Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier

The nanoparticles of Fe₃O₄ as well as the binary nanoparticles of ionic liquid and Fe₃O₄ (IL-Fe₃O₄) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe₃O₄ nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60 mg, a pH of 2.5, and a contact time of 2 min when initial dyes concentrations of 10-200 mg L⁻¹ were used. The maximum adsorption capacity of IL-Fe₃O₄ was 166.67 and 49.26 mg g⁻¹ for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62 L mg⁻¹ for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe₃O₄ by using a mixed NaCl-acetone solution and adsorbent was reusable.     

Redox doping behaviour of poly(3,4-ethylenedithiothiophene) - The counterion effect

Poly(3,4-ethylenedithiothiophene) - PEDTT, an alkylene sulphur derivative of PEDOT, presents itself as an interesting polymer with a number of disparate redox and chromic properties compared to its close analogue - PEDOT. In this study we present the results of an investigation into the electrochemical doping process of PEDTT, using four different electrolyte solutions, differing in anion content of the chosen salt. The results show that the anion identity plays a key role in the redox reactions accompanying these processes in what could be interpreted as anion ionochromism. In situ UV-Vis spectroelectrochemical experiments reveal an intriguing double electrochromic transition of PEDTT films during their oxidative doping, going from golden-yellow through green to pomegranate - a quality not so common within the family of electroactive conjugated polymers. The evolution of each UV-Vis spectrum over a potential range indicates that different redox states of the polymer are responsible for the chromatic changes. In the reduction half-cycle, the dedoping process of PEDTT appears to follow a path dissimilar to the p-doping one, featuring only one, direct electrochromic transition of the film’s colour, bypassing the green state, and a distinct two-step bleaching process of doping-induced charge carrier bands. The observed electrochemical and spectral phenomena have been accredited to the specific redox behaviour of doping-induced radical cation and cationic defect states interacting with the dithioalkylene sulphur atom.     

Preconcentration and Voltammetric Determination of Mercury(II) at a Chemically Modified Glassy Carbon Electrode

In this work, the organic compound 2-mercaptobenzimidazole was covalently bound on the surface of a glassy carbon rod, via silanization, yielding a material capable of selectively complexing Hg(2+) ions. This material was applied as an electrode for voltammetric determination of mercury(II) following its nonelectrolytic preconcentration. After exchanging the medium, the voltammetric measurements were carried out by anodic stripping in the differential pulse mode (pulse amplitude, 50 mV; scan rate, 1.25 mV s(-)(1)) using 10(-)(2) mol L(-)(1) NaSCN solution as supporting electrolyte. An anodic stripping peak was obtained at 0.06 V (vs SCE) by scanning the potential from -0.3 to +0.3 V. After a 5 min preconcentration period in a pH 4.0 Hg(2+) solution, this electrode shows increasing voltammetric response in the range 0.1-2.2 μg mL(-)(1), with a relative standard deviation of 5% and a practical detection limit of 0.1 μg mL(-)(1) (5.0 × 10(-)(7) mol dm(-)(3)). Compared with the conventional stripping approach, this chemically modified glassy carbon electrode procedure presented good discrimination against interference from Cu(II) in up to 10-fold molar excess.     

Fabrication and Evaluation of Low-cost Cu2ZnSn(S,Se)4 Counter Electrodes for Dye-sensitized Solar Cells

Nano-Micro Letters - We explore a simple and eco-friendly approach for preparing CZTS powders and a screen-printing process for Cu2ZnSn(S,Se)4 (CZTSSe) counter electrodes (CEs) in dye-sensitized...     

Photoluminescence of Ca(Ba)Ga2S4:RE poly- and nanocrystals

The photoluminescence and photoluminescence excitation spectra and luminescence decay kinetics of CaGa₂S₄:Eu²⁺ bulk crystals and powders ranging in particle size from 100 to 600 nm have been studied in the temperature range 77–300 K. The results indicate that the full width at half maximum of the photoluminescence band of the CaGa₂S₄:Eu²⁺ nanopowders is about twice that of the bulk crystals. Analysis of the photoluminescence spectra shows that the energy position of the emission band is almost independent of the particle size, temperature, and excitation intensity in the ranges 77–300 K and 10^?3 to 10⁶ W/cm², respectively. The shape of the photoluminescence band is well represented by a Gaussian. The excited state lifetime of the Eu²⁺ ion is ～1000 ns as evaluated from the exponential portion of the luminescence decay curve.     

Electrochemical behaviour of polypyrrole films modified with poly-Cu(v-bpy) 2 2+

Poly-Cu(v-bpy)₂(ClO₄)₂ was electrochemically implanted into a polypyrrole-polymer matrix at levels of 10 to 12% in order to improve the electrical properties of the electrode. To increase the porosity and orientation of the pyrrole polymer, the electrode was pretreated with nitrile butadiene rubber (NBR) and PF ₆ ^- was the dopant anion. The presence of poly-Cu(v-bpy) ₂ ²⁺ enhanced the doping level to 65.6%, the conductivity by a factor of two, and the carrier concentration by a factor of ten. However, the cyclability was reduced by half, relative to polypyrrole alone, and the doping/undoping efficiency was diminished slightly from 0.94 (for polypyrrole alone) to 0.90.     

Electrochemical behaviour of LiM y Mn2−y O4 (M = Cu, Cr; 0 ≤y ≤ 0.4)

Spinel lithium manganese oxide, LiMn₂O₄, is beset with problems of capacity fade upon repeated cycling. The loss in capacity upon cycling is attributable to Jahn-Teller distortion and manganese dissolution in the electrolyte in the charged state. One way to circumvent this capacity fade is to introduce other 3d bdtransition metal ions in the LiMn₂O₄ lattice. In this paper, we report on the effect of partial substitution of manganese in the LiMn₂O₄ phase with copper (II) and chromium (III) ions. It has been shown that the higher octahedral stabilization energy of trivalent chromium imparts greater structural stability to chromium-doped LiMn₂O₄ spinels. Both copper and chromium reduce the capacity of the spinel in the 4 V region. In terms of its good reversible capacity and ability to sustain cycling with minimal capacity fade, LiCr_0.1Mn_1.9O₄ may be considered as a potential cathode material for lithium rechargeable cells.     

Optical and differential scanning calorimetry studies of the (Na2B4O7)-(CuO)-(CeO2) glass system

A series of glass samples was prepared from an admixture of sodium tetraborate, copper and cerium based on the system (Na2B4O7)98-(CuO)2-x-(CeO2)x where x=0.5, 1 and 1.5 mol%, and results of optical absorption, infrared absorption spectra and differential scanning calorimetry are reported as a function of copper and cerium contents. It was found that increasing the CuO content and decreasing the CeO2 content shifted the fundamental absorption edge to longer wavelengths. It was also found that the incorporation of CuO and CeO2 did not affect the limits of the ultraviolet absorption edge of the base glass. This revised version was published online in November 2006 with corrections to the Cover Date.     

聚3-(4-氟苯)噻吩与偶联剂改性RuO_2复合材料的制备

采用固体研磨法使RuCl3.xH2O与NaOH在室温下反应,产物在空气中200℃热处理3h后得到了RuO2颗粒。进而在室温下以硅烷偶联剂KH-550对RuO2颗粒进行表面改性,得到在氯仿中有良好分散性的改性RuO2颗粒。再将改性RuO2颗粒分散到3-(4-氟苯)噻吩(FPT)的氯仿溶液中,并以无水三氯化铁(FeCl3)为氧化剂,采用化学聚合法制备了PFPT/RuO2复合材料。对复合材料的结构与形貌进行了FT-IR、XRD、SEM等表征,并在0.5mol/L硫酸溶液中,用循环伏安(C-V)和恒电流充放电等测试研究了复合材料的电化学性质,结果表明,复合材料中RuO2的比容量可达390F/g。     

Highly selective ratiometric fluorescence determination of Eu3+ ion based on (4E)-4-(2-phenyldiazenyl)-2-((E)-(2-aminoethylimino)methyl)phenol

(4E)-4-(2-phenyldiazenyl)-2-((E)-(2-aminoethylimino)methyl)phenol (PAMP) was synthesized for the first time and used as a ratiometric fluorescent chemosensor for recognition of Eu³⁺ ions in acetonitrile solution. PAMP shows a fluorescent emission at 536 nm. When it forms a complex with Eu³⁺ ion, two new fluorescent enhancements at 418 and 496 nm appeared. In acetonitrile solution, the blue shift of fluorescent emission upon europium binding is due to the formation of a 1:1 metal ligand complex. The chemosensor shows a linear response toward Eu³⁺ in the range of 8.3 × 10^? 8 M to 8.3 × 10^? 6 M. The new fluorescent probe exhibits high selectivity toward Eu³⁺ ions over a large number of interfering cations.     

Full Activation of Mn4+/Mn3+ Redox in Na4MnCr(PO4)3 as a High‐Voltage and High‐Rate Cathode Material for Sodium‐Ion Batteries

Developing high‐voltage cathode materials is critical for sodium‐ion batteries to boost energy density. NASICON (Na super‐ionic conductor)‐structured Na_xMnM(PO₄)₃ materials (M represents transition metal) have drawn increasing attention due to their features of robust crystal framework, low cost, as well as high voltage based on Mn⁴⁺/Mn³⁺ and Mn³⁺/Mn²⁺ redox couples. However, full activation of Mn⁴⁺/Mn³⁺ redox couple within NASICON framework is still a great challenge. Herein, a novel NASICON‐type Na₄MnCr(PO₄)₃ material with highly reversible Mn⁴⁺/Mn³⁺ redox reaction is discovered. It proceeds a two‐step reaction with voltage platforms centered at 4.15 and 3.52 V versus Na⁺/Na, delivering a capacity of 108.4 mA h g^?1. The Na₄MnCr(PO₄)₃ cathode also exhibits long durability over 500 cycles and impressive rate capability up to 10 C. The galvanostatic intermittent titration technique (GITT) test shows fast Na diffusivity which is further verified by density functional theory calculations. The high electrochemical activity derives from the 3D robust framework structure, fast kinetics, and pseudocapacitive contribution. The sodium storage mechanism of the Na₄MnCr(PO₄)₃ cathode is deeply studied by ex situ X‐ray diffraction (XRD) and ex situ X‐ray photoelectron spectroscopy (XPS), revealing that both solid‐solution and two‐phase reactions are involved in the Na⁺ ions extraction/insertion process.     

Thermal behaviour of the O2/TiO2 (110)-(1 × 2) surface

Synchrotron radiation ultra-violet photoemission at different photon energies (17.1, 19.3, and 21.5 eV) has been used to study the interaction of O₂ with the TiO₂ (110)-(1 × 2) surface reconstruction at temperatures between 77 and 320 K. At 77 K the results show a weak molecular chemisorption of the O₂ molecule on the surface. By analysing the thermal behaviour of the O₂/TiO₂ system in a temperature range from 77 to 320 K, it has been found that between 120 and 200 K the O₂ molecule is dissociated.     

The annealing of misfit dislocations in the (111) Cu/(111) Cu2O system

Recent work on the early stages of the epitaxial oxidation of (111) Cu at 350 °C and in oxygen pressures between 10^-7 and 10^-4 Torr has resulted in the determination of the growth modes that occur and the accompanying elastic strains. Initially a hexagonal 3 × 3 oxide superlattice is formed which continues to grow by a layer growth mechanism up to a theoretically estimated thickness of approximately five monomolecular layers. Subsequent oxidation occurs by the formation of lamellar islands containing misfit dislocations which reduce the coincidence lattice misfit strain. In the present work these (111) Cu/(111) Cu₂O bilayers were annealed and examined in situ in the transmission electron microscope in the temperature range 25–350 °C. The misfit dislocation density decreased as the temperature was increased. The annealing effects are complex and interdiffusion phenomena can be observed even at 60 °C.     

Effect of fullerene intercalation on the conformation and packing of poly-(2-methoxy-5-(3'-7'-dimethyloctyloxy)-1,4-phenylenevinylene)

Photoluminescence (PL) and resonance Raman spectroscopy are used to track changes in the conformations and packing of poly-(2-methoxy-5-(3'-7'-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) chains with the addition of [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) molecules. PL lineshapes of MDMO-PPV thin films as a function of annealing time were first measured to determine the spectroscopic signatures of chain conformations and packing in the absence of PCBM. Annealing results in enhanced interchain interactions leading to red-shifts of PL 0-0 transitions by up to ～300 cm(-1) and apparent increases of the line shape Huang-Rhys factors. Wavelength-dependent PL lifetimes of as-cast and films annealed for short times (～30 s) are nonexponential with an instrument-limited component of ～100 ps and a ～350 ps component. With longer annealing times, decays become single exponential with an average lifetime of ～1 ns indicating that all excitations efficiently funnel to strongly coupled interchain sites. Addition of PCBM disrupts MDMO-PPV interchain interactions causing PL 0-0 transitions to blue-shift, increases in line width, and decreases in apparent Huang-Rhys factors. Resonance Raman spectra of MDMO-PPV/PCBM thin films with variable PCBM weight fractions (～50:1 up to 1:8 w/w) were then measured using short (488 nm) and long (568 nm) excitation wavelengths. The out-of-plane vinylene C-H wag mode of MDMO-PPV (～964 cm(-1)) showed pronounced increases in intensity of up to ～30% and red-shifts of up to 5 cm(-1) with increasing PCBM content. These changes result from a decrease of planarity between chain segments that suppresses interchain interactions. Furthermore, red-shifts of up to ～4 cm(-1) were observed for the C═C symmetric stretch of the MDMO-PPV vinylene group (～1625 cm(-1)) with 488 nm excitation. The sensitivity of the MDMO-PPV vinylene group vibrations with PCBM indicates preferential interactions between these two molecules and is consistent with intercalation of PCBM into the polymer structure. This assignment was confirmed by thermally annealing of MDMO-PPV/PCBM films to remove intercalated PCBM molecules, which partially restores interchain interactions as seen from smaller intensity increases (～15%) and red-shifts (～2 cm(-1)) of the ～964 cm(-1) mode. Overall, the spectroscopic results show that MDMO-PPV chains adopt distorted conformations (i.e., less intrachain order and shorter conjugation lengths) that have important implications for explaining the structural origins for large improvements in charge mobilities in MDMO-PPV/PCBM blends.     

Electrical inhomogeneity at the mott transition in the band width controlled κ-(BEDT-TTF)2Cu[N(CN)2Br

The electronic phase separation on macroscopic scale is studied in the organic Mott system κ-(BEDT-TTF)₂Cu[N(CN)₂]Br by means of scanning micro-region infrared spectroscopy using the synchrotron radiation. The phase separation appears in the vicinity of the Mott boundary in the single crystals of which the band width is controlled by partly substituting the BEDT-TTF molecule with the deuterated one. The transport properties under the phase separation are considered to be influenced by the percolation process of the domains.