Hydrothermal synthesis of sheaf-like CuO via ionic liquids

Sheaf-like CuO consisting of nanoplatelets were synthesized by a hydrothermal method at 100 °C from Cu(NO₃)₂·3H₂O and NaOH in the presence of an ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM]BF₄). The XRD indicated the high crystal quality of CuO with monoclinic crystal structure. FESEM and TEM images showed the nanoplatelets with lengths of 4-5 μm, thickness of 65-80 nm and end angle of 60°. FTIR spectra and TG/DSC curves confirmed the adsorption of [BMIM]BF₄ on the surface of CuO. The morphology of CuO could be controlled by the feeding manner of [BMIM]BF₄. It was demonstrated that [BMIM]BF₄ served as a cosolvent and modifiers in the reaction system. Further, the possible growth mechanism of the sheaf-like CuO was proposed.     

ITO thin films prepared by a microwave heating

ITO thin films were prepared by irradiating 2.45 GHz of microwave with an output power of 700 W using a commercial kitchen microwave oven. A substrate temperature went up and down rapidly between 100 and 650 °C in a minute by a dielectric loss of SnO₂ layer pre-deposited on a glass substrate. We found that the electrical and optical properties of films were affected by the atmosphere in a microwave irradiation, while the sintering was completed within a few minutes. Although the electrical resistivity was not reduced below 5.0 × 10^− 4 Ω·cm in this study, the results lead to the possibility of a practical rapid synthesis of ITO transparent conducting oxide films.     

Synthesis of hierarchical ZnO nanobelts via Zn(OH)F intermediate using ionic liquid-assistant microwave irradiation method

ZnOHF nanobelts (NBs) were synthesized under microwave irradiation in the presence of ionic liquid, 1,2,3-trimethyl-imidazole tetrafluoroborate. The ranges of width, length and thickness of the NBs are ca. 500-800 nm, several micrometers and 100 nm, respectively. Porous polycrystal ZnO NBs with hierarchical structure were obtained after careful heat treatment of the intermediate ZnOHF at 400 °C for 2 h. The structural characters of the ZnO NBs were investigated by XRD, SEM, TEM, HRTEM and XPS measurements, and their absorption and photoluminescence properties were studied as well. The characterization results support the proposed reaction mechanism that the hierarchical ZnO NBs were produced via ZnOHF intermediate and subsequent removal of one of its decomposition products, ZnF₂, by hot water. This may be a facile method to fabricate porous ZnO NBs with hierarchical structure.     

Effects of initial precursor and microwave irradiation on step-by-step synthesis of zinc oxide nano-architectures

ZnO nano-architectures were produced with the aid of a fast, simple and low cost microwave-assisted synthesis method. Solid semispherical ZnO nanoparticles on the order of 600 nm in diameter along with rice-like ZnO nanorods 95 nm thick were produced from butanol, triethanolamine (TEA), and zinc acetate dihydrate. Solid spherical ZnO nano-architectures with an average diameter of 250 nm were produced from the same starting materials in addition to NaOH. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the ZnO nano-architectures as well as the precursor. This method is cheap, fast and simple; capable of producing large quantities of each ZnO nanostructure. Investigation of the step-by-step formation mechanism for each ZnO nanostructure was conducted.     

Crystal structure and aggregation behavior in water of ionic liquid 1-hexadecyl-3-methylimidazolium Bromide

A large-transparent single crystal of 1-hexadecyl-3-methylimidazolium bromide monohydrate ([C₁₆mim]Br·H₂O) with 4-mm length was firstly obtained in the water-trichloromethane-toluene growth system (V_water:V_{trichloromethane}:V_toluene = 0.1:1:2). The crystal structure was determined by single crystal X-ray diffraction method. It crystallizes in the triclinic system, space group P-1, with unit cell parameters a = 5.4962(15) Å, b = 7.839(2) Å, c = 27.279(8) Å, α = 94.375°(4), β = 91.500°(5), γ = 101.999°(4), Z = 2, V = 1145.2(5)ų, Dc = 1.176 Mg/m³, μ = 1.804 mm^− 1, F(000) = 436, the final R1 = 0.0497, wR2 = 0.1154. The 3D supramolecular structure is constructed through the weak interactions between imidazolium cations, Br⁻ anions and lattice water molecules. The long alkyl chain to imidazolium ring and lattice water molecules play an important role in the self-assembled process. Moreover, it is proposed that [C₁₆mim]Br has the aggregation behavior in water at the higher concentration and the possible self-assembled structure is the interdigitated pattern.     

Shape-controlled synthesis of cobalt oxide nanocrystals using cobalt acetylacetonate

Cobalt oxide nanocrystals (NCs) with different morphologies have been successfully synthesized through the decomposition of cobalt (II) acetylacetonate (Co(acac)₂) in nonpolar solvent. The growth temperature of NCs was set at 30 °C lower than the nucleation temperature to prepare monodisperse NCs. By tuning the injection speed of paraffin oil, CoO nanoparticles and nanoflowers have been obtained, respectively. The variation in ligand concentration changing speed due to different injection speed of extra paraffin oil is supposed to be the reason for the formation of CoO NCs with different nanostructures. The structure and shape properties of as-synthesized cobalt oxide NCs have been studied and characterized using XRD and TEM.     

Double layer micellar stabilization of gold nanocrystals by greener ionic liquid 1-butyl-3-methylimidazolium lauryl sulfate

We report the first synthesis of anisotropic gold nanocrystals (AuNC) prepared by a seeding approach using the greener ionic liquid, 1-butyl-3-methylimidazolium lauryl sulfate, [BMIM] [C₁₂H₂₅OSO₃]. Crystal growth was successfully achieved by successive addition of growth solution containing HAuCl₄ and ascorbic acid to 2.5-nm Au seeds. These nanocrystals were stabilized by the ionic liquid via a two layer micellar formation. SEM and TEM results showed Au nanocrystals with particle sizes ranging from 20 to 50 nm. Selected-area electron diffraction (SAED) and PXRD pattern gave indices that correspond to Au nanocrystals. Direct addition of ionic liquid to Au seeds in 3:1 volume ratio afforded the formation of Au nanoparticles. TEM image and UV-vis data revealed the formation of 20-50 nm Au nanocrystals. These results show that the greener ionic liquid, [BMIM] [C₁₂H₂₅OSO₃], is a suitable reaction medium for the direct synthesis of larger Au nanoparticles from Au seeds.     

Hydrothermal synthesis of CdSe hierarchical dendrites using ionic liquid as template

Well-defined CdSe hierarchical dendrites have been synthesized through a facile and effective hydrothermal method. The as-formed CdSe dendrites possess good dispersity and have an average length of about 1 μm along the trunk. Most importantly, it is found that long-chain ionic liquid [C₁₆mim]Cl (1-hexadecyl-3-methylimidazolium chloride), which can adsorb on the (002) plane of wurtize CdSe driven by the coulomb force, serves as an effective template and plays a critical role for the morphology of the product. Furthermore, the UV-vis spectrum of the CdSe dendrites displays absorption maxima at 296 nm; therefore, the obtained CdSe dendrites might have promising application in blue emitters, gas sensors, and light-emitting devices.     

Rapid synthesis of TiO2 hollow nanostructures with crystallized walls by using CuO as template and microwave heating

In this paper, TiO₂ hollow nanostructures with anatase walls have been rapidly fabricated by using CuO as template and microwave heating. These TiO₂ hollow nanostructures have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Experimental results showed that the TiO₂ shell transformed from amorphous to anatase phase in 3 min, induced by the hot CuO core under microwave irradiation. The diameter of TiO₂ hollow nanostructures is about 50-80 nm, and the length is about 200-300 nm. The thickness of the shell is about 3 nm. This method is promising to be used to synthesize other nanomaterials with a hollow nanostructure.     

Release of components from a plastic container during microwave heating

A thermoformed, microwavable container made from a polypropylene/Saran®/polypropylene coextruded material was selected as the test container. Samples of the specimen were microwaved in sealed glass vials for periods ranging from 3 to 7 min. After heating, the head space of the vials was sampled and analysed. The microwaving process was carried out in an Amana Radarange® microwave oven on full power. Sample surface temperature as a function of microwaving time and the quantitative identification of volatile compounds released by the polymer during microwaving were determined. Five major components were detected and quantified in the head space of the vial using gas chromatography. The quantity of each component increased with increased microwaving time. Using mass spectrometry, the five components were identified; four were hydrocarbons and the fifth was butylated hydroxytoluene (BHT). Release of organic components during brief microwaving of polymers may be a near-the-surface phenomenon.     

Electrochemical deposition and characterization of cupric oxide thin films

Polycrystalline cupric oxide (CuO) thin films are deposited using an alkaline solution bath employing cathodic electrodeposition method. Thin films are electroplated at various bath temperatures onto conducting indium tin oxide coated glass substrates. The bath temperature effects on the structural, optical and morphological properties of copper oxide films are studied and reported. X-ray diffraction studies revealed mixed phases of monoclinic and cubic for films grown at lower bath temperatures and that the deposited films at temperatures optimized as 75 °C exhibited cubic structure with preferential orientation along a (111) plane. Texture coefficient (T_c) values are calculated for all diffraction lines and the films were highly textured (T_c > 1). The surface morphology and surface roughness are estimated using scanning electron microscopy and atomic force microscopy, respectively and a morphology made up of pyramid shaped grains is presented. Energy dispersive analysis by X-rays revealed that the near stoichiometric CuO thin films are obtained at optimized preparative parameters. The refractive index is calculated using the envelop method. Also, the optical constants of CuO thin films such as complex dielectric constant (ε) and extinction coefficient (k) are also evaluated and reported.     

A novel route for the synthesis of indium nanoparticles in ionic liquid

In this paper, we report a novel preparation of indium nanoparticles by the reduction of indium chloride in ionic liquid by methanolic solution of NaBH₄. The particles are characterized by means of transmission electron microscopy (TEM), X-ray diffraction and UV-visible studies indicated that the powder consist of the cubic phase of indium. The particle size of indium nanoparticles is in the range of 20 nm mean diameter by Transmission electron microscopy (TEM). The samples display a strong surface plasma absorption band at 231 nm, which indicates that the sample is metal indium and the particle size is less than 20 nm. The thermal analysis of the sample indicate indium not indium oxide. Electrochemical studies show that indium nanoparticles have very good electrical properties.     

Single step synthesis of indium tin oxide by ultrasonic spray and microwave assisted pyrolysis

Ultrafine indium tin oxide (ITO) powders were successfully synthesised by the combined methods of ultrasonic spray and microwave assisted pyrolysis, which is a single step, facile, rapid and continuous method without post-heating treatment. Crystallinity, morphology and microstructure of the samples were investigated by X-ray diffractometer, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscope, selected area electron diffraction pattern and laser grain size analyser. Results indicate that pure solid solution ITO ultrafine powders with homogeneous and narrow size distribution, highly dense and smooth surface morphology can be obtained under optimum conditions. Each uniform spherical particle consisted of many smaller crystallites with diameter of <10 nm.     

Microwave-assisted ionic liquid preparation and characterization of cellulose/calcium silicate nanocomposites in ethylene glycol

Preparation of cellulose-based nanocomposites by microwave-assisted ionic liquid method allows the high value-added applications of cellulose by combining three major green chemistry principles: using environmentally preferable solvents, environmentally friendly method and renewable biomaterials. In this paper, we report the microwave-assisted ionic liquid method for the fast controlled synthesis of the cellulose/calcium silicate nanocomposites by using the microcrystalline cellulose, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethylene glycol. The calcium silicate nanoparticles were homogeneously dispersed in the cellulose matrix. The experimental results showed that the additive of ionic liquid favored the composite of cellulose and calcium silicate. The weight loss of nanocomposites was decreased with the increasing ionic liquid concentrations. The influences of heating times, heating temperatures, and ionic liquid concentrations on the products were investigated. This method is fast, environmentally friendly and suitable for the large-scale production of cellulose-based nanocomposites.     

Synthesis and photocatalytic behaviour of 3D flowerlike bismuth oxide formate architectures

By virtue of structural understanding, bismuth oxide formate (BiOCOOH) was first put forward to be a novel photocatalyst candidate. 3D flowerlike architectures have been successfully synthesized through a facile and economical route, which was free from any surfactant and template. The product was characterized by the study of X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM) and electron diffraction (ED), and the crystal structure of BiOCOOH was revealed. Besides, the formation mechanism of the BiOCOOH flowerlike architectures was also discussed. From the results of photocatalytic tests, the synthesized BiOCOOH architectures exhibited excellent photocatalytic activity for rhodamine-B (RhB) degradation under the simulated solar light irradiation. Therefore, this novel 3D flowerlike BiOCOOH architectures show significance of potential application in environment protection problems.     

A task specific basic ionic liquid for synthesis of flower-like ZnO by hydrothermal method

Flower-like ZnO morphology, with different shapes, have been successfully synthesized via a novel and environment-friendly hydrothermal method using zinc acetate and a task specific dicationic dibasic ionic liquid, [mmpim]₂[OH]₂, which plays an important role in fabrication of ZnO structure. The structure and morphology of the product were characterized by X-ray diffraction and scanning electron microscopy, which show different flower-like morphologies. Photoluminescence spectrum of the product exhibits a strong ultraviolet emission at 391 nm and two weak blue-green emissions at about 450 and 500 nm.     

Carbothermic reduction roasting for processing of ferruginous chromite ore using conventional and microwave heating

The present study investigates the recovery of chromite from a low-grade ferruginous ore through the carbothermic magnetization route using conventional and microwave heating sources. The carbothermic magnetization of ore is studied in both a horizontal tube furnace and a microwave oven by varying different process variables. The main objective of the study is to enhance the magnetic susceptibility of iron-bearing gangue minerals to enable the separation in a magnetic field. Alteration of crystalline structure and magnetic property of these minerals enables separation of low-grade ore by using magnetic separation. It is found that low-grade ferruginous chromite ore can be upgraded by reduction roasting, and 61.2% Cr₂O₃ was recovered with a chromium-to-iron ratio of 1.93 from a feed chromium-to-iron ratio of 1.01. The optimum result is achieved at a roasting temperature of 800 °C, with a roasting time of 60 min and a reductant dosage of 7.5%. Similarly, under microwave radiation, the chromium-to-iron ratio was upgraded to 1.81 with a recovery of 22%Cr₂O₃. The optimum result achieved under microwave radiation is at a microwave power of 900 W and exposure time of 7.5 min, with a reductant dosage of 10%. The findings of these two processing routes are discussed through characterization tools.     

Rapid synthesis of Ag@Ni core-shell nanoparticles using a microwave-polyol method

Mixtures of AgNO₃ and NiSO₄·6H₂O, NiCl₂·6H₂O, or Ni(NO₃)₂·6H₂O were reduced in ethylene glycol (EG) in the presence of NaOH and poly(vinylpyrrolidone) (PVP) under microwave (MW) heating for 10 min. Then, we succeeded in the synthesis of Ag core-Ni shell nanoparticles, denoted as Ag@Ni, in high yield. The formation of Ag@Ni particles was confirmed using energy dispersed X-ray spectroscopic (EDS) measurements and selected area electron diffraction (SAED) patterns. The growth mechanism of Ag@Ni is discussed. The UV-Vis spectra of Ag@Ni were similar to those of Ni particles.     

Development of novel metallic glass/polymer composite materials by microwave heating in a separated H-field

Using a single mode 915 MHz applicator, we fabricate novel Cu₅₀Zr₄₅Al₅ metallic glass/polyphenylene sulfide (PPS) composites with high relative densities by microwave processing the constituents in a separated H-field with an applied pressure of about 5 MPa. The heating behaviors and structural changes of the composites have been investigated. A good bonding state between metallic glassy and PPS particles is found. The gradient structure is also induced by microwave heating of the composites with a high fraction of PPS phase.