Photocatalytic activity of silver nanoparticles@cellulose nanocomposites, from pistachio husk, in the toxic azo commercial dye degradation.

In this work, an over-the-counter commercial dye, containing direct blue 151 in its composition, which is also discarded without any environmental regulation, was efficiency photodegraded using a green chemistry-synthesized nanocomposites type silver nanoparticles (AgNPs) supported on pistachio husk (PH). The green synthesis (GS) of the nanocomposites was carried out using the Anemopsis californica leaf extract (ExAc) as a reducing-stabilizing agent (AgNPs/ExAc-PH), for the first time. The presence of AgNPs on the nanocomposite surface was corroborated by field emission transmission electron microscope (FE-TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized AgNPs/ExAc-PH has a bimodal size of 24 and 25 nm (4.86 % each) and a 0.72 % of AgNPs on its surface. AgNPs were adhered to the PH surface, through secondary bonds between the Ag and the cellulose of the PH. The optimum conditions, for efficient photocatalytic degradation, were 5 mg of nanocomposite, 3.18 × 10-2 M of NaBH4, natural sunlight, and stirring; this results in a photodegradation efficiency of 100 % almost instantaneously. Furthermore, it was shown that the dye degradation process is primarily due to the photocatalytic degradation of the dye, which occurs almost instantaneously.

Photocatalytic Activity and Biocide Properties of Ag-TiO2 Composites on Cotton Fabrics.

Composites of Ag and TiO2 nanoparticles were synthesized in situ on cotton fabrics using sonochemical and solvothermal methods achieving the successive formation of Ag-NPs and Ti-NPs directly on the fabric. The impregnated fabrics were characterized using ATR-FTIR spectroscopy; high-resolution microscopy (HREM); scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS); Raman, photoluminescence, UV-Vis, and DRS spectroscopies; and by tensile tension tests. Results showed the successful formation and impregnation of NPs on the cotton fabric, with negligible leaching of NPs after several washing cycles. The photocatalytic activity of supported NPs was assessed by the degradation of methyl blue dye (MB) under solar and UV irradiation revealing improved photocatalytic activity of the Ag-TiO2/cotton composites due to a synergy of both Ag and TiO2 nanoparticles. This behavior is attributed to a diminished electron-hole recombination effect in the Ag-TiO2/cotton samples. The biocide activity of these composites on the growth inhibition of Staphylococcus aureus (Gram+) and Escherichia coli (Gram-) was confirmed, revealing interesting possibilities for the utilization of the functionalized cotton fabric as protective cloth for medical applications.

Characterization and photocatalytic activity of TiO2 nanoparticles on cotton fabrics, for antibacterial masks.

The in-situ impregnation of two commercial cotton fabrics (lab coat and Indiolino) with TiO2 nanoparticles (TiO2-NPs) was carried out. For this, two commercial cotton fabrics were dipped in titanium isopropoxide, titanium butoxide and titanium tetrachloride solutions to the TiO2-NPs formation and in-situ TiO2-NPs impregnation on the cotton fabric surface by the sonochemical, hydrothermal and solvothermal methods, respectively. The impregnated fabrics were characterized by ATR-FTIR, SEM-EDS, Raman, UV-Vis, DRS and tension tests. The results showed the successful formation and impregnation of TiO2-NPs on both cotton fabrics. The leaching of TiO2-NPs from cotton fabrics was negligible after several washing cycles. The self-cleaning properties and antibacterial activity of TiO2-NPs functionalized cotton fabrics were assessed by photocatalytic and antibacterial tests. The photocatalytic activity was determined by the degradation of methylene blue dye under UV and solar irradiation. The materials showed good photoactivity, since MB was degraded up to 99% under solar and UV irradiations in 60 min. The bactericidal capacity of the TiO2-NPs on fabrics, evaluated in-situ by SEM, showed that Indiolino presented the best antibacterial properties against Escherichia coli and Bacillus pumilus.

The effect on the electrocatalytic activity of the chemical interaction of selenium with palladium centers: oxygen reduction and methanol oxidation reactions in alkaline medium.

The chemical reactivity of two different selenium precursors (SeO2and Se) with nanoparticulated palladium was studied in a simple aqueous phase synthesis to generate palladium selenides (PdxSey). As confirmed by XRD, XPS, TEM and energy dispersive spectroscopy analyses, the products generated showed different degrees of selenization according to the nature of the chemical precursor. Such degree of selenization was more important with elemental selenium, in contrast to SeO2. Surface electrochemistry and CO stripping in alkaline medium, clearly revealed the different interactions and stability of PdxSeyachieved with the Pd/C precursor depending on the selenium source. The electrocatalysis of the oxygen reduction reaction was also influenced by the Se source, first in the different degree of reactivity, and second in the selectivity of the reduction product between H2O and H2O2, as well as the tolerance to the methanol oxidation reaction.

A fluorescent PET probe based on polyethyleneimine-Ag nanoclusters as a reversible, stable and selective broad-range pH sensor.

In this work, nanoclusters (NCs) of Cu and Ag capped with hyperbranched polyethyleneimine (PEI) were prepared using chemical reduction by a one-step hydrothermal method. The PEI coated-NCs were characterized by high-resolution transmission electron microscopy, ζ potential, thermogravimetric analysis, dynamic light scattering, Fourier-transform infrared, UV-visible, and fluorescence spectroscopy. The PEI-NCs exhibited strong absorption and fluorescence, high stability, and excellent water dispersibility. The resulting PEI-NCs showed a reversible and linear response of fluorescence intensity with pH over a wide range (3-11); however, PEI-AgNCs showed a better reversibility and sensitivity than PEI-CuNCs. Unlike several types of pH sensors based on modified NCs, which are based on a nanoparticle aggregation/disaggregation mechanism, the response of our sensor is based on a photoinduced electron transfer process, which gives it a high reversibility. This method was successfully applied in pH measurements in tap water and green tea samples, with excellent results, indicating its practical utility for these applications. A visual device was obtained by immobilizing PEI-AgNCs into agarose hydrogels at different pH values. The results show that the proposed sensor can be used as a pH visual detector. Besides, the light emission of the nanosensor was corroborated by fluorescence microscopy, confirming that the nanosensor based on PEI-AgNCs has great potential to be used in cellular imaging.

Synthesis of covalent bonding MWCNT-oligoethylene linezolid conjugates and their antibacterial activity against bacterial strains.

Nowadays, infectious diseases caused by drug-resistant bacteria have become especially important. Linezolid is an antibacterial drug active against clinically important Gram positive strains; however, resistance showed by these bacteria has been reported. Nanotechnology has improved a broad area of science, such as medicine, developing new drug delivery and transport systems. In this work, several covalently bounded conjugated nanomaterials were synthesized from multiwalled carbon nanotubes (MWCNTs), a different length oligoethylene chain (S n ), and two linezolid precursors (4 and 7), and they were evaluated in antibacterial assays. Interestingly, due to the intrinsic antibacterial activity of the amino-oligoethylene linezolid analogues, these conjugated nanomaterials showed significant antibacterial activity against various tested bacterial strains in a radial diffusion assay and microdilution method, including Gram negative strains as Escherichia coli (11 mm, 6.25 µg mL-1) and Salmonella typhi (14 mm, ≤0.78 µg mL-1), which are not inhibited by linezolid. The results show a significant effect of the oligoethylene chain length over the antibacterial activity. Molecular docking of amino-oligoethylene linezolid analogs shows a more favorable interaction of the S 2-7 analog in the PTC of E. coli.

Modeling the ternary chalcogenide Na2MoSe4 from first-principles.

In the ongoing pursuit of inorganic compounds suitable for solid-state devices, transition metal chalcogenides have received heightened attention due to their physical and chemical properties. Recently, alkali-ion transition metal chalcogenides have been explored as promising candidates to be applied in optoelectronics, photovoltaics and energy storage devices. In this work, we present a theoretical study of sodium molybdenum selenide (Na2MoSe4). First-principles computations were performed on a set of hypothetical crystal structures to determine the ground state and electronic properties of Na2MoSe4. We find that the equilibrium structure of Na2MoSe4 is a simple orthorhombic (oP) lattice, with space group Pnma, as evidenced by thermodynamics. Finally, meta-GGA computations were performed to model the band structure of oP Na2MoSe4 at a predictive level. We employ the Tran-Blaha modified Becke-Johnson potential to demonstrate that oP Na2MoSe4 has a direct bandgap at the Γ point that is suitable for optoelectronics. Our results provide a foundation for future studies concerned with the modeling of inorganic and hybrid organic-inorganic materials chemically analogous to Na2MoSe4.

Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres.

In this research, we report a simple hydrothermal synthesis to prepare rhenium (Re)- doped MoS2 flower-like microspheres and the tuning of their structural, electronic, and electrocatalytic properties by modulating the insertion of Re. The obtained compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Structural, morphological, and chemical analyses confirmed the synthesis of poorly crystalline Re-doped MoS2 flower-like microspheres composed of few stacked layers. They exhibit enhanced hydrogen evolution reaction (HER) performance with low overpotential of 210 mV at current density of 10 mA/cm2, with a small Tafel slope of 78 mV/dec. The enhanced catalytic HER performance can be ascribed to activation of MoS2 basal planes and by reduction in charge transfer resistance during HER upon doping.

New Insight on the Formation of Sodium Titanates 1D Nanostructures and Its Application on CO2 Hydrogenation.

The aim of this work is focused on the study of a series of non-traditional catalytic nanomaterials to transform greenhouse CO2 gas into added-value products. We found encouraging results of CO2 hydrogenation activity over sodium titanates with different morphologies. The yield to methanol increases with the increase in the Na incorporated in the nanostructures confirming the proposed mechanism. Samples were prepared at different times of hydrothermal treatment (HTT) with NaOH solutions, and these materials were labeled as Ti-nR-x with x as the hours on the HTT. HRTEM initially showed sphere-shaped nanoparticles in the TiO2 commercial nanopowder, increasing the HTT resulted in morphological changes in which the structures passed from nanosheets and finally to nanorods after 30 h. The X-ray diffraction and Raman spectroscopy results indicated the formation of sodium titanates such as Na2Ti3O7 with short Ti-O bonds and that Na begins to be incorporated into the distorted TiO6 crystalline structure after 5 h of HTT (until 12 wt%). The crystalline and shape transformation resulted in a significant modification on the textural properties passing from 51 m2.g-1 to 150 m2.g-1 and from a pore volume of 0.12 cm3.g-1 to 1.03 cm3.g-1 for Ti-ref and Ti-nR-30 respectively. We also observed differences in the electronic properties as the bandgap presented a blue shift from 3.16 eV on the TiO2 reference nano-powder to 3.44 eV for the Ti-nR-30 calcined sample. This fact coincides with the presence of a more electron-rich state of the Ti4+ and the formation of negative charge layer induced by the presence of Na+ interlayer cations detected by XPS analysis, at the same this helped us to explain the catalytic activity results.

N-Doped carbon nanotubes enriched with graphitic nitrogen in a buckypaper configuration as efficient 3D electrodes for oxygen reduction to H2O2.

Herein, a series of N-doped carbon nanotube (CNx) samples were obtained by modifying the synthesis temperature. Consequently, the proportion of graphitic nitrogen (Ngraph) in the samples was systematically increased as a function of temperature. This allowed evaluation of the role of the CNx graphitic nitrogen in the oxygen reduction reaction (ORR). A correlation between the Ngraph content and the ORR onset potential was observed, which shifted to more positive potentials with an increase in kinetic current density (jk); this showed that Ngraph played a significant catalytic role in the ORR. The samples with high Ngraph content favored the two-electron pathway for the ORR not only in basic media (pH = 13) but also in neutral media (pH = 7), representing an attractive alternative for wastewater remediation through the on-site generation of H2O2. The energetic calculations showed that the formation of H2O2 must be favorable in the presence of graphitic nitrogen sites. Finally, the performance of the buckypaper arrangement was evaluated, and the CNx buckypaper showed a higher cathodic current peak as compared to CNx traditional ink dispersions. Overall, this study not only sheds light on the role of Ngraph in the ORR, but also demonstrates that CNx buckypaper is an efficient 3D electrode for electrocatalytic applications.

Feasibility of a multifaceted educational strategy for strengthening rural primary health care.

OBJECTIVE:: To evaluate the feasibility and acceptability of a comprehensive educational strategy designed to improve care quality in rural areas of Mexico. MATERIALS AND METHODS:: A demonstration study was performed in 18 public rural health centers in Mexico, including an educational intervention that consists of the following steps: Development of the strategy; Selection and training of instructors (specialist physicians from the referral hospital and multidisciplinary field teams); Implementation of the strategy among health care teams for six priority causes of visit, through workshops, individual tutorials, and round-table case-review sessions. Feasibility and acceptability were evaluated using checklists, direct observation, questionnaires and in-depth interviews with key players. RESULTS:: Despite some organizational barriers, the strategy was perceived as worthy by the participants because of the personalized tutorials and the improved integration of health teams within their usual professional practice. CONCLUSION:: The educational strategy proved to be acceptable; its feasibility for usual care conditions will depend on the improvement of organizational processes at rural facilities.

Biological effects of carbon nanotubes generated in forest wildfire ecosystems rich in resinous trees on native plants.

Carbon nanotubes (CNTs) have a broad range of applications and are generally considered human-engineered nanomaterials. However, carbon nanostructures have been found in ice cores and oil wells, suggesting that nature may provide appropriate conditions for CNT synthesis. During forest wildfires, materials such as turpentine and conifer tissues containing iron under high temperatures may create chemical conditions favorable for CNT generation, similar to those in synthetic methods. Here, we show evidence of naturally occurring multiwalled carbon nanotubes (MWCNTs) produced from Pinus oocarpa and Pinus pseudostrobus, following a forest wildfire. The MWCNTs showed an average of 10 walls, with internal diameters of ∼2.5 nm and outer diameters of ∼14.5 nm. To verify whether MWCNT generation during forest wildfires has a biological effect on some characteristic plant species of these ecosystems, germination and development of seedlings were conducted. Results show that the utilization of comparable synthetic MWCNTs increased seed germination rates and the development of Lupinus elegans and Eysenhardtia polystachya, two plants species found in the burned forest ecosystem. The finding provides evidence that supports the generation and possible ecological functions of MWCNTs in nature.

Effect of acute and long-term administration of gold nanoparticles on biochemical parameters in rat brain.

The present study investigated stress oxidative parameters and activities of enzymes of the energy metabolism in various brain structures. Rats were subjected to acute and long-term administration of gold nanoparticles (GNPs) with mean diameters of 10nm and 30nm. Adult (60days old) male Wistar rats received a single intraperitoneal injection (acute administration; 70µg·kg-1) or repeated injections once daily for 28days (long-term administration; 70µg·kg-1) of saline solution or GNPs (10nm or 30nm). Twenty-four hours after administration of the final dose, the animals were killed and the cerebral structures were isolated for enzyme analysis. In this study, we observed that the thiobarbituric acid-reactive species and carbonyl protein levels were decreased after acute administration of GNPs, whereas the superoxide dismutase activity was increased after acute and long-term of GNPs. The catalase activity was affected by the administration of GNPs. Furthermore, we have not found change in the citrate synthase activity. The succinate dehydrogenase, malate dehydrogenase, complexes I, II, II-III and IV, and creatine kinase activities were altered. These results indicate that inhibition energy metabolism can be caused by oxidative stress.

Feasibility of a multifaceted educational strategy for strengthening rural primary health care / Factibilidad de una estrategia educativa multifacética para fortalecer la atención primaria rural

Abstract: Objective: To evaluate the feasibility and acceptability of a comprehensive educational strategy designed to improve care quality in rural areas of Mexico. Materials and methods: A demonstration study was performed in 18 public rural health centers in Mexico, including an educational intervention that consists of the following steps: Development of the strategy; Selection and training of instructors (specialist physicians from the referral hospital and multidisciplinary field teams); Implementation of the strategy among health care teams for six priority causes of visit, through workshops, individual tutorials, and round-table case-review sessions. Feasibility and acceptability were evaluated using checklists, direct observation, questionnaires and in-depth interviews with key players. Results: Despite some organizational barriers, the strategy was perceived as worthy by the participants because of the personalized tutorials and the improved integration of health teams within their usual professional practice. Conclusion: The educational strategy proved to be acceptable; its feasibility for usual care conditions will depend on the improvement of organizational processes at rural facilities.

Resumen: Objetivo: Evaluar la factibilidad y aceptabilidad de una estrategia educativa multifacética de mejora de calidad de atención en áreas rurales de México. Material y métodos: Se realizó un estudio de demostración con una intervención educativa a equipos de salud en 18 centros de salud rurales en México, que incluyó desarrollo de la estrategia; selección y capacitación de instructores (especialistas del hospital de referencia y equipos asesores multidisciplinarios); implementación de la estrategia educativa para seis motivos prioritarios de atención, mediante talleres, asesorías individualizadas y sesiones de revisión de casos. Se evaluaron factibilidad y aceptabilidad mediante listas de cotejo, observación directa, cuestionarios y entrevistas a profundidad con actores clave. Resultados: A pesar de algunas barreras organizacionales, la estrategia fue percibida como valiosa por los participantes, por la asesoría personalizada y la integración de los equipos de salud en su práctica profesional. Conclusión: La estrategia educativa es aceptable para áreas rurales; su factibilidad en la operación usual dependerá de mejoras organizacionales de los servicios.

Multi-Walled Carbon Nanotube Functionalization by Radical Addition Using Hydroxymethylene Groups.

Synthetic methodology and characterization of multi-walled carbon nanotubes (MWCNTs) function- alized with hydroxymethylene groups are reported. The MWCNTs were synthesized by the spray pyrolysis technique using toluene as carbon source and ferrocene as catalyst. Hydroxymethylation of MWCNTs was carried out by methanol using benzoyl peroxide (BPO) at different quantities (300 to 900 mg); the optimum BPO quantity was 300 mg. The resulting materials were characterized by FT-IR, Raman Spectroscopy, Thermal Gravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM). The presence of the hydroxymethylene group on the MWCNTs surface was demonstrated by FT-IR, Raman Spectroscopy, TGA, EDS, TEM and Mass Spectrometry. The func- tionalized MWCNTs were not damaged by this methodology.

Green Synthesis of Silver Nanoparticles: Effect of Dextran Molecular Weight Used as Stabilizing-Reducing Agent.

This paper describes an easy green chemistry method for the synthesis of silver nanoparticles (AgNPs). The AgNPs were obtained through the use of an aqueous silver nitrate solution (AgNO3), with dextrans aqueous solutions of different molecular weights acting as stabilizing and reducing agent, employing the chemical reduction method. We made a comparative study to determine which molecular weight dextran was the best stabilizing and reducing agent, and it was found that the molecular size of the stabilizing agent is inversely proportional to the size of the nanoparticle synthesized. The formation of the AgNPs was demonstrated by UV-Vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). SEM-EDS analysis shows the formation of particles with dendritic structure. TEM shows nanoparticles which are spherical in shape and 1-10 nm in size; also, the clear lattice fringes show highly crystalline AgNPs (FCC).

Synthesis, kinetics and photocatalytic study of "ultra-small" Ag-NPs obtained by a green chemistry method using an extract of Rosa 'Andeli' double delight petals.

This paper reports the effect of different concentrations of Rosa 'Andeli' double delight petals aqueous extract (PERA) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. Its kinetics study and photocatalytic activity were also evaluated. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with 9.66% w/v, 7.25% w/v, and 4.20% w/v PERA as both reducing-stabilizing agent. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). TEM analysis shows spherical nanoparticles in shape and size between ∼0.5 and 1.4nm. A comparative study was done to determine which concentration was the best reducing-stabilizing agent, and we found out that "ultra-small" nanoparticles (0.5-1.1nm) were obtained with 9.66% w/v of PERA. The size of the Ag-NPs depends on the concentration of PERA and Ag(I). The reaction of formation of "ultra-small" Ag-NPs, proved to be first order for metallic precursor (silver) and second order for reducing-stabilizing agent (PERA). The Ag-NPs showed photocatalytic activity, in degradation of commercial dye with an efficiency of 95%.

A biosensor based on Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes and graphene oxide for polyphenol detection.

The use of nanomaterials allows the design of ultrasensitive biosensors with advantages in the detection of organic molecules. Catechol and catechin are molecules that occur naturally in fruits, and their presence in products like dyes and wines affects quality standards. In this study, catechol and catechin were measured at the nanoscale by means of cyclic voltammetry. The oxidation of Coriolopsis gallica laccase immobilized on nitrogen-doped multiwalled carbon nanotubes (Lac/CN x -MWCNT) and on graphene oxide (Lac/GO) was used to measure the concentrations of catechol and catechin. Nitrogen-doped multiwalled carbon nanotubes (CN x -MWCNT) were synthesized by spray pyrolysis and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS). Covalently bonded hybrids with laccase (Lac/CN x -MWCNT and Lac/GO) were generated. Catalytic activity of free enzymes determined with syringaldazine yielded 14 584 UmL-1. With Lac/CN x -MWCNT at concentrations of 6.4 mmol L-1 activity was 9326 U mL-1, while enzyme activity measured with Lac/GO at concentration of 6.4 mmol L-1 was 9 234 U mL-1. The Lac/CN x -MWCNT hybrid showed higher stability than Lac/GO at different ethyl alcohol concentrations. The Lac/CN x -MWCNT hybrid can measure concentrations, not previously reported, as low as 1 × 10-8 mol L-1 by measuring the electric current responses.