppmv to 0.5ppmv. An interesting abruption behavior of rGO sheets during the heating process was observed and discussed. However, the dissociation of rGO honeycomb network was prevented for rGO/TiO2 layered film upon elevated temperature, which might be induced by the synergetic interaction between TiO2 nanoparticles and graphene sheets effectively. The sensing-test results revealed that the rGO/TiO2 sensor exhibited rapid response, excellent selectivity, good reproducibility and remarkable sensitivity of 0.8ppmv−1, which was higher than that of rGO-based one (0.5ppmv−1). Furthermore, the formaldehyde-sensing mechanism was analyzed based on the combination of catalytic reactions and supporting function of TiO2 nanoparticles.

Tetrahedral Tetraphosphonic Acids. New Building Blocks in Supramolecular Chemistry

The structural characterization of tetraphenylmethane tetrakis-4-phosphonic acid (4a) and its closely related Si-analogue tetraphenylsilane tetrakis-4-phosphonic acid (4b) is reported. Crystals of 4a, obtained by crystallization at 165 °C from water under hydrothermal conditions, comprise a dense threefold interpenetrated hydrogen-bonded network. Lower calculated density cocrystals 4b·4 EtOH, attained by recrystallization from ethanol, give rise to a porous honeycomb network that shows no interpenetration. Isolated from the mother liquor, the encapsulated ethanol is rapidly lost under ambient conditions leaving amorphous 4b. While the amorphous 4b is reasonably soluble in methanol, crystalline 4a is virtually insoluble in common organic solvents.

Atomic arrangement and electron band structure of Si(1 1 1)-ß--Bi reconstruction modified by alkali-metal adsorption: ab initio study

Using ab initio calculations, atomic structure and electronic properties of Si(1 1 1)-Bi surface modified by adsorption of 1/3 monolayer of alkali metals, Li, Na, K, Rb and Cs, have been explored. Upon adsorption of all metals, a similar atomic structure develops at the surface where twisted chained Bi trimers are arranged into a honeycomb network and alkali metal atoms occupy the sites in the center of each honeycomb unit. Among other structural characteristics, the greatest variation concerns the relative heights at which alkali metals reside with respect to Bi-trimer layer. Except for Li, the other metals reside higher than Bi layer and their heights increase with atomic number. All adsorbed surface structures display similar electron band structures of which the most essential feature is metallic surface-state band with a giant spin splitting. This electronic property allows one to consider the Si(1 1 1)-Bi surfaces modified by alkali metal adsorption as a set of material systems showing promise for spintronic applications.

Superconductivity in MgPtSi: An orthorhombic variant ofMgB2

A ternary compound, MgPtSi, was synthesized by solid-state reaction. An examination of the compound by powder X-ray diffraction revealed that it crystallizes in the orthorhombic TiNiSi-type structure with the Pnma space group. The structure comprises alternately stacked layers of Mg and PtSi honeycomb network, which is reminiscent of MgB2, and the buckling of the honeycomb network causes orthorhombic distortion. Electrical and magnetic studies revealed that MgPtSi exhibited superconductivity with a transition temperature of 2.5 K. However, its isostructural compounds, namely, MgRhSi and MgIrSi, were not found to exhibit superconductivity.

Syntheses, crystal structures, and properties of four complexes based on polycarboxylate and imidazole ligands

Four metal–organic coordination polymers [Zn(HL)(H2O)]·4H2O (1), [Zn(HL)(L1)]·4H2O (2), [Cu(HL)(H2O)]·3H2O (3) and [Cu(HL)(L1)]·5H2O (4) were synthesized by reactions of the corresponding metal(II) salts with semirigid polycarboxylate ligand (5-((4-carboxypiperidin-1-yl)methyl)isophthalic acid hydrochloride, H3L·HCl) or auxiliary ligand (1,4-di(1H-imidazol-4-yl)benzene, L1). The structures of the compounds were characterized by elemental analysis, FT-IR spectroscopy and single-crystal X-ray diffraction. The use of auxiliary ligand L1 has great influence on the structures of two pairs of complexes 1, 2 and 3, 4. Complex 1 is a uninodal 3-connected rare 2-fold interpenetrating ZnSc net with a Point (Schlafli) symbol of (103) while 2 is a one-dimensional (1D) ladder structure. Compound 3 features a two-dimensional (2D) honeycomb network with typical 63-hcb topology, while 4 is 2D network with (4, 4) sql topology based on binuclear CuII subunits. The non-covalent bonding interactions such as hydrogen bonds, π···π stacking and C–H···π exist in complexes 1–4, which contributes to stabilize crystal structure and extend the low-dimensional entities into high-dimensional frameworks. And the photoluminescent property of 1 and 2 and gas sorption property of 4 have been investigated.

Dynamics of driven flow with exclusion in graphenelike structures.

We present a mean-field theory for the dynamics of driven flow with exclusion in graphenelike structures, and numerically check its predictions. We treat first a specific combination of bond transmissivity rates, where mean field predicts, and numerics to a large extent confirms, that the sublattice structure characteristic of honeycomb networks becomes irrelevant. Dynamics, in the various regions of the phase diagram set by open boundary injection and ejection rates, is then in general identical to that of one-dimensional systems, although some discrepancies remain between mean-field theory and numerical results, in similar ways for both geometries. However, at the critical point for which the characteristic exponent is z=3/2 in one dimension, the mean-field value z=2 is approached for very large systems with constant (finite) aspect ratio. We also treat a second combination of bond (and boundary) rates where, more typically, sublattice distinction persists. For the two rate combinations, in continuum or late-time limits, respectively, the coupled sets of mean-field dynamical equations become tractable with various techniques and give a two-band spectrum, gapless in the critical phase. While for the second rate combination quantitative discrepancies between mean-field theory and simulations increase for most properties and boundary rates investigated, theory still is qualitatively correct in general, and gives a fairly good quantitative account of features such as the late-time evolution of density profile differences from their steady-state values.

Luminescent Two-Dimensional Coordination Polymer for Selective and Recyclable Sensing of Nitroaromatic Compounds with High Sensitivity in Water

A stable two-dimensional (2D) coordination Cd(II) polymer [Cd(ppvppa)(1,4-NDC)]n (1) (ppvppa = N-(pyridin-2-yl)-N-(4-(2-(pyridin-4-yl)vinyl)phenyl)pyridin-2-amine; 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid) was prepared by the solvothermal reactions of Cd(NO3)2·4H2O with ppvppa and 1,4-H2NDC in H2O and MeCN at 150 °C. Compound 1 was characterized by elemental analysis, IR, powder X-ray diffraction (PXRD), and single crystal X-ray diffraction and thermogravimetric analysis (TGA). Compound 1 consists of dimeric [Cd2(μ-ppvppa)2] fragments linked by 1,4-NDC bridges to generate a 2D honeycomb network. Complex 1 strongly emits blue light in the solid state when excited at 419 nm at ambient temperature. This emission is selectively quenched by nitro aromatic compounds in water with good sensitivity. Compound 1 also displays recyclable detection of nitro aromatic compounds.

Stoichiometry engineering of ternary oxide ultrathin films:BaxTi2O3on Au(111)

Ternary oxide ${\mathrm{Ba}}_{x}{\mathrm{Ti}}_{2}{\mathrm{O}}_{3}$ ultrathin films on Au(111) substrates $(x\ensuremath{\le}2/3)$ have been studied using a joint experimental and theoretical approach, including the use of scanning tunneling microscopy (STM), first principles calculations, and Monte Carlo simulations. The films are created by first covering the Au(111) substrate with a ${\mathrm{Ti}}_{2}{\mathrm{O}}_{3}\phantom{\rule{0.28em}{0ex}}(2\ifmmode\times\else\texttimes\fi{}2)$ honeycomb (HC) network and then evaporating low concentrations of Ba atoms onto this film. STM imaging shows that the Ba atoms adsorb individually in the hollow sites of the HC network. Depending on the Ba coverage $x$, which ranges from 0 to 2/3, two ordered phases can be identified at $x=1/3$ and $x=2/3$. A disordered labyrinthlike phase is observed for values of $x$ between 1/3 and 2/3. Theoretical modeling shows that the structural character of these films is driven by the charge transfer that occurs between the electropositive Ba atoms and the electronegative ${\mathrm{Ti}}_{2}{\mathrm{O}}_{3}$/Au substrate. This results in a number of calculated effects including an increase in the film rumpling and a reduction of the film work function with increasing $x$. The evolution of the structure of the thin films as a function of Ba coverage can be described by a lattice gas model with first-, second-, and third-neighbor Ba-Ba repulsive interactions. The range of the dipolar interactions is a key factor in understanding the behavior of Ba ordering. The structural and electronic flexibility, which can be engineered through stoichiometry, temperature, or support control, makes these ultrathin films promising materials for applications related to adsorption or reactivity, or as template supports for the growth of size-selected clusters.

Crystal Structure of the Spin 1/2 Honeycomb-Lattice Antiferromagnet Cu2(pymca)3(ClO4)

Using X-ray diffraction techniques, we have studied the crystal structure of a copper polynuclear coordination polymer Cu2(pymca)3(ClO4) (pymca = pyrimidine-2-carboxylate), which is found to crystallize as a trigonal crystal system, space group P31m, with the lattice constants a = 9.5904(18) A and c = 5.9000(11) A, at temperature T = 150 K. Each pymca ligand connects to two Cu2+ ions, forming a honeycomb network in the ab plane. The T dependence of the magnetic susceptibility of Cu2(pymca)3(ClO4) shows a broad maximum near T = 26 K, indicating low-dimensional antiferromagnetic interactions. From the crystal structure and magnetic properties, we conclude that Cu2(pymca)3(ClO4) is a good realization of a spin-1/2 honeycomb lattice antiferromagnet.

Stretchable Conductive Networks of Carbon Nanotubes Using Plasticized Colloidal Templates

We present a study of the behavior of highly ordered, segregated single-wall carbon nanotube networks under applied strain. Polymer latex templates induce self-assembly of carbon nanotubes into hexagonal (2D) and honeycomb (3D) networks within the matrix. Using mechanical and spectroscopic analysis, we have studied the strain transfer mechanisms between the carbon nanotube network and the polymer matrix. Axial deformation of the nanotube network under applied strain is indicated by downshifts in the 2D mode in the Raman spectra, as well as variation in the Radial Breathing modes. The slippage within nanotube bundles at high strain is indicated by a reduction in the 2D mode rate of change. The fractional resistance change of the composites with strain obeys power law dependence. We present a model for the behavior of carbon nanotube bundles under strain informed by these measurements, and potential applications for such composite materials in elastic electronic devices that can tolerate high strain.

Quantum confinement in self-assembled two-dimensional nanoporous honeycomb networks at close-packed metal surfaces.

Quantum confinement of a two-dimensional electron gas by supramolecular nanoporous networks is investigated using the boundary elements method based on Green's functions for finite geometries and electron plane wave expansion for periodic systems. The "particle in a box" picture was analyzed for cases with selected symmetries that model previously reported architectures constructed from organic and metal-organic scattering centers confining surface state electrons of Ag(111) and Cu(111). First, by analyzing a series of cases with systematically defined parameters (scattering geometry, potentials, and effective broadening), we demonstrate how the scattering processes affect the properties of the confined electrons. For the features of the local density of states reported by scanning tunneling spectroscopy (STS), we disentangle the contributions of lifetime broadening and splitting of quantum well states due to coupling of neighboring quantum dots. For each system, we analyze the local electron density distribution and relate it to the corresponding band structure as calculated within the plane-wave expansion framework. Then, we address two experimental investigations, where in one case only STS data and in the other case mainly angle-resolved photoemission spectroscopy (ARPES) data were reported. In both cases, the experimental findings can be successfully simulated. Furthermore, the missing information can be complemented because our approach allows to correlate the information obtained by STS with that of ARPES. The combined analysis of several observations suggests that the scattering potentials created by the network originate primarily from the adsorbate-induced changes of the local surface dipole barrier.

Emerging frontiers of graphene in biomedicine.

Graphene is a next-generation biomaterial with increasing biomedical applicability. As a new class of one-atom-thick nanosheets, it is a true two-dimensional honeycomb network nanomaterial that attracts interest in various scientific fields and is rapidly becoming the most widely studied carbon-based material. Since its discovery in 2004, its unique optical, mechanical, electronic, thermal, and magnetic properties are the basis of exploration of the potential applicability of graphene. Graphene materials, such as graphene oxide and its reduced form, are studied extensively in the biotechnology arena owing to their multivalent functionalization and efficient surface loading with various biomolecules. This review provides a brief summary of the recent progress in graphene and graphene oxide biological research together with current findings to spark novel applications in biomedicine. Graphene-based applications are progressively developing; hence, the opportunities and challenges of this rapidly growing field are discussed together with the versatility of these multifaceted materials.

Superhydrophilic and underwater superoleophobic mesh coating for efficient oil–water separation

High efficiency of oil–water separation was easily achieved with reusable metal meshes coated by NiOOH nanoflake honeycomb network.

On the linear stability of blood flow through model capillary networks.

Under the approximation that blood behaves as a continuum, a numerical implementation is presented to analyze the linear stability of capillary blood flow through model tree and honeycomb networks that are based on the microvascular structures of biological tissues. The tree network is comprised of a cascade of diverging bifurcations, in which a parent vessel bifurcates into two descendent vessels, while the honeycomb network also contains converging bifurcations, in which two parent vessels merge into one descendent vessel. At diverging bifurcations, a cell partitioning law is required to account for the nonuniform distribution of red blood cells as a function of the flow rate of blood into each descendent vessel. A linearization of the governing equations produces a system of delay differential equations involving the discharge hematocrit entering each network vessel and leads to a nonlinear eigenvalue problem. All eigenvalues in a specified region of the complex plane are captured using a transformation based on contour integrals to construct a linear eigenvalue problem with identical eigenvalues, which are then determined using a standard QR algorithm. The predicted value of the dimensionless exponent in the cell partitioning law at the instability threshold corresponds to a supercritical Hopf bifurcation in numerical simulations of the equations governing unsteady blood flow. Excellent agreement is found between the predictions of the linear stability analysis and nonlinear simulations. The relaxation of the assumption of plug flow made in previous stability analyses typically has a small, quantitative effect on the stability results that depends on the specific network structure. This implementation of the stability analysis can be applied to large networks with arbitrary structure provided only that the connectivity among the network segments is known.

Spectrum of a Dilated Honeycomb Network

We analyze spectrum of Laplacian supported by a periodic honeycomb lattice with generally unequal edge lengths and a $\delta$ type coupling in the vertices. Such a quantum graph has nonempty point spectrum with compactly supported eigenfunctions provided all the edge lengths are commensurate. We derive conditions determining the continuous spectral component and show that existence of gaps may depend on number-theoretic properties of edge lengths ratios. The case when two of the three lengths coincide is discussed in detail.

Tuning Two-Dimensional Layer to Three-Dimensional Pillar-Layered Metal–Organic Frameworks: Polycatenation and Interpenetration Behaviors

A two-dimensional honeycomb network of {[Zn2(bpydb)2(H2O)2](DMA)3(H2O)}n (1) was solvothermally synthesized and structurally characterized. By employing 4,4′-bipyridine (bpy) as a pillar, two additional three-dimensional (3D) metal–organic frameworks (MOFs) of {[Zn2(bpydb)2(bpy)(EtO-H)2](DMF)(EtOH)}n (2) and {[Zn(bpydb)(bpy)](DMA)(EtOH)6}n (3) (bpydbH2 = 4,4′-(4,4′-bipyridine-2,6-diyl) dibenzoic acid, DMA = N,N- dimethylacetamide, DMF = N,N-dimethylformamide) were obtained. MOF 2 displays a 3D pillar-bilayered network generated from polycatenation of the 2D bilayers. By carefully adjusting the reaction condition, MOF 3 was harvested, showing a 2-fold interpenetrated (3,5)-connected hms net. The phase purity, thermal stability, and luminescent properties of the three MOFs were studied. In addition, N2 and CO2 adsorption behaviors of the activated 3 were investigated.

Strain isolation: A simple mechanism for understanding and detecting structures of zero Poisson's ratio

There exist several honeycomb networks exhibiting zero Poisson's ratio (ZPR). Applications of these networks can be found in different fields. The ZPR properties of these structures have been mechanically modeled and tested. However, the underlying mechanism driving the ZPR behavior has not been paid much attention. The present work focuses on the deformation mechanism of the ZPR networks. Through the discussion and comparison of the deformation process of the ZPR, auxetic and common honeycomb networks, the strain‐isolation mechanism is proposed to explain the ZPR behavior. Then, according to this mechanism, the reversed semi‐re‐entrant (RSRE) honeycomb is created. With experimental measurements and finite‐element analysis (FEA), the ZPR properties of the RSRE can be proven. The strain‐isolation mechanism can not only explain the ZPR behavior but also be used in the design of new ZPR honeycomb networks. 3D ZPR structures are also derived from the 2D honeycomb networks. Their Poisson's ratios in 3D space are also discussed based on FEA results. The model of the 3D RSRE structure showing ZPR behaviors in three orthogonal planes.

Comparison of Three New Drying Methods for Drying Characteristics and Quality of Shiitake Mushroom (Lentinus edodes)

This articles provides results of an experimental investigation of three hybrid drying technologies on the drying characteristics and key quality parameters of shiitake mushroom (Lentinus edodes). The drying techniques tested at the laboratory scale are mid-infrared-assisted convection drying (MIRCD), hot air coupled with radio frequency drying (HCRFD), and hot air coupled with microwave drying (HCMD). For comparison, the standard drying technique using hot air was also tested. The quality parameters include texture, color, rehydration rate, shrinkage, nutrient retention, microstructure, etc. These four drying tests were conducted at fixed air temperature (60°C), and the power level for HCRFD, MIRCD, and HCMD was fixed at 4 W/g. The results showed that hot air coupled with microwave drying gave the shortest drying time, and mid-infrared-assisted convection and hot air coupled with radio frequency drying showed better color attributes and nutrient retention. Under the conditions tested, mid-infrared-assisted convection drying yielded minimal shrinkage (maximal rehydration) and lower hardness upon rehydration. The uniform honeycomb network and less collapsed structure of MIRCD samples can be used to explain these better quality characteristics.