Vinča Institute of Nuclear Sciences
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Chemical Titrations and Temperature-Programmed Desorption Study of the Surface Chemistry of Graphene Oxide and 12-Tungstophosphoric Acid Nanocomposite
No full textThe surface chemistry of graphene oxide (GO) and its nanocomposite with 12-tungstophosphoric acid (WPA) (up to 50 wt.% WPA) was studied both in aqueous suspension and in the solid state. The titrations revealed the formation of the composite already in the suspension and that WPA influences GO’s functionalities and their conversion (-COOR to -COOH). There is a loading of WPA (>20 wt.%) beyond which the WPA dominates the chemical character of the GO/WPA suspension. Part of the nanocomposite titrated with NaOH was processed into a powdered form and compared with an annealed sample (450 ◦C, Ar atmosphere). An FTIR analysis revealed the removal of functional groups in both titrated and thermally annealed samples. Annealing did not induce structural changes in WPA within the composite, whereas titration led to noticeable modifications of WPA-related bands. The TPD measurements revealed that the extent of functional group removal by titration was lower compared to annealing. The zeta-potential measurements demonstrated improved stability of the nanocomposite as the WPA content increased. Methylene blue adsorption experiments showed that the presence of oxygen functional groups and WPA on the GO enhances adsorption performance compared to pristine GO. Titration improved the adsorption capacity of the composites, whereas annealing completely suppressed their adsorption properties
Tunable up-conversion and down-conversion photoluminescence of HfO2:Er3+ and HfO2:Er3+/Yb3+ coatings formed by plasma electrolytic oxidation of hafnium
No full textThis study examines the structural and photoluminescent properties of HfO2 coatings doped with Er3+ and co-doped with Yb3+, prepared on hafnium substrates using the plasma electrolytic oxidation (PEO) technique with electrolytes containing Er2O3 and Yb2O3 particles. The coatings are crystalline and consist of monoclinic and tetragonal phases of HfO2 Incorporation of Er and Yb into the HfO2 lattice induces a phase transformation, stabilizing the tetragonal phase. Up-conversion (UC) photoluminescence (PL) of HfO2:Er3+ and HfO2:Er3+/Yb3+ under 980 nm excitation shows characteristic green (2H11/2 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) emissions from Er3+. Increasing the Er3+ concentration enhances the total UC PL intensity, with a disproportionate increase in red emission, attributed to concentration-dependent cross-relaxation processes that populate the 4I13/2 level, followed by excited state absorption. Co-doping HfO2:Er3+ with Yb3+ results in a significant enhancement of UC PL intensity, up to 30 times at the optimal Yb2O3 concentration of 1 g/L in the electrolyte. This enhancement is due to efficient energy transfer from the Yb3+ sensitizer to the Er3+ activator. Furthermore, the Er3+ red emission is preferentially enhanced due to a phonon-assisted Er3+ to Yb3+ energy back-transfer process, which efficiently depopulates the green-emitting 4S3/2 level and increases the population of the red-emitting 4F9/2 level. Down-conversion (DC) PL excitation and emission spectra of HfO2:Er3+ and HfO2:Er3+/Yb3+ display sharp peaks corresponding to f–f transitions of Er3+, with intensities directly proportional to the Er3+ concentration. In HfO2:Er3+/Yb3+, the DC PL intensity decreases as the Yb3+ concentration increases, particularly for the green emission. This reduction is attributed to energy transfer via cross-relaxation from excited Er3+ to Yb3+, which quenches the visible emission from Er3+,
Microhardness Enhancement in Polymer Composites via BaZrO3-Based Ceramic Reinforcement
No full textDefect-tolerant oxide ceramics offer an alternative reinforcement strategy for highperformance polymer composites beyond conventional silica- and zirconia-based systems. In this work, a novel BaZrO3-Y2O3-SrTiO3 (BZYS) ceramic hybrid was introduced as a reinforcing phase in a polyetherimide (PEI) matrix to evaluate its effect on interphase formation, thermal stability and mechanical performance. BZYS powders were prepared by ball milling and incorporated at 1 and 3 wt% into solution-cast PEI films. X-ray diffraction confirmed the preservation of the BaZrO3 perovskite structure after mechanical activation, with a slight lattice expansion, indicating partial ion incorporation and defect-mediated structural accommodation. SEM analysis revealed predominantly submicron agglomerates with homogeneous dispersion at low loading and controlled agglomeration at higher content. Differential scanning calorimetry demonstrated a systematic increase in glass transition temperature from 202.0 ◦C for neat PEI to 210.4 ◦C and 212.0 ◦C for 1 wt% and 3 wt% composites, respectively, evidencing restricted segmental mobility and interphase formation. Instrumented microindentation showed substantial hardness enhancement of 40% and 83% for 1 wt% and 3 wt% reinforcement, respectively (p < 0.05), with a strong linear dependence on filler content (R2 = 0.9845). The results demonstrate that chemically stable, strain-tolerant BZYS ceramics effectively promote interphase-mediated reinforcement in PEI, establishing a novel oxide-based pathway for mechanically enhanced dental composite materials design
Electrochemical approaches to glyphosate detection using molecularly imprinted polymer-coated metal-organic frameworks
No full textGlyphosate (GLY) is one of the most commonly used herbicides worldwide. Its widespread use raises significant concerns about public health and ecological integrity, which have led to increased control and oversight of its use, along with a growing demand for rapid and reliable monitoring. This study presents a novel electrochemical sensing platform designed for detecting GLY, utilizing the unique properties of multifunctional rare-earth metal-organic frameworks (RE-MOFs) alongside with the selective recognition capabilities of molecularly imprinted polymer (MIP) technology. The composite formed from yttrium-2-aminoterephthalic acid-based MOF and graphene oxide modifies the surface properties of a glassy carbon electrode (GCE) and serves as a support substrate for the subsequent preparation of the MIP. The crystallinity and flower-like architecture of the resulting composite, were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), while charge-transfer properties and conductivity were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The selection of the appropriate MIP for GLY detection was driven by advanced theoretical calculations, that focused on the interactions between diverse functional monomers and GLY. Theoretical determination of the optimal monomer was followed by experimental optimization of the electropolymerization method for the preparation of MIP/MOF sensors. The resulting sensor demonstrated a wide dynamic linear range (1–16 542 nM) and a subnanomolar detection limit (0.42 nM). It exhibited good specificity and an excellent recovery rate in practical applicability for water samples. The obtained results highlight the potential of the proposed sensing platform for environmental monitoring applications
The Application of Recycled Jute Non-woven Material Loaded with Zinc Ions as Substrates for Plant Growth
No full textThe challenges posed by polluted effluents containing heavy metal ions and the increasing amounts of textile waste necessitate prompt action. In response to these environmental concerns, a non-woven sorbent made from jute fibers, recycled from the carpet industry, has been developed. To enhance the sorption capacity for Zn2+ ions, the jute fibers were modified with the biopolymer alginate. The successful application of the alginate coating on the jute fibers was proved through FTIR and FESEM analyses. The presence of carboxyl and hydroxyl groups in alginate led to a 68% increase in sorption capacity. An increase in the initial concentration of ions, pH, and temperature was found to facilitate larger uptake of Zn2+ ions. To mitigate environmental risks associated with metal-saturated sorbents and accumulating textile waste, while addressing zinc deficiency in plants, the developed sorbents were evaluated as growth substrates for Lactuca sativa (lettuce) and Setaria viridis (green bristlegrass), two economically important plant species. Jute waste-growth substrates coated with alginate and enriched with Zn can provide mechanical support, humidity, and a source of this essential micronutrient to plants during early growth stages. Optimization of Zn concentration in the growth substrate can lead to the elevated levels of Zn in plant tissues, but also to the increased content of valuable bioactive compounds. Thus, recycling highly biodegradable natural jute waste and reusing it as plant growth substrates can have profound effects on environmental protection and can also be beneficial to human nutrition and health
Single-source precursor synthesis of a compositionally complex early transitional metal nitride (V, Nb, Ta, Mo, W)Nx and its high temperature stability
No full textCompositionally complex transitional metal nitrides are an interesting class of ceramics with superior chemical, thermal, and mechanical stability, with a high potential in ultra-high temperature applications and catalysis. The exceptionality in the properties may partly be explained as a consequence of their high configuration entropy. Although promising candidates, the bulk synthesis of compositionally complex metal (carbo)nitrides remains challenging, often limited by purity and scalability due to significant oxygen contamination from gaseous reactants or nitrogen loss. To offset these disadvantages, the current manuscript proposes an alternative synthesis route for the synthesis of a compositionally complex nitride (V, Nb, Ta, Mo, W)Nx, which deviates from the typical solid-state and sputtering methods by employing an organometallic precursor route and a double ammonolysis process. This is a first attempt to synthesize such ceramics with low oxygen contamination in compositionally complex (carbo)nitrides with a scalable production. Using a multidisciplinary approach consisting of theoretical methods and experiments, the current study elucidates the evolution and stability of the precursor at high temperatures under carbon, and thereby obtained ceramics at different temperatures
Facile synthesis and biocompatibility assessment of gold submicron particles formed from aqua regia via ouzo method
No full textThis study presents a novel synthesis of gold submicron particles (AuSMPs) using the ouzo effect with tea tree essential oil and aqua regia under ambient conditions. This method enables the rapid formation of smooth-surfaced, crystalline AuSMPs at room temperature without additional reducing agents or surfactants. Structural and morphological characterization (XRD, FESEM, TEM) confirmed the formation of pure, face-centered cubic gold particles ˃100 nm, encapsulated in a thin organic layer derived from the essential oil. XTT assay showed excellent biocompatibility up to 1000 µg/mL, with minimal effects observed only at the highest tested concentration. Owing to their size and surface properties, these particles hold strong potential for biomedical applications
Exact summation of special function series: Arbitrary parameter dependence and a new analytic structure from generalized Laguerre polynomials
No full textWe present closed-form evaluations for a class of infinite series involving Bessel functions, Struve functions, and generalized Laguerre polynomials, each expressed in terms of arbitrary parameter values. For the Bessel and Struve cases, the resulting expressions reduce to combinations of classical functions, notably Gamma functions and power-law terms in the free parameters. These results are valid for all parameter values ν > 0, and have been verified through high-precision analytical and numerical evaluations using both Maxima and Mathematica. The most significant contribution arises in the Laguerre case, where we construct a novel analytic function defined on the complex plane. This function, derived from the series involving generalized Laguerre polynomials, exhibits uniform convergence on every compact disk in C, and represents a previously undocumented structure in the theory of orthogonal polynomials. The findings open new avenues for functional analysis and complex-variable techniques in the study of special functions
Carcinogenic Health Risk Assessment of Benzo[a]Pyrene Bound to PM10 in Adult and Children Population Through Ambient Air in Belgrade City, Serbia
No full textParticulate matter (PM) contains various components, among which heavy metals and polycyclic aromatic hydrocarbons (PAHs) are considered the main toxic component. Serbia, a middle-income country in Southeast Europe, faces PM pollution in several towns. This study aimed to assess the carcinogenic health risk of exposure to B[a]P, a representative PAH, in Belgrade for adults and children during heating and non-heating seasons, using deterministic and probabilistic approaches for the 2018–2022 period. Average PM10 levels ranged between 32.6 and 45.3 μg/m3, and B[a]P levels between 1.4 and 3.7 ng/m3. The PM10 annual limit (40 μg/m3) was exceeded at five of fourteen stations, while the B[a]P annual limit (1 ng/m3) was exceeded at all considered monitoring stations. Risk assessment using both approaches resulted in Total Cancer Risk (TCR) values below the USEPA safe limit (1.0E-04) for both populations and seasons. Deterministic TCR values exceeded the 95th percentile (P95) of the probabilistic risk distribution, which represents the reasonable maximum exposure level according to USEPA. The highest TCR was obtained for adults during the heating season using both deterministic (5.63E-05) and probabilistic approach (1.60E-05, P95). Our results indicate that the probabilistic approach provides a more accurate representation of overall risk, leading to better risk management decisions, while the deterministic approach is more conservative due to reliance on average parameter values. Although the carcinogenic risk of B[a]P in Belgrade was acceptable, other PM compounds and exposure pathways should be considered simultaneously to achieve a more accurate health risk assessment
Current Evidence from Animal Models on Molecular Changes Underlying Antidepressant Effects of Psychobiotics
No full textThe treatment of depression is an uphill battle due to the low efficiency and delayed clinical response of antidepressants and the fact that most of them cause numerous side effects. Psychobiotics, probiotics that affect brain function and confer mental health benefits, emerged as a promising ally showing protective effects against depressive- and anxiety-like behaviors in various animal models of depression. There is rapidly accumulating evidence that psychobiotics show protective effects at the molecular level as well, affecting several pathophysiological processes implicated in depression. This narrative review summarizes preclinical insights into molecular changes related to the hypothalamic-pituitary-adrenal (HPA) axis, peripheral inflammation, neuroinflammation, neurotransmission and tryptophan metabolism underlying psychobiotic-driven mitigation of depressive and anxiety symptoms in stress-based, corticosterone-induced and inflammation-induced animal models of depression. Research evidence indicates that psychobiotics normalize the activity of the HPA axis, decrease levels of inflammatory mediators in the intestine, circulation, and brain, normalize the levels of neurotransmitters and their receptors, and regulate tryptophan metabolism in various animal models of depression. The main setbacks in this field are the extensive diversity of studied probiotic strains, which are often insufficiently characterized, and the lack of mechanistic studies in animal models. However, despite these challenges, further study of psychobiotics in the pursuit of supportive therapies for depressive disorders is firmly grounded