Detekcja bezołowiowych nanokryształów fluorkowych rozproszonych w materiałach zol-żelowych przy użyciu dyfrakcji rentgenowskiej oraz metod mikroskopowych i spektroskopowych

Nowadays, the development of researches concentrated on synthesis and characterization of oxyfluoride glass-ceramics doped with rare earth ions is a forefront direction in current materials engineering. The glass-ceramics are the class of innovative optical materials, which contain the fluoride nanocrystals dispersed in oxide amorphous matrices. Such materials combine good mechanical strength and chemical durability of oxide hosts with high luminescence efficiency of rare earth ions incorporated into low-phonon fluoride crystals. Generally, the oxyfluoride glass-ceramic materials are commonly fabricated via controlled heat-treatment of glasses derived by conventional melt-quenching method. Alternatively, such materials can be successfully prepared via sol-gel technique, which is based on polycondensation reaction in liquids phase. Due to the fact that the heat-treatment of xerogels could be conducted at significantly lower temperatures compared with melting of glass-forming components, the sol-gel method seems to be a particularly attractive technique to fabricate the oxyfluoride glass-ceramic materials dedicated for optoelectronic applications. In this doctoral dissertation, the Eu3+-doped glass-ceramic materials containing MF2 (M = Ca, Sr, Ba) or MF3 (M = Y, La, Gd) nanocrystals were synthesized via sol-gel method and characterized. The studied materials were fabricated by controlled heat-treatment of silicate xerogels and the structural changes within sol-gel hosts were verified using IR-ATR spectroscopy. The individual fluoride crystal phases were identified by XRD measurements and the received results were confirmed by high resolution mode in transmission electron microscope HR-TEM. The structural changes during controlled heat-treatment of precursor xerogels were also evaluated based on unique spectroscopic behavior of optically active Eu3+ ions, which results from the nature of their intra-configurational 4f6-4f6 transitions. Due to the significant decrease of R/O-ratio values after conducted heat-treatment process as well as observable splitting of emission bands, 3+ the partial incorporation of Eu3+ ions into precipitated MF2 (M = Ca, Sr, Ba) and MF3 (M = Y, La, Gd) fluoride nanocrystals was confirmed. Moreover, the change in character of registered decay curves of the 5D0 excited state from mono-exponential (xerogels) to bi-exponential (glass-ceramics) clearly evidenced the distribution of Eu3+ ions between sol-gel hosts and fluoride nanocrystals. In summary, the above techniques allow for the full characterization of the glass-ceramic materials, with particular emphasis on the crystallization of fluoride phases in nanometric range

Energy transfer study on Tb3+/Eu3+ Co-activated sol-gel glass-ceramic materials containing MF3 (M = Y, La) nanocrystals for NUV optoelectronic devices

In the present work, the Tb3+/Eu3+ co-activated sol-gel glass-ceramic materials (GCs) containing MF3 (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 C. The studies of Tb3+ ! Eu3+ energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4fn–4fn optical transitions of Tb3+ (5D4 !7FJ, J = 6–3) as well as Eu3+ ions (5D0 ! 7FJ, J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the 5D4 (Tb3+) and the 5D0 (Eu3+) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET e ciency was also observed (from ET 16% for xerogels up to ET = 37.3% for SiO2-YF3 GCs and ET = 60.8% for SiO2-LaF3 GCs). The changes in photoluminescence behavior of rare-earth (RE3+) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO2-MF3:Tb3+, Eu3+ GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation

Reddish-Orange Luminescence from BaF2:Eu3+ Fluoride Nanocrystals Dispersed in Sol-Gel Materials

Nanocrystalline transparent BaF2:Eu3+ glass-ceramic materials emitting reddish-orange light were fabricated using a low-temperature sol-gel method. Several experimental techniques were used to verify structural transformation from precursor xerogels to sol-gel glass-ceramic materials containing fluoride nanocrystals. Thermal degradation of xerogels was analyzed by thermogravimetric analysis (TG) and di erential scanning calorimetry method (DSC). The presence of BaF2 nanocrystals dispersed in sol-gel materials was confirmed by the X-ray di raction (XRD) analysis and transmission electron microscopy (TEM). In order to detect structural changes in silica network during annealing process, the infrared spectroscopy (IR-ATR) was carried out. In particular, luminescence spectra of Eu3+ and their decays were examined in detail. Some spectroscopic parameters of Eu3+ ions in glass-ceramics containing BaF2 nanocrystals were determined and compared to the values obtained for precursor xerogels. It was observed, that the intensities of two main red and orange emission bands corresponding to the 5D0!7F2 electric-dipole transition (ED) and the 5D0!7F1 magnetic-dipole (MD) transition are changed significantly during transformation from xerogels to nanocrystalline BaF2:Eu3+ glass-ceramic materials. The luminescence decay analysis clearly indicates that the measured lifetime 5D0 (Eu3+) considerably enhanced in nanocrystalline BaF2:Eu3+ glass-ceramic materials compared to precursor xerogels. The evident changes in luminescence spectra and their decays suggest the successful migration of Eu3+ ions from amorphous silica network to low-phonon BaF2 nanocrystals

Sol-Gel Glass-Ceramic Materials Containing CaF2:Eu3+ Fluoride Nanocrystals for Reddish-Orange Photoluminescence Applications

CaF2:Eu3+ glass-ceramic sol-gel materials have been examined for reddish-orange photoluminescence applications. The transformation from precursor xerogels to glass-ceramic materials with dispersed fluoride nanocrystals was verified using several experimental methods: di erential scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray di raction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR-ATR), energy dispersive X-ray spectroscopy (EDS) and photoluminescence measurements. Based on luminescence spectra and their decays, the optical behavior of Eu3+ ions in fabricated glass-ceramics were characterized and compared to those of precursor xerogels. In particular, the determined luminescence lifetime of the 5D0 excited state of Eu3+ ions in nanocrystalline CaF2:Eu3+ glass-ceramic materials is significantly prolonged in comparison with prepared xerogels. The integrated intensities of emission bands associated to the 5D0 ! 7F2 electric-dipole transition (ED) and the 5D0 !7F1 magnetic-dipole transition (MD) are changed drastically during controlled ceramization process of xerogels. This implies the e cient migration of Eu3+ ions from amorphous silicate sol-gel network into low-phonon energy CaF2 nanocrystals

Studies of sol-gel evolution and distribution of Eu3+ ions in glassceramics containing LaF3 nanocrystals depending on initial sols composition

In this work, we performed a systematic analysis of the impact of selected chemical reagents used in sol-gel synthesis (i.e., N,N-dimethylformamide) and different catalyst agents (i.e., CH3COOH, HNO3) on the formation and luminescence of Eu3+-doped SiO2–LaF3 nano-glass–ceramics. Due to the characteristic nature of intra-configurational electronic transitions of Eu3+ ions within the 4f6 manifold (5D0 → 7FJ, J = 0–4), they are frequently used as a spectral probe. Thus, the changes in the photoluminescence profile of Eu3+ ions could identify the general tendency of rare earth materials to segregate inside low-phonon energy fluoride nanocrystals, which allows us to assess their application potential in optoelectronics. Fabricated sol-gel materials, from sols to gels and xerogels to nano-glass–ceramics, were examined using several experimental techniques: X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), and luminescence measurements. It was found that the distribution of Eu3+ ions between the amorphous silicate solgel host and LaF3 nanocrystals is strictly dependent on the initial composition of the obtained sols, and the lack of N,N-dimethylformamide significantly promotes the segregation of Eu3+ ions inside LaF3 nanocrystals. As a result, we detected long-lived luminescence from the 5D0 excited state equal to 6.21 ms, which predisposes the obtained glass–ceramic material for use as an optical element in reddish-orange emitting devices

Fabrication of fluoride nanocrystals and their spectroscopic properties

In this work, the fabrication of glass-ceramic materials containing MF3:Eu3+ (M = La, Gd) nanocrystals dispersed in silica sol-gel hosts has been presented. The transformation from liquid sols towards bulk samples was also examined based on IR measurements. The crystallization temperatures and formation of MF3 phases were verified based on TG/DSC analysis and XRD measurements. The optical properties of prepared Eu3+-doped samples were evaluated based on PLE and PL as well as luminescence decay analysis of the 5D0 excited state. Obtained samples exhibit a series of the 5D0 → 7FJ (J = 1–4) emission bands, which were recorded within the reddish-orange spectral area under near-UV illumination (λexc = 393 nm). Recorded luminescence spectra and double-exponential character of decay curves for prepared glass-ceramic samples indicated the successful migration of Eu3+ dopant ions from amorphous silica framework to low-phonon energy MF3 nanocrystal phases

Luminescence of SiO2-BaF2:Tb3+, Eu3+ nano-glass-ceramics made from sol-gel method at low temperature

The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE3+) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped with Tb3+, Eu3+ ions were fabricated from amorphous xerogels at 350 C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the 5D4 level of Tb3+. As a result, the visible light according to the electronic transitions of Tb3+ (5D4 ! 7FJ (J = 6–3)) and Eu3+ (5D0 ! 7FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the shortening in decay times of the 5D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+/Eu3+ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays

Structural and photoluminescence investigations of Tb3+/Eu3+ codoped silicate sol-gel glass-ceramics containing CaF2 nanocrystals

In this work, the series of Tb3+/Eu3+ co-doped xerogels and derivative glass-ceramics containing CaF2 nanocrystals were prepared and characterized. The in situ formation of fluoride crystals was verified by an X-ray diffraction technique (XRD) and transmission electron microscopy (TEM). The studies of the Tb3+/Eu3+ energy transfer (ET) process were performed based on excitation and emission spectra along with luminescence decay analysis. According to emission spectra recorded under near-ultraviolet (NUV) excitation (351 nm, 7F6 ! 5L9 transition of Tb3+), the mutual coexistence of the 5D4 ! 7FJ (J = 6–3) (Tb3+) and the 5D0 ! 7FJ (J = 0–4) (Eu3+) luminescence bands was clearly observed. The co-doping also resulted in gradual shortening of a lifetime from the 5D4 state of Tb3+ ions, and the ET efficiencies were varied from ET = 11.9% (Tb3+:Eu3+ = 1:0.5) to ET = 22.9% (Tb3+:Eu3+ = 1:2) for xerogels, and from ET = 25.7% (Tb3+:Eu3+ = 1:0.5) up to ET = 67.4% (Tb3+:Eu3+ = 1:2) for glass-ceramics. Performed decay analysis from the 5D0 (Eu3+) and the 5D4 (Tb3+) state revealed a correlation with the change in Tb3+–Eu3+ and Eu3+–Eu3+ interionic distances resulting from both the variable Tb3+:Eu3+ molar ratio and their partial segregation in CaF2 nanophase

3D PET image reconstruction based on Maximum Likelihood Estimation Method (MLEM) algorithm

Positron emission tomographs (PET) do not measure an image directly. Instead, they measure at the boundary of the field-of-view (FOV) of PET tomograph a sinogram that consists of measurements of the sums of all the counts along the lines connecting two detectors. As there is a multitude of detectors build-in typical PET tomograph structure, there are many possible detector pairs that pertain to the measurement. The problem is how to turn this measurement into an image (this is called imaging). Decisive improvement in PET image quality was reached with the introduction of iterative reconstruction techniques. This stage was reached already twenty years ago (with the advent of new powerful computing processors). However, three dimensional (3D) imaging remains still a challenge. The purpose of the image reconstruction algorithm is to process this imperfect count data for a large number (many millions) of lines-of-responce (LOR) and millions of detected photons to produce an image showing the distribution of the labeled molecules in space.Comment: 10 pages, 7 figure

Navigating the landscape of Postpartum Depression: a comprehensive review

Introduction and purpose: The joyous occasion of childbirth is often overshadowed by the prevalence of postpartum depression (PPD), a complex mental health condition affecting mothers globally. This paper reviews the current state of knowledge on PPD, exploring its frequency, risk factors, pathogenesis, symptoms, and impact on maternal and child health. Description of the State of Knowledge: Recent studies indicate an alarming increase in PPD rates, with notable racial and socioeconomic disparities. Symptoms of PPD, ranging from mild to severe include mood disturbances, cognitive impairments, and self-harm ideation. The repercussions extend beyond the postpartum period, affecting long-term child development, breastfeeding practices, and the mother-infant bond. Advancements in screening tools, particularly the Edinburgh Postnatal Depression Scale (EPDS), have facilitated early detection. However, creating an environment conducive to open communication about mental health remains a significant challenge. Interventions for PPD include psychotherapeutic approaches, pharmacological interventions, and complementary therapies. Brexanolone, the first FDA-approved drug for PPD, represents a significant breakthrough. Community-based and peer support programs, alongside a multidisciplinary approach involving healthcare professionals and support networks, have shown promise in alleviating PPD symptoms. Summary: In conclusion, PPD remains a substantial public health concern. Increased awareness of its multifaceted nature has led to improved screening, diagnosis, and intervention strategies. Ongoing dialogue, supportive environments, and refined treatments are essential for enhancing the well-being of both mothers and their infants in the postpartum period