Synthesis and sintering of tin-doped indium oxide nanoparticles with uniform size

The urea-based hydrothermal (UBH) method can synthesize indium tin oxide (ITO) nanopowders with good monodispersity and size uniformity. However, the resulting formation of high pressure CO₂ gas by the hydrolysis of urea during the hydrothermal process is unsafe. The pressure generated by the UBH method can be lowered by connecting the hydrothermal reactor to a vessel containing sodium hydroxide solution to quickly absorb CO₂ gas. ITO nanoparticles with particle sizes of 90 ± 3 nm and 40 ± 3 nm can be produced. The size of the as-prepared nanoparticles is readily controlled by adjusting the precursor concentration. Using properly mixed nanoparticles with a volume ratio of V_40 nm:V_90 nm = 30:70 as the raw materials, ITO can be sintered to a high and consistent density of 99.3–99.5% of the theoretical density.     

Synthesis of nanocrystalline MMoO4 (M = Ni,Zn) phosphors via a citrate complex route assisted by microwave irradiation and their photoluminescence

Nanocrystalline MMoO₄ (M = Ni, Zn) phosphors, which have wolframite-type structure, were successfully synthesized at low temperatures via a modified citrate complex route assisted by microwave irradiation. The citrate complex precursors were heat-treated from 300 to 600 °C for 3 h. Crystallization of the MMoO₄ (M = Ni, Zn) nanocrystallites were detected at 500 °C, and entirely completed at a temperature of 600 °C. The nanoparticles presented primarily dispersed and homogeneous morphology with particle size of 20–40 nm. The nanocrystalline MMoO₄ (M = Ni, Zn) phosphors prepared at 600 °C exhibited broad luminescence in green and blue wavelength region, respectively.     

Statistical optimization of experimental parameters for synthesis of manganese carbonate and manganese oxide nanoparticles

Taguchi robust design was used for optimization of direct precipitation reaction conditions in order to simple and fast synthesis of manganese carbonate nanoparticles. Manganese carbonate nanoparticles were synthesized in this study by addition of manganese ion solution to the aqueous carbonate reagent. Effects of several reaction variables, such as manganese and carbonate concentrations, flow rate of reagent addition and temperature on particle size of prepared manganese carbonate were investigated. The significance of these parameters in tuning the size of manganese carbonate particles was quantitatively evaluated by analysis of variance. The results showed that manganese concentration and carbonate concentration in the solutions and also flow rate have significant effects in preparation of manganese carbonate nanoparticles. Also, optimum conditions for synthesis of manganese carbonate nanoparticles via precipitation reaction were proposed. Analysis of variance showed that under the optimum condition, the size of manganese carbonate nanoparticles will be about 54 ± 12 nm. In another part of this study, solid state thermal decomposition reaction of precursor was used for preparation of Mn₂O₃ nanoparticles. The results showed that Mn₂O₃ nanoparticles synthesized via thermal decomposition of manganese carbonate nanoparticles have average size of 90 nm.     

Synthesis of MSnO3 (M = Ba,Sr) nanoparticles by reverse micelle method and particle size distribution analysis by whole powder pattern modeling

Light-to-electricity conversion efficiency in dye-sensitized solar cells critically depends not only on the dye molecule, semiconducting material and redox shuttle selection but also on the particle size and particle size distribution of the semiconducting photoanode. In this study, nanocrystalline BaSnO₃ and SrSnO₃ particles have been synthesized using the microemulsion method. Particle size distribution was studied by whole powder pattern modeling which confirmed narrow particle size distribution with an average size of 18.4 ± 8.3 nm for SrSnO₃ and 15.8 ± 4.2 nm for BaSnO₃. These values are in close agreement with results of transmission electron microscopy. The prepared materials have optimal microstructure for successive investigation in dye-sensitized solar cells.     

Template-free hydrothermal derived cobalt oxide nanopowders: Synthesis,characterization, and removal of organic dyes

Pure spinel cobalt oxide nanoparticles were prepared through hydrothermal approach using different counter ions. First, the pure and uniform cobalt carbonate (with particle size of 21.8–29.8 nm) were prepared in high yield (94%) in an autoclave in absence unfriendly organic surfactants or solvents by adjusting different experimental parameters such as: pH, reaction time, temperature, counter ions, and (Co²⁺:CO₃^2?) molar ratios. Thence, the spinel Co₃O₄ (with mean particle size of 30.5–47.35 nm) was produced by thermal decomposition of cobalt carbonate in air at 500 °C for 3 h. The products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), scanning electron microscope (SEM), and thermal analysis (TA). Also, the optical characteristics of the as-prepared Co₃O₄ nanoparticles revealed the presence of two band gaps (1.45–1.47, and 1.83–1.93 eV). Additionally, adsorption of methylene blue dye on Co₃O₄ nanoparticles was investigated and the uptake% was found to be >99% in 24 h.     

Effect of different solvents in the synthesis of LaCoO3 nanopowders prepared by the co-precipitation method

This paper describes the obtention of LaCoO₃ nanopowders by the co-precipitate method with ammonium hydroxide from solvent such as water, ethyl alcohol and ethylene glycol. The crystalline structure and average particle size are dependent of type-solvent. The XRD patterns indicated that the LaCoO₃ nanopowders prepared with water and ethyl alcohol exhibit a pure perovskite-type LaCoO₃ in the rhombohedra structure. The average diameter of the particles prepared with ethyl alcohol and water are 27 ± 4.49 nm and 64.4 ± 12.92 nm respectively. High resolution transmission electron microcopy revealed an oriented attachment mechanism for the growth of aggregated LaCoO₃ nanocrystals. Room temperature magnetization results of the heat treated LaCoO₃ nanopowders exhibited a paramagnetic behavior. The average particle size and formation temperature of LaCoO₃ obtained in this study is comparatively lower than those reported in the literature.     

Synthesis of spherical NiO nanoparticles through a novel biosurfactant mediated emulsion technique

Spherical nickel oxide nanoparticles were synthesized by microemulsion technique using rhamnolipids as the surfactant along with n-heptane and water. Nickel hydroxide (Ni(OH)₂) particles were first formed which were then calcined to obtain nickel oxide (NiO) particles. Scanning Electron Microscopy (SEM) studies revealed that the synthesized nickel hydroxide particles were spherical in shape with stacked lamellar sheets. Nickel hydroxide was converted to nickel oxide by calcinations at 600 °C for 3 h and was confirmed by X-ray Diffraction (XRD) analysis. Transmission Electron Microscopy (TEM) showed that the nickel oxide particles were crystalline and of uniform size. The effect of pH on particle size was investigated and it was found that the particle size decreased from 86 ± 8 nm at pH 11.6 to 47 ± 5 nm at pH 12.5. A novel method using rhamnolipid biosurfactant for microemulsion synthesis has been demonstrated which offers an eco-friendly alternative to conventional microemulsion technique based on organic surfactants.     

Experimental measurements of gold nanoparticle nucleation and growth by citrate reduction of HAuCl4

Gold particle nucleation and growth were analyzed systematically by UV–vis, ELS and TEM measurements. The gold seed particles ranging from 14.3 nm to 20.3 nm were prepared with monodisperse size distribution by citrate reduction reaction of various initial HAuCl₄ concentrations. Gold nanoparticles of different sizes were made by the seed-mediated growth process. In the first stage of seed-mediated growth, most of gold precursors were used for the growth of seed particles, but, further supply of gold precursors promotes the nucleation of small particles and decreases the average particle diameters while the polydispersity of particles increases. This research can be used as basic data to prepare gold nanoparticles with specific properties for different applications.     

A facile method to synthesize novel monodisperse core–shell structure of spherical silica at nanocrystalline copper

A kind of monodisperse core–shell structure of spherical silica at nanocrystalline copper has been successfully synthesized by a two-step synthesis method. A uniform spherical particle of silica was firstly fabricated according to the Stöber method. The obtained silica sample was coated by nanocrystalline copper through oxidation–reduction process. The effects of the volume of water added in the reaction system on particle size of silica were investigated. The particle size of the as-synthesized silica changed from about 170 ± 2 to 160 ± 2 nm with the volume of the added water change from 2.3 to 20 ml. When the volume of the added water was changed to 40 ml, the diameter of the obtained silica particle was about 210 ± 5 nm. The thickness of the coated copper can be controlled by using different sizes of silica particle. The formation mechanism was also discussed.     

Sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor in a heated flow

The sintering behavior of spherical aggregated nanoparticles prepared by spraying colloidal precursor into a heated flow was investigated both experimentally and theoretically. Spherical micrometer-sized particles consisting of compactly aggregated nanoparticles were formed, due to solvent evaporation and the drying process of the colloidal precursor. The degree of sintering of aggregated nanoparticles depended on the furnace temperature profile, residence time and primary particle size of the aggregated nanoparticles. Spherical monodispersed colloidal silica, in sizes ranging from 22 to 100 nm was selected as the primary particles. The sintering rate increased with temperature and residence time, and decreased with increasing primary particle size. The aggregated nanoparticles sintered completely, resulting in particles with smooth surfaces that were synthesized at 1400 °C, residence time 31.7 s that was obtained by using a carrier gas flow rate of 1.5 L/min and 0.1 M colloidal silica nanoparticles 100 nm in size. An appropriate model of sintering in the system was proposed to explain the shrinkage and the neck growth of the aggregated nanoparticles. The sintering analysis suggested that solid-state volume diffusion suitably described the sintering mechanism of spherical aggregated silica nanoparticles in a heated flow.     

Synthesis,characterization and photocatalytic properties of nanostructured ZnO particles obtained by low temperature air-assisted-USP

ZnO nanoparticles were synthesized in a horizontal three zones furnace at 500 °C using different zinc nitrate hexahydrate concentrations (0.01 M, 0.1 M, and 1.0 M) as a reactive precursor solution by air assisted Ultrasonic Spray Pyrolysis (USP) method. The physico-chemical, structural and functional properties of synthesized ZnO nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV–vis spectroscopy and photoluminescence (PL) measurements. Also, the photocatalytic activities of ZnO synthesized from different precursor concentrations were evaluated by removal rate of methyleneblue (MB) under UV irradiation (365 nm) at room temperature. SEM revealed two types of ZnO nanoparticles: a quasi-spherical, desert-rose like shape of the secondary particles, which does not change significantly with the increasing of precursor solution concentration as well as some content of the broken spheres. Increasing the precursor solution concentration leads to the increase in the average size of ZnO secondary particles from 248 ± 73 to 920 ± 190 nm, XRD reveals the similar tendency for the crystallite size which changes from 23 ± 4 to 55 ± 12 nm in the analyzed region. HRTEM implies the secondary particles are with hierarchical structure composed of primary nanosized subunits. The PL spectra imply a typical broad peak of wavelength centered in the visible region exhibiting the corresponding red-shift with the increase of solution concentration: 560, 583 and 586 nm for the 0.01, 0.1 and 1.0 M solution, respectively. The reported results showed the photocatalytic efficiency of ZnO nanoparticles was enhanced by increased precursor concentration.     

Synthesis of TbMnO3 nanoparticles via a polyacrylamide gel route

We report here the synthesis of TbMnO₃ nanoparticles via an acrylamide gel route. XRD, TG analysis, DSC analysis, and FTIR spectroscopy are combinatively used to investigate the thermal decomposition process of precursor xerogels and the formation of TbMnO₃ phase. It is demonstrated that high-phase-purity TbMnO₃ nanoparticles can be prepared by using different chelating agents at a sintering temperature of 800 °C. SEM observation and XRD analysis reveal that the particle size and morphology of the products have a dependence on the chelating agent. The particles prepared using citric acid as the chelating agent appear to be regularly spherical in shape and highly uniform in size with a diameter of ～67 nm, while the sample prepared by using the chelating agent EDTA mainly consists of sphere-, ellipsoid-, and rod-like particles and exhibits a relatively broad particle size distribution with an average particle size centered around 115 nm. The use of a combination of citric acid and EDTA generally results in sphere- and ellipsoid-like particles with an average particle size between those of the samples prepared separately by using the two chelating agents.     

Preparation of high strength macroporous hydroxyapatite scaffold

Hydroxyapatite (HAp) powder was prepared from CaNO₃·4H₂O and (NH₄)₂HPO₄ by wet-chemical method and has phase stable up to 1250 °C. High strength macroporous HAp–naphthalene (HN) and HAp–naphthalene–benzene (HNB) scaffolds were fabricated by adapting sintering method. The resulting HAp scaffolds have porosity about 60 vol.% with compressive strength of ~ 11 MPa and average pore diameter in the range of ~ 125 μm. The incorporation of benzene in HN scaffold reduces the strength whereas enhanced both the porosity and pore size distribution. XRD, FTIR, SEM and mercury porosimeter techniques were used to study the phase purity, morphology, pore size and pore size distribution of scaffold. The study compared the effect of concentration of naphthalene on strength, porosity and pore size distribution on both HN and HNB scaffold. In-vitro bioactivity studies on HN and HNB scaffolds show the nucleation of spherical carbonated apatite particles on the surface in SBF solution.     

Optical investigations on indium oxide nano-particles prepared through precipitation method

Visible light emitting indium oxide nanoparticles were synthesized by precipitation method. Sodium hydroxide dissolved in ethanol was used as a precipitating agent to obtain indium hydroxide precipitates. Precipitates, thus formed were calcined at 600 °C for 1 h to obtain indium oxide nanoparticles. The structure of the particles as determined from the X-Ray diffraction pattern was found to be body centered cubic. The phase transformation of the prepared nanoparticles was analyzed using thermogravimetry. Surface morphology of the prepared nanoparticles was analyzed using high resolution-scanning electron microscopy and transmission electron microscopy. The results of the analysis show cube-like aggregates of size around 50 nm. It was found that the nanoparticles have a strong emission at 427 nm and a weak emission at 530 nm. These emissions were due to the presence of singly ionized oxygen vacancies and the nature of the defect was confirmed through Electron paramagnetic resonance analysis.     

Study on crystallinity and morphology controlling of titania using acrylamide gel method and their photocatalytic properties

In this study, polyacrylamide gel method was used for preparation of pure and mixed phase TiO₂ nanoparticles. The influence of synthesis conditions on the physicochemical properties of products was investigated. It was found that the type of acid, which was used for acidifying the precursor solution together with calcination temperature can affect the phase structure, crystalline size, morphology and thereby photocatalytic activity of obtained TiO₂ nanoparticles. Different trends were observed during the phase transformation, particle growth, shift in energy of band gap with the change in tensile strain to compressive strain of the prepared TiO₂ nanomaterial. X-ray diffraction (XRD) showed that prepared nanocrystals, which were calcined at 450 °C have pure anatase and anatase–rutile mixed structures. The prepared samples having crystallite size between 5 nm and 60 nm were observed at different calcination temperatures. In addition, the photocatalytic activities of the prepared samples were evaluated by monitoring the degradation of Cresol Red (CR). The results show that the photocatalyst (TEC_I), exhibits the highest photocatalytic efficiency where 94.7% of CR can be decomposed after UV exposure for 75 min.     

Ribbon-like and rod-like hydroxyapatite crystals deposited on titanium surface with electrochemical method

Homogeneous coatings were attained by electrochemical method in electrolytes containing Ca²⁺ and PO₄³⁻ ions with Ca/P ratio being 1.67. SEM observation showed that the hydroxyapatite (HAp,Ca₁₀(PO₄)₆(OH)₂) crystals prepared with higher concentration electrolyte (4 × 10^− 2 M Ca²⁺) are ribbon-like with thickness of nanometer size, a morphology seldom reported previously. In an electrolyte of lower concentration (6 × 10^− 4 M Ca²⁺), the HAp crystals formed are rod-like with a hexagonal cross section and diameter of about 70–80 nm. XRD patterns and IR spectra confirmed that the coatings consist of HAp crystals. TEM micrographs and SAD indicated that the longitude direction for both ribbon-like and rod-like crystal is [002], and the flat surface of the ribbon is (110). HRTEM showed that the ribbon-like crystal is a mixture of HAp and octacalcium phosphate (OCP, Ca₈H₂(PO₄)₆.5H₂O).     

Silver nanoparticle-loaded chitosan–starch based films: Fabrication and evaluation of tensile,barrier and antimicrobial properties

The fabrication of silver nanoparticles was accomplished by γ-ray irradiation reduction of silver nitrate in a chitosan solution. The obtained nanoparticles were stable in the solution for more than six months, and showed the characteristic surface plasmon band at 411 nm as well as a positively charged surface with 40.4 ± 2.0 mV. The silver nanoparticles presented a spherical shape with an average size of 20–25 nm, as observed by TEM. Minimum inhibitory concentration (MIC) against E. coli, S. aureus and B. cereus of the silver nanoparticles dispersed in the γ-ray irradiated chitosan solution was 5.64 µg/mL. The silver nanoparticle-loaded chitosan–starch based films were prepared by a solution casting method. The incorporation of silver nanoparticles led to a slight improvement of the tensile and oxygen gas barrier properties of the polysaccharide-based films, with diminished water vapor/moisture barrier properties. In addition, silver nanoparticle-loaded films exhibited enhanced antimicrobial activity against E. coli, S. aureus and B. cereus. The results suggest that silver nanoparticle-loaded chitosan–starch based films can be feasibly used as antimicrobial materials for food packaging and/or biomedical applications.     

Magnetic and dielectric properties on sol–gel combustion synthesis of Pb(Zr0.52,Ti0.43X0.05)O3 (X = Fe,Ni, and Co) nanoparticles

Pure and X-doped (X = Fe, Ni, and Co) PZT nanoparticles (PZT-NPs) were synthesized by a sol–gel combustion method. The structural characterization of the obtained pure and doped PZT-NPs was carried out by X-ray diffraction (XRD). The crystallite size of the prepared samples was then evaluated by the size strain plot (SSP) method using the XRD results. The average particle sizes of 30–40 nm were measured for pure and doped PZT-NPs by a particle size analyzer. For dielectric measurements, the synthesized powders were pressed into pellets and then sintered at 1250 °C for 2 h. The magnetic properties of the synthesized doped PZT-NPs were studied by a vibration sample magnetometer (VSM) and ferromagnetic behavior was observed.     

Synthesis and characterization of CuInSe2 nanoparticles via a solution method

Pure CuInSe₂ nanoparticles have been successfully synthesized via a solution method in the solvent of oleylamine. Anhydrous InCl₃, CuCl, and Se powder were used as the starting materials. The CuInSe₂ samples were characterized by XRD, TEM, and XPS techniques. It was found that tetragonal chalcopyrite structured CuInSe₂ nanoparticles were obtained with temperature above 230 °C. Sample prepared at 200 °C possesses triangular morphology and a minute amount of In₂Se₃ coexists as intermediate. CuInSe₂ nanoparticles with size of 20.2 ± 0.4 nm were prepared at 230 °C and the narrow size distribution was ascribed to the employment of hot injection, which was better for homogeneous nucleation. Stable “ink” can be formed when the as-synthesized CuInSe₂ nanoparticles were dispersed in organic solvents such as hexane and tolune, and such “ink” might have a practical application in CuInSe₂-based solar cells.     

Adsorption of gum Arabic on bioceramic nanoparticles

Surface modification agents can be used to tailor the surface chemistry and biological activity of bioceramic nanoparticles in very intriguing ways. However, the specific modes of interactions between macromolecules and nanoparticles can be difficult to characterize. The aim of this study was to investigate the adsorption of gum Arabic on hydroxyapatite (HAp) and magnetic nanoparticles (MNP) using the bicinchoninic acid (BCA) test. Gum Arabic (GA) is a natural gum that has been widely used as an emulsifying agent and shows promise for dispersing nanoparticles in aqueous solutions. The adsorption of GA onto HAp nanoparticles followed a Langmuir isotherm with an adsorption plateau occurring at 0.2 g GA/g HAp. The adsorption of GA onto MNP attained a maximum value of 0.6 g GA/g MNP, after which it decreased to approximately 0.2 g GA/g MNP. The maximum adsorption density of GA on both MNP and HAp is equivalent when normalized to the specific surface area (4 × 10^− 3 g GA/m²). Adsorbed GA molecules were displaced from the surface of HAp and MNP in the presence of phosphate ions.