Synthesis of Cerium-Activated Yttrium Aluminate Based Fine Phosphors by an Aerosol Route

Polycrystalline fine powders of yttrium aluminate doped with Ce³⁺ were synthesised by spray pyrolysis of a polymeric pre-cursor, which was obtained by dissolving the corresponding nitrates in a solution of ethylenediaminetetraacetic acid (EDTA) in ethylene glycol (EG). Aerosol decomposition was performed at 550 °C followed by an additional thermal treat-ment (900–1100 °C). The yield of either a single yttrium alu-minium perovskite (YAP) phase or a single yttrium alumin-ium garnet (YAG) phase was investigated as a function of the predefined yttrium/aluminium ratio, the cerium doping concentration, the processing temperature, and the thermal-treatment regime, which included the variation of the heat-ing and cooling rates (dT/dt), the residence time (τ), and the atmosphere. Changes in the composition and structure of the precursor during thermal decomposition were investigated by thermogravimetric and differential thermal analysis (TGA/DTA) and FTIR spectroscopy. The particle morphology and structure were analysed by a combination of scanning electron microscopy and energy-dispersive X-ray spec-troscopy (SEM/EDS) and by highresolution transmission electron microscopy (HR-TEM). The structural refinement was based on the phase identification performed by X-ray powder diffraction (XRPD). The emission spectra were re-corded within the range 325–800 nm by applying excitation wavelengths of 297 (YAP) and 450 nm (YAG). The employed synthesis conditions assured the formation of spherical, non-agglomerated particles with well-developed surfaces and diameters between 200 and 800 nm. For a predefined Y/Al ratio of 1:1, lower processing temperatures combined with longer heat treatments under stationary conditions resulted in a multiphase system, composed of YAP, YAG, and mono-clinic yttrium aluminate (YAM) phases. However, a short heat treatment with a high heating rate (200 °C/min) at higher temperatures results in the formation of a kinetically favoured pure YAP hexagonal phase. On the other hand, for a predefined Y/Al ratio of 3:5, the generation of a thermody-namically favoured pure YAG phase has been confirmed, re-gardless of the applied heat-treatment conditions. Although incomplete, Ce³⁺ introduction into the host matrix has been detected by XRPD and luminescence measurements.The authors gratefully acknowledge the Ministry of Science and Education of the Republic of Serbia (Project No 172035), the University Carlos III (Madrid, Spain), and the Santander Bank (Chairs of Excellence Program for the academic year 2010–2011) for financial suppor

TEM-STEM study of europium doped gadolinium oxide nanoparticles synthesized by spray pyrolysis

Proocedings of: Fourth Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials. Kurashiki, Japan, 02-05 September 2012.Scanning-Transmission and Transmission Electron Microscopy techniques (STEM and TEM) have been applied to the characterization of nanostructured gadolinium oxides doped with europium synthesized by spray pyrolysis. The High Angle Annular Dark Field (HAADF) &- Scanning Transmission Electron Micros-copy (STEM) tools have been used to perform a tomographic study to identify morphological character-istics of nanostructured particles, and to differentiate them according to the heat treatments to which these have been subjected. With these techniques it has been possible to confirm the hollowness and por-ous nature of samples subjected to low temperature annealing (900 ºC). Moreover, the beginning of the densification and sintering processes in samples subjected to thermal treatment at higher temperature (1100 ºC) have been evaluated. Chemical analysis by electron energy loss spectroscopy (EELS) and X ray energy dispersive spectroscopy (EDS) carried out in STEM mode have allowed to confirm the high uni-formity and the expected chemical composition. The high resolution tools either allowed to confirm the presence of a cubic (Ia3 symmetry) and the monoclinic (c2/m symmetry) phases in the nanostructured particles.This work has been supported by the Advanced Structural Materials Program- ESTRUMAT (S2009/MAT-1585) and MAT2010-19837-C06-05. Thanks are extended to NanoPort (FEI)- Eindhoven, especially to Eng. L. Fernando Mendoza and to the Ministry of Science and Technology of Serbia (Project #142010).Publicad

Influence of nanoscale defects on the improvement of photocatalytic activity of Ag/ZnO

This study presents the advances in the field of ZnO/Ag catalysts from the synthesis of hierarchical ZnO nanowires (NWs) decorated with Ag nanoparticles, prepared by a facile solvothermal method at 120°C. It evaluates the photocatalytic efficiency from studying the time reaction of Ag/Zn concentration ratio and the presence of cetyltrimethylammonium bromide (CTAB) as an organic dispersant. X-ray diffraction, scanning electron microscopy, and analytical/high-resolution transmission electron microscopy results confirmed the presence of homogeneous cylindrical ZnO nanowires and quasi-spherical Ag crystals. ZnO NWs exhibited hexagonal wurtzite structure and cubic FCC symmetry in Ag nanoparticles (NPS). Two types of nanostructures, including homogeneous cylindrical ZnO NWs in the absence of Ag and simultaneous presence of ZnO NWs and Ag NPs, formed depending on experimental conditions. The photocatalytic activity was evaluated by studying methylene blue (MB) degradation time under UV light excitation. Diffuse reflectance UV–Vis spectrophotometry (UV–Vis DRS) allowed identifying the ZnO absorption band at ~393 nm. Crystal size varied depending on the reaction time and the addition of CTAB. Synthesis time increased bandgap values, getting better photocatalytic performance in samples synthesized in intermediate times (6 h), higher Ag+/Zn2+ molar ratio (0.2/1.0), and CTAB. According to HRTEM observations, the presence of silver nanocrystals with high content of defects (twinning, stacking faults) could play an essential role in the photocatalytic response. In this context, the specific synthesis conditions of Ag/ZnO might be more appropriate for their use in organic dyes degradation in water and the potential use in protective treatments against materials biodeterioration processes.This work has been supported by the Innovation and Education Ministry (ref. MAT2013-47460-C5-5-P and MAT2016-80875-C3-3-R), the Autonomous Region Program of Madrid (ref. S2018/NMT-4411 and S2013/MIT-2862), the Geomateriales 2 program (S2013/MIT_2914), the TOP Heritage (P2018/NMT-4372) of the Community of Madrid, the Innovation and Education Ministry (MAT201347460-C5-5-P) and the Ministry of Education, Science and Technological Development of Serbia (projects No. 172035 and 45020). Besides, we would like to thank the Master of “Materials Science” of Carlos III University (Spain) for providing financial and laboratory equipment support

Synthesis and morpho-structural characterization of nanostructured magnesium hydroxide obtained by a hydrothermal method

Controlled magnesium hydroxide particles were successfully synthesized via a simple hydrothermal method. The influence of temperature and reaction time on the hydrothermal synthesis of Mg(OH)(2) was studied. The results provide new parameters to control the morphologies, particle sizes, agglomeration level and crystallographic structures of the brucite nanosized. The physic chemical properties of synthesized Mg(OH)(2) nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), high resolution transmission electron microscopy (HR-TEM) and thermogravimetry/differential scanning calorimetry (TG/DSC). It has been shown that the prolongation of reaction time improves the crystalline degree of magnesium hydroxide particles. It was also possible to detect a relevant increase in the degree of crystallinity and a faster crystal growth with defined hexagonal morphologies in the samples obtained at higher temperature. Our results show that this simple hydrothermal route is highly interesting for the large scale production of these nanomaterials. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.This study has been supported by the Geomaterials Programme (S2009/MAT-1629) and the ESTRUMAT Programme (S2009/MAT-1585) and it has been carried out in the Department of Materials Science and Engineering and Chemical Engineering of the University Carlos III of Madrid, Spain. The authors are grateful to the National Center for Electron Microscopy (CNME) for its support with TEM

Atomic scale study of the dehydration/structural transformation in micro and nanostructured brucite (Mg(OH)(2)) particles: Influence of the hydrothermal synthesis conditions

Micro and nanostructured brucite (Mg(OH2)) particles synthesized by hydrothermal method from solutions with high content of hydrazine (0.14 M) and nitrate (0.24 g) were compared with samples obtained from low hydrazine content (0.0002 M) and nitrate (0.12 g). The samples were heated at 180 degrees C for 4 h, 6 h and 12 h. XRD, TEM-HRTEM, SAED and image analysis techniques were used for the morphological and structural characterization. The effect of electron beam irradiation on the brucite dehydration was observed in atomic resolution images at 300 kV. Hexagonal crystals show differences in crystallinity, strains and kinetic of reaction. High hydrazine/nitrate samples have slightly larger crystals with better crystallinity, showing a strong preferential orientation. Rietveld refinements show how unit cell parameters are bigger in samples obtained with higher hydrazine/nitrate content, confirming also the preferential orientation along the 0001 plane. Differences in the dehydration process show the rapid formation of a porous surface, the amorphised cortex or the presence of highly oriented strains in samples prepared from higher hydrazine/nitrate content. Conversely, crystals slightly smaller with randomly scattered defect surfaces showing the Mg(OH)(2)/MgO interphase in samples prepared with low hydrazine/nitrate content. Significant differences in the kinetic of reaction indicate how the dehydration process is faster in samples prepared with high hydrazine/nitrate content. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.This present research was funded by the Community of Madrid under the GEOMATERIALES II project (S2013/MIT-2914), by the Complutense University of Madrid’s Research Group: “The alteration and conservation of stone heritage” (921349), the Autonomous Region Program of Madrid, MULTIMAT-CHALLENGE (ref. S2013/MIT‐2862), the Innovation and Education Ministry ref. (MAT2013-47460-C5-5-P), the Mat201019837/C06-05 and the Ministry of Education, Science and Technological Development of Serbia (OI 1612046) projects. The authors are indebted to the Petrophysical Laboratory IGEO, affiliated with the Moncloa Campus of International Excellence CEI-09-009(UCM-UPM), the Heritage Laboratory Network in Science and Technology for Heritage Conservation (RedLabPat,) and the Materials Science Department (Carlos III University of Madrid)

STRUCTURE OF RELATIONS BETWEEN THE FREQUENCY OF MICRONUCLEI IN PERIPHERAL BLOOD LYMPHOCYTES AND AGE, GENDER, SMOKING HABITS AND SOCIO-DEMOGRAPHIC FACTORS IN SOUTH-EAST REGION OF SERBIA

Frequency of micronuclei (MN) in peripheral blood lymphocytes is a measure of genotoxicity and spontaneous chromosomal instability with many modifying factors. The aim of this work was to examine the relation between results of micronucleus test and set of socio-demographic parameters in healthy population in south-east Serbia using structure equation approach. Cytokinesis–block (CB) technique was used for analysis of MN frequency in peripheral blood lymphocytes on 133 healthy volunteers of various ages. Socio-demographic data was collected through a questionnaire. The mean frequency of MN gradually rose with age from 0.56±0.71 in new-borns to 5.48 ±3.65 in the 61-80 years age group (AG), with a decrease in the 81-92 years AG. MN frequency was positively correlated with age, altitude of birth place, altitude of place of residence, nuclear buds and nucleoplasmatic bridges, and negatively with education level and smoking habits. Linear structural model revealed age to be related to all of the examined variables, and indicates probable existence of another factor, independent of age, influencing all of these except nuclear buds. It can be concluded that the frequency of micronuclei is influenced by age and factor/s resembling socioeconomic status or lifestyle and this influence is independent of age

IL28B Genetic Variations in Patients with Recurrent Herpes Simplex Keratitis

Background and objectives: Recurrent herpes simplex keratitis (HSK) is the most common cause of corneal blindness in the developed world. A relationship between host gene polymorphisms and the recurrence of herpes simplex virus (HSV) infection has previously been proposed. Thus, the aim of this study was to investigate a potential association between the IL28B host genotype and recurrent HSK. Materials and Methods: Eighty patients older than 18 years of age of both genders with a history of recurrent herpes simplex labialis (HSL) were considered for inclusion. Seventy-five of these patients were found to be seropositive for HSV-1 and were subsequently enrolled in the study. Twenty-four of the enrolled patients also had a history of recurrent HSK associated with severe corneal scarring and visual acuity deterioration. Total DNA was isolated from whole blood samples. A single-nucleotide polymorphism (SNP) rs12979860 near the IL28B gene on chromosome 19 was genotyped. Results: A significant association was observed between recurrent HSK and two SNPs of the IL28B genotype (CCrs12979860 and CTrs12979860, p < 0.01). The variation CCrs12979860 showed a significantly greater association with HSK (16 out of 26 patients) compared with CTrs12979860 (8 out of 34 patients). Conclusion: Seropositive individuals with a history of recurrent HSK are likely to have the CC IL28B genotype. This genotype may be related to incomplete control of the infection and more frequent periodical viral shedding along the first nerve branch of the trigeminal ganglion, which clinically manifests as recurrent herpes keratitis. The clinical manifestation of recurrent HSV-1 infection seems to be influenced by polymorphism of the IL28B genotype

Structural, morphological and luminescence properties of nanocrystalline up-converting Y1.89Yb0.1Er0.01O3 phosphor particles synthesized through aerosol route

Nanocrystalline up-converting Y₂ O₃Yb³⁺ Er³⁺ phosphor particles were processed in a dispersed system-aerosol, generated ultrasonically at 1.3 MHz from common nitrate precursor solution having fixed ytterbium-to-erbium concentration ratio. The appropriate process parameters: residence time 21 s, carrier gas (air) flow rate 1.6 dm3/min, synthesis temperature 900 °C, led to the formation of un-agglomerated spherical nanostructured secondary particles, having mean particle size of approx 450 nm, composed of primary nanoscaled (20 nm) subunits. In order to reach targeting phase crystallinity, the as-prepared particles were additionally annealed at 1100 °C in air for 12, 24 and 48 h, respectively. Particle structure, morphology and purity were analyzed by X-ray powder diffraction (XRPD), scanning electron microscopy (FESEM/SEM), analytical and high resolution transmission electron microscopy (TEM/HRTEM) in combination with energy dispersive X-ray analysis and Fourier Transform Infrared Spectroscopy (FTIR). All samples crystallized in a cubic bixbyte-structure, space group Ia-3. The crystallite size changed with annealing time from 30 nm in as-prepared sample to 135 nm in sample annealed for 48 h, respectively. Emission spectra were assigned to the following trivalent erbium f–f electronic transitions: ²H₉/₂ → ⁴I₁₅/₂ (blue: 407–420 nm), (²H₁₁/₂̦ ⁴S₃/₂) → ⁴I₁₅/₂ (green: 510–590 nm), and ⁴F₉/₂ → ⁴I₁₅/₂ (red: 640–720 nm). The significant improvement of the emission decay times were observed after thermal treatment and this effect is correlated further with the structural and morphological particles characteristics. For the anneal-ing time of 12 h a quite high emission decay times were achieved (blue: 0.14 ms, green: 0.32 ms and red: 0.39 ms).This research is financially supported through the Project #172035 of the Ministry of Science and Education of the Republic of Serbia. OM especially acknowledge the University Carlos III, Madrid, Spain-Santander Bank Chairs of Excellence program and JSPS 2011/2012 fellowship, Japan.Publicad

Effects of citric ion on hexagonal NaYF4: Yb/Er phase formation during solvothermal synthesis

Up-converting nanoparticles (UCNPs) which have ability to emit a visible light upon excitation with NIR photons are with wide applications in optoelectronic devices, forensic, biomedicine and security. The synthesis of the most efficient hexagonal β- NaYF4:Yb/Er phase in shape of uniformly sized spherical nanoparticles is usually performed through thermal decomposition of complex organic precursor in high-boiling organic solvents, which rise deep concerns regarding their potential citotoxicity. In this work, citric acid and Na-citrate are used for the stabilization of hexagonal polymorph during solvothermal processing of NaYF4:Yb/Er phase from common inorganic precursor (rare earth nitrate salts). Additionally, effect of precipitation agent, i.e. fluorine source (NaF, NH4F and NH4HF2) on the final particle morphology is deduced based on comprehensive scanning and transmission electron microscopy analyses. Detailed refinement of the X-ray powder diffraction data (XRPD) revealed simultaneous nucleation of a cubic and hexagonal phase during solvothermal reaction. The use of citric acid resulted in formation of micro- and nano- spherical particles of a hexagonal and cubic NaYF4:Yb/Er phase, respectively, while Na-citrate provoked nucleation of well crystallized hexagonal crystals of β-NaYF4:Yb/Er phase. Size of the crystallites is determined by the choice of the precipitant, and is smallest in the case when NH4F is used. All synthesized powders emit bright and intense green light due to the intensification of the 2H11/2,4S3/2 →4I15/2 electronic transitions upon the excitation by the infrared light (λ=978 nm)

Thelohanellus hovorkai-kod ženki i mlađi šarana

Telohaneloza je obolenje šaranskih riba koje se klinički uočava na perajima i krljuštima (Thelohanellus nikolskii) i svim drugim tkivima a naročito u centralnom nervnom sistemu (Thelohanellus hovorkai). Na prisustvo parazita Thelohanellus nikolskii pregledani su mladunci i matične ribe šarana (Cyprinus carpio) koji potiču sa ribnjaka u Srbiji. Prisustvo ovog parazita zabeleženo je kod mladunaca šarana starijih od 90 dana i kod matica šarana. Intenzitet infekcije razlikovao se u zavisnosti od ribnjaka na kojima je obolenje utvrđeno. Ustanovljeno je da su najintenzivnije infekcije kao i najveći broj inficiranih jedinki poticali sa ribnjaka gde su gajeni sa starijim kategorijama, jezera sa prirodnim mrestom, i objekata koji su služili kao skladištbeni prostor tokom zimskog perioda. Spore Thelohanellus hovorkai nađene su na škrgama, koži, muskulaturi, jetri, slezini, bubrezima, crevu, žučnom i vazdušnom mehuru, kičmenoj moždini i mozgu gde je bio prisutan najveći broj parazita. Spore su bile obavijene mukofilnim omotačem. Prosečne veličine spora T. hovorkai iznosile su: dužina spore 20-21µm, širina spore 14µm, dužina polarne kapsule 12.5-14µm, širina polarne kapsule 11.5-12.5µm, dužina spore sa sluzavim omotačem 22.5-25µm i širina spore sa sluzavim omotačem 14.5-17.5µm. Dijagnostika ovog obolenja vezana je za detekciju spora čija se veličina razlikuje u opisima istraživača kod riba iz otvorenih voda i šaranskih riba gajenih u akvakulturi. Da bi utvrdili da li je u pitanju možda druga vrsta ili podvrsta parazita to možemo učiniti primenom molekularnih tehnika koje pokušavamo da uvedemo u dijagnostiku. Obolenje se manifestuje poremećajima u centralnom nervnom sistemu, malokrvnosti i slabijem napredovanju mladunaca a naročito kada se dijagnostikuje veći broj spora u tkivima riba. Specifične terapijske mere nisu poznate ali opšte preventivne mere vezane za pripremu objekata za gajenje mladunaca šarana daju povoljne rezultate. Predmet istraživanja je bio detekcija miksosporidia kod šarana. U ovom radu, opisana je telohaneloza kod jednogodišnje mlađi i matičnih jedinki šarana uzrokovana sa parazitom Thelohanellus hovorkai. Istraživanja su sprovedena u severnom delu Srbije (Vojvodina) na 15 ribnjaka u razdoblju 2007-2010. Svi ispitivani ribnjaci snabdevaju se vodom iz mreže kanala, reka Tisa, Tamiš, i Dunava, i bunara. Metode koje su korištene su klinička posmatranja, svetlosna mikroskopija i klasična patohistologija s H & E bojenjem. Ono što se pokazalo veoma bitno jeste da prirodni mrest riba nije pogodan za intenzivniju proizvodnju šarana i da se preporučuje gajenje mladunaca samo ako su iste starosne grupe. Tokom zime, ribnjačko tlo treba isušiti i izamrznuti a nakon 3-5 godina eksploatacije, površinski sloj tla od ribnjaka treba ukloniti. Tokom pripreme ribnjaka preporučuje se korišćenje rotacionih plugova a za dezinfekciju ribnjaka treba koristiti gašeni (1000 kg / ha) ili negašeni kreč (2000 kg / ha)