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A 2-D chiral entangled coordination polymer, {Mn3(2,2′-bpy)2(3-cpta)2·H2O}n (1) (3-H3cpta=3-(3′-carboxyphenoxy)phthalic acid, 2,2′-bpy=2,2′-bipyridine), has been synthesized via the solvothermal method. X-ray diffraction analysis reveals that 1 consists of one right-handed helical chain and one wavelike 2-D plane, which are connected with each other through hydrogen bonds and π···π interactions to generate a 3-D supra-molecule. Thermal gravimetric analysis shows that 1 possesses good thermal stability. Temperature dependent magnetic susceptibilities have also been measured from 1.8 to 300 K, which shows 1 to be anti-ferromagnetic. [ABSTRACT FROM AUTHOR]

Four methods were adopted to prepare samples 20%NiO/Al 2 O 3 with calcination fixed at 500 °C, which were then reduced into 20%Ni/Al 2 O 3 and used as catalysts for reaction of selective methanation of CO in H 2 -rich gas (CO-SMET). XRD and TPR measurements indicate that nickel aluminates were formed in the calcined samples and their formation was influenced by preparation methods. Higher temperatures were required to reduce the calcined samples more efficiently and to achieve a higher catalytic activity for CO-SMET. Among the four methods, the precipitation method using ammonium carbonate as precipitant produced the highest catalytic activity both for CO methanation and for CO 2 methanation after reduction at 800 °C for 2 h. The calcined sample 20%NiO/Al 2 O 3 prepared with the method was therefore used as support and impregnated with Ru 3+ solution. Ru addition promoted reduction of Ni 2+ ions in the calcined sample even at the low temperatures of 400 °C and 500 °C. The catalyst 1%Ru–20%Ni/Al 2 O 3 reduced at 500 °C thus had a superior performance, removing CO to ca. 30 ppm with a selectivity as high as 75% at reaction temperature of 220 °C. [ABSTRACT FROM AUTHOR]

Nanopatterned sapphire substrates were prepared by solid state reaction of patterned Al films obtained by E-Beam lithography of a PMMA/copolymer bilayer resist and lift-off. The effect of exposure parameters and annealing on the structure and morphological properties of nanopatterned sapphire substrates prepared by solid state reaction were investigated by a scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Raman, respectively. The circular Al patterns with diameter/spacing being 500nm/1000nm were obtained by optimal exposure diameter/exposure dosage of 400nm/200μC/cm2. Patterned Al films were subsequently subjected to solid state reaction by dual stage annealing due to the melting temperature of Al thin films (660°C). The hillocks formation on Al films was minimized with an oxidation anneal at 450°C. Moreover, the little change in the morphology of Al patterns was observed after annealing at 450°C. The SEM and AFM results show the patterns were retained on sapphire substrates after high temperature annealing at less than 1200°C. The XRD and Raman results reveal that the composition and orientation of island patterns prepared by solid state reaction for 24h at 450°C, and 1h 1000°C were the same as that of the sapphire (0001) substrates. [ABSTRACT FROM AUTHOR]

Abstract: ZnO thin films were prepared on sapphire (0001) substrates by the dip-coating sol–gel technique. Then, ZnO thin films with thicknesses of 50nm, 150nm, 250nm, and 350nm were annealed at 800°C and with thickness of 250nm were annealed at 600°C, 700°C, 800°C, and 900°C, respectively. The effect of film thickness and annealing temperature on the structure and optical properties of sol–gel ZnO thin films on sapphire substrates were investigated by XRD, SEM, RT-PL. All the sol–gel ZnO thin films show polycrystalline hexagonal wurtzite structure and a high preferential c-axis orientation. The XRD and SEM results show that the better structural quality, high c-axis preferred orientation, uniform, compact sol–gel ZnO thin films 250nm thick were obtained when annealed at 700°C in air. Room-temperature PL spectrum of sol–gel ZnO thin films can be divided into the UV emission and the visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the visible broadband emission can be ascribed to the deep level emissions (DLE). The visible emission is suppressed with the annealing temperature of 600–700°C. By analyzing our experimental results, we concluded that the deep-level emission corresponds to oxygen vacancies (V O ). The biggest ratio of the PL intensity of UV emission to that of visible emission (I NBE/I DLE) is observed from sol–gel ZnO thin films 250nm thick annealed at 700°C. Therefore, we suggest that film thickness of 250nm and annealing temperature of 700°C are the most suitable conditions for obtaining high quality, high c-axis preferred orientation, uniform, compact sol–gel ZnO thin films with good luminescence performance. [Copyright &y& Elsevier]

Abstract: ZnO thin films were epitaxially grown on sapphire (0001) substrates by radio frequency magnetron sputtering. ZnO thin films were then annealed at different temperatures in air and in various atmospheres at 800°C, respectively. The effect of the annealing temperature and annealing atmosphere on the structure and optical properties of ZnO thin films are investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL). A strong (002) diffraction peak of all ZnO thin films shows a polycrystalline hexagonal wurtzite structure and high preferential c-axis orientation. XRD and AFM results reveal that the better structural quality, relatively smaller tensile stress, smooth, uniform of ZnO thin films were obtained when annealed at 800°C in N2. Room temperature PL spectrum can be divided into the UV emission and the Visible broad band emission. The UV emission can be attributed to the near band edge emission (NBE) and the Visible broad band emission can be ascribed to the deep level emissions (DLE). By analyzing our experimental results, we recommend that the deep-level emission correspond to oxygen vacancy (VO) and interstitial oxygen (Oi). The biggest ratio of the PL intensity of UV emission to that of visible emission (I NBE/I DLE) is observed from ZnO thin films annealed at 800°C in N2. Therefore, we suggest that annealing temperature of 800°C and annealing atmosphere of N2 are the most suitable annealing conditions for obtaining high quality ZnO thin films with good luminescence performance. [Copyright &y& Elsevier]

Two luminescent metal-organic frameworks (LMOFs), namely, [Cd2(DDCPB)·(DMF)2·H2O]n (CHD-1) and [Zn2(DDCPB)·(DMA)2]n·n(DMA) (CHD-2), were solvothermally constructed, which present structural diversity. Single crystal X-ray diffraction analysis indicates that they consist of [Cd2(μ2-O)2(κ-O)2] building units (for CHD-1), [Zn2(κ-O)6] building units (for CHD-2), which are further linked by multicarboxylate H4DDCPB to construct microporous frameworks. Remarkably, both CHD-1 and 2 exhibit highly efficient luminescent sensing for environmentally relevant Cu2+ ions through luminescence quenching. Theoretical and experimental calculations indicate that the luminescent quenching can be attributes to the donor-acceptor electron transfer between the MOFs and analytes. This work indicates that CHD-1 and 2 could be taken as a potential candidate for developing multifunctional luminescence sensors. [ABSTRACT FROM AUTHOR]

1T-TiSe 2 is a model transition metal dichalcogenide material that develops charge density waves (CDWs). Here we present variable-temperature Raman spectroscopy study on both CDW and optical phonon modes of 1T-TiSe 2 thin layers exfoliated onto SiO 2 substrate. Raman scattering intensities of all modes reach a maximum when the sample thickness is about 12 nm. This phenomenon can be explained by optical interference effect between the sample and the substrate. The CDW amplitude modes experience redshift and broadening as temperature increases. We extract CDW transition temperature ( T CDW ) from temperature dependence of the frequency of A 1 g CDW mode. We find that T CDW decreases in thinner flakes, which could be due to extrinsic effects. [ABSTRACT FROM AUTHOR]

Based on the N-donor auxiliary ligand effect, two new Ni(II) coordination polymers [Ni 2 (HL) 2 (bpe) 2 ] ( 1 ) and [Ni(HL)(bipy)(H 2 O) 2 ] ( 2 ) [H 3 L = 2-(4′-carboxyphenyl)terephthalic acid; bpe = 1,2-bis(4-pyridyl)ethane; bipy = 4,4′-bipyridine] have been successfully synthesized and characterized by single-crystal X-ray diffraction study, elemental analysis, IR spectra, TGA and powder X-ray diffraction (PXRD). This work presents a comparative study on the tuning of structural topologies by using two N-donor ligands with different lengths as auxiliary ligands. The structural determination reveals that complex 1 , incorporating bpe ligands, features a three-dimensional (3D) 4-connected 4-fold dia interpenetrating architecture with the point symbol of 6 6 , while 2 , containing bipy ligands, exhibits a two-dimensional (2D) sql layer structure with a 4-connected (4 4 ·6 2 ) topology. Moreover, the magnetic properties for 1 and 2 were also measured and compared on account of their different structures. [ABSTRACT FROM AUTHOR]

A new one-dimensional (1D) 4d–4f heterometallic coordination polymer [ErAg(Himdc)2(H2O)3] (1) (H3imdc=4,5-imidazoledicarboxylic acid) is synthesized under hydrothermal condition and characterized by elemental analysis, IR, PXRD and single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic space group P-1, showing a 1D metal–organic pseudo-nanotube with a 4.014×12.027Å2 cross-section. Furthermore, it assembles into a 3D supramolecular architecture via hydrogen bonds between pseudo-nanotubes. The complex 1 exhibits solid-state photoluminescence and high thermal stability. [ABSTRACT FROM AUTHOR]

Three new complexes, {[Mn(dtb)(bpe)·2H2O]·H2O}n(1), {[Mn(dtb)(bpa)·2H2O]·H2O}n(2), and {[Mn(dtb)(phen)]}n(3) [H2dtb = 5,5′-dithiobis(2-nitrobenzoic acid), bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bi(4-pyridyl)ethane, phen = 1,10-phenanthroline], have been synthesized under hydrothermal conditions with Mn(OAc)2·4H2O, dtb, and differentN-donor ligands. X-ray structure analyses of1and2reveal analogous structures with 1D helical chains and 2D 44chiral layers. The structure of3shows a 1D chain which is outwardly decorated with phen ligands. These neutral polymeric complexes exhibit structural diversity due to the different coordination modes of the flexible dtb ligand and the N-donor ligands. The thermogravimetric analyses and X-ray powder diffractions of1–3are also presented. [ABSTRACT FROM AUTHOR]

Abstract: A new coordination compound [Ag(Hcpob)(bpy)]n (1) was assembled by 4-(3′-carboxylphenoxy)benzoic acid (H2cpob), 4,4′-bipyridine (bpy) and AgNO3 under the hydrothermal synthesis. Especially, H2cpob came from the in situ decarboxylation of 4-(2′,3′-dicarboxylphenoxy)benzoic acid (H3dpob) in the hydrothermal reaction. Single-crystal X-ray diffraction reveals that 1 crystallizes in a monoclinic P21/c space group. 1 displays a one-dimensional (1D) fishbone-like double chain structure constructed from Ag(I) ions, bpy ligands and partly deprotonated H2dpob ligands, which further form a three-dimensional (3D) supramolecular architecture via π–π stacking and hydrogen-bonding interactions. In addition, the photoluminescence of 1 has been investigated in detail. [Copyright &y& Elsevier]

A new coordination polymer, {[Ag(H3bptc)(bpe)] · 2H2O} n (1) (H4bptc = 3,3′,4,4′-benzophenonetetracarboxylic acid, bpe = 1,2-bis(4-pyridyl)ethene), has been synthesized through a hydrothermal technique and structurally characterized. The crystal structure of 1 exhibits a 2-D hydrogen-bonding sheet between H3bptc− and two free water molecules. Fluorescent property, TG analysis, and X-ray powder diffraction for 1 were also measured and discussed. [ABSTRACT FROM AUTHOR]