The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antib... more The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antibacterial properties using citrus peel residues (orange, lemon, and grapefruit) as reducing and stabilizing agents, and on assessing their antibacterial activity against multidrug-resistant clinical Staphylococcus aureus. The synthesized AgNPs were analyzed by various techniques, including UV-Vis spectroscopy, SAED, TEM, XRD, FTIR, and Raman. The results demonstrate the formation of ultra-small, monodisperse, quasi-spherical AgNPs with an average particle size of 2.42 nm for AgNPs produced with mixed extracts. XRD analysis indicated that the AgNPs have a crystal size of 9.71 to 16.23 nm. The AgNPs exhibited potent inhibitory activity against resistant S. aureus, with a minimum inhibitory concentration (MIC) of 15.625 to 62.50 ppm. The findings suggest that the ultra-small nanometer size of the AgNPs could be attributed to the synthesis method that employs ambient conditions and the presen...
El aumento de la población y sus actividades con el consiguiente desarrollo del ser humano, ha pr... more El aumento de la población y sus actividades con el consiguiente desarrollo del ser humano, ha propiciado la generación y acumulación de mayores cantidades de residuos como los de tipo orgánico que pueden impactar de manera negativa al medio ambiente. Por ello, es importante fomentar estrategias más eficientes de gestión y disposición final para este tipo de residuos. Al respecto, debido a su naturaleza orgánica, estos residuos pueden contener diversos compuestos de interés que pueden ser aplicados en áreas como la nanotecnología, medicina, medio ambiente, alimentaria, farmacéutica, entre otras., por lo que su revalorización es una alternativa viable para su aprovechamiento. En este sentido, la síntesis verde de nanopartículas metálicas con propiedades interesantes tales como: antimicrobianas, antioxidantes, catalizadoras, anticancerígenas, etc, ha mostrado ser una metodología de obtención de dichos nanomateriales de una manera más amigable con el medio ambiente y con una mejor rela...
The aim of the present work is to determine the austenite to ferrite transformation temperatures ... more The aim of the present work is to determine the austenite to ferrite transformation temperatures in a Si-Al non-oriented electrical steel. Critical transformation temperatures on heating and cooling are determined using an in-situ X-ray diffraction technique where the specimen is heated or cooled in a stepwise manner. The transformation temperatures are estimated from changes in the intensities of the (110)α and (111)γ peaks as a function of temperature. The time evolution of the microstructure resulting from isothermal heat treatments at temperatures between 800 and 1000 °C applied after cooling from 1050 °C is followed by quantitative metallography on samples quenched into water. The results show that, on cooling, formation of ferrite starts at about 950 °C and ends at 790 °C, indicating a strong effect of Si and Al on the austenite to ferrite and eutectoid transformations. These results suggest that the low tensile ductility exhibited by this material at temperatures near 1000 °C...
ABSTRACT Three-dimensional (3-D) nanoarchitectures composed of self-organized hematite nanocrysta... more ABSTRACT Three-dimensional (3-D) nanoarchitectures composed of self-organized hematite nanocrystals were successfully prepared by thermally induced hydrolysis of iron (III) solutions in the presence of urea and without additional stabilizers. The size, morphology and microstructure of these nanocrystal aggregates were investigated as a function of aging time using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The evolution of the microstructural parameters, including crystallite size, root mean square strain and lattice parameters, was analyzed by the Rietveld method using the MAUD software program and adopting the size–strain–shape Popa model. In addition, vibrating-sample magnetometry measurements were carried out to examine the magnetic behavior of the nanoarchitectures. These studies suggested that the formation mechanism of the observed nanoarchitectures consisted of several self-organization processes linked in hierarchical levels. The nanocrystals within these nanoarchitectures grew in size by Ostwald ripening and subsequent grain growth when they were aged at 98 °C in tightly capped tubes for an aging time that varied from 2 h up to 45 days. The crystal morphology evolved favoring a rhombohedral shape until intergrowth between the densely packed nanocrystals occurred. Consequently, the morphology of the nanoarchitectures, their effective magnetic anisotropy, the occurrence of the Morin transition and the exchange bias effect were also strongly dependent on the aging time.
The objective of this study was to determine the oxidative stress and the physiological and antio... more The objective of this study was to determine the oxidative stress and the physiological and antioxidant responses of coriander plants (Coriandrum sativum) grown for 58 days in soil with zinc oxide nanoparticles (ZnO NPs) and zinc sulfate (ZnSO4) at concentrations of 0, 100, 200, 300, and 400 mg of Zn/kg of soil. The results revealed that all Zn compounds increased the total chlorophyll content (CHLt) by at least 45%, compared to the control group; however, with 400 mg/kg of ZnSO4, chlorophyll accumulation decreased by 34.6%. Zn determination by induction-plasma-coupled atomic emission spectrometry (ICP–AES) showed that Zn absorption in roots and shoots occurred in plants exposed to ZnSO4 at all concentrations, which resulted in high levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Only at 400 mg/kg of ZnSO4, a 78.6% decrease in the MDA levels was observed. According to the results, the ZnSO4 treatments were more effective than the ZnO NPs to increase the antioxidant act...
The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antib... more The present study centers on the synthesis of ultra-small silver nanoparticles (AgNPs) with antibacterial properties using citrus peel residues (orange, lemon, and grapefruit) as reducing and stabilizing agents, and on assessing their antibacterial activity against multidrug-resistant clinical Staphylococcus aureus. The synthesized AgNPs were analyzed by various techniques, including UV-Vis spectroscopy, SAED, TEM, XRD, FTIR, and Raman. The results demonstrate the formation of ultra-small, monodisperse, quasi-spherical AgNPs with an average particle size of 2.42 nm for AgNPs produced with mixed extracts. XRD analysis indicated that the AgNPs have a crystal size of 9.71 to 16.23 nm. The AgNPs exhibited potent inhibitory activity against resistant S. aureus, with a minimum inhibitory concentration (MIC) of 15.625 to 62.50 ppm. The findings suggest that the ultra-small nanometer size of the AgNPs could be attributed to the synthesis method that employs ambient conditions and the presen...
El aumento de la población y sus actividades con el consiguiente desarrollo del ser humano, ha pr... more El aumento de la población y sus actividades con el consiguiente desarrollo del ser humano, ha propiciado la generación y acumulación de mayores cantidades de residuos como los de tipo orgánico que pueden impactar de manera negativa al medio ambiente. Por ello, es importante fomentar estrategias más eficientes de gestión y disposición final para este tipo de residuos. Al respecto, debido a su naturaleza orgánica, estos residuos pueden contener diversos compuestos de interés que pueden ser aplicados en áreas como la nanotecnología, medicina, medio ambiente, alimentaria, farmacéutica, entre otras., por lo que su revalorización es una alternativa viable para su aprovechamiento. En este sentido, la síntesis verde de nanopartículas metálicas con propiedades interesantes tales como: antimicrobianas, antioxidantes, catalizadoras, anticancerígenas, etc, ha mostrado ser una metodología de obtención de dichos nanomateriales de una manera más amigable con el medio ambiente y con una mejor rela...
The aim of the present work is to determine the austenite to ferrite transformation temperatures ... more The aim of the present work is to determine the austenite to ferrite transformation temperatures in a Si-Al non-oriented electrical steel. Critical transformation temperatures on heating and cooling are determined using an in-situ X-ray diffraction technique where the specimen is heated or cooled in a stepwise manner. The transformation temperatures are estimated from changes in the intensities of the (110)α and (111)γ peaks as a function of temperature. The time evolution of the microstructure resulting from isothermal heat treatments at temperatures between 800 and 1000 °C applied after cooling from 1050 °C is followed by quantitative metallography on samples quenched into water. The results show that, on cooling, formation of ferrite starts at about 950 °C and ends at 790 °C, indicating a strong effect of Si and Al on the austenite to ferrite and eutectoid transformations. These results suggest that the low tensile ductility exhibited by this material at temperatures near 1000 °C...
ABSTRACT Three-dimensional (3-D) nanoarchitectures composed of self-organized hematite nanocrysta... more ABSTRACT Three-dimensional (3-D) nanoarchitectures composed of self-organized hematite nanocrystals were successfully prepared by thermally induced hydrolysis of iron (III) solutions in the presence of urea and without additional stabilizers. The size, morphology and microstructure of these nanocrystal aggregates were investigated as a function of aging time using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The evolution of the microstructural parameters, including crystallite size, root mean square strain and lattice parameters, was analyzed by the Rietveld method using the MAUD software program and adopting the size–strain–shape Popa model. In addition, vibrating-sample magnetometry measurements were carried out to examine the magnetic behavior of the nanoarchitectures. These studies suggested that the formation mechanism of the observed nanoarchitectures consisted of several self-organization processes linked in hierarchical levels. The nanocrystals within these nanoarchitectures grew in size by Ostwald ripening and subsequent grain growth when they were aged at 98 °C in tightly capped tubes for an aging time that varied from 2 h up to 45 days. The crystal morphology evolved favoring a rhombohedral shape until intergrowth between the densely packed nanocrystals occurred. Consequently, the morphology of the nanoarchitectures, their effective magnetic anisotropy, the occurrence of the Morin transition and the exchange bias effect were also strongly dependent on the aging time.
The objective of this study was to determine the oxidative stress and the physiological and antio... more The objective of this study was to determine the oxidative stress and the physiological and antioxidant responses of coriander plants (Coriandrum sativum) grown for 58 days in soil with zinc oxide nanoparticles (ZnO NPs) and zinc sulfate (ZnSO4) at concentrations of 0, 100, 200, 300, and 400 mg of Zn/kg of soil. The results revealed that all Zn compounds increased the total chlorophyll content (CHLt) by at least 45%, compared to the control group; however, with 400 mg/kg of ZnSO4, chlorophyll accumulation decreased by 34.6%. Zn determination by induction-plasma-coupled atomic emission spectrometry (ICP–AES) showed that Zn absorption in roots and shoots occurred in plants exposed to ZnSO4 at all concentrations, which resulted in high levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Only at 400 mg/kg of ZnSO4, a 78.6% decrease in the MDA levels was observed. According to the results, the ZnSO4 treatments were more effective than the ZnO NPs to increase the antioxidant act...
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Papers by Enrique Díaz Barriga-Castro