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Graphene quantum dots enhanced with gold nanoparticles for advanced antibacterial applications
No full textIn the era of antibiotic resistance, exploring novel nanomaterials offers a promising avenue for combating infections. This study investigates the antibacterial effects of graphene quantum dots (GQDs) combined with gold nanoparticles, synthesized in situ via gamma irradiation of GQDs with chloroauric acid and isopropyl alcohol at doses of 1, 5, 10, and 20 kGy. The composites were analyzed using several characterization methods, including photoluminescence and infrared spectroscopy, dynamic light scattering, zeta potential measurements, and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Inductively coupled plasma optical emission spectrometry analysis confirmed the presence of gold in all samples, with the highest concentration of 11.14 μg/mL. Hemolytic assays confirmed excellent biocompatibility with hemolysis below 2 %, while MTT assays revealed that cell viability exceeded 80 % for most samples, confirming their non-toxic nature. The findings showed that these materials have antibacterial activity against the MRSA strain. These results demonstrate that gold nanoparticles significantly contribute to the antibacterial properties of GQDs, indicating their potential for biomedical applications
Mullite based ceramics obtained from waste clay-diatomite
No full textMullite based ceramics have been fabricated using waste clay-diatomite from raw diatomite powder as Si and Al-nitrate as Al precursors with fibrous particles, nest like morphology. The hard mullite ceramics prepared by mold pressing (50 MPa) without additives obtained high compressive strength (up to 160 MPa at 1500 °C). The diatomite-nitrate samples were sintered at three temperatures (1300, 1400, and 1500 °C) for 1 h. XRPD of the sintered samples showed that the crystalline mineral phases mainly comprise mullite, cristobalite, and corundum. Field emission scanning electron microscopy (FESEM) images confirmed that the rod shape morphology of mullite particles, with 5 µm in length and 500 nm in diameter (aspect ratio 1:10). The mechanical stability of samples sintered at different temperatures evaluated by compressive testing showed good mechanical stability enabling the raw diatomaceous earth suitable for the production of various types of construction, and thermal insulating ceramic materials.Programme and the Book of Abstracts / 8th Conference of The Serbian Society for Ceramic Materials, 8CSCS-2025, June 14-16, 2025, Belgrade, Serbia
Nitrogen-doped carbon dots as biocompatible fluorescent agents for labelling human red blood cells
No full textEvaluating the biocompatibility of nanoparticles with blood is essential to demonstrate their biosafety, reduce potential adverse effects, and enable their application in nanomedicine. Although many studies have explored interactions between blood and nanomaterials, only limited number have specifically addressed the compatibility of nitrogen-doped carbon dots (N-CD) with red blood cells (RBC), the most abundant cells in blood, that are essential for healthy functioning of all vertebrates through their role in oxygen transport. This study investigated the biological properties of several concentrations (25, 50, 100, 200 μg/mL) of negatively charged, green fluorescent N-CD, synthesized using environmentally friendly precursors through a hydrothermal method, on healthy human RBC in vitro. Scanning electron microscopy and atomic force microscopy revealed that the treatment with N-CD, even at the highest concentration, did not significantly affect RBC morphology. Interfacial interaction between N-CD and RBC was demonstrated by photoluminescence spectroscopy, fluorescence microscopy, and synchronous fluorescence spectroscopy analysis. The treatment with N-CD at the highest concentration had no effects on the RBC osmotic fragility, slightly increased the RBC deformability, and demonstrated a noticeable protective effect on the RBC hemolysis after 24 h. Flow cytometry analysis confirmed that N-CD did not alter the RBC morphology and did not result in an increase in the production of reactive oxygen species or reactive nitrogen species, indicating that their interaction did not lead to oxidative stress induction in human RBC. These findings suggest that fluorescent N-CD are biocompatible, fluorescent RBC imaging agents and hold promise as candidates for developing novel RBC-based drug delivery systems. © 2025 Elsevier B.V
Correlation of the Microstructural, Chemical, Luminescent, and Photocatalytic Properties of SrGd2O4 Doped with Rare Earth Ions
No full textThis study evaluated the relationship between the microstructure, photoluminescence, and photocatalytic properties of newly synthesized nanostructured phosphor materials. The combustion method was used to create samples of down-converting SrGd2O4 doped with Dy3+ ions (1, and 7 at%) and up-converting SrGd2O4 co-doped with varying quantities of Yb3+ ions (2, and 6 at%) and a constant quantity of Ho3+ ions (1 at%). Transmission electron microscopy (TEM) revealed the existence of porous agglomerated round-shaped particles, with the size around 150 nm, arranged in network-like structures. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of all structural elements and their homogeneous distribution throughout the particles. The presence of specific emission peaks associated with Dy3+ or Ho3+ dopant ions was demonstrated by luminescent measurement. The degradation processes of specific organic dyes (methylene blue for up-converters and rhodamine B for down-converters) under simulated sun irradiation were used to investigate photocatalytic activity. A reduction in dye concentration in aqueous solutions was measured using UV/Vis absorption spectroscopy. The results showed a successful dye breakdown rate after 4 h, and aliquots of the working solutions were obtained at precise intervals. Additionally, the results indicated that samples with the highest luminescence intensity exhibited superior photocatalytic activity, suggesting a significant promise for usage as multifunctional materials. © 2025 by the authors
Carbon-Rich Nanocomposites Based on Polyaniline/Titania Nanotubes Precursor: Synergistic Effect Between Surface Adsorption and Photocatalytic Activity
No full textNowadays, there is an urgent need for efficient photocatalysts and adsorbents for environmentally relevant applications. This study investigates the effect of polyaniline (PANI) on the structure and performance of carbonized nanocomposites composed of PANI and TiO2 nanotubes (NTs), focusing on their photocatalytic degradation efficiency and dye adsorption capacity. The hypothesis was that PANI forms conductive carbon domains and stabilizes the anatase phase during thermal treatment, enhancing the performance of TiO2-NTs as photocatalysts. Nanocomposites based on PANI and TiO2-NTs (TTP) were synthesized through chemical oxidative polymerization of aniline (ANI) in the presence of TiO2-NTs using two TiO2/ANI molar ratios of 50 and 150 and subsequently carbonized at 650 °C, yielding CTTP-50 and CTTP-150. The novel CTTP composites and carbonized pristine TiO2-NTs (CTNT) were characterized by various techniques, including TEM, UV-Vis diffuse reflectance, Raman spectroscopy, XRD, and TGA. Their performance regarding dye adsorption and photocatalytic degradation under visible light was evaluated with Acid Orange 7, Methylene Blue, and Rhodamine B. CTTP-150 exhibited the highest adsorption capacity and photodegradation rate, attributed to the synergistic effect of PANI, which stabilizes the TiO2 phase and enhances visible-light absorption and adsorption. © 2025 by the authors
Synthesis and evaluation of C-1-alkynyl substituted N-aryl-tetrahydroisoquinolines as multitarget cholinesterase and monoamine oxidase-B inhibitors for the treatment of Alzheimer's disease
No full textA series of 35C-1-alkynylated THIQ compounds (25 new and 10 known) was synthesized, and their inhibitory potential against monoamine oxidase-B (MAO-B) and cholinesterase enzymes was assessed by evaluating the effects of introducing substituents at R1, R2, and on the phenylacetylene motif. Drug-likeness, including stability, lipophilicity and membrane permeability, was assessed theoretically and using ultra-high-performance liquid chromatography and parallel artificial membrane assays. The cytotoxic effects were evaluated on three human cell lines. The inhibition mechanism was examined by analysing the reversibility of inhibition combined with kinetic and fluorescence measurements and docking studies. Structure-activity relationship studies revealed that introducing of an alkynyl group at the C-1 position of the N-aryl-THIQs significantly influenced their inhibitory potential towards MAO-B and cholinesterase enzymes, with the effects being primarily determined by the nature of the substituents on the phenylacetylene motif and at the R2 position. Only fluoro substitution at R1 led to a significant reduction in inhibition potency for cholinesterase enzyme while in the case of MAO-B any R1 substituent was found to notably diminish the inhibitory potential. With low cytotoxic effects, satisfactory stability, and the ability to cross a blood-brain barrier, the synthesized compounds are promising candidates for further optimization in AD drug discovery. © 2025 Elsevier B.V
Efficient Ionic Liquid-Based Leaching and Extraction of Metals from NMC Cathodes
No full textThe increasing demand for lithium-ion batteries (LIBs) and their limited lifespan emphasize the urgent need for sustainable recycling strategies. This study investigates the application of tetrabutylphosphonium-based ionic liquids (ILs) as alternative leaching agents for recovering critical metals, Li(I), Co(II), Ni(II), and Mn(II), from spent NMC cathode materials. Initial screening experiments evaluated the leaching efficiencies of nine tetrabutylphosphonium-based ILs for Co(II), Ni(II), Mn(II), and Li(I), revealing distinct metal dissolution behaviors. Three ILs containing HSO4−, EDTA2−, and DTPA3− anions exhibited the highest leaching performance and were selected for further optimization. Key leaching parameters, including IL and acid concentrations, temperature, time, and solid-to-liquid ratio, were systematically adjusted, achieving leaching efficiencies exceeding 90%. Among the tested systems, [TBP][HSO4] enabled near-complete metal dissolution (~100%) even at room temperature. Furthermore, an aqueous biphasic system (ABS) was investigated utilizing [TBP][HSO4] in combination with ammonium sulfate, enabling the complete extraction of all metals into the salt-rich phase while leaving the IL phase metal-free and potentially suitable for reuse, indicating the feasibility of integrating leaching and extraction into a continuous, interconnected process. This approach represents a promising step forward in LIB recycling, highlighting the potential for sustainable and efficient integration of leaching and extraction within established hydrometallurgical frameworks. © 2025 by the authors
Utilization of Waste Clay–Diatomite in the Production of Durable Mullite-Based Insulating Materials
No full textMicrostructural, mechanical and qualitative phase identification of durable mullite-based ceramics obtained by utilization of waste clay–diatomite has been studied. Mullite-based ceramics were fabricated using waste clay–diatomite from the Baroševac open-cast coal mine, Kolubara (Serbia). The raw material consists mainly of SiO2 (70.5 wt%) and a moderately high content of Al2O3 (13.8 wt%). In order to achieve the stoichiometric mullite composition (3Al2O3-2SiO2), the raw material was mixed with an appropriate amount of Al(NO3)3·9H2O. After preparing the precursor powder, the green compacts were sintered at 1300, 1400 and 1500 °C for 2 h. During the process, rod-shaped mullite grains were formed, measuring approximately 5 µm in length and a diameter of 500 nm (aspect ratio 10:1). The microstructure of the sample sintered at 1500 °C resulted in a well-developed, porous, nest-like morphology. According to the X-ray diffraction analysis, the sample at 1400 °C consisted of mullite, cristobalite and corundum phases, while the sample sintered at 1500 °C contained mullite (63.24 wt%) and an amorphous phase that reached 36.7 wt%. Both samples exhibited exceptional compressive strength—up to 188 MPa at 1400 °C. However, the decrease in compressive strength to 136 MPa at 1500 °C is attributed to changes in the phase composition, the disappearance of the corundum phase and alterations in the microstructure. This occurred despite an increase in bulk density to 2.36 g/cm3 (approximately 82% of theoretical density) and a complete reduction in open porosity. The residual glassy phase (36.7 wt% at 1500 °C) is probably the key factor influencing the mechanical properties at room temperature in these ceramics produced from waste clay–diatomite. However, the excellent mechanical stability of the samples sintered at 1400 and 1500 °C, achieved without binders or additives and using mined diatomaceous earth, supports further research into mullite-based insulating materials. Mullite-based materials obtained from mining waste might be successfully used in the field of energy-efficient refractory materials and thermal insulators. for high-temperature applications.Featured Application: Due to their low thermal conductivity, mullite-based materials obtained from mining waste might be successfully used as insulating materials, while designing and texturing their microstructure can further enhance their insulating properties
Quantification of volatile fatty acids to safeguard reclaimed water quality
No full textBeCELS 2025: Belgrade Conference for Early-Career Life Scientists, taking place on Friday, September 5, 2025, at the Institute of Molecular Genetics and Genetic Engineering (IMGGE) in Belgrad
Principal component analysis luminescence thermometry of Ce3+ – case study of BaF2:Ce3+ single crystals
No full textLuminescence thermometry based on Ce3+-doped materials is limited by the lack of well separated emission bands and the nanosecond timescale of the 4f–5d transition, which complicate conventional temperature-readout methods. In this work, we demonstrate the application of principal component analysis (PCA) to enhance the temperature sensitivity of BaF2:Ce3+ single crystals. A crystal was grown by the vertical Bridgman method and characterized structurally and spectroscopically. Temperature-dependent photoluminescence spectra were recorded in the 300–550 K range under 270 nm LED excitation. PCA was applied to the emission spectra, enabling dimensionality reduction and extraction of a principal component (PC1) that exhibits a strong monotonic dependence on temperature. This PCA-based method achieves an average temperature resolution of ∼1 K, overcoming the limitations of traditional luminescence intensity ratio techniques for Ce3+ systems. These results highlight the potential of PCA for practical high-precision luminescence thermometry using Ce3+-doped materials