Simple method to rapidly fabricate chain-like carbon nanotube films and its field emission properties

A simple process to fabricate chain-like carbon nanotube （CNT） films by microwave plasma-enhanced chemical vapor deposition （MPCVD） was developed successfully. Prior to deposition, the Ti/Al2O3 substrates were ground with Fe-doped SiO2 powder. The nano-structure of the deposited films was analyzed by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and Raman spectroscopy. The field electron emission characteristics of the chain-like carbon nanotube films were measured under the vacuum of 10-5 Pa. The low turn-on field of 0.80 V/μm and the emission current density of 8.5 mA/cm2 at the electric field of 3.0 V/μm are obtained. Based on the above results, chain-like carbon nanotube films probably have important applications in cold cathode materials and electrode materials.

Synthesis, Crystal Structure and Photoluminescence of a Zn(Ⅱ) Coordination Polymer Derived from 1,1'-Biphenyl-2,2',6,6'-tetracarboxylic Acid

A new polymeric znic（II） coordination polymer, [Zn2（bptc）·（H2O）4]n·nC H3 OH 1, was synthesized by the hydrothermal reaction of Zn（NO3）2·6H2O with 1,1＇-biphenyl-2,2＇,6,6＇-tetracarboxylic acid（H4bptc） and structurally characterized by single-crystal diffraction, IR and elemental analysis. The polymer crystallizes in the orthorhombic system, space group Pnna with a = 13.411（1）, b = 16.418（2）, c = 9.178（7）, V = 2025.2（3） 3, Z = 4, C17H14O13Zn2, Mr = 557.06, Dc = 1.827 g/cm3, F（000） = 1120, μ（MoK α） = 2.439 mm-1. The final R and wR are 0.0548 and 0.1691 for 1279 observed reflections with I 2（I）. In this compound, the bptc4- anion adopts monodentate bridging coordination modes connecting the zinc（II） ions to form a 1D chain structure, which furnishes a 2D supramolecular architecture through hydrogen bonding interactions formed by carboxylic oxygen atoms of bpdc, oxygen atoms of crystalline methanol and water molecules. Complex 1 displays an emissive maximum at 435 nm in the solid state at room temperature.

Synthesis,Crystal Structure and Properties of a 3-Fold Interpenetrating 3D Cd(Ⅱ)Complex Derived from 4-(2-Methyl-1H-imidazol-1-yl)benzoic Acid

A new Cd~Ⅱ coordination complex,namely [Cd（iba）_2]_n（1）,was prepared by the hydrothermal reaction of Cd（NO_3）_2·4H_2O with 4-imidazol-1-yl-benzoic acid（Hiba）. Single-crystal X-ray diffraction analysis shows that compound 1 crystallizes in monoclinic system,space group Cc with a = 11.403（4）,b = 30.480（9）,c = 7.732（3） ？,β = 130.189（4）o,V = 2503.0（1） ？~3,Z = 4,C_（22）H_（18）CdN_4O_4,Mr = 514.80,Dc = 1.666 g/cm^3,F（000） = 1032 and μ（Mo Kα） = 1.101 mm-1. The final R and wR are 0.0573 and 0.1823 for 4421 observed reflections with I 〉 2σ（I）. Each iba-ligand coordinates in a bidentate fashion,connecting the Cd（Ⅱ） atoms to form a 2D wave-shape layer structure,which can be simplified as a four-connected topological net. Interestingly,the 2D layers are further extended into a 3-fold interpenetrating 3D architecture. Compound 1 displays an emissive maximum at 455 nm in the solid state at room temperature and a response of the second harmonic generation（SHG） activity is approximately 0.8 times that of KDP.

Synthesis, Structure and Magnetic Properties of a 3D Interpentrating Network Based on 4-Imidazol-1-yl-benzoic Acid and Azide Ligands

A new CoⅡ coordination complex, namely [Co（iba）（N3）]n, was prepared by the hydrothermal reaction of Co（NO3）2·6H2O with Na N3 in the presence of 4-imidazol-1-yl-benzoic acid（Hiba）. Compound 1 crystallizes in orthorhombic, space group Pbca with a = 6.782（2）, b = 19.93（5）, c = 15.96（4） A, V = 2157.2（3） A3, Z = 8, C10H7O2N5 Co, Mr = 228.14, Dc = 1.774 g/cm^3, F（000） = 1160, μ（Mo Kα） = 1.592 mm-1. The final R and w R are 0.0706 and 0.1990 for 1160 observed reflections with I 2σ（I）. Each iba- coordinates in a bidentate fashion with two CoⅡ ions and every two adjacent CoⅡ ions were connected by one azido ion to form a 3D two-fold interpenetrating framework. Thermogravimeteric analysis（TGA） of compound 1 reveals that the loss of moiety of azido ion occurs from 200 oC to about 260 oC and the framework begins to decompose above 300 oC. The magnetic property investigation of compound 1 demonstrates that it displays ferromagnetic coupling between CoⅡ ions.

Self-assembly of a Mixed-valence Cu(Ⅰ)/Cu(Ⅱ)Coordination Polymer Derived from a Conformationally Flexible Tripodal Phosphoric Trimide Ligand

Reaction of a tripodal ligand, N,N＇,N＇＇-tris（3-pyridinyl） phosphoric trimide（TPPA） and CuBr_2·2H_2O result in the assembly of a new polymeric copper coordination polymer, which was characterized by single-crystal diffraction, infrared spectroscopy and elemental analysis. The polymer crystallizes in the triclinic system, space group P1 with a = 9.0964（5）, b = 10.2592, c = 10.5822（8） A, V = 933.01（9） A3, Z = 2, C_（30）H_（24）Br_4Cu_3N_（12）O_2P_2, M_r = 985.02, D_c = 1.753 g/cm3, F（000） = 4072 and μ（MoKα） = 0.746 mm^（-1）. The final R and w R are 0.0588 and 0.1329 for 4260 observed reflections with I 〉 2σ（I）. Cu（Ⅰ） is tetrahedrally coordinated and Cu（Ⅱ） center adopts square planar coordination geometry. Because of the flexibility of the TPPA ligands, the pyridyl rings rotate though a certain angle and three pyridyl rings on the same TPPA rotate by about 45° with respect to the central P=O groups. TPPA ligand acts as a tridentate ligand and is coordinated with three metal centers with its pyridyl donors to form a 2D-sheet like structure, and it is further connected by N-H···O and N-H···Br, resulting in a 3D network packing. Oxidation states of the metal center have been determined by bond valence sum calculation.

Synthesis and Characterization of a Novel Grid Coordination Polymer Network Generated from Unsymmetrically Bridging Ligand

Self-assembly of pyta （pyta = N-（4-pyridylmethyl） triazole） with Ag（I） center by layer-separating diffusion method at ambient temperature gives rise to a new supramolecular [Ag（p-pyta）CIO4]n which has been characterized by single-crystal X-ray diffraction. The polymer crystallizes in a hexagonal space group R-3 with a = 22.456（7）, b = 22.456（7）, c = 14.570（1） A, V= 6363（6） A3, Z = 4, C36H36Ag4.5C14.5N18O18, Mr = 1653.77, Dc = 1.726 g/cm3, F（000） = 3240, μ（MoKa） = 1.625 mm^-1, the final R = 0.0449 and wR = 0.1397 for 2744 observed reflections with I〉2σ（I）.