Currently, to reduce the environmental problems associated with plastic waste, methods are being sought to use this waste as raw materials in different applications, such as fibers. In addition, to improve these materials and provide different properties, nanoparticles (NPs) are incorporated. In the present work, polymeric fibers made of recycled polyethylene terephthalate (r-PET) from post-consumer water bottles, functionalized with 0%, 1.5%, 3% and 6% zinc oxide nanoparticles (ZnO-NPs) in function of r-PET weight, were elaborated to evaluate their antibacterial and antifungal characteristics. The ZnO-NPs were synthesized by the solvothermal method, obtaining particles with a mean diameter of 38.15 nm, while the fibers were obtained by electrospinning with a diameter range between 200–5000 nm. The functionalized fibers were carried out against Escherichia coli and Bacillus subtilis through the agar diffusion method, obtaining the highest inhibition halo at 6% w/w ZnO-NPs, being 26.5 mm and 34.25 mm, respectively. In addition, the same method was used to evaluate the antifungal activity of Penicillium s.p. and Fusarium graminearum, observing antifungal properties due to the presence of nanoparticles in the fibers.

Nanoparticles (NPs) have generated significant interest in various fields due to the unique properties that materials exhibit at the nanoscale. This study presents a comparative analysis of copper nanoparticles (Cu-NPs) and cobalt nanoparticles (Co-NPs) synthesized via conventional solvothermal and green hydrothermal synthesis using ethylene glycol and Medicago sativa extract, respectively. The conventional solvothermal synthesis showed higher efficiency for both Cu-NPs and Co-NPs with yields of 32.5% and 26.7%, respectively. Characterization through UV–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) revealed that while solvothermal synthesis produced larger particles (76.5 nm for Cu-NPs, 86.8 nm for Co-NPs), the green hydrothermal method yielded smaller particles (53.8 nm for Cu-NPs, 67.7 nm for Co-NPs) with better control over particle size distribution and spherical morphology, showing minimal agglomeration. UV–vis confirmed metal oxide formation, while FTIR showed complex patterns in NPs (green hydrothermal), indicating plant extract compounds. Antifungal evaluation against Pseudocercospora fijiensis showed complete inhibition at 2000 ppm for both NP types, with no mycelial growth after 30 days. When integrated into chitosan, solvothermal NPs produced rougher surfaces, and scanning electron microscope (SEM) confirmed the presence of copper and cobalt in the nanocomposites. This study provides insights into the synthesis of nanoparticles using an environmentally friendly process and their microbiological applications for future use in organic agriculture.

Magnetic nanoparticles of Fe3O4/TiO2 (core/shell) type were synthesized by a method combining chemical co-precipitation for the initial synthesis of Fe3O4 and sol-gel synthesis for the making of the TiO2 shell film. The magnetic nanoparticles were characterized before and after the coating process by X-ray, field emission scanning electron microscope and scanning electron microscope with X-ray microanalysis. The structural refinement analysis by the Rietveld method was performed through the FullProf program from X-ray powder diffraction, which confirmed the presence of Fe3O4 as iron oxide and the anastase phase of TiO2 as shell layer. The crystal size was calculated by Scherer’s equation and around 10nm for both the Fe3O4 core and TiO2 shell. According the field emission scanning electron microscope, the coated magnetic nanoparticles are spherical and they are highly agglomerated. The exclusive presence of Fe, Ti and O was confirmed by scanning electron microscope with X-ray microanalysis. Finally, the dispersion of aqueous Fe3O4/TiO2 nanoparticles was evaluated at different pH values by ultraviolet spectroscopy in the ultraviolet and visible range. The highest values of absorbance were obtained at pH 8 and 4,5; showing good dispersion. On the other hand, at pH 6,5 there is tendency to agglomerate with subsequent precipitation. Se sintetizaron nanopartículas magnéticas del tipo Fe3O4/TiO2 (núcleo/coraza) mediante el método combinado que involucra para la síntesis inicial del Fe3O4 la co-precipitación química y para la formación de la capa de TiO2 la síntesis por la técnica sol-gel. Las nanopartículas magnéticas fueron caracterizadas antes y después del proceso de recubrimiento, mediante rayos-X y microscopía electrónica de barrido con emisión de campo y con microanálisis de rayos-X. El análisis de refinamiento estructural se realizó por el método Rietveld a través del programa FullProf, a partir de la difracción de rayos-X de polvo y confirmó la presencia de Fe3O4 como óxido de hierro y que el recubrimiento está constituido por TiO2 en su fase anastasa. El tamaño del cristal fue calculado mediante la ecuación de Scherrer y corresponde alrededor de 10nm, tanto para el Fe3O4 como para la capa de TiO2. Según los análisis de microscopía electrónica de barrido con emisión de campo, las nanopartículas magnéticas recubiertas tienen forma esférica y se encuentran altamente aglomeradas. Los resultados de microscopía electrónica de barrido con microanálisis de rayos-X confirman únicamente la presencia de tres elementos: Fe, Ti y O. Finalmente, la dispersión de las nanopartículas de Fe3O4/TiO2 en agua fue evaluada a diferentes valores de pH mediante espectroscopía ultravioleta en el rango del ultravioleta y el visible. Los mayores valores de absorbancia se obtuvieron a pH 8 y 4,5; mostrando una buena dispersión. Por otro lado, a pH 6,5 hay tendencia a aglomerarse con posterior precipitación.