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The physical and chemical features of tuned, shape-selected ZnO particles are discussed in terms of response to external hydrostatic pressure using the Synchrotron Powder X-ray diffraction measurements, degradation kinetics over dye pollutant in aqueous solution and X-ray Photoelectron Spectroscopy fingerprints, latter giving an insight into the morphological versatility and surface diversity of ZnO powder. The microstrain responses of the ZnO NPs to the applied hydrostatic pressure were studied up to 30 GPa, while the photocatalytic reactions were carried over the RhB dye pollutant molecules. We comparatively showed that the diversity of size and shape of ZnO particles distinguishes the wurtzite-to-rocksalt transformation reversibility phenomena by dictating the microstructure- dependent deformation behavior and ultimately leads to different microstrain responses to hydrostatic pressure. Moreover, we mimicked theoretical breakthroughs at the Density Functional Theory level leading to morphology- driven ZnO NPs. The exceptionally high apparent- rate constant of 9.7(2)× 10-2 min-1 highlights the role of spherical ZnO NPs grown hydrothermally from ethanolic solution towards the giant, spindle-shaped ZnO particles prepared in NaOH medium with calcination treatment. By understanding the crystal growth of ZnO NPs via the molecular ZnO interface/solvent/additive interactions and screening the solution chemistry of ZnO NPs, one can make ZnO a highly efficient promising multifunctional material.

Microstructural features have an important role in optimizing the properties of ZnO nanoparticles (NPs) and are essential factors for flexible applications. The importance of theoretical understanding beyond systematic pathway set-ups, which can lead to the design of morphologically targeted ZnO NPs is of key importance. By integrating synthesis of ZnO particles using different methods, and structural property measurements, aided by theory calculations we singled out the optimal ZnO candidate with morphology-dependent functionalities. This study highlights the physical and chemical peculiarities of shape-selected ZnO particles prepared by different routes, concisely elaborating the mechanical response to external hydrostatic pressure via Synchrotron Powder X-ray diffraction experiments, degradation kinetics over RhB dye pollutant and X-ray Photoelectron Spectroscopy fingerprints, latter giving an insight into the morphological versatility and surface diversity of ZnO polycrystals. We mimicked theoretical breakthroughs at the Density Functional Theory level leading to morphology-driven ZnO NPs, reflecting enhanced catalytic activity and pressure induced internal strain contributions to the mechanical properties of nanocrystalline ZnO particles. The microstrain responses of the ZnO NPs to the applied hydrostatic pressure were studied up to 30 GPa, while the degradation measurements were carried over the RhB dye pollutant molecules. We comparatively showed that the diversity of size and shape of ZnO particles distinguishes the wurtziteto- rocksalt transformation reversibility phenomena by dictating the microstructure-dependent deformation behavior and ultimately leads to different microstrain responses to hydrostatic pressure. The exceptionally high apparent-rate constant of 9.7(2)× 10 min highlights the role of spherical ZnO NPs grown hydrothermally from ethanolic solution towards the giant, spindle-shaped ZnO particles prepared in NaOH medium with calcination treatment. It seems that by understanding the crystal growth of ZnO NPs via the molecular ZnO interface/solvent/additive interactions and screening the solution chemistry of ZnO NPs, one can make ZnO a highly efficient promising multifunctional material. Based on the above results, the prospect of being able to synthesize pure ZnO NPs that efficiently degrade ∼99% of the RhB dye pollutant in 50 min serves as a continuous incentive for future research.

Structural and microstructural features of ZnO particles prepared by different routes were determined by pressure-induced synchrotron powder X-ray diffraction measurements and complemented by the results of optical micrographs showing the morphological diversity of different ZnO polycrystals. In particular, the pressure-induced change in crystallite size and the contributions of internal strain to the mechanical properties of nanocrystalline ZnO were systematically scaled. A transition from wurtzite to rocksalt phase in ZnO with spherical nanoparticles grown hydrothermally from ethanolic solution resulted in a strong ∼21% collapse in unit cell volume at ∼17.68 GPa, whereas compression of spindle-shaped ZnO particles prepared in NaOH with calcination treatment led to the formation of an exclusively cubic phase at 13.77 GPa, reflecting a ∼20% unit cell volume collapse. Interestingly, the fingerprints of the cubic diffraction patterns in spherical ZnO did not reappear upon decompression from ∼29 GPa - the hexagonal structures were preserved beyond the upward transition pressure, whereas in contrast, a very different trend was observed in spindle-shaped ZnO after depressurization, showing a reversible pressure- induced structural transition to single-phase hexagonal symmetry by slowly depressurizing from 15.46 GPa to ambient pressure. These different features point to a rather contradictory revresibility phenomenon that needs to be investigated: why do the phase-pure ZnO samples of the cubic assemblies show different transformation activities at the same pressure ranges? This tricky behavior results from the differences in surface energy between the crystalline phases and the volume collapse ratio. In addition, the particle size significantly affects the pressure range of phase stability and the final ratios of rocksalt and wurtzite phases at ambient conditions in different ZnO samples. The microstrain response of ZnO particles to applied hydrostatic pressure was investigated up to 30 GPa and revealed that the diversity of ZnO particle size and shape determines the reversibility of wurtzite to rock salt transformation by dictating the microstructure-dependent deformation behavior and ultimately leading to different microstrain responses to hydrostatic pressure.

Uslijed mehaničke traume, ozljede ili zbog nepravovremeno liječenog karijesa i paradontoze može doći do djelomičnog ili potpunog gubitka zuba/zubiju. Kako bi se održala kakvoća života pojedinca problem se rješava ugradnjom dentalnih implantata – metalni vijak, kao baza za keramičku krunicu, most ili zubnu protezu, ugrađuje se u kost čeljusti. Za izradu dentalnih implantata najčešće se koriste materijali na osnovi titanija. Za uspješnu implantaciju i kako bi se izbjegle bolne korekcijske operacije, po ugradnji implantata mora doći do brze oseointegracije s okolnom kosti i tkivima. Kako formiranje postojanih interakcija implantni materijal/kost i implatni materijal/okolno tkivo ovisi o mikrostrukturi, morfologiji i sastavu te hidrofilnosti površine, funkcionalizacija površine implatnog materijala je od ključne važnosti. U ovom istraživanju, provedena je funkcionalizacija površine titanijeva dentalnog implantata kemisorpcijom bioaktivnih molekula, mogućih pojačivača oseointegracije. Morfologija modificiranih površina Ti|TiO2|bioaktivna prevlaka ispitana je koristeći SEM, a svojstva močenja pomoću mjerenja kontaktnog kuta. In vitro karakterizacija nemodificiranih i modificiranih površina provedena je u otopini umjetne sline upotrebom elektrokemijske impedancijske spektroskopije. Eksperimentalna otkrića potvrđena su DFT izračunima i predložen je mehanizam formiranja bioaktivnih prevlaka.

Since implantation success strongly depends on the osseointegration process, current trends in dental implant research are based on surface properties modifications by biomimetic and bioactive coatings that mimic biochemical surroundings and architecture of the human bone. Calcium phosphate ceramics, like hydroxyapatite, with mineral composition similar to natural bone, as a single compound coating or as a composite with collagen, bioglass, or silica are used to promote osseointegration or overall implant system’s characteristics. Drug-based coatings with bisphosphonates like Zolendronate or Alendronate, drugs for bone diseases, promote mechanical fixation of implant and bone mineralization. However, it must not be forgotten that a fundamental prerequisite for the success of osseointegration is a long-term corrosion stability of implant materials. Human body fluids, especially oral cavity fluids, in which pH is constantly changing, represent very aggressive media with high concentrations of chloride ions that are among the most aggressive and corrosive to metals. Although titanium is a gold standard in dental implantology due to its exceptional biocompatibility and corrosion resistivity, there is an increasing data reported regarding complications caused by titanium dental implant fixation. It was shown that titanium ions, that originated as product from corrosion reaction in body fluids, caused negative immune reactions or skin allergies immediately or shortly after implant fixation. Therefore, it is crucial to design a coating which will make titanium surface more bioactive/osseoinductive and at the same time more corrosion resistant during a long-term exposure to oral cavity fluids. In this study the titanium surface was modified by vitamin D3, molecules that are crucial for maintaining bone mineral density and normal functioning of the immune system. The main goals were (i) to improve titanium corrosion resistivity during exposure to an artificial saliva solution and simultaneously (ii) to induce in vitro processes of “new bone” formation. According to results of all techniques, the D3 vitamin layer imparted very good corrosion protection to the oxide-covered titanium and induced a formation of biocompatible bone-like calcium phosphates what confirmed enhanced titanium's bioactivity level.

Although dental implants have been used since ancient times, there is a continuing need to improve characteristics to ensure their long- term integration into the jaw.^1 Current trends in dental implant research are focused on surface properties modification by biomimetic and bioactive coatings that mimic architecture of the human bone and biosurrounding.^2-4 Therefore, the titanium dental implant was functionalized by two different molecules, Cholecalciferol (vitamin D3) and Alendronate sodium (Fosamax®T). D3 vitamin and Alendronate were chosen due to their known positive influences on human organism, especially on the bone-system. The aim of functionalization was (i) to improve anti-corrosion properties of the implant and simultaneously (ii) make implant´s surface potentially more bioactive (to promote and accelerate osseointegration). An integrated experimental-theoretical approach was applied to study coating´s formation mechanism, wetting properties and corrosion behaviour in an artificial saliva solution (during 7 days). In general, the results indicate improved surface properties of the implant after functionalization and are in a direct corelation with chemical nature and structure of coating molecules.

The objective of the study was to obtain potential biocontrol agents of green mould disease, caused by Trichoderma spp., affecting the most commonly cultivated basidiomycetes: white button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus spp.). The isolation of bacterial strains with antagonistic properties against Trichoderma spp. was carried out from samples of straw and chicken manure, compost at various stages of the composting process and casing soil used for growing button mushrooms. Bacterial isolates characterized as Gram-positive and catalase- positive were identified based on the hypervariant region of the 16S rDNA as: Bacillus subtilis, B. amyloliquefaciens, B. licheniformis and B. pumilus. After a preliminary screening of bacterial isolates for antagonistic activity against Trichoderma aggressivum f. europaeum further screening was conducted with additional indicator isolates of fungi: T. harzianum, T. koningii and T. atroviride. Growth inhibition of Trichoderma spp. ranged from 40 to 70 % depending on the antagonistic strain and fungal indicator. The strains with the strongest antagonistic activity were selected for in vivo experiments in which the efficacy of strains in pathogen suppression and their effect on mushroom yield were evaluated, in comparison with a commercial biofungicide based on Bacillus velezensis QST 713 and a fungicide based on prochloraz-Mn. In mushroom growing room trials against T. aggressivum f. europaeum, the most effective treatment in pathogen control was prochloraz-Mn, followed by the native B. amyloliquefaciens B-241, B. velezensis QST 713, B. pumilus B-138 and B. subtilis B- 233. Strain B. amyloliquefaciens B- 241 showed the greatest potential for biocontrol of green mould disease in button mushroom production caused by various Trichoderma species, which makes it a good candidate for further trials at commercial scale. In addition, antagonistic potential of ten chosen Bacillus subtilis strains was evaluated against causal agents of green mould disease of oyster mushroom, Trichoderma pleuroti and Trichoderma pleuroticola. Based on the in vitro method for quantification of antagonistic potential of Bacillus spp. strains, growth inhibition of T. pleuroti ranged from 55 to 62 % and no significant differences among antagonistic activity of tested B. subtilis strains were found. Inhibition of T. pleuroticola was slightly higher, ranging from 55 to 70 % and strain B. subtilis B- 358 induced the highest growth inhibition thus showing promising results for further in vivo trials. This research confirmed mushroom substrate to be a good source of antagonistic microorganisms with potentials for use in biological control of green mould control in edible mushroom production. This work was supported by bilateral project 337- 00- 205/2019-09/21.

In the research of multifunctional properties, one of the most important targets is a thorough understanding of a correlation between structural features of material and desired physical and chemical properties. High thermal stability makes BaAl2O4 suitable for fabrication of fluorescent lamps, LEDs, FEDs, etc. – this especially refers to doped BaAl2O4 due to optimal combination of microstructural, electrical, and optical parameters [1]. Physical properties of BaAl2O4 host can be controlled by modification of crystal structure and electronic state by partial substitution of Al and Ba sites cations and/or thermal treatment under reduction conditions [2]. The influence of Co2+ on the BaAl2O4 lattice and its magnetic properties was explored using the PXRD, Uv-Vis and magnetic studies. Magnetization measurements of BaAl2O4 doped with 4, 8 and 12 at. % Co in form of pressed pellets were performed using SQUID magnetometer at temperatures 2 - 400 K and fields up to 5 T. We found that by increasing the amount of Co, resulting magnetization also increases in otherwise non-magnetic BaAl2O4 material. In order to describe magnetic behaviour, it was necessary to include magnetic anisotropy of paramagnetic Co2+ ions. Since BaAl2O4 is ferroelectric [3], very motivating is similar work where Fe doping of ferroelectric BaTiO3 produced also the magnetic response of material [4]. If considerable magnetic response could be obtained, it could lead to the novel magnetoelectric and/or multiferroic state in doped BaAl2O4.

In technologically intense and competitive search for the applicable and best-in-class materials, one of the most important targets and a crucial step includes a meticulous planning of the research strategy and collection of a high quality experimental data, in order to find and/or boost the optimal combination of their physical and chemical characteristics, delivering a sistematically tailored functionalities of the final product. Regardless of whether we have a pure inorganic, or hybrid, inorganic-organic material, an understanding the synergy of accurate crystal structure, sufficient purity, tunable particle and/or strain size is still a quite challenging multitask. Keeping in mind the correlation of these parameters, the application of the room temperature (RT) powder X-ray diffraction (PXRD) and structural evolution with pressure from the synchrotron radiation experiments are independently highlighted on the selected inorganic and inorganic-organic exemplars, pointing out the necessity and preciousness of this characterization method, without which it would be impossible to relate the crystal structure to physical properties. The possibility of performing the non-ambient in situ synchrotron radiation experiments, enables deeper insight into the correlation between structural features (e.g phase transition mechanism) and mechanical properties of functional materials.

Life inevitably leaves its traces on the teeth. A mechanical trauma, an accident or untimely treated caries and periodontitis frequently lead to permanent tooth loss. Dentists and dental specialists have a contemporary solution: the small titanium body fixed into the jawbone acts as the base for single crowns, larger bridges or dentures. Titanium dental implants, in the form of screw (endosseous implants), are various-age appropriate secure solution and are the most used implants. Since a dental implant, generally metal-made, represents a foreign body for the patient, many difficulties can occur. Therefore, for successful implant application, the dental industry has to consider all relevant factors that are related to dental reconstruction and restoration like biocompatibility, osseointegration, corrosion resistance, implant geometry design, mechanical stability, and implant/bone and implant/surrounding tissue interactions. Once the implant is placed within the jaw, it should rapidly osseointegrate with surrounding bones and tissues and create a stable implant/surrounding bone interface. It is clear, implant-bone and implant-surrounding tissue interactions are affected by the implant surface microstructure, composition, morphology, roughness and hydrophilicity. Hence, surface engineering plays a significant role in the improvement of the implantation process, especially osseointegration. Many studies report about surface modification of dental implants (e.g., sandblasting, acid etching, anodization, self-assembling etc.) in order to optimize and improve their surface characteristics and enhance implantation. In this study, the titanium implant surface was functionalized by chemisorption of osseoinductive molecule using a facile and effective approach. The morphology of the modified implant surface, Ti/TiO2/bioactive coating, was examined by SEM and wetting properties by contact angle measurements. Electrochemical properties of the Ti/TiO2/bioactive coating were studied in vitro in artificial saliva solution using electrochemical impedance spectroscopy. The experimental findings were corroborated by means of DFT calculations. The formation mechanism of bioactive implant coating was proposed considering experimental results and a computational study of Gibbs free energies of bioactive molecule/TiO2 molecular interactions.

Alkaline earth aluminates are promising starting compounds for the preparation of fluorescent and phosphorescent doped materials. The room- temperature (RT) phase of BaAl2O4 becomes a luminescent material with emission in the red or blue-green spectral range when doped with Eu3+ or Eu2+ ions, respectively. The quite complicated crystal structure of the host material (hexagonal system, space group P63) with several possible lattice sites for the Eu dopant makes XAFS an ideal tool to determine the Eu position and its coordination in Eu-doped BaAl2O4. Here we investigate the influence of Eu doping on the structure of BaAl2O4 by means of XAFS at RT. Nanosized powder samples of pure BaAl2O4 and one doped with 4.9 at.% Eu in relation to Ba were prepared from Ba(NO3)2, Al(NO3)3·9H2O, and Eu(NO3)3·6H2O using a hydrothermal route followed by a thermal treatment at 1100 °C for 4h. For the XAFS studies, the powder samples were diluted with BN and dispersed on self-adhesive kapton tapes. Several tapes were stacked in order to obtain an absorption suited for XAFS measurements, which were carried out at both the Ba and the Eu L3-edges on beamline BL10 at the Dortmund Electron Accelerator DELTA using a channel-cut Si(111) monochromator and gas-filled ionization chambers as detectors. EXAFS studies at the Ba L3-edge for both samples, pure and Eu- doped BaAl2O4, gave evidence that the structure of the doped sample was very similar to that of pure BaAl2O4. The determined Ba-O and Ba-Al distances in these samples agree well with those obtained by the Rietveld structure refinement using the X-ray diffraction patterns for both samples. XANES measurements at the L3-edge of the Eu-doped sample clearly revealed the presence of solely Eu3+ ions, but the radial distribution function resulting from the EXAFS data was completely different from those for Eu2O3 and AlEuO3 reference phases. Impurity phases containing Eu were not detected in the doped sample, so the incorporation of the Eu3+ dopant on a regular lattice site of the BaAl2O4 host is very likely. We tested several possible lattice sites in the course of the Eu-EXAFS data fitting. Replacement of Ba2+ ions on the regular Ba2 site by Eu3+ ions, and including an additional oxygen into the lattice for charge compensation, gave the best results. EXAFS investigations have shown that Eu-doping in BaAl2O4 leads to substitution of Eu3+ ions for Ba2+ on the Ba2 site in the host structure, with charge compensation by interstitial oxygen in the vicinity of the related Ba2 site. The presence of any impurity phase could be excluded.

Zinc oxide is of interest in many applications as an important material with excellent combination of optical, electrical and microstructural properties. In order to optimize the properties of ZnO material for the highly technical or biomedical applications it is necessary to control its structure and morphology. This research is a follow up to our previous investigations [1, 2]. In a previous paper [2] we studied and compared the impact of a versatile family of ethanolamines (MEA and TEA) on the microstructural properties of the ZnO particles prepared in ethanol. In the present work zinc oxide particles were synthesized from zinc acetylacetonate in the presence of triethanolamine (TEA) and various alcoholic solvent, ethanol or octanol, at 170°C. The structural, optical and morphological characteristics of ZnO particles were monitored using X-ray powder diffraction (XRD), UV-Vis spectroscopy and field emission scanning electron microscopy (FE-SEM). The experimental findings are confirmed by means of DFT calculations. On the basis of both microstructural and theoretical studies, the nucleation and growth mechanism of ZnO nanoparticles is proposed. The nucleation and formation mechanism of ZnO nanoparticles was proposed considering the results obtained from a computational study of Gibbs free energies of ZnO−TEA molecular interactions (G*INT) in various solvent system. The calculations revealed different binding affinities which initiated the nucleation processes of ZnO into nanoparticles in the presence of alcohols of different size and polarity. The high chelating efficiency of TEA towards zinc with tetrahedral geometry is observed.

Suzbijanje i održavanje razine populacije biljno parazitskih nematoda ispod ekonomskoga praga štetnosti u korjenastom povrću zahtijeva integrirani pristup primjene agrotehničkih mjera i bioloških sredstava za zaštitu bilja jer kemijski nematocidi nisu dozvoljeni. Ciljevi istraživanja bili su utvrditi utjecaj plodoreda na populaciju Meloidogyne hapla (sjeverna nematoda korijenovih kvržica) i učinkovitost bionematocida NemakeyTM u suzbijanju Paratylenchus bukowinensis (igličaste nematode). Pokus je postavljen u ljetnom usjevu mrkve i peršina tijekom 2016. godine u Tvrđavici kod Osijeka. Populacija M. hapla smanjena je ispod ekonomskoga praga štetnosti uvođenjem kupusnjača u plodored koje su uzgajane na foliji. Prije sjetve mrkve i peršina, populacija P. bukowinensis kretala se od 155 do 470 nematoda u 100 mL tla, a vrhunac populacije od 217 do 920 nematoda u 100 mL tla utvrđen je pri vađenju. Bionematocid je bio slabo učinkovit u suzbijanju populacije igličastih nematoda u mrkvi. Utvrđena su ekonomski značajna oštećenja korijena mrkve (63 %) i peršina (43 %) od P. bukowinensis. Simptomi oštećenja mrkve i peršina od igličastih nematoda vrlo su slični simptomima napada nematoda korijenovih kvržica pri čemu je korijen biljke deformiran, ali nema kvržica. Koliko nam je poznato, do sada u RH nisu opisana u literaturi znatna oštećenja korjenastoga povrća od igličastih nematoda.

Barium aluminate, BaAl2O4, is a widely used material that has a high technological application in the field of electronics and optical communications. When doped/co-doped with transition metal cations or rare earth cations, it exhibits good luminescence properties [1]. Barium aluminate exists in two hexagonal phases with a reversible phase transition at 123 °C. At RT a ferroelectric phase in P63 space group is present, while at high temperature a paraelectric phase in P6322 space group is observed [2]. Powder BaAl2O4 samples doped with 0 and 1.76 at.% Cr in relation to Al were prepared by a hydrothermal method. Prepared samples were characterized by X-ray diffraction and synchrotron based X-ray absorption spectroscopy at the Cr K- and Ba L3-edge. XRD patterns showed that samples were nanocrystalline with a hexagonal crystal structure, space group P63. The doped sample contained a small amount of an impurity phase BaCrO4. Obtained Cr K-edge X-ray absorption near edge structure for the doped sample showed the presence of chromium in 6+ and 3+ oxidation states. Evidently, the Cr6+ ion was present in BaCrO4, while Cr3+ likely participated in the formation of the BaAl2O4:Cr phase. Extended X-ray absorption fine structure indicated on an unusual tetrahedral coordination of Cr3+ ions within the BaAl2O4 host phase. The structure of samples was refined by the Rietveld method [3]. Rietveld structure refinement showed that in doping Cr3+ ions substituted for Al3+ ions on Al1 tetrahedral sites of the BaAl2O4 crystal lattice. Lattice strain increased with Cr doping, while crystallite size simultaneously decreased. [1] Fukuda K., Iwata T., Orito T. J. Solid State Chem., 2005, 178, 3662. [2] Huang S.- Y., Von der Muell R., Ravez J., Chaminade J. P., Hagenmuller P., Couzi M. J. Solid State Chem., 1994, 109, 97. [3] Rietveld H. M. J. Appl. Crystallogr., 1969, 2, 65.

Barium aluminate BaAl2O4 is a photoabsorptive material of a considerable interest because of its potential application in the field of electronics and optical data processing (Kim et al., 2000). The electronic properties, as well as the photoabsorption performance of this material, can be tuned by addition of varying amounts of dopants/defects into the host structure resulting with more promising or advanced applications (Zhang et al., 2007). When doped/co-doped with transition metal cations or rare earth cations, it exhibits good luminescence performance. The europium doped BaAl2O4 is already used as a luminescent material with an emission in the red spectral range. Optical properties of this material have been widely investigated, but the crystal structure has not been examined. A mechanism of Eu incorporation into the BaAl2O4 host was only predicted on the basis of optical data (Peng & Hong, 2007). Barium aluminate exists in two hexagonal phases with a reversible phase transition at 123 °C (Huang et al., 1994). At RT a ferroelectric phase in P63 space group is present, while at high temperature it holds a P6322 space group assigned to the paraelectric phase. Structural studies of nanocrystalline powder sample of BaAl2O4 doped with 4.9 at% Eu3+ have been performed in order to examine the dependence of dopant incorporation mechanism on its oxidation state and doping level. Eu3+-doped BaAl2O4 phosphor sample was prepared by the hydrothermal route. Combined X-ray powder diffraction (XRPD), 151Eu Mössbauer measurements and synchrotron based X-ray absorption spectroscopy (XAS) were applied in order to examine the location and oxidation state of the europium dopant within the BaAl2O4 host matrix. Obtained XANES data at Eu L3-edge for the Eu- doped sample showed the presence of europium in 3+ oxidation state solely. An occupation of barium sites in the host BaAl2O4 lattice was clearly evidenced within a detailed analysis of the EXAFS data at the Eu L3-edge for the Eu-doped sample. The results suggested a mean Eu-O distance of about 2.40 Å and the coordination number of about 9, both indicating on Eu3+ substitution for Ba2+. Results of the Rietveld structure refinement analysis have indicated that Eu3+ dopant ions tend to occupy IX-coordinated Ba2 positions in hexagonal channels formed by corner-linked AlO4 tetrahedra of the BaAl2O4 host with a charge compensation by oxygen interstitials. References: Huang, S.-Y., Von der Muell, R., Ravez, J., Chaminade, J. P., Hagenmuller P. & Couzi M. J. (1994). Solid State Chem. 109, 97-105. Kim, C., Kwon, I., Park, C., Hwang, Y., Bae, H., Yu, B., Pyun, C. & Hong. G. (2000). J. Alloys Compd. 311, 33-39. Peng, M. & Hong, G. (2007). J. Lumin. 127, 735- 740. Zhang, L., Wang, L. & Zhu, Y. (2007). Adv. Funct. Mater. 17, 3781-3790.

Nanocrystalline sample of pure BaAl2O4 and one doped with 4.9 at% Eu in relation to barium were prepared by a hydrothermal method. Both samples were characterized by synchrotron based X-ray absorption spectroscopy. The EXAFS experiments at the Ba (5247 eV) and Eu (6977 eV) L3-edges have been performed in order to study the local environment of the Eu3+ dopant in detail. In the fitting procedure of EXAFS data at the Ba L3‐ edge, fits comprising two oxygen nearest neighbour shells with 6 oxygen atoms at about 2.7 Å and 3 oxygen atoms at about 2.95 Å, and 3 aluminium atoms at 3.4 Å and 3.5 Å fit the experimental data well for both the pure BaAl2O4 and BaAl2O4 doped with 4.9 at% Eu. The results revealed that the local structure of the pristine BaAl2O4 with 9 oxygen atoms in the first coordination sphere is retained during Eu‐doping. The obtained radial distribution functions for the Eu-doped sample obtained at the Ba L3-edge and at the Eu L3-edge are quite similar, which indicated that the short range order structure around Ba and Eu are very similar. The EXAFS data also showed that no substantial amounts of Eu2O3 and AlEuO3 were present in the Eu-doped sample.

Powder sample of pure BaAl2O4 and one doped with 4.9 at% Eu in relation to barium were prepared by a hydrothermal method and subsequent annealing at 1100 oC for 4h. Both samples were characterized by synchrotron based X-ray absorption spectroscopy. The transmission mode Eu and Ba L3- edge X-ray absorption experiments of the prepared samples were performed at DELTA beamline 10. The normalized Eu L3-edge XANES spectrum of Eu-doped sample was investigated in comparison to the spectra of Eu2O3 and AlEuO3 standards, and to the one of a glass sample containing both Eu2+ and Eu3+. The white line feature of the Eu-doped BaAl2O4 sample at 6983.4 eV clearly revealed the presence of trivalent europium in the doped sample. The Ba L3-edge XANES spectra of pure BaAl2O4 and Eu-doped BaAl2O4 samples showed that in the doped sample the host material remained in its original Ba2+-state. The presence of impurity phases such as Eu2O3, AlEuO3 and BaO in the prepared Eu-doped sample can be excluded on a basis of the obtained XANES spectra.

Spektroskopija rendgenske apsorpcije zasniva se na mjerenju linearnoga koeficijenta apsorpcije rendgenskoga zračenja za materijal u ovisnosti o energiji upadnoga rendgenskog zračenja. Spektar rendgenske apsorpcije sadrži dva područja, XANES i EXAFS, koja se međusobno razlikuju po rasponu energije upadnih rendgenskih zraka iznad apsorpcijskoga ruba promatranog atoma i mehanizmu raspršenja fotoelektrona koje emitira apsorbirajući atom. Često se spektroskopija u području XANES signala naziva metodom XANES, a spektroskopija u području EXAFS signala metodom EXAFS. U radu su opisani principi ovih metoda, njihove prednosti i ograničenja. One omogućuju formiranje strukturnoga modela dopiranoga materijala, što je važan korak u određivanju kristalne strukture dopiranih materijala koji se najčešće ne mogu prirediti u obliku jediničnoga kristala. Uz korištenje podataka rendgenske difrakcije u dopiranome polikristalnom materijalu i prikladnoga strukturnog modela, s pomoću Rietveldove metode može se utočniti kristalna struktura dopiranoga materijala. Prikazan je primjer uspješnog određivanja kristalne strukture barijevoga aluminata (BaAl2O4) dopiranoga s 4, 9 at.% Eu, provedenoga na taj način.

Barium aluminate, BaAl2O4, is a widely used material that has a high technological application in the field of electronics and optical communications.1 Specially, it has been extensively investigated as a promising host for long afterglow luminescent materials. Namely, when doped/co-doped with transition metal cations or rare earth cations, barium aluminate exhibits good luminescence properties.2, 3 Chromium is a low cost activator, and Cr3+-doped systems are already used in modern technologies, for example in production of solid-state lasers. Barium aluminate possesses a stuffed tridymite structure with barium cations incorporated into channels inside a three-dimensional network of corner sharing AlO4 tetrahedra.4 It exists in two hexagonal phases which are reversibile at 123 °C. At room temperature a ferroelectric phase in P63 space group is present, while at high temperature a paraelectric phase in P6322 space group is observed.5 Powder samples of barium aluminate doped with 0-12 at.% Cr were prepared by a hydrothermal method and additionally annealed at 900 °C for 4 h. Prepared samples were characterized by X-ray diffraction at RT, and their crystal structures were refined by the Rietveld method, simultaneously with the analysis of diffraction line broadening. The XRD patterns showed that all samples had the hexagonal stuffed trydimite structure in space group P63. The unit-cell parameters were precisely determined using silicon powder as an internal standard, and refined by the WPPF program.6 EPR and photoluminescence measurements indicated that chromium was present as Cr3+ ion in the doped samples. Rietveld refinement showed in which sites of BaAl2O4 structure Cr3+ dopant cations are incorporated. Line broadening analysis revealed that samples contained crystallites of ~30 nm in size. References: 1 C. Kim, I. Kwon, C. Park, Y. Hwang, H. Bae, B. Yu, C. Pyun, G. Hong, J. Alloys and Compd., 2000, 311, 33. 2 K. Fukuda, T. Iwata, T. Orito, J. Solid State Chem., 2005, 178, 3662. 3 Y. Lin, Z. Zhang, Z. Tang, J. Zhang, Z. Zheng, X. Lu, Mater. Chem. Phys., 2001, 70, 156. 4 A. Putnis, An Introduction to Mineral Sciences, Cambridge University Press, 1992. 5 S.-Y. Huang, R. Von der Muell, J. Ravez, J. P. Chaminade, P. Hagenmuller, M. Couzi, J. Solid State Chem., 1994, 109, 97. 6 H. Toraya, J. Appl. Crystallogr., 1986, 19, 440.

Rhodium and Rh-oxide based catalysts have found important applications, for example, in methanol or methane oxidations, decomposition of NOx gases to N2 and O2 etc. The catalytic chemistry of rhodium involves various redox reactions in which rhodium participate in different Rh-oxide forms. Reference literature demonstrates a high discrepancy between the number of publications about the catalytic activity of Rh-catalyst, on one hand, and, on the other, the redox chemistry of rhodium. For that reason, we have investigated the formation of α -Rh2O3 at the laboratory level. We focused on the formation of α -Rh2O3 from amorphous rhodium (hydrous)oxide obtained by precipitation from Rh(NO3)3 aqueous solution. The isolated precipitate was dried, then heated in air atmosphere up to 650°C. Samples were characterized by XRD, FT-IR, Raman and FE-SEM. The XRD of sample obtained at 400°C showed a broad and intensive peak which can be assigned to the amorphous nature of the sample. This peak is positioned at the Bragg angles corresponding to prominent peaks of α -Rh2O3. For the same sample, FT-IR spectrum showed one very broad and intensive peak centered at 544 cm-1, while the corresponding Raman spectrum showed broad peaks at 268, 411 and 556 cm-1. The Raman spectrum of the sample obtained at 650 cm-1 showed peaks at 276, 422, 568 and 610 cm-1, which can be attributed to α -Rh2O3 in line with XRD. FE-SEM showed a gradual increase in size (in the nanometer range) of rhodium oxide particles with an increase of temperature reaching 650°C.

Proučavan je utjecaj heksametilentetramina (urotropina) na procese ubrzane hidrolize iona Fe pri 90 °C iz otopina FeCl3, Fe(NO3)3 i NH4Fe(SO4)2. Fazni sastav, morfologija i mikrostrukturna svojstva produkata hidrolize istraživani su primjenom FT-IR i Mössbauerove spektroskopije, rentgenske difrakcije u prahu i transmisijske elektronske mikroskopije. Postupnim povećanjem pH do kojeg dolazi zbog homogene hidrolize urotropina pri 90 °C u kiselom mediju stvaraju se kontrolirani uvjeti hidrolize iona Fe . Kemijska i strukturna svojstva produkata hidrolize ovisili su o koncentracijama soli Fe(III) i urotropina, prirodi prisutnog aniona, te o vremenu taloženja. Uočeno je značajno smanjenje veličine čestica i kristalnosti b-FeOOH s porastom koncentracije urotropina tijekom hidrolize otopina FeCl3. Postupno povećanje pH vrijednosti do kojeg dolazi homogenom hidrolizom urotropina pri većim koncentracijama stvara uvjete za bržu i potpunu faznu transformaciju b-FeOOH u a-FeOOH i/ili a-Fe2O3 mehanizmom otapanje/ponovno taloženje. Tijekom hidrolize otopina Fe(NO3)3 u prisutnosti urotropina pri većim koncentracijama, udio faze a-FeOOH (maksimum dobiven oko neutralnog pH) značajno je povećan u odnosu na a-Fe2O3. Određeni su uvjeti taloženja a-FeOOH, a-Fe2O3 i NH4Fe3(OH)6(SO4)2 hidrolizom otopina NH4Fe(SO4)2 u prisutnosti urotropina. Specifičnom adsorpcijom iona SO na aktivnim površinama čestica a-FeOOH i a-Fe2O3 pri niskim pH vrijednostima inhibiran je njihov kristalni rast. Povećanjem pH vrijednosti do kojeg dolazi homogenom hidrolizom urotropina viših koncentracija smanjena je specifična adsorpcija sulfatnog aniona i favorizirana kristalizacija a-FeOOH i a-Fe2O3. Nije dokazano nastajanje švertmanita (Fe8O8(OH)6SO4) u pripravljenim uzorcima.

Precipitations of iron oxides from FeCl3 solutions in the presenceof urotropin at 90 oC were monitored using the Fourier transforminfrared spectroscopy, Mössbauer spectroscopy, X-ray diffractionand transmission electron microscopy. Urotropin was used as agenerator of OH– ions. The precipitation processes depended on theconcentrations of FeCl3 and urotropin and the time of aging. After1 day of aging the precipitation systems up to pH ≈ 2, the β-FeOOHphase was precipitated, while in the region of 5 < pH < 6 the mixturesof β-FeOOH, α-Fe2O3 and α-FeOOH were precipitated, andat pH > 6 the mixtures of α-Fe2O3 and α-FeOOH were observed.The -FeOOH phase precipitated at 2.16 < pH < 5.55 dissolved after7 days, yielding soluble iron for the α-FeOOH growth on account ofα-Fe2O3. At pH ≈ 1.5 and less, β-FeOOH was present as a singlephase up to 7 days of aging the precipitation systems. The mechanismsof iron oxide precipitation in dependence on pH were discussed.The size and morphology of oxide particles were stronglyinfluenced by experimental conditions of the precipitation processas shown by transmission electron microscopy.

Sakupljene su metode i standardi različitih zemalja kao i međunarodnih organizacija. Eksperimentalno je ispitano ekološko prirodno obojeno pamučno vlakno “paolo verde”. Dokazano je da je to vlakno vrlo tankih stijenki. U uvjetima nošenja posebno znojenja dolazi do promjene boje (alkalno znojenje intenzivira plavi ton, a kiselo žuti), te zapetljavanja i oslabljenja vlakana , pa se stoga vlakno može ocijeniti kao nepodesno za upotrebu.