Environmental behavior of coated NMs: Physicochemical aspects and plant interactions.

The application of nanomaterials (NMs) depends on several characteristics, including polydispersity, shape, surface charge, and composition, among others. However, the specific surface properties of bare NMs induce aggregation, reducing their utilization. Thus, different surface coverages have been developed to avoid or minimize NMs aggregation, making them more stable for the envisioned applications. Carbon-based NMs are usually coated with metals, while metal-based NMs are coated with natural organic compounds including chitosan, dextran, alginate, or citric acid. On the other hand, the coating process is expected to modify the surface properties of the NMs; several coating agents add negative or positive charges to the particles, changing their interaction with the environment. In this review, we analyze the most recent literature about coating processes and the behavior of coated NMs in soil, water, and plants. In particular, the behavior of the most commercialized metal-based NMs, such as TiO2, ZnO, CeO2, CuO, Ag, and Au, and carbon-based NMs are discussed in this review. The available articles about the effects of coated NMs in plants are discussed. Up to now, there is no uniformity in the information to ensure that the surface coverage increases or decreases the effects of NMs in plants. While some parameters are increased, others are decreased. Since the data is contradictory in some cases, the available literature does not allow researchers to determine what concentrations benefit the plants. This review highlights current results and future perspectives on the study of the effects of coated NMs in the environment.

Síntesis, caracterización y evaluación de la actividad antimicrobianade las cuentas porosas de MgO -alginato de calcio / Synthesis, characterization, and assessment of the antimicrobial activity of MGO – calcium alginate porous beads

La dispersión de nanopartículas antibacterianas en matrices poliméricas biocompatibles, no tóxicas y biodegradables permitirá el desarrollo de materiales más eficientes y efectivos para la conservación de alimentos, la eliminación de contaminantes y la protección contra microorganismos que comprometen la salud humana. Los materiales bactericidas nanométricos tienen una relación superficie / volumen muy grande que les permite interactuar con más copias de moléculas biológicas, y por lo tanto, mejorar la eficacia antimicrobiana. Más recientemente, se ha sugerido la actividad antimicrobiana del MgO amigable con el medio ambiente y químicamente estable. La incorporación de compuestos bactericidas en una matriz polimérica puede combinar la estabilidad física proporcionada por la matriz polimérica con las propiedades antimicrobianas de los agentes antimicrobianos dispersados como partýculas pequeñas sólidas. Sobre esta base, la presente investigación se centrará en el desarrollo de mezclas de partículas inorgánicas poliméricas biocompatibles, los denominados nanocompuestos, con actividad antimicrobiana sintonizable y mejorada. Se confirmó la actividad antimicrobiana de perlas de alginato cálcico -MgO (que oscilaban entre 0% y 40% p / p MgO) contra E. coli. Las perlas que contenían 20% p / p de MgO inhibían completamente el crecimiento bacterial de la E. coli.

The dispersion of antibacterial nanoparticles into bio-compatible, non-toxic and bio-degradable polymeric matrices will enable the development of more efficient and effective materials for food preservation, removal of contaminants, and protection against human health-compromising microorganisms. Nanometric bactericidal materials have a very large surface to volume ratio that enable them to attach more copies of biological molecules, and hence, enhance antimicrobial efficiency. More recently, the antimicrobial activity of environmental-friendly and chemically stable MgO has been suggested. The incorporation of bactericidal compounds into a polymeric matrix can combine physical stability provided by the polymeric matrix with the antimicrobial properties of antimicrobial agents dispersed as solid tiny particles. On this basis, the present research will be focused on the development of biocompatible polymer-inorganic particle mixtures, so-called nanocomposites, with tunable and enhanced antimicrobial activity.The antimicrobial activity of calcium alginate –MgO beads (ranging from 0% -40% w/w MgO) against E. coli was confirmed. Beads containing 20% w/w of MgO fully inhibited the E. coli. bacterial growth.

Antimicrobial nanomaterials as water disinfectant: applications, limitations and future perspectives.

Nanotechnology and its application is one of the rapidly developing sciences. As demand of fresh drinking water is increasing, nanotechnology can contribute noticeable development and improvement to water treatment process. Disinfection process is the last and most important step in water and wastewater treatment process. Some nanomaterials can be used as disinfectants due to their antimicrobial properties and reduce the possibility of harmful disinfection by-products (DBPs) formation during traditional disinfection process. A significant number of research efforts is done or going on to understand the mechanisms and enhance the efficiency of nanomaterials as antimicrobial agents, although it will take more time to understand the full potential of nanomaterials in this field. This review paper focuses on inactivation pathways of benign nanomaterials, their possible and probable application and limitations as disinfectants and future opportunities for their application in water cleaning processes.

Quantum dots of ZnSe(S) doped with copper as nanophotocatalyst in the degradation of organic dyes.

Copper-doped quantum dots of ZnSe(S) synthesized via microwave-heating conditions were used as photocatalyst in the photo-degradation of methylene blue (MB), methyl violet (MV) and victoria blue (VB) under UV irradiation (302 nm) in aqueous phase and at pH 6.5. Quantum dots were characterized by High Resolution Transmission Electron Microscopy (HR-TEM), X-ray diffraction (XRD), UV-Vis, photoluminescence and Fourier transform infrared (FT-IR) spectroscopy. The degradation of MB, MV and VB were monitored using High Performance Liquid Chromatography (HPLC) at 660 nm, 590 nm and 610 nm, respectively. Degradations percentages of 46%, 88% and 90% of MB, MV and VB, respectively, were achieved in presence of 1000 mg/L of quantum dots and 6 hours of UV-irradiation. Cu-doped ZnSe(S) QDs evidenced a remarkable capability to degrade cationic organic dyes as single components and in mixtures.

Sorption study of toluene and xylene in aqueous solutions by recycled tires crumb rubber.

Sorption of toluene and xylene by tire crumb rubber (TCR) and its main components: carbon black (CB) and styrene-butadiene polymer (SBP) were evaluated. The 12 starting concentrations of adsorbates in aqueous solutions ranged from 0.05 mg/L to 100.0mg/L. The amounts of CB and SBP used in the sorption tests were determined considering their typical contents in tire crumb rubber (30% and 60% w/w, respectively). Freundlich's isotherms and Scatchard plot parameters suggested a two-step sorption process when TCR was used as the sorbent; whereas a single-step route was apparent when the sorption experiments were carried out with CB or SBP. Freundlich's n parameter was estimated at 0.65 for CB and 1.0 for both TCR and SBP. A removal of 60% of toluene and 81% of xylene from starting 50 ppm solutions was attained in the first 30 minutes of contact using 5 g/L of TCR.

Synthesis of size-controlled cobalt ferrite particles with high coercivity and squareness ratio.

Cobalt ferrite particles with diameters ranging from a few micrometer to about 15 nm were synthesized using a modified oxidation process. The fine control of the particle size was achieved by introducing various concentrations of Fe(3+) ions at the beginning of the reaction. Among the particle sizes obtained by using this method, particles with a grain size of about 36 nm showed a magnetization (M(s)) of 64 emu/g and a maximum coercivity (H(c)) of 2020 Oe at room temperature. The corresponding squareness ratio was found to be 0.53.