Hydrothermal synthesis of optically active rare earth fluorides

Hydrothermal method has great interest in recent years for synthesis of nano- and micro- crystals of upconverting rare earth (RE) fluorides, with controlled morphology and high purity, under high temperatures and pressures. Some surfactants (ethylenediaminetetraacetic acid (EDTA), polyvinylpyrrolidone (PVP), oleic acid (OA)) along with different type of solvents are added in order to control size, morphology and crystalline phases of particles. In this work Yb3+/Er3+ co-doped YF3 and NaYF4 fine powders were synthesized using the hydro/solvo thermal method in the present of EDTA as a complexing agent. Effect of the processing parameters on the particles crystal structure, morphology and optical properties were estimated on the basis of X-ray diffractometry (XRPD), scanning electron microscopy (SEM) and photoluminescence measurement. It was shown that in terms of increased concentration of RE ions in aqueous solvent media the hexagonal β-NaYF4:Yb3+/Er3+ phase with the most efficient green emission were synthesized. On the other side, the occurrence of cubic α-NaYF4:Yb3+/Er3+ and orthorhombic YF3:Yb3+/Er3+ were observed with a decrease of the RE ions when ethanol is used as a solvent. All of the samples provide intense green emission after been excited with infrared light (λ = 978 nm), which is assigned to the Er3+ (2H11/2, 4S3/2) → 4I15/2 electronic transitions

Памћење живи кроз комуникацију : Представљен зборник докумената "Извештаји и наредбе Недићеве Владе народног спаса за Округ пожаревачки 1941-1942. година"

Поводом обележавања Дана Историјског архива Пожаревац и 75 година од победе над фашизмом, у свечаној сали Скупштине града Пожаревца представљен је Зборник докумената ИАП и Војног архива Министарства одбране Републике Србије „Извештаји и наредбе Недићеве „Владе народног спаса“ за Округ пожаревачки 1941 – 1942. година“ – том 1, приређивача др Јасмине Николић и др Маријане Мраовић.Приказ публикације: Извештаји и наредбе Недићеве "Владе народног спаса" за Округ пожаревачки, 1941-1942. године : [зборник докумената]. Том 1, приредиле Јасмина Николић и Маријана Мраовић ; аутори предговора Јасмина Николић, Горан Петровић, Маријана Мраовић. - Пожаревац : Историјски архив ; Београд : Војни архив, 2018 (Смедерево : Newpress). - 269 стр. : илустр. ; 25 cm. - (Зборници докумената / [Историјски архив Пожаревац] ; зборник 4) ISBN 978-86-84969-89-

Yb3+/Tm3+ doped SrGd2O4 as photoluminescent and photocatalytic material

In this work we present new up-conversion materials, consisted of SrGd2O4 doped with different concentration of Yb3+ (2, 4, 6 at%) ions and constant concentration of Tm3+ (1 at%), prepared by the combustion method. X-ray powder diffraction (XRPD) showed that assynthesized nanoparticles have orthorhombic structure (Pnma), assigned to the JCPDS Card No:01-072-6387. Scanning electron microscopy (SEM) revealed that obtained nanostructure is composed of porous agglomerated nanoparticles, while energy dispersive spectroscopy (EDS) confirmed presence and uniform distribution of all constituting elements accross the sample. Luminescent properties were evaluated and discovered two blue emission bands at 450 nm and 474 nm, and one red emission band at 650 nm. The sample co-doped with 4 at% Tm3+ showed the most intense photoluminescent emission, and because of that was used in the photocatalytic exiperiment. UV-VIS Diffuse Reflectance Spectroscopy was performed in order to examine materials bandgap, and value of 4.3 eV was obtained as well as the additional values from the bands at lower energies, which indicate potentially good photocatalytic properties. X-ray photoelectron spectroscopy (XPS) revealed presence of OHgroups on the surface which also have positive impact on the photocatalytic performances of the material. UV-VIS Absorption Spectroscopy was used to measure changes of the methylene blue concentration during the photocatalytic degradation process. After 4 h of exposure to the simulating Sun irradiation, the results indicate successful dye decomposition rate. Reaction parameters (MB concentration and catalyst mass) were altered in order to achieve the best photocatalytic performances of this newly synthesized materials.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

One-pot synthesis of biocompatible NaYF4:Yb,Er nanoparticles for cell labeling

In modern medical research, great attention has been focused to the development of the new biomarkers which include up-converting nanoparticles (UCNPs). Their optical response is triggered by NIR radiation that achieves deeper tissue penetration when compared with traditionally used fluorophores. In this work, biocompatible NaYF4: Yb, Er nanoparticles were synthesized by polymer assisted one-pot solvothermal processing using chitosan or poly(lacticco- glycolic acid). X-ray powder diffraction and electron microscopy results revealed differences in crystal arrangement and morphology of the as-synthesized particles. Fourier transform infrared spectroscopy confirmed the presence of corresponding polymers moiety on UCNPs surface providing their biocompatibility and low cytotoxicity towards human gingival fibroblasts (HFG). As a consequence of efficient up-conversion, prominent green emission (between 512-533nm and between 533-560nm) as well as red emission (630-690nm) were recorded in the particles photoluminescence spectra, and these are applied further in the visualization of the HFG using the laser scanning microscopy with a NIR laser source

Effects of soybean carbohydrates and lactobacillus helveticus bgra43 on metabolic processes in rat colon

Aim of this work was to assess the metabolic and physiological changes that occurred in the hind gut of rats after feeding with soybean carbohydrates alone and in combination with Lactobacillus helveticus BGRA43. Wistar rats were gavaged with soybean flour for 28 days. The parameters assessed included fecal volatile organic compounds, and L-lactate, reducing sugars, proteins, ammonia and water levels in the colonic lumen. The presence of lactic acid (LAB), sulfate reducing (SRB) and methanogenic bacteria was assessed by semi-quantitative PCR. Malondialdehyde levels as well as lymphoid tissue size in ileal and colonic mucosa were also evaluated. On the basics of the results obtained, correlation network was created, setting the parameters tested in research in two metabolic groups: saccharolytic and proteolytic fermentation group. The principal finding of the study is a negative correlation between oral administration of BGRA43 and increase of parameters related to carbohydrate fermentation in the gut, and a positive correlation to factors related to proteolytic fermentation. On the contrary, soybean carbohydrates were correlated with increased values of factors related to carbohydrate catabolism. Different effects of BGRA43 and soybean carbohydrates on metabolic processes in colonic lumen indicate the possibility of applying the BGRA43 in alleviating the gastrointestinal symptoms occurring after consuming hardly digestible carbohydrates

Ethylenediaminetetraacetic acid (EDTA) assisted hydro/solvothermal synthesis of up-converting rare earth fluorides

Over the last decade, a lot of effort was directed toward developing of the representative methodologies for the preparation of up-converting (UC) particles which exhibit a unique narrow visible emission when excited by lower-energy photon radiation. This work presents the impact of different processing parameters on structural, morphological and optical properties of up-converting (UC) rare earth fluorides obtained by hydro/solvothermal synthesis. Monodisperse NaYF4:Yb3+/Er3+ particles with different morphology, size and crystal phase were synthesized with a help of ethylenediaminetetraacetic acid (EDTA) through adjusting the precursor concentration, degree of doping, polarity of solvent and reaction time. They are characterized by X-ray powder diffraction, scanning and transmission electron microscopy, energy dispersive X-ray and Furrier transform infrared spectroscopy, as well as photoluminescence measurements. It was shown that particle size and phase composition are dependent on the precursor concentration, type of solvent and doping degree, while the cubic to hexagonal transformation of NaYF4:Yb3+/Er3+ phase is affected by the reaction time. The crystallization of the orthorhombic YF3:Yb3+/Er3+ phase is established either after decreasing concentration of dopants or increasing polarity of solvents. All of the synthesized particles exhibited efficient up-conversion emission which can be tuned from pure green to the yellowish-orange through control of particles size and phase composition

Effect of Gd3+ introduction on YF3: Yb, Er structural, morphological and optical properties

Monosized up-converting nanoparticles (UCNPs) with a spherical shape and biocompatible surface have a wide application in biomedicine as new cell markers or light-triggered drug delivery agents. The synthesis of the hexagonal β-NaYF4:Yb/Er phase is of a great interest, because of its most efficient up-conversion luminescence. Beside it, synthesis of the UCNPs based on YF3:Yb/Er phase is also attractive due to its orthorhombic phase arrangement and fact that higher concentration of dopants could be introduced in such crystal lattice. In this work the synthesis of pure and Gd-doped YF3:Yb/Er phases were performed through hydro/solvo thermal method using a biocompatible chitosan as a surfactant. The XRD analysis showed that independently of the gadolinium content formation of the orthorhombic phase is achieved, but intensity of the green emission due to the (2H11/2, 4S3/2) → 4I15/2 electronic transitions was highest for un-doped YF3:Yb/Er sample

Citrate assisted solvothermal synthesis of beta-NaYF4: Yb, Er up-converting nanoparticles

Thanks to the unique optical properties, up-converting nanoparticles (UCNPs) have a wide application in optoelectronics, forensics, security and biomedicine. The synthesis of the most efficient hexagonal β-NaYF4: Yb/Er phase is usually performed through thermal decomposition of organic precursors which could cause the UCNP cytotoxicity. Since cubic polymorph is kinetically more stable than hexagonal, we used citric acid and Na-citrate for the nucleation of hexagonal NaYF4: Yb, Er phase in nanosized particles. Additionally, effect of different precipitation agents (NaF, NH4F and NH4HF2) used during solvothermal synthesis is explored. The XRPD analysis showed that using of citric acid led to a product composed from mixture of cubic and hexagonal NaYF4: Yb/Er phase, while the presence of Na-citrate influences the nucleation of well crystallized hexagonal β-NaYF4: Yb/Er phase, regardless of precipitation agents used. All samples are composed of polycrystalline spherical particles which size is influenced by the precursor chemistry. UCNPs emit intense green emission due to the (2H11/2, 4S3/2) → 4I15/2 electronic transitions, after been excited with infrared light (λ=978 nm)

Ethylenediaminetetraacetic acid (EDTA) assisted hydro/solvothermal synthesis of up-converting rare earth fluorides

Over the last decade, a lot of effort was directed toward developing of the representative methodologies for the preparation of up-converting (UC) particles which exhibit a unique narrow visible emission when excited by lower-energy photon radiation. This work presents the impact of different processing parameters on structural, morphological and optical properties of up-converting (UC) rare earth fluorides obtained by hydro/solvothermal synthesis. Monodisperse NaYF4:Yb3+/Er3+ particles with different morphology, size and crystal phase were synthesized with a help of ethylenediaminetetraacetic acid (EDTA) through adjusting the precursor concentration, degree of doping, polarity of solvent and reaction time. They are characterized by X-ray powder diffraction, scanning and transmission electron microscopy, energy dispersive X-ray and Furrier transform infrared spectroscopy, as well as photoluminescence measurements. It was shown that particle size and phase composition are dependent on the precursor concentration, type of solvent and doping degree, while the cubic to hexagonal transformation of NaYF4:Yb3+/Er3+ phase is affected by the reaction time. The crystallization of the orthorhombic YF3:Yb3+/Er3+ phase is established either after decreasing concentration of dopants or increasing polarity of solvents. All of the synthesized particles exhibited efficient up-conversion emission which can be tuned from pure green to the yellowish-orange through control of particles size and phase composition

Lactobacillus fermentum Postbiotic-induced Autophagy as Potential Approach for Treatment of Acetaminophen Hepatotoxicity

The aim of this study was to investigate the potential of postbiotics originated from Lactobacillus fermentum BGHV110 strain (HV110) to counteract acetaminophen (APAP)-induced hepatotoxicity in HepG2 cells. This strain was selected according to its autophagy inducing potential, based on previous studies reporting protective role of autophagy in APAP caused cellular damage. Cell viability was assessed using MTT and LDH assays, while autophagy was monitored by qPCR analysis of BECN1, Atg5, p62/SQSTM1, and PINK1 mRNA expression and by Western blot analysis of p62/SQSTM1 and lipidated LC3 accumulation. Our results showed that detrimental effect of APAP on cell viability was suppressed in the presence of HV110 which was linked with increased conversion of LC3 protein and p62/SQSTM1 protein degradation. Additionally, higher p62/SQSTM1 and PINK1 mRNA transcription were noticed in cells co-treated with APAP/HV110, simultaneously. In conclusion, this study suggests that HV110 enhances activation of PINK1-dependent autophagy in HepG2 cells and its eventual co-supplementation with APAP could be potentially used for alleviation of hepatotoxic side effects caused by APAP overdose