Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

Dielectric and electric studies of the [N(CH3)4][N(C2H5)4]ZnCl4 compound at low temperature

The [N(CH₃)₄][N(C₂H₅)₄]ZnCl₄ compound was prepared and characterized by electrical technique. The temperature dependence of the dielectric permittivity shows that this compound is ferroelectric below T = 268 K. The two semi-circles observed in the complex impedance identify the presence of the grain interior and grain boundary contributions to the electrical response in the material. The equivalent circuit is modeled by a combination series of two parallel R_P–CPE circuits. The frequency dependent conductivity is interpreted in term of Jonscher's law. The modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (K.W.W.) function: ?(t) = exp [(−t/τ)^β]. The temperature dependence of the alternative current conductivity (σ_p), direct current conductivity (σ_dc) and the relaxation frequency (f_p) confirm the presence of the ferroelectric–paraelectric phase transition.     

Chemical resistance properties of molybdenum back electrodes used in non-vacuum Cu(In,Ga)Se2 thin film solar cell

The first step in fabricating copper-indium-gallium-diselenium solar cells (CIGS) is to deposit a thin film of molybdenum (to serve as the back electrode), on a glass substrate. Prior to depositing the absorption layer, the surface of the Mo back electrode is cleaned with acetone; however, this may cause the electrode to separate from the substrate. The aim of this study was to discover the specific cause of the separation, and arrive at a solution to correct this behavior. The result is a thin film comprising crystals of different sizes and orientations. Optimal results were obtained when the bi-layer Mo electrode was deposited on a substrate heated to a temperature of 373 K.     

Synthesis and characterization of novel nanostructured fishbone-like Cu(OH)2 and CuO from Cu4SO4(OH)6

The Cu₄SO₄(OH)₆ was synthesized by a simple hydrothermal reaction with a yield of ~ 90%. Using Cu₄SO₄(OH)₆ as the starting material, novel fishbone-like Cu(OH)₂ was produced by a direct reaction of Cu₄SO₄(OH)₆ with NaOH solution. The Cu(OH)₂ consists of many needle-like nanorods parallel to each other and perpendicular to the direction of backbone, forming fishbone-like structure. Using the fishbone-like Cu(OH)₂ as the sacrificial precursor, CuO with similar size and morphology was obtained through a simple heat treatment. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-Vis absorption spectroscopy were employed to characterize the as-prepared samples. The conversion of the Cu₄SO₄(OH)₆ to the fishbone-like Cu(OH)₂ was visualized by time-dependent SEM images. A mechanism was also proposed based on the observed results.     

二氧化钛的制备及以其为载体的脱硝催化性能研究

以工业化生产的偏钛酸为原料,制备出颗粒均匀的球形二氧化钛颗粒。通过扫描电子显微镜、X射线衍射、BET比表面积、激光粒度分布等测试方法,分析表征了颗粒的结构形态及表面理化性质。以所制备的二氧化钛为载体,以偏钒酸铵为V2O5(活性物质)的前驱体,制备脱硝催化剂,考察催化剂的脱硝活性,结果表明,当燃烧温度为370℃时,所制备的催化剂的脱硝效率为75%。     

Comparative study of Cu(In,Ga)Se2/(PVD)In2S3 and Cu(In,Ga)Se2/(CBD)CdS heterojunction based solar cells by admittance spectroscopy, current-voltage and spectral response measurements

Co-evaporated Cu(In,Ga)Se₂ (CIGSe) based solar cells with Physical Vapour Deposited (PVD) Indium Sulphide (In₂S₃) as buffer layer have been studied by admittance spectroscopy and current-voltage characteristics measurements. The results have been compared to those obtained with a reference CBD-CdS/CIGSe device. In darkness, the PVD-In₂S₃ buffer layer devices exhibit higher densities of trapping defects and low values of shunt resistance. However, under illumination we have observed an important improvement of the In₂S₃/CIGSe electronic transport properties. This behavior seems to be linked to the presence of a metastable defect with activation energy of 0.3 eV.     

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.     

Selective removal of Pb(II), Cd(II), and Zn(II) ions from waters by an inorganic exchanger Zr(HPO3S)2

The present study reported synthesis of a new inorganic exchanger, i.e., zirconium hydrogen monothiophosphate [Zr(HPO₃S)₂, denoted ZrPS] and its selective sorption toward Pb(II), Cd(II) and Zn(II) ions. ZrPS sorption toward all the three metals is dependent upon solution pH due to the ion-exchange nature. As compared to another inorganic exchanger zirconium phosphate [Zr(HPO₄)₂, denoted ZrP], ZrPS exhibits highly selective sorption toward these toxic metals from the background of calcium ions at great levels. Such sorption preference is mainly attributed to the presence of –SH group in ZrPS, as further demonstrated by FT-IR analysis and XPS study. Moreover, ZrPS particles preloaded with heavy metals could be efficiently regenerated with 6 M HCl for multiple use without any noticeable capacity loss. All the experimental results indicated that ZrPS is a promising sorbent for enhanced heavy metals removal from contaminated water.     

Influence of absorber copper concentration on the Cu(In,Ga)Se2/(PVD)In2S3 and Cu(In,Ga)Se2/(CBD)CdS based solar cells performance

The present contribution deals with the influence of the copper concentration in Cu(In,Ga)Se₂ (CIGSe) on the solar cells based on CIGSe/(PVD)In₂S₃ and CIGSe/(CBD)CdS. We find that, depending on the buffer layer, the optimum open circuit voltage (Voc) is not reached for the same copper concentration. The values of Voc for the CIGSe/(CBD)CdS solar cells are higher when the copper content is very close to stoichiometry (25%), whereas, the Voc values for CIGSe/(PVD)In₂S₃ solar cells attain their maximum for lower copper contents. On the other hand, contrary to the case of the (CBD)CdS buffer, the Jsc is strongly hindered for the (PVD)In₂S₃ buffered cells when the copper content is lowered. The study has been made for different absorber gallium contents and the evolution is coherent with the presence of a cliff at the CIGSe/(PVD)In₂S₃ interface.     

White OLEDs based on novel emissive materials such as Zn(HPB)2 and Zn(HPB)q

Organic light emitting diodes (OLEDs) show a lot of advantages for display purposes. Because OLEDs provide white light emission with high efficiency and stability, it is desirable to apply OLEDs as an illumination light source and backlight in LCD displays. We synthesized new emissive materials, namely [2-(2-hydroxyphenyl)benzoxazole] (Zn(HPB)₂) and [(2-(2-hydroxyphenyl)benzoxazole)(8-hydoxyquinoline)] (Zn(HPB)q), which have a low molecular compound and thermal stability. We studied white OLEDs using Zn(HPB)₂ and Zn(HPB)q. The fundamental structures of the white OLEDs were ITO/PEDOT:PSS (23 nm)/NPB (40 nm)/Zn(HPB)₂ (40 nm)/Zn(HPB)q (20, 30 or 40 nm)/Alq₃ (10 nm)/LiAl (120 nm). As a result, when the thickness of the Zn(HPB)q layer was 20 nm, white emission is achieved. We obtained a maximum luminance of 15325 cd/m² at a current density of 997 mA/cm². The CIE (Commission International de l'Eclairage) coordinates are (0.28, 0.35) at an applied voltage of 9.75 V.     

暴露(001)晶面的纳米TiO2/SiC复合纤维气敏性能

锐钛矿相的TiO₂晶体主要由热力学稳定的(101)晶面组成,而具有较高活性的(001)晶面所占比例较少。通过F离子的引入,当其吸附在TiO₂的高活性(001)晶面上时,可以使晶面的表面能降低,从而制备出暴露(001)晶面的TiO₂。为提高该TiO₂的气敏性能,通过水热法将纳米TiO₂与SiC超细纤维复合,制备出具有分级结构的TiO₂/SiC复合纤维,以此解决TiO₂回收难及单晶TiO₂之间团聚的问题。结果表明,对于丙酮气体,所合成的TiO₂/SiC复合纤维的灵敏度(21.2)是暴露(001)晶面的纳米TiO₂灵敏度(14.0)的1.5倍,是商业TiO₂灵敏度(4.0)的5.3倍。     

Influence of sodium compounds at the Cu(In,Ga)Se2/(PVD)In2S3 interface on solar cell properties

The present contribution deals with indium sulfide buffer layers grown by thermal co-evaporation of elemental indium and sulfur. It has been found necessary to deposit these buffer layers at low substrate temperatures in order to reach V_oc values similar to those with (CBD)CdS. However, such deposition conditions lead to the formation of a highly recombinative Cu(In,Ga)Se₂/indium sulfide interface. This behaviour may be associated to the presence of sodium carbonates/oxides at the interface even though the Cu(In,Ga)Se₂ surface was cleaned in NH₃ (1 M, room temperature) prior to the indium sulfide deposition. An explanation is that, despite the chemical etch, sodium carbonates/oxides remain in the air exposed Cu(In,Ga)Se₂ grain boundaries and can migrate towards the surface when the Cu(In,Ga)Se₂ is heated under vacuum. These polluted interface areas act as recombination zones and thus inferior devices. A possibility to improve the device performance (i.e. improve the interface quality) is to sulfurize the remaining sodium carbonates/oxides. The resulting Na₂S can then leave the interface by formation of a solid solution with the indium sulfide. By adapting the buffer layer deposition process, 13.3% efficiency devices with co-evaporated indium sulfide are realized, performance which is close to that reached with (CBD)CdS.     

Study on structural phase transitions and relaxation processes of Cs2Co(SO4)2·6H2O and Cs2Zn(SO4)2·6H2O crystals

The structural phase transitions and relaxation processes of Cs₂Co(SO₄)₂·6H₂O and Cs₂Zn(SO₄)₂·6H₂O single crystals were investigated, with the phase transitions of both crystals being determined from NMR data. The spin–lattice relaxation time, T₁, of the ¹³³Cs nucleus in two crystals undergoes a significant change near the phase transition temperature, T_C, and these changes coincide with the changes in the splitting of the ¹³³Cs resonance lines. The variations in the temperature dependence for the splitting of the ¹³³Cs resonance lines and T₁ near T_C are related to changes in the symmetry of surrounding Cs⁺. In addition, the ¹³³Cs T₁ of Cs₂Co(SO₄)₂·6H₂O, which contains paramagnetic ions, was found to be shorter than that of Cs₂Zn(SO₄)₂·6H₂O. This relaxation time is inversely proportional to the square of the magnetic moment of the paramagnetic ions. The differences between the ¹³³Cs T₁ of these compounds are probably due to the differences between the electronic structures of their metal ions.     

Time-resolved spectroscopy of intrinsic luminescence of Y3Ga5O12 and (LaLu)3Lu2Ga3O12 single crystals

The nature of intrinsic luminescence of Y₃Ga₅O₁₂ (YGG) and (LaLu)₃Lu₂Ga₃O₁₂ (LLGG) single crystals grown from a melt was determined. In the case of a YGG single crystal containing Y_Ga antisite defects with a concentration of 0.25–0.275 at.% the intrinsic luminescence was considered as a superposition of luminescence of self-trapped excitons (STE), luminescence of excitons localized near antisite defects (LE(AD) centers) and luminescence caused by a recombination of an electron with a hole captured at Y_Ga antisite defects. Due to a large (2–3%) concentration of Lu_La antisite defects in LLGG single crystals the intrinsic luminescence was a superposition mainly of the LE(AD) center emission and the recombination luminescence of Lu_La antisite defects. The energy structure of the mentioned centers in YGG and LGGG hosts was determined from the excitation spectra of their luminescence under excitation by synchrotron radiation in the range of the fundamental absorption edge of these garnets.     

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 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.     

Effect of precursor structure on Cu(InGa)Se2 formation by reactive annealing

Precursor structures of Mo/CuGa/In, Mo/In/CuGa, Mo/In/CuGa/In and Mo/CuGaIn were prepared on thin sodium-free glass by the sputtering of CuGa and In targets. In-situ phase evolution of precursors with temperature was investigated by a high-temperature X-ray diffraction system, which verified the existence and transformation of several intermetallics: Cu₂In, Cu₁₁In₉, Cu₃Ga, Cu₇In₃, Cu₉Ga₄ and Cu₁₆In₉ as well as elemental In. MoSe₂ layers produced during selenization were detected by scanning electron microscope and X-ray diffraction, with their thicknesses varying by precursor structure. Adhesion strength of Cu(InGa)Se₂ to each Mo layer was assessed by applying CdS chemical bath deposition process to each sample.     

Giant domain formation in Langmuir-Blodgett films based on Alkylammonium-Au(dmit)2 salt

The crossed polarized-light microscopy has revealed that the as-deposited LB film of the 2C₁₄-Au(dmit)₂ salt consists of giant domains of several hundred microns, which have a uni-axial molecular arrangement. By the electrochemical oxidation, the giant domains disappear and smaller domains of 5-10 μm appear. According to the atomic force microscopy (AFM) observation, the as-deposited film consists of domains of several microns but it appears that the observed domains are fragments formed by cracks generated in much larger domains, as seen by the shapes. It is hypothesized that there exist giant domains at the air/water interface but cracks are made during the transfer process. Thus, the uni-axial molecular arrangement is kept over the macroscopic range. Considering the random potentials set up by grain boundaries and/or defects, fabrication of the crack-free LB film is considered to be indispensable for realizing metallic properties down to much lower temperatures and global superconductivity.     

The effect of Sb2O5 additions on the dielectric properties of Ag(Nb0.8Ta0.2)O3 ceramics

The sintering behavior and dielectric properties for perovskite Ag(Nb_0.8Ta_0.2)O₃ ceramic with Sb₂O₅ doping was explored. A small amount of Sb₂O₅ (2.5 wt.%) led to high densification at temperatures < 1060 °C. The dielectric constant increased and the temperature coefficient decreased with increasing concentration of Sb₂O₅, and the dielectric constant reached 673, combined with a low temperature coefficient of 147 ppm/°C, and dielectric loss of 0.0044 (at 1 MHz) for the sample with 3.5 wt.% Sb₂O₅ sintered at 1080 °C.     

Electrodeposition based synthesis of S-rich CuIn(S,Se)2 layers for photovoltaic applications: Raman scattering analysis of electrodeposited CuInSe2 precursors

Single step electrodeposition (ED) of Se-rich CuInSe₂ precursors, followed by RTP annealing under sulphurising conditions leading to S-rich CuIn(S,Se)₂ films, constitutes a promising technology for low cost high efficiency solar cells. In this work, a Raman scattering (RS) analysis of Se rich precursors grown under ED conditions leading to different chemical compositions is reported. RS has allowed identification of the main secondary phases in these layers with elemental Se, Cu-Se binary and ordered vacancy compound (OVC) phases. The experimental data show a strong dependence of the spectral contributions related to Se and Cu-Se with the layer molecularity, and the formation of these phases is mainly determined by the content of excess Se in the layers. The correlation of these data with the characteristics of the solar cells fabricated with these precursors, shows the strong impact of the presence of the Cu-Se phase on the performance of the final devices. These results point out the key role played by this binary phase on the formation of secondary phases after the sulphurising step.