Mole-controlled growth of Y-doped ZnO nanostructures by hydrothermal method

We investigated the mole-controlled growth of Y-doped ZnO (YZO) nanostructures by the hydrothermal synthesis techniques. Through controlling the aqueous solution's mole concentration, we could modify the morphological and structural properties of YZO. The shape of YZO becomes a nanometer-sized rod when using a relatively low mole concentration, whereas the morphology is changed to be flat and mosaic when using a relatively high mole concentration. Since the aqueous solution's mole concentration decides the amount of hydroxide, we ascribe the mole-controlled morphological changes to the alteration of chemical potential during the hydrothermal chemical reaction.     

Aggregates in mixtures of ionic liquids

Surfactant-like ionic liquids (C₁₆MIMCl, C₁₆MIMBF₄) aggregate in mixtures with another ionic liquid (EAN). Critical aggregate concentrations and estimations of object sizes are given and compared to aqueous systems and other relevant literature data. The investigated mixtures are stable up to more than 200 °C and can probably be used to extend the limited temperature range of water-based colloids.     

Synthesis, morphology and random laser action of ZnO nanostructures

Three-dimensional (3-D) ZnO random-wall nanostructures and one-dimensional (1-D) ZnO nanorods were prepared on silicon substrates by a simple solid-vapour phase thermal sublimation technique. Optical pumped random lasing has been observed in the ZnO random-wall arrays with a threshold intensity of 0.38 MW/cm² in the emission wavelength from 380 to 395 nm. The optical gain was attributed to the closed-loop scattering and light amplification of the ZnO random-wall. The experimental result suggests that the morphology of nanostructure is the key factor to effect random lasing.     

ZnO-ionic liquid nanostructures

The mixture of nanostructures derived from the surface interactions and reactivity of ZnO nanoparticles with the room-temperature ionic liquid (IL1) 1-hexyl, 3-methylimidazolium hexafluorophosphate has been studied. Results are discussed on the basis of transmission electron microscopy (TEM) observations, energy dispersive spectroscopy (EDS) analysis, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) determinations. Size and morphology changes in ZnO nanoparticles by surface modification with IL1 are observed. ZnF₂ crystalline needles due to reaction with the hexafluorophosphate anion are also formed.     

Studies on electrowetting of room temperature ionic liquids

This paper reports experimental investigations on the electrowetting behavior of ionic liquids in comparison with aqueous electrolytes, which is one of the important research topics in optofluidics. The effect of applied voltage on the contact angle is reported in detail. In addition, the liquid–solid material interfacial tension and the thickness of insulating layer are estimated under certain conditions. Related conclusions are valuable in the field of future electrowetting applications.     

Co3O4-ZnO hierarchical nanostructures by electrospinning and hydrothermal methods

A new hierarchical nanostructure that consists of cobalt oxide (Co₃O₄) and zinc oxide (ZnO) was produced by the electrospinning process followed by a hydrothermal technique. First, electrospinning of a colloidal solution that consisted of zinc nanoparticles, cobalt acetate tetrahydrate and poly(vinyl alcohol) was performed to produce polymeric nanofibers embedding solid nanoparticles. Calcination of the obtained electrospun nanofiber mats in air at 600 °C for 1 h, produced Co₃O₄ nanofibers with rough surfaces containing ZnO nanoparticles (i.e., ZnO-doped Co₃O₄ nanofibers). The rough surfaced nanofibers, containing ZnO nanoparticles (ZnNPs), were then exploited as seeds to produce ZnO nanobranches using a specific hydrothermal technique. Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were employed to characterize the as-spun nanofibers and the calcined product. X-ray powder diffractometery (XRD) analysis was used to study the chemical composition and the crystallographic structure.     

Modelling interfacial properties of ionic liquids with ePC-SAFT combined with density gradient theory

Highlights

• Combination of ePC-SAFT with density gradient theory

• Calculation of interfacial properties of pure ILs in broad temperature range

• Quantitative predictions of surface tensions for ILs not used in κ parameter fitting

     

Effect of substrates and anions of zinc salts on the morphology of ZnO nanostructures

The ZnO nanostructures were hydrothermally synthesized on glass and Al substrates, respectively, using zinc chloride, zinc nitrate, and zinc acetate as precursor. The as-prepared products were characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Different ZnO nanostructures were obtained, such as nanorods, nanosheets, flower-like nanostructures and so on. The effects of the substrates and anions of zinc salts on the morphologies of the resulting products have been investigated.     

Electroreduction of N-methylphthalimide in room temperature ionic liquids under insonated and silent conditions

The selective electroreduction N-methylphthalimide to 3-hydroxy-2-methyl-isoindolin-1-one has been performed in ionic liquids using phenol as a proton donor under silent and ultrasonic conditions. A significant increase in the rate of electroreduction is shown using ultrasonic activation and in addition high current efficiencies were observed. Some decomposition of the ionic liquid was found to have occurred under exposure to ultrasound.     

Synergic effects of ultrasound and ionic liquids on fluconazole emulsion

The aim of this work was to evaluate the influence of US on the properties of the fluconazole emulsions prepared using imidazolium-based ILs ([C_n C₁im]Br). The effects of the preparation method (mechanical stirring or US), US amplitude, alkyl chain length (of [C₁₂C₁im]Br or [C₁₆C₁im]Br), and IL concentration on the physicochemical properties were evaluated. Properties such as droplet size, span index, morphology, viscosity encapsulation efficiency, and drug release profile were determined. The results showed that US-prepared emulsions had a smaller droplet size and smaller polydispersity (Span) than those prepared by mechanical stirring. Additionally, the results showed that emulsions prepared with [C₁₆C₁im]Br and US had spherical shapes and increased stability compared to emulsions prepared by MS, and also depended on the IL concentration. The emulsion prepared by US at 40% amplitude had increased encapsulation efficiency. US provided a decrease in the viscosity of emulsions containing [C₁₂C₁im]Br; however, in general, all emulsions had viscosity close to that of water. Emulsions containing [C₁₆C₁im]Br had the lowest viscosities of all the emulsions. The emulsions containing the IL [C₁₆C₁im]Br had more controlled release and a lower cumulative percentage of drug release. The IL concentration required to prepare these emulsions was lower than the amount of conventional surfactant required, which highlights the potential synergic effects of ILs and US in preparing emulsions of hydrophobic drugs.     

Electronic structures of imidazolium-based ionic liquids

Electronic structures of ionic liquids formed by 1-buthyl-3-alkylimidazolium ion [C_nmim]⁺ (n = 4 and 8) with various inorganic and organic anions have been investigated by ultraviolet photoemission, X-ray photoemission, inverse photoemission and soft X-ray emission spectroscopies (SXES). The comparison of the calculated density of states with the observed spectra revealed that the molecular orbital energies of these ionic liquids are significantly affected by the electrostatic Madelung potential among the ions. The SXES results clearly show that the both highest occupied and lowest unoccupied states of [C₄mim]⁺PF₆⁻ are derived from the cation as a result of strong Madelung potential. On the other hand, the SXES results show the valence electronic structures of ionic liquids with larger anion molecules, [C_nmim]⁺Tf₂N⁻ and [C_nmim]⁺OTf⁻ are contributed from the both cation and anion.     

Fabrication and characterization of ZnO micro and nanostructures prepared by thermal evaporation

A simple method of thermal evaporation to fabricate micro and nanostructures of zinc oxide was presented. ZnO micro and nanostructures, prepared under different quantity of O₂, were characterized by techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and analytical transmission electron Microscope. The SEM images indicated that the products prepared under the condition of sufficient O₂ were needle-like microrods and the samples synthesized under the condition of deficient O₂ were nanorods and nanowires with very high aspect ratio. The results of XRD and Raman shifts revealed that the ZnO micro and nanostructures synthesized under different quantity of O₂ were both single crystalline with the hexagonal wurtzite structure. The HRTEM images indicated that the ZnO nanowire prepared under the condition of deficient O₂ was single crystalline and grown along the direction of [0 0 1]. Photoluminescence measurement was carried out and it showed that the spectra of ZnO micro and nanostructures prepared under different quantity of O₂ exhibited similar emission features. In addition, the growth mechanism of ZnO micro and nanostructures was preliminarily discussed.     

Synthesis and field emission of patterned ZnO nanorods

A simple and self-catalytic method has been developed for synthesizing finely patterned ZnO nanorods on ITO-glass substrates under a low temperature of 500 °C. The patterned ZnO nanorod arrays, a unit area is of 400 × 100 μm², are synthesized via vapor phase transport method. The surface morphology and composition of the as-synthesized ZnO nanorods are characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The mechanism of formation of ZnO nanorods is also discussed. The measurement of field emission (FE) reveals that the as-synthesized ZnO nanorods arrays have a turn-on field of 3.3 V/μm at the current density of 0.1 μA/cm² and a low threshold field of 6.2 V/μm at the current density of 1 mA/cm². So this approach must have a potential application of fabricating micropatterned oxide thin films used in FE-based flat panel displays.     

Effect of monocationic ionic liquids as electrolyte additives on the electrochemical and thermal properties of Li-ion batteries

The conventional electrolyte system has been compared with the ionic liquid (IL) additive containing electrolyte system at room temperature as well as elevated temperature. In this work, two types of monocationic ILs such as 1-butyl-3-methylpyrrolidinium hexafluorophosphate (Pyr IL) and 1-ethyl-3-methylimidazolium hexafluorophosphate (IMI IL) are added as an additive at two different weight ratios in 1.15 M LiPF₆ (EC/EMC = 3/7 v/v) electrolyte solution, the structural, electrochemical and thermal characteristics of LiNi_0.80Co_0.15Al_0.05O₂ (NCA)/carbon full-cell in different electrolyte formulations have been reconnoitered. X-ray diffraction (XRD) studies have proved that IL as an electrolyte additive does not alter the structural stability of cathode materials after cycling. Under room temperature, Pyr IL additives at 1 wt% and 3 wt% deliver better cycleability than others, with the retention ratios of 93.62% and 92.8%, respectively. At elevated temperature, only 1 wt% Pyr IL additive is giving stable capacity retention ratio of 80.74%. Ionic conductivity and self-extinguishing time (SET) values are increasing with respect to the amount of additive added to the electrolyte. Thermal studies reveal that 3 wt% Pyr IL is favorable regarding the safety of the battery as it shows shifting of peak to higher temperature of 272.10 °C. Among the IL additives evaluated in this study, addition of 1 wt% Pyr IL is the most desirable additive for achieving the best cycling performance as well as thermal behavior of Li-ion batteries.     

Controlled hydrothermal growth of ZnO nanostructures by sequestering the Zn metal ions with the chelating agent EDTA

In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn²⁺ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm.     

新型BrФnsted酸性离子液体的合成与表征

制备了五种对水稳定性好、带-SO3H官能团的磺酸类BrФnsted酸离子液体,用核磁共振(NMR)、红外光谱(IR)、电喷雾质谱(ESI-MS)、热重分析(TG)等表征手段对制备的离子液体进行了表征。结果表明,制备的离子液体与预期设计的结构一致,离子液体纯度大于95%;热重分析发现离子液体具有高的热稳定性和较宽的液态范围,其分解温度均高于300℃;五种离子液体均存在四种离子存在形式,H 可以单独以离子形式存在,并不是通常所认为的仅有两种离子存在形式。另外,研究了离子液体在常用溶剂中的溶解性,发现制备的离子液体易溶于水、甲醇,不溶于乙醚、甲苯和乙酸乙酯。     

Thermodynamic properties of the mixtures of some ionic liquids with alcohols using a simple equation of state

In the present work, we have used a simple equation of state called the GMA EoS to calculate the density of three ionic liquid mixtures including 1-butyl-3-methylimidazolum hexafluorophosphate, [BMIM] [PF₆] + methanol, 1-butyl-3-methylimidazolum tetrafluoroborate, [BMIM] [BF₄] + methanol, and [BMIM] [BF₄] + ethanol at different temperatures, pressures, and compositions. The isothermal compressibility, excess molar volumes, and excess Gibbs molar energy of these mixtures have been computed using this equation of state. The values of statistical parameters show that the GMA EoS can predict these thermodynamic properties very well within the experimental errors. The results show that isothermal compressibility of ionic liquids is lower than alcohols and the effect of temperature and pressure on the isothermal compressibility of ionic liquids is lower than alcohols. The excess molar volumes and excess molar Gibbs energy for these ionic liquid mixtures with alcohols are all negative at various temperatures and pressures over the whole composition range. The results have been interpreted in terms of intermolecular interactions and structural factors of the ionic liquids and alcohols.     

Physicochemical properties of ionic liquids based on imidazolium/pyrrolidinium cations and maleate/phthalate anions

Ionic liquids (ILs) based on imidazolium/pyrrolidinium cations and maleate/phthalate anions can be used as excellent electrolyte materials for electrolytic capacitors. In this study, we synthesized four ILs of this family and investigated their thermal behaviors, ionic conductivities and sparking voltages. The four ILs have high thermal stability for capacitor requirements. The conductivities of imidazolium ILs are slightly higher than those of pyrrolidinium analogs and the conductivities of maleate anion-based ILs are higher than those of corresponding phthalate anion-based ILs. Besides, the long-term thermal stability of imidazolium ILs in conductivity is superior to that of pyrrolidinium analogs. Whereas the long-term thermal stability of phthalate anion-based ILs is better than that of corresponding maleate anion-based ILs. The influence of cationic structure of the ILs on conductivity was analyzed. The temperature dependence of conductivity was also discussed in this work. The Vogel–Tammann–Fulcher (VTF) equation accurately describes the temperature dependence of conductivity for the ILs. In addition, the result of sparking voltage measurement shows that neither Ikonopisov nor Albella model is valid for the ILs.