The photovoltaic performance of dye-sensitized solar cells enhanced by using Dawson-type heteropolyacid and heteropoly blue-TiO2 composite films as photoanode

Dawson-type heteropolyacid {P₂Mo₁₈^VI} and its two-electron heteropoly blue {P₂Mo₂^VMo₁₆^VI}-doped TiO₂ composites have been successfully prepared by a simple sol–gel method and introduced into the photoanode of dye-sensitized solar cells (DSSCs), which results in a significant performance enhancement of DSSCs. The electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) curve were employed to investigate the electron transport and carrier recombination behavior in DSSCs. The results show that doping with {P₂Mo₁₈^VI} and {P₂Mo₂^VMo₁₆^VI} could both suppress the dark current and increase the electron lifetime in DSSCs. The performance of DSSCs with both {P₂Mo₁₈^VI}-doped and {P₂Mo₂^VMo₁₆^VI}-doped photoanodes is better than that with pure P25 photoanodes and the overall conversion efficiency was improved by 24.48% and 17.19%, respectively.     

A novel oxidation state Keggin-type isopolyoxomolybdate (C3H5N2)4H[MoVI0.5MoVI12O40]: Synthesis,structural characterization and electrocatalytic properties

A new oxidation state Keggin-type isopolyoxomolybdate, (C₃H₅N₂)₄H[Mo^VI_0.5Mo^VI₁₂O₄₀]·H₂O (1), was synthesized and structurally characterized by single crystal X-ray crystallography, spectroscopy, and further characterized by IR spectroscopy, UV–vis spectra, ESI-MS and thermogravimetric analysis. All the Mo atoms in the [[Mo^VI_0.5Mo^VI₁₂O₄₀]]^5 − anion are Mo^6 +, which was confirmed by the X-ray photoelectron spectroscopy(XPS), bond valence sum (BVS), and UV–vis spectra. Electrospray ionization mass spectrometry (ESI-MS) results suggest that {Mo₁₂O₄₀} and {Mo₁₃O₄₀} fragments coexist in compound 1. Compound 1 demonstrated good electrocatalytic activity for nitrite and hydrogen peroxide reduction.     

Two novel 3D bimetallic oxide framework with 16-membered wheel clusters based on {Mo5O16} ribbon-like chains

Two hybrid compounds based on {Mo₅O₁₆} ribbon-like chains, [M(3-pt)₂(Mo₅O₁₆)]·H₂O (M = Co, Mn) (1 and 2) {3-pt = 5-(3-pyridyl)-tetrazole}, have been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Three-dimensional Mo/O/M^II/tetrazole frameworks of the title compounds are constructed from 1D infinite ribbon-like [Mo₅O₁₆]²⁻ chains covalently linked through [M(3-ptz)]²⁺ fragments via OM and NMo coordinate bonds. It is noteworthy that the isostructural compounds contain an unprecedented 3D bimetallic oxide network with 16-membered wheel clusters in which two parallel interdigitated stacks of 3-pt ligands are trapped. Remarkably, the title complexes represent the first two examples of the solid materials containing {Mo₅O₁₆} ribbon-like chains.     

Electrochemical characterization of self-assembly process of nano-scaled polyoxomolybdate (NH4)42[Mo72Mo60O372(CH3COO)30(H2O)72]·ca.300H2O

Cyclic voltammetry and electrochemical admittance were used to characterize the self-assembly process of nano-scaled spheres of polyoxomolybdate (NH₄)₄₂[Mo^VI₇₂Mo^V₆₀O₃₇₂(CH₃COO)₃₀(H₂O)₇₂]·ca.300H₂O·ca.10CH₃COONH₄) or {Mo₁₃₂}. Cyclic voltammetry indicated that the self-assembly process could be detected after 8 h and completed after one day. Electrochemical admittance showed that the molybdenum species in the CH₃COONH₄-CH₃COOH buffer (pH 4.46) were totally different from those in the pure (NH₄)₆Mo₇O₂₄ solution (pH 5.54) and the (NH₄)₆Mo₇O₂₄ solution (pH 4.21) acidified by hydrochloric acid. However, the molybdate species in the latter two solutions should be mixtures of non-protonated and/or protonated [Mo₇O₂₄]⁶⁻ and [Mo₈O₂₆]⁴⁻ anions. Detailed analysis of admittance results could support the existence of the molybdate species related to the {Mo^VI₆} fragment which was one of the components of {Mo₁₃₂} clusters. Admittance results on the self-assembly process were coincident with those from cyclic voltammetry.     

A novel 2, 6-connected inorganic-organic 3-D open framework based on {As2Mo18} with photocatalytic property and anticancer activity

A new inorganic-organic open framework based on Wells-Dawson arsenomolybdate, {Ag(diz)₂}₃[{Ag(diz)₂}₃(As₂Mo₁₈O₆₂)]∙H₂O (1) (diz = 1,2-diazole) has been hydrothermally synthesized and characterized by elemental analysis, IR, TG, UV, XRD, and single-crystal X-ray diffraction. In compound 1, each {As₂Mo₁₈} cluster uses six terminal oxygen atoms on 'equator' position to attract peripheral six {Ag(diz)₂} linkers, which are further connected by six Dawson clusters located on two different planes via unique equator-to-equator interlaced ways to form a unprecedented 3D network with {8¹² ∙ 12³}{8}₃ topology. Compound 1 represents the highest covalent connectivity of 3-D Dawson arsenomolybdate, which exhibits merit photocatalytic properties for degradation of refractory dyes Azon Phloxine (AP) under UV light. In addition, compound 1 has a potent inhibition effect on proliferation of Human gastric adenocarcinoma cells (SGC-7901).     

A new rhombic 2D interpenetrated organic-inorganic hybrid material base on [HxAs2Mo6O26](6 − x)− polyoxoanion and Co-btb complexes

The new compound based on unconventional arsenomolybdate: {Co(btb)(H₂O)₂}₂{H₂As₂Mo₆O₂₆}·2H₂O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) (1) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, elemental analyses, IR, XPS, UV–vis-NIR and TG. Compound 1 consists of [H₂As₂Mo₆O₂₆]^4 − polyoxoanion and {Co-btb} complexes, the polyoxoanion as a tetradentate node coordinated with the Co^2 + ions forming the rhombic 2D interpenetrated layer structure, which is further extended the 3D topological structure with symbol {4⁶ · 6² · 8¹⁶ · 12⁴}{4⁹ · 6⁶}²{4}² by weak interaction. It shows obvious photocatalytic activities for the degradation of methylene blue (MB) and rhodamine-B (RhB). In addition, the electrocatalytic activity upon the reduction of nitrite also has been studied.     

Self‐Assembly of A Novel Ag48 Cluster Encapsulating an Unprecedented [Mo8O28]8− Anion Template

A novel silver cluster ( SD/Ag48a ) co‐protected by p‐MePhS^? and CF₃COO^? ligands with an in‐situ generated unprecedented [Mo₈O₂₈]^8? template has been synthesized under solvothermal condition. Single‐crystal X‐ray diffraction (SCXRD) and electrospray mass spectrometry (ESI‐MS) were used to determine the atom‐precise structure and solution behavior, respectively. Interestingly, the rare [Mo₈O₂₈]^8? ion observed in the center of SD/Ag48a consists of 8 edge‐shared {MoO₆} octahedra or can be deemed as three {Mo₄O₄} cubes fused together by sharing faces. The UV‐Vis spetcrum exhibits that a high‐energy (HE) wide absorption centered at ca. 365 nm, which can be assinged to intraligand (IL) π→π* transition absorption, whereas the low‐energy (LE) shoulder peak centered at ca. 500 nm can be ascribed to ligand‐to‐metal‐charge‐transfer (LMCT, S 3p→Ag 5 s) transition.     

Hydrothermal synthesis,structure and properties of two new phosphomolybdates based on Strandberg-type {P2Mo5O23}6 − building units

Two inorganic–organic hybrid compounds based on Strandberg-type phosphomolybdates (abbreviated as {P₂Mo₅O₂₃}^6 −) complexes [H₃O]₂[Cu₂(Pyim)₂(H₂O)₃][P₂Mo₅O₂₃] · 6H₂O (1) and [Cu₃(Pyim)₃(H₂O)₄][P₂Mo₅O₂₃] · 7H₂O (2) were successfully synthesized at different pH values under hydrothermal conditions. Both 1 and 2 are based on the {P₂Mo₅O₂₃}^6 − clusters connected by copper complexes to generate one dimensional chain. The magnetic analyses of compounds 1 and 2 indicate antiferromagnetic interactions between copper ions.     

Two Keggin polyoxoanion-based hybrids composed of CuI/tbz segments: Syntheses,structures and electrochemical properties

Two Keggin polyoxoanion-based hybrid compounds composed of Cu^I/tbz segments [Cu^I₂(tbz)₂][Cu^I(tbz)₂(PMo^VI₁₀Mo₂^VO₄₀Cu^I₂)] (1) and [Cu^I₂(tbz)₃][Cu^I (tbz)₂](PW₁₂O₄₀) (2), have been hydrothermally synthesized. In compound 1, a 3D supramolecular framework with 2D channels is constructed from a novel cap-to-cap {Cu^I(tbz)₂(PMo^VI₁₀Mo₂^VO₄₀Cu^I₂)}^2 −_n chain via hydrogen bonding and π–π interactions, in which {Cu^I₂(tbz)₂}^2 + segments are incorporated. Compound 2 is composed of one discrete PW₁₂ polyoxoanion, one {Cu^I(tbz)₂}⁺ segment and one {Cu^I₂(tbz)₃}^2 + segment, displaying a 3D supramolecular structure through hydrogen bonding and π–π interactions. The results indicate that the polyoxoanions and configurations of tbz ligand play the key roles in the self-assembly processes. The electrochemical properties of compounds 1 and 2 have been investigated.     

Polyoxometalate-cucurbituril molecular solid as photocatalyst for dye degradation under visible light

An organic-inorganic hybrid molecular solid based on Lindqvist-type polyoxometalate (POM) anions, {W₆O₁₉}^2 −, and decamethylcucurbit[5]uril (Me₁₀CB[5]) was synthesized under hydrothermal condition. In the structure of {[Na₂(W₆O₁₉)(Me₁₀CB[5])(H₂O)]·2H₂O}_n (complex 1), the sodium cations, {W₆O₁₉}^2 − anions, and Me₁₀CB[5] macrocycles formed a 1D chain subunit that assembled into a 3D supramolecular host-guest network through extensive supramolecular interactions. Furthermore, the complex displayed enhanced photocatalytic activity towards the degradation of rhodamine B (RhB) in water under visible light irradiation.     

A multifunctional reduced molybdophosphate-based 3D metal–organic framework induced by a rigid triazole and a flexible bis(triazole) mixed ligand

A novel reduced molybdophosphate-based metal–organic framework (MOF) Zn[(MoO₂)₆(HPO₄)₂(PO₄)₂(OH)₃]₂[Zn₂(L¹)][Zn(HL²)₂]₂·10H₂O (1) (L¹ = 1,6-bis(1,2,4-triazol-1-yl)hexane, L² = 1,2,4-triazol) has been hydrothermally synthesized and structurally characterized. Compound 1 is constructed from the [Zn(P₄Mo₆)₂]-based 2D layer and μ₂-bridging L¹ ligands, which shows a (2,3,8)-connected three-dimensional framework with {{4·6²}2{4⁴·6²·8¹⁸·12⁴}{4}²} topology. 1 represents the first 3D P₄Mo₆-based MOF constructed by mixed N-donor ligands. The electrocatalytic and photocatalytic activities of compound 1 have been investigated.     

Polyoxometalate chain-like polymer: the synthesis and crystal structure of a 1D compound, [Mo36O108(NO)4(MoO)2La2(H2O)28]n·56nH2O

Reaction of {Mo₃₆(NO)₄} with LaCl₃ in the presence of NH₂OH·HCl results in the formation of a novel chain-like polymer, [Mo₃₆O₁₀₈(NO)₄(MoO)₂La₂(H₂O)₂₈]_n·56nH₂O, in which the {Mo₃₆(NO)₄} units are linked to each other by two parallel La atoms.     

Hydrothermal synthesis,crystal structure and electrochemical behavior of two new isomorphic layered vanadates: [M(dpa)V3O8.5] (M = Cu(II) 1 and Zn(II) 2; dpa = 2,2′-dipyridylamine)

Two new isomorphic vanadates, [M(dpa)V₃O_8.5] (M = Cu²⁺ 1, Zn²⁺ 2; dpa = 2,2′-dipyridylamine) have been synthesized hydrothermally. X-ray crystal analysis reveals that vanadates 1 and 2 exhibit a layered structure constructed from {V₃O_8.5}^2? layers inlaid with [M(dpa)]²⁺ subunits. The {V₃O_8.5}^2? layers consist of ribbon-like chains of edge sharing {VO₅} square pyramids bridged through {V₂O₇} fragments. Electrochemical measurement shows that lithium ions are reversibly intercalated and deintercalated in vanadate 1.     

Organic–inorganic hybrid supramolecular assembly through the highest connectivity of a Wells–Dawson molybdoarsenate

An unusual supramolecular hybrid material based on the Dawson molybdoarsenate, (H₂bimyb)₃(As₂Mo₁₈O₆₂) (1) (bimyb = 1,4-Bis(imidazol-l-ylmethyl) benze) has been hydrothermally synthesized and characterized by elemental analysis, IR, TG, UV, XRD, and single-crystal X-ray diffraction. In compound 1, the {As₂Mo₁₈O₆₂} cluster uses its surface oxygen atoms to attract 14 bimyb ligands, which are further surrounded by 22 Dawson polyanions via strong supramolecular interactions to form close-packed 3D supramolecular networks with a (14⁹¹)(5¹⁰)(4⁶) topology structure. Compound 1 represents the highest connectivity of Dawson molybdoarsenate. In addition, compound 1 exhibits bifunctional electrocatalytic behaviors for oxidation of ascorbic acid (AA) and reduction of hydrogen peroxide (H₂O₂), as well as high-efficient degradation ability for typical dye MB under UV light.     

Organic–inorganic hybrid oxides: Structure and magnetic properties of [{Cu(terpy)}2Mo6O17(H2O)(O3PCH2NH2CH2PO3)2] · H2O,a bimetallic oxide constructed from novel {Mo6O17(H2O)(O3PCH2NH2CH2PO3)2}4− clusters

The hydrothermal reaction of MoO₃, CuSO₄ · 5H₂O, 2,2′:6′:2″-terpyridine (terpy) and bis-N,N-(methylphosphonic acid) amine (H₂O₃PCH₂NHCH₂PO₃H₂) provided blue crystals of the bimetallic oxide [{Cu(terpy)}₂Mo₆O₁₇(H₂O)(O₃PCH₂NH₂CH₂PO₃)₂] · H₂O (1 · H₂O). The three-dimensional structure of 1 is constructed from {Mo₆O₁₇(H₂O)(O₃PCH₂NH₂CH₂PO₃)₂}⁴⁻ clusters linked through {Cu(terpy)}²⁺ subunits. The cluster consists of three pairs of edge-sharing {MoO₆} octahedra linked through corner-sharing interactions into a {Mo₆O₆} ring. One phosphonate ligand spans the diameter of the ring, bridging four molybdenum sites and leaving at a pendant {PO} group at each terminus. The second diphosphonate ligand exploits one {–PO₃} unit to cap the hexamolybdate ring and bridge all six molybdenum sites while the second {–PO₃} terminus bridges two molybdenum sites, leaving a pendant {PO} unit. Crystal data: C₃₄H₄₅Cu₂Mo₆N₈O₃₅P₄: monoclinic, P2₁/n, a = 11.9431(7) Å, b = 17.382(1) Å, c = 27.524(2) Å, β = 90.429(1)°, V = 5713.7(6) Å³, Z = 4, D_calc = 2.270 g cm⁻³, R₁ = 0.0466.     

Degradation of color photographic waste fix solution by anodic oxidation

By use of a capillary electrophoretic method for anion analysis the anodic oxidation of thiosulfate, present in color photo bleach‐fix solutions, was investigated. In a specially constructed electrolysis cell with a cation‐exchange membrane separating the electrode chambers and with a carbon flow‐through three‐dimensional anode the two‐stage anodic oxidation of S₂O₃^2? anions was realized. In the first stage, S₂O₃^2? anions were oxidized to a maximal degree to an intermediate compound – tetrathionate (S₄O₆^2?) – then S₄O₆^2? anions were oxidized to the sulfate (SO₄^2?), avoiding the decomposition of intermediate compounds and the formation of harmful sulfur compounds. © 2002 Society of Chemical Industry     

Ionothermal synthesis and characterization of alkali metal polyoxometallates: Structural trends in the (emim)m[An(Mo8O26)] (emim = 1-ethyl-3-methylimidazolium; m = 2,3; n = 1,2; A = K,Rb, Cs) group of compounds

Three novel octamolybdates (emim)₃K(Mo₈O₂₆) (1), (emim)₃Rb(Mo₈O₂₆) (2) and (emim)₂Cs₂(Mo₈O₂₆) (3) (emim = 1-ethyl-3-methylimidazolium) have been prepared by ionothermal reactions using (emim)Br as a solvent. The structures contain octamolybdate anions [β-Mo₈O₂₆]^4–. In compounds 1 and 2, [β-Mo₈O₂₆]^4– units are linked by alkali metal cations to form 1D chain structures, while Cs cations in the compound 3 link to polyoxoanions to form a 2D layered structure.     

The synthesis and characterization of a new butterfly-like polyoxometalate: K5Na2[Mo9V3O38]·9H2O

A new butterfly-like compound K₅Na₂[Mo9V₃O₃₈]·9H₂O 1 has been synthesized in aqueous solution and characterized by elemental analysis, IR spectroscopy, TG analysis, UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammogram and single-crystal X-ray diffraction analysis. Compound 1 is a new butterfly-like molybdodivanadate composed by Mo (VI) and V (V) with the Mo/V ratio 3:1, the polyoxoanion [Mo₉V₃O₃₈ ]^7? can be described as two {MMo₄O₁₈} (M = Mo/V) units connected by one {V₂O₈} core. The photocatalyst property of compound 1 has been investigated, which shows a good photocatalyst for degradation of RhB.     

Extended architecture formed by linkage of a new type of decamolybdate {Mo10O34} unit and Cu3 cluster

A novel extended architecture based on unprecedented decamolybdate unit and Cu₃ cluster, (NH₄)_2n[Cu₃(atrz)₆Mo₁₀O₃₄]_n (1) (atrz = 4H-4-amino-1,2,4-triazole), has been synthesized under the hydrothermal conditions. The decamolybdate unit in 1 represents an unprecedented type {Mo₁₀O₃₄} skeleton and is composed of γ-octamolybdate subunit capped two {MoO₆} octahedra at corners by sharing three oxygen atoms. The capped {MoO₆} octahedra of decamolybdates and the external copper ions of the linear trinuclear cation [Cu₃(atrz)₆]^6 + further connect alternately to form a 1D chain. Magnetic measurement reveals the antiferromagnetic interactions among the Cu₃ cluster.     

Comparative electrochemical study of myoglobin loaded in different types of layer-by-layer assembly films

Four different types of layer-by-layer films were assembled on solid surfaces and designated as PDDA/{ZrO₂}_n, {PDDA/ZrO₂}_n, {PDDA/NP-ZrO₂}_n, and {PDDA/PSS}_n, where ZrO₂ stands for zirconia sol-gel formed by vapor-surface sol-gel deposition, NP-ZrO₂ represents ZrO₂ nanoparticles, PDDA is poly(diallyldimethylammonium), and PSS is poly(styrenesulfonate). When these films were immersed in myoglobin (Mb) solutions, Mb could be gradually “absorbed” or loaded into the films, and the Mb-loaded films at pyrolytic graphite (PG) electrodes demonstrated nearly reversible cyclic voltammetric (CV) responses for Mb Fe^III/Fe^II couple and good electrocatalytic property toward H₂O₂. The electrochemical and electrocatalytic activity of Mb in these films exhibited the sequence of PDDA/{ZrO₂}_n-Mb > {PDDA/ZrO₂}_n-Mb > {PDDA/NP-ZrO₂}_n-Mb > {PDDA/PSS}_n-Mb. Among the four types of films, PDDA/{ZrO₂}_n films, formed by repeated vapor-surface sol-gel deposition of ZrO₂ on PDDA surface, demonstrated better porosity and permeability, and thus could load more amounts of Mb from its solutions. Also because of the better porosity of PDDA/{ZrO₂}_n-Mb films, the small counterions in buffer solution could get into and out of the films more easily, also resulting in the better CV responses of the films according to the mechanism of electron hopping. UV-vis and FTIR spectroscopic studies suggest that Mb in these films essentially retains its native structure. The protein-loaded multilayer films are a novel kind of protein layer-by-layer films, which provide a new route to immobilize proteins and may provide a foundation for fabricating the third generation biosensors based on the direct electrochemistry of enzymes.