Rentería Beleño, Boris

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    Preparation and characterization of polyaniline-based magnetic nanocomposites for EMI shielding applications
    (2007) Rentería Beleño, Boris; Banerjee, Jayanta; College of Engineering; Valentín Rullán, Ricky; Perales Pérez, Oscar J.; Department of Mechanical Engineering; Calderón Colón, Andrés
    Among the wide applications of polymers, their use to reduce electronic noise is receiving great attention from the scientific and technological communities. This electronic noise is part of electromagnetic interference (EMI), which is responsible for the degradation of electronic systems or their interference with other electronics devices. The uncontrolled exposure to electromagnetic waves caused by the problems mentioned before can also be conducive to health concerns. Polyaniline (PAni) characteristics of frequency agility, light weight, simple tuning of functional properties and its non-corrosive nature, make this polymer a suitable material for the development of electromagnetic shielding materials where protection against noise without degradation of device performance is the main aim. Tuning of conductive and magnetic properties in PAni-based nanocomposites can be achieved by suitable selection of polymerization conditions and controlled addition of ferrites nanoparticles. PAni was synthesized by polymerization of aniline in presence of ammonium peroxydisulfate and HCl. The disperse phase consisted of low-coercivity (Zn-Mn ferrites) nanoparticles. Our work was focused on the synthesis of PAni matrix and the ferrite disperse nano-phase as well as the determination of suitable conditions for homogeneous dispersion of the nanoparticles during the polymerization process in order to achieve suitable homogeneity of the magnetic properties in the final composites. The results of magnetic characterization by Vibrating Sample Magnetometer (VSM) magnetometers, and structural and morphological characterization by X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscopy (HRTEM) techniques respectively, are presented and discussed. The effect of the presence of ferrite nanocrystals on the thermal stability of the nanocomposites has been evaluated by Thermogravimetric analyses (TGA) of the composites produced at different PAni/ferrite molar ratios. The conductivity of synthesized PAni-based nanocomposites has also been calculated from Current Vs Voltage (I Vs V) measurements carried out at room temperature conditions.
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    Processing of biopolymer-based magnetic nanocomposites and their evaluation for disinfection in water reuse applications
    (2024-12-16) Rentería Beleño, Boris; Suárez, O. Marcelo; College of Engineering; Tarafa Vélez, Pedro J.; Silva Araya, Walter F.; Román Velázquez, Félix R.; Department of Civil Engineering; Santiago Román, Aidsa I.
    This dissertation explores using nanostructured materials for environmental remediation, focusing on water contamination - a pressing global issue that poses severe health risks and exacerbates the water scarcity crisis. The research develops innovative methods for contaminant removal using ferrite nanoparticles integrated with biopolymers. The study emphasizes pathogenic water contamination linked to health problems such as gastrointestinal infections, neurological disorders, and heightened cancer risks, underscoring the urgency of advancing water treatment technologies. Ferrite nanoparticles, particularly cobalt ferrites, exhibit unique properties such as superparamagnetic behavior, high surface area, and a positive surface charge, making them highly effective for antibacterial applications. These nanoparticles interact electrostatically with the negatively charged bacterial membranes, facilitating the magnetic capture and removal of microorganisms. Incorporating biopolymers enhances the nanoparticles' structural support, biocompatibility, and environmental safety, enabling the synthesis of advanced nanocomposites. Cobalt ferrite nanoparticles were synthesized via a controlled co-precipitation method, evaluating physical, morphological, and antibacterial properties by varying synthesis parameters such as temperature, time, and heating method (Bunsen burner, autoclave, and microwave). Characterization techniques, including XRD, VSM, optical microscopy, SEM, TEM, zeta potential analysis, and FT-IR, confirmed the synthesized materials' structural, magnetic, and functional group properties, validating their suitability for water remediation. Microbiological tests showcased significant microbial reductions, even against Gram-positive and Gram-negative bacteria, highlighting the adaptability and effectiveness of the materials across diverse microbiological contaminants. The nanoparticles exhibited a spinel structure characteristic of ferrites, irrespective of the heating method. Among 36 samples evaluated, the material synthesized using a Bunsen burner at 900°C for 5 minutes demonstrated optimal properties, including a 12 nm average particle size, 41 emu/g magnetization, and 9 mV zeta potential at pH 7, with an irregular morphology. The electrospinning and cross-linking formation processes ensured uniform nanoparticle dispersion in the polymer solutions that synthesize fibers and beads. Characterization techniques, including XRD, FT-IR, SEM, and TEM, were employed to verify the particles' size, morphology, crystalline structure, and functional groups. Antibacterial and magnetic removal tests were conducted, exposing the nanomaterials to different bacterial concentrations of E. coli and E. faecalis, which were selected as representatives of Gram-positive and Gram-negative bacteria, respectively. Bacterial growth inhibition studies revealed a 70% removal efficiency for E. coli and approximately 20% for E. faecalis at a concentration of 1×10 CFU/mL when exposed to 2500 ppm of nanoparticles. Further enhancements were accomplished by incorporating cobalt ferrite nanoparticles into beads and electrospun fibers, the former based on sodium alginate and the latter on cellulose acetate. The 3X-beads sample with 60 w/w% nanoparticle content achieved 70% and 40% removal efficiencies for E. coli and E. faecalis, respectively. In contrast, cellulose acetate fibers demonstrate magnetic removal efficiencies ranging from 20% to 60% for both bacterial types at concentrations of 1,000 mg of magnetic fiber S1-10-40 with 40 w/w% of nanoparticles. General results showed that the synthesized nanomaterials, including biopolymer-based beads and fibers, effectively reduced microbial contamination through magnetic removal. The methodology proved versatile across diverse microorganism types, highlighting its potential to combat antibiotic-resistant bacteria. This research contributes to developing sustainable materials for environmental remediation, offering scalable solutions to enhance water quality and address the integrated challenges of water scarcity and microbial pollution.