Nanometer Scale Research Articles

Tuning Charge-Transfer States by Interface Electric Fields.

Intermolecular charge-transfer (CT) states are extended excitons with a charge separation on the nanometer scale. Through absorption and emission processes, they couple to the ground state. This property is employed both in light-emitting and light-absorbing devices. Their conception often relies on donor-acceptor (D-A) interfaces, so-called type-II heterojunctions, which usually generate significant electric fields. Several recent studies claim that these fields alter the energetic configuration of the CT states at the interface, an idea holding prospects like multicolor emission from a single emissive interface or shifting the absorption characteristics of a photodetector. Here, we test this hypothesis and contribute to the discussion by presenting a new model system. Through the fabrication of planar organic p-(i-)n junctions, we generate an ensemble of oriented CT states that allows the systematic assessment of electric field impacts. By increasing the thickness of the intrinsic layer at the D-A interface from 0 to 20 nm and by applying external voltages up to 6 V, we realize two different scenarios that controllably tune the intrinsic and extrinsic electric interface fields. By this, we obtain significant shifts of the CT-state peak emission of about 0.5 eV (170 nm from red to green color) from the same D-A material combination. This effect can be explained in a classical electrostatic picture, as the interface electric field alters the potential energy of the electric CT-state dipole. This study illustrates that CT-state energies can be tuned significantly if their electric dipoles are aligned to the interface electric field.

The Application of Cathodoluminescence (CL) for the Characterization of Blue Pigments

The combined application of Cathodoluminescence (CL) with Scanning Electron Microscopy (SEM) on paintings and painted surfaces has the potential to identify both organic and inorganic pigments on a micrometre or even nanometre scale. Additionally, the combination with Energy-Dispersive Spectrometry (EDS) allows for a more holistic, elemental, and mineralogical characterization of pigments. In addressing the need for the creation of a robust, open access database of characteristic CL spectra of pigments, a large project has been undertaken, focusing primarily on common organic and inorganic pigments. The present paper focuses on the CL characterization of 10 significant blue pigments in pure powder form: cerulean blue, Egyptian blue, Han blue, indigo, lapis lazuli, Maya blue, phthalo blue, vivianite, ultramarine blue, and zirconium blue. The CL spectra present characteristic bands for most of the pigments, allowing their secure identification, especially when combining the results with the EDS analyses. The effect of binding media and of the mixture of different pigments was also studied, via the analysis of mixtures of pigments with oil painted over canvas. Overall, both the binding medium and the mixture of pigments do not appear to create significant differences in the occurring spectra, thus allowing the identification of individual pigments. EDS and RAMAN spectra are included in order to facilitate comparison with other databases.

Direct-write printed controllable concave surface for fabricating flexible metal electrode

Structured surface of flexible substrate could generate a positive impact on flexibility of metal electrode due to the surface free energy relaxation, which could make the flexibility of metal electrode meet the performance requirement of flexible electronics. However, the preparation of controllable structured surface of flexible substrate is still a tough and challenge process. In this research work, controllable concave surface of flexible substrate was prepared by direct-write print with a viscoelastic substrate. When the controllable concave surface of flexible substrate was evaporated with a nanoscale metal layer, various metal electrodes could be obtained with a controllable morphology of concave surface. The direct-write printed concave surface efficiently enhanced the flexibility of metal electrodes. When the prepared concave surface generated a continuous connected structure with a 0.1 mm printing space, an excellently enhanced flexibility of metal electrode was achieved with an internal bending flexibility of 93.72%, external bending flexibility of 93.67%, stretchability of 85% and number of stable cyclic bending times over 12,000. Meanwhile, the direct-write printed concave surface generated a reversed convex surface, which could be used for pressure sensing as a flexible pressure sensor. Therefore, this research work provides an efficient method for fabricating flexible electrode, which has important research and application value in the area of high-performance flexible electronics.

Exploring Nanomaterials for Hydrogen Storage: Advances, Challenges, and Perspectives.

Hydrogen energy heralded for its environmentally friendly, renewable, efficient, and cost-effective attributes, stands poised as the primary alternative to fossil fuels in the future. Despite its great potential, the low volumetric density presents a formidable challenge in hydrogen storage. Addressing this challenge necessitates exploring effective storage techniques for a sustainable hydrogen economy. Solid-state hydrogen storage in nanomaterials (physically or chemically) holds promise for achieving large-scale hydrogen storage applications. Such approaches offer benefits, including safety, compactness, lightness, reversibility, and efficient generation of pure hydrogen fuel under mild conditions. This article presents solid-state nanomaterials, specifically nanoporous carbons (activated carbon, carbon fibers), metal-organic frameworks, covalently connected frameworks, nanoporous organic polymers, and nanoscale metal hydrides. Furthermore, new developments in hydrogen fuel cell technology for stationary and mobile applications have been demonstrated. The review outlines significant advancements thus far, identifies key barriers to practical implementation, and presents a perspective for future sustainable energy research. It concludes with recommendations to enhance hydrogen storage performance for cost-effective and long-lasting utilization.

Three-Dimensional Profile Reconstruction and Internal Defect Detection of Silicon Wafers Using Cascaded Fiber Optic Fabry–Pérot Interferometer and Leaky Field Detection Technologies

Abstract Wafer quality control is one of the important processes to improve the yield rate of semiconductor products. Profile quality and defects in the wafer are two key factors that should be taken into consideration. In this research, we introduce a method that measures the profile of the upper surface and the thickness of the wafer at the same time using an optical fiber cascaded Fabry–Pérot interferometer working at wavelength of 1550 nm. Therefore, the 3D profile of the wafer can be reconstructed directly. Testing results show that both accuracy and precision of the Fabry–Pérot interferometer are within a nanometer scale. Defects, especially those embedded inside the wafer, will be detected by monitoring the leaky field with treating wafers as slab waveguides. With the leaky field detection, defects on the lower surface of the wafer were successfully detected by monitoring the leaky field above the upper surface of the wafer. Compared with traditional methods such as radiographic testing or computed tomography testing, the proposed methods provide a cost-effective alternative for wafer quality evaluation.

Revealing the Mechanism of Combining Best Properties of Homogeneous and Heterogeneous Catalysis in Hybrid Pd/NHC Systems

AbstractThe formation of transient hybrid nanoscale metal species from homogeneous molecular precatalysts has been demonstrated by in situ NMR studies of catalytic reactions involving transition metals with N‐heterocyclic carbene ligands (M/NHC). These hybrid structures provide benefits of both molecular complexes and nanoparticles, enhancing the activity, selectivity, flexibility, and regulation of active species. However, they are challenging to identify experimentally due to the unsuitability of standard methods used for homogeneous or heterogeneous catalysis. Utilizing a sophisticated solid‐state NMR technique, we provide evidence for the formation of NHC‐ligated catalytically active Pd nanoparticles (PdNPs) from Pd/NHC complexes during catalysis. The coordination of NHCs via C(NHC)−Pd bonding to the metal surface was first confirmed by observing the Knight shift in the 13C NMR spectrum of the frozen reaction mixture. Computational modeling revealed that as little as few NHC ligands are sufficient for complete ligation of the surface of the formed PdNPs. Catalytic experiments combined with in situ NMR studies confirmed the significant effect of surface covalently bound NHC ligands on the catalytic properties of the PdNPs formed by decomposition of the Pd/NHC complexes. This observation shows the crucial influence of NHC ligands on the activity and stability of nanoparticulate catalytic systems.

Revealing the Mechanism of Combining Best Properties of Homogeneous and Heterogeneous Catalysis in Hybrid Pd/NHC Systems.

The formation of transient hybrid nanoscale metal species from homogeneous molecular precatalysts has been demonstrated by in situ NMR studies of catalytic reactions involving transition metals with N-heterocyclic carbene ligands (M/NHC). These hybrid structures provide benefits of both molecular complexes and nanoparticles, enhancing the activity, selectivity, flexibility, and regulation of active species. However, they are challenging to identify experimentally due to the unsuitability of standard methods used for homogeneous or heterogeneous catalysis. Utilizing a sophisticated solid-state NMR technique, we provide evidence for the formation of NHC-ligated catalytically active Pd nanoparticles (PdNPs) from Pd/NHC complexes during catalysis. The coordination of NHCs via C(NHC)-Pd bonding to the metal surface was first confirmed by observing the Knight shift in the 13C NMR spectrum of the frozen reaction mixture. Computational modeling revealed that as little as few NHC ligands are sufficient for complete ligation of the surface of the formed PdNPs. Catalytic experiments combined with in situ NMR studies confirmed the significant effect of surface covalently bound NHC ligands on the catalytic properties of the PdNPs formed by decomposition of the Pd/NHC complexes. This observation shows the crucial influence of NHC ligands on the activity and stability of nanoparticulate catalytic systems.

Effect of a low‐mineralized thermal spring water on skin barrier mechanical properties using atomic force microscopy

AbstractThe mineral content of thermal spring water (TSW) applied to the skin surface can directly influence the skin barrier. Indeed, our previous study showed that Avène TSW (ATSW), a low mineral content thermal spring water, protects the stratum corneum from dehydration compared to a mineral‐rich TSW (MR‐TSW) and maintains skin surface ultrastructure. While many TSWs have been recognized to have beneficial effects on skin, little is known about their localized and specific effects on skin barrier biomechanics at the nanometric scale. The aim of this study was to compare the effects of ATSW with a reference, MR‐TSW, on the biomechanical barrier properties of the skin under homeostasis conditions using atomic force microscopy (AFM). AFM was used to obtain a precise nanomechanical mapping of the skin surface after three applications of both TSW. This provides specific information on the skin topographical profile and elasticity. The topographic profile of skin samples showed a specific compaction of the skin layers after application of MR‐TSW, characterized by an increase of the total number of external skin layers, compared to non‐treated samples. By contrast, ATSW did not modify the skin topographic profile. High‐resolution force/volume acquisitions to capture the elastic modulus showed that it was directly correlated with skin rigidity. The elastic modulus strongly and significantly increased after MR‐TSW application compared to non‐treated skin. By contrast, applications of ATSW did not increase elastic modulus. These data demonstrate that applications of MR‐TSW significantly modified skin barrier properties by increasing skin surface layer compaction and skin rigidity. By contrast, ATSW did not modify the topographical profile of skin explants nor induce mechanical stress at the level of the stratum corneum, indicating it does not disrupt the biophysical properties linked to skin surface integrity.

Enhancing photon recycling of perovskite nanosheet by two-photon excitation

Nanometer scale light penetration depths of halide perovskite (HP) set an intrinsic limit on the performance improvement of optoelectronic devices. Here, we show that two-photon excitation can overcome this limit by markedly increasing the light penetration depth and significantly enhance photon recycling. Through a comparison study between one-photon and two-photon excitations by femtosecond laser pulses in a CsPbBr3 nanosheet, our results demonstrate that two-photon excitation can increase photocarrier transport distance by about 900 nm, which is even comparable to the photocarrier diffusion length. Our work provides substantial insights into the photon recycling of HP induced by nonlinear optical excitations, which can benefit the performance optimization of advanced optoelectronic devices.

A facile approach to developing multifunctional archaeological wool fabric surface with self-cleaning, and UV protection properties using nano-coating

In most Egyptian museums and storage facilities, archaeological textiles face several difficulties, including liquid stains, light effects, and the effects of air pollution. The majority of them are the consequence of human intervention, inappropriate handling, and poor display techniques. This research aims to provide colorful archaeological wool fabric surfaces with UV irradiation protection and self-cleaning properties without compromising the fabric’s mechanical or aesthetic qualities. To preserve archaeological wool fabrics from different stains and harmful light radiation, two simple coating technologies (hydrophilic and hydrophobic coating) were developed for the first time. The experiment used empirically accelerated aging of natural dyed wool fabrics to produce textile models that were as analogous as possible to the archaeological textiles. In the first coating method, the surfaces of hydrophilic fabrics were created by coating wool samples with calcium-alginate and nanoscale metal oxide particles (Ca-ALG@metal oxide nanoparticles). In the second coating technique, SiO2 NPs@silicon rubber (SiO2 NPs@RTV) was applied to the wool fabrics to generate the surfaces of superhydrophobic wool fabrics. The impact of the two coating treatments was assessed on the physicochemical characteristics and preservative features of the treated and standard wool fabric samples, including mechanical characteristics, color, light radiation protection, and self-cleaning.

Corrosion Protection Performance of PACC and PACC-Metal Oxides Nanocomposites Electropolymerized Coating of Low Carbon Steel

In the current study, a novel conductive polymer poly 6-((4 acetylphenyl) carbamoyl) cyclohex-3-ene-1-carboxylic acid (PACC) was created by polymerized 6-((4 acetylphenyl) carbamoyl) cyclohex-3-ene-1-carboxylic acid (ACC) monomer using the electropolymerization process. The resulting polymer was characterized using Fourier Transform Infrared Spectroscopy (FTIR). The ability of this polymer to protect the alloy from corrosion was studied at temperatures ranging between 298 and 328 K. The ability of these coatings to stop corrosion on the surface was assessed by measuring the corrosion potential (Ecorr) and the corrosion current (icorr) using a potentiostat. Adding nanoscale metal oxides (zirconium dioxide (ZrO2) and magnesium oxides (MgO)) enhanced the efficiency of this polymeric coating. The protection efficiency of the polymer alone was 77.5%; this efficiency increased to 85.0% and 99.7% in the presence of nano ZrO2 and MgO, respectively. Kinetic and thermodynamic parameters (Ea, H, and S) were calculated for uncoated and coated LCS. An atomic force microscope (AFM) studied the coating surface morphology. Electrochemical impedance spectroscopy (EIS) was used to evaluate the coating resistance.

Experimental and Computational Investigations of the Effects of Bridging Linkers on the Protein Corona of Nanoscale Metal–Organic Frameworks

Experimental and Computational Investigations of the Effects of Bridging Linkers on the Protein Corona of Nanoscale Metal–Organic Frameworks

Thermodynamic Driving Forces for the Self-Assembly of Diblock Polypeptoids.

Peptoid polymers with sequence-defined side chains are observed to self-assemble into a variety of structures spanning nanometer and micron scales. We explored a diblock copolypeptoid, poly(N-decylglycine)10-block-poly(N-2-(2-(2-methoxyethoxy)ethoxy)-ethylglycine)10 (abbreviated as Ndc10-Nte10), which forms crystalline nanofibers and nanosheets as evidenced by recent cryo-transmission electron microscopy, atomic force microscopy, X-ray diffraction, and calorimetry. Using all-atom molecular dynamics simulations, we examined the thermodynamic forces driving such self-assembly and how nanoscale morphology is tailored through modification of the N-terminus or via the addition of small molecules (urea). We have found that the hydrophobic Ndc domain alignment is key to the formation of molecular stacks whose growth is limited by electrostatic repulsion between protonated N-termini. These stacks are the building blocks that assemble via cooperative van der Waals attraction between the tips of extended decyl side chains to form nanofibers or nanosheets with a well-converged intermolecular interaction energy. Assemblies are significantly more stable in urea solution due to its strong attraction to the peptoid-solvent interface. Isolated peptoids exhibit curved all-cis backbones, which straighten within molecular stacks to maximize contact and registry between neighboring molecules. We hypothesize that competition between this attractive interaction and a strain cost for straightening the backbone is what leads to finite stack widths that define crystalline nanofibers of protonated Ndc10-Nte10. Growth is proposed to proceed through backbone unfurling via trans defects, which is more prevalent in aqueous solution than in THF, indicating a possible pathway to self-assembly under experimentally defined synthesis conditions (viz., THF evaporation).

Predictive Synthesis of Transition Metal Carbide via Thermochemical Oxocarbon Equilibrium.

Fabricating nanoscale metal carbides is a great challenge due to them having higher Gibbs free energy of formation (ΔG°) values than other metal compounds; additionally, these carbides have harsh calcination conditions, in which metal oxidation is preferred in the atmosphere. Herein, we report oxocarbon-mediated calcination for the predictive synthesis of nanoscale metal carbides. The thermochemical oxocarbon equilibrium of CO-CO2 reactions was utilized to control the selective redox reactions in multiatomic systems of Mo-C-O, contributing to the phase-forming and structuring of Mo compounds. By harnessing the thermodynamically predicted processing window, we controlled a wide range of Mo phases (MoO2, α-MoC1-x, and β-Mo2C) and nanostructures (nanoparticle, spike, stain, and core/shell) in the Mo compounds/C nanofibers. By inducing simultaneous reactions of C-O (selective C combustion) and Mo-C (Mo carbide formation) in the nanofibers, Mo diffusion was controlled in C nanofibers, acting as a template for the nucleation and growth of Mo carbides and resulting in precise control of the phases and structures of Mo compounds. The formation mechanism of nanostructured Mo carbides was elucidated according to the CO fractions of CO-CO2 calcination. Moreover, tungsten (W) and niobium (Nb) carbides/C nanofibers have been successfully synthesized by CO-CO2 calcination. We constructed the thermodynamic map for the predictive synthesis of transition metal carbides to provide universal guideline via thermochemical oxocarbon equilibrium. We revealed that our thermochemical oxocarbon-mediated gas-solid reaction enabled the structure and phase control of nanoscale transition metal compounds to optimize the material-property relationship accordingly.

Recycling the spent cobalt-based perovskites for the high-active oxygen catalysts in zinc-air batteries

Cobalt (Co) is widely used in energy storage and conversion devices, although its content on our planet is not adequate. Therefore, recycling Co from the spent Co-enriched materials is indispensable. Co-based perovskites, which contain abundant Co, are extensively utilized in solid oxide fuel cells, three-way catalysts, and oxygen-permeable membranes, and the recovery of Co from the spent Co-based perovskites is necessary to meet the long-term requirement of Co. In this work, a facile and universal thermal reduction method (750 °C and N2 atmosphere) is employed to convert the spent cobalt-based perovskites into high-performance bifunctional oxygen catalysts for zinc-air batteries (ZABs), achieving high-efficient Co recovery and re-utilization. At high temperatures, melamine and dopamine hydrochloride are transformed into carbon nanotubes, C3N4 and reducing gases (such as NH3 and H2). Simultaneously, the metal elements in the spent Co-based perovskites (SrNb0.1Co0.7Fe0.2O3,SNCF) are converted into nano-scale alloy particles and metal nitrides. Then, the phase structures, micromorphology, and element valences of the obtained multiphase oxygen catalyst (SNCF–Ni-PM) are characterized by X-ray diffraction, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy, respectively. The electrochemical properties, including oxygen catalytic activities and stability, of SNCF-Ni-PM are measured by linear sweep voltammetry, chronopotentiometry, chronoamperometry, and cyclic voltammetry methods. Considering the practical applications, the aqueous and solid-state ZABs are assembled and measured. The results demonstrate that the multiphase SNCF-Ni-PM mainly includes carbon nanotubes, C3N4 nanosheets, and FeNiN or CoFe nanoparticles. Moreover, SNCF-Ni-PM exhibits excellent bifunctional oxygen catalytic activity, with an oxygen evolution reaction (OER) potential at 10 mA cm−2 of 1.51 V and an oxygen reduction reaction (ORR) half-wave potential of 0.77 V, outperforming most of the reported oxygen catalysts. Using SNCF-Ni-PM, the aqueous and solid-state ZABs can achieve high power densities of 295.9 and 228.4 mW cm−2, respectively, being superior to most ZABs. In addition, the aqueous ZAB with SNCF-Ni-PM can operate stably for 300 h with a slight degradation. This work provides a feasible method for effectively recycling Co from the spent Co-based perovskites.

Atom probe tomography investigation of sintered transition metal carbonitride - A Zr(C,N) study

Zirconium based nitrides, carbides and carbonitrides are highly technological compounds which received during the 1950s and 60s huge interest due to their combination of metal and refractory properties. The interest reiterated recently due to the need of compounds with high electrical conductivity, corrosion and oxidation resistance, and neutron transparency with the rise of mobility electrification and nuclear energy. Sintered Zr(C,N) is investigated with CHN elemental analysis combined with atom probe tomography (APT) to evaluate the composition and homogeneity of carbon and nitrogen from the bulk down to the nanometer scale. Results have shown a strong nitrogen loss and an enrichment in carbon which diffused from the graphite die and punch. Nevertheless, the composition is homogenous in the sample. Atom probe tomography suggests that the sintered alloy is sub-stoichiometric with carbon and nitrogen homogeneously distributed within the grain. The stoichiometry calculated corresponds to the estimation by Vegard’s law.

Fabrication of silver nanoparticles synthesize using Lantana camara leaves extract on biofilm of sodium alginate

Silver nanoparticles (AgNPs) belong to the class of noble metal nanoparticles widely utilized across various sectors including biomedical applications, cosmetics, and everyday products like soaps, toothpaste, and detergents, thereby bringing individuals into direct contact with them. Extensive research has explored the antifungal properties of silver and silver nitrate. In this study, the synthesis of AgNPs was achieved effectively using a leaf extract from Lantana camara. Characterization of the synthesized AgNPs was performed employing transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Analysis via UV–vis spectroscopy, SEM and TEM proved reliable and sufficient, with the appearance of AgNPs resulting in a noticeable change in tonal form. SPR peaks for AgNPs were observed at 467–473 nm using UV–Vis spectroscopy, while FTIR studies delineated the stabilizing and peak properties of the AgNPs. Size of the synthesized silver nanoparticles increased with higher concentrations of AgNO3 solution, albeit averaging on the smaller side of the nanometer scale. Synthesized AgNPs have effective antibacterial properties of nanoparticles, their incorporation into food packaging materials could enhance food storage lifespan and ensure consumer safety. The burgeoning interest in developing biodegradable coatings, as alternatives to costly wax-based coatings lacking biodegradability, is on the rise. These coatings aim to preserve the qualities of harvested crops. These are flexible films derived from biological compounds like proteins and polysaccharides, act as barriers against external elements and exhibit bioflexibility. They hold potential applications in medicine, pharmacology, and the food industry. The integration of polysaccharides, proteins, and lipids to enhance the functionality of films represents a recent advancement in the manufacturing of biodegradable and biofilm-based films. The anticipated outcome of this study is to augment the beneficial properties of Lantana camara for the preparation of nanoparticles using its extract, thereby highlighting its biological activity against emerging pathogenic biofilm-forming species.

Acoustofluidic manipulation for submicron to nanoparticles.

Particles, ranging from submicron to nanometer scale, can be broadly categorized into biological and non-biological types. Submicron-to-nanoscale bioparticles include various bacteria, viruses, liposomes, and exosomes. Non-biological particles cover various inorganic, metallic, and carbon-based particles. The effective manipulation of these submicron to nanoparticles, including their separation, sorting, enrichment, assembly, trapping, and transport, is a fundamental requirement for different applications. Acoustofluidics, owing to their distinct advantages, have emerged as a potent tool for nanoparticle manipulation over the past decade. Although recent literature reviews have encapsulated the evolution of acoustofluidic technology, there is a paucity of reports specifically addressing the acoustical manipulation of submicron to nanoparticles. This article endeavors to provide a comprehensive study of this topic, delving into the principles, apparatus, and merits of acoustofluidic manipulation of submicron to nanoparticles, and discussing the state-of-the-art developments in this technology. The discourse commences with an introduction to the fundamental theory of acoustofluidic control and the forces involved in nanoparticle manipulation. Subsequently, the working mechanism of acoustofluidic manipulation of submicron to nanoparticles is dissected into two parts, dominated by the acoustic wave field and the acoustic streaming field. A critical analysis of the advantages and limitations of different acoustofluidic platforms in nanoparticles control is presented. The article concludes with a summary of the challenges acoustofluidics face in the realm of nanoparticle manipulation and analysis, and a forecast of future development prospects.

Size reduction of biochar to nanoscale decrease polycyclic aromatic hydrocarbons (PAHs) and metals content and bioavailability in nanobiochar

Objective of this research was to investigate ball milling of biochar from various feedstocks (willow, rice husk, oilseed rape, sewage sludge) under different pyrolysis conditions (500 and 750 °C, N2 and CO2 atmosphere) on polycyclic aromatic hydrocarbons (PAHs) and metals content. A significant reduction in both total (Ctotal Σ16) (1.1 to 2.4-fold decrease) and freely available (Cfree Σ16) (1.1 to 2.9-fold decrease) PAHs in nanobiochar (n-BC), particularly in sewage sludge (SSL)-derived n-BC was observed. The changes in biochar surface characteristics induced by ball milling, such as surface area, pore volume, and hydrophilicity, contribute to the decreased PAHs content. Mechanisms involving mechanochemical degradation, free-radical reactions, and defects on the biochar surface may explain the decrease of PAHs. The n-BC showed lower log Kd values for PAHs (reduced by 14 to 41 %) compared to bulk biochar (b-BC), indicating reduced effectiveness in immobilizing PAHs. The ball milling significantly reduced also metal contents by 37 to 55 %, especially in willow pellets and agricultural residue (rice husk and oilseed rape straw) with optimal reduction (by 55 %) observed for WL-derived n-BC produced at 650 °C. Importantly, no metals were detected in the aqueous phase after ball milling, ensuring environmental safety of these materials. Reduction mechanisms of metals during ball milling include stable aggregate formation, enhanced defects in crystalline structures, and irreversible adsorption onto new surfaces. The results demonstrate that the application of an eco-friendly ball milling method allows for the production of materials characterized by reduced contamination levels, which is crucial from an environmental protection viewpoint.

#2281 SEM for the diagnosis of glomerular diseases (amyloidosis, minimal change, thin membrane, IgA, membranoproliferative and diabetic nephropathy)

Abstract Background and Aims Treating renal diseases often requires ultrastructural details to establish or confirm diagnosis. Ultrastructural information that is not evidenced by optical microscopy includes, e.g., the podocyte foot processes effacement, thinning or alteration of basement membrane, presence of fibrils, Fabri's intracellular inclusions and subepithelial vs. subendothelial of deposits. Unfortunately, transmission electron microscopy (TEM), required to achieve the required resolution, has high costs, and is time-consuming. Here, we report our experience with scanning electron microscopy (SEM) on paraffin sections from standard pathology sections. Method We have retrospectively reanalyzed paraffin sections from renal biopsies of 50 patients with a diagnosis of IgAN, minimal change, diabetes, and amyloidosis. The paraffin sections were available and processed according to standard procedures (fixation, paraffin embedding), with a thickness of 3-4 µm. Sections were deparaffinized, stained with PASM (periodic acid Shiff + methenamine), mounted in aqueous mounting medium and imaged with 40x and 60x objectives. Sections were then unmounted, washed to remove glycerol, dehydrated in absolute alcohol, and air-dried. Finally, they were gold coated (“sputtering”) and analyzed in a scanning electron microscope (Zeiss). Results For the interpretation of SEM images, correlative analysis has been used, imaging precisely the same region of the section using standard optical microscopy and SEM. SEM can quickly identify the typical morphology of podocyte foot processes (Fig. 1A) and the podocyte effacement in minimal change disease (Fig. 1B). SEM can also easily allow the measurement of the thickness of the basement membrane of glomerular capillary walls (Fig. 1C-E) and its thinning in case of thin membrane disease (Fig. 1D) or its increased thickness in the case of diabetes (Fig. 1E). Amyloid fibrils (Fig. 1F) can also be identified in the capillary walls, confirming the diagnosis of amyloidosis Congo-red positive (Fig. 1G). The high resolution of the technique allows us to identify with high reliability the small ruptures of the capillary walls in IgA and membranoproliferative nephritis, with extravasation of erythrocytes and fibrin cloths (Fig. 1H). Mitochondria are well-demarcated, particularly in proximal tubule cells, and often, mitochondrial cristae are visible in samples with adequate fixation (Fig. 1I). Interstitial edema and fibrosis are evident in SEM microscopy (Fig. 1L). At very high magnification, in histological preparations with exceptional fixation, the filtration pores of endothelial cells could be observed (partially visible in Fig. 1E), as well as details such as the brush border of the tubular epithelial cells. The interpretation of the images is not always straightforward as it also requires knowledge of the artifacts induced by the fixation, processing, and inclusion of paraffin, such as, for example, the intracytoplasmic cellular structures containing lipids of the intratubular “foam cells” appear empty. For a correct interpretation of the SEM images, however, the recognition of the nuclei is essential because the chromatin is condensed into clods, especially around the periphery, and inside, some areas appear empty. Conclusion Scanning electron microscopy (SEM) is a powerful tool for the study of nephrological diseases, as it allows you to examine microscopic details at the nanometric scale (not detectable in optical microscopy), providing valuable information for diagnosis, understanding, and management of the disease, the possibility of carrying out Correlative Microscopy. Given the relatively simple and fast preparation of the samples to be examined, the low costs of execution, and the possibility of archiving the preparation in the histotheque for a possible revision of the case, this leads us to think that this method could be considered a valid alternative to transmission electron microscopy (TEM).