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Investigation of the interactions and electromagnetic shielding properties of graphene oxide/platinum nanoparticle composites prepared under low-dose gamma irradiation
No full textA low-dose gamma irradiation was used for the one-step synthesis of graphene oxide/platinum nanoparticle composites. Various spectroscopic and microscopic methods were employed to structurally and morphologically characterize the prepared composites, and the nature of the interactions between graphene oxide sheets and platinum clusters was investigated using density function theory (DFT). Gamma irradiation caused the reduction of hexachloroplatinic acid, resulting in the formation of Pt nanoparticles and the simultaneous partial reduction of graphene oxide (GO). Pt nanoparticles synthesized at doses of 10 and 20 kGy showed a homogeneous GO surface coverage with a high portion of particles with sizes of up to 10 nm. The DFT results indicate a difference in electrical conductivity between GO and PtNPs. This could cause charge redistribution across the contact area, creating a conductive network at the interface that should enhance the EMI shielding capabilities of the composite. The shielding efficiency of the composites measured at the X band showed a blockage of 77% of the incident electromagnetic wave at a center frequency of 10 GHz. The composite prepared at a 20 kGy dose exhibited a greater contribution from a mismatch loss component, attributed to the improved electrical conductivity induced by irradiation
Izolovanje i karakterizacija verbaskozida iz biljke Plantago lanceolata L.
No full textU okviru ovog istraživanja najviše pažnje je posvećeno izolovanju i hemijskoj karakterizaciji specijalizovanih metabolita iz listova biljke Plantago lanceolata¸ gajene u veštačkim uslovima. Istraživanje je započeto višestepenom polarnom ekstrakcijom biljnog materijala, nastavljeno brzom kolonskom hromatografijom (dry-flash column chromatography). Za finalno prečišćavanje koriščena je semi-preparativna visokoefikasna tečna hromatografija (HPLC). Tankolskojnom hromatografijom (TLC) i HPLC-om je praćena efikasnost razdvajanja i čistoća dobijenih frakcija tokom procesa izolovanja. Primenom modernih spektroskopskih i spektrometrijskih metoda (NMR i LC-HRMS) utvrđeno je da je izolovani metabolit polifenolni glikozid verbaskozid. Dobijeni rezultati pružaju osnovu za dalja istraživanja njegove uloge u odgovoru biljke na hemijski stres, kao i njegovih farmakoloških svojstava i primene u farmaceutskoj i prehrambenoj industriji
Interakcija Ara h 1 iz pečenog kikirikija sa THP 1 M0 makrofagima i modulatorna uloga lipida kikirikija
No full textU razvoju alergija na hranu ključnu ulogu imaju antigen prikazujuće ćelije, među njima i makrofagi, koje obrađuju alergene hrane, predstavljaju ih naivnim T ćelijama i time utiču na razvoj imunog odgovora. Na prepoznavanje i preuzimanje alergena, kao i na formiranje imunog odgovora, mogu značajno uticati faktori kao što su termička obrada i sastav matriksa hrane. Cilj ovog rada bio je da se: 1) uspešno izoluje i prečisti Ara h 1 iz odmašćenog praha termički obrađenog (pečenog) kikirikija, 2) ispita proces vezivanja/preuzimanja Ara h 1, jednog od glavnih alergena kikirikija, od strane THP 1 M0 makrofaga, uz analizu uticaja lipida kikirikija na ovaj proces; 3) ispita zavisnost efikasnosti preuzimanja alergena od početne koncentracije i vremena tretmana i 4) proceni aktivacija NF κB signalnog puta i proizvodnja citokina IL 6 i IL 10 nakon tretmana THP 1 M0 makrofaga alergenom Ara h 1, uz analizu uticaja lipida kikirikija na ove procese.
Ara h 1 je izolovan iz odmašćenog praha pečenog kikirikija kombinacijom taložnih i hromatografskih metoda. Nakon fluorescentnog obeležavanja Ara h 1 FITC om, THP 1 M0 makrofagi su tretirani ovim alergenom, kao i kombinacijom alergena i lipida kikirikija. Aktivacija NF κB signalnog puta analizirana je pomoću luciferaznog reporter eseja pod kontrolom NF κB promotora, dok su koncentracije citokina IL 6 i IL 10 određene ELISA metodom
Sinteza i karakterizacija kompleksa renijuma(V) sa N,N-ligandima
No full textUspeh hemioterapeutika na bazi platine podstakao je naučna istraživanja u pravcu sintetisanja novih kompleksnih jedinjenja različitih prelaznih metala sa raznovrsnim organskim molekulima kao ligandima radi ispitivanja njihovog citotoksičnog potencijala. Glavni cilj pomenutih istraživanja jeste pronalaženje efikasnijih i manje toksičnih jedinjenja koja će ući u klinička ispitivanja. Posebnu pažnju u novije vreme privlače kompleksi renijuma(I) i renijuma(V) sa različitim N,N N,S i N,O-ligandnim sistemima, koji mogu prevazići rezistenciju i neželjene efekte već postojećih platinskih lekova. Renijum može da postoji u velikom broju oksidacionih stanja, što mu omogućava da formira različite tipove kompleksa sa raznovrsnim ligandima i koordinacionim geometrijama. Renijum ima dva radioizotopa 186Re i 188Re koji su našli primenu u nuklearnoj medicini. Najčešći strukturni motiv u kompleksima je stabilno trikarbonil renijum(I) jezgro. Istražena su i jedinjenja renijuma viših oksidacionih stanja među kojima su se izdvojili okso kompleksi renijuma(V). Utvrđeno je da kompleksi renijuma indukuju ćelijsku smrt različitim mehanizmima kao što su nekroza, apoptoza i paraptoza. Izmenom liganada može se podesiti fotoluminiscencija, lipofilnost i citotoksičnost renijumskih kompleksa. S toga predmet naučnog istraživanja ovog završnog rada predstavlja sintezu i karakterizaciju kompleksnih jedinjenja renijuma(V) sa N,N-ligandima na bazi fenantrolina
Interlaboratory Comparison Reveals State of the Art in Microplastic Detection and Quantification Methods
No full textIn this study, we investigate the current accuracy of widely used microplastic (MP) detection methods through an interlaboratory comparison (ILC) involving ISO-approved techniques. The ILC was organized under the prestandardization platform of VAMAS (Versailles Project on Advanced Materials and Standards) and gathered a large number (84) of analytical laboratories across the globe. The aim of this ILC was (i) to test and to compare two thermo-analytical and three spectroscopical methods with respect to their suitability to identify and quantify microplastics in a water-soluble matrix and (ii) to test the suitability of the microplastic test materials to be used in ILCs. Two reference materials (RMs), polyethylene terephthalate (PET) and polyethylene (PE) as powders with rough size ranges between 10 and 200 μm, were used to press tablets for the ILC. The following parameters had to be assessed: polymer identity, mass fraction, particle number concentration, and particle size distribution. The reproducibility, SR, in thermo-analytical experiments ranged from 62%–117% (for PE) and 45.9%–62% (for PET). In spectroscopical experiments, the SR varied between 121% and 129% (for PE) and 64% and 70% (for PET). Tablet dissolution turned out to be a very challenging step and should be optimized. Based on the knowledge gained, development of guidance for improved tablet filtration is in progress. Further, in this study, we discuss the main sources of uncertainties that need to be considered and minimized for preparation of standardized protocols for future measurements with higher accuracy
III International Conference on Noncovalent Interactions (ICNI-III)
No full textThis virtual collection of Reviews, Concepts and Research Articles in Chemistry Europe journals (Chem. Eur. J., Eur. J. Inorg. Chem., Eur. J. Org. Chem., ChemCatChem, ChemPlusChem and ChemPhysChem) highlights the latest developments in the field of weak interactions. The Collection includes contributions from participants of ICNI-III (17-21 June 2024, Belgrade, Serbia) and from other researchers in this exciting are of research
Primena BaCl2, HCl i CH3COOH za procenu efikasnosti ekstrakcije mikro- i makroelemenata urbanog zemljišta grada Zagreba
No full textU ovom radu ispitivani su uzorci urbanog zemljišta grada Zagreba primenom metode ekstrakcije u jednom koraku upotrebom tri različita ekstrakciona sredstva: 0,1M BaCl2, 2M HCl i 0,43M CH3COOH. Cilj rada je bio procena mobilnosti i biodostupnosti mikro- i makroelemenata, kao i poređenje efikasnosti tri različita reagensa za ekstrakciju 17 elemenata iz 25 uzoraka zemljišta sa teritorije grada Zagreba. Za kvantitiativno određivanje sadržaja elemenata korišćena je indukovano spregnuta plazma - optička emisiona spektroskopija (ICP-OES), pri čemu su praćene koncentracije sledećih elemenata: Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Sr i Zn
Efficient nano-size ZnM/rGO (M = Ni, Cu, and Fe) electrocatalysts for oxygen electrode reactions in alkaline media
No full textHerein, zinc with nickel, copper, and iron was deposited on reduced graphene oxide (rGO) (ZnM/rGO, M = Cu, Ni, Fe) and examined as novel bifunctional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reaction in alkaline media. Fourier-transform infrared and X-ray photoelectron spectroscopy, X-ray powder diffraction analysis, transmission, and scanning electron microscopy with energy-dispersive X-ray spectroscopy were used for the examination of structural and morphological properties of ZnM/rGO. ZnFe/rGO showed the lowest OER overpotential and Tafel slope, the highest OER current density with the lowest charge-transfer resistance. Furthermore, ORR at ZnFe/rGO proceeds by mixed 2e/4e mechanism, and by 2e mechanism at the other materials. Still, ZnCu/rGO showed the most positive onset potential and low Tafel slope during ORR. Hence, ZnFe/rGO presents the best OER activity with further improvements needed in terms of its ORR performance to reach full potential for rechargeable metal-air batteries and unitized regenerative fuel cells
Reversible Inhibition of Cysteine Proteases Using S-Methyl Methanethiosulfonate
No full textCysteine proteases find applications in diverse fields, but their susceptibility to autolysis poses storage challenges. Unlike irreversible inhibitors, S-methyl methanethiosulfonate (MMTS) enables enzyme reactivation, offering an ideal solution for preventing autolysis during storage and allowing subsequent protein activation when required. Here, we describe effective methods for inhibiting and reactivating papain, providing valuable insights for enhancing the storage and usability of cysteine proteases in various scientific, medical, and industrial applications
Temporal changes in the flexural properties of 3D-printed ABS specimens
No full textThis study investigates the environmental aging effects on 3D-printed Acrylonitrile Butadiene Styrene (ABS) produced using Fused Deposition Modeling (FDM) and Digital Light Processing (DLP) techniques. The materials in filament (FDM) and resin (DLP) forms were exposed to UV light, humidity, and temperature fluctuations over two months. Mechanical testing via three-point bending and Fourier Transform Infrared Spectroscopy (FTIR) were employed to assess the impact of these environmental factors. Results showed notable mechanical strength and structural stability differences between the FDM-printed filament and DLP-printed resin ABS under aging conditions. The filament-based ABS exhibited superior mechanical properties, retaining its strength over time, while the resin-based ABS degraded significantly shortly after printing. Despite exposure to ambient environmental conditions, the chemical composition of both materials remained stable throughout the research period