Idalia Gómez

Solubilization, dispersion and stabilization of magnetic nanoparticles in water and non-aqueous solvents: recent trends

Recent achievements in the solubilization and stabilization of magnetic nanoparticles (MNPs) are reviewed. The majority of reported MNPs correspond to iron-based {nZVI, superparamagnetic iron oxides (SPIONs), core–shell Fe/Au or FexOy/Au nanoparticles and ferrites} nanoparticles, with a few numbers corresponding to MnO and cobalt nanoparticles. Magnetic nanoparticles can be solubilized in water or non-aqueous solvents for short or long time periods. The main approaches for MNP solubilization are discussed, namely, suitable choice of precursors, pH, surfactants/coating agents, and solvents, as well as functionalizing agents. MNPs are generally solubilized by functionalization with water-soluble compounds/moieties (in particular, sulfonic acid disodium salts, soluble polymers, porphyrins and calixarenes), under conditions of the thermal decomposition of low stability metal complexes, coprecipitation, microwave heating, and by ultrasonication. The polyol strategy is frequently applied to increase MNP solubility. The stabilization of MNPs in solutions could be achieved with the help of inorganic, monomeric and polymeric compounds.

Facile and rapid detection of respiratory syncytial virus using metallic nanoparticles

BackgroundRespiratory syncytial virus (RSV) causes severe respiratory infection in infants, children and elderly. Currently, there is no effective vaccine or RSV specific drug for the treatment. However, an antiviral drug ribavirin and palivizumab is prescribed along with symptomatic treatment. RSV detection is important to ensure appropriate treatment of children. Most commonly used detection methods for RSV are DFA, ELISA and Real-time PCR which are expensive and time consuming. Newer approach of plasmonic detection techniques like localized surface plasmon resonance (LSPR) spectroscopy using metallic nanomaterials has gained interest recently. The LSPR spectroscopy is simple and easy than the current biophysical detection techniques like surface-enhanced Raman scattering (SERS) and mass-spectroscopy.ResultsIn this study, we utilized LSPR shifting as an RSV detection method by using an anti-RSV polyclonal antibody conjugated to metallic nanoparticles (Cu, Ag and Au). Nanoparticles were synthesized using alginate as a reducing and stabilizing agent. RSV dose and time dependent LSPR shifting was measured for all three metallic nanoparticles (non-functionalized and functionalized). Specificity of the functionalized nanoparticles for RSV was evaluated in the presence Pseudomonas aeruginosa and adenovirus. We found that functionalized copper nanoparticles were efficient in RSV detection. Functionalized copper and silver nanoparticles were specific for RSV, when tested in the presence of adenovirus and P. aeruginosa, respectively. Limit of detection and limit of quantification values reveal that functionalized copper nanoparticles are superior in comparison with silver and gold nanoparticles.ConclusionsThe study demonstrates successful application of LSPR for RSV detection, and it provides an easy and inexpensive alternative method for the potential development of LSPR-based detection devices.

Biosynthesis of Cadmium Sulfide Nanoparticles by the Fungi Fusarium sp.

ABSTRACT CdS nanoparticles have attracted attention due to its optical and electrical properties. Conventional methods provide some problems, such as particle size, high-pressure requirements, and the use of toxic materials, for its synthesis. It is well known that many microorganisms can provide inorganic materials either intra- as extracellularly. In this work, the authors present the results of the CdS nanoparticles synthesis using Fusarium sp. biomass as a sustainable synthesis procedure, after its exposition with a CdSO4 solution. Nanoparticles were characterized by ultraviolet-visible, x-ray diffraction, and atomic force microscopy.

Microwaves Applied to Carbothermic Reduction of Iron Ore Pellets

Results of reduction tests conducted on iron ore pellets with carbon are presented in this work. Work done is centered on reduction kinetics using carbon as the reducing agent with a conventional heat supply (heat transfer process) compared with reduction kinetics where heat is supplied by microwaves to the whole volume. Ore used in this work is called “Alzada” which has well known reducibility characteristics, and is often used as standard for comparison.

In Situ Synthesis and Deposition of Gold Nanoparticles with Different Morphologies on Glass and ITO Substrate by Ultrasonic Spray Pyrolysis

Gold nanoparticles were synthesized and deposited in situ by ultrasonic spray pyrolysis on glass and indium tin oxide (ITO) substrates. This technique led to the formation of gold nanoparticles with different morphologies without the use of any capping agent. The gold nanoparticles deposited on glass substrate were obtained as nanospheres with an average particle size of 30 nm with some agglomerates; however, the nanoparticles deposited on ITO substrate were obtained with different morphologies, such as triangular nanoprisms, nanorods, nanocubes, and nanorhombus, with particle sizes between 40 and 100 nm. The ITO substrate influenced the morphology of the gold nanoparticles obtained due to changes in the deposition temperature, which also change the crystalline structure of the ITO film on the substrate.

MICROWAVES AS AN ENERGY SOURCE FOR PRODUCING MAGNESIA-ALUMINA SPINEL

This work describes the production of magnesia-alumina spinel using microwaves as an energy source. The microwave energy was supplied by means of an 800 W magnetron operating at 2.45 GHz. The microstructure and the mineral composition were studied by means of scanning electronic microscopy (SEM) and X-Ray diffraction respectively. The resultant product showed sintered zone and incipient smelting of the reagents meaning that microwave processing could be a practical method for spinel production.

One-Step Green Synthesis of Metallic Nanoparticles Using Sodium Alginate

Metallic nanoparticles have been focus of research because of their characteristic properties, specifically the LSPR which can have wide applications in biomedical sciences and engineering. Currently, traditional physical and chemical methods can synthesize these nanoparticles but their disadvantages such as costs, time, effectiveness, and toxicity of precursors provide a wide range of problems for the synthesis of these nanoparticles. Recently, some natural polymers and organic compounds have been used for the synthesis of nanoparticles by green methods. In this study, we synthesize copper, silver, and gold nanoparticles using sodium alginate as reducing and stabilizing agent under microwave irradiation. The LSPR for each system was observed by UV-vis spectroscopy. Particle size distribution and zeta potential demonstrate the size and stability for these nanoparticles. FESEM and TEM microscopies have shown the size and morphology of these systems correlated with UV-vis, particle size distribution, and zeta potential analyses. The study demonstrates a rapid, facile, cheaper, and one-step green method of synthesis for these metallic nanoparticles being an alternative to the conventional methods used for synthesis of metallic nanoparticles.

Cadmium Sulfide and Zinc Sulfide Nanostructures Formed by Electrophoretic Deposition

Cadmium sulfide (CdS) and zinc sulfide (ZnS) nanostructures were formed by means of electrophoretic deposition of nanoparticles with mean diameter of 6 nm and 20 nm, respectively. Nanoparticles were prepared by a microwave assisted synthesis in aqueous dispersion and electrophoretically deposited on aluminum plates. CdS thin films and ZnS one-dimensional nanostructures were grown on the negative electrodes after 24 hours of electrophoretic deposition at direct current voltage. CdS and ZnS nanostructures were characterized by means of scanning electron (SEM) and atomic force (AFM) microscopies analysis. CdS thin films homogeneity can be tunable varying the strength of the applied electric field. Deposition at low electric field produces thin films with particles aggregates, whereas deposition at relative high electric field produces smoothed thin films. The one-dimensional nanostructure size can be also controlled by the electric field strength. Two different mechanisms are considered in order to describe the formation of the nanostructures: lyosphere distortion and thinning and subsequent dipole-dipole interactions phenomena are proposed as a possible mechanism of the one-dimensional nanostructures, and a mechanism considering pre-deposition interactions of the CdS nanoparticles is proposed for the CdS thin films formation.

Highly Luminescent ZnS Nanoparticles Obtained by Microwave Heating

We report the results of the synthesis and characterization of highly luminescent ZnS nanoparticles obtained by microwave heating working at 905 W during 60 sec. The products were characterized by UV-vis spectroscopy, photoluminescent spectroscopy, X-ray diffraction and atomic force microscopy. Different morphologies were observed by AFM, nanoparticles (average diameter = 100 nm) and nanoislands (micrometer size). As the content of S 2− and Zn 2+ decreases, the band edge emission becomes higher and the photoluminescent intensity increases, finding a quantum yield of 70%, and both of these properties exhibit a blue shift due to the reduction in particle size. The X-ray diffraction analysis indicates the presence of ZnS in cubic sphalerite form. Microwave heating includes the ability to quickly reach reaction temperatures and a straightforward process control, thus making quantum dot materials with quantum yield (QYs) of 70%, accessible to an increased number of research labs.

Influence of Precursor and Power Irradiation on the Microwave-Assisted Synthesis of ZnS Nanoparticles

Results on the synthesis of ZnS nanoparticles from ZnSO 4 and Zn(CH 3 COO) 2 as precursors under microwave (MW) heating conditions are reported. An MW oven (1650 W) operating at 60 and 100% of the nominal power in periods for 60 s was employed. The obtained dispersions were analyzed by UV-Vis spectroscopy, X-ray diffraction, photoluminescence, and transmission electron microscopy. The results show that the dispersion concentration depends mainly on the applied power, whereas the luminescent properties are related with the employed precursors, because the sulfate ions promote the electronic transition in the ZnS nanoparticles, synthesized with a mean radius of 7.1 nm and possessing a hexagonal morphology.