Influence of Equimolar Concentration on Structural and Optical Properties of Binary Selenides Nanoparticles

Nanoparticles of PbSe, Cu₂Se, and CdSe are prepared for two equimolar concentrations (0.05 M and 0.1 M) by precipitation method at 130°C. The obtained nanoparticles were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV-visible analysis to study the structural, morphological, and optical properties and are discussed in detail.     

Agglomeration behavior of chromia nanoparticles prepared by amorphous complex method using chelating effect of citric acid

Chromia (Cr₂O₃, chromic oxide, Eskolaite) nanoparticles were prepared by amorphous complex method using citric acid as a chelating agent. As a precursor for chromic oxide particle, dried gel with a three-dimensional network consisted of the molar ratio of [citrates]/[chromium ions]=2:1 was prepared. Finally, chromic oxide nanoparticles were formed by calcination of precursor gel at 700 °C for 2 h. Obtained chromic oxide particles were characterized by thermogravimetric and differential thermal analysis, X-ray diffraction, field emission scanning electron microscopy, and Brunauer–Emmett–Teller surface area measurement. It turned out that chromic oxide nanoparticles showed highly agglomerated structure consisted of weakly attached primary particles with each other by van der Waals and capillary adhesive forces. The size distribution of the individual particles was about 20–50 nm. Estimated average particle size from BET surface area was 29.21 nm. The reason for the formation of highly agglomerated structure was discussed.     

Effect of acidity on the glycine–nitrate combustion synthesis of nanocrystalline alumina powder

Nanocrystalline alumina powders were prepared by combustion synthesis using glycine as fuel and nitrate as an oxidizer. The effect of the pH values in the precursor solutions on crystallite sizes, surface areas and morphologies of the synthesized alumina powder has been investigated by X-ray diffractometry, thermal analysis, nitrogen adsorption–desorption, and transmission electron microscopy. With decreasing the pH values in the precursor solutions, the obtained materials could be modified from segregated nanoparticles (pH 10.5) to aggregates of nanoparticles (pH 6.0), and finally to a flaky morphology (pH 2.5). The rates of decomposition, the interaction of coordination as well as the hydrogen bonding of the glycine and the Al-hydroxides species at different pH values were found to be responsible for the generation of flake and/or segregated nanoparticles during auto-ignition reactions. The as-prepared combustion ashes were converted into pure nanocrystalline alumina after calcination at elevated temperatures. The specific surface areas of the products calcined at 800 °C ranged from 96 to 39 m²/g with the pH decreased from 10.5 to 2.5.     

Synthesis and properties of hollow silica nanoparticles

Hollow nanoparticles of silicon dioxide (SiO₂) have been obtained using Cu/SiO₂ core-shell nanoparticles as precursors. An original technique based on heating the precursor nanoparticles to T = 400°C followed by a nanochemical reaction of copper oxide separation from hollow silica particles has been proposed and implemented for the first time. The obtained hollow SiO₂ nanoparticles have been studied by transmission electron microscopy. Mechanisms involved in the formation of hollow silica nanoparticles are discussed.     

Preparation of α-alumina nanoparticles via vapor-phase hydrolysis of AlCl3

A novel alumina precursor, represented as AlO_xCl_y(OH)_z, was prepared in a batch reactor through a vapor-phase hydrolysis of AlCl₃ at 200 °C for 1 min. The precursor particles were spherical and distributed in the size range of 30 to 200 nm, giving a number-average diameter of 70 nm. The precursor particles were calcined at 1200 °C for 6 h to obtain α-alumina nearly 100% in α-transformation degree. The weight loss upon calcination was 40%, comparable to 35% of Al(OH)₃. The surface-area equivalent diameter of the obtained α-alumina particles was calculated to be 35 nm.     

Acalypha indica–mediated green synthesis of ZnO nanostructures under differential thermal treatment: Effect on textile coating,hydrophobicity, UV resistance,and antibacterial activity

In this study, ZnO nanoparticles were green-synthesized from Acalypha indica leaf extract using zinc acetate as a precursor. The prepared ZnO nanoparticles were calcined at three different temperatures, namely 100, 300, and 600?°C. The structure/morphology of the green-synthesized ZnO nanoparticles was ascertained through X-ray diffraction, particle size analysis, scanning electron microscopy, transmission electron microscopy, and surface area analysis techniques. It was observed from the physico-chemical and biological characterization studies that ZnO nanoparticles calcined at high temperature (600?°C) exhibit high surface area (230?m²?g^?1) and small particle size (20?nm) with good antibacterial activity against Escherichia coli (22.89?±?0.06?mm) and Staphylococcus aureus (24.62?±?0.08?mm). In addition, cotton fabrics coated with these nanoparticles showed higher UV-protection (87.8?UPF), hydrophobicity (155°), and maximum zone of bacterial inhibition against E. coli and S. aureus (25.13?±?0.05 mm and 30.17?±?0.03?mm) than those coated with particles calcined at 100?°C and 300?°C. High temperature calcination has a vital role in the crystallization of the particles towards nanoscale with increased resistivity to UV exposure, washing treatments, and microbial infection in fabrics. Thus, the cost-effective ZnO nanoparticles obtained through green synthesis method proves their potential applications in the field of biomedical, textile, and cosmetic applications.     

Characterization and synthesis of KTa0.1Nb0.9O3 particles via high temperature mixing method under hydrothermal conditions

KTa_0.1Nb_0.9O₃ (KTN) particles with an orthorhombic perovskite structure have been synthesized via a high temperature mixing method (HTMM) under hydrothermal conditions. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microcopy (HRTEM). The influence of alkaline concentration and solvent composition on the phase structure and morphology of the obtained powders was investigated. The results show that the well-crystallized KTN powders with sizes of 200–500 nm are successfully prepared at temperatures as low as 240 °C when the KOH concentration is 2.0 M and the isopropanol/water (I/W) volume ratio equals to 100/0.     

Preparation of new antimony(0)/polyaniline nanocomposites by a one-pot solution phase method

The new Sb(0)/PANI nanocomposite was successfully synthesized by a one-pot solution phase method. Sb(0) particles were first prepared by the reduction of SbCl₅ or SbCl₃ using t-BuONa-activated NaH in THF. A ligand exchange with aniline on t-BuONa-stabilized Sb(0) particles yielded aniline-stabilized particles. The Sb(0)/PANI nanocomposite was finally obtained by polymerizing aniline-stabilized Sb(0) particles by using ammonium persulfate. The morphology and the structure of the nanocomposite was examined by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results obtained show that the Sb(0) precursor has a great influence on the size and the crystallinity of Sb(0) nanoparticles dispersed in PANI.     

Synthesis and characterisation of SnO2 nano-single crystals as anode materials for lithium-ion batteries

Rutile structure SnO₂ nano-single crystals have been synthesized using tin (IV) chloride as precursor by the modified hydrothermal method. Controllable morphology and size of SnO₂ could be obtained by adjusting the concentration of the hydrochloric acid. The SnO₂ nanoparticles were characterised by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical methods. The SnO₂ nanoparticles as anode materials in lithium-ion batteries exhibit high lithium storage capacities. The reversible capacities are more than 630 mA h g^− 1.     

Thermal decomposition of β-FeOOH

β-FeOOH particles were prepared by a forced hydrolysis of the 0.1 M FeCl₃ + 5·10⁻³ M HCl solution, whereas sulfated β-FeOOH particles were prepared by forced hydrolysis of the 0.1 M FeCl₃ solution containing 5·10⁻³ M quinine hydrogen sulfate (QHS). β-FeOOH particles, as well as sulfated β-FeOOH particles, were thermally treated up to 600 °C. The samples were characterized using DTA, XRD, FT-IR and TEM. β-FeOOH particles showed a cigar-type morphology, whereas bundles of β-FeOOH needles were obtained in the presence of QHS. Heating of β-FeOOH particles at 300 °C and above yielded α-Fe₂O₃ particles. Specific adsorption of sulfate groups showed a strong effect on the thermal decomposition of β-FeOOH particles. Upon heating of sulfated particles between 300 and 500 °C the formation of an amorphous phase and a small fraction of α-Fe₂O₃ were observed. Needle-like morphology of amorphous particles in these samples was preserved. At 600 °C, α-Fe₂O₃ particles were obtained; however, they were much smaller than those obtained by heating a pure β-FeOOH.     

Molecular design of nanometric zinc borate-containing polyimide as a route to flame retardant materials

Zinc borate (Zn₂B₆O₁₁·3H₂O) nanoparticles were successfully prepared by using an emulsion liquid membrane (W/O/W emulsion) to control the size of particles with Na₂B₄O₇·10H₂O, boric acid and ZnSO₄·7H₂O as raw materials. All materials were dispersed with the polyimide (PI) precursor, poly (amic acid). Using a combination of dissolving the poly (amic acid) and mixing fatty acid surfactant-coated zinc borate nanoparticles; we have demonstrated the formation of nanocomposites with uniform nanoparticles dispersion. We report the first deposition of nanocomposite polyimides from solution using spin-coating. The microstructures and morphology of the as-obtained samples were studied by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA).     

Synthesis of multilayer Nano-ZrO2 coated polystyrene spheres on fabrication of three-dimensional ordered macroporous structures

Monodispersed ZrO₂ precursor nanoparticles with a diameter of 25 nm were successfully synthesized by using diglycol as complexing reagent. The kinetic of particle growth as a function of concentration ratio of ZrOCl₂: diglycol was investigated. The as-synthesized ZrO₂ precursor nanoparticles were homogenously coated on the surface of polystyrene particles. Multilayer coating process was implemented by using poly (acrylic acid) (PAA) to modify the surface charges of the coated spheres, which was characterized by zeta-potential, particles size distribution and microstructural observation. The multilayer-coated polystyrene (PS) spheres have been used as templates to produce macroporous materials. Ordered macroporous ZrO₂ materials were obtained after the ZrO₂ precursor nanoparticles coated PS spheres were formed by centrifugation and calcined at 550°C for 3 h. The porous wall thickness could be well controlled by using the multilayer nano-ZrO₂ coated PS spheres with different coating thickness.     

Preparation of Mn2SnO4 nanoparticles as the anode material for lithium secondary battery

The ultrafine Mn₂SnO₄ nanoparticles with diameters of 5-10 nm have been prepared by thermal decomposition of precursor MnSn(OH)₆. The MnSn(OH)₆ nanoparticles precursor was synthesized by a hydrothermal microemulsion method. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and electron diffraction have been employed to characterize the crystal structures and morphologies of the as-prepared samples. High-resolution transmission electron microscopy observations revealed that the as-synthesized nanoparticles were single crystals. The thermal characterization was studied by differential thermal analysis and thermogravimetry analysis measurements. Electrochemical test showed that the Mn₂SnO₄ nanoparticles exhibited a high initial charge-discharge capacity of 1320 mAh/g.     

Direct synthesis of maghemite,magnetite and wustite nanoparticles by flame spray pyrolysis

Magnetic iron-oxide nanoparticles have been prepared by flame spray pyrolysis (FSP) under controlled atmosphere. This way controlled and direct flame synthesis of Fe₂O₃ (maghemite), Fe₃O₄ (magnetite) and FeO (wustite) particles is possible by a scalable process. The Fe oxidation state was controlled by varying the fuel to air ratio during combustion as well as by varying the valence state of the applied Fe precursor. The as-prepared materials were characterized by electron microscopy, nitrogen adsorption, X-ray diffraction and Raman spectroscopy. Magnetic properties were investigated with SQUID, which unravelled superparamagnetic behaviour for all materials and typical features for the corresponding crystal structures and particle sizes. Maximum magnetisation was achieved for a mixture of maghemite and magnetite.     

Synthesis, characterization and magnetic properties of CoFe2O4 nanorods

In this work, we demonstrated a new precursor route to synthesize CoFe₂O₄ one-dimensional (1D) nanorods. CoFe₂O₄ nanorods were prepared via the thermal decomposition of CoFe₂(C₂O₄)₃ nanorod precursor, which was prepared by solvothermal method without the assistance of template or surfactant. The microstructure and magnetic property of the obtained products were characterized by x-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric (TG) and differential thermal analysis (DTA) and vibrating sample magnetometer (VSM). The results showed that the as-prepared CoFe₂O₄ nanorods were built by magnetic nanoparticles after calcining the precursor nanorods at different temperatures, and the size variation of magnetic nanoparticles with calcination temperatures leaded to variable magnetic properties.     

Solvothermal synthesis and characterization of acicular α-Fe2O3 nanoparticles

Nanometer-sized α-Fe₂O₃ particles have been prepared by a simple solvothermal method using ferric acetylacetonate as a precursor. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDAX), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transition electron microscopy (TEM), infrared spectroscopy (IR) and thermal analysis (TG-DTA). XRD indicates that the product is single-phase α-Fe₂O₃ with rhombohedral structure. Bundles of acicular shaped nanoparticles are seen in TEM images with an aspect ratio ～ 12; typically 8–12 nm wide and over 150 nm long. The α-Fe₂O₃ nanoparticles posses a high thermal stability, as observed on thermal analysis traces.     

Preparation,microstructure and electrochemical performance of nanoparticles LiMn2O3.9Br0.1

LiMn₂O_3.9Br_0.1 nanoparticles were prepared by a room-temperature solid-state coordination method. The structure and morphology of the as-prepared materials were analyzed by X-ray diffractometry and transmission electron microscopy. The results show that the LiMn₂O_3.9Br_0.1 is well-crystallized and consists of monodispersed nanoparticles 80–100 nm in size. Results of electrochemical testing show that the samples prepared at different temperatures have similar electrochemical performance. The initial discharge capacities of LiMn₂O_3.9Br_0.1 prepared at 800 °C and 700 °C are 121 mAh g^? 1 and 118.9 mAh g^? 1, respectively, higher than for LiMn₂O₄ prepared using the same method.     

Synthesis and characterization of vanadium carbide nanoparticles by thermal refluxing-derived precursors

Vanadium carbide (VC) nanoparticles were synthesized by a novel refluxing-derived precursor. The organic/inorganic hybrid precursor was prepared by a two-step refluxing method using hydrous V₂O₅ as vanadium source and n-dodecane as carbon source. The reaction process, phase composition, microstructure, and element composition of VC were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The results showed that VC nanoparticles could be obtained at 900 °C for 1 h in flowing Argon (Ar), which was much lower than those of conventional synthesis methods. XRD pattern indicated that the product was face-centered cubic VC with a lattice constant a = 4.1626 Å and average crystallite size of 22.3 nm. Raman spectra indicated that long time refluxing resulted in alkane dehydrogenation and the formation of coke on V₂O₅ nanoparticles. XPS investigations confirmed oxygen presence in VC lattice. Electron microscopy photographs showed the particle size ranged from 20 to 50 nm. All these results confirmed that the two-step refluxing method was a novel and feasible method to synthesize VC nanoparticles.     

Synthesis and thermal stability of W/WS2 inorganic fullerene-like nanoparticles with core–shell structure

W/WS₂ inorganic fullerene-like (IF) nanoparticles with core–shell structure are synthesized by the reaction of tungsten nanospheres and sulfur at relatively low temperatures (380–600 °C) under hydrogen atmosphere, in which tungsten nanospheres were prepared by wire electrical explosion method. Images of transmission electron microscopy and high-resolution transmission electron microscopy show that the composite particles are of core–shell structure with spherical shape and the shell thickness is about 10 nm. X-ray powder diffraction results indicate that the interlayer spacing of IF-WS₂ shell decreases and approaches that of 2H-WS₂ with increasing annealing temperatures, representing an expansion of 3.3–1.6%. A mechanism of IF-WS₂ formation via sulfur diffusion into fullerene nanoparticles is discussed. Thermal analysis shows that the nanoparticles obtained at different temperatures exhibit similar thermal stability and the onset temperature of oxidization is about 410 °C. Encapsulating hard tungsten core into IF-WS₂ and the spherical shape of the core–shell structures may enhance their performance in tribological applications.     

Structural and spectral investigations of Rhodamine (Rh6G) dye-silica core-shell nanoparticles

Rhodamine (Rh6G) dye-silica core-shell nanoparticles (DSCSNPs) have been prepared by the controlled hydrolysis and condensation of single silica precursor tetraethylorthosilicate (TEOS) using the sol-gel method. Scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis reveal that dye molecules are entrapped in silica (SiO₂) shell resulting into core-shell particles of ∼30 nm diameter. These particles are also characterized by X-ray diffraction and Fourier transforms infrared spectroscopy. The results indicate that core-shell particles are all in spherical shape and have a narrow size distribution. The fluorescent and optical properties of core-shell particles have been investigated using fluorescence and UV-Visible absorption spectra. The photoluminescence in solid or liquid medium occurs at the same wavelength. The SiO₂ shell restricts the leakage and photobleaching of dye efficiently. These core-shell nanoparticles are found to be highly luminescent and stable.