Álvaro de Jesús Ruíz-Baltazar

Effect of the surfactant on the growth and oxidation of iron nanoparticles

Fe nanoparticles and branched nanostructures of iron oxide were synthesized by chemical reduction in aqueous phase. The mechanism of formation of iron oxides as a function of the amount of surfactant employed during the synthesis process was studied. Specifically Fe, Fe2O3, and Fe3O4 nanoparticles were obtained. The oxidation of Fe to Fe3O4 and finally to Fe2O3 was carried out by oxidative etching process, decreasing the amount of stabilizer agent. The structures obtained were characterized by high resolution (HRTEM) and scanning/transmission (STEM) electron microcopies, energy dispersive spectroscopy (EDS), and optical spectroscopy (UV-Vis and IR).

Comparative Study of Ag Nanostructures

Nanoparticles of Ag with different sizes and structures were obtained and studied. Two methods for reductions of Ag ions were employed, chemical reduction by sodium borohydride and ethylene glycol. Cuboctahedral and icosahedral structures were obtained. Molecular simulations were carried out in order to evaluate the reactivity of both structures. On the other hand, the electrochemical activity and antibacterial effect E. coli of the cuboctahedral and icosahedral structures were measured experimentally. The results obtained by molecular simulation, cyclic voltammetry, and antibacterial effect were compared and discussed in this work.

Analysis for the Sorption Kinetics of Ag Nanoparticles on Natural Clinoptilolite

The kinetic adsorption behavior of silver nanoparticles deposited on a natural zeolite from Oaxaca is presented. Theoretical models as Lagergren first-order, pseudo-second-order, Elovich, and intraparticle diffusion were employed and compared with experimental data obtained by atomic absorption spectrophotometry technique. Correlation factors of the order of 0.99 were observed. Analysis by transmission electron microscopy revealed that the silver nanoparticles were homogeneously distributed on the zeolite. Additionally, chemical characterization of the material was carried out through a dilution process with lithium metaborate. An average value of 9.3 in the Si/Al ratio was observed and related to the kinetic adsorption behavior of the zeolite.

Preparation of Silver-Doped Alumina Spherical Beads with Antimicrobial Properties

The synthesis of composites with antibacterial properties is of great interest for the development of new biomedical applications. The antimicrobial properties of silver have been verified against microorganisms such as bacteria, viruses, and fungi; interest in silver has been renewed, so several technologies are currently in development, especially in dental materials. The purpose of this work was to improve the parameters for producing silver-doped alumina spherical beads using sodium alginate as a sacrificial template. Alumina is a biocompatible and thermally stable ceramic, while silver was used for its bactericidal properties. The obtained spheres presented a mean diameter of 2 mm, with an irregular surface and intertwined particles after a sintering process. After electrodeposition, white spheres turned to a dark gray color, demonstrating the presence of silver nanoparticles and fractal silver dendrites on the surface. Spheres were characterized by SEM, FTIR, and XRD. Antimicrobial activity of the alumina-AgP spheres against E. coli, S. aureus, K. pneumoniae, and S. mutans was analyzed by turbidimetry. The specific antimicrobial activity of all the composites showed specific antibacterial effects, independently of the amount of silver deposited, probably due to the differences in the microbial cell wall structures. Therefore, antibacterial activity depends on microbiological and structural characteristics of each bacterium.

Synthesis of α-Alumina Nano-Onions by Thermal Decomposition of Aluminum Formate

A simplified route to prepare α-Al2O3 nano-onions and alumina powders with an excellent surface area through the thermal decomposition of aluminum formate (Al(O2CH)3) precursor is proposed. The calcined powders were characterized by infrared and 13C MAS NMR spectroscopy. Coordination numbers and chemical interactions were determined by 27Al MAS NMR spectroscopy. The 27Al MAS NMR spectra showed the presence of η-Al2O3 at 1000°C, and the transformation to α-Al2O3 at 1100°C. The spectral data also showed that while the precursor contained 6-coordinated aluminum ions, four-, five-, and six-coordinated aluminum species were present after calcination at 400°C. SEM images and BET measurements of α-Al2O3 revealed aggregated particles with a specific surface area of 118 m2/g. A nano-onion structure of α-Al2O3 was evident from the HRTEM image.

Green Composite Based on Silver Nanoparticles Supported on Diatomaceous Earth: Kinetic Adsorption Models and Antibacterial Effect

A green synthesis of composite based on silver nanoparticles (AgNPs) obtained by Melissa officinalis (MO) extract and supported on diatomaceous earth (DE) was synthesized. Kinetic adsorption models were proposed to describe the sorption mechanism of AgNPs nanoparticles during the impregnation process. Theoretical models as pseudo first order, pseudo-second order, Elovich and intraparticle diffusion were developed to establish accurately the kinetic parameters, such as correlations factors (R2) and maximum Ag nanoparticles sorption capacity of the diatomite. According to the Kinetic adsorption parameters obtained, the pseudo-second order model reveals the best linear fit. Also, four types of pseudo-second order model were performed and analyzed. The proposed models describe with great precision, the adsorption mechanism of Ag nanoparticles during the impregnation process onto DE surface. Complementary, the antibacterial activity of the composite against Staphylococcus aureus and Escherichia coli were evaluated. The green composite (Ag nanoparticles/diatomaceous earth) was characterized by Electron Microscopy, X-Ray Diffraction and Infrared Spectroscopy.

Preparation and characterization of natural zeolite modified with iron nanoparticles

This study is aimed at investigating the structural and morphological characterization of natural and modified zeolite obtained from the state of Oaxaca (Mexico). Iron nanoparticles were used for the zeolite modification. The iron nanoparticles were loaded on the zeolite surface by homogeneous nucleation. Adsorption kinetic models of pseudo first and second order were surveyed. The characterization of pristine and modified zeolite was performed by Fourier transform infrared (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). From the results, three main phases were identified: clinoptilolite, mordenite, and feldspar. We could also determine the adsorption capacity of the zeolites by means of adsorption kinetic models.