The Effect of Sulphate and Chloride Palladium Salt Anions on the Morphology of Electrodeposited Pd Nanoparticles and their Catalytic Activity for Oxygen Reduction in Acid and Alkaline Media

Pd/GC electrodes were prepared by the electrochemical deposition of palladium on glassy carbon (GC) using PdSO4 or PdCl2 salts. As-prepared GC-supported Pd nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS spectra revealed that the depositing palladium salt anion influences the oxidation state of the deposited Pd, while AFM images showed its effect on Pd nanoparticle size and coverage. The deposition from the PdCl2 salt solution resulted in smaller palladium nanoparticles, but much higher GC surface coverage than from PdSO4. The activity of Pd/GC electrodes towards oxygen reduction was examined in acid and alkaline media using the rotation-disc electrode. Among the different Pd/GC electrodes, the one prepared using PdCl2 salt with the full Pd coverage has shown the best ORR activity. The ORR occurs through a 4e-series reaction mechanism like on polycrystalline palladium but exceeds its activity concerning the initial potential

Impact of circulating vascular endothelial growth factor level and the angiogenesis degree of the aspirated coronary thrombi on angiographic and clinical outcome of patients with acute ST elevation myocardial infarction treated with primary percutaneous coronary intervention

Koronarni tromb dobijen manuelnom aspiracionom trombektomijom od pacijenata sa akutnim infarktom miokarda sa elevacijom ST-segmenta (STEMI) lečenih primarnom perkutanom koronarnom intervencijom (pPCI) predstavlja pogodan materijal za proučavanje patofizioloških mehanizama u osnovi koronarne tromboze, trajanja ishemije kod STEMI pacijenata, kao i različitog obima angiogeneze u trombu. Vaskularni endotelni faktor rasta (VEGF) je ključni molekul angiogeneze, koji se može meriti u krvi STEMI pacijenata. Vrednosti cirkulišućeg VEGF-a mogu reflektovati kompenzatorni angiogeni odgovor ishemijskog miokarda i predstavljati važan prognostički faktor kod pacijenata sa infarktom miokarda. Cilj. Cilj ove studije bio je da se odredi starost i stepen angiogeneze aspiriranog koronarnog tromba i izmeri vrednost cirkulišućeg serumskog VEGF-a (sVEGF) u populaciji STEMI pacijenata lečenih pPCI uz aspiracionu trombektomiju, kao i ispitivanje njihovog uticaja na angiografske i kliničke ishode STEMI pacijenata. Materijal i metode. U istraživanje je uključeno 100 konsekutivnih STEMI pacijenata lečenih pPCI i aspiracionom trombektomijom od kojih je dobijena adekvatna količina materijala za dalju patohistološku analizu (>1 mm3). Aspirirani materijal analiziran je svetlosnom i konfokalnom mikroskopijom. Kategorizacija trombova prema starosti (svež, litički i organizovani tromb) izvršena je bojenjem hematoksilin-eozinom. Stepen angiogeneze je određen imunohistohemijskim bojenjem na markere endotelnih ćelija (EĆ) – CD34 i CD31, i gradiran kao pojedinačne EĆ, grupisane EĆ i kapilarne petlje EĆ. Vrednosti sVEGF-a prilikom prijema pacijenata u salu za kateterizaciju pre PCI određivane su ELISA metodom. Angiografski ishodi su podrazumevali analizu stepena miokardnog ispiranja (MBG) na finalnom angiogramu i stepena rezolucije ST-elevacije (STR) na elektrokardiogramu nakon 60 minuta od pPCI. Klinički ishodi procenjeni su veličinom infarkta miokarda na osnovu maksimalnih vrednosti oslobođenih kardiospecifičnih enzima tokom hospitalizacije (CKmax, troponin Imax), ehokardiografskim parametrima veličine infarkta i remodelovanja leve komore tokom hospitalizacije i nakon 6 meseci praćenja (EDVI, ESVI, LVEF, WMSI), i učestalošću neželjenih kardiovaskularnih i cerebralnih događaja (MACCE) tokom perioda praćenja od 6 meseci nakon STEMI (smrt, reinfarkt miokarda, moždani udar, revaskularizacija infarktne arterije, tromboza stenta, hospitalizacija zbog srčane insuficijencije)...Coronary thrombus obtained by manual aspiration thrombectomy from patients with acute ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI) represents convenient material for studying pathophysiologic mechanisms underlying coronary thrombosis, duration of ischemia in STEMI patients, and the degree of thrombus angiogenesis. Vascular endothelial growth factor (VEGF) is the key molecule involved in angiogenesis, which can be measured in the blood of STEMI patients. Level of circulating VEGF could reflect compensatory angiogenic response of ischemic myocardium and represent an important prognostic factor for patients with myocardial infarction. Aim. The aim of this study was to determine the age and the angiogenesis level of aspirated thrombi, and to measure the level of circulating serum VEGF (sVEGF) in STEMI patients treated with pPCI with aspiration thrombectomy, exploring their impact of angiographic and clinical outcomes of STEMI patients. Methods. Study included 100 consecutive STEMI patients with successful thrombectomy during pPCI obtaining adequate amount of material for further pathohistologic analysis (>1 mm3). Aspirated thrombotic material was analyzed by light and confocal microscopy. Age of the aspirated thrombus (fresh, lytic and organized) was determined by hematoxylin-eosin staining. The degree of angiogenesis was assessed by immunohistochemical staning using endothelial cell (EC) markers (CD34 and CD31), and graded as single EC, clusters and EC microvessels. sVEGF was measured during the hospital admission before pPCI and detected by ELISA. Angiographic outcomes were defined as myocardial blush grade (MBG) on final angiogram, with assessing the degree of resolution of ST-elevation (STR) on electrocardiogram 60 minutes after pPCI. Clinical outcomes were evaluated by the final infarct size estimated by the maximum levels of released cardiospecific enzymes during hospitalization (CKmax, troponin Imax), echocardiographic parameters during the initial hospitalization and after 6-months follow-up (EDVI, ESVI, LVEF and WMSI), and the incidence of major adverse cardiovascular and cerebrovascular events (MACCE) during the 6-months follow-up (death, reinfarction, stroke, target vessel revascularization, stent thrombosis, hospitalization due to heart failure)..

Characterization and hydrogen evolution on Pt/nanoplatelets

Finding suitable catalysts for hydrogen evolution reaction (HER) is key for economic production of hydrogen for use in fuel cells. Reducing the amount of expensive noble metals that are used is one of the ways for obtaining such catalysts. Various combinations of different noble metals and various carbon supports have been studied. In this work nanoplatelets (GNP) was used as a support and on it Pt nanoparticles were electrochemically deposited in sub monolayer nanoislands. Obtained Pt/GNP electrode was characterized by X ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) while its electrocatalytic activity was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry . XPS analysis showed that the atomic percentages of Pt in Pt/GNP was 1.3% for electhrochemical deposition and 0.3% for spontaneous deposition, respectively. SEM micrographs of Pt/GNP electrode surface showed that Pt nanoparticles occupy mostly the edges GNP support, while elemental maping confirms the distribution of Pt, C and O over the surface of the electrode. Pt/GNP electrode has shown remarkably good performance for HER reaction in 0.5 M H2SO4 acid solution. Outstanding HER activity was achieved, showing the initial potential close to the equilibrium potential for HER and of -0.003 V and a low Tafel slope of about -30 mV/dec. The chronoamperometric measurement performed over 180 min for hydrogen evolution at the constant potential indicates good stability and durability.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Electrochemically exfoliated graphene as support of platinum nanoparticles for methanol oxidation reaction and hydrogen evolution reaction

To enhance the utilization efficiency of platinum (Pt) in electrochemical energy conversion, the precise selection of support materials presents a highly promising strategy. We have developed an efficient and stable bifunctional catalyst for methanol oxidation (MOR) and hydrogen evolution (HER) reaction in an alkaline medium. The Pt-based electrocatalyst, denoted as Pt/e-rGO with low Pt loading was successfully synthesized using graphene sheets as the support via chemical reduction using formic acid as the reducing agent. Graphene sheets are obtained by anodic electrochemical exfoliation of graphite tape. Significant enhancement of intrinsic activity toward MOR and HER was achieved for Pt/e-rGO compared to the commercial Pt/C catalyst. Structural characterization was performed by TEM, SEM and XPS. XPS analysis shows that the graphene is highly reduced. TEM analysis unveiled that the majority of the Pt nanoparticles (NPs) exhibit a diameter in the range of 4-5 nanometers, which is significant because the efficiency of electrooxidation of methanol on supported Pt NPs shows a strong dependence on particle size distribution. Catalyst activity was studied by cyclic voltammetry and linear sweep voltammetry in 0.1M KOH. Electrochemical active surface area (ECSA) was measured by CO-stripping voltammetry and estimated to be 67.93 m2 /g. Current density of 11.28 mA/cm2 ECSA at 0.82 V vs. RHE for MOR is achieved. Onset potential for MOR is 0.55 V vs. RHE. Meanwhile, for HER overporential at the current density -10 mA/cm2 ECSA was 119 mV.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Synthesis and characterization of Na0.4MnO2 as cathode material for aqueous sodium-ion batteries

The application of rechargeable batteries is growing significantly and there is a need for developing cheaper batteries with good performances. Sodium-ion batteries could be a viable option due to higher abundance of sodium against lithium mineral resources, its low price and similar principles intercalate Na+ ions as Li+ ions in lithium-ion batteries. Different materials as manganese oxides and vanadium oxide are used as electrode materials in sodium batteries. Na0.44MnO2 was regarded as one of the most promising cathode materials for sodium-ion batteries due to its high specific capacity and good cyclability. In this work, Na0.4MnO2 was synthesized using glycine-nitrate method (GNM). The structure of synthesized powder was characterized by X-Ray Diffraction (XRD), while the particles morphology was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elemental mapping was performed by energy-dispersive Xray spectroscopy (EDS). XRD results showed that the phase structure of Na0.4MnO2 was orthorhombic with tunnel structure. TEM and SEM micrographs of obtained powder material showed uniformed rod-like shape particles with the average lengths and widths of 300 nm and 80 nm, respectively and EDS analysis confirmed that the sample contains Na, Mn, and O in an appropriate ration. The electrochemical behavior of Na0.4MnO2 was investigated by cyclic voltammetry (CV) in a saturated aqueous solution of NaNO3 at scan rates from 20 to 400 mV•s-1. The initial discharge capacity of Na0.4MnO2 in NaNO3 solution was 50 mA•h•g- 1, while after 15 cycles its value increased for 9%. while the efficiency (the ratio of the capacity charge and discharge) was amounting to ~ 95%. This indicates that material synthesized by GNM can be used as cathode material in aqueous sodium-ion batterie

Hydrogen evolution reaction on bimetallic Ir/Pt(poly) electrodes in alkaline solution

Hydrogen evolution reaction (HER) was studied in alkaline solution on Pt(poly) electrode modified by spontaneously deposited Ir nanoislands. Comprehensive insight into the characteristics of the bimetallic Ir/Pt(poly) catalysts was obtained by a combination of Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS) and classical electrochemical techniques. HER investigations have shown that the presence of spontaneously deposited Ir enhances the activity of bare Pt(poly) in alkaline solution. This was attributed to the heterogeneity of the active surface sites and to the electronic interaction between two metals in close contact which together facilitated the adsorption of the H intermediate species.This is peer-reviewed version of the article: Svetlana Štrbac, Milutin Smiljanić, Thomas Wakelin, Jelena Potočnik, Zlatko Rakočević, Hydrogen evolution reaction on bimetallic Ir/Pt(poly) electrodes in alkaline solution, Electrochimica Acta (2019), [https://dx.doi.org/10.1016/j.electacta.2019.03.100][http://cer.ihtm.bg.ac.rs/handle/123456789/2951

Synthesis temperature influence on the structure, morphology and electrochemical performance of NaxMnO2 as cathode materials for sodium-ion rechearchable batteries

The lithium-ion batteries are the most commonly used for energy storage in portable devices. Since lithium is relatively rare on earth but rapidly consumed, it is necessary to find an adequate replacement. Owing to the similar chemical properties of sodium and lithium, but much higher availability, sodium ion batteries are one of the best candidates to replace lithium-ion batteries. A variety of materials such as manganese oxide, vanadium oxide or phosphate can be used as an electrode material (anode and cathode) in sodium ion batteries due to the high ability of intercalation of sodium. In this work, NaxMnO2 powder was synthesized by glycine nitrate method. The precursor powder was annealed for four hours at different temperatures: 800, 850, 900 and 950 °C. The characterization of the obtained materials was carried out using following methods: X-ray diffraction (XRD), scanning electron spectroscopy with energy dispersive X-ray spectroscopy (SEM/EDS) and transmission electron spectroscopy with energy dispersive Xray spectroscopy (TEM/EDS). Electrochemical properties were studied using cyclic voltammetry and chronopotentiometry in an aqueous solution of NaNO3. The layer structured Na0.7MnO2.05 with sheet-like morphology and Na0.4MnO2 with 3-D tunnel structure and rod-like morphology was obtained at 800 oC and 900 oC respectively. Na0.44MnO2 with rod-like morphology was annealed at 900 and 950 oC. 3D-tunnel structure Na0.44MnO2 obtained at 900 oC showed the best electrochemical behaviour in aqueous NaNO3 solution

Synthesis and Characterization of Na0.4MnO2 as a Positive Electrode Material for an Aqueous Electrolyte Sodium-ion Energy Storage Device

Due to the increasing use of batteries in everyday life and in industry, there is a need for developing cheaper batteries than the widely used lithium ion batteries. Lower price and higher abundance of sodium compared to lithium mineral resources intensified the development of Na-ion batteries. Aqueous lithium/ sodium rechargeable batteries have attracted considerable attention for energy storage because they do not contain flammable organic electrolytes as commercial batteries do, the ionic conductivity of the aqueous electrolyte is about two orders of magnitude higher than in non-aqueous electrolyte and the electrolyte salt and solvent are cheaper. Various materials such as manganese oxides, vanadium oxide and phosphates have been used as electrode materials (cathodic and anodic) in sodium batteries due to high sodium intercalation ability in both, organic and aqueous electrolytes. The most frequently used type of manganese oxides are Li–Mn–O or Na–Mn–O systems due to their tunnel or layered crystal structures which facilitate the lithium/sodium intercalation-deintercalation. In this work, a glycine-nitrate method (GNM) was applied for the synthesis of cathode material Na0.4MnO2

Anti-Inflammatory Therapy in Coronary Artery Disease: Where Do We Stand?

Inflammation plays an important role in all stages of atherosclerosis — from endothelial dysfunction, to formation of fatty streaks and atherosclerotic plaque, and its progression to serious complications, such as atherosclerotic plaque rupture. Although dyslipidemia is a key driver of atherosclerosis, pathogenesis of atherosclerosis is now considered interplay between cholesterol and inflammation, with the significant role of the immune system and immune cells. Despite modern therapeutic approaches in primary and secondary cardiovascular prevention, cardiovascular diseases remain the leading cause of mortality worldwide. In order to reduce residual cardiovascular risk, despite the guidelines-guided optimal medical therapy, novel therapeutic strategies are needed for prevention and management of coronary artery disease. One of the innovative and promising approaches in atherosclerotic cardiovascular disease might be inflammation-targeted therapy. Numerous experimental and clinical studies are seeking into metabolic pathways underlying atherosclerosis, in order to find the most suitable pathway and inflammatory marker/s that should be the target for anti-inflammatory therapy. Many anti-inflammatory drugs have been tested, from the well-known broad range anti-inflammatory agents, such as colchicine, allopurinol and methotrexate, to targeted monoclonal antibodies specifically inhibiting a molecule included in inflammatory pathway, such as canakinumab and tocilizumab. To date, there are no approved anti-inflammatory agents specifically indicated for silencing inflammation in patients with coronary artery disease. The most promising results came from the studies which tested colchicine, and studies where the inflammatory-target was NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome/interleukin-1 beta (IL-1β)/interleukin-6 (IL-6)/C-reactive protein (CRP) pathway. A growing body of evidence, along with the ongoing clinical studies, suggest that the anti-inflammatory therapy might become an additional strategy in treating atherosclerotic cardiovascular disease. Herein we present an overview of the role of inflammation in atherosclerosis, the most important inflammatory markers chosen as targets of anti-inflammatory therapy, along with the critical review of the major clinical trials which tested non-targeted and targeted anti-inflammatory drugs in patients with atherosclerotic cardiovascular disease

An aggressive chondroblastoma of the knee treated with resection arthrodesis and limb lengthening using the Ilizarov technique

This case report describes the management of a 15 year old male with a biologically aggressive chondroblastoma of the knee. Following CT, bone scan, angiography and an open biopsy, the diagnosis was confirmed histologically and immunohistochemically. The patient underwent a 13 cm en-bloc excision of the knee, and knee arthrodesis with simultaneous bone transport using an Ilizarov ring fixator. Following 136 days of bone transport, the patient achieved radiological and clinical bony union after a total frame time of 372 days. He then commenced 50% partial weight-bear in a protective knee brace and gradually worked up to full weight-bearing by 4 months. The patient developed superficial pin tract infections around the k-wires on 2 occasions; these settled with a cephalosporin antibiotic spray and local dressings. At 13 years follow-up there are no signs of disease recurrence or failure at the fusion site. The patient is able to fully weight bear and stand independently on the operated leg. Knee arthrodesis with simultaneous limb-lengthening is an effective treatment modality following en-bloc resection of an aggressive chondroblastoma. The case is discussed with reference to the literature