Xue-Mei Liu

Synthesis of mesoporous Bi2WO6 architectures and their gas sensitivity to ethanol

Uniform hierarchical multilayered Bi2WO6 architectures were synthesized by a facile template-free hydrothermal process, and their synthesis conditions and formation mechanism were carefully investigated. XRD, XPS, FE-SEM, and HR-TEM techniques were employed to determine their phase composition, morphology and microstructure. Nitrogen adsorption and desorption isotherms were conducted to examine the specific surface area and the pore nature of the as-prepared sample. The results show that the as-prepared Bi2WO6 architectures consist of secondary nanoplates and have a mesoporous nest-like morphology with a diameter of 3–4 μm, and have very large specific surface areas. The largest surface area of 47.72 m2 g−1 is achieved when synthesized at 190 °C for 2.0 h. Furthermore, the Bi2WO6 samples were fabricated into a gas sensor, and the experimental results showed that the samples exhibited high sensitivity and a fast response–recovery to ethanol gas at lower temperatures (300 °C). For 100 ppm ethanol, the sensitivity of the best sensor (GS2) was 34.6, which is about 3-fold higher than the reported mesoporous ZnO based gas sensor because its mesoporous structure provided a high surface-to-volume ratio and surface accessibility for the ethanol. A plausible enhancement gas responding mechanism of the nest-like Bi2WO6 sensors was also proposed based on the structure and response–recovery properties.

An unusual asymmetric polyoxomolybdate containing mixed-valence antimony and its derivatives: [Sb4VSb2IIIMo18O73(H2O)2]12- and {M(H2O)2[Sb4VSb2IIIMo18O73(H2O)2]2}22- (M = MnII, FeII, CuII or CoII).

A new type of heteropolyanion containing mixed-valence antimony, [Sb4(V)Sb2(III)Mo18O73(H2O)2](12-) (1a), and its four derivatives, {M(H2O)2[Sb4(V)Sb2(III)Mo18O73(H2O)2]2}(22-) (M = Mn(II), Fe(II), Cu(II), or Co(II)) (2a-5a), have been isolated as ammonium salt, and their structures were determined by single-crystal X-ray diffraction. The framework of the polyanion 1a displays a curious asymmetric structure, and there exist six types of Sb coordination environments and seven types of {MoO6} octahedra. The title compounds were also characterized by elemental analyses, IR, UV-vis, Raman spectra, and cyclic voltammogramms.

Syntheses, structures and magnetic properties of two heterometallic carbonates: K2Li[Cu(H2O)2Ru2(CO3)4X2]·5H2O (X = Cl, Br)

Self-assembly of Ru2(CO3)43− units and Cu2+ ions in the presence of halogen (Cl− or Br−) has resulted in two novel isomeric layered structural heterometallic carbonates, K2Li[Cu(H2O)2Ru2(CO3)4X2]·5H2O [X = Cl (1), Br (2)]. X-ray structural analysis reveals that complexes 1 and 2 contain a similar square-grid negative layer [Cu(H2O)2Ru2(CO3)4X2]n5n−, in which each Ru2(CO3)4X25− unit is linked by four Jahn–Teller distorted Cu(H2O)22+ ions in a cross mode and vice versa. The adjacent negative layers are connected by K–O, Li–O bonds, and hydrogen bonding, which led to the formation of a supramolecular 3D network structure. The two complexes show ferromagnetic coupling between the Ru2 dimer and the Cu2+ ion. Detailed magnetism measurement demonstrates that complex 1 exhibits soft magnetic ordering below 2.9 K coexistent with domain movement, and complex 2 shows long-range ferromagnetic ordering below 3.8 K.

Layer structural bimetallic metamagnets obtained from the aggregation of Ru2(CO3)43− and Co2+ in existence of halogen

An investigation of halogen (Cl− and Br−) influence on the self-assembling Ru2(CO3)43− paddle-wheel precursors and Co2+ ions in aqueous solution has resulted in two novel layer structural bimetallic carbonate complexes, [{Co(H2O)4}2Ru2(CO3)4(H2O)Cl]n·7.5nH2O (1), and [{Co(H2O)4}2Ru2(CO3)4(H2O)2]n·[{Co(H2O)4}2Ru2(CO3)4Br2]n·10.5nH2O (2). X-ray structural analysis reveals that complexes 1 and 2 contain similar square-grid layer structures, in which each Co(H2O)42+ bonds to two Ru2(CO3)43− units in a trans manner forming square-grid layer [{Co(H2O)4}2Ru2(CO3)4]nn+, and X− (Cl− and Br−) ions influence the packing diagram between neighboring layers. For complex 1, two axial positions of each Ru2(CO3)43− paddlewheel are terminated by H2O and Cl−, respectively, forming a neutral layer [{Co(H2O)4}2Ru2(CO3)4(H2O)Cl]n. Meanwhile in complex 2, the axial positions of each Ru2(CO3)43− in the layer [{Co(H2O)4}2Ru2(CO3)4]nn+ are terminated by two H2O or two Br−, forming two oppositely charge layers packing alternatively, namely, the positive layer [{Co(H2O)4}2Ru2(CO3)4(H2O)2]nn+ and negative layer [{Co(H2O)4}2Ru2(CO3)4Br2]nn−. These two complexes are metamagnets, showing magnetic ordering Tc = 5.1 K, TN = 2.6 K for 1, and Tc = 2.7 K, TN = 2.3 K for 2, and the metamagnetism transition fields are ~1.2 kOe and ~0.5 kOe K for 1 and 2, respectively.

Heterometallic Co(II)–Ru2(II,III) carbonates: from discrete ionic crystals to three-dimensional network

An investigation of the reaction conditions influence on the self-assembling of Ru2(CO3)43− paddle wheel precursors and Co2+ ions in aqueous solution has resulted in a series of Co–Ru2 hetero-metallic complexes with different composition and dimensionality, namely [K1/3{Co(H2O)6}4/3{Ru2(CO3)4(H2O)2}]·2H2O (1), [KCo(H2O)5Ru2(CO3)4]·5H2O (2), and [KCo(H2O)4Ru2(CO3)4]·H2O (3). These complexes exhibit dimensional diversity due to the various linking modes of Co2+ ions. X-Ray structural analysis reveals that complex 1 is composed of ionic crystals with the Ru2(CO3)43−:Co(H2O)62+:K+ ratio of 3:4:1. For complex 2, one water of each Co(H2O)62+ is substituted by one oxygen of Ru2(CO3)43− forming [Co(H2O)5Ru2(CO3)4]−, then the neighboring Ru2(CO3)43− units are connected to each other through the remaining two carbonate oxygen atoms forming a negative square-grid layer [Co(H2O)5Ru2(CO3)4]nn−. In complex 3, two water molecules of each Co(H2O)62+ are substituted by the oxygen atoms of Ru2(CO3)43− units, which are connected to each other forming the square-grid layer [Ru2(CO3)4]n3n− similar to that in 2, then Co(H2O)42+ ions bond to neighboring [Ru2(CO3)4]n3n− layers in a cis mode forming the three-dimensional network [Co(H2O)4Ru2(CO3)4]nn−. Complex 2 exhibits ferromagnetic coupling between Ru25+ and Co2+, and long-range ordering is observed below 5.0 K. In contrast, complex 3 with a 3-D sublattice displays spin-glass behavior with the coexistence of spin-canting with magnetic ordering at 4.7 K.

Structure and Magnetic Properties of Pyridine Coordinated Sandwich-type Heteropolyanion {[Na(H2O)2]3[Ni(C5H5N)]3(AsW9O33)2}9−

pyridine 协调了三明治类型 heteropolytungstate Na7 [Ni (H2O ) 6 ]{[Na (H2O ) 2 ] 3 [Ni (C5H5N )]3-(AsW9O33 ) 2 }