pedro lana | CDTN - Academia.edu (original) (raw)

Papers by pedro lana

Manganese copper ferrites belong to a family of ferrites with specific importance due to their hi... more Manganese copper ferrites belong to a family of ferrites with specific importance due to their high permeability values and low losses at low frequencies. In this paper, a series of ferrite samples has been synthesized using a novel and low cost sol-gel autocombustion route in order to systematically investigate the structural, compositional, morphological, and magnetic properties when zinc is substituted by copper in the series. X-ray diffraction reveals that all the samples have characteristic cubic spinel structure. The effect of zinc substitution at the copper site on the chemical bonding of the ferrite samples was investigated by Fourier transform infrared spectroscopy. Energy dispersive X-ray analysis was performed to determine the homogeneity and stoichiometric composition of elements present in the samples. Nanosized, uniformly shaped grains were evident from the images obtained using a scanning electron microscopy, which indirectly confirms the significance of the autocombustion synthesis technique employed in this paper. Magnetic properties determined using a vibrating sample magnetometer exhibited that zinc substitution could enhance the saturation magnetization of the samples, attributed to the substitution of a paramagnetic element (zinc) by a diamagnetic one (copper).

Química Nova, 2023

Recebido em 20/06/2022; aceito em 30/09/2022; publicado na web em 09/12/2022 Resistant infectious... more Recebido em 20/06/2022; aceito em 30/09/2022; publicado na web em 09/12/2022 Resistant infectious microorganisms are causing a worldwide emerging problem, called antimicrobial resistance. To avoid this outbreak, new antimicrobial technologies are necessary. Silver nanoparticles (AgNPs) are known for their antibacterial properties and several studies have focused on their synthesis, characterization, and biological assays. One possibility to synthesize AgNPs is through gamma radiation, known as radiolytic synthesis. This work focuses on the radiolytic synthesis of AgNPs capped into a mesoporous silica nanoparticle aiming at an antimicrobial application. The variants of the radiolytic synthesis, which may influence the AgNPs formation, were studied and statistically compared by Design of Experiments Factorial Design in Minitab Software. The Ag content is statically dependent on dose, volume, and pH, as well as on two parameters interaction: [Ag+]-pH and [Ag+]-volume-pH interaction. Transmission electron microscopy and nitrogen adsorption analyses indicated the presence of subnanometric AgNPS located inside the mesopores. Silver nanoagglomerates were also found by transmission electron microscopy, which could be formed by silver oxides, as shown in X-ray photoelectron spectroscopy. AgNPs reduce the specific surface area of the silica nanoparticle, while the matrix morphology remains. The nanocomposites presented preliminary biocompatibility observed in in vitro biological assay using fibroblasts, which support their application in biological systems as antimicrobial substitutes.

Environmental Technology, Jan 11, 2023

Physical Review B, Jul 25, 2005

We present magneto-optic Kerr effect, x-ray photoelectron spectroscopy, and x-ray magnetic circul... more We present magneto-optic Kerr effect, x-ray photoelectron spectroscopy, and x-ray magnetic circular dichroism data from epitaxial thin ferromagnetic film grown onto GaAs͑001͒-͑4 ϫ 6͒. By seeding a half monolayer of Co in an Fe double wedge with a total thickness of six monolayers, we introduced a magnetic marker, which, similarly to Mössbauer spectroscopy, allows us to probe the magnetic and chemical properties across the ferromagnetic film in a layer-dependent analysis. The long-range magnetization is found to persist within the Fe overlayer at any depth, until a reduction is observed at the interface with GaAs. Correspondingly the spin magnetic moment is maximum at the center of the film and is reduced both at the interface and at the surface. We found also an enhancement of the orbital magnetic moment and orbit-to-spin magnetic-moment ratio near the interface with the GaAs substrate. Further, an uneven segregation ͑diffusion͒ between Ga and As has been found, and its influence on magnetic properties is discussed.

Social Science Research Network, 2022

RSC Advances, 2017

We theoretically and experimentally investigated wasp-waisted magnetic hysteresis curves at a low... more We theoretically and experimentally investigated wasp-waisted magnetic hysteresis curves at a low temperature for CoFe 2 O 4 nanopowders. Our theoretical approach proposes a physical mechanism that leads to wasp-waisted behavior for a single magnetic phase with the same anisotropic field, contrary to that of typical multi-phase magnetic systems. Our simulations show that a combination of effects, namely easy-plane anisotropy configuration and dipolar interactions, results in a double peak in the magnetic susceptibility curve of a granular magnetic system. As experimental evidence of such an effect, we present a CoFe 2 O 4 nanopowder and its structural and magnetic characterizations, which support a single magnetic phase. In addition, the evidence does not corroborate many explanations reported in the literature for wasp-waisted magnetic behavior. Our results provide evidence for a tetragonal crystalline phase of CoFe 2 O 4 due to magneto-elastic coupling, recently reported in the literature.

ACS applied nano materials, May 2, 2023

World Journal of Microbiology & Biotechnology, Jan 6, 2022

Selenium nanoparticles (SeNPs) were synthesized by irradiating a solution containing sodium selen... more Selenium nanoparticles (SeNPs) were synthesized by irradiating a solution containing sodium selenite (Se +4) as the precursor in YPG liquid medium with gamma-rays. Spherical particles were formed after reactions of sodium selenite with hydrated electrons (e aq-) and hydrogen radicals (H •) produced following water radiolysis. No hazardous reducing agents were employed. The obtained nanoparticles were morphologically characterized, and their physicochemical and structural parameters were analyzed. SeNPs characterization showed all selenium in the Se 0 state. We incubated Saccharomyces cerevisiae cells with the SeNPs for 24 h and then challenged the cells with ionizing radiation. After radiation exposure, cells were assessed for cell viability, lipid peroxidation, protein carbonylation, free radical generation, and total sulfhydryl content. The synthesized SeNPs were considered safe and less toxic at the concentration employed than the same selenite concentration. Except for the protein carbonylation results, there were no other signi cant modi cations in viability or the oxidative stress parameters in SeNP-treated cells. It was concluded that 1 mM of the synthesized SeNPs does not trigger oxidative stress. Furthermore, we veri ed that SeNPs attenuate the reactive oxygen species generation after in vitro ionizing radiation exposure. These observations open up tremendous possibilities for radiosensitizer development. Highlights Synthesis of selenium nanoparticles with gamma irradiation and sodium selenite Generation of spherical, amorphous, and zero-valent selenium nanoparticles In vitro nanoparticle treatment reduces reactive oxygen species after irradiation Selenium nanoparticles are safe, nontoxic, not provoking oxidative stress in vitro Selenium nanoparticles as possible platform for radiosensitizers development

Ceramics International, Jun 1, 2023

Journal of Controlled Release

Vectorized small interfering RNAs (siRNAs) are widely used to induce gene silencing. Among the de... more Vectorized small interfering RNAs (siRNAs) are widely used to induce gene silencing. Among the delivery systems used, lipid-based particles are the most effective. Our objective was the development of novel lipid-polymer hybrid nanoparticles, from lipoplexes (complexes of cationic lipid and siRNAs), and poly (lactic-co-glycolic acid) (PLGA), using a simple modified nanoprecipitation method. Due to their morphology, we called these hybrid nanoparticles Spheroplexes. We elucidated their structure using several physico-chemical techniques and showed that they are composed of a hydrophobic PLGA matrix, surrounded by a lipid envelope adopting a lamellar structure, in which the siRNA is complexed, and they retain surface characteristics identical to the starting nanoparticles, i.e. lipoplexes siRNA. We analyzed the composition of the particle population and determined the final percentage of spheroplexes within this population, 80 to 85% depending on the preparation conditions, using fluorescent markers and the ability of flow cytometry to detect nanometric particles (approximately 200 nm). Finally, we showed that spheroplexes are very stable particles and more efficient than siRNA lipoplexes for the delivery of siRNA to cultured cells. We administered spheroplexes contain siRNAs targeting TNF-α to mice with ulcerative colitis induced by dextran sulfate and our results indicate a disease regression effect with a response probably mediated by their uptake by macrophages / monocytes at the level of lamina propria of the colon. The efficacy of decreased level of TNF-α in vivo seemed to be an association of spheroplexes polymer-lipid composition and the specific siRNA. These results demonstrate that spheroplexes are a promising hybrid nanoparticle for the oral delivery of siRNA to the colon.

ACS Applied Nano Materials

$Research paper thumbnail of Caracterizacao de titanato de bario, obtido pelo processo hidrotermal, atraves da difracao de raio X$

Ceramica (Sao Paulo), 1996

Materials Chemistry and Physics

Nanomaterials, 2021

The detailed study of graphene oxide (GO) synthesis by changing the graphite/oxidizing reagents m... more The detailed study of graphene oxide (GO) synthesis by changing the graphite/oxidizing reagents mass ratios (mG/mROxi), provided GO nanosheets production with good yield, structural quality, and process savings. Three initial samples containing different amounts of graphite (3.0 g, 4.5 g, and 6.0 g) were produced using a bench reactor under strictly controlled conditions to guarantee the process reproducibility. The produced samples were analyzed by Raman spectroscopy, atomic force microscopy (AFM), x-ray diffraction (XDR), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetry (TGA) techniques. The results showed that the major GO product comprised of nanosheets containing between 1–5 layers, with lateral size up to 1.8 µm. Therefore, it was possible to produce different batches of graphene oxide with desirable physicochemical characteristics, keeping the amount of oxidizing reagent unchanged. The use of different proportions (mG...

Physical Chemistry Chemical Physics, 2020

In this work, we present a coupled experimental and theoretical first-principles investigation on... more In this work, we present a coupled experimental and theoretical first-principles investigation on one of the more promising oxide-diluted magnetic semiconductors, the Sn1−xCoxO2 nanoparticle system, in order to see the effect of cobalt doping on the physical and chemical properties.