Synthesis, structure and magnetic properties of nanosized lanthanum-calcium manganite

U ovom radu predstavljeni su rezultati ispitivanja strukturnih, mikrostrukturnih i magnetnih osobina nanočestičnog mešovitog manganovog oksida sastava La0.7Ca0.3MnO3 dobijenog primenom dveju različitih metoda sinteze: mehanohemijske sinteze i modifikovane sinteze samorasprostirućim talasom sagorevanja (SHS). Karakterizacija sintetisanih uzoraka izvršena je pomoću rendgenske difrakcije, transmisione elektronske mikroskopije i SQUID magnetometrije. Rendgenostrukturna analiza pokazala je da su uzorci dobijeni na oba načina jednofazni i da kristališu u prostornoj grupi Pnma (ortorombična distorzija perovskitne strukture O′ tipa). Primenom mehanohemijske metode sinteze dobijen je sistem koji se odlikuje značajnim mikronaprezanjem, velikom magnetnom anizotropijom i postojanjem neuređenog površinskog sloja čija debljina iznosi ~ 30 % ukupnog dijametra čestice. Kao posledica aglomeracije čestica praha u uzorku su prisutne međučestične interakcije (dipol-dipol), što je potvrđeno opsežnim magnetnim merenjima. Ustanovljeno je da će, zavisno od eksperimentalnih uslova, sistem ispoljavati ili kolektivno spinsko ponašanje analogno stanju super-spinskog stakla (TP ≤ 46 K, H ≤ 500 Oe) ili superparamagnetno ponašanje. Velika pažnja posvećena je razvoju modifikovane sinteze SHS, sa ciljem da se obezbedi jednostepeni postupak za dobijanje nanočestičnih čvrstih rastvora visoke kristaliničnosti. Ovaj postupak je uspešno primenjen za dobijanje predmetnog oksida u nanočestičnoj formi. Nanočestice praha La0.7Ca0.3MnO3 sintetisanog modifikovanom SHS metodom odlikuju se visokim stepenom kristaliniteta bez prisustva amorfnog sloja na površini i relativno uzanom raspodelom čestica po veličini (12-35) nm. Na osnovu analize magnetnih merenja utvrđeno je da ovako dobijeni materijal istovremeno ispoljava osobine koje su karakteristične i za masivne i za nanočestične sisteme, što je rezultat spoja visokog stepena kristaliničnosti sa jedne, i male veličine čestica sa druge strane. Ponašanje magnetizacije u zavisnosti od temperature pruža jake indikacije za prisustvo međučestičnih interakcija i u ovom uzorku.This thesis presents the results of the investigation of structural, microstructural and magnetic properties of nanosized mixed manganite samples with composition La0.7Ca0.3MnO3, obtained by using two different methods of synthesis: mechanochemical synthesis and modified self-propagating high-temperature synthesis (SHS). The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and SQUID magnetometry. The structural analysis of XRD data showed that both samples are single phase and crystallize within O′ type of orthorhombic perovskite structure (space group Pnma). The sample obtained by mechanochemical treatment exhibits significant microstrain, high magnetic anisotropy and the existence of a disordered layer on the particle surface whose thickness amounts 30 % of a particle diameter. Due to particle agglomeration, a certain degree of interparticle interactions (dipolar) within the sample are present, which was confirmed by comprehensive set of magnetic measurements. It was found that, depending on the experimental conditions, the system will exhibit collective behavior which corresponds to super-spin glass state (TP ≤ 46 K, H ≤ 500 Oe) or superparamagnetic behavior. In order to provide a single-step process for the synthesis of nanoparticle solid solutions with high crystallinity, special attention was paid to development of appropriate modification of SHS synthesis. This procedure was successfully applied for obtaining the subject oxide in the nanoparticle form. Nanoparticles of La0.7Ca0.3MnO3 powder synthesized by a modified SHS method are found to be highly crystalline without the presence of an amorphous surface layer and to have relatively narrow particle size distribution (12-35) nm. The analysis of magnetic measurements showed that the so obtained material exhibits interesting mixture of bulk- and nanocharacteristics, originating from the combination of high crystallization degree and small particle size. Temperature dependence of magnetization indicates the presence of interparticle interactions in this sample

Radiation-Induced method for the controlled synthesis of nanostructured materials

The synthesis represents a crucial step for achieving the unique properties of nanomaterials. Gamma (γ) - radiation-induced synthesis possesses several advantages over other conventional synthetic routes such as production of clean materials, the possibility of simultaneous synthesis and sterilization, in-situ generation of radiolysis products and the lack of necessity for initiators and crosslinking reagents in the case of polymer-based materials fabrication. γ-radiation induced synthesis has been utilized in the development and modification of various types of systems, including metal, metal oxide and alloyed nanoparticles, carbon-based nanomaterials, polymer based nanomaterials and nanocomposites etc. In this lecture, fundamentals of radiation chemistry will be given with an emphasis on the synthesis of nanomaterials in aqueous solutions. The effects of the total dose, dose rate, and the addition of different solutes to tailoring the synthesized materials’ composition, form, shape, size and size distribution will be demonstrated. The possible applications of so obtained materials in industry and biomedicine will be presented

Nanofabrication and characterisation of magnetic Fe3O4 nanostructures for potential environmental and biomedical applications

Magnetic iron oxide nanomaterials, which enable a multitude of uses, are given special focus in the fields of biomedicine and environmental protection. The detection, sorption, and/or degradation of inorganic (lead, chromium, arsenic, and cadmium), organic (dyes, pharmaceuticals, pesticides, phenols, and benzene), and biological (viruses and bacteria) pollutants can all be effectively accomplished with the use of magnetic nanoparticles. Magnetic iron oxide nanomaterials are in particular focus for use as hyperthermia media in cancer treatment and as magnetic resonance imaging (MRI) contrast agents. The possibility of magnetic separation of such materials, due to their essential properties under the influence of an external magnetic field, reduces production costs and also prevents the production and accumulation of toxic waste. Among the many metal oxide nanomaterials, magnetite (Fe3O4) and maghemite (γ-Fe2O3) are currently the only two magnetic materials approved by the US Food and Drug Administration (FDA) for human use as iron deficiency therapeutics and as contrast agents for MRI. Here, we synthesized nanoparticles of magnetite (Fe3O4) by the method of reduction-precipitation and characterized. Additionally, potential binding of brilliant green dye on Fe3O4 and construction of innovative magnetic composite was investigated. The physicochemical features were explored using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). XRD analysis confirms formation of the crystal phase of magnetite. The presence of magnetite nanoparticles is shown by typical groups for the peaks of iron compounds at a lower wavelength (≤ 700 cm-1 ) that are characteristic of the Fe-O bond. Morphological analyzes with FESEM showed that magnetite is a composite of nanospheres and nanorods that provide a large surface area. Dye binding study was performed using UVvisible and FTIR spectrometer.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Removal of heavy metals from aqueous media by sunflower husk: A comparative study of biosorption efficiency by using ICP-OES and LIBS

Presented research aimed to develop an alternative approach for the estimation of biosorption capability of sunflower husk. The acid-pretreated sunflower biomass was characterized by scanning electron microscopy combined with energy dispersive X-Ray spectroscopy (SEM-EDX) analysis and Fourier transform infrared (FTIR) spectroscopy. Biosorption efficiency has been evaluated using inductively coupled plasma optical emission spectroscopy (ICP-OES) and laser-induced breakdown spectroscopy (LIBS). The adsorption capacity of the adsorbent was determined as the function of the pH of the solution, the initial concentration of heavy metal solutions, and contact time. The optimal conditions were achieved after 15 min of contact at pH 6, while the percentage of the removal was from 80.0–98.7 %, depending on the element. The results obtained from the kinetic and isotherm studies show that maximum adsorption of ions was quickly reached and followed the pseudo-second-order kinetic model. Real samples were tested and obtained Ni values by LIBS method were 3100±200 and 1240±100 mg kg-1, while estimated values by the ICP-OES were 2995±20 and 1130±10 mg kg-1, respectively. The obtained results prove that LIBS method can be used as a “green alternative” for the evaluation of biosorption efficiency

Spin Glass Dynamics of Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 Obtained by a Mechanochemical Milling

Spin dynamics of nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 system was studied through the set of diverse magnetic measurements Analysis of the data obtained from magnetic relaxation measurements, memory effect and AC susceptibility experiments pointed to a spin glass like behavior of interacting nanoparticle system14th Czech and Slovak Conference on Magnetism, Jun 06-09, 2010, Kosice, Slovaki

Spin glass like behaviour of magnetite nanoparticle system obtained by thermal decomposition of acetylacetonate precursor

The research aim was to investigate the magnetic properties of strongly interacting Fe3O4 nanoparticles. Monodisperse nanoparticles were prepared by thermal decomposition of iron (III) acetylacetonate. Transmission electron microscopy pointed to the narrow particle size distribution with the mean particle size of (4.87±1.10) nm. The magnetic properties were studied by means of SQUID magnetometer, with AC and DC measurements carried in the wide range of applied magnetic field, temperature and frequencies. Magnetic characterization proved superparamagnetic behaviour at high, as well as spin glass like (SGL) properties at low temperatures. The experimental fingerprints for SGL behaviour were found in the observed memory effects.Program and the book of abstracts available at: [https://dais.sanu.ac.rs/handle/123456789/175]Twelfth Young Researchers' Conference Materials Sciences and Engineering December 11-13, 2013, Belgrade, Serbi

Development of Novel Approaches for Tumour Therapy based on Nanostructured Materials - MagBioVin Project

Research advancements and opportunities by the FP7-ERA Chairs project MagBioVin are spotlighted.[1] Topic of the project is the design of different novel magnetic nanoarchitectures (e.g. bimagnetic and polymeric core-shell systems, nanoparticles embedded in mesoporous silica structures, and radiolabeled nanostructures)[2–4] for application in targeted treatment and diagnostics of cancer. These nanomaterials posses the ability for selective treatment of tumor tissues by the targeting with magnetic field.[5,6] Alternating magnetic field also provides the means for hyperthermia-induced cancer treatment.[7]Attachment of radionuclides to the synthesized nanoparticles is explored for the purpose of imaging and internal radiotherapy.[8,9] Magnetic characteristics of the prepared nanomaterials is done by SQUID magnetometry and Mössbauer spectroscopy. Structural characterization of the investigated nanomaterials is performed by XRD, TEM imaging, DRIFT spectroscopy, and nitrogen sorption analysis. Magnetic hyperthermia effects are monitored by using commercial setup (nB nanoScale Biomagnetics) which includes applicators for cell cultures and small animals. In vitro and in vivo (animal model) applicability of the synthesized nanomaterials regarding toxicity, biodistribution and anticancer efficacy is explored for targeted cancer treatment.1st International Symposium: program and the book of abstracts : March 29-31, 2016; University of Central Lancashire, Preston, U

Solvothermal synthesis of magnetite nanoparticles suitable for application in magnetic hyperthermia

In this paper, spherical Fe3O4@OA nanoparticles were prepared via solvothermal method, in which iron sulphate, sodium hydroxide and oleic acid were used as precursors. The main idea of this research was to develop the method for preparation of nanoparticles with magnetic properties suitable for application in magnetic hyperthermia. We have tried to tailor size, shape and the degree of interparticle interactions by varying experimental conditions during the synthesis route. Obtained samples were structurally and magnetically characterized by means of different experimental probes such as: X-ray diffraction, SQUID magnetometry, FTIR and Mossbauer spectroscopy. Structural characterization asserts that the obtained phase is magnetite, Fe3O4, while FTIR spectra support the presence of oleic acid coating on the particle surface. Detailed magnetic characterization done by SQUID measurements and Mossbauer spectroscopy confirmed the presence of the strong and weak interactions in the nanoparticles system, depending on the synthesis conditions.11th Conference for Young Scientists in Ceramics (SM-2015, and ESR Workshop, COST MP1208) : programme and the book of abstracts, October 21-24, Novi Sa

Relaxation phenomena in SSG Fe3O4 nanoparticle system

Fe3O4 nanoparticles were synthesized by thermal decomposition of organic precursor (acac complex) and the structural characterization was done by TEM measurements. In order to understand magnetic behavior of the examined Fe3O4 system magnetic characterization was done by SQIUD measurements in AC and DC regime. Sample exerts memory effects and aging phenomena, all pointing to the existence of super spin glass state at low temperatures. Appropriate interpretation of the measured effects can be provided within the framework of droplet and hierarchical models. Investigation of relaxation phenomena comprised measurements of zero field cooled and thermoremanent magnetization time decay. Time dependence of the related relaxation rates showed unusual trend of slowing down with increasing temperature. The origin of observed behavior still remains an open question

Magnetism of Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 under Applied Hydrostatic Pressure

Nanoparticle La0 7Ca0 3Mn0 7Fe0 3O3 with the average particle size of 10 nm was mechanochemically synthesized in the single-step procedure Temperature and field dependences of magnetization were recorded under both ambient and applied hydrostatic pressure up to 0 47 GPa At ambient pressure, two magnetic transition points were observed one of the spin-glass like type at the temperature T-f approximate to 34 K, and ferro-to-paramagnet transition at T-C approximate to 51 K Under the applied pressure magnetic parameters gradually changed (i) both T-C and T-f were lowered with the increase in pressure, (ii) both high field magnetization M-5T and remanent magnetization M-Rem decreased with pressure, (iii) coercivity H increased with pressure The obtained results show that magnetism of a nanoparticle system with high degree of Intrinsic disorder diminishes with the applied pressure that is in compliance with the effect of the increased cationic disorder (internal pressure) in bulk manganites14th Czech and Slovak Conference on Magnetism, Jun 06-09, 2010, Kosice, Slovaki