Synthesis of iron oxide nanoparticles at low bath temperature: Characterization and energy storage studies

Ferric oxide powders were cathodically electrodeposited at a fixed bath temperature 8 °C. The obtained powders were characterized by X-ray diffraction (XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermogramimetric analysis (TGA). Scanning electron microscopic examination of the resultant powders revealed the formation of iron oxide nanoparticles with a grain size of approximately 20 nm. The adhesive deposit is obtained by reducing bath temperature. The increased adhesion is believed to result from the reducing kinetics energy of molecules and the rate of gas bubbling the electrode surface.     

Photocatalytic degradation of methylene blue by Zn2SnO4-SnO2 system under UV visible radiation

Zn₂SnO₄-SnO₂ system was successfully synthesized by co-precipitation under ultrasonic radiation combined with high temperature calcination. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy and UV–visible absorption spectroscopy revealed the presence of cubic particles mixed with nanoparticles of Zn₂SnO₄-SnO₂ composites which were synthesized from Zn:Sn molar ratios of 1:1 and 3:2. Upon using Zn:Sn molar ratios of 3:1 and 2:1, additional ZnO minor phase was detected. In addition, the calculated pseudo-first-order rate constant of the product synthesized from 3:2 molar ratio of Zn:Sn was the highest at 12.244×10^–3 min^–1.     

Studies on structural,morphological, magnetic and optical properties of chromium sesquioxide (Cr2O3) nanoparticles: Synthesized via facile solvothermal process by different solvents

Chromium sesquioxide (Cr₂O₃) nanoparticles have been successfully synthesized via the facile solvothermal process, by using CrO₃ in different solvents. The as-synthesized nanoparticle sizes are calculated and confirmed to be 25–45 nm, by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The functional groups of the samples were tested by the Fourier transform infrared (FTIR) spectroscopy. Fine and spherical-like morphologies and compositional elements of the products were observed by the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. A weak ferromagnetic (WFM) property was observed for sample by the vibrating sample magnetometer (VSM). The observed band gap values (E_g=4.33–3.54 eV) higher than that of bulk Cr₂O₃ (~3.4 eV) indicated that the particles had been successfully synthesized in the nano region, and measured by ultra-violet visible (UV–vis) absorption spectroscopy. The broad visible emission at ~399 nm, in the photoluminescence spectroscopy revealed the high purity and perfect crystallinity of the samples.     

Evolution of the morphology of Cu films on nanoporous Si pillar arrays

The morphology of nanoporous Si pillar arrays (Si-NPA) prepared by hydrothermal etching was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The results reveal that Si-NPA has a silicon micro/nanometer composite structure, which makes it an ideal template. Si-NPA-based Cu nanocomposite systems (Cu/Si-NPA) were obtained by immersing Si-NPA in 0.01 M CuCl₂ for 1, 5, 10 or 30 min at room temperature. Time-dependent morphological changes and the elemental composition of Cu/Si-NPA were analyzed by SEM, X-ray diffraction (XRD) and X-ray energy-dispersive spectroscopy (EDS). The number and the average size of Cu nanoparticles increased with the immersion time. Besides, Cu/Si-NPA inherited the morphological characteristics of Si-NPA. The results indicate that the morphological evolution of Cu/Si-NPA can be explained by the existence of microscopic electrochemical cells.     

Transition of nanocrystalline In(OH)3 as spherical Indium Oxide nanoparticles embedded platelets

Indium oxide nanoparticles were synthesized by a co-precipitation method using the basic raw materials like Indium (III) Chloride and the precipitating reagent as Ammonium hydroxide. The formation of Indium oxide is highly dependent on temperature. The morphology, structural, particle size, optical and electrical properties of In₂O₃ nanoparticles were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive microscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), UV spectra, Photoluminescence spectroscopic (PL) and Electrical resistance measurements. The results exhibit a crystalline cubic structure in particles, spherical shape, size about 14 nm and optical band gap of 4.20 eV.     

The role of oxidizing agents in the structural and morphological properties of CeO2 nanoparticles

Cerium oxide (CeO₂) nanoparticles with good crystallinity and smooth surface are prepared by chemical precipitation method with different bases (NH₃, NaOH and KOH) using cerium nitrate as a source material. The effect of precipitating agents on the growth of cerium oxide nanoparticles are investigated by Photoluminescence (PL), X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FTIR), thermo gravimetric–differential thermal analysis (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS). Cubic fluorite crystallites are detected by XRD pattern with preferred orientation along (1 1 1) direction. PL spectra revealed the presence of a strong and broad emission band at425 nm due to the blue shift in the visible region. The broad band below 700 cm⁻¹ is due to the envelope of the phonon band of metal oxide (Ce–O) network as revealed by the IR spectra. The TG-DTA curves revealed that the total weight loss of the samples is 19.67% when the samples are heated upto 800 °C. SEM images exhibits weakly agglomerated spheroid crystallites are obtained with the typical size in the range 10–50 nm. TEM images display that the particles are nearly spherical and square in shape with diameter 8–12 nm. XPS spectrum confirms the existence of Ce⁴⁺ oxidation states in CeO₂samples.     

Fabrication of heterojunction SnO2/BiVO4 composites having enhanced visible light photocatalystic activity

SnO₂/BiVO₄ heterojunction composite photocatalysts with various mole ratios have been prepared via a simple hydrothermal method. The structure, composition and optical properties of the SnO₂/BiVO₄ composites were determined by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface analysis, X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). Photocatalytic activities of the composites were evaluated by studying the degradation of methylene blue (MB) solutions under simulated visible light irradiation (500 W halogen tungsten lamp). The 3:7 mol ratio SnO₂/BiVO₄ composite exhibited the highest photocatalytic performance, leading to 72% decompositon of MB within 120 min of irradiation.     

Direct thermal decomposition synthesis and characterization of hematite (α-Fe2O3) nanoparticles

Hematite (α-Fe₂O₃₎ nanoparticles were prepared via direct thermal decomposition method using γ-Fe₂O₃ as a wet chemically synthesized precursor. The precursor was calcinated in air at 500 °C. Samples were characterized by Thermogravimetric analysis (TGA), X-ray diffraction, Infrared, Scanning electron microscopy, Transmission electron microscopy (TEM) and Photon correlation spectroscopy (PCS). TEM and PCS analyses revealed that the average particle size of the α-Fe₂O₃ nanoparticles synthesized at 500 °C are about 18±2 nm and 50±3 nm for 1 h and 24±2 nm and 82±3 nm for 2 h, respectively. The difference in average particle size determined by PCS and TEM analysis is due to the electrostatic forces between particles, and their agglomeration in PCS analysis. Magnetic properties have been detected by a Vibrating sample magnetometry at room temperature. The α-Fe₂O₃ nanoparticles exhibited a weak ferromagnetic behavior at room temperature.     

Structural properties of size-controlled SnO2 nanopowders produced by sol–gel method

SnO₂ nanoparticles were synthesized by sol–gel method with different sol concentrations and the effect of sol concentration on the structural properties of SnO₂ was investigated. The aim of this work is synthesizing of SnO₂ nanoparticles from SnCl₂·2H₂O (tin (II) chloride dihydrate) precursor to obtain high quality powders for using as Li-ion anode material. For this purpose, during the SnO₂ precursor solution preparation, chloride ions were removed from the solution and then the sol–gel synthesis was applied. Produced SnO₂ nanopowders were characterized by x-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive x-ray spectroscopy (EDS) analyses. TG-DTA and FT-IR analysis were performed on the synthesized sol. Grain size, crystal index and lattice strains of SnO₂ particles were calculated. The results showed that the grain size of particles has increased by the increasing of sol concentration, and the crystallinity has been improved. The smallest crystallite size (6.03 nm) was obtained from the SnO₂ sample of 6 mmole concentration sol and maximum size (9.65 nm) from 14 mmole sol according to W–H analysis.     

Synthesis and characterization of sol-processed α-MnO2 nanostructures

Nanostructure of α-MnO₂ was prepared by air oxidation of manganese chloride (MnCl₂) via sol processing by adding N, N-Dimethylformamide (DMF) as surface active material. The obtained material was conventionally annealed at 400 °C for 2 h. The product was characterized by X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The chemical reaction involved in the synthesis of α-MnO₂ nanostructure was proposed and discussed. From XRD pattern, the purity and crystallinity of final product was observed. The synthesized α-MnO₂ nanostructure showed an average crystallite size of 17 nm.     

Effect of preparation techniques on infrared emissivities of Zn0.9Co0.1O powders

Zn_0.9Co_0.1O powders were prepared by chemical solution deposition, solid-state reaction and sol–gel route at different calcination temperatures. The structure and morphologies of samples were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The infrared absorption spectra and infrared emissivities in the range of 8–14 μm were investigated by Fourier transform infrared spectroscopy and IR-2 dual-band infrared emissometer. XRD patterns confirmed the hexagonal wurtzite structure of as-synthesized samples but the peaks of the secondary phase, ZnCo₂O₄, were observed below 1000 °C. Scanning electron micrographs showed large grain sizes of the samples prepared by solid-state reaction and sol–gel processing. The infrared emissivities of samples fabricated by chemical solution deposition and sol–gel route decreased with increasing temperature. Powders obtained using solid-state reaction showed the lowest emissivities, with a minimum value (0.755) at 1150 °C.     

Effect of temperature on crystallite sizes of copper sulfide nanocrystals prepared from copper(II) dithiocarbamate single source precursor

We report the synthesis of CuS nanoparticles using [Cu(butdtc)₂] as single source precursor thermolysed at two different temperatures. The products were characterized by UV–vis absorption spectroscopy, X-ray diffraction, Transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis and atomic force microscopy. The absorption spectra of the CuS nanocrystals are blue shifted and the XRD were indexed to the hexagonal phase of CuS with nanoparticles obtained at 120 °C showing well defined crystalline structure compared to those obtained at 180 °C. Transmission electron microscopy images showed particles that are almost spherical in shapes with average crystallite sizes of 21–38 nm for CuS1 prepared at 180 °C and 3–7 nm for CuS2 prepared at 120 °C and confirms that the chosen reaction temperature determine the crystallite sizes of the nanoparticles.     

Strontium ferrite nanoparticle study: Thermal decomposition synthesis,characterization, and optical and magnetic properties

Monoferrite strontium ferrite nanoparticles were successfully synthesized in the presence of strontium oxalate, [(SrC₂O₄)], as strontium precursor by using solid-state thermal decomposition method. X-ray diffraction study was used to determine phase purity, crystal structure, and average crystallite size of the strontium ferrite nanoparticles. The electrical conductivity measurement of the sintered sample was carried out at 300 °C. Metal nitrates and oxalate precursor without any solvent or surfactant were used in this method; later, they were decomposed at 850 °C for 2 h in a gas mixture of 85% Ar and 15% H₂. The average diameter of the strontium ferrite nanoparticles was 40 nm. The as-prepared strontium ferrite nanoparticles were characterized extensively by techniques like XRD, transmission electron microscope (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM), room temperature photoluminescence (Pl), ultraviolet–visible spectroscopy (UV–vis), and energy dispersive spectrometry (EDS).     

Preparation and characterization of bronze/SiCp composites produced via current activated sintering method

In this study, bronze matrix was reinforced with nickel coated nano SiC particles using mechanical alloying and then subsequent rapid current sintering technique. Mechanical ball milling of bronze matrix composite powders were performed with 1.0, 3.0 and 5.0 vol% SiC nanoparticle reinforcements. The composite powders were cold compacted under constant pressure of 150 MPa. The compacted structures were sintered at atmospheric conditions almost to the full density within 10 min using current sintering, in which the powders were heated by a low voltage and high amperage current and compressed simultaneously to achieve dispersion of nano SiC particles. The samples were sintered at 900 A current to eliminate porosities and agglomeration of particles. The porosity of the produced samples were reduced from 9.49% to 6.13% respectively for the uncoated and coated 5.0 vol% SiC reinforced nanocomposites. Microhardness testing and scanning electron microscopy (SEM) were used for the microstructural characterization of the composites. Rapid sintering was also thought to be an advantage to eliminate volume increment seen under conventional atmospheric sintering conditions.     

Synthesis,characterization, and supercapacitor studies of manganese (IV) oxide nanowires

One-dimensional manganese (IV) oxide (MnO₂) (～20 nm in average diameter) were synthesized by cathodic electrodeposition and heat treatment. The mechanism of electrodeposition and nanowire formation were discussed. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR). Nanowires with varying lengths and diameters were found in TEM and SEM images of the sample. The results of N₂ adsorption–desorption analysis indicated that the BET surface area of the MnO₂ nanowires was 157 m² g^?1 and the pore size distributions were 2.5 and 4.5 nm. The electrochemical performances of the prepared MnO₂ as an electrode material for supercapacitors were evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements in a solution of 0.5 M Na₂SO₄. The higher specific capacitance of 318 F g^?1 and good capacity retention of 86% were achieved after 1000 charge–discharge cycles had been observed for the MnO₂ nanowires electrode.     

Single-step synthesis of activated carbon/γ-Fe2O3 nano-composite at room temperature

Magnetically activated carbon (MAC) nano-composite was synthesized by a simple single-step wet chemical method at room temperature. The structure, surface area, morphology and magnetic properties of as-prepared composite were characterized by X-ray diffraction (XRD), Brunaure–Emmet–Teller analysis (BET), Fourier transform infrared spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry. SEM and TEM analysis indicated that the spherical maghemite (γ-Fe₂O₃) nanoparticles of average particle size 22±2 nm were homogeneously dispersed onto Treated Activated Carbon (TAC). Also, using Scherrer's formula, the average crystallite maghemite nano-particles on the TAC were estimated to be about 19 nm. According to BET analysis, the MAC was of 356 m²/g surface area and 0.36 cm³/g pore volume. The MAC nano-composite exhibited a nearly superparamagnetic property with a saturation magnetization (Ms) of 3.15 A m²/kg. It is suggested that this method could be a more efficient and practical way to produce magnetically modified activated carbon for use as a magnetic adsorbent to remove contaminants.     

Structural,optical and antibacterial properties of nanocrystalline Zn1–xLaxO compound semiconductor

The Zn_1–xLa_xO powders were synthesized by the planetary ball milling method. An accumulated milling time of 15 h with a milling speed of 400 rpm were found to be the optimum milling conditions. The crystal structure, morphology, selected area electron diffraction, and elemental analysis were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The solubility limit of La that could substitute at the Zn sites was only 5 mol% or x=0.05. The dependence of the crystallite size on the La doping content can be explained by the Zener pinning effect. The particle size of the milled ZnO powder was about 34.03 nm and the particle size was reduced to 30.90 nm when doped with 10 mol% La. The particles of all milled samples could agglomerate as a cluster. The largest E_g value of 3.14 eV was obtained from the Zn_0.97La_0.03O powder due to this sample having the smallest crystallite size. The Zn_1–xLa_xO powders can inhibit Staphylococcus aureus better than Escherichia coli due to the presence of an extra lipopolysaccharide layer on the outer surface of the latter.     

Study of diffusion barrier properties of ionized metal plasma (IMP) deposited TaN between Cu and SiO2

The diffusion barrier properties of IMP deposited TaN between Cu and SiO₂ have been investigated in the Cu (200 nm)/TaN (30 nm)/SiO₂ (250 nm)/Si multi-layer structure. The IMP-TaN thin film shows better Cu diffusion barrier properties than chemical vapor deposition (CVD) and conventional physical vapor deposition (PVD) deposited TaN films. The thermal stability was evaluated by electrical measurement and X-ray diffraction (XRD) analysis. As a main part of thermal stability studies, the atomic intermixing, new compound formation and phase transitions in the test structure were also studied. Furthermore, a failure mechanism was also examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), secondary ion mass spectroscopy (SIMS) and Rutherford backscattering spectroscopy (RBS) in conjunction with electrical measurements. The 30 nm thick IMP-TaN was found to be stable up to 800°C for 35 min.     

Thin films of silica imbedded silicon and germanium quantum dots by solution processing

Hydrophilic silicon (0.9 nm) and germanium (2.7 nm) quantum dots (QDs), synthesized utilizing micelles to control particle size, were coated with silica using liquid phase deposition. The use of dodecyltrimethylammonium bromide as a surfactant yielded uniform spheres (Si@SiO₂=57 nm; Ge@SiO₂=32 nm), which could then be arrayed in three dimensions using a vertical deposition method on quartz plates. The silica coated QDs were characterized by UV–visible spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy. The thin films were characterized by UV–visible spectroscopy, scanning electron microscopy, and the measurement of a photocurrent.     

Photocatalytic and antimicrobial activity of NiWO4 nanoparticles stabilized by the plant extract

In recent years, biosynthesis of nanoparticles using plant extract has attracted great attention owing to its cost effective, non-toxic, eco-friendly and as an alternative approach to physical and chemical methods. Nickel tungstate (NiWO₄) nanoparticles were synthesised via the aqueous leaf extract of Azadirachta indica plant. The prepared nanoparticles were characterized using UV–visible diffuse reflectance spectroscopy (UV–vis-DRS), fourier transform infra-red spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. SEM results showed that plant extract modified NiWO₄ (PNT) was composed of tiny sphere in shape. XRD results revealed that the average crystallite size of PNT was smaller (12.12 nm) when compared to the bare NiWO₄ (NT) prepared using precipitation method (31.11 nm). The photocatalytic activity of NiWO₄ nanoparticles were investigated using methylene blue (MB) as a model organic pollutant under visible light irradiation. PNT showed high efficiency for the degradation of MB compared to NT. The effect of operation parameters such as initial dye concentration, pH and catalyst concentration has been investigated in detail. PNT was subjected to antimicrobial studies and significant results were obtained.