Magnetic structures synthesized by controlled oxidative etching: Structural characterization and magnetic behavior

A facile strategy for the fabrication Fe3O4 nanostructures at room temperature and with well-defined morphology is proposed. In this methodology, the iron precursors were reduced by sodium borohydride. Subsequently an oxidative etching process promotes the formation of Fe2O3 nanostructures. Magnetic measurements revealed a well-defined superparamagnetic behavior for the material. The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetization curves reveals that critical and blocking temperature were 24 and 350 °C respectively. The Fe3O4 nanostructures were characterized using aberration-corrected (Cs) scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS). Additionally, Raman spectra support the Fe3O4 presence and corroborate the efficiency of the synthesis process to obtain magnetite. Keywords: Chemical synthesis, Fe3O4 nanoparticles, Structural characterization, Magnetic propertie

Comparative Study of Ag Nanostructures: Molecular Simulations, Electrochemical Behavior, and Antibacterial Effect

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

Green synthesis of silver nanoparticles using a Melissa officinalis leaf extract with antibacterial properties

The exceptional properties of the silver nanoparticles offer several applications in the biomedicine field. The development of antibiotics which are clinically useful against bacteria and drug resistant microorganisms, it is one of the main approaches of silver nanoparticles. However, it is necessary to develop environmentally friendly methods for their synthesis. In this sense, the main objective of this work is focused on to propose a simplified and efficient green synthesis of silver nanoparticles with proven antibacterial properties. The green synthesis route is based on the use of the Melissa officinalis as reducing agent of the silver ions in aqueous solution at room temperature. Complementary, the antibacterial activity of the silver nanoparticles against Staphylococcus aureus and Escherichia coli was confirmed. The silver nanoparticles obtained were characterized by transmission electron microscopy, X-ray diffraction, UV–vis, Raman and FT-IR spectroscopy. The observed results suggested that using Melissa officinalis, it is possible to performed silver nanoparticles with controlled characteristics and with significant inhibitory activity against the Staphylococcus aureus and Escherichia coli. Keywords: Green synthesis, Nanoparticles, Antibacterial effec

Effect of Zn Nanoparticles Doping on Oxytetracycline Removal by Natural Aluminosilicate and Carbon Nanotubes

The presence of antibiotics such as oxytetracycline (OTC) in water and wastewater is considered an environmental problem and, consequently, their elimination is an important topic. The present research shows the removal of OTC from aqueous medium using a quartz-based natural aluminosilicate (Q) and carbon nanotubes (CNTs) modified with zinc nanoparticles (ZnNPs) as alternative adsorbent materials for OTC removal. The ZnNPs were synthesized by chemical reduction method and were used to modify the Q and CNT surface. There were obtained four materials (Q, Q/ZnNPs CNTs. and CNTs/ZnNPs) characterized by SEM–EDX, FTIR, DRX, and pHPZC. The adsorption behavior of OTC, as a function of drug concentration, pH, and temperature, was investigated by adsorption experiments. High adsorption capacities (qe) of OTC as 644 and 111 mg/g were obtained for CNTs and CNTs/ZnNPs, respectively. For Q and Q/ZnNPs, the maximum OTC sorption was 177 and 78 mg/g, respectively. It was found that OTC adsorption process using CNTs and CNTs/ZnNPs follows a pseudo-second-order and intraparticle diffusion, while when using the Q and Q/Zn, it follows a pseudo-first-order model. Moreover, isotherm tests were performed on distilled water and drinking water to evaluate the effect of ionic strength. The obtained data were adjusted to Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich isotherm equations, being Freundlich the isotherm that describes the OTC sorption process. The results obtained were indicative of a good OTC adsorption capacity by the alternative prepared materials

Cell behavior on silica-hydroxyapatite coaxial composite.

Progress in the manufacture of scaffolds in tissue engineering lies in the successful combination of materials such as bioceramics having properties as porosity, biocompatibility, water retention, protein adsorption, mechanical strength and biomineralization. Hydroxyapatite (HA) is a ceramic material with lots of potential in tissue regeneration, however, its structural characteristics need to be improved for better performance. In this study, silica-hydroxyapatite (SiO2-HA) non-woven ceramic electrospunned membranes were prepared through the sol-gel method. Infrared spectra, scanning electron microscopy and XRD confirmed the structure and composition of composite. The obtained SiO2-HA polymeric fibers had approximately 230±20 nm in diameter and were then sintered at 800°C average diameter decreased to 110±17 nm. Three configurations of the membranes were obtained and tested in vitro, showing that the composite of SiO2-HA fibers showed a high percentage of viability on a fibroblast cell line. It is concluded that the fibers of SiO2-HA set in a coaxial configuration may be helpful to develop materials for bone regeneration

Eco-friendly synthesis of Fe3O4 nanoparticles: Evaluation of their catalytic activity in methylene blue degradation by kinetic adsorption models

In this work the green synthesis of Fe3O4 nanoparticles by cynara cardunculus leaf extract is presented. This green synthesis route offers a novel and eco-friendly alternative to obtaining of iron oxides nanoparticles. Functional nanoparticles with potential catalytic applications, particularly for water remediation containing organic dyes were synthetized. The structural characterization of the Fe3O4 nanoparticles were carried out by scanning electron microscopy (SEM), X-ray diffraction, techniques. Calculation to obtaining the crystallite size by Williamson –Hall method were performed. Additionally, Raman spectroscopy support the Fe3O4 characterization. Posteriorly, the Fe3O4 nanoparticles were evaluated on the methylene blue degradation. Kinetic adsorption models were employed to establish the behavior during the methylene blue degradation process. Pseudo first order, Pseudo second order, Intraparticle diffusion and Elovich Models were calculated based on the experimental data obtained. Calculations as the correlation factor indicates the best linear fit between the theoretical models and the experimental data obtained during the blue methylene degradation. Keywords: Green synthesis, Fe3O4 nanoparticles, Kinetic adsorption models, Methylene blue degradatio

Novel biosynthesis of Ag-hydroxyapatite: Structural and spectroscopic characterization

Silver-doped hydroxyapatite (Ag-HAP) was obtained by green synthesis route. The dopant silver nanoparticles (AgNPs) were obtained by biosynthesis based on Melissa officinalis extract. This research is focused on the characterization and the use of the nontoxic and environment-friendly Ag-HAP nanocomposite. The structural and morphological characterization of Ag-HAP nanocomposite was carried out by scanning electron microscopy (SEM), X-ray diffraction, Fourier-transform infrared (FT-IR) and Raman spectroscopy. The obtained nanoparticles exhibited a great interaction with the HAP matrix, performing an Ag-HAP nanocomposite. Changes in the structure of the Ag-HAP nanocomposite were corroborated by the different characterization techniques. Additionally, a homogeneous distribution of the AgNPs on the HAP structure was observed. The heterogeneous nucleation process employed to doping the HAP, offer a functional route to obtain a green composite with potentials applications in multiple fields, such as tissue engineering, bone repair as well as protein. These properties can be evaluated in subsequent studies. Keywords: Green synthesis, Ag nanoparticles, Hydroxyapatite, Structural characterization, Spectroscop

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

Biosynthesis of Ag nanoparticles using Cynara cardunculus leaf extract: Evaluation of their antibacterial and electrochemical activity

The present study reports the green synthesis of silver nanoparticles (AgNP’s) using Cynara cardunculus leaf extract in aqueous media. The silver ions reduction was carried out by the antioxidant component presents in the Cynara cardunculus. Transmission electron micrographs revealed that the synthesized AgNP’s exhibits semi-spherical morphology and the particle size was less than 45 nm. The energy dispersive X-ray analysis (EDS) spectrum revealed the presence of silver. Complementary, The AgNP’s solution exhibited an absorption peak at 435 nm, corresponding to surface plasmon resonance of AgNP’s. Fourier transform infrared (FT-IR) spectra showed the presence of the organic components responsible for reduction and stabilizing the nanoparticles. X-ray photoelectron spectroscopy (XPS) was employed to elucidate the chemical state and near surface composition of the AgNP’s obtained from Cynara cardunculus leaf extract. The antibacterial effect of the AgNP’s synthesized was tested by the disk diffusion method against E. Coli and S. Aureus bacteria. The electrochemical response of the nanoparticles was evaluated by cyclic voltammogram. The antibacterial and electrochemical activity of the AgNP’s were described in this work. Keywords: Silver nanoparticles, Green synthesis, Antibacterial activity, Electrochemical respons