Israel López

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.

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.

Modification of the luminescent properties of ZnS nanoparticles by the adsorbed species

Abstract We report the modification of the luminescent properties of ZnS nanoparticles by the adsorbed chemical species. ZnS nanoparticles were prepared via microwave-assisted synthesis. The effects of the concentrations of citrate and SO42− ions on the optical properties were analyzed by means of UV-Vis and photoluminescence spectrophotometries, and Fourier-transform IR spectroscopy. ZnS nanoparticles were also analyzed by means of X-ray diffraction and transmission electron microscopy. The results confirm that the luminescent properties of the synthesized particles are affected by the adsorbed chemical species (citrate and SO42− ions). ZnS nanoparticles synthesized with 30 and 45 mM Na2SO4, and 2 mM trisodium citrate exhibit higher intensity of luminescence than those synthesized with 15 mM Na2SO4. The average diameter of the ZnS nanoparticles synthesized under these last experimental conditions is about 20 nm.

Electrophoretic Deposition of Cadmium Sulfide Nanoparticles: Electric Field and Particle Size Effects

The present work shows the electric field and particle size effects on the formation of nanostructured arrays by electrophoretic deposition of cadmium sulfide (CdS) nanoparticles. The CdS nanoparticles with mean diameter below 6 nm were prepared by a microwave assisted synthesis. These nanoparticles were aged for one and two weeks at room temperature in order to produce nanoparticle agglomeration. The CdS nanoparticles were deposited on aluminum plates, with 1 cm of distance between them, using a constant applied voltage of 600 and 900 mV for 1 min. The nanostructures formed using CdS nanoparticles freshly prepared under 900 mV show spherical morphology. Under a voltage of 600 mV, nanostructures with elongated morphology were obtained.

Direct Electrochemical Synthesis of Metal Complexes

Abstract The electrolytic oxidation of a metal anode in a solvent containing the ligand of interest is a single-step process for the synthesis of metal complexes. This method allows the formation of both coordination complexes and organometallic compounds. The direct electrochemical synthesis of metal complexes is a simple technique, often carried out at room temperature, which allows us to choose from a variety of ligands. The electrolytic oxidation of the metal avoids the use of oxidizing agents; therefore there are no species that could compete with the ligand to coordinate with the metal ion. The electrosynthesis can be kinetically controlled by adjusting the intensity of the current through the cell, if the reduced metal ions are generated slowly.

Nanomaterials for Printing Technology

Abstract 2D printing is a commonly used technology based on the addition of dots onto a flat surface with X and Y axis. 3D printing, on the other hand, is related to additive manufacturing by adding layer by layer of the raw material fed into it to create a final product; in other words, it adds another dimension of depth, that is to say, a Z axis. 3D printing applications are revolutionary when compared to 2D because it is possible to create a complex object in numerous possible materials. Recently, the use of nanomaterials in 3D printing technology has gained attention, especially the synthesis of nanostructured dispersions also called nanoinks, which are used as building material in the additive manufacture process. The incorporation of nanomaterials in 3D printing techniques has allowed the introduction of materials for new generation devices with specific electrical, optical, and mechanical properties. 3D printing has been used to create nanoengineering prototypes; they have the potential to optimize the resources in fields like reconstructive medicine, electronic circuits, and scaffolds fabrication, among others. 3D printing technology has already been proved as a viable alternative in several medical applications including the manufacture of custom prosthetic devices, dental implants, and even the first steps in organs and tissues printing. In circuit fabrication, printable conducting inks, such as metals and conductive polymers, have been widely studied allowing the fabrication of flexible electric circuits and chemical sensors. Furthermore, the use of 3D printing technology is often supported in scaffolds, which provides, mainly, mechanical and electrical properties to the final composite. The development of new inks based on nanomaterials often encounters different obstacles, such as controlling the ink viscosity and surface tension, which are important parameters in the printing process.

Condensation of Carbon Vapour in the Microwave Oven

Abstract : This work is devoted to microwave heating of graphite for studying the processing of carbon nanotubes (CNTs) by graphite vaporization. We have applied heating by microwaves (MW) (power 800W, frequency 2.45 GHz) in air at 20-90 min. The oven temperature was approximately 1200 deg. C. The condensed material was collected on a fused silica target. After deposition, the morphology of carbon nanotubes was studied by Scanning Electron Microscopy (SEM) Atomic Force Microscopy (AFM), and Transmission Electron Microscopy (TEM). The samples were found to contain nanotubes, nanoparticles and fibers (at 1.30-2.80 micrometers to 6-11 micrometers) which appeared to be highly graphitized. It was observed that multi-walled nanotubes (MWNTs) were produced by this method.