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Removal of neodymium ions from aqueous solution by magnetic nanoparticles
Ana Ambrož, 2021, master's thesis

Abstract: This work is focused on the synthesis and characterization of surface-functionalized γ-Fe2O3-NH4OH@SiO2(APTMS) nanoparticles, their applications, and performance for Nd3+ removal from aqueous solutions, with an emphasis on the characterization of MNPs and Nd(NO3)3•6H2O. The γ-Fe2O3 nanoparticles were obtained by the co-precipitation method, stabilized with ammonia solution, and functionalized by SiO2 and APTMS. Neodymium nitrate hexahydrate (Nd(NO3)3•6H2O) used in aqueous solution was synthesised from neodymium oxide (Nd2O3) powder. The thermal behaviour and stability of the magnetic nanoparticles and Nd(NO3)3•6H2O was studied with thermogravimetric analysis (TGA) in O2, N2, and air atmosphere. Transmission electron microscopy (TEM) images were obtained in order to analyse the particle morphology and measure the size distribution of the nanoparticles. The hydrodynamic diameter of particles and the zeta potential were measured to determine the stability of particles in the solution. ATR-FTIR spectroscopy was used to confirm the functionalization of the magnetic nanoparticles and the adsorption of Nd3+ ions. The effect of the REE adsorption on the MNPs was studied by comparing the sample’s UV-Vis absorption spectra. The laboratory testing and analysis of the results indicate promising applications for the removal of the REE from aqueous solutions with magnetic nanoparticles. However, the coating of the MNP core by SiO2(APTMS) is inefficient for the removal of Nd3+ ions.
Keywords: Magnetic nanoparticles, Rare earth elements, Neodymium, Adsorption, Zeta potential, UV-Vis spectroscopy
Published: 03.05.2021; Views: 102; Downloads: 22
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The magnetic and colloidal properties of $CoFe_2O_4$ nanoparticles synthesized by co-precipitation
Sašo Gyergyek, Mihael Drofenik, Darko Makovec, 2014, original scientific article

Abstract: Magnetic $CoFe_2O_4$ nanoparticles were synthesized by co-precipitation at 80 °C. This co-precipitation was achieved by the rapid addition of a strong base to an aqueous solution of cations. The investigation of the samples that were quenched at different times after the addition of the base, using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS) and X-ray powder diffractometry, revealed the formation of a Co-deficient amorphous phase and $Co(OH)_2$, which rapidly reacted to form small $CoFe_2O_4$ nanoparticles. The nanoparticles grew with the time of aging at elevated temperature. The colloidal suspensions of the nanoparticles were prepared in both an aqueous medium and in a non-polar organic medium, with the adsorption of citric acid and ricinoleic acid on the nanoparticles, respectively. The measurements of the room-temperature magnetization revealed the ferrimagnetic state of the $CoFe_2O_4$ nanoparticles, while their suspensions displayed superparamagnetic behaviour.
Keywords: cobalt ferrite, nanoparticles, co-precipitation, colloidal suspensions, magnetic properties
Published: 30.08.2017; Views: 1856; Downloads: 57
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Synthesis comparison and characterization of chitosan-coated magnetic nanoparticles prepared with different methods
Gordana Hojnik Podrepšek, Željko Knez, Maja Leitgeb, 2014, original scientific article

Abstract: In this study, magnetic maghemite nanoparticles were prepared with the coprecipitation method, due to its simplicity and productivity. Thereafter, chitosan-coated magnetic nanoparticles were synthesized with three different methods, the micro-emulsion process, the suspension cross-linking technique and the covalent binding. Subsequently, a comparison of the used methods was done using various analyses such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA), differential scanning calorimetry (DSC), vibrating-sample magnetometry (VSM) and dynamic light scattering (DLS). The characterization results from Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) indicated a successful binding of chitosan on the magnetic nanoparticles. SEM pictures showed that spherical structured particles with an increased particle size were obtained as the chitosan layer around the particles was increased. Considering that the magnetic-separation technique has the advantages of rapidity, high efficiency, cost-effectiveness and lack of negative effect on the biological activity, these carriers may be applied in enzyme immobilization.
Keywords: magnetic nanoparticles, chitosan, surface functionalization
Published: 23.03.2017; Views: 799; Downloads: 79
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Synthesis of chromium-nickel nanoparticles prepared by a microemulsion method and mechanical milling
Irena Ban, Janja Stergar, Mihael Drofenik, Gregor Ferk, Darko Makovec, 2013, original scientific article

Abstract: A chemical and a physical method have been applied for the preparation of chromium-nickel alloy nanoparticles. These particles were designed to be used for controlled magnetic hyperthermia applications. Microemulsions with $Ni^{2+}$ and $Cr^{3+}$ and/or $NaBH_4$ as precursors were prepared using the isooctane/CTAB, n-butanol/$H_2O$ system. The samples of $Cr_xNi_{1-x}$ nanoparticles with the desired composition were obtained after the reduction of their salts with $NaBH_4$ and afterwards heat treated in a TGA in a $N_2$ atmosphere at various temperatures. The $Cr_xNi_{1-x}$ materials were also prepared by mechanical milling. Utilizing a ball-to-powder mass ratio of 20 : 1 and selecting the proper alloy compositions we were able to obtain nanocrystalline $Cr_xNi_{1-x}$ particles. Thermal demagnetization in the vicinity of the Curie temperature of the nanoparticles was studied using a modified TGA-SDTA method. The alloyʼs phase composition, size and morphology were determined with XRD measurements and TEManalyses.
Keywords: mechanical alloying, magnetic nanoparticles, magnetic hyperthermia, Curie point
Published: 21.12.2015; Views: 1011; Downloads: 67
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A facile route to the synthesis of coated maghemite nanocomposites for hyperthermia applications
Gregor Ferk, Irena Ban, Janja Stergar, Darko Makovec, Anton Hamler, Zvonko Jagličić, Mihael Drofenik, 2012, original scientific article

Abstract: CM-dextran-covered maghemite particles for applications in magnetic hyperthermia treatments were synthesized and their physical, magnetic and morphological properties were examined. Magnetic fluids were prepared and their heating proper ies in an alternating magnetic field were studied. The results reveal that the particle size and the thickness of the carboxy-methyl-dextran (CM-dextran) coatings have a decisive influence on the heating properties: specific absorption rate (SAR). The majority of the magnetic dissipation comes from the Neel relaxation, while the Brown contribution is small. A thermal steady state at the selected temperature (42 °C) can be achieved using synthesized maghemite particles with proper particle morphology and by controlling the magnetic field intensity or the frequency.
Keywords: magnetic nanoparticles, hyperthermia, magnetic properties
Published: 10.07.2015; Views: 1186; Downloads: 68
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2014, doctoral dissertation

Abstract: Cobalt ferrite (CoFe2O4) nanoparticles prepared via co-precipitation method were modified with tetraethoxysilane (TEOS) and additional funkcionalized with 3-mercaptopropyl trimethoxysilane (MPTMS) with purpose of cleaning waste water contaminated with heavy metal ions (Pb2+ and Hg2+). The influence of different experimental parameters (reaction time, reaction temperature and different TEOS:MPTMS ratios) on silica coating of CoFe2O4 nanoparticles and additional on thiol group was systematically studied. Silanes adsorb to the particle surface with alkoxy (Si(OR)4) groups at one end, while functional substituents (-SH) at the opposite end stay extended into surrounding aqueous medium and chemically interact with heavy metal contaminates. Thiol functionalized CoFe2O4 nanoparticles were characterized using IR spectroscopy, X-ray diffraction (XRD), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), energy-dispersive X-ray spectroscopy (EDXS) and vibrating-sample magnetometer (VSM). The thiol functionalized CoFe2O4 nanoparticles were used for Pb2+ and Hg2+ions adsorption from aqueous media. Effect of treatment has been demonstrated using atomic absorption spectroscopy (AAS).
Keywords: cobalt ferrite, magnetic nanoparticles, tetraethoxysilane, 3-mercaptopropyl trimetoxysilane, thiol group, lead, mercury, adsorption
Published: 02.12.2014; Views: 1871; Downloads: 116
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Antimicrobial medical textiles based on chitosan nanoparticles for gynaecological treatment
Tijana Ristić, 2014, doctoral dissertation

Abstract: The aim of this dissertation was to develop a novel medical tampon for alternative gynaecological treatment using chitosan nanoparticles as an antimicrobial agent or as a drug delivery system. For this purpose viscose tampon band was used and functionalized with chitosan and trimethyl chitosan nanoparticles. A comprehensive of interactions between chitosan and cellulose as well as characterization of prepared materials were done. At the beginning, chitosan (CS) and trimethyl chitosan (TMC) solutions, as well as nanoparticles synthesised by ionic gelation were studied. Their characterization was focused on determining the charge and antimicrobial properties against common pathogenic microorganism. The influence of cationic charge on the inhibition of microbial growth was confirmed. Since CS and TMC solutions and nanoparticles dispersions exhibited antibacterial activity against Lactobacillus, a detailed investigation in chitosan’s antimicrobial mode of action was performed using a novel diffusion nuclear magnetic resonance (D-NMR). D-NMR allowed the monitoring of intra- and extracellular water exchange from the cells indicating the membrane alteration and leakage of intracellular constituencies. Further, in order to study the adsorption phenomena and molecular interactions between CS/TMC (solution or nanoparticles) and cellulose material, model cellulose surfaces were used, and adsorption was studied by quartz crystal microbalance with dissipation. CS and TMC were favourably deposited onto cellulose model surface at higher ionic strength, higher pH values, i.e. factors causing lower solubility, where the presence of electrostatic interactions was negligible and non-electrostatic interactions were dominant. The knowledge gained from the model surfaces was extremely helpful in characterization of real systems, i.e. functionalized cellulose fibres and for understanding the obtained results. Immobilization of CS and TMC (in the form of solution and/or nanoparticles) onto cellulose viscose fibres was confirmed with several analytical methods. The attachment of chitosan onto fibres was reversible, as endorsed with desorption studies mimicking the conditions of vaginal usage. Evaluation of antimicrobial properties was performed using two different techniques, both revealing a high inhibition of the tested microorganism. In addition, Lactobacillus susceptibility testing has shown that chitosan-coated fibres do not have any negative influence on the resident microbiota. Assessment of in-vitro cytotoxicity demonstrated that samples do not cause a cytotoxic effect in direct contact. Additionally, model drug was incorporated into chitosan nanoparticles and subsequently attached onto fibres in order to create modern, vaginal drug delivery systems. Antimicrobial medical textiles investigated in the scope of this dissertation show the potential for their exploitation in gynaecological field as preventive or curative treatment without triggering any adverse effects for the user.
Keywords: chitosan, N, N, N-trimethyl chitosan, nanoparticles, antimicrobial activity, cellulose model films, regenerated cellulose fibres, diffusion nuclear magnetic resonance, quartz crystal microbalance, vaginal infections, drug delivery systems, cytotoxicity
Published: 13.02.2014; Views: 2486; Downloads: 110
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The characterisation of nanosized nickel-zinc ferrites synthesized within reverse micelles of CTAB/1-hexanol/water microemulsion
Vuk Uskoković, Mihael Drofenik, Irena Ban, 2004, original scientific article

Abstract: Stoichiometric nanocrystalline nickel-zinc ferrites were synthesized by a reverse micelle method following a multi-microemulsion approach. Different pH values were chosen for the alkali precipitating reaction during the synthesis of different powders. Synthesized, as-dried and subsequently calcined powders were characterized in terms of their magnetic properties. XRD analyses and specific-surface area measurements were used to determine the average particlesizes of the synthesized samples. DCS and TGA measurements were performed to reveal the phase transitions within the samples at elevated temperatures, whereas TEM was used to view and record the microstructure of the nanosized ferrite samples. A possible mechanism of the formation of the synthesized NiZn-ferrite was also discussed.
Keywords: magnetic materials, magnetic nanoparticles, microemulsion synthesis, nickel, iron, fine powders, Ni-Zn ferrites, reverse micelle method
Published: 01.06.2012; Views: 1393; Downloads: 22
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The synthesis of iron-nickel alloy nanoparticles using a reverse micelle technique
Irena Ban, Mihael Drofenik, Darko Makovec, 2006, original scientific article

Abstract: Nanosized Fe0.2Ni0.8 particles were prepared by reducing their salts with sodium borohydride (NaBH4) in cationic water-in-oil (w/o) microemulsions of water/cetyl-trimethyl-amonium bromide (CTAB) and n-butanol/isooctane at 25 °C.According to the TEM and X-ray diffraction analyses, the synthesized particles were around 4-12 nm in size. Due to their nanodimensions, the particles had a primitive cubic (pc) structure rather than the body-centered cubic (BCC) structure of the bulk material. An examination of the synthesis from the reverse micelle reveals that the morphology of the iron-nickel alloy nanoparticles depends mainly on the microemulsion`s composition. The magnetization of the nanoparticles was much lower than that of the bulk material, reflecting the influence of the nanodimensions on the particlesć magnetizations.
Keywords: magnetic materials, nickel/iron alloys, nanoparticles, synthesis, microemulsions, magnetic properties, reverse micelles
Published: 31.05.2012; Views: 1496; Downloads: 84
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