Syntheses, optical and structural properties of luminescent powders based on rare earth ions doped gadolinium vandate

Glavni cilj istrаživаnjа u okviru ove doktorske disertаcije bio je da se rаzviju metode i optimizuju pаrаmetri sinteza koje su pogodne za dobijanje neorgаnskih luminescentnih prаhovа nа bаzi gаdolinijum-vаnаdаtа (GdVO4) dopirаnog jonimа retkih zemаljа i ispitaju strukturna, morfološka i optička svojstаvа dobijenih prаhovа. Poslednjih nekoliko godinа sve se više pаžnje posvećuje proučаvаnju fosfora koji su na bazi ortovаnаdаtа. Razvoj savremenih uređaja iz oblasti optoelektronike u velikoj meri zavisi od poboljšanih karakteristika luminescentnih materijala koji se koriste za njihovu izradu. Otkriveno je da su fosfori na bazi gadolinijum-vanadata dopiranog jonima retkih zemalja jedni od neorganskih luminescentnih materijala koji najviše obećavaju, čineći prilagodljiv izvor za brojne primene. U okviru ove doktorske disertacije luminescentni prahovi na bazi gadolinijum-vanadata, GdVO4, koji su dopirani jonima retkih zemalja, dobijeni su na sledeća tri načina: metodom reakcije u čvrstoj fazi, metodom hemijske precipitacije iz rastvora i metodom inverznih micela. Ovim metodama su sintetisani sledeći luminescentni prahovi: GdVO4:Tm3+, GdVO4:Tm3+/Yb3+, GdVO4:Er3+/Yb3+, GdVO4:Ho3+/Yb3+, GdVO4:Er3+/Yb3+/Li+, GdVO4:Ho3+/Yb3+/Li+, GdVO4:Tm3+/Er3+/Ho3+/Yb3+, ispitivan je njihov fazni sastav i struktura, kao i uticaj postupka sinteze na njihovu morfologiju. Takođe, u cilju proučavanja i poređenja optičkih svojstava (Stoksove i anti-Stoksove emisije) ovih sistema, detaljno je proučavano i prisustvo različitih kombinacija dopanata i ko-dopanata, kao i njihov stehiometrijski odnos. Za neke sisteme optička svojstva su merena u funkciji temperature u cilju određivanja potencijalne primene materijala u termometriji. Rendgeno-strukturna analiza svih dobijenih materijala pokazala je dobru kristaliničnost i dobijanje odgovarajuće, čiste faze sintetisanih prahova. Svi sistemi su dali čistu tetragonalnu fazu cirkonatnog tipa. Morfologija prahova snimana je na transmisionom i skenirajućem elektronskom mikroskopu u kombinaciji sa energetskom disperzionom analizom X-zraka. Utvrđeno je da se metodom reakcije u čvrstoj fazi dobijaju deformisane (nepravilne) sferne čestice prosečnog prečnika od 1,4 μm do 8,4 μm. Ko-dopiranjem ovih sistema Li+ jonima veličina kristalita raste do 90 nm za bilo koju koncentraciju Li+...The main goal of this PhD thesis was the optimization of parameters and development of the corresponding method for synthesis inorganic luminescent powders based on the rare earth ions doped gadolinium vanadate (GdVO4). The obtained materials were characterized and structural, morphological and optical properties were studied. In the last years, more attention was paid to the study of phosphors based on orthovanadate. The development of modern devices in the field of optoelectronics depends on the improved characteristics of the luminescent materials which have been used to make them. It has been found that the phosphors based on rare earth ions doped gadolinium-vanadate are inorganic luminescent materials that are the most promising, making a customizable resource for numerous applications. In this PhD thesis luminescent powders based on the rare earth ions doped gadolinium vanadate (GdVO4) materials were synthesized by three different techniques: solid state reaction, chemical precipitation from solution and inverse micelles method. The GdVO4: Tm3+, GdVO4: Tm3+/Yb3+, GdVO4: Er3+/Yb3+, GdVO4: Ho3+/Yb3+, GdVO4: Er3+/Yb3+/Li+, GdVO4: Ho3+/Yb3+/Li+ and GdVO4: Tm3+/Er3+/Ho3+/Yb3+ systems were synthesized and characterized. The phase compositions and structure, morphologies and optical properties were investigated. In order to compare the optical properties (Stokes and anti-Stokes emissions) of obtained systems, effects and presence of different combinations of dopants and co-dopants, as well as their stoichiometric ratio were studied in details. In order to determine the potential application the systems in the thermometry their optical properties were measured as a function of temperature. XRD analysis suggests that obtained materials crystallize in the tetragonal structure without any impurities and with good crystallinity. The morphologies of the powders were recorded by transmission and scanning electron microscopes in combination with an energy dispersive analysis of X-rays. It was found that deformed (irregular) spherical particles in the range from 1.4 to about 8.4 micrometers were obtained by solid state reaction. The calculated crystallite size for these particles is about 60 nm, while in Li+ co-doped systems this size increases up to 90 nm for any concentration of Li + ions..

Examination of the possibility of obtaining pyrite concentrate from the flotation tailings of the Lece mine

The Lece mine is characterized by the fact that it has gold and silver besides the main valuable components in the flotation concentrates of lead and zinc. Practically since the opening of the mine and flotation, research has been carried out with the aim of obtaining better technological indicators on all four valuable metals (lead, zinc, gold and silver), especially on gold. This paper represents a contribution to that research in order to increase the recovery of gold in flotation concentrates. Gold occurs in ore in several ways (native, with lead and zinc, with pyrite and quartz), which requires a complex technological scheme of gold valorization. Most of the gold is bound to galena and is valorized through lead concentrate. A smaller part of the gold is bound to zinc and is valorized through zinc concentrate. However, about 25% of the gold remains in tailings. Researchers ie. the authors of this paper tried to valorize part of the gold that is lost in the tailings by introducing a third pyrite concentrate with an increased gold content. The paper presents the results of laboratory experiments on the possibility of obtaining pyrite concentrate from the Lece tailings and a proposal for a technological scheme of the process

High resolution luminescence spectroscopy and thermoluminescence of different size LaPO4:Eu3+ nanoparticles

T. G. acknowledges the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001). K. S. and K. L. acknowledge the Latvian National Research Program IMIS2. The authors from Vinča Institute of Nuclear Sciences acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project No: 45020 and 172056 ).Nanoparticles (5 nm) and nanorods (2 nm × 15 nm and 4 nm × 20 nm) of monoclinic monazite LaPO4:Eu3+ were prepared by reverse micelle and co-precipitation techniques. Effects of the particle size and surface defects on the intensity of luminescence and the emission spectrum shapes were analyzed by high resolution spectroscopy under laser (266 nm) and X-rays excitation. All synthesized LaPO4:Eu3+ samples showed similar spectral features with characteristic Eu3+ ions emission bands: 5D0→7F0 centered at 578.4 nm, magnetic-dipole transition 5D0→7F1 at 588–595 nm, electric-dipole transition 5D0→7F2 at 611.5–620.5 nm, 5D0→7F3 at (648–652 nm) and 5D0→7F4 at (684–702.5 nm), with the most dominant electric-dipole 5D0→7F2 transition. Additionally, the thermally stimulated luminescence was studied for the most dominant peak at 611.5 nm. It was shown that the Eu3+ doping creates traps in all samples. Two prominent and well resolved glow peaks at 58.7 K and 172.3 K were detected for 5 nm nanoparticles, while low-intensity glow-peaks at 212.1 K and 212.2 K were observed in the X-rays irradiated nanorods. Displayed glows could be attributed to free and bound electrons and holes or to the recombination of electrons of ionized oxygen vacancies with photogenerated holes. To obtain information about the processes and specific defect type it is necessary to carry out additional analysis for all synthesized samples. The glow curves were analyzed and trap parameters were estimated and discussed throughout the paper.ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001); IMIS2; Ministry of Education, Science and Technological Development of the Republic of Serbia (Project No: 45020 and 172056 ); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Particle size effects on the structure and emission of Eu3+:LaPO4 and EuPO4 phosphors

The authors acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Projects nos. 45020 and 172056). T.G acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001).This paper provides the detailed study of (nano)particle's size effect on structural and luminescent properties of LaPO4:Eu3+ synthesized by four different methods: high temperature solid-state, co-precipitation, reverse micelle and colloidal. These methods delivered monoclinic monazite-phase submicron particles (> 100 nm), 4 × 20 nm nanorods and 5 nm spheres (depending on the annealing temperature), 2 × 15 nm nanorods, and ultra-small spheres (2 nm), respectively. The analysis of emission intensity dependence on Eu3+ concentration showed that quenching concentration increases with a decrease of the particle size. The critical distance for energy transfer between Eu3+ ions is found to be 18.2 Å, and the dipole-dipole interaction is the dominant mechanism responsible for the concentration quenching of emission. With the increase in Eu3+ concentration, the unit-cell parameter slightly increases to accommodate larger Eu3+ ions at sites of smaller La3+ ions. Photoluminescent emission spectra presented four characteristic bands in the red spectral region: at 592 nm (5D0→7F1), at 612 nm (5D0→7F2), at 652 nm (5D0→7F3) and at 684 nm (5D0→7F4), while in small colloidal nanoparticles additional emission bands from host defects appear at shorter wavelengths. Intensities of f-f electronic transitions change with particles size due to small changes in symmetry around europium sites, while emission bandwidths increase with the reduction of particle size due to increased structural disorder. Judd-Ofelt analysis showed that internal quantum yield of Eu3+ emission is strongly influenced by particle's morphology.Ministry of Education, Science and Technological Development of the Republic of Serbia (Projects nos. 45020 and 172056); ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Multifunctional Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles synthesized by reverse micelle method

Synthesis of Eu3+- and Er3+/Yb3+-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with similar to 4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu3+-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er3+/Yb3+-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from H-2(11/2)- GT I-2(15/2) and S-4(3/2)- GT I-4(15/2) transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K-1, which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers

Up-conversion luminescence of GdVO4:Nd3+/Er3+ and GdVO4:Nd3+/Ho3+ T phosphors under 808 nm excitation

All authors acknowledge to the COST Action CM1403: The European upconversion network - from the design of photon-upconverting nanomaterials to biomedical applications (2014–2018). The authors from the University of Belgrade acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project Nos. 45020 and 172056 ). K. S. acknowledges the Latvian National Research Program IMIS2 (Grant No. 302/2012 ). T. G. acknowledges the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 ( 1.1.1.2/16/I/001 ).In recent years, there exists a tendency in research of up-conversion materials to shift excitation from 980 nm to shorter wavelengths. Here, in order to produce up-conversion luminescence emission of GdVO4-based materials under 808 nm excitation, polycrystalline powders of GdVO4:Er3+/Nd3+ and GdVO4:Ho3+/Nd3+ were successfully prepared by a high-temperature solid-state reaction technique. The prepared powders were highly crystalline with a single-phase zircon-type GdVO4 structure and consisted of micrometer-sized irregular spherical particles (2–6 μm in diameter). In all studied samples, visible up-conversion luminescence was successfully achieved under 808 nm illumination. Near-infrared pumping produced emission bands in the green, yellow-orange and green regions of the visible spectrum. The bands in the green and red regions of GdVO4: Er3+/Nd3+ as well as GdVO4:Ho3+/Nd3+ were, respectively, characteristic of Er3+ and Ho3+ ions. The dominant band originating from the 4G7/2 → 4I11/2 transition in Nd3+ ions was observed around 597 nm in all samples.COST Action CM1403 (2014–2018); Ministry of Education, Science and Technological Development of the Republic of Serbia (Project Nos. 45020 and 172056 ); Latvian National Research Program IMIS2 (Grant No. 302/2012 ); ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 ( 1.1.1.2/16/I/001 ); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Supplementary data for the article: Pavlović, T.; Dimkić, I.; Andrić, S.; Milojković-Opsenica, D.; Stanković, S.; Janaćković, P.; Gavrilović, M.; Ristivojević, P. Linden Tea from Serbia – an Insight into the Phenolic Profile, Radical Scavenging and Antimicrobial Activities. Industrial Crops and Products 2020, 154, 112639. https://doi.org/10.1016/j.indcrop.2020.112639

Supplementary material for: [https://doi.org/10.1016/j.indcrop.2020.112639]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/4040

The Effect of Shelter on Oxidative Stress and Aggressive Behavior in Crested Newt Larvae (Triturus spp.)

Shelters are important for animal survival. Provision of adequate hiding places allow animals to express their natural sheltering behavior and it can have different positive effects on cortisol levels, physiological processes and mental performance. Although the absence of a refuge activates some stress response, its effect on oxidative stress has not been adequately examined. This study investigated whether the presence/absence of a shelter modifies the oxidative status (the antioxidant system and oxidative damage) and aggressive behavior of crested newt larvae (Triturus macedonicus and its hybrid with T. ivanbureschi). Our results show that individuals reared with shelters had lower values of the tested antioxidant parameters (catalase, glutathione peroxidase, glutathione S-transferase and glutathione), indicating a lower production of reactive species than individuals reared without shelter. The same pattern was observed in both T. macedonicus and its hybrid. Contrary to the activation of some physiological pathways, shelter availability did not significantly affect the rate of intraspecific aggressive behavior. The physiological benefits of shelter use can be manifested as a lower requirement for investment in the energy necessary for the maintenance of the upregulated antioxidant defenses, activation of repair systems and synthesis of endogenous antioxidants. This study highlights the importance of shelter provision, which may be valuable in habitat restoration and animal conservation studies

Diatom and bacteria assemblages in saline habitats (Vojvodina, Serbia)

Soda pans are restricted to the Carpathian Basin and differ from other similar saline waters mainly due to the dominant presence of Na+, HCO3–, and CO32– ions. These shallow and temporary aquatic habitats are inhabited by a number of species that can thrive in extreme environments. In Serbia, saline habitats are rare, endangered, and most common in the territory of Vojvodina. One of the most investigated group of organisms in soda pans is diatoms. Due to ecophysiological plasticity, they can survive and tolerate extreme environmental conditions which gives them a competitive advantage over other algae. Quite the opposite, prokaryotes in saline habitats are not sufficiently studied and data are scarce. Thus, samples from 6 soda pans were collected in March 2021 aiming to determine diatom (microscopic and molecular analysis, 18S rRNA gene) and bacterial community (16S rRNA gene). Most of the recorded diatom taxa are neutrophilic to alkalibiontic, mostly halophilic, and eutrophic species. The species richness diversity index was the highest in Velika Slatina and Slatina, while it was lowest in Mala Rusanda. The genus Nitzschia was one of the most represented and numerous according to morphological analyses (24 taxa, 4 dominant), while molecular analyses indicate 11 different species with low abundances and mainly with unassigned sequences. The biggest discrepancy in these two approaches was observed in Mala Rusanda and Okanj bara. Metabarcoding analysis indicated Halamphora veneta as the dominant taxa, while morphological analyses have shown a predominance of Nitzschia supralitorea and Surirella brebissonii in Mala Rusanda, and N. austriaca in Okanj bara. Estimated richness and alpha diversity indices showed the highest bacterial diversity in Velika Rusanda and Okanj bara, while the lowest richness was in Mala Rusanda. Representatives of the phylum Proteobacteria were detected predominantly in Pečena Slatina, Bacteroidota in Velika Slatina, Actinobacteria in Okanj bara, while representatives of Firmicutes were most abundant in Slatina, Velika Rusanda, and Mala Rusanda. At the genus level, 515 different genera were detected, and some of the most dominant were: Luteolibacter, unidentified genera from the family Bacillaceae, Actibacter, etc. Further investigations will be required to overcome the problem of the reference barcoding library incompleteness for halophilic and alkaliphilic species in these habitats and try to reveal the unknown relationship between diatoms and bacteria

Delovanje meda na nivo malondialdehida u plazmi izloženoj terapijskoj dozi zračenja

Malondialdehyde (MDA) is the end product of lipid peroxidation and biomarker of free radicals. The aim of this study is to investigate the effect of honey on concentrations of MDA in plasma exposed to a therapeutic dose of radiation. In this experiment animals were divided into two groups: in CONTROL group the animals were given distilled water orally for 28 days, and HONEY group consisted of animals given 1,5 ml/kg honey orally for 28 days. Blood samples of both groups were collected from a rat's tail. All blood samples were exposed to radiation of 2 Gy. Malondialdehyde concentration in plasma was determined using spectrophotometric method. Honey treatment in the blood plasma exposed to a therapeutic dose of 2 Gy significantly decreased MDA level by 30 % compared with control group. The present results indicated that honey had an effect on the levels of MDA in plasma exposed to radiation.Malondialdehid (MDA) je krajnji proizvod peroksidacije lipida i biomarker slobodnih radikala. Cilj ovog istraživanja je bio da se ispita uticaj meda na koncentraciju MDA u krvnoj plazmi izloženoj terapijskoj dozi zračenja. U ovom eksperimentu životinje su podeljene u dve grupe: u kontrolnoj grupi životinje su dobijale destilovanu vodu oralno tokom 28 dana, a drugu grupu činile su životinje koje su tokom 28 dana dobijale oralno 1.5 ml/kg meda. Uzorci krvi obe grupe su sakupljeni iz repa pacova. Svi uzorci krvi bili su izloženi zračenju od 2 Gy. Koncentracija MDA u plazmi određena je spektrofotometrijskom metodom. Tretman medom u krvnoj plazmi izložen terapijskoj dozi od 2 Gy značajno je smanjio nivo MDA (30 %) u poređenju sa kontrolnom grupom.XXXII Simpozijum Društva za zaštitu od zračenja Srbije i Crne Gore, 4-6. oktobar 2023; Budva, Crna GoraProceedings: [https://vinar.vin.bg.ac.rs/handle/123456789/11602