Karlo Karlovic | Ruder Boskovic Institute (original) (raw)

Papers by Karlo Karlovic

V 2 O 5 particles were precipitated by the sol -gel method, then subjected to heat treatment. Sam... more V 2 O 5 particles were precipitated by the sol -gel method, then subjected to heat treatment. Samples were analyzed using XRD, TGA/DTA, FT-IR, Raman and transmission electron microscopy (TEM) techniques. XRD showed an amorphous-like structure of these particles with the beginning of their crystallization, whereas TEM showed their fibrillar morphology. In the FT-IR spectrum of the starting sample, not all bands typical of the crystalline V 2 O 5 spectrum were developed. The Raman spectrum showed all bands of V 2 O 5 , however, with a significant broadening. The fibrillar morphology of V 2 O 5 particles was disappearing with increase in the heating temperature, and at 600 jC, only big particles of irregular shape were obtained. Heating of the starting V 2 O 5 particles in argon atmosphere up to 600 jC produced the V 3 O 7 phase as associated with the predominant V 2 O 5 phase. D

Two kinds of nanosize V 2 O 5 particles were synthesized in our own laboratory and concomitantly ... more Two kinds of nanosize V 2 O 5 particles were synthesized in our own laboratory and concomitantly applied to V79 and L929 fibroblasts and SCCVII, B16F10 and FsaR tumor cells. The morphologies of the cells were monitored using an inverted inverse microscope equipped with digital camera, while quantitative determination of the cytotoxicity of nanosize V 2 O 5 particles was measured using crystal violet bioassay. Twenty four hours after the addition of nanosize V 2 O 5 particles (20 lM), noticeable changes in the morphology and density of fibroblast and cancer cells were observed. Reculturing in a freshly prepared medium for the next 24 h showed a high recovery effect on V79, SCCVII and B16F10 cells, while FsaR and L929 cells were seriously damaged and unable to recover. At a higher concentration of nanosize V 2 O 5 particles (100 lM), the cytotoxicity of V 2 O 5 prevailed against the recovery effect in all cell types. Quantitative measurements have shown that the resistance of investigated cell cultures to the cytotoxicity of nanosize V 2 O 5 particles decreases in the order V79 > SCCVII > B16F10 > FsaR > L929. The high cytotoxic effect found on FsaR cells suggests that nanosize V 2 O 5 particles could be regarded as poisoning material in the treatment of FsaR fibrosarcoma cells. Possible mechanisms involved in the cytotoxicity of nanosize V 2 O 5 particles were discussed.

Raman scattering was applied as a probe for the evolution of the crystalline size and distributio... more Raman scattering was applied as a probe for the evolution of the crystalline size and distribution of nanosized TiO 2 . Small physical dimensions of TiO 2 crystals lead to a shift and broadening of the first-order Raman lines through a relaxation of the q 0 selection rule and affects on to the position of a low-frequency Raman (LFR) band. The details of the evolution of the 144 cm Ϫ1 Raman line shape (frequency, broadening and asymmetry) on the size and distributions of the nanocrystals are presented. The methodologies for the size determination of nanocrystals using the LFR mode together with a deconvolution treatment to obtain the size distribution were analyzed. Both the Raman results were compared with the grain size distribution obtained by high-resolution electron microscopy. ᭧

Coprecipitates, Ni(OH) 2 + 2Fe(OH) 3 , were milled in a planetary mill, using an agate bowl and b... more Coprecipitates, Ni(OH) 2 + 2Fe(OH) 3 , were milled in a planetary mill, using an agate bowl and balls (99.9% SiO 2 ), and then heated at a maximum temperature of 573 or 773 K. The Mo È ssbauer spectra at 298 K of the ball-milled samples (not heated) showed the superposition of two quadrupole doublets. After heating at 573 K, the superposition of two doublets was preserved at 298 K with a slight increase in the quadrupole splitting for the sample ball-milled for 64 h. After heating at 573 K, the ball-milled samples showed at 80 K a central quadrupole doublet and a sextet with very broad lines. All the samples heated to 573 K were amorphous for according to X-ray di raction while those heated to 773 K exhibited crystalline NiFe 2 O 4 with broadened di raction lines. At 298 K, superposition of two sextets in the Mo È ssbauer spectra was observed for the samples obtained after heating at 773 K, indicating the presence of nickel ferrite as a single phase. The average sizes of NiFe 2 O 4 crystallites were in the nanosize range (8± 12 nm). The Fourier transform infrared spectra of the samples heated at 773 K showed two very strong bands with positions at 601± 603 and 408± 411 cm -1 , which can be ascribed to NiFe 2 O 4 .

Nanosized TiO, powders were prepared using the sol-gel procedure. The selected colloidal suspensi... more Nanosized TiO, powders were prepared using the sol-gel procedure. The selected colloidal suspensions were stabilized with polyethylene glycol (PEG). This polymer prevented sintering of TiO, particles during the calcination of the starting material. X-ray powder diffraction (XRD) phase analysis showed that the samples, obtained up to 5OO"C, were a mixture of anatase and brookite. In the samples, obtained at 850°C and higher temperatures, rutile as a single phase was detected. The TGA/DTA curves were dependent on the preparation of TiO, samples. The samples were also characterized by Fourier transform infrared spectroscopy and laser Raman spectroscopy. A new method, based on low-frequency Raman scattering, was proposed for the size determination of nanosized TiO,. The size determination of nanosized TiO, by low-frequency Raman scattering was in a good agreement with crystallite size values obtained by XRD. 0 1997 Elsevier Science S.A.

Low wavenumber Raman scattering of the acoustic vibrational modes of nanoparticles was used for t... more Low wavenumber Raman scattering of the acoustic vibrational modes of nanoparticles was used for the determination of the size distribution of free dielectric and semiconductor nanoparticles and of nanoparticles embedded in matrices. The theoretical background as well as the experimental results for the free noninteracting nanoparticles and for the nanoparticles in strong interaction with a surrounding matrix is described. The approach is based on a 1/n dependence of the Raman light-to-vibration coupling coefficient and on the fact that each nanocrystallite of diameter D vibrates with its eigenfrequency n ∼ 1/D. The model calculation considers the inhomogeneous broadening due to contribution from the particles of different sizes, and homogeneous broadening due to interaction of particles with the matrix. The comparison of the calculated and experimental low wavenumber Raman spectra are presented for SnO 2 , TiO 2 and CdS free nanoparticles and TiO 2 , CdS x Se 1−x and HfO 2 nanoparticles embedded in a glass matrix. The particle-size distributions determined by Raman scattering were compared to those found by TEM measurements. Raman spectroscopy proved to be a simple, fast and reliable method for size-distribution measurements. By an inverse procedure, starting from the Raman spectra and known particle-size distribution, a new method for the determination of the mean sound velocities of longitudinal and transverse phonons of nanoparticles is described.

The effects of iron on the structural properties of Zn-borosilicate glasses have been studied usi... more The effects of iron on the structural properties of Zn-borosilicate glasses have been studied using X-ray diffraction, IR spectroscopy and ST Fe M6ssbauer spectroscopy.-Znborosilicate glasses were doped with a-Fe203. In the systems Na~O-ZvO-B203-SiO 2 -Fe2 O3 the presence of only one crystalline phase, ZnFe2 O4, was detected. X-ray diffraction showed that crystallization is more pronounced in the systems ZnO-B203-SiO2-Fe203. In these systems the presence of different crystalline phases, such as ZnO, 7-Fe 2 Oz, Fe z O,, ZnF% O, and Fe 3 BO 5 , was detected. The crystalliz~ition of cr 4 in the system ZnO-B2Oa-SiO 2 was confirmed by X-ray diffraction and IR spectroscopy. The valence state and coordination of iron in Zn-borosilicate glasses were determined by s 7 Fe M6ssbauer spectroscopy. corrosion properties of these glasses. In oxide glasses, iron Pnay exist in the form of Fe 3+ and/or Fe 2+. Generally, these ions are distributed between different structural sites.

The effects of iron on the structural properties of Zn-borosilieate glass and Pb-metaphosphate gl... more The effects of iron on the structural properties of Zn-borosilieate glass and Pb-metaphosphate glass were studied using X-ray diffraction, s ~Fe M~ssbauer spectrosCopy and IR spectroscopy. Zn-borosilieate glass was prepared with varying amounts of Fe 203 (up to 30% wt.). It was found that the chemical form of added iron (,,-FeOOH, a-Fe203 or Fe304) affects the Fe3+/Fe 2 § ratio, as well as the distribution of iron ions at different coordination sites. At high concentration of iron the crystallization of zinc ferrite in the glass matrix takes place. X-ray diffraction and 5 ~Fe M6ssbauer spectroscopy showed that the amount of zinc ferrite in Zn-borosflieate glass decreases with the following order of addition: a-FeOOH~t~-Fe203-*F%O 4 . In Pb-metaphosphate glass doped with high concentration of a-Fe20 ~, the erystaUization of Fe3(PO,) 2 is pronounced. The assignments of IR band positions and the corresponding interpretation are given. The importance of this study for the technology of vitrification of high-level radioactive wastes is emphasized.

The influence of experimental conditions on the formation of nanosize magnetite by micro-emulsion... more The influence of experimental conditions on the formation of nanosize magnetite by micro-emulsion method was investigated using Mössbauer and FT-IR spectroscopies, FE SEM/EDS and TEM. It was found that the concentration of starting chemicals (FeCl 3 /FeSO 4 ), aeration/de-aeration, high alkalinity and γ-irradiation influenced this precipitation process. Rod-like goethite particles ∼200-300 nm long and up to 10 nm wide were obtained by destabilization of the micro-emulsions aged 5 to 45 days at RT. Si-containing ferrihydrite was also formed and it retarded the formation of goethite by the dissolution/re-precipitation mechanism. A small amount of Si from a glass flask was dissolved. A very strong influence of γ-irradiation on the formation of nanosize magnetite by micro-emulsion method was observed. γ-irradiation created strong reductive conditions in the micro-emulsions. At an ∼460 kGy dose, nanosize magnetite particles sized ∼5 to 20 nm and very small amounts of goethite particles were obtained. The EDS measurements on the particles suggested the formation of substoichiometric magnetite (Fe 3−x O 4 ) and not of maghemite. This finding is in line with the strong reductive conditions induced with γ-irradiation.

Ti(IV)-isopropoxide was hydrolyzed with water molecules generated "in situ" by an esterification ... more Ti(IV)-isopropoxide was hydrolyzed with water molecules generated "in situ" by an esterification between carboxylic acid and alcohol providing excellent control of the hydrolysis and condensation rate. Raman and FT-IR spectra of the TiO 2 -acetate precursor suggested that the organic ligand is chemically bound to the titanium. With heating of the TiO 2 -acetate precursor up to 320ЊC, the surface area increased from 3 to 280 m 2 g Ϫ1 . The organic component completely decomposed above 320ЊC. With a further increase in temperature, the surface area of the nanocrystalline anatase gradually decreased. The method of lowfrequency Raman scattering was used to determine the particle size in dependence on experimental conditions, and a good agreement was obtained with the crystallite size determination using the Scherrer method. ᭧

Glasses are suitable host matrices for the immobilization of high-level radioactive wastes. The c... more Glasses are suitable host matrices for the immobilization of high-level radioactive wastes. The corrosion behaviour of nuclear waste glass in water is of considerable importance, since a potential route for returning of radionuclides to the biosphere is their leaching from the waste form into groundwater and subsequent transport by the groundwater to the surface. In this study, the preparation and characterization of borosilicate glasses of different chemical composition were investigated. Borosilieate glasses were doped with simulated nuclear waste oxides. The chemical corrosion in water of these glasses was followed by measuring the leach rates (g'cm-2"day-~), as a function of time. It was found that a simulated nuclear waste glass with the chemical composition (weight %), 15.61% Na20, 10.39% B~O3, 45.31% SiO2, 13.42% ZnO, 6.61% TiO2 and 8.66% waste oxides, is characterized by low melting temperature and with good corrosion resistance in water. Influence of passive layers on the leaching behaviour of nuclear waste glasses is discussed.

Factors that influence the precipitation of iron oxides from Fe(II) containing solutions were inv... more Factors that influence the precipitation of iron oxides from Fe(II) containing solutions were investigated by X-ray powder diffraction, 57 Fe Mössbauer and FT-IR spectroscopies, FE SEM and EDS techniques. Near spherical aggregates of spindle-shape goethite particles were obtained by oxidation of 0.1 mol dm -3 FeSO 4 solution (suspension) with pure oxygen at 90°C. Wide and thin goethite particles elongated along the crystallographic c-axis were formed in parallel. With the addition of tetramethylammonium hydroxide to 0.1 mol dm -3 FeSO 4 solution (suspension) substoichiometric magnetite (Fe 3-x O 4 ) particles were additionally formed. They were dominant at pH > 12.5. Mössbauer spectroscopy was used to calculate the stoichiometries of Fe 3-x O 4 particles. Very small magnetite particles (» 20-100 nm) showed a tendency to aggregate. The twinning effect of octahedral magnetite particles (> 200 nm) was observed. A drastic effect on the properties of iron oxide precipitates was achieved by adding H 3 PO 4 to the precipitation system containing 0.1 mol dm -3 FeSO 4 + 0.01 mol dm -3 H 2 SO 4 solution at the start. In dependence on the concentration of the added H 3 PO 4 , nanosize goethite particles about 15-25 nm in size, or poor crystalline ferrihydrite particles (two-line ferrihydrite) were obtained. The EDS analyses of the precipitates did not show any significant change in the sulphur content, whereas the phosphorous content gradually increased in the precipitates with an increase in the added H 3 PO 4 . In high concentrations phosphates completely suppressed the formation of goethite under given experimental conditions, and phosphated ferrihydrite was formed instead. Keywords ferrihydrite magnetite phosphate Mössbauer FE SEM CROATICA CHEMICA ACTA CCACAA 81 (4) 569¿578 (2008) Croat. Chem. Acta 81 (4) 569¿578 (2008)

Modified hydrothermal and 'wet' precipitation routes at room temperature were employed to synthes... more Modified hydrothermal and 'wet' precipitation routes at room temperature were employed to synthesise pure monoclinic BiVO 4 powders of varying particle morphologies. Monoclinic BiVO 4 powder was also prepared by a solid-state reaction at 7008C. Depending on the synthesis conditions, the colour of BiVO 4 varies from inhomogeneously yellow-brown to homogeneously and intensive lemon yellow. BiVO 4 prepared by solid-state reaction consisted of large compact particles about 15 mm in size and of irregular shape. At higher magnification, the formation of domains with smooth terrace-like surfaces was observed. These domains ended with well-defined walls, and the edges of these walls were relatively very sharp. BiVO 4 synthesised by the hydrothermal and an aqueous process at RT consisted of smaller particles (0.3-1.2 mm) and of much bigger regular crystals with a well-defined crystal habit. A continuous shift of the most intense Raman band to lower wavenumbers reveals that the average short range symmetry of the VO 4 tetrahedra becomes more regular. The values of FWHM for the same Raman band increase from sample prepared by solid-state reaction to sample obtained at RT. The Raman results suggested that a sample prepared at high temperature consisted of less symmetric VO 4 tetrahedra than samples prepared at low temperature and that the high-temperature sample showed better crystallinity with less defects than the samples prepared by an aqueous process under mild conditions. FT-IR spectra showed main features typical of the vanadates of other metal(3C) cations. However, the position of IR bands recorded for BiVO 4 depended on the synthesis route. q

A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi 2 ... more A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi 2 O 3 precursor, which was then heated to 400 or 500°C. β-Bi 2 O 3 obtained at 400°C showed well-shaped plate-like particles. The mixture β-Bi 2 O 3 /α-Bi 2 O 3 , obtained by prolonged heating at 400°C, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. α-Bi 2 O 3 obtained at 500°C consisted of particles of varying shapes and sizes. Vitrification of α-Bi 2 O 3 was also observed. XRD showed a small fraction of unidentified phase(s) in these samples. Different microstructures were obtained when the precipitation from aqueous Bi(NO 3 ) 3 solution with tetramethylammonium hydroxide at pH ∼ 14 was used. The precipitation at pH ∼ 3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La 0.26 Bi 0.24 )Bi 0.5 OOH. It was found that these particles were made up of much smaller primary BiOOH particles.

Tungsten trioxide hydrates were synthesized by (a) cation exchange reaction from sodium tungstate... more Tungsten trioxide hydrates were synthesized by (a) cation exchange reaction from sodium tungstate solution and (b) precipitation from sodium tungstate solution by the addition of HCl solution. The samples were analyzed by XRD, DTA/TGA, Raman and FT-IR spectroscopy. XRD showed formation of WO 3 ·H 2 O by cation exchange reaction, whereas WO 3 ·0.33H 2 O was identified by XRD as a product of the acidification of sodium tungstate solution with HCl solution. After heating at 320°C, WO 3 ·H 2 O transformed into WO 3 , whereas the WO 3 ·0.33H 2 O crystal structure remained and these results were in agreement with DTA/TGA measurements. The WO 3 ·H 2 O sample synthesized by cation exchange reaction showed a weight loss corresponding to one molecule of water in the crystal structure. However, samples WO 3 ·0.33H 2 O showed a much greater weight loss upon heating than could be expected on the basis of the WO 3 0.33H 2 O formula. The phase transition WO 3 ·H 2 O WO 3 was also monitored by Raman and FT-IR spectroscopy. In the case of WO 3 ·0.33H 2 O samples, the basic features of Raman and FT-IR spectra did not change on heating to 320°C, thus indicating that the heating of WO 3 ·0.33H 2 O up to this temperature did not destroy the original crystal structure. Contrary to this, after heating the WO 3 ·H 2 O sample to 320°C, the Raman and FT-IR spectra showed a series of new bands caused by the phase transition WO 3 ·H 2 O WO 3 .

Background: Particulate air pollution in lung epithelial cells induces pathogenic endpoints like ... more Background: Particulate air pollution in lung epithelial cells induces pathogenic endpoints like proliferation, apoptosis, and pro-inflammatory reactions. The activation of the epidermal growth factor receptor (EGFR) is a key event responsible for signalling events involving mitogen activated protein kinases specific for these endpoints. The molecular events leading to receptor activation however are not well understood. These events are relevant for the toxicological evaluation of inhalable particles as well as for potential preventive strategies in situations when particulate air pollution cannot be avoided. The current study therefore had the objective to elucidate membrane-coupled events leading to EGFR activation and the subsequent signalling cascade in lung epithelial cells. Furthermore, we aimed to identify the molecular target of ectoine, a biophysical active substance which we described to prevent carbon nanoparticle-induced lung inflammation.

Mö ssbauer and Fourier transform infrared (FT-IR) spectroscopies and thermal field emission scann... more Mö ssbauer and Fourier transform infrared (FT-IR) spectroscopies and thermal field emission scanning electron microscopy (FE SEM) were used to investigate the precipitation of iron oxides from FeSO 4 solutions. The hydrolysis of urea at 90°C was utilized as a generator of OH À ions needed for the precipitation of iron oxides. The formation of specific iron oxyhydroxide or oxide phase depended on the concentration of FeSO 4 and urea, as well as on the rate of oxygenation. In dependence on the experimental conditions different iron oxide phases, such as goethite, hematite and magnetite were found in the precipitates. Mö ssbauer spectra showed only the formation of substoichiometric magnetite (Fe 3-x O 4 ). Significant spectral differences in the RT Mö ssbauer spectrum of goethite phase were observed, and the spectra showing the presence of this phase could be fitted only taking into account the distribution of hyperfine magnetic fields. FE SEM inspection showed varying sizes and geometrical shapes of goethite particles. Goethite particles were elongated along the crystallographic c-axis.