Synthesis, Crystal Structure and Properties of a New Zn(II) Coordination Polymer Constructed from 2,3-Pyridine Dicarboxylic Acid and 1,1′-(1,4-Butanediyl)bis(imidazole)

A new coordination polymer, namely [Zn（pdc）（bbi）]n {H2 pdc = 2,3-pyridine dicar- boxylic acid, bbi = 1,1-（1,4-butanediyl）bis（imidazole）}, has been prepared under hydrothermal conditions and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. It crystallizes in monoclinic, space group P21 /n with a = 8.436（3）, b = 16.988（5）, c = 12.106（4）, β = 92.204（5）°, V = 1733.6（9）3, Z = 4, C17 H17 N5 O4 Zn, Mr = 420.73, Dc = 1.612 g/cm3, F（000） = 864, μ（MoKa） = 0.452 mm-1, the R = 0.0672 and wR = 0.1645. In the mononuclear complex, each Zn（II） is five-coordinated by one carboxylate O and one pyridyl N atoms from one pdc anion, one carboxylate O atom from another pdc anion, and two N atoms from two bib ligands. The Zn（II） ions are connected by pdc ligands to form skeleton chains, and bbi ligands further link them to construct a 2D framework. The thermal and luminescence properties of the complex were also investigated.

Recent developments of quantum dot based micro-LED based on non-radiative energy transfer mechanism

With regard to micro-light-emitting diodes(micro-LEDs),their excellent brightness,low energy consumption,and ultrahigh resolution are significant advantages.However,the large size of traditional inorganic phosphors and the number of side defects have restricted the practical applications of small sized micro-LEDs.Recently,quantum dot(QD)and nonradiative energy transfer(NRET)have been proposed to solve existing problems.QDs possess nanoscale dimensions and high luminous efficiency,and they are suitable for NRET because they are able to nearly contact the micro-LED chip.The NRET between QDs and micro-LED chip further improves the color conversion efficiency(CCE)and effective quantum yield(EQY)of full-color micro-LED devices.In this review,we discuss the NRET mechanism for QD micro-LED devices,and then nano-pillar LED,nano-hole LED,and nano-ring LED are introduced in detail.These structures are beneficial to the NRET between QD and micro-LED,especially nano-ring LED.Finally,the challenges and future envisions have also been described.

Theoretical optoelectronic analysis of intermediate-band photovoltaic material based on ZnY_(1-x) O_x(Y = S,Se,Te) semiconductors by first-principles calculations

The structural, energetic, and electronic properties of lattice highly mismatched ZnY1-xOx （Y = S, Se, Te） ternary alloys with dilute O concentrations are calculated from first principles within the density functional theory. We demonstrate the formation of an isolated intermediate electronic band structure through diluted O-substitute in zinc-blende ZnY （Y = S, Se, Te） at octahedral sites in a semiconductor by the calculations of density of states （DOS）, leading to a significant absorption below the band gap of the parent semiconductor and an enhancement of the optical absorption in the whole energy range of the solar spectrum. It is found that the intermediate band states should be described as a result of the coupling between impurity O 2p states with the conduction band states. Moreover, the intermediate bands （IBs） in ZnTeO show high stabilization with the change of O concentration resulting from the largest electronegativity difference between O and Te compared with in the other ZnSO and ZnSeO.

Fabrication and Characterization of GaN-Based Micro-LEDs on Silicon Substrate

GaN-based micro light emitting diodes(micro-LEDs) on silicon(Si)substrates with 40μm in diameter are developed utilizing standard photolithography and inductively coupled plasma etching techniques.From currentvoltage curves,the relatively low turn-on voltage of 2.8 V and low reverse leakage current in the order of 10-8 A/cm2 indicate good electrical characteristics.As the injection current increases,the electroluminescence emission wavelength hardly shifts at around 433 nm, and the relative external quantum efficiency slightly decays,because the impact of quantum-confined Stark effect is not serious in violet-blue micro-LEDs.Since GaN-LEDs are cost effective on large-area Si and suitable for substrate transfer or vertical device structures,the fabricated micro-LEDs on Si should have promising applications in the fields of high-resolution display and optical communication.

Transformation behaviors,structural and magnetic characteristics of Ni-Mn-Ga films on MgO(001)

Ferromagnetic Ni-Mn-Ga films were fabricated by depositing on MgO （001） substrates at temperatures from 673 K to 923 K. Microstructure, crystal structure, martensitic transformation behavior, and magnetic properties of the films were studied. With increasing deposition temperature, the surface morphology of the films transforms from granular to continu- ous. The martensitic transformation temperature is not dependent on deposition temperature; while transformation behavior is affected substantially by deposition temperature. X-ray analysis reveals that the film deposited at 873 K has a 7M marten- site phase, and its magnetization curve provides a typical step-increase, indicating the occurrence of magnetically induced reorientation （MIR）. In situ magnetic domain structure observation on the film deposited at 873 K reflects that the marten- sitic transformation could be divided into two periods： nucleation and growth, in the form of stripe domains. The MIR occurs at the temperature at which martensitic transformation starts, and the switching field increases with the decrease of temperature due to damped thermal activation. The magnetically induced martensitic transformation is related to the difference of magnetization between martensite and austenite. A shift of martensite temperature of dT/dH = 0.43 K/T is observed, consistent with the theoretical value, 0.41 K/T.

Evolution of magnetic domain structure of martensite in Ni–Mn–Ga films under the interplay of the temperature and magnetic field

Ferromagnetic shape memory Ni-Mn-Ga films with 7M modulated structure were prepared on MgO （001） substrates by magnetron sputtering. Magnetization process with a typical two-hysteresis loop indicates the occurrence of the reversible magnetic field-induced reorientation. Magnetic domain structure and twin structure of the film were controlled by the in- terplay of the magnetic and temperature field. With cooling under an out-of-plane magnetic field, the evolution of magnetic domain structure reveals that martensitic transformation could be divided into two periods： nucleation and growth. With an in-plane magnetic field applied to a thermomagnetic-treated film, the evolution of magnetic domain structure gives evidence of a reorientation of twin variants of martensite. A microstructural model is described to define the twin structure and to produce the magnetic domain structure at the beginning of martensitic transformation; based on this model, the relationship between the twin structure and the magnetic domain structure for the treated film under an in-plane field is also described.

Effect of second introduced phase on magnetotransport properties of La_(2/3)Sr_(1/3)MnO_3/0.33(CuO, ZnO, Al_2O_3) composites

The structure, magnetic and magnetotransport properties of La2/3Sr1/3MnO3(LSMO)/0.33(CuO, ZnO, Al2O3) compositeswere investigated to explore the role of second introduced phase. The microstructural analysis shows two kinds of grain boundaries:LSMO/LSMO and LSMO/second phase/LSMO. Two maximal resistivities appear in LSMO/0.33CuO and LSMO/0.33ZnOcomposites while the resistivity of LSMO/0.33Al2O3 decreases monotonically with increasing the temperature from 200 K to 400 K.Moreover, the temperature dependence of magnetoresistance(MR) of LSMO/0.33Al2O3 that decreases monotonically with increasingthe temperature is different from that of LSMO/0.33CuO and LSMO/0.33ZnO. A developed two-channel model consisting ofscattering model and tunneling model was proposed to fit the resistivity—temperature curves of these composites. The role of secondintroduced phase and the magnetotransport mechanism of these composites were elucidated.

Syntheses, Crystal Structures and Properties of Two Metal-organic Complexes Based on 5-(4-Pyridyl)-methoxyl Isophthalic Acid

Two new metal-organic frameworks, [Co3L2（NO2）2（H2O）2],, （1） and{[Ni（L）（H2O）5] （H2O）2.DMF}, （2, H2L = 5-（4-pyridyl）-methoxyl isophthalic acid）, have been synthesized by the hydrothermal method and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis （TGA） and X-ray crystallography. Compound 1 crystallizes in the monoclinic system with space group P2/c and adopts a slightly distorted octahedral configuration. In compound 1, the 2D bilayered structures are linked by O-H...O and O-H...N hydrogen bonds to form a 3D framework. Compound 2 crystallizes in the monoclinic system with space group P2/n, and the central nickel atoms are octa-coordinated with five O atoms from coordinated water molecules and one N atom from one H2L ligand. The abundant O-H…O hydrogen bonds and π…π interactions link the molecules into a 3D framework. In addition, compounds 1 and 2 exhibit strong ultraviolet absorption in the solid state at room temperature.

Hydrothermal Synthesis, Crystal Structure and Luminescence Properties of a New 2D Cadmium Complex Based on the 4,4'-Bis(benzimidazol-1-ylmethy1)biphenyl and Glutaric Acid Ligands

A new polymeric complex {[Cd2（bbmb）2（gt）2]＇（H2O）2}, （bbmb = 4,4＇-bis（benzimidazol-l-ylmethyl）biphenyl, H2gt = glutaric acid） has been obtained by hyclrothermal method and structurally characterized by elemental analysis, IR, XRD, TGA and single-crystal X-ray diffraction. The complex belongs to the triclinic system, space group P1 with a = 10.2417（15）, b = 13.752（2）, c = 22.201（3） A, a = 73.899（2）, β = 88.416（2）, y = 78.305（2）°, V = 2940.4（7） A3, Z = 2, C66H56Cd2N808, Mr = 1313.99, Dc = 1.484 g/cm3, F（000） = 1336 and μ = 0.787 mm-1, and features a 2D network. In the solid state at room temperature, the cadmium（Ⅱ） complex exhibits strong fluorescence absorption at 435 nm （λmax）.

Synthesis, Crystal Structure and Water-induced Reversible Crystal-to-amorphous Transformation Property of [{Ni(IBG)(4,4'-bipy)(H_2O)_2}·3H_2O]_n

A novel NiII complex [{Ni（IBG）（4,4＇-bipy）（H2O）2}·3H2O]n 1 （H2IBG = isophthaloylbisglycine and 4,4＇-bipy = 4,4＇-bipyridine） has been synthesized and characterized by singlecrystal X-ray diffraction, elemental analysis, IR spectra and thermogravimetric analysis. It crystallizes in monoclinic, space group P2/c with a = 15.5420（7）, b = 22.4344（1）, c = 8.3455（5）, β = 101.538（3）o, V = 2670.1（7）3, Z = 4, C22H32N4NiO13, Mr = 619.23, Dc = 1.443 g/cm3, F（000） = 1296.0, μ（MoKα） = 0.750 mm-1, the final R = 0.0570 and wR = 0.1445 for 2296 observed reflections with I 〉 2σ（I）. In the structure, the NiII metal center is coordinated in an octahedral environment arranged by two water molecules, two carboxylate oxygen atoms and two nitrogen atoms from two 4,4＇-bipy ligands. Thermal decomposition and powder X-ray diffraction results indicate that the transformation from the crystal form, [{Ni（IBG）（4,4＇-bipy）（H2O）2}·3H2O]n, to the amorphous powder, Ni（IBG）（4,4＇-bipy）（H2O）2, is reversible, so the latter form may be utilized as an absorbing agent for water and water vapor.

Syntheses and Crystal Structures of Four Cobalt Supramolecular Architectures with Hmtyaa Ligand

Four cobalt supramolecular architectures with Hmtyaa（2-（5-methyl-1,3,4-thiadiazol-2-ylthio）acetic acid） ligand have been synthesized.[Co（mtyaa）2（H2O）4]·4（H2O）（1）：triclinic,space group P1 with a = 6.7537（18）,b = 8.591（2）,c = 10.615（3） ,α = 96.495（4）,β = 99.955（5）,γ = 103.615（5）°,V = 581.9（3） 3,Z = 1,Mr = 581.52,Dc = 1.659 g/m3,μ = 1.158 mm-1,F（000） = 301,Rint = 0.0557,R = 0.0377 and wR = 0.1056 for 1854 observed reflections with Ⅰ 〉 2σ（Ⅰ）;{[Co（4,4＇-bipy）（H2O）4]·2（mtyaa）·2（H2O）}n（2）：triclinic,space group P1 with a = 7.669（2）,b = 8.840（3）,c = 11.521（4） ,α = 79.912（5）,β = 73.954（5）,γ = 86.612（6）°,V = 738.9（4） 3,Z = 1,Mr = 701.67,Dc = 1.577 g/m3,μ = 0.924 mm-1,F（000） = 363,Rint = 0.0636,R = 0.0498 and wR = 0.1311 for 2155 observed reflections with Ⅰ 〉 2σ（Ⅰ）;{[Co（4,4＇-bipy）（mtyaa）（H2O）3]（mtyaa）·2（H2O）}（3）：monoclinic,space group Pc with a = 7.7832（17）,b = 11.527（3）,c = 31.483（7） ,β = 91.952（4）°,V = 2822.9（11） 3,Z = 4,Mr = 683.65,Dc = 1.609 g/m3,μ = 0.963 mm-1,F（000） = 1412,Rint = 0.0758,R = 0.0609 and wR = 0.1095 for 5841 observed reflections with I 〉 2σ（I）;{[Co（bpe）（mtyaa）2（H2O）2]}n（4）：monoclinic,space group C2/c with a = 19.290（11）,b = 12.027（7）,c = 14.865（8） ,β = 125.648（8）°,V = 2802（3）3,Z = 4,Mr = 657.66,Dc = 1.559 g/m3,μ = 0.959 mm-1,F（000） = 1356,Rint = 0.0456,R = 0.0332 and wR = 0.0985 for 2299 observed reflections with Ⅰ 〉 2σ（Ⅰ）.

Topology and Photoluminescence Property of a Neodymium-carboxylate Coordination Polymer Based on a Tripodal Flexible Ligand

A new metal-organic coordination polymer {[Nd（tci）（H2O）2]·2H2O}n（1） has been synthesized based on the flexible tricarboxylate ligand tris（2-carboxyethyl）isocyanuric acid（H3tci） and structurally characterized by single-crystal X-ray diffraction analyses, elemental analysis, infrared spectra（IR）, powder X-ray diffraction（PXRD） and thermogravimetric analysis（TGA）. Complex 1 crystallizes in triclinic, space group P1 with a = 9.1648（11）, b = 9.3326（12）, c = 12.440（2） , C（12）H（20）N3O（13） Nd, Mr = 558.55, V = 886.9（2） 3, Z = 2, Dc = 2.092 g·cm-3, μ = 3.006 mm-1, F（000） = 554, 2.56〈θ〈25.00°, λ（Mo Kα） = 0.71073 , T = 293（2） K, the final R = 0.0662 and w R = 0.2071. X-ray diffraction analysis reveals that complex 1 is a two-dimensional layer, which is further assembled into a three-dimensional supramolecular architecture through hydrogen bonding interactions. The structure of complex 1 can be simplified as a rare 2-periodic uninodal {48·62} topology and a non-interpenetrating kgd topology. Furthermore, the thermal stability and photoluminescence property of 1 were investigated.

Nonuniform Distribution of Capping Ligands Promoting Aggregation of Silver Nanoparticles for Use as a Substrate for SERS

Citrate-reduced silver nanoparticles (Ag-NPs) are used extensively for surface-enhanced Raman scattering (SERS) studies, but are typically found to aggregate using an aggregation agent. This study is aimed at developing a simple, stable, and reproducible aggregated method for Ag-NPs without any aggregation agents in aqueous solutions. The aggregation is induced by the process of centrifugation, water washing and ultrasonication. A mechanism based on the nonuniform distribution of capping ligands is proposed to account for the aggregated structure formation. UV-Vis-NIR extinction spectra and TEM allowed us to identify the existence of Ag-NPs aggregation. Further, due to the polydisperse mixture of Ag-NPs (20~65 nm) used in the present work, Ag-NPs are aggregated closely, which contribute to the observation of low-concentration SERS from the residual citrate layer or even the single-molecule SERS of R6Gon aggregation. After the evaporation of droplet of Ag-NPs aggregation on the Si substrate, citrate or R6Gcould also be detected but with marked redor blue-shifts.

Dy substitution effect on the temperature dependences of magnetostriction in Pr_(1-x)Dy_xFe_(1.9) alloys

The temperature dependences of magnetostriction in Pr（1 x）DyxFe（1.9）（0 ≤ x ≤ 1.0） alloys between 5 K and 300 K were investigated.An unusual decrease of magnetostriction with temperature decreasing was found in Pr-rich alloys（0 ≤x ≤ 0.2）,due to the change of the easy magnetization direction（EMD）.Dy substitution reduces the magnetostriction in high-magnetic field（10 kOe ≤ H≤90 kOe） at 5 K,while a small amount of Dy substitution（x = 0.05） is beneficial to increasing the magnetostriction in low-magnetic field between 10 K and 50 K.This makes the alloys a potential candidate for low temperature applications.

Controllable synthesis,characterization,and growth mechanism of hollow Zn_x Cd_(1-x) S spheres generated by a one-step thermal evaporation method

Novel hollow ZnxCdl xS spheres that are uniform in size are synthesized through the one-step thermal evaporation of a mixture of Zn and CdS powder. From an X-ray diffraction （XRD） study, the hexagonal wurtzite phase of ZnxCdl_xS is verified, and the Zn mole fraction （x） is determined to be 0.09. According to the experimental results, we propose a mechanism for the growth of Zn0.09Cd0.91S hollow spheres. The results of the cathodoluminescence investigation indicate uniform Zn, Cd, and S distribution of alloyed Zn0.09Cd0.91S, instead of separate CdS, ZnS, or nanocrystals of a core- shell structure. To the best of our knowledge, the fabrication of ZnxCd1-xS hollow spheres of this kind by one-step thermal evaporation has never been reported. This work would present a new method of growing and applying hollow spheres on Si substrates, and the discovery of the Zn0.09Cd0.91S hollow spheres would make the investigation of ZnxCd1-xS micro/nanostructures more interesting and intriguing.

Application of sampled grating to control the lasing wavelength in complex-coupled DFB laser

This paper reports that the complex-coupled distributed feedback laser with the sampled grating has been designed and fabricated.The ＋1st order reflection of the sampled grating is utilized for laser single mode operation,which is 1.5387 μm in the experiment.The typical threshold current of the device is 30 mA,and the optical output power is about 10 mW at the injection current of 100 mA.

Simulation and Suppression of the Gas Phase Pre-reaction in Metal-Organic Chemical Vapor Deposition of ZnO

The reaction mechanism and simulations of the metal-organic chemical vapor deposition reactor for ZnO film growth are presented,indicating the temperature of the reaction species.The gas phase pre-reaction can be modulated by several factors or conditions.Simulations verify the relationships between temperature and pyrolysis of precursors,and further reveal that the substrate temperature and flow rate of cooling water have great impacts on the temperature distribution.The experimental results agree with the simulations.

Optical and magneto–optical properties of periodic Co double layer film

Co double layer film （CoDLF） consisting of a disk-array layer and an antidot-array layer, both with square order, was investigated. Both the reflectivity and Kerr spectra of CoDLF show anisotropic effects when the azimuthal angle of incident light changes. From the simulation result of surface plasmon polaritons （SPPs）, we attribute the reflectivity minima and Kerr angle maxima in the spectra mainly to the excitation of different diffractional orders＇ SPPs. More interestingly, the Kerr angle changes sign at specific wavelengths. We attribute these phenomena to the excitation of SPPs and localized surface plasmons （LSPs）, and the interaction between them.

Identification of surface oxygen vacancy-related phonon–plasmon coupling in TiO_2 single crystal

Oxygen vacancies （OVs） play a critical role in the physical properties and applications of titanium dioxide nanos- tructures, which are widely used in electrochemistry and photo catalysis nowadays. In this work, OVs were artificially introduced in the surface of a pure TiO2 single crystal by pulsed laser irradiation. Raman spectra showed that the intensity of Eg mode was enhanced. Theoretical calculations disclose that this was caused by the strong coupling effect between the phonon vibration and plasmon induced by the OVs-related surface deformation, and good agreement was achieved between the experiments and theory.

A Band-Gap Energy Model of the Quaternary Alloy In_(x)Ga_(y)Al_(1−x−y)N using Modified Simplified Coherent Potential Approximation

Based on modification of the simplified coherent potential approximation,a model for the band-gap energy of In_(x)Ga_(y)Al_(1−x−y)N is developed.The parameters of the model are obtained by fitting the experimental band-gap energy of their ternary alloys.It is found that the results agree with the experimental values better than those reported by others,and that the band-gap reduction of In_(x)Ga_(y)Al_(1−x−y)N with increasing In or Ga content is mainly due to enhanced intraband coupling within the conduction band,and separately within the valence band.