Transmission Electron Microscopy Studies Research Articles

Investigating Charge-Induced Transformations of Metal Nanoparticles in a Radically-Inert Liquid: A Liquid-Cell TEM Study

We present a novel in situ liquid-cell transmission electron microscopy (TEM) approach to study the behavior of metal nanoparticles under high-energy electron irradiation. By utilizing a radically-inert liquid environment, we aim to minimize radiolysis effects and explore the influence of charge-induced transformations. We observed complex dynamics in nanoparticle behavior, including morphological changes and transitions between amorphous and crystalline states. These transformations are attributed to the delicate interplay between charge accumulation on the nanoparticles and enhanced radiolysis, suggesting a significant role for charge-assisted processes in nanoparticle evolution. Our findings provide valuable insights into the fundamental mechanisms driving nanoparticle behavior at the nanoscale and demonstrate the potential of liquid-cell TEM for studying complex physicochemical processes in controlled environments.

Covalent Carbide Interconnects Enable Robust Interfaces and Thin SEI for Graphite Anode Stability under Extreme Fast Charging.

Carbonaceous and carbon-coated electrodes are ubiquitous in electrochemical energy storage and conversion technologies due to their electrochemical stability, lightweight nature, and relatively low cost. However, traditional reliance on conductive additives and binders leads to impermanent electrical pathways. Here, a general approach is presented to fabricate robust electrodes with a progressive failure mechanism by introducing carbide-based interconnects grown via carbothermal conversion of (5 wt%) titanium hydride nanoparticles. This method concurrently enhances both electrical and mechanical properties within the electrode architecture. The resulting chemical bonding between active materials establishes a novel mechanism to maintain stable electrical pathways during cycling. Employed as Li-ion battery anodes, these electrodes exhibit improved cyclability, achieving 80% capacity retention after 800 fast-charge cycles at moderate loading (1 mAh cm- 2). High loading cells with areal capacity of 3 mAh cm-2 show significantly improved cycle lifeover the same number of cycles. This performance improvement is attributed to the absence of significant impedance growth and a thinner solid electrolyte interphase (SEI) layer formed at high current densities (4C) as demonstrated by X-ray photoelectron spectroscopy and transmission electron microscopy studies. The enhanced conductivity facilitates SEI formation, lowering ionic impedance and mitigating lithium plating, ultimately leading to the reported extended cycle life.

Development of a selective COX-2 inhibitor: from synthesis to enhanced efficacy via nano-formulation.

Non-steroidal anti-inflammatory drugs NSAIDs are widely used for managing various conditions including pain, inflammation, arthritis and many musculoskeletal disorders. NSAIDs exert their biological effects by inhibiting the cyclooxygenase (COX) enzyme, which has two main isoforms COX-1 and COX-2. The COX-2 isoform is believed to be directly related to inflammation. Based on structure-activity relationship (SAR) studies of known selective COX-2 inhibitors, our aim is to design and synthesize a novel series of 2-benzamido-N-(4-substituted phenyl)thiophene-3-carboxamide derivatives. These derivatives are intended to be selective COX-2 inhibitors through structural modification of diclofenac and celecoxib. The compound 2-benzamido-5-ethyl-N-(4-fluorophenyl)thiophene-3-carboxamide VIIa demonstrated selective COX-2 inhibition with an IC50 value of 0.29 μM and a selectivity index 67.24. This is compared to celecoxib, which has an IC50 value of 0.42 μM and a selectivity index 33.8. Molecular docking studies for compound VIIa displayed high binding affinity toward COX-2. Additionally, the suppression of protein denaturation with respect to albumin was performed as an indicative measure of the potential anti-inflammatory efficacy of the novel compounds. Compound VIIa showed potent anti-inflammatory activity with 93% inhibition and an IC50 value 0.54 μM. In comparison, celecoxib achieved 94% inhibition with an IC50 value 0.89 μM. Although molecule VIIa demonstrated significant in vitro anti-inflammatory activity, adhered to Lipinski's "five rules" (RO5) and exhibited promising drug-like properties, it showed indications of poor in vivo activity. This limitation is likely due to poor aqueous solubility, which impacts its bioavailability. This issue could be addressed by incorporating the drug in niosomal nanocarrier. Niosomes were prepared using the thin-film hydration technique. These niosomes exhibited a particle size of less than 200 nm, high entrapment efficiency, and an appropriate drug loading percentage. Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) studies revealed that the niosomes were spherical and demonstrated compatibility of all of its components. The drug release study indicated that the pure drug had limited practicality for in vivo use. However, incorporating the drug into niosomes significantly improved its release profile, making it more suitable for practical use.

Achieving the 1D Atomic Chain Limit in Van der Waals Crystals.

Experiments with graphene have demonstrated that 2D van der Waals materials can be stable, robust, and efficiently manipulated at the level of individual atomic planes. However, the stability and manipulation of 1D van der Waals materials and individual atomic chains remains elusive. Here, the ability to exfoliate and process two representative van der Waals materials containing 1D motifs, namely MoI3 and Ta2Se8I, at the scale of individual atomic chains is demonstrated. High-resolution transmission electron microscopy and atomic force microscopy studies confirm the presence of stable individual atomic chains of MoI3 at room temperature. It is further shown that 1D van der Waals materials with low exfoliation energy, such as Ta2Se8I, can be processed with electron beams to achieve suspended individual atomic chains. Ab initio calculations corroborate the findings regarding the cleavage energies and the thermodynamic stability of individual atomic chains in these 1D van der Waals materials. These results demonstrate that the top-down approach in material processing can be extended to the scale of individual chains.

Using In situ Transmission Electron Microscopy to Study Strong Metal-Support Interactions in Heterogeneous Catalysis.

Precisely controlling the microstructure of supported metal catalysts and regulating metal-support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal-support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided.

Cytocompatible Hyperbranched Polyesters Capable of Altering the Ca2+ Signaling in Neuronal Cells In Vitro.

Synthetic hyperbranched polyesters with potential therapeutic properties were synthesized using the bifunctional polyethylene glycol or PEG with different molecular weights, ca., 4000, 6000, and 20,000 g/mol, and the trifunctional trans-aconitic acid or TAA. During polycondensation, a fixed amount of PEG was allowed to react with varying amounts of TAA (1:1 and 1:3) to control the branching extents. It was found that the synthetic polyesters had a considerable yield and were highly water soluble. Spectroscopic data (Fourier transform infrared and 1H NMR) confirmed the polyester formation; the branching percentages were determined from 1H NMR spectroscopy which varied from 73% to 22% among the synthesized samples. As the molecular weight of PEG was increased, the branching percentage drastically dropped. All polyesters were found to be negatively charged due to the ionization of unreacted -COOH in the branched ends at the working pH (7.4). Both the hydrodynamic size and intrinsic viscosity were found to reduce as the branching extent increased. Among the sets of polyesters, the one with the highest branching percentage (73%) showed the core-shell morphology (evident from field emission scanning electron microscopy and transmission electron microscopy studies). It also exhibited the highest efficiency toward Ca2+ influx in neuronal cells due to the unique morphology and the negatively charged surface. Nevertheless, this particular grade of polyester along with all the other grades was cytocompatible and induced reactive oxygen species generation. Since the maximally branched grade was highly efficient in altering the Ca2+ signaling through stronger influx, it may well be tested for treating neuronal disorders in vivo in future.

Synthesis of a dehydrodieugenol B derivative as a lead compound for visceral leishmaniasis-mechanism of action and in vivo pharmacokinetic studies.

Leishmaniasis is a parasitic neglected tropical disease, affecting 12 million people. Available treatments present several limitations, with an increasing number of resistance cases. In the search for new chemotherapies, the natural product dehydrodieugenol B was used as a scaffold for the synthesis of a series of derivatives, resulting in the discovery of the promising analog [4-(4-(5-allyl-3-methoxy-2-((4-methoxybenzyl)oxy)phenoxy)-3-methoxybenzyl)morpholine, 1]. In this work, we investigated the effect of compound 1 on cell signaling in Leishmania (L.) infantum, culminating in cell death, as well as its immunomodulatory effect in the host cell. Additionally, we performed a pharmacokinetic profile study in an animal model. After treatment, compound 1 induced the alkalinization of acidocalcisomes and concomitant Ca2+ release in the parasite. These events may induce depolarization of the mitochondrial potential, with successive collapse of the bioenergetic system, leading to a reduction of ATP and reactive oxygen species (ROS) levels. The analysis of total proteins and protein profile by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) demonstrated that compound 1 also altered the parasite proteins after treatment. Transmission electron microscopy studies revealed ultrastructural damage to mitochondria; together, these data suggest that compound 1 may promote autophagic cell death. Additionally, compound 1 also induced an immunomodulatory effect in host cells, with a reduction of Th1 and Th2 cytokine response, characterizing an anti-inflammatory compound. The obtained pharmacokinetic profile in rats enhances the potential of the compound, with a mean plasma half-life (T1/2) of 21 h. These data reinforce the potential of compound 1 as a new lead for future efficacy studies.

Er3+/Tm3+ codoped CaF2 based oxyfluoroborosilicate glass-ceramics for fiber laser applications

Transparent Er3+/Tm3+ codoped CaF2 based oxyfluoroborosilicate glass-ceramics (BSEr1TmxGCs) with variable Tm3+ concentration were prepared through melt quench process followed by reheat treatment at 450 °C/1h. They were characterized through differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) Raman spectroscopy, near infrared (NIR) emission and luminescence decay. The formation of CaF2 nanocrystallites against oxyfluoroborosilicate glassy phase was confirmed by scanning electron microscopic (SEM) and hi-resolution transmission electron microscopic (HRTEM) studies. The NIR emission properties were investigated at 460 nm diode laser pumping. The applicability of BSEr1TmxGCs were examined by evaluating effective bandwidth (Δλeff), stimulated emission cross-section (σe), gain bandwidth (σe × Δλeff), figure of merit (σe × τR) and quantum efficiency (ηQE). The energy transfer efficiency (ηET), rate of energy transfer (WET) between Er3+ and Tm3+ and the rate of non-radiative transitions (WNR) were also calculated. The comparative NIR emission performance suggests that the BSEr1Tm1GC has proficiency for 1530 nm broadband fiber lasers and optical amplifiers in short wavelength and conventional wavelength (S + C) band communication window.

A detailed characterization study of Ni/CeO2 catalysts identifies Ni availability as the primary factor affecting CO2 methanation performance

The structure of a catalyst has a strong impact on its performance. Here we investigate the physicochemical properties of Ni/CeO2 in an attempt to draw structure–activity relationships for CO2 methanation. A combination of characterisation methods (X-ray diffraction (XRD), 4D Scanning Transmission Electron Microscopy (4D-STEM), CO chemisorption and oxygen storage capacity study etc.) clearly demonstrates the effect of Ni crystallite size, Ni availability (i.e. catalytically accessible Ni) and oxygen vacancies at the Ni-CeO2 interface in Ni/CeO2 during CO2 methanation. Among them, the role of exposed Ni active sites is highlighted, and two possible optimisation schemes i.e. changing the support calcination temperature and the final calcination atmosphere are proposed to obtain a better dispersal of Ni NPs (nanoparticles) on CeO2. Both modification methods do not affect the reaction route, and the activity differences of Ni/CeO2 can be explained by the various hydrogenation rate of formate species, as confirmed by in situ diffuse-reflectance infrared Fourier-transform spectroscopy (DRIFTS) measurements.

In-Situ TEM study of microstructural evolution in proton irradiated single crystal UO2 under high-temperature annealing

Understanding microstructural changes in nuclear fuels under different irradiation conditions is important as it directly affects thermal, oxidation and mechanical properties and thereby reactor safety and longevity. This work focuses on the effect of temperature on the evolution of extended defects in uranium dioxide. In-situ transmission electron microscopy (TEM) annealing of proton irradiated UO2 was performed at different temperatures: 900 °C, 1100 °C and 1300 °C, 1 hour for each temperature. Microstructural evolution in terms of dislocation loops and voids were captured using in-situ TEM during annealing at different temperatures. Post-annealing at each temperature, detailed characterization using rel-rod dark field, bright field, and underfocus-overfocus imaging in TEM were used to identify faulted loops, perfect dislocation loops, and voids, respectively. Dislocation loops showed migration, disappearance, coalescence and loop-line interactions which significantly contributed to the recovery process during annealing at temperatures of 1100 °C and 1300 °C. Small voids were observed at 900 °C (diameter ∼ 0.5–1.5 nm) and grew rapidly during 1300 °C annealing (diameter ∼ 1–3 nm). Void growth was attributed to vacancy absorption, Ostwald ripening and void coalescence mechanisms. Extensive void growth was unique to in-situ TEM annealing due to free surface effect as ex-situ annealing confirmed negligible TEM resolvable (> 0.5 nm) voids at 1300 °C. The dislocation loops and voids behavior during in-situ TEM annealing were compared with rate theory and cluster dynamics predictions.

In-situ observation of defects evolution of graphene nanoflakes in Pt/C catalyst for boosting ORR performance

The structural stability of supported metal nanoparticles determines the activity and longevity of heterogeneous catalysts. Unfortunately, the chemical/thermal working environment inevitably accelerates metal sintering to larger crystallites that leads to the degradation of catalytic performance. Here, we demonstrate that the distribution of defects in carbon support as an inherent parameter plays a crucial role in catalyst sintering. Based on in-situ transmission electron microscopy studies, the strong metal-support interaction between platinum (Pt) nanoparticles and defect-rich graphene nanoflakes largely suppresses metal sintering up to 700 °C. Particularly, the optimal carbon support can be achieved in the annealing process, in which the mass transfer and charge transport can be enhanced by accurately manipulating the distribution of defects in carbon matrix and graphitization degree. It is worth noting that the screened Pt/GNs-300 exhibits impressive oxygen reduction reaction performance with high half-wave potential (0.91 V), mass activity (108.1 A g–1Pt) and excellent stability. By its ascendancy in ORR, the Pt/GNs-300 exhibits a high open-circuit voltage of 1.41 V and a maximum power density of 198.6 mW cm−2 in Zn-air battery, implying its brilliant practicability. This work paves a pathway for achieving sinter-resistant metal-loaded catalysts in energy electrocatalysis.

Encapsulation of Ru nanoparticles within NaY zeolite for ammonia decomposition

Uniform and minuscule Ru particles confined in NaY zeolite (Ru@NaY) are prepared via a simple in situ synthesis technique. Transmission electron microscopy studies indicate that the Ru particles are encapsulated within the micropores of NaY zeolite and form a uniform size of 1.5–3.5 nm. Thanks to the effective confinement of Ru particles within the NaY zeolite, as well as the high concentration of B-5 sites and basic sites, the prepared Ru@NaY catalysts show excellent NH3 decomposition activity and highly efficient H2 formation. Notably, the 0.1Ru@NaY catalyst achieves a 92.7% NH3 conversion and a H2 formation rate of 690 mmol min−1·gRu−1 at 500 °C and GHSV = 9000 mLNH3·gcat−1·h−1 and shows outstanding stability throughout a 95-h lifetime test. The encapsulation synthesis of Ru clusters in zeolites endows the catalysts with exceptional catalytic activities and excellent stability, thus providing new prospects for the production of H2 from NH3 decomposition.

Ultrastructural Analysis of the Large Neuronal Perikarya in an Injured Dentate Nucleus Using an Experimental Model of Hyperthermia-Induced Convulsions: The First Qualitative and Quantitative Study.

Background: Febrile seizures are a common form of convulsions in childhood, with poorly known cellular mechanisms. The objective of this pioneering study was to provide qualitative and quantitative ultrastructural research on the large neuronal perikarya in the cerebellar dentate nucleus (DN), using an experimental model of hyperthermia-induced seizures (HSs), comparable to febrile seizures in children. Methods: The study used young male Wistar rats, divided into experimental and control groups. The HSs were evoked by a hyperthermic water bath at 45 °C for 4 min for four consecutive days. Specimens (1 mm3) collected from the DN were routinely processed for transmission electron microscopy studies. Results: The ultrastructure of the large neurons in the DN affected by hyperthermic stress showed variously pronounced lesions in the perikarya, including total cell disintegration. The most pronounced neuronal lesions exhibited specific morphological signs of aponecrosis, i.e., dark cell degeneration ('dark neurons'). In close vicinity to the 'dark neurons', the aponecrotic bodies were found. The findings of this qualitative ultrastructural study correspond with the results of the morphometric analysis of the neuronal perikarya. Conclusions: Our results may constitute interesting comparative material for similar submicroscopic observations on large DN neurons in HS morphogenesis and, in the future, may help to find potential treatment targets to prevent febrile seizures or reduce recurrent seizures in children.

Using In situ Transmission Electron Microscopy to Study Strong Metal‐Support Interactions in Heterogeneous Catalysis

AbstractPrecisely controlling the microstructure of supported metal catalysts and regulating metal‐support interactions at the atomic level are essential for achieving highly efficient heterogeneous catalysts. Strong metal‐support interaction (SMSI) not only stabilizes metal nanoparticles and improves their resistance to sintering but also modulates the electrical interaction between metal species and the support, optimizing the catalytic activity and selectivity. Therefore, understating the formation mechanism of SMSI and its dynamic evolution during the chemical reaction at the atomic scale is crucial for guiding the structural design and performance optimization of supported metal catalysts. Recent advancements in in situ transmission electron microscopy (TEM) have shed new light on these complex phenomena, providing deeper insights into the SMSI dynamics. Here, the research progress of in situ TEM investigation on SMSI in heterogeneous catalysis is systematically reviewed, focusing on the formation dynamics, structural evolution during the catalytic reactions, and regulation methods of SMSI. The significant advantages of in situ TEM technologies for SMSI research are also highlighted. Moreover, the challenges and probable development paths of in situ TEM studies on the SMSI are also provided.

Insight into the Internal Structure of High-Performance Multicore Magnetic Nanoparticles Used in Cancer Thermotherapy.

Multicore magnetic nanoparticles (MNPs), comprising iron oxide cores embedded in a sugar or starch matrix, are a class of nanomaterials with promising magnetic heating properties. Their internal structure, and particularly the strength of the internal core-core magnetic interactions, are believed to determine the functional properties, but there have been few detailed studies on this to date. We report here on an interlaboratory and multimodality transmission electron microscopy (TEM) and magnetic study of a high-performance MNP material (supplied by Resonant Circuits Limited, RCL) that is currently being used in a clinical study for the treatment of pancreatic cancer. TEM data were collected under a variety of conditions: conventional; high-resolution; scanning; cryogenic; and, for the first time, liquid phase. All the imaging modes showed mostly irregular dextran lamellae of lateral dimensions 30-90 nm, plus ca. 15% n/n of what appeared to be 30-60 nm long "nanorods", and a multitude of well-dispersed ca. 3.7 nm diameter iron oxide cores. Cryogenic electron tomography indicated that the nanorods were edge-on lamellae, but in dried samples, tomography showed rod- or lath-shaped forms, possibly resulting from the collapse of lamellae during drying. High-resolution TEM (HRTEM) showed the dextran to be crystallized in the low-temperature hydrated dextran polymorph. Magnetic remanence Henkel-plot analysis indicated a weak core-core interaction field of ca. 4.8 kA/m. Theoretical estimates using a point-dipole model associated this field with a core-to-core separation distance of ca. 5 nm, which tallies well with the ca. 4-6 nm range of separation distances observed in liquid-cell TEM data. On this basis, we identify the structure-function link in the RCL nanoparticles to be the unusually well-dispersed multicore structure that leads to their strong heating capability. This insight provides an important design characteristic for the future development of bespoke nanomaterials for this significant clinical application.

α-Bi2O3 tubular rods coated on Bi2O2CO3 nanosheets for high-performance asymmetric supercapacitor applications

Mixed phases of bismuth oxide nanostructures as an active electrode material in supercapacitor applications have recently gained huge research interest. In this study, the layered Bi2O2CO3 nanosheets and the secondary phase of α-Bi2O3 tubular rods named Bi2O2CO3/α-Bi2O3 heterostructure have been synthesized and utilized for supercapacitor applications. The crystal nature and microstructure of the Bi2O2CO3/α-Bi2O3 heterostructure were initially confirmed by powder X-ray diffraction (p-XRD), Raman, UV-Vis diffuse reflectance spectroscopy (UV-DRS, absorbance), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies. X-ray photoelectron spectroscopy (XPS) measurements have investigated the oxidation states and chemical binding energies. Regarding the electrochemical performances, the Bi2O2CO3/α-Bi2O3 heterostructure as electro-active material delivered a maximum specific capacitance (Cs) value of 635 F g−1 at the given current density value of 1 A g−1 in a conventional three-electrode mode. A coin cell type electrode has been fabricated using Bi2O2CO3/α-Bi2O3 heterostructure, resulting in an asymmetric supercapacitor device cell (ASC), which has a Cs of 112 F g− 1 (at 1 A g− 1) and a power density and energy density values of 515 W kg−1 and 22.5 Wh kg−1 respectively. The two supercapacitor electrodes in sequence effectively ignite the red-light-emitting diode (LED). Moreover, in the ASC type Bi2O2CO3 /α-Bi2O3 heterostructure, the specific capacitance value was slightly reduced to 12.3 % by 2000 cycles, showing favourable cyclic performance and stability during the electrochemical process. Based on the above-mentioned characterization, the appropriate electrochemical performances of Bi2O2CO3/α-Bi2O3 tubular rod heterostructures make them a promising candidate for future energy storage devices.

RETRACTION: Preventive Effect of Naringin on Cardiac Mitochondrial Enzymes During Isoproterenol-induced Myocardial Infarction in Rats: A Transmission Electron Microscopic Study.

M. Rajadurai and P. Stanely Mainzen Prince, "Preventive Effect of Naringin on Cardiac Mitochondrial Enzymes During Isoproterenol-induced Myocardial Infarction in Rats: A Transmission Electron Microscopic Study," by Journal of Biochemical and Molecular Toxicology 21, no. 6 (2007): 354-361, https://doi.org/10.1002/jbt.20203. The above article, published online on 9 November 2007 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor-in-Chief, Hari K. Bhat; and Wiley Periodicals, LLC. The retraction has been agreed due to duplication of panels presented in figure 3b and 3 f. The authors did not provide an explanation or their raw data. The editors consider the results and conclusion reported in this article unreliable.

Histochemical and ultrastructural localization of triterpene saponins in Medicago truncatula.

In the Medicago genus, saponins are complex mixtures of triterpene pentacyclic glycosides extensively studied for their different and economically relevant biological and pharmaceutical properties. This research is aimed at determining for the first time the tissue and cellular localization of triterpene saponins in vegetative organs of Medicago truncatula, a model plant species for legumes, by histochemistry and transmission electron microscopy. The results showed that saponins are present mainly in the palisade mesophyll layer of leaves, whereas in stems they are mostly located in the primary phloem and the subepidermal cells of cortical parenchyma. In root tissue, saponins occur in the secondary phloem region. Transmission electron microscopy revealed prominent saponin accumulation within the leaf and stem chloroplasts, while in the roots the saponins are found in the vesicular structures. Our results demonstrate the feasibility of using histochemistry and transmission electron microscopy to localize M. truncatula saponins at tissue and cellular levels and provide important information for further studies on biosynthesis and regulation of valuable bioactive saponins on agronomic relevant Medicago spp., such as alfalfa (Medicago sativa L.). RESEARCH HIGHLIGHTS: The Medicago genus represents a valuable rich source of saponins, one of the most interesting groups of secondary plant metabolites, which possess relevant biological and pharmacological properties. Plant tissue and cellular localization of saponins is of great importance to better understand their biological functions, biosynthetic pathway, and regulatory mechanisms. We elucidate the localization of saponins in Medicago truncatula with histochemical and transmission electron microscopy studies.

Enhanced oxygen reduction reaction with rare-earth metal-based Ce-N-C catalyst

An atomically dispersed single atom catalyst based on rare-earth metal, Cerium embedded into the porous N-doped carbon (Ce-N-C), has been synthesized by using metal-organic framework method. The Ce-N-C catalyst have been physiochemically and electrochemically characterized in detail. Transmission electron microscope studies revealed atomically dispersed Ce atoms on the N-doped carbon support. The electrochemical oxygen reduction reaction (ORR) kinetics of Ce-N-C-3 catalyst revealed an admirable activity with a half-wave potential of 0.89 V, nearly equal to state-of-the-art Pt/C catalyst. The K-L plots and RRDE measurements revealed a nearly direct 4 electron reduction of O2 to H2O by Ce-N-C-3 catalyst. In addition, the chronoamperometry studies with a simulated H2O2 environments clearly revealed the significance of Ce3+/Ce4+ redox couple in deactivating hydrogen peroxide and/or hydroperoxide radicals. The commendable ORR activity, stability and peroxide resistance of Ce-N-C-3 catalysts is credited to the high surface area, atomically dispersed Ce atoms, formation of Ce-N4-C active sites in the catalysts, evidenced from the XPS analysis, in addition to the significance of Ce3+/Ce4+ redox couple in the catalyst. Most importantly, chronoamperometric studies revealed clear evidence of Ce3+/Ce4+ couple significance, helping in effectively mitigating the peroxide related detrimental effects to the ORR catalyst.

Synthesis and Characterization of Gold Nanoparticles and Gold Nanoparticles Loaded with Bromelain

The production and use of nanometallic elements, such as gold, have received a lot of attention lately due to their distinctive features and wide range of uses. Most of these studies have employed the Turkevich approach. This research employed the Turkevich technique to produce gold nanoparticles (AuNPs). AuNPs and bromelain-loaded AuNPs were characterised using a variety of methods, including ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and zeta potential (ZP) measurements. The UV-Vis spectra of Bromelain, AuNPs, and AuNPs-Bromelain each had a peak at 276, 534, and 550 nm wavelengths, respectively. The FE-SEM and TEM studies revealed the presence of spherical particles with a smooth surface. The diameters of the AuNPs ranged from 49.32 to 77.29 nm; the diameters of the Bromelain-AuNPs ranged from 46.39 to 75.66 nm, as determined by the FE-SEM analysis. The TEM analysis indicated that the particles' sizes ranged from 7.40 to 15 nm for AuNPs and 14.51 nm for AuNPs-Bromelain. The XRD patterns revealed numerous diffraction peaks, indicating the crystal structure of the synthesised nanoparticles. FTIR spectrometry was employed to identify the functional groups in the synthesised nanoparticles. Zeta potential (ZP) measurements revealed that AuNPs had a zeta potential value of +0.1±0.4, and the zeta potential value for AuNPs-Bromelain was +1.2±3.0 mV.