Hydrothermal Synthesis, Crystal Structure and Magnetic Property of a Novel Mixed Valence Decatungstate: [Cu(2,2′-bipy)_2]_2Na_2W_6~VW4^(VI)O_(30)·2H_2O

A novel Cu（II）-2,2＇-bipy-supported （bipy = bipyridine） mixed valence decatungstate, [Cu（2,2＇-bipy）2]2Na2W6^VW4^VIO30·2H2O 1, has been synthesized and structurally characterized by X-ray analysis. The crystal of 1 is of triclinic, space group P1^- with a= 10.9393（10）, b = 12.0492（2）, c = 12.3783（2）A, a = 80.631（10）, β= 70.226（10）, γ= 72.329（9）^o, V = 1459.64（4）A^3, Z = 1, Dc = 3.582 g/cm^3, F（000） = 1404, R = 0.0553 and wR = 0.1242 for 4607 observed reflections （I 〉 2σ（I））. The EPR spectrum of 1 indicates that its unpaired electrons are placed in the dx2-y2 orbital of the ground state of Cun. Furthermore, compound 1 shows an antiferromagnetic interaction.

Hydrothermal Synthesis and Structural Characterization of a Novel Mixed Valence Sodium Vanadium(Ⅳ,Ⅴ)Phosphate Na_(3.6)H_(1.4)P_(2)V_(5)O_(18)·11H_(2)O

A novel mixed valance vanadium phosphate Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O was synthesized by a hydrothermal method and its structure was characterized by X ray diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetric analysis. Na 3.6 H 1.4 P 2V 5O 18 ·11H 2O crystallizes in the cubic system with the cell parameter a =1.601(8) nm. The ratio of V( Ⅳ)/ V(Ⅴ) in the compound is 3.55.

Alternative lead-free mixed-valence double perovskites for high-efficiency photovoltaic applications

Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production.To overcome these limitations,researchers have proposed mixed-valence double perovskites,where Cs_(2)Au~ⅠAu~ⅢI_6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency.To further extend the scope of these lead-free materials,we varied the trivalent gold ion and halogen anion in Cs_(2)Au~ⅠAu~ⅢI_6,resulting in 18 new structures with unique properties.Further,using first-principles calculations and elimination criteria,we identified four materials with ideal band gaps,small effective carrier mass,and strong anisotropic optical properties.According to theoretical modeling,Cs_(2)AuSbCl_6,Cs_(2)AuInCl_6,and Cs_(2)AuBiCl_6 are potential candidates for solar cell absorbers,with a spectroscopic limited maximum efficiency(SLME) of approximately 30% in a 0.25 μm-thick film.These three compounds have not been previously reported,and therefore,our work provides new insights into potential materials for solar energy conversion.We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.

Recent research progress on mixed valence state tungsten based materials

Synthesis and characterization of tungsten based mixed valence state nanoparticles and their novel applications are reviewed.The mixed valence state tungsten based homogeneous nanomaterials such as bronze structure M_(x)WO_(3)(M=Na^(+),K^(+),Rb^(+),Cs^(+),NH_(4)^(+),etc.)and tungsten sub-oxide W_(18)O_(49) possess excellent infrared(IR)light shielding property,implying their great potential applications on heat ray shielding and indoor energy saving effect in summer season.Also,some novel properties such as electric conductivity,bio thermal therapy function and electrochromic properties of mixed valence state tungsten based materials are introduced.The design of components,formation of composites and structure control of thin films are expected to realize the property enhancement and candidates for practice application as window materials.The multifunc-tionality of the mixed valence state based composites also implies great potential on novel applications of various building materials.

Hydrothermal Synthesis and Structure of [CH3NH3]2[(VⅣO)2(VⅤO4)2]:A New Layered Mixed-valence Vanadium Oxide Incorporated with Organic Cations

A new layered mixed valence vanadium oxide, [CH 3NH 3] 2[(V ⅣO) 2(V ⅤO 4) 2], which contains interlamellar organic cations was prepared under hydrothermal conditions and its single crystal structure was determined. It crystallizes in a triclinic system with space group P 1, a =0 625 59(8) nm, b =0 639 84(9) nm, c =0 747 19(10) nm, α =78 718(2)°, β =80 099(2)°, γ =77 100(2). The compound contains mixed valence V 4+ /V 5+ vanadium oxide layers constructed from VO 4 tetrahedra, pairs of edge sharing VO 5 square pyramid and methylamine with protonated organic amines occupying the interlayer space.

Halogen Mediated Self-assembly of Three Mixed Valent Cu(Ⅰ)/Cu(Ⅱ)Complexes

Reaction of the ligand dmpt（dmpt=6,7-dimethylbenzo[f][1,10]phenanthroline）with CuCl2 afforded mixed valent Cu（Ⅰ）/Cu（Ⅱ） discrete tetranuclear complexes[Cu（Ⅱ）Cl2（dmpt）Cu（Ⅰ）Cl]（1）,while the reaction of ligand dppz（dppz = dipyrido[3,2-a：20,30-c]phenazine） with divalent halogen copper salt CuX2（X=Cl,Br） gave one-dimensional chain mixed valent Cu（Ⅰ）/Cu（Ⅱ） complexes [Cu（Ⅱ）Cl2（dppz）Cu（Ⅰ）Cl]n（2） and discrete mixed valent Cu（Ⅰ）/Cu（Ⅱ）complexes [Cu（Ⅱ）Br2（dppz）（DMF）Cu（Ⅰ）Br]（3）. Complex 2 consists of a one-dimensional chain-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-Cl-dppzC u（Ⅱ）-Clμ2-Cu（Ⅰ）-with Cu（Ⅱ） and Cu（Ⅰ） atoms linked together by chloride anion. Complex 3 is a discrete complex,which is the same as complexes 1 and 2 involving two different copper valent Cu（Ⅰ） and Cu（Ⅱ）. The Cu（Ⅰ） ion presents a pseudo-trihedral geometry,while the Cu（Ⅱ） ion presents a slightly distorted square-pyramidal geometry. This fact proved that halogen ions play a vital role in the assembly procedure. Our research results demonstrate the structural diversification that can be achieved by halogen ions mediated. Moreover,halogen ions-mediated self-assembly may provide useful information for further design of compounds with novel structures and properties.

Temperature-dependent Hydrothermal Synthesis of Two Distinct Three-dimensional Copper Complexes

Two distinct copper coordination polymers, namely [Cu^Ⅱ2（2,5-pydc）2（bpp）2]·H2O（1） and Cu2^ⅠCu^Ⅱ（2,5-pydc）2（bpp）2（2）（2,5-pydc = pyridine-2,5-dicarboxylic acid, bpp = 1,3-bi（4-pyridyl）propane）, have been successfully synthesized through hydrothermal conditions under different temperatures. Single-crystal X-ray structural analysis revealed that both complexes 1 and 2 are 3D frameworks. Complex 1 is an 8-connected 2-fold interpenetrating network based on [Cu（2,5-pydc）]4 molecular building block（MBB）, and also can be simplified as a 4-connected net if the Cu（Ⅱ） ion is regarded as an independent node, whereas 2 shows a（4,4）-connected non-interpenetrated framework which contains mixed valence Cu（Ⅰ/Ⅱ） centers. The results demonstrate that temperature plays a significant role in the final structures of the complexes.

Room Temperature Modulated Structure of Ca and K co-Doped LaMnO_3

A series of perovskite compounds of La1-x-yCaxKyMnO3 was prepared by hydrothermal disproportionation reaction of MnO2. The three oxidation states of manganese（Mn3＋, Mn4＋ and Mn5＋） can stably exist in the compounds. Under room temperature conditions, twice and three times modulated structure produced by the charge ordering can be observed by X-ray diffraction（XRD）, select area electron diffraction（SAED） and high resolution transmission electron microscopy（HR-TEM）. The splits of the diffraction peaks of the single crystals confirmed by synchrotron X-ray diffraction experiment are in accordance with those of the powder sample. The existence of the different oxidation states of Mn3＋, Mn4＋ and Mn5＋ can be considered to be the dominating reason of the complicated room temperature modulated structure.

Vibration uncoupling of germanium with different valence states lowers thermal conductivity of Cs2Ge3Ga6Se14

The thermal phonon transport is a key matter for heat managing in materials science which is crucial for device miniaturization and power density increase. Herein, we report the synthesis, structure and characterization of a new compound, Cs2Ge3Ga6Se14, with a unique anisotropic structure simultaneously containing Ge^3+ and Ge^2+ that adopt(Ge1)2^3+ Se6 dimer or(Ge2)^2+Se6 octahedron, respectively. The thermal conductivity was measured to be 0.57–0.48 W m^-1 K^-1 from 323 to 773 K, the lowest value among all the known Ge-containing compounds, approaching its glass limit according to the Cahill’s formulation. More importantly, we discover for the first time that the vibration uncoupling of Ge with different valence states hinders the effective thermal energy transport between the(Ge1)2^3+ Se6 dimer and(Ge2)^2+Se6 octahedron, and consequently lowers the thermal conductivity. In addition, we propose a structure factor f = sin(180) ×d/l(i =A, B)iGe Qi, with which a structure map of the Cs2 Ge3 M6 Q14 family is given.

Ag4Hg（SeO3）2（SeO4）: a novel SHG material created in mixed valent selenium oxides by in situ synthesis

Explorations of new second harmonic generation materials in Ag^+-Hg^2+/Bi^3+-selenites systems afforded three new silver selenium oxides, namely, Ag4 Hg(SeO3)2(SeO4)(1), Ag2Bi2(SeO3)3(SeO4)(2) and Ag5 Bi(SeO3)4(3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3 D open framework with 4-, 6-and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4(KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 e V respectively. Theoretical calculations disclose that compounds2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.

Wastewater treatment using Fe-doped perovskite manganites by photocatalytic degradation of methyl orange,crystal violet and indigo carmine dyes in tungsten bulb/sunlight

We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1 and 0.5) manganites and(ⅱ) efficient separation of photocatalysts from water using magnetic field.These ceramic photocatalysts were sintered at 1050℃ for 12 h.Ceramics were characterized by X-ray diffraction(XRD),soft X-ray absorption spectroscopy(SXAS),Fourier transform infrared spectroscopy(FTIR) and UV-visible diffuse reflectance spectroscopy(DRS).SXAS studies show the presence of Mn(Mn^(3+)/Mn^(4+)) and Fe(Fe^(3+)/Fe^(4+)) mixes valences in Fe-doped compositions.Optical band gap is found in visible light range for La_(0.7)Sr_(0.3)Mn_(1-x)Fe_(x)O_(3)(x=0.0,0.05,0.1) compositions.La_(0.7)Sr_(0.3)MnO_(3) degrades 94.6% methyl orange in7 min,81.9% crystal violet in 10 min and 99.1% indigo carmine in 5 min.La_(0.7)Sr_(0.3)Mn_(0.9)Fe_(0.1)O_(3) degrades the 92.6% methyl orange dye solution in 9 min,94.8% crystal violet in 25 min and 97.1% indigo carmine in3 min.Parent and Fe doped manganites can be separated in 60 s from wastewater.

Ceria Nanoparticles as Enzyme Mimetics

In the past decades, enzyme mimetics based on ceria nanoparticles （nanoceria） have been developed as potential substitutes for nature enzymes. The mixed valence states of cerium and the patterns of oxygen vacancies on crystal planes result in different enzyme mimetic activities. In this review we survey the bio-applications of nanoceria-based enzyme mimetics as well as the underlying mechanisms. Factors influencing the enzyme mimetic activities and future perspective of nanoceria-based enzyme mimetics are also addressed.

High-temperature synthesis and electronic bonding analysis of Ca-doped LaMnO_(3) rare-earth manganites

Doped lanthanum manganites La_(1-x)Ca_(x)MnO_(3) with five different concentrations of Ca(x=0.1,0.2,0.3,0.4 and 0.5) were synthesized by high-temperature solidstate reaction method and characterized.The prepared samples were experimentally analyzed by X-ray diffraction(XRD),ultraviolet-visible spectroscopy(UV-Vis),scanning electron microscopy/energy dispersive spectroscopy(SEM/EDS) and vibrating sample magnetometer(VSM)measurements.Orthorhombic structure is confirmed for this compound from powder X-ray diffraction data.The XRD data confirm the shrinkage in the unit cell of synthesized samples for increasing calcium concentration.The UV-Visible analysis for the estimation of optical band gap(E_(g)) reveals that the band gap decreases with the incorporation of Ca.The synthesized samples were investigated for charge density distribution using maximum entropy method,utilizing the XRD data sets.From the charge density analysis,it is found that the bond lengths for La-O and Mn-O bonds decrease with the addition of Ca.The ionic nature between La and O atoms and covalent nature between Mn and O atoms are enhanced for 40% of calcium-doping.For 50% of Ca-doped sample,ionic nature between La and O atoms and covalent nature between Mn and O atoms decrease.All the prepared samples exhibit ferromagnetism at 20 K and paramagnetism at 300 K.