Haijun Pang

Amperometric detection of nitrite based on Dawson-type vanodotungstophosphate and carbon nanotubes.

A nitrite sensor based on Dawson vanodotungstophosphates α2-K7P2VW17O62·18H2O (P2W17V) and carbon nanotubes (CNTs) was prepared by electrostatic layer-by-layer self-assembly technique. The sensor {PEI/PSS/[PDDA/P2W17V-CNTs]n} was characterized by UV-vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS). The electron transfer and sensing ability of this sensor were explored using cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) technology. The results show that the incorporation of CNTs and P2W17V into the composite film endowed the modified electrode with fast transfer rate and high electrocatalytic activity towards oxidation of nitrite. This nitrite sensor with 10 bilayers has a broad linear range of 5×10(-8) to 2.13×10(-3)M, a low detection limit of 0.0367μM (SN(-1)=3), a high sensitivity of 0.35mA mM(-1) NO2(-), an excellent anti-interference property in the presence of other potential interfering species and a good stable. It was successfully employed for determination of nitrite in real towards.

Turn helical motifs from pair to single entangled double helixes in a cobalt-vanadate system via introduction of a V-shaped ligand.

Two novel helical compounds based on polyoxovanadates, [Co(H2O)2V2O6] (1) and [Co(bimb)V2O6] (2) (bimb = 1,3-bis(1-imidazoly)benzene), have been synthesized under identical hydrothermal conditions, providing two structurally different helical motifs due to introduction of a V-shaped bimb ligand in 2. Compound 1 possesses a pair of entanglement double helixes in a 3D inorganic framework, whereas compound 2 shows a single entangled double helix in a 3D inorganic-organic network owing to the influences of steric hindrance of ligands as well as coordination geometries of metal cations. The electrocatalytic and photocatalytic properties of 1 and 2 were also investigated in details.

Assembly of co-bimb-polyoxotungstate hybrids: from 1D chain to 3D framework influenced by the charge of Keggin anions

Two new inorganic–organic hybrid compounds: [Co(H2O)2(bimb)2]2[SiW12O40] (1) and [Co2(H2O)(bimb)4](HBW12O40)·H2O (2) (bimb = 1,3-bis(1-imidazoly)benzene), have been synthesized under the same hydrothermal conditions and characterized by single crystal X-ray diffraction, IR spectra, elemental analyses and powder X-ray diffraction. Structural analyses show that 1 displays a 1D polymeric chain, whereas 2 presents a complicated 3D self-penetrating framework. The distinct structural features of the two compounds suggest that the charge of the Keggin anions should play a significant role in the process of assembly. The electrochemical properties of 1 and 2 were investigated in detail.

Tuning the dimension of POM-based inorganic–organic hybrids from 3D self-penetrating framework to 1D poly-pendant chain via changing POM clusters and introducing secondary spacers

Through tuning the different polyoxometalate (POM) clusters and the secondary spacers, four new various dimensionality inorganic–organic hybrid compounds Cu5(pzta)6(H2O)2[Mo8O26] (1), Cu5(pzta)6(H2O)6[PW12O40]·(OH) (2), Cu4(pzta)2(bipy)(H2O)4(OH)2[Mo8O26]·2H2O (3) and [Cu2(pzta)2(bipy)2(H2O)2][HPW12O40]·8H2O (4) (pzta = 5-(2-pyrazinyl)tetrazole, bipy = 4,4′-bipyridine) have been synthesized under identical hydrothermal conditions. The four compounds were assembled from copper cations, N-donor ligands and POM clusters. Compound 1 displays a novel self-penetrating 3D framework. When the POM clusters were changed from β-[Mo8O26]4− (β-Mo8) to [PW12O40]3− (PW12), compound 2 was obtained, which is a 2D layer with square channels into which the tetradentate PW12 anions as templates are incorporated. Furthermore, by introducing second spacer bipy into the reaction system of 1 and 2, respectively, compounds 3 and 4 were obtained. 3 shows a 2D layer that consists of adjacent metal–organic chains fused together by six-connected β-Mo8 anions, and 4 exhibits a 1D poly-pendant chain constructed by dinuclear copper complexes and PW12 clusters. The distinct structural features of the four compounds suggest that different POM clusters and secondary spacers should have great effect on the structures of POM-based inorganic–organic hybrids. Additionally, the luminescent and electrochemical properties for 1–4 have been investigated.

A new 3D framework based on reduced Wells-Dawson arsenotungstates as eight-connected linkages

A new hybrid compound based on reduced Wells-Dawson arsenotungstates as eight-connected linkages, [Cu4(btb)6(H2O)2][As2WV2WVI16O62]·10H2O (1) (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) has been synthesized under hydrothermal conditions. Structural analysis shows that 1 displays a 3D POMOF structure consisting of two crystal distinct motifs: a 3D MOF architecture and an eight-connected As2W18 cluster. It is worth mentioning that the 3D MOF architecture possesses two kinds of channels (A and B). The eight-connected As2W18 clusters as guests occupy the B channels and are incorporated within the MOF to achieve a 3D POMOF architecture with a novel (32·42·52)(33·45·53·64)2(36·49·59·64) topology. In addition, the electrochemical studies show that 1 has good electrocatalytic activities toward reduction of both hydrogen peroxide and nitrite molecules ascribed to W-centers. The photocatalytic properties of 1 indicate that the title compound presents a good degradation activity and may be a potential photocatalyst for oxidative decomposition of methylene blue dye.

Two novel zipper-like compounds of the usual and bivanadyl capped Keggin clusters connected by propeller-shaped complexes

By choosing asymmetric L ligands (L = 1-(imidazol-1-yl)-4-(1,2,4-triazol-1-ylmethyl)benzene), Cu2+/Co2+ cations and Keggin clusters as starting materials, two new POM-based zipper-like compounds, {Cu(L)4[HPMo12O40]}·4H2O (1) and {[Co(L)4][HPMo8VV4O40(VIVO)2]} (2), have been hydrothermally synthesized and characterized by elemental analyses, single-crystal X-ray diffraction, XPS, powder X-ray diffraction, IR spectroscopy, and TG analyses. A structural feature of 1 and 2 is that there exists a 1D + 1D → 3D interdigitated architecture achieved using molecular zippers, in which overhanging mono-coordinated L arms act as teeth. Compound 2 shows bifunctional electrocatalytic activities toward not only reduction of normal iodated inorganic molecules (IO3−) ascribed to Mo-centers, but also oxidation of biological molecules such as ascorbic acid (AA) ascribed to V-centers.

An electrochromic composite film of Preyssler-type phosphotungstate decorated by AuNPs

A multilayer composite film containing Preyssler-type phosphotungstate K12.5Nal.5[NaP5W30O110]·l5H2O (P5W30) and Au particles (AuNPs) was fabricated by layer-by-layer assembly technology (LBL). The {[PEI/PSS-AuNPs/PEI/P5W30]n} composite film was characterized by scanning electronic microscopic (SEM), UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and cyclic voltammetry (CV) measurements. The electrochemical behavior of the films with and without AuNPs was investigated by cyclic voltammetry and electrochemical impedance spectra, and the composite film showed an enhanced electron transfer rate. The 6 bilayer AuNPs-free film performed color switching from transparent to blue, optical contrast of 10.4%, and an coloration efficiency of 6.99 cm(2) C(-1) at 600 nm. The 6 bilayer composite film displayed enhanced electrochromic performance with the color switching from claret-red to deeper purple, optical contrast of 27.3% and coloration efficiency of 18.52 cm(2) C(-1) at 550 nm due to the presence of AuNPs. The contribution of AuNPs gives valuable information for exploring new electrochromic materials.

“Pinwheel” subunit-directed polyoxometalate-based hybrid compound [Cu(bimb)2]2[β-Mo8O26] with both helixes and chiral layers

A new polyoxometalate-based hybrid compound, [Cu(bimb)2]2[β-Mo8O26] (1) (bimb = 1,3-bis(1-imidazoly)benzene), has been synthesized and characterized by single-crystal X-ray diffraction, IR spectrum, elemental analyses and powder X-ray diffraction. Structural analysis revealed that the structure of 1 consists of a pair of chiral “pinwheel” subunits, and that such “pinwheel” subunits direct the formation of enantiomorphous chiral layers, in which the left- and right-handed helical chains are arranged regularly along the [001] direction. To the best of our knowledge, compound 1 represents the first example of an octamolybdate-based compound with both chiral and helical structural features. In addition, a photocatalytic experiment indicated that the title compound presents good degradation activity and may be a potential photocatalyst to decompose the methylene blue dye.

Tuning the topology structures of polymolybdate-based hybrids from interpenetrated framework to interdigitated architecture via changing polymolybdate clusters

By introducing different polyoxomolybdates into a Cu–bimb system (bimb = 1,4-bis(imidazol-1-yl) benzene), three new polyoxomolybdate-based inorganic–organic hybrids with distinct architectures, [CuII(bimb)1.5(H2O)(β-Mo8O26)0.5] (1), (Hbimb)2[CuI(bimb)(PMo12O40)]·4H2O (2) and [CuI4(bimb)4(SiMo12O40)]·2H2O (3), have been synthesized under identical hydrothermal conditions and characterized by routine methods. Compound 1 displays an interesting 2-fold interpenetrated structure consisting of two identical layers. When the polyoxomolybdate clusters were changed from β-[Mo8O26]4− to [PMo12O40]3−, and [SiMo12O40]4−, compounds 2 and 3, respectively, were obtained. Compound 2 shows a highly opened three-dimensional framework, while compound 3 exhibits a three-dimensional interdigitated architecture. The different structural features of compounds 1–3 suggest that the influences of different polyoxometalate clusters on structure must play a key role in the process of assembling. Additionally, both the luminescent and electrochemical properties for 1–3 have been investigated.

Synthesis and structural characterization of 3d–4f heterometallic coordination polymers: from cluster to chain

Two new 3d–4f heterometallic coordination polymers, [MnIV2CeIV3O6Na(OAc)8(H2O)5](OH)·10H2O (1) and [MnIINdIII2Na2(OAc)8(H2O)6]·2(OH) (2) (OAc− = acetate), have been conventionally synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. In 1, three Ce4+ and two Mn4+ cations are bridged by OAc− and μ3-O2− bridges forming a pentanuclear 3d–4f heterometallic [MnIV2CeIV3O6(OAc)8(H2O)5] cluster, while in 2, two Nd3+ and one Mn2+ cations are linked by carboxylic bridge of OAc− anions giving a 1D 3d–4f heterometallic [MnIINdIII2(OAc)8(H2O)6] chain. Additionally, pentanuclear heterometallic [MnIV2CeIV3O6(OAc)8(H2O)5] clusters in 1 are further connected by Na+ cations to result in a 1D chain, whereas the 3d–4f heterometallic chains in 2 are linked by Na1–O–Na1 dimers into a 2D array. Moreover, the variable magnetic susceptibilities of 1 and 2 are investigated.