Synthesis and characterization of CdS nanoparticles in the presence of oleic acid as solvent and stabilizer

Oleic acid (OA)-capped CdS nanoparticles (NPs) have been successfully synthesized via the direct reaction of Cd(CH₂COO)₂·2H₂O with S powder in OA solvent at 230 °C under nitrogen flow, which was a kind of clean and air-stable solvent. The morphologies and structures of the as-synthesized CdS NPs are examined by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Fourier transform infrared (FTIR) spectroscopy, and the typical Ostwald ripening growth mechanism is concluded. Moreover, the collected ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) spectroscopy demonstrate good optical properties of CdS NPs.     

Decorating graphene sheets with Pt nanoparticles using sodium citrate as reductant

In this paper, we proposed a novel and green approach for the synthesis of graphene nanosheets (GNS) and Pt nanoparticles-graphene nanosheets (Pt/GNS) hybrid materials, employing graphene oxide (GO) as precursor and sodium citrate as environmentally friendly reducing and stabilizing agent. The microstructures of GO and Pt/GNS were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) and electrochemical measurements. The results confirmed that the uniform size distribution of Pt nanoparticles on the surface of GNS without agglomerates could be easily obtained via using sodium citrate as reductant, moreover the Pt/GNS hybrids exhibited high electrochemical activity.     

Synthesis of LiCoPO4 as a cathode material for lithium-ion battery by a polymer method

A polymer method has been used to synthesize high operation voltage LiCoPO₄ cathode material. Thermogravimetric analysis and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM),galvanostatic charge–discharge test and cyclic voltammetry (CV) are used to study the LiCoPO ₄ . The results show LiCoPO₄ has a well-crystallized olivine structure with submicron size. In the range of 3.0–5.1 V, the initial discharge capacities of polymer material are 97.3, 91.5, and 86.5 mAh g^?1 at 0.1, 0.2. and 1 C, respectively. Thus, the polymer method has a great potential in preparing electrode materials for lithium-ion batteries.     

Structural and optical characterization of CdS nanoparticles prepared by chemical precipitation method

In the present study we have synthesized CdS semiconducting quantum dots by the chemical precipitation method using Thioglycerol as the capping agent. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) are employed to characterize the size, morphology and crystalline structure of the as-prepared material. The synthesized QPs have a mixture of cubical and hexagonal crystal symmetry with 12 nm average diameter. Ultraviolet-visible (UV-vis) absorption spectroscopy is used to calculate the band gap of the material and blue shift in absorption edge. Confinement of the optical phonon modes in the QPs is studied by Raman spectroscopy, while FTIR for identification of chemical bonds in the nanomaterial. Multiple cadmium and sulphur defects were observed by employing the photoluminescence (PL) method.     

Synthesis of ZnO nanoparticles using surfactant free in-air and microwave method

Zinc oxide nanoparticles have been successfully prepared by a facile route involving the reaction of zinc sulphate heptahydrate and sodium hydroxide through drop-by-drop mixing synthesis-IA, instant mixing synthesis-IA and under the influence of microwave radiations. The synthesis under different reaction conditions played an important role and led to the formation of zinc oxide nanoparticles of different size and shapes. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The concentration dependent antimicrobial activity of synthesized ZnO nanoparticles was carried out. The photocatalytic activity was evaluated using the photodegradation of methylene blue (MB) dye under UV irradiation. Further, the optical properties of as-prepared ZnO nanoparticles were investigated by UV-vis spectrophotometry. The absence of surfactant led to a simple, cheap and fast method of synthesis of zinc oxide nanoparticles.     

Microwave-assisted fractional precipitation of magnetite nanoparticles using designed experiments

In this study, highly pure magnetite nanoparticle dispersed in water and an organic solvent (n-hexane) and its powder form were prepared in laboratory scale by the fractional precipitation using ammonium hydroxide and microwave heating in the presence of linoleic acid as capping agent. In order to overcome the oxidation of Fe²⁺ during magnetite formation ferrous ammonium sulfate, sodium azide, and fractional precipitation technique were used. The Fe₃O₄ products were investigated by XRD, LLS, EDX, TEM, viscosity measurements, and chemical analysis. The effects of seven main factors on the average diameter of magnetite particles were studied by a screening design. The analysis of the samples showed that this new modified method is able to produce pure magnetite particles in the range of 1–15 nm. The most important factors on the particle size reduction of magnetite were found to be the capping agent used and the pH of solution at the end of precipitation process. Data analysis was performed using Qualitek-4 and Minitab softwares.     

Synthesis of nanoparticles of CoxFe(3−x)O4 by combustion reaction method

Nanocrystalline magnetic particles of Co_xFe_(3−x)O₄, with x ranging from 0.79 to 1.15, has been synthesised by combustion reaction method using iron nitrate Fe(NO₃)₃.9H₂O, cobalt nitrate Co(NO₃)₂·6H₂O, and urea CO(NH₂)₂ as fuel without template and subsequent heat treatment. The process is quite simple and inexpensive since it does not involve intermediate decomposition and/or calcining steps. The maximum reaction temperature ranged from 850 to 1010 °C and combustion lasted less then 30 s for all systems. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of CoFe₂O₄. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures phase purity. The average crystallite sizes determined from the prominent (3 1 1) peak of the diffraction using Scherre's equation and TEM micrographs consisted of ca. 27 nm in spherical morphology. FTIR spectra of the as-prepared material showed traces of organic and metallic salts byproducts. However, when the same material was washed with deionised water the byproducts were rinsed off, resulting in pure materials. Magnetic properties such as saturation magnetisation, remanence magnetisation and coercivity field measured at room temperature were 48 emu/g, 15 emu/g and 900 Oe, respectively.     

Structure of a metaphosphate glass by magnetic measurements

We compare the EPR spectra of a glassy material x CuO (1 ? x)Na₂O P₂O₅ with a crystal 0.5 CuO 0.5 Na₂O P₂O₅ of known structure. This gives us a mean of defining the copper atom in its site.     

One-pot reaction to synthesize superparamagnetic iron oxide nanoparticles by adding phenol as reducing agent and stabilizer

An improved thermal decomposition method was used to directly prepare water-soluble Fe₃O₄ magnetic nanoparticles (MNPs) with relatively higher quality via reductive decomposition of ferric acetylacetonate [Fe(acac)₃], in the presence of benzyl ether and phenol, in which inexpensive phenol acted as reducing agent and stabilizer, produce the semi phenol-benzoquinone coated on the Fe₃O₄ and make the Fe₃O₄·MNPs water-soluble and the colloidal solution stable. By changing the molar ratio of phenol to Fe(acac)₃ and reaction time, the size of Fe₃O₄·MNPs could be varied from 19.3 ± 4.4 nm to 9.7 ± 1.5 nm, with the saturation magnetizations in the range of 51.3–62.9 emu/g.     

Synthesis and TL glow curve analysis of BaSO4:Eu,Dy phosphor

The polycrystalline samples of Ba_1?x?ySO₄:Eu_x,Dy_y (0≤x≤1, 0≤y≤1) have been prepared using the chemical co-precipitation technique. The thermoluminescence (TL) sensitivity of the samples have been found changing with the value of x and y and the highest TL intensity is for Ba₉₆SO₄:Eu₀₂,Dy₀₂. The sample has been characterised by x-ray diffraction (XRD). The samples are found to have orthorhombic structure. For TL analysis Ba₉₆SO₄:Eu₀₂,Dy₀₂ is annealed at different temperatures ranging from 873 to 1173 K. Kinetic parameters of all the TL glow curves of Ba_1?x?ySO₄:Eu_x,Dy_y for different values of x and y and also for the TL glow curves Ba₉₆SO₄:Eu₀₂,Dy₀₂ annealed at different temperatures have been found out using computerised glow curve deconvolution (CGCD) method. The activation energy for the most intense TL peak at (444–453 K) is found out to be 1.26 eV and order of kinetics is 1.35.     

Synthesis and characterization of MnWO4 nanoparticles encapsulated in mesoporous silica SBA-15 by fast microwave-assisted method

The MnWO₄ nanoparticles encapsulated in mesoporous silica (MnWO₄/SBA-15) was successfully synthesized by a fast microwave-assisted method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption–desorption isotherm, and Fourier transform infrared spectroscopy (FTIR). Our results showed that the MnWO₄/SBA-15 nanocomposites have the ordered hexagonal meso-structure of SBA-15, indicating MnWO₄ nanoparticles were successfully distributed into the channels of SBA-15. The size of MnWO₄ nanoparticles in SBA-15 is significantly smaller than the size of MnWO₄ nanoparticles prepared without SBA-15, indicating that the MnWO₄/SBA15 nanocomposites would be very promising for improving photocatalytic activity of MnWO₄ nanoparticles.     

Synthesis of LiFePO4-C cathode materials using a green and low-cost method

LiFePO₄-C was prepared by the solid-state reaction using LiH₂PO₄, Fe₂O₃, and glucose as raw materials, which is a green and low-cost method. Thermogravimetry, differential scanning calorimetry, X-ray diffraction, and element analyzer were used to study the phase and carbon content of the synthesized samples. The optimum conditions for synthesizing LiFePO₄ are identified. The discharge capacity of 120 mAh g⁻¹ was achieved at a current density of 100 mA g⁻¹ between 2.5 and 4.2 V during the first 50 cycles.     

Synthesis of nanoparticles using a pulsed electrical discharge in a liquid

We used a pulsed electrical discharge in a liquid to obtain Cu-, WC-, and ZnO-containing nanoparticles. The effect of the discharge current and pulse duration on the morphology and phase composition of the synthesized material was studied by spectrophotometry, transmission electron microscopy, and x-ray diffraction analysis. We discuss possible mechanisms for nanoparticle formation in a discharge submerged in a liquid. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 111–120, January–February, 2008.     

Preparation of superparamagnetic magnetite nanoparticles by reverse precipitation method: Contribution of sonochemically generated oxidants

Magnetic iron oxide nanoparticles were successfully prepared by a novel reverse precipitation method with the irradiation of ultrasound. TEM, XRD and SQUID analyses showed that the formed particles were magnetite (Fe₃O₄) with about 10 nm in their diameter. The magnetite nanoparticles exhibited superparamagnetism above 200 K, and the saturation magnetization was 32.8 emu/g at 300 K. The sizes and size distributions could be controlled by the feeding conditions of FeSO₄ · 7H₂O aqueous solution, and slower feeding rate and lower concentration lead to smaller and more uniform magnetite nanoparticles. The mechanisms of sonochemical oxidation were also discussed. The analyses of sonochemically produced oxidants in the presence of various gases suggested that besides sonochemically formed hydrogen peroxide, nitrite and nitrate ions contributed to Fe(II) ion oxidation.     

Synthesis and characterization of NiMn2O4 nanoparticles using gelatin as organic precursor

Nanoparticles of NiMn₂O₄ were successfully obtained by mixing gelatin and inorganic salts NiCl₂·6H₂O and MnCl₂·4H₂O in aqueous solution. The mixture has been synthesized at different temperatures and resulted in NiMn₂O₄ nanoparticles with crystallites size in the range of 14–44 nm, as inferred from X-ray powder diffraction (XRPD) data. We have also observed that both the average crystallite size and the unit cell parameters increase with increasing synthesis temperature. Magnetic measurements confirmed the presence of a magnetic transition near 110 K.     

Synthesis and characterization of manganese ferrite nanoparticles by thermal treatment method

Cubic structured manganese ferrite nanoparticles were synthesized by a thermal treatment method followed by calcination at various temperatures from 723 to 873 K. In this investigation, we used polyvinyl pyrrolidon (PVP) as a capping agent to control the agglomeration of the nanoparticles. The characterization studies were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average particle sizes of manganese ferrite nanoparticles were determined by TEM, which increased with the calcination temperature from 12 to 22 nm and they had good agreement with XRD results. Fourier transform infrared spectroscopy confirmed the presence of metal oxide bands at all temperatures and the absence of organic bands at 873 K. Magnetic properties were demonstrated by a vibrating sample magnetometer, which showed a super-paramagnetic behavior for all samples and also saturation magnetization (M_s) increases from 3.06 to 15.78 emu/g by increasing the calcination temperature. The magnetic properties were also confirmed by the use of electron paramagnetic resonance spectroscopy, which revealed the existence of unpaired electrons and also measured peak-to-peak line width, resonant magnetic field and the g-factor.     

Synthesis of silver nanoparticles by sonogalvanic replacement on aluminium powder in sodium polyacrylate solutions

The process of the formation of silver nanoparticles (AgNPs) via the method of galvanic replacement (GR) of Ag⁺ with aluminum powder in sodium polyacrylate (NaPA) solutions in the ultrasonic (US) field has been studied. It was observed, that the yellow colloidal solutions of stabilized AgNPs with the absorption maximum at ∼ 410 nm were obtained under the application of US power by 20 W and frequency by 20 kHz in the wide range of AgNO₃ and NaPA concentrations (0.1 – 0.5 mM and 0.5 – 5.0 g/L respectively) at 25 ⁰C. It was shown, that the GR process under US field occurs without of the significant induction period. Using the UV–vis spectroscopy the kinetics of AgNPs formation has been studied and it was observed the first order kinetics with respect to Ag⁺ ions both for the nucleation and growth processes. It was found that observable rate constants of nucleation are close for the all experimental conditions but the observable rate constants of growth decreased with increasing of initial concentration of AgNO₃. Based on the obtained kinetic data it was proposed a mechanism of the formation of AgNPs consisted of the following two main stages: 1) the nucleation with the formation of primary nanoclusters (AgNCs) on aluminum surface followed by their ablation from the surface of the sacrificial metal by ultrasound into bulk of solution; 2) the transformation of AgNCs in AgNPs via growth from the Al surface and / or agglomeration of AgNCs. Using TEM it was found that the size of obtained AgNPs does not exceed of 25 nm and slightly depends on the initial concentrations of precursors. High antimicrobial activity of obtained colloidal solutions against gram-negative and gram-positive bacteria as well as against fungi was observed.