Field Emission Gun Scanning Electron Microscopy Research Articles

Fabrication of Free‐Standing Hybrid Composite High Capacity Cathodes for Li−S Batteries with Nickel Oxide Polysulfide Adsorbent

AbstractThis study focuses on enhancing lithium‐sulfur (Li−S) battery performance by using nickel(II) oxide (NiO), as polysulfide adsorbent to mitigate the shuttle effect. Polysulfides have been shown to effectively adsorb onto the hydrophilic surfaces of polar metal oxides and thus suppress this effect. In this work, a NiO – reduced Graphene Oxide/Sulfur (NiO‐rGO/S) hybrid composite paper was developed for use as a binder‐free, flexible cathode. The characterization of the composite films was done through Fourier transform infrared spectroscopy (FT‐IR), Raman spectroscopy, thermogravimetric analysis (TG), field emission gun scanning electron microscopy (FEG‐SEM), energy dispersive x‐ray spectroscopy (EDS) and x‐ray diffraction (XRD). To test adsorption of polysulfides by NiO, ultraviolet‐visible (UV‐Vis) spectroscopy was applied. Electrochemical performance tests of CR2032 cells were also conducted by cyclic voltammetry (CV), charge‐discharge tests, electrochemical impedance spectroscopy (EIS). The NiO‐rGO/S cathode, particularly the one containing 2 % NiO, exhibited remarkable performance. It delivered an initial discharge capacity of 1230 mAh g−1, maintaining 1029 mAh g−1 after 300 cycles, with a high capacity retention of 83.1 %. This suggests that the NiO‐rGO/S hybrid composite is a promising candidate for improving the efficiency and lifespan of Li−S batteries.

Historical Drugs in Transylvania: Disclosing the Composition of Ointments from the "History of Pharmacy Collection" in Cluj-Napoca Through a Multi-Analytical Approach.

The National Museum of Transylvanian History in Cluj-Napoca, Romania, features a History of Pharmacy Collection that documents the evolution of pharmacies in the region since the 16th century. Within the "Pharmatrans" project (2021-2023), we investigated the chemical composition of ointments from fourteen historical pharmaceutical containers dating back to the 18th and 19th centuries. Most samples were from an aristocratic traveling medicine chest, a key artifact in the collection. This study marks the first extensive analysis of historical pharmaceutical formulations in Romania, enhancing our understanding of these valuable items. The main ingredients of formulations were characterized using gas chromatography-mass spectrometry (GC-MS), solid-phase microextraction-GC-MS (SPME-GC-MS), and pyrolysis-GC-MS (Py-GC-MS). Additionally, high-performance liquid chromatography coupled with high-resolution mass spectrometry (HPLC-ESI-Q-ToF) was employed for the detailed analysis of lipid materials and polar compounds. Elemental analysis was conducted using field emission gun-scanning electron microscope (FEG-SEM) with energy-dispersive spectroscopy (EDS). The results revealed that twelve out of fourteen mixtures contained interpretable organic content, often aligning with the vessels' labels. The findings indicate that Transylvanian elites in the late 18th century had access to both rare drugs and traditional remedies, reflecting contemporary trends in pharmacy.

Effect of annealing conditions on resistive switching in hafnium oxide-based MIM devices for low-power RRAM

Abstract This work presents resistive switching (RS) behaviour in HfO2-based low-power resistive random-access memory (RRAM) devices. A metal-insulator-metal (MIM) structure (Au/HfO2/Pt) was fabricated by sandwiching a thin insulating layer of HfO2 between Pt and Au electrodes. HfO2 films deposited by RF sputtering at room temperature were rapid thermally annealed in N2 ambient at 400 °C and 500 °C. Grazing angle x-ray diffraction (GIXRD), Field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) were employed to analyse the phase, crystal structure, morphology, surface roughness and chemical composition of the HfO2 films. The bipolar RS could be observed in both as-deposited and annealed HfO2 film-based devices from I–V characteristics measured using a source meter. We have investigated the effect of annealing temperature and annealing ambient on the phase formation of HfO2 as well as the RS characteristics and compared with as-deposited film-based device. Annealed HfO2 film-based devices exhibited improved electrical characteristics, including stable and repeatable RS at significantly lower switching voltages (<1 V) which indicates low power consumption in these devices. The relatively lower processing temperature of the HfO2 films and that too in the films deposited by physical vapor deposition (PVD) technique-RF magnetron sputtering makes this study significantly useful for resistive switching based non-volatile memories.

PLA/PCL polymer nanocomposite with silver and copper nanoparticles and lavender essential oil: Synthesis, characterization and application in tissue engineering

The present work aims to synthesize, characterize, and evaluate the cytotoxicity and antimicrobial activity of PLA/PCL polymeric nanocomposite with silver nanoparticles (AgNPs) and copper (CuNPs) and the addition of lavender essential oil (LEO) for application in tissue engineering. For the synthesis of the nanocomposite films, the central composite rotational design (CCRD 2²) was used, where the ideal condition was 0 .5 %wt. of AgNPs and CuNPs (3:1D) with a higher cell viability (196.1 %) after 24 h. After defining the ideal condition, the effect of incorporating LEO into the polymer blend and nanoparticles in the proportions of 0.5 (3:1D0.5), 0.75 (3:1D0.75) and 1 v-1 (3:1D1) was evaluated. All nanocomposite films were characterized structurally, morphologically, thermally, and mechanically by X-ray diffraction (XRD), Field Emission Gun–Scanning Electron Microscopy (FEG-SEM), Thermogravimetric analysis (TGA), contact angle and mechanical Properties (displacement and maximum tension). To evaluate cytotoxicity, an in vitro safety profile was performed in HFF-1 (fibroblasts) and HaCat (keratinocytes) cell lines, where PLA/PCL polymer blend with 0.5 %wt. of AgNPs and CuNPs (3:1D) and PLA/PCL polymer blend with 0.5 %wt. of AgNPs and CuNPs and LEO (0.5 v-1) (3:1D0.5) nanocomposite film showed the best cell viability without the nitric oxide (NO) generation, total levels of reactive oxygen species (ROS) or dsDNA release for the HFF-1 and HaCat cell lines, as well as genoprotective characteristic and without genotoxic profile. Moreover, the tests were carried out on the pH of injured skin at different immersion times (3, 6, 12 and 24 h) and didn´t show cell death or inflammatory reaction. For the antimicrobial activity, the 3:1D, 3:1D0.5, and PLA/PCL polymer blend with 0.5 %wt. of AgNPs and CuNPs and LEO (0.75 v-1) (3:1D0.75) nanocomposite films showed the formation of biofilm for S. aureus, E. coli, P. aeruginosa and K. pneumoniae. Therefore, the PLA/PCL polymer nanocomposite with AgNPs and CuNPs showed potential application as a healing dressing for skin regeneration.

Ultramarine blue containing paint layers: Further study of the photo-catalytic degradation of binding media

Photo-catalytic degradation of a linseed oil binder by natural ultramarine (Lapis Lazuli or Lazurite) and Sodalite in paint layers was studied. Both pigments degrade the binder under xenon arc exposure, leading to erosion of the binder at the surface, increased roughness, light scattering and desaturation of the color. Both pigments behave similarly to synthetic ultramarine blue studied earlier. The results for Sodalite provide further proof that the zeolitic nature of the aluminosilicate cage causes the catalytic degradation and that the enclathrated polysulfur radical anions S2-. and S3-. trapped inside the cage are not responsible for the catalytic action. Relatively stable synthetic binders are less affected by the presence of synthetic ultramarine blue. The paints were aged in a xenon arc apparatus using a simulated indoor environment (radiation > ca. 320 nm). The samples were analyzed using diffuse reflectance spectroscopy in the UV–vis and short wavelength infrared (SWIR) ranges, Raman spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM) and FTIR.

Silica coated N-doped carbon modified with ruthenium nanoparticles: An effective waste derived carbon nanocatalyst in oxidation reactions and also its evaluation by DFT and anti-bacterial studies

This report presents the development of an inexpensive mesoporous nanocatalyst i.e. silica coated N-doped carbon modified with ruthenium nanoparticles (Ru/RuO2@NSAC). The carbon and nanosilica components were derived from waste materials namely waste tea extract and rice husk respectively highlighting the sustainable approach to the synthesis process. The nanocatalyst was thoroughly characterized using various advanced techniques such as Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (P-XRD), Field emission gun-scanning electron microscopy (FEG-SEM), Energy dispersive X-ray analysis (EDX), High resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray resonance fluorescence (XRF) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). These characterizations provided comprehensive insights into the structural features of the nanocatalyst. XPS analysis confirmed the presence of both metallic ruthenium and Ru (IV) on the nanocatalytic support. The particle size of Ru/RuO2@NSAC was determined using Scherrer's equation and came out to be 21.37 nm. This nanocatalyst demonstrated remarkable performance as a robust heterogeneous catalyst for the oxidation of alkylarenes and alcohols to their corresponding carbonyl compounds. It exhibited excellent recyclability, maintaining its activity for up to five consecutive runs. Post-recycling, the catalyst was again characterized by P-XRD and FEG-SEM to ensure its structural integrity. Additionally, the antibacterial activity of Ru/RuO2@NSAC was evaluated against both Gram-positive and Gram-negative bacteria. A density functional theory study was also conducted to support the experimental findings, providing a theoretical basis for the observed catalytic behavior.

Fracture‐mechanical properties of tailored epoxy nanocomposites at elevated temperatures

AbstractAn investigation was conducted to assess the influence of hybridized block‐copolymer (BCP) and core–shell rubber (CSR) particles on the tensile properties, fracture mechanical properties, and toughening mechanisms of a high strength epoxy/anhydride system at elevated temperatures (80°C). Utilizing standard tensile and compact tension (CT) specimens, substantial increases in fracture energy were observed for specimens enhanced with nanoparticles—831% for the 4 wt.% BCP‐toughened system and 600% for the 12 wt.% CSR‐toughened system. Field emission gun–scanning electron microscope imaging indicated that the inclusion of BCP and CSR significantly altered fracture surface morphologies, consistent with the improved mechanical properties. Glass transition temperature (Tg) determined through dynamic mechanical analysis—were not significantly influenced by additive inclusion, presenting a ~1°C decrease for BCP and ~3°C increase for CSR toughened systems relative to the unaltered matrix. Toughening mechanisms induced by the BCP and CSR particles were identified as (a) localized enhanced plastic shear‐band yielding around the particles and (b) cavitation of the particles followed by enhanced plastic void growth in the epoxy matrix. Outcomes from this study highlight the role of BCP and CSR particles in the toughening of epoxy/anhydride systems and provide a comprehensive assessment of their influence on mechanical characteristics at high temperatures.

Anisotropic piezoresistive response of 3D-printed pressure sensor based on ABS/MWCNT nanocomposite

Nanocomposites based on carbon nanotubes (CNTs) are suitable for sensors, due to matrix ability to incorporate nanotube properties. Thus, we developed a low-cost, nanostructured poly(acrylonitrile-butadiene-styrene) (ABS) polymer piezoresistive sensor produced by additive manufacturing. For this, solution layers of acetone, dimethylformamide and CNTs functionalized with carboxylic acid were pulverized on an ABS substrate using an aerograph. Electrical characterization revealed an anisotropic piezoresistive response of the material, induced by the printing lines direction. Field Emission Gun-Scanning Electron Microscopy showed the nanostructured film spreading after five layers of CNTs as well as the random entanglement of nanotubes on parallel and perpendicular 3D-printed ABS substrates. Raman spectroscopy indicated compression and p-type doping of CNTs in interaction with the polymer, as seen mainly by the blueshift of the G and 2D subbands. The results show that the material is promising for pressure sensors, with potential applications in robotic haptic feedback systems.

Easy reversible clustering of gold nanoparticles via pH-Induced assembly of PVP-b-PAA copolymer

The growing demand of novel hybrid organic/inorganic systems with exciting properties has contributed to an increasing need for simplifying production strategies. Here, we report a simple method to obtain controlled three-dimensional hybrid architectures, in particular hybrid supracolloids (hSC), formed by gold nanoparticles and a double hydrophilic block copolymer, specifically the poly(acrylic acid)-block-poly(N-vinyl-2-pyrrolidone) (PAA-b-PVP), directly in aqueous medium. The ubiquitous pH-sensitive poly(acrylic acid) (PAA) block initiates the assembly through pH changes, while the poly(N-vinyl-2-pyrrolidone) block assures the close affinity with the AuNPs. We demonstrate that the formation of hybrid supracolloids (hSC) is the result of the synergetic behavior of the two specific polymeric blocks. Additionally, the entire process shows spontaneous and fast switchability. The nanostructured copolymer behaves like a highly swollen hydrogel and displays a disordered internal structure. The driving force for the association of the copolymer chains is induced by the synergetic effects of the decrease in solubility of the poly(acrylic acid) block and the formation of inter and intra chains hydrogen bonds. These were demonstrated by using small angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation monitoring (QCM-D) and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX). In turn, the AuNPs are randomly spread all over the polymeric matrix, as demonstrated by field emission gun – scanning electron microscopy (FEG-SEM). A correlation analysis reveals the hSC density depends mostly on the initial concentration of AuNPs. These results can inspire the fabrication of more complex structures with multicomponent composition.

Exploring the multifunctional aspects of SrBi2-X(CoFe2O4)XNb2O9 nanocomposite materials emphasizing the structural, elastic, and optical properties

Nanocomposites of SrBi(2-X)(CF)XNb2O9 (SBNCF) (CF=CoFe2O4 for X = 0.0 to 0.5 with a step increment of 0.1) were synthesized using the hydrothermal method and characterized for their structural, morphological, elastic, and optical properties. The incorporation of CF into SrBi2Nb2O9 (SBN) resulted in hybrid composites with tailored properties. X-ray Diffraction (XRD) with Rietveld refinement analysis confirmed the formation of orthorhombic SBN and spinel CF phases. Field Emission Gun Scanning Electron Microscopy (FEG-SEM) revealed that SBN exhibits a plate-like morphology, with the incorporation of CF into the SBN matrix resulting in both plate-like and octahedral-shaped grains. The Brunauer–Emmett–Teller (BET) method was used to determine the pore radius and surface area, both of which were found to have increased, indicating an enhancement in photocatalytic performance. The presence of the constituent elements in the prepared compositions was confirmed by Energy Dispersive Spectroscopy (EDS). Fourier Transform Infrared Spectroscopy (FTIR) spectra were used to determine elastic properties, suggesting potential applications in electronic noise filtering. From Diffuse Reflectance Spectroscopy (DRS), a recognizable semiconducting behavior and band gap bowing were noticed in SBNCF nanocomposites on the obtained energy band gap values (2.20 eV–1.56 eV) compared to the SBN host matrix (3.16 eV). The materials exhibited strong emission peaks at 470 nm, 528 nm, 584 nm, and 703 nm upon the excitation of 425 nm light using Photoluminescence (PL) spectroscopy. The white emission was predominant at room temperature in all the produced samples and the corresponding color temperature values range from 5865.93 K to 7599.05 K from the CIE diagram. The SBNCF materials are promising candidates in photocatalytic reactions and white light-emitting diodes (w-LEDs) based on their enhanced optical properties.

Use of carbon black powder for surface treatment of stainless steel substrates via a low-cost CO2 laser

Nowadays, AISI 304 stainless steel plays a crucial role in industry. However, stainless steel exhibits limited wear resistance as it is used in parts with relative motion. Laser treatment emerges as a promising approach to improve its superficial properties. Using a laser as a heat source presents unique properties for heating surfaces, as the first atomic layers of the material absorb the radiation from the laser beam. In this study, we used a low-cost 100 W CO2 laser with carbon black powder to treat the surface of AISI 304 steels. In addition, the reflectance of irradiation on steel is 90%. We used carbon black powder as a photo-absorbing material for radiation to overcome this obstacle. The characterization included field emission gun–scanning electron microscopy, energy dispersive x ray, microhardness, and pin-on reciprocation tribometer. The results showed a significant increase in surface hardness after laser treatment compared to the untreated substrate at a magnitude of 3.8 times. Elemental mapping analysis revealed carbon's presence on the substrate's surface. In addition to increasing surface hardness, we observed a decrease in the friction coefficient of the laser-treated samples compared to the reference substrate. Finally, it could be concluded that carbon black powder had a triple function; it acted as a photo-absorbent material, a carbon source to increase surface hardness, and a solid lubricant. These results show the predictions of using a low-cost CO2 laser with carbon black powder as an efficient, versatile, and fast alternative.

Production of rGO based hybrid composite buckypaper cathodes by using copper oxide polysulfide adsorbent for Li-S batteries

Lithium-sulfur batteries are particularly noteworthy for applications requiring large capacity and long battery life. Transition metal oxides have emerged as polar host materials for lithium polysulfides to further modulate the bonding energy with polysulfides and increase the coupling density of the electrodes. Polar metal oxides naturally adsorb polysulfides on their hydrophilic surfaces. In this study, the polysulfide adsorbing ability of CuO against the shuttle effect is utilized. For this purpose, copper(II) oxide (CuO) is used as polysulfide adsorbent and CuO - reduced Graphene Oxide / Sulphur (CuO-rGO/S) hybrid composite buckypaper electrodes are produced as cathodes in Li-S batteries without using binders. In this work, optical, morphological and structural analyzes of composite films were carried out by Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analysis, respectively. After the CR2032 button cell was assembled using the produced cathode materials, cyclic voltammetry (CV), charge-discharge performance tests, rate capability and electrochemical impedance spectroscopy (EIS) analyzes were performed to investigate the Li-S battery capacities. With the CuO-rGO/S hybrid composite cathode containing 2 % CuO, a discharge capacity of 1205 mAh g−1 was obtained in the first cycle. At the end of the 1000 cycles, the discharge capacity of the cathode was achieved as high as 696 mAh g−1. As a result, the battery capacity of rGO/S-based composite electrodes has been improved by taking advantage of CuO added to the cathode structure to adsorb polysulfides.

Morphological and Doping Effects on Electrical Conductivity of Aluminum Metal Substrate through Pulsed Electrodeposition Coating of Cu-MWCNT

The demand for more efficient and sustainable electrical systems has driven research in the quest for innovative materials that enhance the properties of electrical conductors. This study investigated the influence of copper (Cu) coating and multi-walled carbon nanotubes (MWCNTs) on aluminum metal substrate through the pulsed electrodeposition technique. Parameters such as the concentration of chemical elements, current, voltage, temperature, time, and electrode spacing were optimized in search of improving the nanocomposite coating. The metallic substrate underwent anodization as surface preparation for coating. Characterization techniques employed included Field Emission Gun—Scanning Electron Microscopy (FEG-SEM) for analyzing coating morphology, Energy-Dispersive X-Ray Spectroscopy (EDS), Raman spectroscopy, and Kelvin probe for obtaining surface electrical conductivity values. Homogeneous dispersion of the Cu-MWCNTs film coating was achieved across the entire surface of the aluminum plate, creating a complex morphology. The doping effect was highlighted by changes in the vibrational characteristics of the nanocomposite, which affected the Raman spectrum dispersion bands. An increase in surface electrical conductivity by ≈52.33% compared to the control sample was obtained. Therefore, these results indicate that the improvement in the material’s electrical properties is intrinsically related to the complex morphology achieved with the adopted Cu-MWCNT nanocomposite coating process.

Characterization of SnO2-based gas sensors to analyze diesel and biodiesel blends

This study analyzed biodiesel blends using sensors constituted by SnO2 pellets with gold interdigitated contacts deposited on the surface. Tin dioxide was synthesized by the polymeric precursor method with further calcination treatment at 500°C, conformed and sintered at three temperatures to form three different samples: 700°C (Sn1), 900°C (Sn2) and 1100°C (Sn3). The samples were analyzed by X-Ray Diffraction, FEG-SEM (Field Emission Gun - Scanning Electron Microscopy), Raman spectroscopy, and electrical measurements. Results confirmed the formation of rutile-type tetragonal cassiterite phase, with quasi-spherical particles a moderate degree of heterogeneity in particle size 30-90 nm). Raman vibrational modes and infrared spectrum also confirmed the presence of tin oxide in high purity rutile phase. Sensorial measurements showed high sensitivity, response, and recovery time in tests with biodiesel/ethanol mixtures, allowing to distinguish between blends with a wide range of composition and serving as a potential device to detect adulterated fuel.

Nutrition Design Modeling Method Development for Adana Origin Maize Starch Granules by Structural and Elemental Analysis

The granules of Adana origin maize starch were treated with thermal, acidic and amylase enzyme degradation processes and examined using the Field Emission Gun – Scanning Electron Microscope (FEG-SEM) to determine the structure analysis and composition modeling. The morphology deformation of the starch granules in shape, surface and size, and elemental analysis peaks and data were determined upon degradation. The microstructure images resulted the occurrence of stretches and slit cracks on the nanoparticle surface and high carbohydrate carbon elemental compound. The degraded amylopectin layers upon the conversion stages were notably presented with high clarity ever published. Investigation of the treated starch granules presented that the granules presented an explicit swelled, splintered and spherical granules model, and a high carbon carbohydrate nutrition model. The swelling and gelling existence temperature of the starch samples were detected as 69 °C.

Synthesis of a Phosphoethanolamine Cellulose Mimetic and Evaluation of Its Unanticipated Biofilm Modulating Properties.

When coordinating and adhering to a surface, microorganisms produce a biofilm matrix consisting of extracellular DNA, lipids, proteins, and polysaccharides that are intrinsic to the survival of bacterial communities. Indeed, bacteria produce a variety of structurally diverse polysaccharides that play integral roles in the emergence and maintenance of biofilms by providing structural rigidity, adhesion, and protection from environmental stressors. While the roles that polysaccharides play in biofilm dynamics have been described for several bacterial species, the difficulty in isolating homogeneous material has resulted in few structures being elucidated. Recently, Cegelski and co-workers discovered that uropathogenic Escherichia coli (UPEC) secrete a chemically modified cellulose called phosphoethanolamine cellulose (pEtN cellulose) that plays a vital role in biofilm assembly. However, limited chemical tools exist to further examine the functional role of this polysaccharide across bacterial species. To address this critical need, we hypothesized that we could design and synthesize an unnatural glycopolymer to mimic the structure of pEtN cellulose. Herein, we describe the synthesis and evaluation of a pEtN cellulose glycomimetic which was generated using ring-opening metathesis polymerization. Surprisingly, the synthetic polymers behave counter to native pEtN cellulose in that the synthetic polymers repress biofilm formation in E. coli laboratory strain 11775T and UPEC strain 700415 with longer glycopolymers displaying greater repression. To evaluate the mechanism of action, changes in biofilm and cell morphology were visualized using high resolution field-emission gun scanning electron microscopy which further revealed changes in cell surface appendages. Our results suggest synthetic pEtN cellulose glycopolymers act as an antiadhesive and inhibit biofilm formation across E. coli strains, highlighting a potential new inroad to the development of bioinspired, biofilm-modulating materials.

Silver nanoparticles from ascorbic acid: Biosynthesis, characterization, in vitro safety profile, antimicrobial activity and phytotoxicity

Skin lesions are caused by the interruption of their functions, causing several possibilities of injury, and affecting the patient's quality of life. Thus, an effective alternative to this problem is the application of metallic nanoparticles with considerable antimicrobial activity, such as silver nanoparticles (AgNPs). In this context, the present study aims to synthesize and characterize AgNPs from l-ascorbic acid (AA) for a possible cutaneous tissue engineering, evaluating the in vitro safety profile (VERO cells line), antimicrobial activity (Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa strains), genotoxicity effect and phytotoxicity (Lactuca sativa and Beta vulgaris L. seeds). The novelty of the present study consists of applying green silver nanoparticles for potential application in skin lesions, followed by the study of toxicity in seeds (phytotoxicity), cells (cytotoxicity and genotoxicity with the in vitro safety profile), and antimicrobial activity. X-ray diffraction (XRD), N2 porosimetry, Field Emission Gun – Scanning Electron Microscope (FEG-SEM), zeta potential (ZP), Scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and Fourier-transform infrared spectroscopy (FT-IR) were used to evaluate the morphological, structural, and textural properties of the AgNPs. XRD diffractogram showed characteristic peaks of a face-centered cubic crystal structure at 38.06° (111); 44.26° (200); 64.45° (220); 77.37° (311) and 81.34° (200). FEG-SEM micrography indicated a predominantly spherical morphology and uniformly distributed structure with an average size of 58.4 ± 19 nm. Moreover, AgNPs demonstrated functional groups characteristics of the reducing agent and the metallic precursor, such as the –OH, –CH, –CO, - CC, and Ag–O stretchings. AgNPs showed SBET = 0.3 ± 0.0085 m2 g−1, Dp = 16.2 ± 10.2 nm, Vp = 0.0008 ± 0.0002 cm³ g−1 and ZP = −27.6 ± 1.9 mV with hysteresis type H1 and mesoporous characteristics. EDX analysis indicated the presence of AgNPs (72.34 wt% and 10.46 wt% silver and oxygen respectively) indicating the effectiveness of the biosynthesis process. For the in vitro safety profile, AgNPs did not show cytotoxicity on VERO cells ranging from 0.5 to 150 μg mL−1 with a good gemoprotection. The minimum inhibitory concentration (MIC) showed that AgNPs have an inhibition of 312 μg mL−1 and 156 μg mL−1 on Gram-positive and Gram-negative strains, respectively. The phytotoxicity showed that only high concentrations (50 and 100 μg mL−1) of AgNPs interfered with seed growth. Therefore, AgNPs biosynthesized from l-ascorbic acid (AA) have potential applications as antimicrobial dressings and are biocompatible for application in skin lesions.

Irradiation effects on GEM detectors operated at RUN1 and RUN2 at the LHCb experiment

Triple-GEM detectors with pad readout have been employed to equip the innermost region (R1) of the first station (M1) within the Muon system of the LHCb experiment. The GEM detectors have been operated with an Ar/CO2/CF4 = 45/15/40 gas mixture at a gas gain of about 4000 with an average particle flux of about 250 kHz/cm2. Throughout RUN1 and RUN2, spanning approximately 440 days of colliding beams, the GEM detectors accumulated a charge of up to 0.5 C/cm2. This paper presents a comparative analysis between a global irradiation test of GEM detectors at the Calliope facility (ENEA-Casaccia, 1.25 MeV γ ray flux from a 60Co source) and the GEMs operated at LHCb, focusing on the impacts of a CF4-based gas mixture. In both instances, the detectors were opened and the GEM foils were examined by the EN-MME-MM CERN group with a Field Emission Gun Scanning Electron Microscope (FEG-SEM) for a magnified image analysis and an X-Max Energy Dispersive X-ray Spectroscopy (EDS) for the chemical one.

Isolation and Characterization of Spherical Cellulose Nanocrystals Extracted from the Higher Cellulose Yield of the Jenfokie Plant: Morphological, Structural, and Thermal Properties.

Scholars are looking for solutions to substitute hazardous substances in manufacturing nanocellulose from bio-sources to preserve the world's growing environmental consciousness. During the past decade, there has been a notable increase in the use of cellulose nanocrystals (CNCs) in modern science and nanotechnology advancements because of their abundance, biocompatibility, biodegradability, renewability, and superior mechanical properties. Spherical cellulose nanocrystals (J-CNCs) were successfully synthesized from Jenfokie micro-cellulose (J-MC) via sulfuric acid hydrolysis in this study. The yield (up to 58.6%) and specific surface area (up to 99.64 m2/g) of J-CNCs were measured. A field emission gun-scanning electron microscope (FEG-SEM) was used to assess the morphology of the J-MC and J-CNC samples. The spherical shape nanoparticles with a mean nano-size of 34 nm for J-CNCs were characterized using a transmission electron microscope (TEM). X-ray diffraction (XRD) was used to determine the crystallinity index and crystallinity size of J-CNCs, up to 98.4% and 6.13 nm, respectively. The chemical composition was determined using a Fourier transform infrared (FT-IR) spectroscope. Thermal characterization of thermogravimetry analysis (TGA), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) was conducted to identify the thermal stability and cellulose pyrolysis behavior of both J-MC and J-CNC samples. The thermal analysis of J-CNC indicated lower thermal stability than J-MC. It was noted that J-CNC showed higher levels of crystallinity and larger crystallite sizes than J-MC, indicating a successful digestion and an improvement of the main crystalline structure of cellulose. The X-ray diffraction spectra and TEM images were utilized to establish that the nanocrystals' size was suitable. The novelty of this work is the synthesis of spherical nanocellulose with better properties, chosen with a rich source of cellulose from an affordable new plant (studied for the first time) by stepwise water-retted extraction, continuing from our previous study.

Antibacterial and antiviral PA6-AgNPs microfibers for application as a filter element in facial respirators

Polymeric microfibers are very interesting materials that can be associated with other nanomaterials aiming to obtain specific properties and be used in a wide range of applications. In this study, we prepared different formulations of polyamide 6 (PA6) containing silver nanoparticles (AgNPs) and produced microfibers by solution blow spinning technique for its use as a filter element in a face respirator. The obtained samples were then characterized by field emission gun-scanning electron microscopy (FEG-SEM), energy dispersion spectroscopy (EDS), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), water contact angle (WCA), thermogravimetric analysis (TGA), and respirability and antibacterial, antiviral and cytotoxicity assays. In general, the microfibers were well dispersed and the AgNPs were evenly distributed throughout the samples, reflecting a hydrophilic character and good thermal stability, with a maximum weight loss of 2.9 % attributed to the evaporation of water molecules. The sample produced with a concentration of 10 mmol/L of silver nitrate presented acceptable levels of resistance to respiration. Concerning the microbiological analyses, the results showed that samples evidenced antibacterial effect against Escherichia coli and Staphylococcus aureus, forming inhibition halos of up to 4 mm in disk diffusion assays and inhibiting bacterial growth in liquid medium assays, as well as antiviral effect against betacoronavirus MHV-3, promoting a reduction of up to 99.9 % of viral particles. Moreover, the samples presented cytotoxicity on the first and second days, whereas on the seventh day some of the extracts did not show cytotoxic activity, indicating that the cells adapted to the culture medium. Considering the data set and the simple process of obtaining the microfibers, it was possible to conclude that this material can be applied as a filter element in a face respirator as well as in a variety of products with antibacterial and antiviral purposes.