CuSn(OH)6 submicrospheres: Room-temperature synthesis and weak antiferromagnetic behavior

CuSn(OH)₆ submicrospheres with a diameter of 400-900 nm, which are composed of nanoparticles with a size of about 27.8 nm, have been successfully synthesized for the first time via a simple liquid approach at room temperature in 15 min. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the products. Standard magnetization measurements at low temperature reveal that the as-obtained CuSn(OH)₆ submicrospheres are antiferromagnetic and have a weak spin-Peierls transition at about 78 K.     

Repeatable synthesis of Cu2O nanorods by a simple and novel reduction route

Cu₂O nanorods were synthesized by reducing bamboo leaf-shaped Cu(OH)₂ with sodium hypophosphite (NaH₂PO₂) in an H₂O/ethylene glycol (EG) mixing solution. The Cu(OH)₂ was prepared by adding an alkaline solution to an aqueous solution containing CuSO₄ and NaH₂PO₂ at room temperature. The optimum temperature range for the reduction of the Cu(OH)₂ to Cu₂O nanorods was 55-70 °C. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The result showed the prepared Cu₂O nanorods were uniform and had diameters of 10-20 nm and lengths of 150-200 nm. The synthesis is simple, inexpensive, and highly repeatable.     

Mild solvothermal synthesis of complex fluorides Li2BeF4 and LiSrAlF6

The complex fluorides Li₂BeF₄ and LiSrAlF₆ were synthesized solvothermally at 180–240 °C and characterized by means of X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). The different influence factors such as solvents, molar ratios of initial mixtures, reaction temperature and reaction time were investigated. The experimental results indicated that Li₂BeF₄ and LiSrAlF₆ powders could be controllably synthesized in the solvothermal process.     

亚微米级Cu3(BTC)2的合成、表征及应用研究

采用水/溶剂热法合成了铜的亚微米级有机金属框架Cu_3(BTC)_2,并用扫描电镜、透射电镜、X射线粉末衍射、傅里叶红外光谱仪及光电子能谱仪对材料的形貌结构及表面性质进行了分析。将制备的Cu_3(BTC)_2用于吸附去除水中亚甲基蓝(MB)污染物。吸附结果表明,MB在Cu_3(BTC)_2上的吸附符合Freundlich模型。当MB初始浓度为30mg/L时,平衡吸附量为29.5mg/g,当初始浓度提高到300mg/L时,平衡吸附量达到244.3mg/g,吸附效果优于文献中报道的大部分吸附材料。     

Photoluminescence and Raman study of Cu2ZnSn(SexS1 − x)4 monograins for photovoltaic applications

The quaternary semiconductors Cu₂ZnSnSe₄ and Cu₂ZnSnS₄ have attracted a lot of attention as possible absorber materials for solar cells due to their direct bandgap and high absorption coefficient (> 10⁴ cm⁻¹). In this study we investigate the optical properties of Cu₂ZnSn(Se_xS_1 − x)₄ monograin powders that were synthesized from binary compounds in the liquid phase of potassium iodide (KI) flux materials in evacuated quartz ampoules. Radiative recombination processes in Cu₂ZnSn(Se_xS_1 − x)₄ monograins were studied by using low-temperature photoluminescence (PL) spectroscopy. A continuous shift from 1.3 eV to 0.95 eV of the PL emission peak position with increasing Se concentration was observed indicating the narrowing of the bandgap of the solid solutions. Recombination mechanisms responsible for the PL emission are discussed. Vibrational properties of Cu₂ZnSn(Se_xS_1 − x)₄ monograins were studied by using micro-Raman spectroscopy. The frequencies of the optical modes in the given materials were detected and the bimodal behaviour of the A₁ Raman modes of Cu₂ZnSnSe₄ and Cu₂ZnSnS₄ is established.     

Synthesis of nanostructured M/Fe3O4 (M = Ag,Cu) composites using hexamethylentetramine and their electrocatalytic properties

Nanoscaled Ag/Fe₃O₄ hybrids with different Ag contents and Cu/Fe₃O₄ nanoshpere and microsphere were successfully synthesized with assistance of sodium citrate and (CH₂)₆N₄ via a hydrothermal process. The as-prepared samples were identified and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. All samples were used as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution. The catalytic activity of Ag/Fe₃O₄ samples increased first and then decreased by increasing Ag content from 0% to 8%, and the one with 6% Ag displayed the highest catalytic activity. All the Cu/Fe₃O₄ samples exhibited enhanced catalytic activity by comparison with a glassy carbon electrode, and the one prepared with the molar ratio of Cu²⁺, Fe³⁺, citrate anion, and (CH₂)₆N₄ with 1:1:3:5 exhibited the highest catalytic activity.     

Hydrothermal synthesis and magnetic property of Cu3(OH)2V2O7·nH2O

Copper vanadium oxide hydroxide hydrate (Cu₃(OH)₂V₂O₇·nH₂O) nanoparticles with mean size of about 100 nm were successfully synthesized by a simple hydrothermal method. The structure and morphology of the as-synthesized products were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectra, and Fourier transform infrared spectra (FTIR). The composition and purity of the as-synthesized Cu₃(OH)₂V₂O₇·nH₂O nanoparticles were characterized by Energy disperse spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The magnetic property of the as-synthesized Cu₃(OH)₂V₂O₇·nH₂O nanoparticles was characterized by vibrant sample magnetometer. Magnetic hysteresis curve indicate that the as-synthesized nanoparticles are of weak ferromagnetic property at room temperature.     

Optical properties of Cu(In,Ga)Se2 and Cu2ZnSn(S,Se)4

The optical properties of CuInSe₂, CuGaSe₂, Cu₂ZnSnS₄, and Cu₂ZnSnSe₄ are investigated using three different first-principles methods, namely the generalized gradient approximation by Perdew, Burke, and Ernzerhof (PBE), the hybrid Hartree-Fock-like functional by Heyd, Scuseria, and Ernzerhof (HSE), and a Green's function approach (GW). The density-of-states, the complex dielectric function ε(ω) = ε₁(ω) + iε₂(ω), and the optical absorption coefficient α(ω) are determined, providing fundamental understanding of these materials. We find that even though the PBE method generates fairly accurate effective crystal potentials, the HSE and GW methods improve considerably the band-gap energies E_g and also the localization of the semicore states, thereby describing the optical properties much better. Furthermore, we also present optimized convergence parameters for the self-consistent HSE calculation in order to reduce the computational time of this orbital-dependent method.     

Synthesis and electrochemical properties of Nb-doped Li3V2(PO4)3/C cathode materials for lithium-ion batteries

Li₃V_2−xNb_x(PO₄)₃/C cathode materials were synthesized by a sol-gel method. X-ray diffraction patterns demonstrated that the appropriate addition of Nb did not destroy the lattice structure of Li₃V₂(PO₄)₃, and enlarged the unit cell volume, which could provide more space for lithium intercalation/de-intercalation. Transmission electron microscopy and energy dispersive X-ray spectroscopy analysis illustrated that Nb could not only be doped into the crystal lattice, but also form an amorphous (Nb, C, V, P and O) layer around the particles. As the cathode materials of Li-ion batteries, Li₃V_2−xNb_x(PO₄)₃/C (x ≤ 0.15) exhibited higher discharge capacity and better cycle stability than the pure one. At a discharge rate of 0.5C, the initial discharge capacity of Li₃V_1.85Nb_0.15(PO₄)₃/C was 162.4 mAh/g. The low charge-transfer resistances and large lithium ion diffusion coefficients confirmed that Li₃V_2−xNb_x(PO₄)₃/C samples possessed better electronic conductivity and lithium ion mobility. These improved electrochemical performances can be attributed to the appropriate amount of Nb doping in Li₃V₂(PO₄)₃ system by enhancing structural stability and electrical conductivity.     

Ultrasound assisted template-free synthesis of Cu(OH)2 and hierarchical CuO nanowires from Cu7Cl4(OH)10·H2O

Cu(OH)₂ nanowires have been synthesized by an ultrasound assisted solution route in absence of a template, using Cu₇Cl₄(OH)₁₀·H₂O as a precursor. Hierarchical CuO nanowires were obtained by a simple solid-state thermal transformation of these Cu(OH)₂ nanowires. The products were characterized by XRD, SEM, TEM and HRTEM. The ranges of diameters and lengths of the polycrystalline CuO nanowires are ca. 20-30 nm and several micrometers, respectively. Ultrasonic time is found an important factor to morphology of the CuO products. This could be a potential efficient way for large scale fabrication of CuO nanowires with hierarchical structures. Surface photovoltage spectra of the CuO nanowires in air, NH₃ and CH₂Cl₂ atmospheres were investigated, which demonstrates it a good photoelectric gas sensing material.     

Facile fabrication of La(OH)3 nanorod arrays and their application in wastewater treatment

Hexagonal and vertically aligned La(OH)₃ nanorod arrays have been fabricated in a large scale via a simple electrochemical method without any hard templates and surfactants. By the aid of potential-time curve, a possible formation process of the La(OH)₃ nanorod arrays is proposed, and the gas bubbles functioning as a dynamic template might be responsible for the growth of ordered La(OH)₃ nanorods. The total absorption capacities of the as-prepared products for Congo red is about 73.5 mg g^− 1, which shows an environmental engineering application in removing organic dye from water. In short, this synthetic method shows prominent advantages such as its low-cost, easy preparation, good adherence and suitability for preparing other nanoarrays.     

The crystallisation of Cu2ZnSnS4 thin film solar cell absorbers from co-electroplated Cu-Zn-Sn precursors

The best CZTS solar cell so far was produced by co-sputtering continued with vapour phase sulfurization method. Efficiencies of up to 5.74% were reached by Katagiri et al. The one step electrochemical deposition of copper, zinc, tin and subsequent sulfurization is an alternative fabrication technique for the production of Cu₂ZnSnS₄ based thin film solar cells. A kesterite based solar cell (size 0.5 cm²) with a conversion efficiency of 3.4% (AM1.5) was produced by vapour phase sulfurization of co-electroplated Cu-Zn-Sn films. We report on results of in-situ X-ray diffraction (XRD) experiments during crystallisation of kesterite thin films from electrochemically co-deposited metal films. The kesterite crystallisation is completed by the solid state reaction of Cu₂SnS₃ and ZnS. The measurements show two different reaction paths depending on the metal ratios in the as deposited films. In copper-rich metal films Cu₃Sn and CuZn were found after electrodeposition. In copper-poor or near stoichiometric precursors additional Cu₆Sn₅ and Sn phases were detected. The formation mechanism of Cu₂SnS₃ involves the binary sulphides Cu_2 − xS and SnS₂ in the absence of the binary precursor phase Cu₆Sn₅. The presence of Cu₆Sn₅ leads to a preferred formation of Cu₂SnS₃ via the reaction educts Cu_2 − xS and SnS₂ in the presence of a SnS₂(Cu₄SnS₆) melt. The melt phase may be advantageous in crystallising the kesterite, leading to enhanced grain growth in the presence of a liquid phase.     

Synthesis and characterization of bundle-like structures consisting of single crystal Ce(OH)CO3 nanorods

Bundle-like structures consisting of single crystal cerium hydroxide carbonate (Ce(OH)CO₃) nanorods have been synthesized successfully by a hydrothermal method at 100 °C using cerium nitrate (Ce(NO₃)₃·6H₂O) as the cerium source, aqueous carbamide both as an alkaline and carbon source and cetyltrimethylammonium bromide (CTAB) as surfactant. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to characterize such bundle-like structures. SEM and TEM images show that Ce(OH)CO₃ bundle-like structures were composed of nanorods with diameters of ∼ 100 nm. The XRD pattern and electron diffraction (ED) pattern indicate that Ce(OH)CO₃ has a pure orthorhombic single crystal structure.     

Photoluminescence and radioluminescence of pure and Ce activated Na3Gd(PO4)2

The spectroscopic properties of Na₃Gd(PO₄)₂ and Na₃Gd(PO₄)₂:Ce³⁺ phosphors in the VUV-UV spectral range were investigated. Five excitation bands of Ce³⁺ ions at Gd³⁺ sites are observed at wavelengths of 205, 246, 260, 292, and 321 nm. Doublet Ce³⁺ 5d → 4f emission bands are observed at 341 and 365 nm with a decay constant τ_1/e around 26 ns. The X-ray excited luminescence of Na₃Gd_0.99Ce_0.01(PO₄)₂ at room temperature shows a photon yield of ∼17,000 photons/MeV of absorbed X-ray energy.     

Thermoluminescence properties of Ce-doped LiSr4(BO3)3 phosphor

Borates LiSr₄(BO₃)₃ were synthesized by high-temperature solid-state reaction. The thermoluminescence (TL) and some of the dosimetric characteristics of Ce³⁺-activated LiSr₄(BO₃)₃ were reported. The TL glow curve is composed of only one peak located at about 209 °C between room temperature and 500 °C. The optimum Ce³⁺ concentration is 1 mol% to obtain the highest TL intensity. The TL kinetic parameters of LiSr₄(BO₃)₃:0.01Ce³⁺ were studied by the peak shape method. The TL dose response is linear in the protection dose ranging from 1 mGy to 1 Gy. The three-dimensional thermoluminescence emission spectra were also studied, peaking at 441 and 474 nm due to the characteristic transition of Ce³⁺.     

Near UV-based LED fabricated with Ba5SiO4(F,Cl)6:Eu as blue- and green-emitting phosphor

A series of halosilicate phosphor, Ba₅SiO₄(F,Cl)₆:Eu²⁺, were synthesized by a solid state reaction. Excited by 370-nm light, Ba₅SiO₄Cl₆:Eu²⁺ exhibits a broad emission band peaking at 440 nm. Partial substitution of Cl⁻ with F⁻ in the host lattice leads to red-shift in the emission band with centering wavelength from 440 nm to 503 nm. The possible mechanism for the luminescence change was discussed based on the XRD patterns. Blue and green LEDs were fabricated by combination of a 370 nm-emitting near UV chip and the optimal Ba₅SiO₄Cl₆:Eu²⁺ and Ba₅SiO₄(F₃Cl₃):Eu²⁺, respectively. This series of phosphors is considered as a promising blue and green component used in fabrication of near UV-based white LEDs.     

Growth of Cu2ZnSnS4 thin films on Si (100) substrates by multisource evaporation

Cu₂ZnSnS₄ films were grown on Si (100) by vacuum evaporation using elemental Cu, Sn, S and binary ZnS as sources. X-ray diffraction patterns of films grown at different substrate temperatures indicated that polycrystalline growth was suppressed and the orientational growths were relatively induced in a film grown at higher temperatures. Tetragonal structure of Cu₂ZnSnS₄ films was confirmed by studying RHEED patterns. The existence of c-axis ([001] direction) growth, two kinds of a-axis (〈100〉 direction) growth and four kinds of {112} twins which can be classified as two symmetrical pairs is proposed. Broad emissions at around 1.45 eV and 1.31 eV were observed in the photoluminescence spectrum measured at 13 K.     

Structure and phase relations in the 2(CuInS2)-Cu2ZnSnS4 solid solution system

The intermixing of roquesite (CuInS₂) and kesterite (Cu₂ZnSnS₄), i. e. Cu(In_x(ZnSn)_1−xS₂ was investigated by a combination of neutron and X-ray powder diffraction. Samples with 0 ≤ × ≤ 1 were synthesized by a solid state reaction of the pure elements in evacuated silica tubes at 800 °C and cooled with a 10 K/h rate after the final annealing. The structural parameters of CuIn_x(ZnSn)_1−xS₂ were determined by simultaneous Rietveld refinement of neutron and X-ray diffraction data. The microstructure and chemical composition of the samples were investigated by electron microprobe analysis. A broad miscibility gap exists in the region 0.4 ≤ × < 0.8 indicated by the coexistence of two phases, an In-rich (x ~ 0.77) and a Zn-Sn-rich (x ~ 0.33) phase. Cu(In_x(ZnSn)_1−xS₂ mixed crystals with 0 ≤ x < 0.4 crystallize in the kesterite type structure, and with 0.8 ≤ × ≤ 1.0 in the chalcopyrite type structure. In the latter In, Zn and Sn are disordered on the In site. In the mixed crystals the lattice constant a and c show a linear dependence on chemical composition, whereas the tetragonal deformation Δ = 1−c/2a varies nonlinearly. Moreover in the mixed crystal with x ~ 0.15 the tetragonal deformation is equal zero and thus its structure is characterized by a pseudo-cubic unit cell.     

Controlled synthesis of hierarchically porous β-Ni(OH)2 microspheres and NiO nanoparticles with the optical property of NiO nanoparticles

In this study, we demonstrate the preparation of novel hierarchically porous β-Ni(OH)₂ microspheres constructed with nanoflakes through a simple solution-phase approach, using NiCl₂·6H₂O and hexamethylenetetramine (HMTA) as the starting materials without adding any additives. NiO nanoparticles with the average diameter of 10 nm were obtained by calcining the as-prepared β-Ni(OH)₂ microspheres at 500 °C under ambient pressure. On the other hand, β-Ni(OH)₂ nanoplates were prepared by substituting HMTA with NaOH as the basic source, revealing the realization of shape-controlled synthesis of β-Ni(OH)₂ nanostructures. Optical property of the NiO nanoparticles was conducted by means of UV-vis spectrum, exhibiting small blue shift compared with the bulk counterpart. The possible mechanisms for selective formation of β-Ni(OH)₂ microspheres and nanoplates were in brief discussed.     

Facile preparation and enhanced photocatalytic H2-production activity of Cu(OH)2 nanospheres modified porous g-C3N4

A facile precipitation approach for the preparation of Cu(OH)₂/g-C₃N₄ composite photocatalysts with good porous structure was developed for the first time. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible light (UV–vis) absorbance spectra, photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). A photocatalytic water splitting reaction on the as-prepared photocatalysts were carried out under visible light irradiation. The results revealed that the prepared samples showed significantly enhanced photocatalytic activity. The optimal Cu(OH)₂ loading content was found to be 0.34 mol%, giving an H₂-production rate of 48.7 μmol h⁻¹ g⁻¹, which is higher 16.5 times than that of pure g-C₃N₄. This high photocatalytic H₂-production activity is attributed to the presence of Cu(OH)₂ clusters on the surface of the porous g-C₃N₄, which efficiently promotes the visible light absorption and separation of photogenerated electron–hole pairs.