Green synthesis of gold nanoparticles via Moringa oleifera seed extract: antioxidant, antibacterial and anticarcinogenic activity on lung cancer.

Plant-mediated biosynthesis of nanoparticles is a green method that allows synthesis in one-pot process. Synthesis of gold nanoparticles with plant extracts has gained interest in the field of biomedicine due to its variety of applications. This study presents the synthesis via green chemistry of gold nanoparticles (AuNPs) using the methanol extract of Moringa oleifera seeds. The AuNPs were synthesized at room temperature. UV-Vis spectroscopy confirmed the formation of AuNPs by identifying the surface plasmon resonance located at 546 nm. TEM analysis shows spherical nanoparticles. FTIR analysis demonstrated the presence of specific bioactive molecules responsible for the Au3+ ion reduction process. The antioxidant activity of the nanoparticles was evaluated on the stabilization of the DPPH radical (1,1-diphenyl-2-picrylhydrazyl, 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl). The antimicrobial activity analysis was developed by broth microdilution method at different concentrations against Escherichia coli and Staphylococcus aureus. Minimum inhibitory concentration were 400 µg/mL and 200 µg/mL, respectively. A549 lung cancer cell proliferation was measured according to the MTT protocol, indicating a dose-dependent response and a IC50 of 163.9 ± 13.27 µg/mL. The AuNPs synthesized using M. oleifera seeds showed promise as active materials for antimicrobial or anticancer products.

Bactericidal and fungicidal capacity of Ag2O/Ag nanoparticles synthesized with Aloe vera extract.

This research aims to provide an alternative eco-friendly way to obtain silver species and assess their bactericidal activity. This study reports the synthesis of Ag2O nanoparticles and Ag nanoparticles reduced with a green synthesis method, using a low-cost and commercial Aloe vera extract. The crystalline phases of Ag and Ag2O nanoparticles were analyzed by X-ray diffraction. The oxidation states for both species were determined by X-ray photoelectron spectroscopy. The optical properties of the material were studied through optical absorption, which resulted in well-defined band centered at 545 nm. This result is attributed to the morphology and size of the silver nanoparticles. In addition, antibacterial tests were performed on AgNPs biosynthesized with A. vera with the Kirby-Bauer protocol on Gram-negative and Gram-positive bacteria Escherichia coli and Staphylococcus aureaus, respectively. Moreover, antifungal tests were performed with various species from Candida.

Nanowire networks and hollow nanospheres of Ag-Au bimetallic alloys at room temperature.

Due to their physicochemical properties, metallic nanoalloys have potential applications in biomedicine, electrocatalysis and electrochemical sensors, among many other fields. New alternative procedures have emerged in order to reduce production costs and the use of toxic substances. In this study we present a novel low-toxicity synthesis method for the fabrication of nanowire networks (NWNs) and Ag-Au hollow nanospheres. The synthesis process is performed at room temperature without any sophisticated equipment, such as special cameras or furnaces, etc. Transmission electron microscopy showed that the NWNs contain random alloys with a diameter of between 10-13 nm. The radius for the hollow nanospheres is approximately located between 70-130 nm. The absorption bands in the UV-vis spectrum associated with the surface plasmon in Ag-Au bimetallic nanoparticles are highlighted at 385 nm for the NWNs and 643 nm for the hollow nanospheres. The study was performed with low-toxicity substances, such as rongalite, ascorbic acid and sucrose, and showed high efficiency for the fabrication of these types of nanostructures, as well as good stability for long periods of time.

Pb/Pb3O4 Metal-Semiconductor Nanocomposite Obtained on 4A Zeolite-Optical and Structural Properties.

This work describes a controlled and low-cost synthesis method to obtain Pb/Pb3O4 nanocomposites using synthetic zeolite 4A. The nanostructures obtained have a core-shell configuration with 5-25 nm diameters. High-resolution transmission electron microscopy (HRTEM), BF, high-angle annular dark-field annular scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible (UV-vis) characterization techniques were used. Crystallographic planes (111), (200), and (220) for the core and planes (110) and (211) for the shell, corresponding to FCC and tetragonal structures for Pb and Pb3O4, respectively, were determined using HRTEM. The HAADF-STEM images allowed the analysis of intensity contrast images proportional to the number of atoms. XPS spectral analysis showed a 4.8 eV difference in binding energy between Pb 4f7/2 and Pb 4f5/2 for lead and lead oxide. EDS elemental mapping, XPS, and UV-vis spectroscopy analyses revealed the simultaneous presence of lead and lead oxide in the same structure. The band gap obtained for the shell was determined to be 4.50 eV. Consequently, Pb/Pb3O4 nanocomposites show a higher response to high-energy photons, making them suitable for UV photocatalysis applications.

Influence of Carboxymethyl Cellulose on the Green Synthesis of Gold Nanoparticles Using Gliricidia sepium and Petiveria alliacea Extracts: Surface-Enhanced Raman Scattering Effect Evaluation.

Gold nanoparticles (AuNPs) were synthesized and stabilized using ecological strategies: the extracts of the leaves of the plants Gliricidia sepium (GS) and Petiveria alliacea (PA) reduced the metallic Au ions to AuNPs. The AuNPs were analyzed as surface-enhanced Raman scattering (SERS) substrates for pyridoxine detection (vitamin B6). UV-vis spectroscopy was carried out to assess the stability of the AuNPs. As a result, absorption bands around 530 and 540 nm were obtained for AuNPs-PA and AuNPs-GS, respectively. Both cases associated it with localized surface plasmon resonance (LSPR). In the final stage of the synthesis, to stabilize the AuNPs, carboxymethyl cellulose (CMC) was added; however, LSPR bands do not exhibit bathochromic or hypsochromic shifts with the addition of CMC. Transmission electron microscopy (TEM) micrographs show relatively spherical morphologies; the particle diameters were detected around 7.7 and 12.7 nm for AuNPs-PA and AuNPs-GS, respectively. The nanomaterials were evaluated as SERS substrates on pyridoxine, revealing an intensification in the vibrational mode centered at 688 cm-1 associated with the pyridinic ring. Complementarily, different density functional theory functionals were included to obtain molecular descriptors on the Aun-cluster-pyridoxine interaction to study the SERS behavior.

Green Synthesis for Carbon Quantum Dots via Opuntia ficus-indica and Agave maximiliana: Surface-Enhanced Raman Scattering Sensing Applications.

In this study, we present an alternative method for synthesizing carbon quantum dots (CQDs) using a green synthesis approach via extracts from Agave maximiliana and Opuntia ficus-indica(Ofi). The extracts from both plants were used as the carbon source for the CQDs. The synthesis method employs mesoporous zeolite 4A as a refractory for the thermal treatment of the samples. Transmission electron microscopy analysis established that the size of the CQDs shows a narrow distribution centered around 2 nm with a maximum size of less than 3 nm for both cases. The CQDs exhibit absorption bands associated with π-π* transitions located around 220 nm. In both cases, photoluminescence (PL) phenomenon was detected by irradiating the samples with a UV wavelength and detecting emissions close to the blue wavelength. Additionally, both kinds of CQDs were tested as surface-enhanced Raman scattering (SERS) substrates against methylene blue (MB), indicating an enhancement associated with ring deformation and stretching modes of the v(C-C) and v(C-N) bonds located around 1400 and 1620 cm-1, respectively. Complementarily, in the framework of density functional theory, H2nC2(2m+1) structures (with n = 3-5 and m = 1-3) were used as a theoretical representation of CQDs in interaction with the MB molecule. It is used for developing the analysis of charge transfer effects between both systems and for specifying elements that generate the SERS effect associated with the chemical enhancement mechanism.