Controlled Co-precipitation Method Research Articles

Study of Congo red photodegradation kinetic catalyzed by Zn1-XCuXS and Zn1-XNiXS nanoparticles

A controlled co-precipitation method was used to prepare nanoparticles of zinc sulfide doped with Ni and/or Cu in the presence of mercaptoethanol as capping agent. The nanoparticles characterize via UV-visible spectra, atomic absorption spectrophotometer (AAS), X-ray powder diffraction (XRD) patterns and transmission electron microscope (TEM) image. The doping of Ni2+ and/or Cu2+ ions did not altered the phase of zinc sulfide nanoparticles. Congo red photodegradation kinetic catalyzed by synthesized nanoparticles was studied under UV-visible irradiation. The effect of dopant mole fraction, the dosage of photocatalysts and the samples pH were investigated on the decolorization rate of dye. More degradation of dye was achieved in neutral samples versus acidic or alkaline pH. The Congo red was degraded more than 95 and 98% in the presence of 800 mg/L of Zn0.94Ni0.06S and Zn0.90Cu0.10S nanoparticles, respectively, within 120 min. The effect of hydrogen peroxide and several anions were investigated on the catalytic activity of proposed photocatalysts. Also, the reproducibility of nanoparticles behavior as photocatalyst showed at least a four-cycle of photodegradation process. Key words: Nanoparticles, zinc sulfide, Congo red, photocatalyst, photodegradation.

Tuning of magnetic properties in Co–Zn ferrite nanocrystals synthesized by a size controlled co-precipitation method

CoxZn1−xFe2O4 (0.5 ≤ x ≤ 1.0) nanocrystals have been synthesized by conventional and a modified size-controlled coprecipitation method and characterized by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and Mössbauer spectroscopy. The control of the oversaturation conditions in the reacting solution, favored by the control of the flow rate at which the reactants were contacted, promoted heterogeneous nucleation and hence crystal growth, as evidenced by XRD measurements. The size-controlled synthesis route also allowed the tuning of the maximum magnetization and the coercivity, which increased by a factor of five. The demagnetization temperature was found to be strongly dependent on the Co-content and crystal size and varied between 106 °C and 540 °C. Mössbauer spectroscopy confirmed the strong influence of the synthesis conditions on the superparamagnetic fraction in the samples.

Decolorization kinetic studies of Congo red catalyzed by Co-doped CdS nanoparticles

The Cd0.97Co0.03S nanoparticles were prepared by using a controlled co-precipitation method. The nanoparticles were characterized by using UV-Vis spectra, XRD patterns and TEM image. The blue shift in the band gap of CdS semiconductor was observed with decreasing of the particle size. The XRD patterns prove the zinc-blend-type of Cd0.97Co0.03S nanoparticles. The size of nanoparticles less than 50 nm was confirmed through TEM image. The decolorization kinetics of Congo red catalyzed by prepared nanoparticles was studied under UV and sunlight irradiations. The decolorization study of dye with the initial concentration 20 mg/L shows the pseudo-first order kinetics with the apparent rate constant 1.35×10−2 min−1 at pH 7. The Cd0.97Co0.03S photocatalyst also indicates an excellent reactivity for bleaching of dye under sunlight irradiation with the apparent rate constant of 1.01×10−2 min−1. Degradation of 92–82% of Congo red was obtained in five cycles of reuse of proposed photocatalyst and dissolution of photocatalyst was found to be less than 0.2%.

A biocompatible approach to surface modification: Biodegradable polymer functionalized super-paramagnetic iron oxide nanoparticles

In the study, Fe3O4 nanoparticles with a size range of 10–20 nm were firstly prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. Then, the super-paramagnetic iron oxide nanoparticles were covalently modified by biodegradable polymers such as polyethylene glycol (PEG) and poly(ethylene glycol)-co-poly(d,l-lactide) (PELA). The size and its distribution of the nanoparticles were determined by dynamic light scattering measurements (DLS). The magnetic nanoparticles was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), Fourier transform infrared spectroscopy (FT-IR) and UV–visible spectrophotometry (UV). Magnetic properties were measured using a vibrating sample magnetometer. And the 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of the magnetic nanoparticles. The results showed that the Fe3O4 nanoparticles functionalized by PEG and PELA possessed a mean size of 43.2 and 79.3 nm, respectively, and exhibited an excellent biocompatibility.

Growth, characterization and transport properties of Pb x Zn1−x S mixed crystals

The polycrystalline Pb x Zn1−x S semiconductor powder with (0 ≤ x ≤ 0·5) has been prepared by controlled co-precipitation method from an alkaline medium using thiourea as a sulphide ion source. Pellets are made with these powders applying 10 ton/sq.cm. pressure and sintered at 800°C for 2 h in nitrogen atmosphere. X-ray studies of these samples have indicated that the compounds are polycrystalline in nature with mixed hexagonal and cubic structure of ZnS and cubic structure of PbS. Lattice parameters (a and c) of all the compounds are determined from the X-ray data and are found to decrease nonlinearly with increase in Pb concentration (x). It is also observed that the grain size of the crystallites increases in samples with x = 0−0·5. Scanning electron micrographs have shown that both cubic and hexagonal crystallites are present in the mixed crystals. The electrical conductivity in Pb x Zn1−x S is found to decrease with increase in composition (x = 0−0·5), whereas it increases at all temperatures in all samples. Mobility of charge carrier concentration is found to increase with increasing temperature. The increase in carrier mobility in Pb x Zn1−x S samples may be due to reduced grain boundary potential. In Pb x Zn1−x S samples with x = 0−0.3, the sum of the activation energy due to charge carriers and grain boundary potential is equal to the activation energy due to conductivity.

Methane gas-sensing and catalytic oxidation activity of SnO2–In2O3 nanocomposites incorporating TiO2

The InO1.5–SnO2 nanocomposites incorporating TiO2 were synthesized by a controlled co-precipitation method as sensing materials of a novel semiconductor CH4 sensor. Through manipulating the total salt concentration, cation ratio, precipitation pH, aging time and calcination temperature, the nanocrystalline composites were successfully derived with chemical homogeneity and superior thermal stability compared to tin oxide. The gas-sensing and catalytic activity for methane oxidation were examined in a micro fixed bed reaction system. The experimental results showed that the nanocomposites exhibited high gas-sensing and catalytic activity, and these performances depended on composition of composites, calcination temperature of precursors and sensor operating temperature. It was found that the sensing behavior was straightforwardly related to the catalytic activity. The sensing and catalytic activity was greatly enhanced by the introduction of metal elements or oxide surface coatings. To guide for the search of better sensor materials or suitable additives, it is necessary to understand the sensing mechanism of the semiconductor oxide gas sensors by temperature-programmed desorption (TPD) study and X-ray photoelectron spectroscopic (XPS) analysis.

Preparation and characterization of interferon‐loaded magnetic biodegradable microspheres

In this work, magnetite (Fe(3)O(4)) nanoparticles with an average size 10 nm modified by sodium oleate were prepared by the modified controlled chemical coprecipitation method, which can be well dispersed in water and linked well with protein molecules because of the presence of -COOH on their surface. Then magnetic poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) microspheres containing interferon alpha-2b (IFN-a-2b) were prepared by the modified water-in-oil-in-water solvent evaporation procedure. X-ray powder diffraction analysis, particle size analysis, transmission electron microscopy, scanning electron microscopy, and vibrating-sample magnetometer (VSM) analysis were carried out to examine phase composition, surface and interior morphology, size and size distribution, and magnetic properties of the magnetic microspheres. Also the effects of some important parameters on the magnetic biodegradable microspheres were investigated, such as magnetite dosage in the preparation system, stirring rate of the suspension medium, and concentration of the external aqueous phase. And the antiviral activity of IFN-a-2b encapsulated in the magnetic polymeric microspheres was evaluated by the vesicular stomatitis virus (VSV) cytopathicity inhibition assay. The results showed that the properties of IFN-loaded magnetic PLGA and PLA microspheres were better than the conventional protein-loaded polymeric microspheres, such as perfect magnetic properties, higher protein encapsulation efficiency, and less effect on the antiviral activity of protein. These indicated that the magnetic PLA and PLGA microspheres containing IFN-a-2b exhibited strong potential as targeted-drug delivery vehicles, which could be rapidly localized to the immunization-related tissues easily by an external magnetic field.

Sensing characterization of Sn/In/Ti nanocomplex oxides for CO, CH4 and NO2

The nanocomplex oxides of Sn-In and Sn-In-Ti were prepared by controlled co-precipitation method as sensing materials of semiconductor gas sensors for detection of CO, CH4 and NO2. Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging time, the nanocrystalline powders were successfully derived with chemical homogeneity and superior thermal stability, compared with the single component oxides. The particle size and morphology, surface area, and thermal and phase stabilities were characterized using TEM, TG-DTA, BET and XRD. The sensing tests showed that the Sn-In composites exhibit high sensitivity and selectivity for CO and NO2. The introduction of TiO2 enhanced CH4 sensitivity and selectivity, particularly, additives of Pd and Al2O3 as a dopant and surface modification greatly enhanced the sensing properties. The sensitivity depended on the composition of composites, calcination temperature and operating temperature. The optimal values were (25%In2O3-75%SnO2)-20%TiO2 for temary composite, 600 and 300°C, respectively. Temperature-programmed desorption (TPD) studies were employed to explain the gas adsorption behavior displayed by the surface of nanocomposites and X-ray photoelectron spectroscopic (XPS) analysis was used to confirm the electronic interactions existing between oxide components. The sensing mechanism of the nanocomposites was attributed to chemical and electronic synergistic effects.

Synthesis and characterization of biocompatible Fe3O4 nanoparticles

In this study, magnetite (Fe3O4) nanoparticles with a size range of 8-20 nm were prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. In the process, two kinds of surfactant (sodium oleate and polyethylene glycol) were studied; then, sodium oleate was chosen as the apt surfactant to attain ultrafine, nearly spherical and well-dispersed (water-base) Fe3O4 nanoparticles, which had well magnetic properties. The size and size distribution of nanoparticles were determined by particle size analyzer. And the magnetite nanoparticles was characterized by X-ray powder diffraction (XRD) analysis, transmission electron microscopy (TEM), electron diffraction (ED) photography, Fourier transform infrared spectrometer (FT-IR), and vibrating-sample magnetometer (VSM). Also the effect of many parameters on the Fe3O4 nanoparticles was studied, such as reaction temperature, pH of the solution, stirring rate and concentration of sodium oleate. And the 5-dimethylthiazol-2-yl-2,5- diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of magnetite nanoparticles. The results showed that the Fe3O4 nanoparticles coated by sodium oleate had a better biocompatibility, better magnetic properties, easier washing, lower cost, and better dispersion than the magnetite nanoparticles coated by PEG.

Bioerodible Polymeric Nanoparticles for Targeted Delivery of Proteic Drugs

Significant efforts are being devoted to develop nanotechnology for drug delivery, mainly because of the distinct advantages offered by nanometer-size polymeric systems. Moreover, targeted drug delivery can be obtained by polymer conjugation to biospecific ligands. The present investigation was aimed mainly at determining the targeting ability of hybrid nanoparticles based on synthetic polymer/protein hybrid matrices. These nanoparticles were designed for liver targeted release of proteic drugs with antiviral activity, such as alpha-interferon. Human serum albumin and the monoesters of alternating copolymers of maleic anhydride/alkyl vinyl ethers of oligo(ethylene glycol) were selected as proteic and synthetic components, respectively. Digalactosyl diacyl glycerol, a natural glycolipid selectively recognized by the asialofetuin receptor present on liver hepatocytes was used as active targeting agent. Nanoparticles of 100-300 nm average size were obtained by controlled coprecipitation method. Investigation of nanoparticle surface properties by spectroscopic analysis and by biological tests indicated that the synthesized nanoparticles do expose on their surface targeting moieties that selectively interact with liver hepatocytes receptors.

Synthesis of amino-modified magnetite nanoparticles coated with Hepama-1 and radiolabeled with 188Re for bio-magnetically targeted radiotherapy

Ultrafine well -dispersed magnetite nanoparticles were directly prepared in aqueous solution using the controlled coprecipitation meth od. This paper discusse s the preparation of novel surface silica modified colloids with a core of single -domain magnetite particles . Amino -silane was covalently coupled to the colloids and activated by glutaraldehyde. The underlying idea is to tailor the s ilica shell thickness and surface properties such that the colloids became stable spheres with isotropic interactions, whereas an external magnetic field produces weak dipolar attractions and consequently reversible anisotropic structures. Hepama -1, a huma nized monoclonal antibody directed against liver cancer, was coated on functional magnetic nanoparticles by the cross -linker glutaraldehyde to prepare immuno -magnetic nanoparticles (IMN). A direct labeling method was adopted to radiolabel IMN with 188 Re . T he radiolabeling efficiency was about 90% with good in vitro stability. Such nanoparticles might be useful for bio -magnetic radiotherapy .

Preparation, characterization and gas-sensing properties of SnO2–In2O3 nanocomposite oxides

This paper aims at preparing gas-sensing nanocomposites of SnO2–In2O3 using a chemically controlled co-precipitation method and testing their sensing properties for detection of toxic gases. Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging conditions, the nanocrystalline composite powder was successfully derived with chemical homogeneity and superior thermal stability compared to the single-component oxides. The experimental results showed that these nanocomposites exhibited high sensitivity and selectivity for the detection of CO and NOx, and the sensitivity depended on the composition of the composites, calcination temperature and operating temperature. Their sensing performance was further enhanced through the introduction of a small amount of metals or other oxides as dopants and surface coatings. The gas-sensing mechanism of the nanocomposites was also discussed by X-ray photoelectron spectroscopic (XPS) analysis and temperature-programmed desorption (TPD) studies at gas-sensing operating temperatures.

Synthesis and characterization of ultrafine well-dispersed magnetic nanoparticles

Ultrafine well-dispersed magnetic nanoparticles were directly prepared in aqueous solution using controlled coprecipitation method. The structure, size, size distributions and magnetic properties of the magnetic nanoparticles, characterized by TEM, XRD and VSM, indicated the formation of single domain nanoparticles with average size smaller than 5nm. The magnetic nanoparticles show superparamagnetism and a lower saturation magnetization is found as a consequence of smaller particle size. The relevant conditions for obtaining these magnetic colloids are discussed and the so-prepared magnetic nanoparticles are stable in a wide pH range.

SYNTHESIS AND CHARACTERIZATION OF (CdSe)1-X(ZnS)x MIXED POLYCRYSTALLINE SEMICONDUCTORS BY CO-PRECIPITATION METHOD

The polycrystalline (CdSe)1-x (ZnS)x semiconductor powder with (0 ≤ x ≤ 1) has been prepared by controlled co-precipitation method from an alkaline medium using thiourea as a sulphide ion source. Pellets are made out of these powders under 10 tonnes/sq.cm pressure and are sintered at 800°C for 2 hours in nitrogen atmosphere. X-ray studies have indicated that the compounds are polycrystalline in nature with mixed hexagonal structure of CdSe with x = 0-0.3 and cubic structure of ZnS with x = 1. The chemical homogeneity of the samples was observed from the EDAX and also noted that the atomic contents present were as per the constituents taken in the solution. Lattice parameters (a and c) of all the compounds are determined from the X-ray data and are found to decrease with the increase in ZnS content. It is also observed that the grain size decreases with the increase in x from 0-0.6 and later it remained almost the same till x reaches 0.9. Optical studies indicated that the energy gap was as high as 5.2 eV and remained almost same throughout the composition range x = 0-1. Scanning electron micrographs have shown platelet like structure in CdSe and mixed compounds where as a mixed Cubic and Hexagonal structure in ZnS. The results are explained based on different phases present in the compounds.