Synthesis, structural characterization and broadband ferromagnetic resonance in Li ferrite nanoparticles

Producción CientíficaLithium ferrites are well known materials due to its numerous technological applications especially in microwave devices. Lithium ferrite nanoparticles were prepared by sol-gel technique by means of Pechini method, and then annealed at different temperatures in 250–1000 °C range. XRD confirms spinel formation with particles sizes in 15–700 nm range, with increased size with annealing temperature, whereas FTIR and Raman measurement confirm that single phase lithium ferrite with ordered cationic structure is obtained. Microwave magnetoabsorption data of the annealed lithium ferrite nanoparticles were obtained with a broadband system based on a network analyzer that operates up to 8.5 GHz. At fields up to 200 mT we can observe a broad absorption peak that shifts to higher frequencies with magnetic field according to ferromagnetic resonance theory. The amplitude of absorption, up to 85%, together with the frequency width of about 5.5 GHz makes this material suitable as wave absorber. FMR parameters like resonance field, linewidth and broadening are analyzed in order to obtain the characteristic parameters and analyze the microwave behaviour.Ministerio de Economía, Industria y Competitividad ( project MAT2016-80784-P

Broadband ferromagnetic resonance in Mn-doped Li ferrite nanoparticles

Producción CientíficaLithium ferrites are well known materials due to their numerous technological applications especially in microwave devices. Mn-doped lithium ferrite nanoparticles were prepared by sol-gel technique by means of Pechini method, and then annealed at different temperatures in 250–1000 °C range. XRD confirms spinel formation with particle size in the 15–200 nm range, with increased size with annealing temperature. Microwave magnetoabsorption data of annealed lithium ferrite nanoparticles, obtained with a broadband system based on a network analyzer operating up to 8.5 GHz are presented. At fields up to 200 m T we can observe a broad absorption peak that shifts to higher frequencies with magnetic field according to ferromagnetic resonance theory. The amplitude of absorption, up to 85%, together with the frequency width of about 4.5 GHz makes this material suitable as wave absorber. Samples annealed at higher temperatures show a behaviour similar to polycrystalline samples, thus suggesting their multidomain character.Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación with FEDER (project MAT2016-80784-P

Implantação de sistemas operativos em módulos de comunicação sem fios

Mestrado em Engenharia Eletrónica e TelecomunicaçõesA crescente adoção de redes de sensores sem fios na indústria tem potenciado esforços contínuos de investigação e desenvolvimento ao nível dos sistemas operativos que as suportam. A uniformização da programação para diferentes plataformas de hardware e a reutilização de pilhas de comunicação permite obter ganhos significativos no processo de desenvolvimento. A Micro I/O possui uma plataforma de hardware designada por μMRF que tem sido usada em várias aplicações de redes de sensores sem fios para validação de conceito e para prototipagem. Com vista a suportar aplicações com requisitos de comunicação mais exigentes e empregar um método de desenvolvimento mais eficiente, optou-se por adaptar o sistema operativo Contiki para a plataforma μMRF. Esta dissertação descreve o trabalho realizado para integrar o suporte do microcontrolador Microchip™ dsPIC33FJ256MC710 no sistema operativo Contiki. A validação deste trabalho foi realizada através de uma aplicação desenvolvida com a versão modificada do sistema operativo Contiki e com o sensor de temperatura existente na placa μMRF. Esta aplicação permite o acesso remoto à temperatura do sensor, através de um browser, usando o protocolo HTTP e a verificação de conectividade usando pacotes ICMP, ambos sobre Ipv6. O desempenho da rede sem fios foi avaliado nas vertentes de perda de pacotes e de round trip delay usando pacotes echo request e echo reply. O trabalho realizado insere-se num projecto para desenvolvimento de sistemas de “smart-parking” no qual as restrições de energia são significativas mas onde a possibilidade de aplicações, suportadas em sistemas operativos, é aliciante.Over the last few years, there has been a significant increase in the use of wireless sensor networks in industry. This has pushed the research and development in embedded operating systems to support applications in this domain. In fact, the possibility to turn applications independent of the hardware platforms and the possibility to reuse communications stacks leads to significant gains in the applications development process. Micro I / O has developed a hardware platform called μMRF that has been used to build several applications with wireless sensor networks for proof of concept and prototyping. In order to support applications with more demanding communication requirements, and to improve the development process, it was decided to adapt the Contiki operating system to the platform μMRF. This dissertation describes the work done to adapt the Contiki operating system to support the Microchip ™ dsPIC33FJ256MC710 microprocessor. The validation of this work was conducted through an application developed with the modified version of the Contiki operating system using the temperature sensor onboard of the μMRF platform for demonstration purposes. The developed application allowed remote access to the temperature sensor through a browser using the HTTP protocol and the connectivity verification, using ICMP packets, both through IPv6. The performance of the wireless network was evaluated through an analysis of the packet loss and round trip delays using echo request and echo reply. This work is aimed to evaluate the possibility to support smart parking applications in embedded systems connected by wireless communications, with severe restrictions in power consumption but with a significant interest in having an embedded operating system with all the correspondent functionalities

Magnetic After-effects in Ni Ferrite Nanoparticles

Producción CientíficaMagnetic after-effects in ferrite nanoparticles have been measured with magnetic disaccommodation technique. For higher annealing temperature multidomain formation is detected with low temperature relaxation process similar to single crystal and polycrystalline NiFe2O4. As expected, no room temperature processes are observed due to low vacancy content. On the other hand, logarithmic relaxations are observed at lower annealing temperatures, revealing monodomain character.Ministerio de Economía, Industria y Competitividad (project MAT2016-80784-P

Fabrication, Structural, Electrical, and Biological Analysis

This research was funded by FEDER funds through the COMPETE 2020 Program and National Funds through the FCT—Portuguese Foundation for Science and Technology under the projects LISBOA-01-0247-FEDER-039985/POCI-01-0247-FEDER-039985. S.R. Gavinho and A. Sofia Pádua acknowledge the FCT—Portuguese Foundation for Science and Technology for the Ph.D. grant ( UI/DB/151287/2021). Publisher Copyright: © 2023 by the authors.Implantology is crucial for restoring aesthetics and masticatory function in oral rehabilitation. Despite its advantages, certain issues, such as bacterial infection, may still arise that hinder osseointegration and result in implant rejection. This work aims to address these challenges by developing a biomaterial for dental implant coating based on 45S5 Bioglass® modified by zirconium insertion. The structural characterization of the glasses, by XRD, showed that the introduction of zirconium in the Bioglass network at a concentration higher than 2 mol% promotes phase separation, with crystal phase formation. Impedance spectroscopy was used, in the frequency range of 102–106 Hz and the temperature range of 200–400 K, to investigate the electrical properties of these Bioglasses, due to their ability to store electrical charges and therefore enhance the osseointegration capacity. The electrical study showed that the presence of crystal phases, in the glass ceramic with 8 mol% of zirconium, led to a significant increase in conductivity. In terms of biological properties, the Bioglasses exhibited an antibacterial effect against Gram-positive and Gram-negative bacteria and did not show cytotoxicity for the Saos-2 cell line at extract concentrations up to 25 mg/mL. Furthermore, the results of the bioactivity test revealed that within 24 h, a CaP-rich layer began to form on the surface of all the samples. According to our results, the incorporation of 2 mol% of ZrO2 into the Bioglass significantly improves its potential as a coating material for dental implants, enhancing both its antibacterial and osteointegration properties.publishersversionpublishe

Application of hyperthermia for cancer treatment: Synthesis and characterization of magnetic nanoparticles and their internalization on tumor cell lines

FEDER funds through the COMPETE 2020 Program under the project number POCI-01-0145-FEDER-007688. This work was also funded by the Scientific merit prize Santander-Totta - Lisbon New University - "Antibody engineering for breast cancer therapy" 2013. Catarina I. P. Chaparro also acknowledges the financial support from Liga Portuguesa Contra o Cancro (LPCC)/Pfizer 2017.Truncated sialylated O-glycans, such as cell-surface carbohydrate antigen sialyl-Tn (STn) are overexpressed by several cancer types, but not by the respective normal tissues. STn expression is associated with oncogenesis and metastatic ability of cancer cells, with reduced overall survival and lack of response to chemotherapy. Advances in nanomedicine have resulted in rapid development of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) with considerable potential in cancer treatment. Therefore, in this study SPIONs coated with oleic acid (OA) or dimercaptosuccinic acid (DMSA) were developed and characterized for internalization in two breast cancer cell lines: cell line expressing the STn antigen and the corresponding control. SPIONs with an average diameter of 8 nm showed superparamagnetic behavior and high potential to be used as magnetic hyperthermia agents. OA and DMSA coating provided high stability of SPIONs in physiological conditions while not changing their main properties. NPs internalization studies showed a higher accumulation of DMSA coated NPs in the breast cancer MDA-MB-231 WT cell line. In MDA-MB-231 cell line expressing STn both coated NPs showed a similar accumulation. Therefore, STn antigen can act as a receptor capable of detecting and covalently bind to the molecules present on NPs surface and induce their cellular uptake by endocytosis.publishersversionpublishe

Electrospun composite cellulose acetate/iron oxide nanoparticles non-woven membranes for magnetic hyperthermia applications

In the present work composite membranes were produced by combining magnetic nanoparticles (NPs) with cellulose acetate (CA) membranes for magnetic hyperthermia applications. The non-woven CA membranes were produced by electrospinning technique, and magnetic NPs were incorporated by adsorption at fibers surface or by addition to the electrospinning solution. Therefore, different designs of composite membranes were obtained. Superparamagnetic NPs synthesized by chemical precipitation were stabilized either with oleic acid (OA) or dimercaptosuccinic acid (DMSA) to obtain stable suspensions at physiological pH. The incorporation of magnetic NP into CA matrix was confirmed by scanning and transmission electron microscopy. The results showed that adsorption of magnetic NPs at fibers' surface originates composite membranes with higher heating ability than those produced by incorporation of magnetic NPs inside the fibers. However, adsorption of magnetic NPs at fibers' surface can cause cytotoxicity depending on the NPs concentration. Tensile tests demonstrated a reinforcement effect caused by the incorporation of magnetic NPs in the non-woven membrane.publishe

Effect of tetramethylammonium hydroxide on nucleation, surfacemodification and growth ofmagnetic nanoparticles.

Nanoparticles of magnetite (Fe3O4) were obtained by reacting ferric chloride with sodium sulphite, through the reductionprecipitation method. The effects of adding tetramethylammonium hydroxide (TMAOH) during or after the precipitation of the iron oxide were studied in an attempt to obtain well-dispersed magnetite nanoparticles. Accordingly, the following experimental conditions were tested: (i) precipitation in absence of TMAOH (sample Mt), (ii) the same as (i) after peptizing with TMAOH (Mt1), (iii) TMAOH added to the reaction mixture during the precipitation of magnetite (Mt2). Analyses with transmission electron microscopy (TEM), X-ray diffraction, M?ossbauer spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), zeta potential, and magnetization measurements up to 2.5 T revealed that magnetite was normally formed also in the medium containing TMAOH. The degree of particles agglomeration was monitored with laser diffraction and technique and inspection of TEM images. The relative contributions of N?eel and Brownian relaxations on the magnetic heat dissipation were studied by investigating the ability of suspensions of these magnetite nanoparticles to release heat in aqueous and in hydrogel media. Based on ATR-FTIR and zeta potential data, it is suggested that the surfaces of the synthesized magnetite particles treated with TMAOH become coated with (CH3)4N+ cations