Biosynthesis of titanium dioxide nanoparticles using a probiotic from coal fly ash effluent

The synthesis of titanium dioxide nanoparticle (TiO₂ NP) has gained importance in the recent years owing to its wide range of potential biological applications. The present study demonstrates the synthesis of TiO₂ NPs by a metal resistant bacterium isolated from the coal fly ash effluent. This bacterial strain was identified on the basis of morphology and 16s rDNA gene sequence [KC545833]. The physico-chemical characterization of the synthesized nanoparticles is completely elucidated by energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and transmission and scanning electron microscopy (TEM, SEM). The crystalline nature of the nanoparticles was confirmed by X-RD pattern. Further, cell viability and haemolytic assays confirmed the biocompatible and non toxic nature of the NPs. The TiO₂ NPs was found to enhance the collagen stabilization and thereby enabling the preparation of collagen based biological wound dressing. The paper essentially provides scope for an easy bioprocess for the synthesis of TiO₂ NPs from the metal oxide enriched effluent sample for future biological applications.     

Chitosan as template for the synthesis of ceria nanoparticles

Cerium oxide (CeO₂), nanoparticles were prepared using chitosan as template, cerium nitrate as a starting material and sodium hydroxide as a precipitating agent. The resultant ceria–chitosan spheres were calcined at 350 °C. The synthesized powders were characterized by, XRD, HRTEM, UV–vis, FTIR, and TG-DTA. The average size of the nanoparticles obtained was ∼4 nm and BET specific surface area ∼105 m² g⁻¹. Blueshifts in the ultraviolet absorption spectra have been observed in cerium oxide nanocrystallites. The band-gap was found to be 4.5 eV. The blueshifts are well explained for diameters down to less than a few nanometers by the change in the electronic band structure.     

Vanadium dioxide nanobelts: Hydrothermal synthesis and magnetic properties

VO₂ (B) nanobelts were prepared by a hydrothermal method at 180 °C using V₂O₅·nH₂O sol and H₂C₂O₄·2H₂O as starting agents. The obtained nanobelts have diameters ranging from 50 to 100 nm in width, 20-30 nm in thickness with lengths up to 1.5 μm. Measurements of the static magnetic susceptibility provide evidence for two phase transitions at T₁ = 225 K and T₂ = 290 K, respectively. Below T₁, the data suggest the presence quasi-free as well as of strongly antiferromagnetic correlated spins associated to V⁴⁺-ions.     

Sonochemical synthesis of ZnO nanoparticles: The effect of temperature and sonication power

ZnO nanoparticles were synthesized by drop-wise addition of ZnCl₂ solution to KOH, in different temperatures and sonication output powers. The morphologies and structure of resulting materials were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The morphology of the products was determined to be a mixture of nano rods as well as nanoparticles depending to sonication output power and temperature. A reduction in nanoparticles and aggregates sizes as well as amount of byproducts was observed by increasing the sonication output power. A combination of sonication output power and temperature was also studied on the properties of the product. At 70 °C and 45 W sonication output power, the smallest nanoparticles as well as narrower range of sizes in addition to minimum amount of byproducts was obtained in this work.     

Microwave synthesis of yttria stabilized zirconia

Yttria stabilised zirconia (YSZ) nanocrystals, with a mean size between 5 and 10 nm, were prepared by microwave flash synthesis. Flash synthesis was performed in alcoholic solutions of yttrium, zirconium chloride and sodium ethoxide (EtONa) using a microwave autoclave (RAMO system) specially designed by authors. Energy dispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) transmission and scanning electron microscopy (TEM and SEM) are used to characterized these nanoparticles. Compared with conventional synthesis, nanopowders can be produced in a short period (e.g. 10 s), both high purity and stoechiometric control are obtained. Nevertheless, this mean of production is more cheaper and much faster than the ones commonly used to produce yttria stabilized zirconia (YSZ) by conventional sol-gel techniques.     

Novel hydroxide precursors for low temperature synthesis of selected ternary oxides

A novel method of using hydroxide precursors to reduce the synthesis temperature for few selected ternary oxides has been presented here. This technique is very useful and advantageous when the ternary oxides contain an alkaline earth element. The selected compositions for this method are BaCeO₃ (BC), BaBiO₃ (BB), La_0.7Sr_0.3CoO₃ (LSCO) and BaBi₂Nb₂O₉ (BBN). Commercially purchased strontium (or barium) hydroxide and freshly prepared lanthanum, cobalt, bismuth and niobium hydroxides were mixed thoroughly in stoichiometric ratio and heated at different temperatures ranging from 100 to 700 °C for 10 h for corresponding compositions. The sequence of the reaction and evolution of the product phase were studied by the X-ray diffraction (XRD) studies. The phase purity and lattice parameters were also determined by XRD investigations. All the product phases in each case were formed at relatively low temperature than when they were prepared by co-precipitation or solid state method. The morphology and average particle size of these powders were investigated by scanning electron microscopy (SEM).     

Facile synthesis of highly branched jacks-like ZnO nanorods and their applications in dye-sensitized solar cells

Highly branched, jacks-like ZnO nanorods architecture were explored as a photoanode in dye-sensitized solar cells, and their photovoltaic performance was compared with that of branch-free ZnO nanorods photoanodes. The highly branched network and large pores of the jacks-like ZnO nanorods electrodes enhances the charge transport, and electrolyte penetration. Thus, the jacks-like ZnO nanorods DSSCs render a higher conversion efficiency of η = 1.82% (V_oc = 0.59 V, J_sc = 5.52 mA cm⁻²) than that of the branch-free ZnO nanorods electrodes (η = 1.08%, V_oc = 0.49 V, J_sc = 4.02 mA cm⁻²). The incident photon-to-current conversion efficiency measurements reveal that the jacks-like ZnO nanorods DSSCs exhibit higher internal quantum efficiency (∼59.1%) than do the branch-free ZnO nanorods DSSC (∼52.5%). The charge transfer resistances at the ZnO/dye/electrolyte interfaces investigated using electrochemical impedance spectroscopy showed that the jacks-like ZnO nanorods DSSC had high charge transfer resistance and a slightly longer electron lifetime, thus improving the solar-cell performance.     

A mild solvothermal route to α-Fe2O3 nanoparticles

A mild solvothermal route has been developed to synthesize α-Fe₂O₃ nanoparticles using Fe(NO₃)₃ as a starting material. The results from XRD and TEM indicate the α-Fe₂O₃ powders possess a rhombohedrally centered hexagonal structure, and the size of particles from alcohothermal method at 160 °C is about 50-100 nm.     

CuO urchin-nanostructures synthesized from a domestic hydrothermal microwave method

This letter reports the synthesis of CuO urchin-nanostructures by a simple and novel hydrothermal microwave method. The formation and growth of urchin-nanostructures is mainly affected by the addition of polyethylene glycol (PEG). The hierarchical malachite particles are uniform spheres with a diameter of 0.7-1.9 μm. CuO urchin-nanostructures were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FEG-SEM) and nitrogen adsorption (BET). The specific surface area of the CuO nanostructured microspheres was about 170.5 m²/g. A possible mechanism for the formation of such CuO urchin-nanostructures is proposed.     

In2O3 microcrystals obtained from rapid calcination in domestic microwave oven

The simple way to prepare In₂O₃ microcrystals is reported in this paper. The precursor, In(OH)₃ microstructures, were obtained using the Microwave-Assisted Hydrothermal (MAH) Method. By annealing as-prepared In(OH)₃ precursor at 500 °C for 5 min in a domestic microwave oven (MO), In₂O₃ microcrystals were prepared, inheriting the morphology of their precursor while still slightly distorted and collapsed due to the In(OH)₃ dehydration process which was studied by thermal analysis. The In(OH)₃ and In₂O₃ were characterized using powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. These techniques confirm the chemical dehydration of In(OH)₃ and the formation of In₂O₃ powders. The domestic MO promotes a rapid structural organization as compared with a CF (conventional furnace). The MAH method and the subsequent annealing in a domestic MO were shown to be a low cost route for the production of In₂O₃, with the advantages of lower temperature and smaller time.     

One-pot synthesis of CuFeSe2 cuboid nanoparticles

Ternary semiconducting CuFeSe₂ nanocrystals of a particular shape and size were successfully synthesized using a cost-effective and simple one-pot chemical route. X-ray powder diffraction and field emission scanning electron microscopy results indicated that the as-synthesized CuFeSe₂ comprised cuboid nanoparticles with dimensions of 50–150 nm as well as a tetragonal phase. Elemental analysis yielded an atomic ratio of Cu:Fe:Se of 1:1.06:2.17. The synthesis temperature and the solvent octadecylamine were significant in determining the structural phases and morphologies of the final products. The optimal condition for synthesizing the tetragonal CuFeSe₂ phase with cuboid nanoparticles was a reaction temperature of 200 °C for 1 h in octadecylamine solvent. A possible mechanism of the formation of ternary CuFeSe₂ nanoparticles with controllable shapes is discussed.     

Synthesis and characterization of CuO nanoparticles from liquid ammonia

A new type of CuO nanoparticles were synthesized in liquid ammonia in the presence of sodium metal. First, Cu nanoparticles were obtained by reducing copper nitrate with the alkali metal in liquid ammonia, then, CuO nanoparticles were formed in the ambient conditions. The morphology and structure of as-prepared CuO nanoparticles were characterized by TEM and XRD, and the reason of aggregation of CuO nanoparticles was supposed.     

Facile synthesis of antimony-doped tin oxide nanoparticles by a polymer-pyrolysis method

In this article, antimony-doped tin oxide (ATO) nanoparticles was synthesized by a facile polymer-pyrolysis method. The pyrolysis behaviors of the polymer precursors prepared via in situ polymerization of metal salts and acrylic acid were analyzed by simultaneous thermogravimetric and differential scanning calorimetry (TG-DSC). The structural and morphological characteristics of the products were studied by powder X-ray diffraction (XRD) and transmission electron microscope (TEM). The results reveal that the ATO nanoparticles calcined at 600 °C show good crystallinity with the cassiterite structure and cubic-spherical like morphology. The average particle size of ATO decreases from 200 to 15 nm as the Sb doping content increases from 5 mol% to 15 mol%. Electrical resistivity measurement shows that the resistivity for the 10-13 mol% Sb-doped SnO₂ nanoparticles is reduced by more than three orders compared with the pure SnO₂ nanoparticles. In addition, due to its versatility this polymer-pyrolysis method can be extended to facile synthesis of other doped n-type semiconductor, such as In, Ga, Al doped ZnO, Sn doped In₂O₃.     

Low temperature synthesis of porous copper/zinc oxide

A two-step urea aqueous solution process at a low temperature (90 °C) was employed for the preparation of a copper/zinc oxide material. Well defined porous spherical particles with average sizes of around 5 μm in diameter were prepared first and then used as a support for further copper-zinc precipitation. It was found that the particle composition and shape were changed with applied stirring speed (100 rpm or 200 rpm) and that particle size is inversely proportional to the copper content in the particles. The particles preserved their size and shape after the heat treatment. Prepared Cu/ZnO samples showed catalytic activity for the reaction of steam reforming of methane. Samples were characterized by scanning field emission electron microscopy, energy dispersive X-ray analyses, X-ray powder diffraction, surface area analyses, and atomic absorption spectroscopy.     

Synthesis and characterization of nanocrystalline MgAl2O4 spinel via sucrose process

Nanocrystalline MgAl₂O₄ spinel powder was synthesized using metal nitrates and a polymer matrix precursor composed of sucrose and polyvinyl alcohol (PVA). The precursor and the calcined powders were characterized by simultaneous thermal analysis (STA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to XRD results, the inceptive formation temperature of spinel via this technique was between 600 and 700 °C. The calcined powder at 800 °C for 2 h has faced shaped morphology and its crystallite size is in the range of 8-12 nm. Further studies also showed that the amount of polymeric matrix to metal ions has significant influence on the crystallite size of synthesized magnesium aluminate spinel powder.     

A novel method to low temperature synthesis of nanocrystalline forsterite

Nanocrystalline forsterite (Mg₂SiO₄) powder was synthesized using sucrose as a chelating agent and template material from an aqueous solution of magnesium nitrate and colloidal silica. The synthesized powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), simultaneous thermal analysis (STA), and scanning electron microscopy (SEM). The synthesized nano-powder had particle size smaller than 200 nm and average crystallite size of powders calcined at 800 °C for 3 h was in the range of 10-30 nm. Also the effect of addition 2 and 4 wt.% forsterite seed on nucleation temperature and crystallite size of forsterite was investigated. The presence of small amounts of Mg₂SiO₄ as seed obviously accelerated the crystallization of forsterite. According to DTA results the inceptive formation temperature of Mg₂SiO₄ without any seed was 760 °C, while this temperature for the specimen containing 4 wt.% seed was 700 °C.     

Silver nanoparticles: Large scale solvothermal synthesis and optical properties

Silver nanoparticles have been successfully synthesized by a simple and modified solvothermal method at large scale using ethanol as the refluxing solvent and NaBH₄ as reducing agent. The nanopowder was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible and BET surface area studies. XRD studies reveal the monophasic nature of these highly crystalline silver nanoparticles. Transmission electron microscopic studies show the monodisperse and highly uniform nanoparticles of silver of the particle size of 5 nm, however, the size is found to be 7 nm using dynamic light scattering which is in good agreement with the TEM and X-ray line broadening studies. The surface area was found to be 34.5 m²/g. UV-visible studies show the absorption band at ∼425 nm due to surface plasmon resonance. The percentage yield of silver nanoparticles was found to be as high as 98.5%.     

Large-scale synthesis of ultralong Sb2S3 sub-microwires via a hydrothermal process

This paper describes an ethylene glycol (EG)-assisted approach to the large-scale ultralong Sb₂S₃ sub-microwires, formed by a simple hydrothermal reaction between SbCl₃ and Na₂S in the presence of distilled water. Transmission electron microscopy and scanning electron microscopy studies indicate that these Sb₂S₃ sub-microwires possess a diameter around 200 nm and length up to 100 μm. High-resolution transmission electron microscopy and selected area electron diffraction studies reveal that each Sb₂S₃ sub-microwire is a single-crystal along the [0 0 1] direction. The possible formation mechanism of the sub-microwires was discussed. The effects of volume ratio of EG/water, reaction temperature and the concentration of CO(NH₂)₂ on the morphology of Sb₂S₃ sub-microwires were also investigated.     

Hydrothermal synthesis and magnetic properties of Co0.2Cu0.03Fe2.77O4 nanoparticles

Co_0.2Cu_0.03Fe_2.77O₄ nanoparticles with different morphologies have been synthesized directly via a simple hydrothermal method. The effects of pH value, precursor concentration, reaction temperature and surfactant on the particle size were discussed. X-ray diffraction analyses showed that the as-synthesized Co_0.2Cu_0.03Fe_2.77O₄ nanoparticles possessed typical spinel structure. Scanning electron microscope images showed different morphologies of the particles, including truncated octahedron and octahedron. It was indicated that well-dispersed Co_0.2Cu_0.03Fe_2.77O₄ nanoparticles can be synthesized at pH values ranging from 11 to 13, and reaction temperature of 160 °C. The particle size decreased from 18 to 10 nm after the addition of sodium dodecyl sulphate at the pH value of 9. The magnetic measurement showed that the as-prepared Co-Cu spinel ferrite nanoparticles possessed hard magnetic property.     

Chemical synthesis of α-iron in aqueous FeCl3

Iron-aluminium composite and α-iron powder have been prepared by chemical reduction of aqueous FeCl₃ with aluminium at different conditions. Experiments showed that the concentration of FeCl₃ and aluminium particle size are the main factors to influence the reaction. XRD, SEM and potentiometric titration were employed to characterize the products. SEM showed that as iron particles grow they tend to form spherical seed on the surface of aluminium. XRD revealed that the α-iron was single phase after deposit treatment by NaOH solution. The purity of as-prepared α-iron was 99.5%, as determined from the X-ray fluorescence spectroscopy. The possible formation mechanism is a two-stage red-ox-process: Fe³⁺→Fe²⁺→α-Fe.