Pore geometry of ceramic device: The key factor of drug release kinetics

Release kinetics of tigecycline, a potential antibiotic in treatment of osteomyelitis, from calcium hydroxyapatite (CHA), as one of the most important ceramic materials in bone tissue engineering, was investigated in this study. Tigecycline, in solid state, was mixed with CHA powder and the obtained mixture was compressed into tablets using two different pressures. These tablets were immersed in a phosphate-buffered saline solution and tigecycline release was measured by a UV-VIS spectrophotometer. The total release time was 5 or 28 days, depending on the pressure applied during compression. It was shown that there is a close relationship between pore sizes and drug release rate. The drug release kinetics was interpreted on the base of pore sizes and pore size distribution. [Projekat Ministarstva nauke Republike Srbije, br. 172026

Ferromagnetic behaviour of the Zn-Mn-O system

Polycrystalline Zn-Mn-O samples with nominal manganese concentrations x = 0.0 1, 0.04 and 0.10 were synthesized by a solid state reaction route using (ZnC(2)O(4 center dot)2H(2)O)(1-x) and (MnC(2)O(4)-2H(2)O)(x). Thermal treatment of the samples was performed in air at temperatures 673, 773, 873, 973 and 1173 K for x = 0.01 and at the temperature 773 K for x = 0.04 and 0.10. The samples were investigated by X-ray diffraction, thermogravimetry, differential thermal analysis, transmission electron microscopy, magnetization measurements and electron paramagnetic resonance. X-Ray diffraction was also performed on MnO(2) thermally treated at temperatures 673, 773, 873, 973, 1073 and 1173 K. Room temperature ferromagnetism was observed in the Zn-Mn-O samples with x = 0.0 1 thermally treated at low temperatures (673 and 773 K) and in the sample with x = 0.04 thermally treated at 773 K. It seems that the ferromagnetic phase could originate from interactions between Mn(2+) and acceptor defects incorporated in the ZnO crystal lattice during the thermal treatment of the samples

Room-Temperature Ferromagnetism in Zn-Mn-O, X-Ray Photoemission Surface Study

Room temperature ferromagnetic properties of Zn-Mn-O show evident dependence on manganese concentration and preparation conditions. We systematically studied series of samples with manganese concentration ranging from 0 to 10 at.%, prepared in air at thermal treatment temperatures ranging from 400 to 900 degrees tau C. The samples were investigated by X-ray diffraction, TEM, magnetization measurements and XPS spectroscopy. XPS analyses of surface composition, chemical bonding and XPS depth profiling were successfully employed on powder revealing the chemical composition at the surface of the grains and underneath. The study emphasizes important role of the grain surface in observed room temperature ferromagnetism. It seems that the ferromagnetic phase is correlated with oxygen build up at the surface.12th Annual YUCOMAT Conference, Sep 06-10, 2010, Herceg Novi, Montenegr

EPR analiza Cd1-xMnxS kvantnih tačaka

Cd1-xMnxS kvantne tačke dijametra d ≤ 4.5 nm su dobijene taloženjem vodenog rastvora. Koncentracije mangana u merenim uzorcima su bile od x = 0.001 do x = 0.25. Izvršena su merenja EPR spektara u oblasti temperatura 20-290 K pomoću 9.5 GHz spektrometra. Za sve koncentracije mangana uočeno je da se spektar sastoji od široke linije i hiperfine strukture. Hiperfina struktura je opisana centralnim (MS = 1/2 ↔ MS = -1/2) dozvoljenim i zabranjenim prelazima sa konstantom hiperfine strukture |A| = 9.6 mT i sa parametrom razdvajanja aksijalnog polja D od 11.1 do 13.5 mT. Hiperfina struktura je pripisana izolovanim Mn2+ jonima na površini nanokristala. Širina široke rezonatne linije koja se ne menja sa temperaturom znači da ona potiče od necentralnih manganovih prelaza proširenih efektom kristalnog polja, kao i u nekim neuređenim materijalimaDrugi seminar mladih istraživača : Decembar 29, Beograd, 2003

Magnetic Properties of Mn-Doped Amorphous SiO2 Matrix

Samples of Mn-doped amorphous SiO2 matrix with manganese concentration 0.7 and 3 at.% have been prepared by a sol-gel method. Transmission electron microscopy analysis has shown that the samples contain agglomerates of amorphous silica particles 10 - 20 nm in size. Two types of Mn-rich particles are dispersed in silica matrix, smaller nanoparticles with dimensions between 3 and 10 nm, and larger crystalline areas consisting of aggregates of the smaller nanoparticles. High-temperature magnetic susceptibility reveals that dominant magnetic phase at higher temperatures is lambda-MnO2. At temperatures below T-C = 43 K strong ferrimagnetism originating from the minor Mn3O4 phase masks the relatively weak magnetism of lambda-MnO2. Magnetic field dependence of the maximum in the zero-field-cooled magnetization for both the samples in the vicinity of 40 K, and a frequency shift of the real component of the AC magnetic susceptibility in the sample with 3 at.% Mn suggest that the magnetic moments of the smaller Mn3O4 nanoparticles with dimensions below 10 nm are subject to thermally activated blocking process just below the Curie temperature T-C. The low-temperature maximum in the zero-field-cooled magnetization observed for both the samples below 10 K indicates possible spin glass freezing of the magnetic moments in the geometrically frustrated Mn sublattice of the lambda-MnO2 crystal structure.12th Annual YUCOMAT Conference, Sep 06-10, 2010, Herceg Novi, Montenegr

Singlet oxygen generation by higher fullerene-based colloids

In this paper, the results of the synthesis and characterization of higher fullerene-based colloids is presented. The generation of singlet oxygen (1)O2 ((1)Delta g) by fullerenc water-based colloids (nC60, nC70 and nC84) was investigated. It was found by electron paramagnetic resonance spectroscopy that the generation of singlet oxygen was the highest by the nC84 colloid. The amplitude of the electron paramagnetic resonance (EPR) signal was two orders of magnitude higher than the amplitude of the EPR signals which originated from nC60 and nC70. The surface morphology and the structure of the particles of the water-based colloids were investigated by atomic force microscopy (AFM). The AFM study showed that the average size of the nC60, nC70 and nC84 were 200, 80 and 70 nm, respectively. In addition, the particle size distribution of the nC60, nC70 and nC84 colloids was determined by dynamic light scattering (DLS) measurements

PO-410 Cytotoxicity and genotoxicity of new gadolinium, iron oxide, cobalt ferrite and graphene oxide nanoparticles on some tumour cell lines in vitro

Nanoparticles (NPs) are increasingly used in cancer therapy as delivery agents and in the diagnosis of malignant diseases as contrast agents for magnetic resonance imaging (MRI). The aim of this work was in vitro assessments of Gd-NPs, Fe- NPs, CoFe-NPs and Graphene Oxide-NPs cytotoxicity and genotoxicity on some tumour and normal human cell lines.Abstracts of the 25th Biennial Congress of the European Association for Cancer Research, Amsterdam, The Netherlands, 30 June – 3 July 201

Sol-gel as a Method to Tailor the Magnetic Properties of Co1+yAl2-yO4

The magnetic properties of mesoscopic materials are modified by size and surface effects. We present a sol-gel method used to tailor these effects, and illustrate it on Co1+yAl2-yO4 spinel. Nanocomposites made of spinel oxide Co1+yAl2-yO4 particles dispersed in an amorphous SiO2 matrix were synthesized. Samples with various mass fractions -x of Co1+yAl2-yO4 in composite, ranging from predominantly SiO2 (x = 10 wt%) to predominantly spinel (x = 95 wt%), and with various Co concentrations in spinel y were studied. The spinel grain sizes were below 100 nm with a large size distribution, for samples with predominant spinel phase. Those samples showed Curie-Weiss paramagnetic behavior with antiferromagnetically interacting Co ions (theta approximate to -100 K). The grain sizes of spinel stays confined in 100 nm range even in the spinel samples diluted with as low as 5 wt% concentration of amorphous SiO2. For the samples with predominant SiO2 the crystalline nanoparticles are well separated and of size of around 100 nm, but with presence of much smaller spinel nanoparticles of about 10 nm. The magnetic properties of the samples with predominant silica phase showed complex behavior, spin-glass magnetic freezing at the lowest temperatures and lower absolute value of theta and consequently lower exchange constant

Magnetic susceptibility studies of Zn1-xFexSe and Zn1-xFexS

The magnetic susceptibility of diluted magnetic semiconductors Zn1-xFexSe and Zn1-xFexS has been calculated within a crystal field model and by applying the extended nearest-neighbour pair approximation. The results are compared with available experimental data. It appears that a good agreement between theory and experiment is obtained for Zn1-xFexSe laking the long-range exchange comprising several nearer interionic distances, whereas in Zn1-xFexS the exchange interaction with nearest-neighbours alone gives a better solution. (C) 1999 Elsevier Science B.V. All rights reserved

Influence of the Fe2+ ion triple clusters on the magnetic susceptibility of Fe-based diluted magnetic semiconductors

Low lying energy levels of Fe2+ ion triples in the cubic-structure iron-based diluted magnetic semiconductors are calculated on the basis of a model which includes crystal field, spin-orbit interaction, Zeeman interaction and Heisenberg-type exchange interaction. Using this energy level diagram the magnetic susceptibility of a crystal is calculated in the nearest-neighbour (NN) and in the extended NN pair approximation, We find that the Fe2+ ion triples contribute to the temperature dependent susceptibility up to the lowest temperatures investigated, T greater than or equal to 1 K. It appears that the triple Fe2+ ion clusters may explain at least a part of the low-temperature increase of the magnetic susceptibility which is observed in these magnetic materials. (C) 2001 Elsevier Science B.V. All rights reserved