The present work shows the synthesis of ZnO nanoparticles through a green method, using sargassum extracts, which provide the reducing and stabilizing compounds. The conditions of the medium in which the reaction was carried out was evaluated, that is, magnetic stirring, ultrasound assisted, and resting condition. UV-Vis, FTIR spectroscopy, and X-ray diffraction results confirmed the synthesis of ZnO with nanometric crystal size. The scanning electron microscopy analysis showed that the morphology and size of the particles depends on the synthesis condition used. It obtained particles between 20 and 200 nm in the sample without agitation, while the samples with stirring and ultrasound were 80 nm and 100 nm, respectively. ZnO nanoparticles showed antibacterial activity against Gram-positive S. aureus and Gram-negative P. aeruginosa. A quantitative analysis was performed by varying the concentration of ZnO nanoparticles. In all cases, the antibacterial activity against Gram-positives was greater than against Gram-negatives. Ultrasound-assisted ZnO nanoparticles showed the highest activity, around 99% and 80% for S. aureus and P. aeruginosa, respectively. Similar results were obtained in the study of the anti-inflammatory activity of ZnO nanoparticles; the ultrasound-assisted sample exhibited the highest percentage (93%), even above that shown by diclofenac, which was used as a reference. Therefore, the ZnO nanoparticles synthesized with sargassum extracts have properties that can be used safely and efficiently in the field of biomedicine.

Bimetallic Au@Pt nanoparticles (NPs) with Pt monolayer shell are of much interest for applications in heterogeneous catalysts because of enhanced catalytic activity and very low Pt-utilization. However, precisely controlled synthesis with uniform Pt-monolayers and stability on the AuNPs seeds remain elusive. Herein, we report the controlled deposition of Pt-monolayer onto uniform AuNPs seeds to obtain Au@Pt core–shell NPs and their Pt-coverage dependent electrocatalytic activity for methanol electro-oxidation. The atomic ratio between Au/Pt was effectively tuned by varying the precursor solution ratio in the reaction solution. The morphology and atomic structure of the Au@Pt NPs were analyzed by high-resolution scanning transmission electron microcopy (HR-STEM) and X-ray diffraction (XRD) techniques. The results demonstrated that the Au@Pt core–shell NPs with Pt-shell thickness (atomic ratio 1:2) exhibit higher electrocatalytic activity for methanol electro-oxidation reaction, whereas higher and lower Pt ratios showed less overall catalytic performance. Such higher catalytic performance of Au@Pt NPs (1:2) can be attributed to the weakened CO binding on the Pt/monolayers surface. Our present synthesis strategy and optimization of the catalytic activity of Au@Pt core–shell NPs catalysts provide promising approach to rationally design highly active catalysts with less Pt-usage for high performance electrocatalysts for applications in fuel cells.

This work presents the results obtained in the design and manufacture of a simple, economic and ecological filter based on Sargassum spp. (Sspp), consisting of the species S. natans and S. fluitans, for the elimination of organic and inorganic toxic substances. The main objective is to make use of Sspp, as the massive amounts of this alga arriving at the Mexican Caribbean coast have caused serious problems over recent years. The toxic substances treated were organic dyes (methyl blue, methyl orange and methyl red) and the metal ion, lead (II). To obtain optimal removal conditions, grinding of the Sspp used, its mass and humidity were evaluated. In the design of the filter the area, flow rate and the number of layers were evaluated. Removal rates of almost 100%, 65% and 25% were obtained for methylene blue, methyl red and methyl orange respectively, and in the case of lead (II), values up to 95% were obtained. After the tests, the Sspp was characterized, using Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy, showing the presence of the dyes and the ionic species. These results demonstrate the efficiency of the dynamic Sspp-based filtration system proposed, which can be industrially scaled for the treatment of water contaminated with these kinds of substances.

Sargassum species-based extracts were used to carry out the synthesis of homogeneous gold nanoparticles. Various techniques were used to determine the characteristics and composition of the nanoparticles. The UV-Vis results showed that the 50% water/ethanol extract had the most reducing agents and stabilizers. Therefore, this type of extract was used to synthesize nanoparticles and for their subsequent characterization. Crystallinity and crystal size were evaluated using X-ray diffraction. Size and morphology were analyzed using scanning electron microscopy, showing that the gold nanoparticles were mostly spherical, with a size range of 15–30 nm. The catalytic activity of the gold nanoparticles was evaluated through the degradation of organic dyes: methylene blue, methyl orange, and methyl red. The degradation rates were different, depending on the nature of each dye, the simplest to degrade was methylene blue and methyl red was the most difficult to degrade. The results indicated that the use of Sargassum spp. for the synthesis of gold nanoparticles has potential in the remediation of water that is contaminated with organic dyes. Moreover, given the recent serious environmental and economic problems caused by the overpopulation of Sargassum spp. in the Mexican Caribbean, the findings hold promise for their practical and sustainable use in the synthesis of nanomaterials.

In this work, the influence of the Sargassum natans I alga extract on the morphological characteristics of synthesized ZnO nanostructures, with potential biological and environmental applications, was evaluated. For this purpose, different ZnO geometries were synthesized by the co-precipitation method, using Sargassum natans I alga extract as stabilizing agent. Four extract volumes (5, 10, 20, and 50 mL) were evaluated to obtain the different nanostructures. Moreover, a sample by chemical synthesis, without the addition of extract, was prepared. The characterization of the ZnO samples was carried out by UV-Vis spectroscopy, FT-IR spectroscopy, X-ray diffraction, and scanning electron microscopy. The results showed that the Sargassum alga extract has a fundamental role in the stabilization process of the ZnO nanoparticles. In addition, it was shown that the increase in the Sargassum alga extract leads to preferential growth and arrangement, obtaining well-defined shaped particles. ZnO nanostructures demonstrated significant anti-inflammatory response by the in vitro egg albumin protein denaturation for biological purposes. Additionally, quantitative antibacterial analysis (AA) showed that the ZnO nanostructures synthesized with 10 and 20 mL of extract demonstrated high AA against Gram (+) S. aureus and moderate AA behavior against Gram (-) P. aeruginosa, depending on the ZnO arrangement induced by the Sargassum natans I alga extract and the nanoparticles’ concentration (ca. 3200 µg/mL). Additionally, ZnO samples were evaluated as photocatalytic materials through the degradation of organic dyes. Complete degradation of both methyl violet and malachite green were achieved using the ZnO sample synthesized with 50 mL of extract. In all cases, the well-defined morphology of ZnO induced by the Sargassum natans I alga extract played a key role in the combined biological/environmental performance.