Dielectric and electromagnetic interference shielding properties of high entropy (Zn,Fe,Ni,Mg,Cd)Fe2O4 ferrite

The new (Zn,Mg,Ni,Fe,Cd)Fe2O4 high entropy ferrite with average crystallite size 11.8 nm was synthesized in two stages by annealing of co-precipitated amorphous precursor. The dielectric spectroscopy confirms, that the electrical conductivity and polarization processes are associated with the mobility of electrons in the structure of ferrite. It was concluded, that the both, high frequency complex dielectric permittivity as well as complex magnetic permeability are strongly temperature and frequency dependent. The AC electrical conductivity is associated with quantum mechanical tunneling of electrons and related to the transfer of charge carriers between Fe2+ and Fe3+ ions. Moreover, the microwave absorption properties were determined. The best microwave absorption properties have been confirmed in the frequency range 1.9 to 2.1 GHz for a layer which is 0.8-1 cm thick. For this range, reflection loss (RL) is lower than -25 dB and shielding effectiveness (SE) lower than -50 dB.

Modified halloysite nanoclay as a vehicle for sustained drug delivery

This paper presents the effect of modified halloysite nanotubes on the sustained drug release mechanisms of sodium salicylate. Acid treatment and composite polymer-halloysite modification techniques were adopted in this study. After each modification, sodium salicylate drug was loaded, and in vitro release properties were evaluated and compared with the raw unmodified halloysite nanotubes. The results obtained from SEM, TEM and FTIR analyses indicate that both acid treatment and composite formation have no effect on the tubular structure and morphology of halloysite. However, modification of the halloysite nanotubes did influence the drug release rate. In the acid treatment modification, there was an improved loading of sodium salicylate drug which resulted in the sustain release of large amount of the sodium salicylate. In the polymer/halloysite composite formation, a consistent layer of polymer was formed around the halloysite during the composite formation and thus delayed release providing sustained release of sodium salicylate drug over a longer period of time as compared to the acid treated and unmodified halloysite. The results from the invitro release were best fitted with the Higuchi and the Koresymer-Peppas models.

Cold anammox process and reduced graphene oxide - Varieties of effects during long-term interaction

Because of its energy efficiency, the anaerobic ammonium oxidation (anammox) process has been recognized as the most promising biological nitrogen removal process, but its implementation in mainstream wastewater treatment plants is limited by its relatively high optimal temperature (30 °C). Recently, it was shown that during short-term batch experiments, reduced graphene oxide (RGO) displayed accelerated reaction activity at low temperatures (10-15 °C). In this study, the long-term effects of RGO on the low-temperature anammox process in a sequencing batch reactor (SBR), are studied for the first time, including different methods of interaction. The results presented here show that RGO can stimulate anammox activity up to 17% through two factors: bacterial growth stimulation, which was especially significant at higher temperatures (>15 °C), and an increase of the anammox reaction rate, which occurred only below 15 °C. The bacterial community structure was not influenced by addition of RGO. Moreover, after incubation in an anammox bioreactor, RGO showed signs of degradation and chemical changes as evidenced by the presence of oxygen and calcium on its surface. According to the literature and the obtained results, it is proposed that RGO is oxidized and oxygen is reduced by the organic mediator that is involved in the enzymatic reactions. However, activated sludge is a very complex structure created by numerous, undefined microorganisms, which makes it difficult to determine the exact oxidation mechanism.

Enhanced degradation of sulfamethoxazole by a modified nano zero-valent iron with a β-cyclodextrin polymer: Mechanism and toxicity evaluation

Rising concern about emerging and already persisting pollutants in water has urged the scientific community to develop novel remedial techniques. A new group of remediation methods is based on the modification of nanoscale zero-valent iron particles (nZVI), which are well known for treating volatile organic compounds and heavy metals. The properties of nZVI may be further enhanced by modifying their structure or surface using "green" polymers. Herein, nZVI was modified by a β-cyclodextrin polymer (β-CDP), which is considered an environmentally safe and inexpensive adsorbent of contaminants. This composite was used for the first time for the degradation of sulfamethoxazole (SMX). Coating by β-CDP not only enhanced the degradation of SMX (>95%, under 10 min) by the nanoparticles in a wide pH range (3-9) and enabled their efficient reusability (for three cycles) but also made the coated nZVI less toxic to the model bioindicator microalga Raphidocelis subcapitata. Moreover, degradation products of SMX were found to be less toxic to Escherichia coli bacteria and R. subcapitata microalga, contrary to the SMX antibiotic itself, indicating a simple and eco-friendly cleaning process. This research aims to further stimulate and develop novel remedial techniques based on nZVI, and provides a potential application in the degradation of antibiotics in a wide pH range. Moreover, the wealth of available cyclodextrin materials used for surface modification may open a way to discover more efficient and attractive composites for environmental applications.

Simple Method to Improve Electrical Conductivity of Films Made from Single-Walled Carbon Nanotubes

Despite the widespread use of sonication for individualization of nanomaterials, its destructive nature is rarely acknowledged. In this study, we demonstrated how exposure of the material to a hostile sound wave environment can be limited by the application of another preprocessing step. Single-walled carbon nanotubes (CNTs) were initially ground in a household coffee grinder, which enabled facile deagglomeration thereof. Such a simple approach enabled us to obtain high-quality CNT dispersion at reduced sonication time. Most importantly, electrical conductivity of free-standing films prepared from these dispersion was improved almost fourfold as compared with unground material eventually reaching 1067 ± 34 S/cm. This work presents a new approach as to how electrical properties of nanocarbon ensembles may be enhanced without the application of doping agents, the presence of which is often ephemeral.

Silver nanoparticles synthesized by UV-irradiation method using chloramine T as modifier: structure, formation mechanism and catalytic activity

Two different formation mechanisms of Ag NPs by UV-irradiation method in the presence of chloramine T were identified.

Selective Laser Melting of 18NI-300 Maraging Steel

In the present study, 18% Ni 300 maraging steel powder was processed using a selective laser melting (SLM) technique to study porosity variations, microstructure, and hardness using various process conditions, while maintaining a constant level of energy density. Nowadays, there is wide range of utilization of metal technologies and its products can obtain high relative density. A dilatometry study revealed that, through heating cycles, two solid-state effects took place, i.e., precipitation of intermetallic compounds and the reversion of martensite to austenite. During the cooling process, one reaction took place (i.e., martensitic transformation), which was confirmed by microstructure observation. The improvements in the Rockwell hardness of the analyzed material from 42 ± 2 to 52 ± 0.5 HRC was improved as a result of aging treatment at 480 °C for 5 h. The results revealed that the relative density increased using laser speed (340 mm/s), layer thickness (30 µm), and hatch distance (120 µm). Relative density was found approximately 99.3%. Knowledge about the influence of individual parameters in the SLM process on porosity will enable potential manufacturers to produce high quality components with desired properties.

Carbon Quantum Dots from Amino Acids Revisited: Survey of Renewable Precursors toward High Quantum-Yield Blue and Green Fluorescence

Carbon quantum dots (CQDs) were synthesized via a green, one-step hydrothermal method. As CQD precursors, nine amino acids of different structural descriptors (negatively/positively charged in water, polar, hydrophobic, sulfur-containing, and other/complex ones) were surveyed: Asp, Cys, Gly, His, Leu, Lys, Phe, Pro, and Ser. The reactions were performed in an autoclave in the presence of citric acid at 180 °C for 24 h and yielded core-shell CQDs. CQDs were comprehensively characterized by transmission electron microscopy, dynamic light scattering, Raman, UV/Vis, infrared, X-ray photoelectron spectroscopy, and fluorescence spectroscopy. At the excitation wavelength of λ_ex = 350 nm, Cys-, Phe-, Leu-, and Lys-based CQDs displayed the highest quantum yield blue fluorescence-90 ± 5, 90 ± 4, 87 ± 5, and 67 ± 3%, respectively-superior to the conventional fluorescent dyes. Strikingly, for Lys- and Phe-CQDs, dissimilar trends in the excitation-emission wavelength relationships were identified, that is, constantly strong red shifts versus excitation wavelength-independent emission. Cys- and Lys-CQDs were water-dispersible toward the narrow unimodal distribution of hydrodynamic diameters-0.6 and 2.5 nm, respectively. Additionally, Lys- and Cys-CQDs, with high absolute zeta potential values, formed stable aqueous colloids in a broad range of pH (2, 7, and 12). The results constitute important premises for water-based applications of CQDs, such as bioimaging or photocatalysis.

Drug delivery via anion exchange of salicylate decorating poly(meth)acrylates based on a pharmaceutical ionic liquid

Poly[trimethylammonium (meth)acrylate]s decorated by salicylate anions were investigated as drug carriers. Efficient exchange of drug was provided by phosphate anions contained in the medium within 4 h.

Influence of the modifiers in polyol method on magnetically induced hyperthermia and biocompatibility of ultrafine magnetite nanoparticles

Magnetite nanoparticles (Fe₃O₄ NPs) are widely tested in various biomedical applications, including magnetically induced hyperthermia. In this study, the influence of the modifiers, i.e., urotropine, polyethylene glycol, and NH₄HCO_3, on the size, morphology, magnetically induced hyperthermia effect, and biocompatibility were tested for Fe₃O₄ NPs synthesized by polyol method. The nanoparticles were characterized by a spherical shape and similar size of around 10 nm. At the same time, their surface is functionalized by triethylene glycol or polyethylene glycol, depending on the modifiers. The Fe₃O₄ NPs synthesized in the presence of urotropine had the highest colloidal stability related to the high positive value of zeta potential (26.03 ± 0.55 mV) but were characterized by the lowest specific absorption rate (SAR) and intrinsic loss power (ILP). The highest potential in the hyperthermia applications have NPs synthesized using NH₄HCO₃, for which SAR and ILP were equal to 69.6 ± 5.2 W/g and 0.613 ± 0.051 nHm²/kg, respectively. Their application possibility was confirmed for a wide range of magnetic fields and by cytotoxicity tests. The absence of differences in toxicity to dermal fibroblasts between all studied NPs was confirmed. Additionally, no significant changes in the ultrastructure of fibroblast cells were observed apart from the gradual increase in the number of autophagous structures.

Fabrication of electrospun poly(lactic acid) nanoporous membrane loaded with niobium pentoxide nanoparticles as a potential scaffold for biomaterial applications

Tissue engineering aims to regenerate and restore damaged human organs and tissues using scaffolds that can mimic the native tissues. The requirement for modern and efficient biomaterials that are capable of accelerating the healing process has been considerably increased. In this work, a novel electrospun poly(lactic acid) (PLA) nanoporous membrane incorporated with niobium pentoxide nanoparticles (Nb₂ O₅ ) for biomaterial applications was developed. Nb₂ O₅ nanoparticles were obtained by microwave-assisted hydrothermal synthesis, and different concentrations (0, 1, 3, and 5% wt/wt) were tested. Chemical, morphological, mechanical, and biological properties of membranes were evaluated. Cell viability results demonstrated that the membranes presented nontoxic effects. The incorporation of Nb₂ O₅ improved cell proliferation without impairing the wettability, porosity, and mechanical properties of membranes. Membranes containing Nb₂ O₅ nanoparticles presented biocompatible properties with suitable porosity, which facilitated cell attachment and proliferation while allowing diffusion of oxygen and nutrients. This study has demonstrated that Nb₂ O₅ nanoparticle-loaded electrospun PLA nanoporous membranes are potential candidates for drug delivery and wound dressing applications.

Production, Characterization and Application of Oxide Nanotubes on Ti-6Al-7Nb Alloy as a Potential Drug Carrier

This work concerns the development of a method of functionalization of the surface of the biomedical Ti–6Al–7Nb alloy by producing oxide nanotubes (ONTs) with drug-eluting properties. Shaping of the morphology, microstructure, and thickness of the oxide layer was carried out by anodization in an aqueous solution of 1 M ethylene glycol with the addition of 0.2 M NH₄F in the voltage range 5–100 V for 15–60 min at room temperature. The characterization of the physicochemical properties of the obtained ONTs was performed using SEM, XPS, and EDAX methods. ONTs have been shown to be composed mainly of TiO₂, Al₂O₃, and Nb₂O₅. Single-walled ONTs with the largest specific surface area of 600 cm² cm⁻² can be obtained by anodization at 50 V for 60 min. The mechanism of ONT formation on the Ti–6Al–7Nb alloy was studied in detail. Gentamicin sulfate loaded into ONTs was studied using FTIR, TG, DTA, and DTG methods. Drug release kinetics was determined by UV–Vis spectrophotometry. The obtained ONTs can be proposed for use in modern implantology as carriers for drugs delivered locally in inflammatory conditions.

Glass-Forming Ability and Corrosion Resistance of Al88Y8-xFe4+x (x = 0, 1, 2 at.%) Alloys

The effect of iron and yttrium additions on glass forming ability and corrosion resistance of Al₈₈Y_8-xFe_4+x (x = 0, 1, 2 at.%) alloys in the form of ingots and melt-spun ribbons was investigated. The crystalline multiphase structure of ingots and amorphous-crystalline structure of ribbons were examined by a number of analytical techniques including X-ray diffraction, Mössbauer spectroscopy, and transmission electron microscopy. It was confirmed that the higher Fe additions contributed to formation of amorphous structures. The impact of chemical composition and structure of alloys on their corrosion resistance was characterized by electrochemical tests in 3.5% NaCl solution at 25 °C. The identification of the mechanism of chemical reactions taking place during polarization test along with the morphology and internal structure of the surface oxide films generated was performed. It was revealed that the best corrosion resistance was achieved for the Al₈₈Y₇Fe₅ alloy in the form of ribbon, which exhibited the lowest corrosion current density (j_corr = 0.09 μA/cm²) and the highest polarization resistance (R_p = 96.7 kΩ∙cm²).

Tuning wettability and electrical conductivity of single-walled carbon nanotubes by the modified Hummers method

Partial oxidation of nanocarbon materials is one of the most straightforward methods to improve their compatibility with other materials, which widens its application potential. This work studied how the microstructure and properties of high crystallinity single-walled carbon nanotubes (SWCNTs) can be tailored by applying the modified Hummers method. The influence of temperature (0, 18, 40 °C), reaction time (0 min to 7 h), and the amount of KMnO4 oxidant was monitored. The results showed that depending on the oxidation conditions, the electronic characteristics of the material could be adjusted. After optimizing the parameters, the SWCNTs were much more conductive (1369 ± 84 S/cm with respect to 283 ± 32 S/cm for the untreated material). At the same time, the films made from them exhibited hydrophilic character of the surface (water contact angle changed from 71° to 27°).

Influence of Magnetite Nanoparticles Shape and Spontaneous Surface Oxidation on the Electron Transport Mechanism

The spontaneous oxidation of a magnetite surface and shape design are major aspects of synthesizing various nanostructures with unique magnetic and electrical properties, catalytic activity, and biocompatibility. In this article, the roles of different organic modifiers on the shape and formation of an oxidized layer composed of maghemite were discussed and described in the context of magnetic and electrical properties. It was confirmed that Fe3O4 nanoparticles synthesized in the presence of triphenylphosphine could be characterized by cuboidal shape, a relatively low average particle size (9.6 ± 2.0 nm), and high saturation magnetization equal to 55.2 emu/g. Furthermore, it has been confirmed that low-frequency conductivity and dielectric properties are related to surface disordering and oxidation. The electric energy storage possibility increased for nanoparticles with a disordered and oxidized surface, whereas the dielectric losses in these particles were strongly related to their size. The cuboidal magnetite nanoparticles synthesized in the presence of triphenylphosphine had an ultrahigh electrical conductivity (1.02 × 10-4 S/cm at 10 Hz) in comparison to the spherical ones. At higher temperatures, the maghemite content altered the behavior of electrons. The electrical conductivity can be described by correlated barrier hopping or overlapping large polaron tunneling. Interestingly, the activation energies of electrons transport by the surface were similar for all the analyzed nanoparticles in low- and high-temperature ranges.

On the Use of Laser Fragmentation for the Synthesis of Ligand-Free Ultra-Small Iron Nanoparticles in Various Liquid Environments

Traditionally, the synthesis of nanomaterials in the ultra-small size regime (1-3 nm diameter) has been linked with the employment of excessive amounts of hazardous chemicals, inevitably leading to significant environmentally detrimental effects. In the current work, we demonstrate the potential of laser fragmentation in liquids (LFL) to produce highly pure and stable iron ultra-small nanoparticles. This is carried out by reducing the size of carbonyl iron microparticles dispersed in various polar solvents (water, ethanol, ethylene glycol, polyethylene glycol 400) and liquid nitrogen. The explored method enables the fabrication of ligand-free iron oxide ultra-small nanoparticles with diameter in the 1-3 nm range, a tight size distribution, and excellent hydrodynamic stability (zeta potential > 50 mV). The generated particles can be found in different forms, including separated ultra-small NPs, ultra-small NPs forming agglomerates, and ultra-small NPs together with zero-valent iron, iron carbide, or iron oxide NPs embedded in matrices, depending on the employed solvent and their dipolar moment. The LFL technique, aside from avoiding chemical waste generation, does not require any additional chemical agent, other than the precursor microparticles immersed in the corresponding solvent. In contrast to their widely exploited chemically synthesized counterparts, the lack of additives and chemical residuals may be of fundamental interest in sectors requiring colloidal stability and the largest possible number of chemically active sites, making the presented pathway a promising alternative for the clean design of new-generation nanomaterials.

Atomic structure of Mg-based metallic glass investigated with neutron diffraction, reverse Monte Carlo modeling and electron microscopy

The structure of a multicomponent metallic glass, Mg₆₅Cu₂₀Y₁₀Ni₅, was investigated by the combined methods of neutron diffraction (ND), reverse Monte Carlo modeling (RMC) and high-resolution transmission electron microscopy (HRTEM). The RMC method, based on the results of ND measurements, was used to develop a realistic structure model of a quaternary alloy in a glassy state. The calculated model consists of a random packing structure of atoms in which some ordered regions can be indicated. The amorphous structure was also described by peak values of partial pair correlation functions and coordination numbers, which illustrated some types of cluster packing. The N = 9 clusters correspond to the tri-capped trigonal prisms, which are one of Bernal's canonical clusters, and atomic clusters with N = 6 and N = 12 are suitable for octahedral and icosahedral atomic configurations. The nanocrystalline character of the alloy after annealing was also studied by HRTEM. The selected HRTEM images of the nanocrystalline regions were also processed by inverse Fourier transform analysis. The high-angle annular dark-field (HAADF) technique was used to determine phase separation in the studied glass after heat treatment. The HAADF mode allows for the observation of randomly distributed, dark contrast regions of about 4-6 nm. The interplanar spacing identified for the orthorhombic Mg₂Cu crystalline phase is similar to the value of the first coordination shell radius from the short-range order.

Growth suppression of bacteria by biofilm deterioration using silver nanoparticles with magnetic doping

Decades of antibiotic use and misuse have generated selective pressure toward the rise of antibiotic-resistant bacteria, which now contaminate our environment and pose a major threat to humanity. According to the evolutionary "Red queen theory", developing new antimicrobial technologies is both urgent and mandatory. While new antibiotics and antibacterial technologies have been developed, most fail to penetrate the biofilm that protects bacteria against external antimicrobial attacks. Hence, new antimicrobial formulations should combine toxicity for bacteria, biofilm permeation ability, biofilm deterioration capability, and tolerability by the organism without renouncing compatibility with a sustainable, low-cost, and scalable production route as well as an acceptable ecological impact after the ineluctable release of the antibacterial compound in the environment. Here, we report on the use of silver nanoparticles (NPs) doped with magnetic elements (Co and Fe) that allow standard silver antibacterial agents to perforate bacterial biofilms through magnetophoretic migration upon the application of an external magnetic field. The method has been proved to be effective in opening micrometric channels and reducing the thicknesses of models of biofilms containing bacteria such as Enterococcus faecalis, Enterobacter cloacae, and Bacillus subtilis. Besides, the NPs increase the membrane lipid peroxidation biomarkers through the formation of reactive oxygen species in E. faecalis, E. cloacae, B. subtilis, and Pseudomonas putida colonies. The NPs are produced using a one-step, scalable, and environmentally low-cost procedure based on laser ablation in a liquid, allowing easy transfer to real-world applications. The antibacterial effectiveness of these magnetic silver NPs may be further optimized by engineering the external magnetic fields and surface conjugation with specific functionalities for biofilm disruption or bactericidal effectiveness.

Broadband dielectric spectroscopy for monitoring temperature-dependent chloride ion motion in BiOCl plates

The dielectric properties and electrical conduction mechanism of bismuth oxychloride (BiOCl) plates synthesized using chloramine-T as the chloride ion source were investigated. Thermally-activated structure rebuilding was monitored using broadband dielectric spectroscopy, which showed that the onset temperature of this process was 283 K. This rebuilding was related to the introduction of free chloride ions into [Bi2O2]2+ layers and their growth, which increased the intensity of the (101) diffraction peak. The electrical conductivity and dielectric permittivity were related to the movement of chloride ions between plates (in the low-frequency region), the interplanar motion of Cl- ions at higher frequencies, vibrations of these ions, and charge carrier hopping at frequencies above 10 kHz. The influence of the free chloride ion concentration on the electrical conductivity was also described. Structure rebuilding was associated with a lower concentration of free chloride ions, which significantly decreased the conductivity. According to the analysis, the BiOCl plate conductivity was related to the movement of Cl- ions, not electrons.

From dots to tubes - the reversed scenario of bottom-up external-catalyst-free synthesis of N-doped carbon nanotubes

We present a novel external-catalyst-free route for the synthesis of N-doped carbon nanotubes (N-CNTs) from amino-acid-derived carbon dots (CDs) as sustainable resources. N-CNTs (∼4-26 at% of N) were comprehensively characterized by complementary techniques while the synthetic strategy emerges as an important alternative and, simultaneously, a simply-scalable approach.

Structural Characterization of Al65Cu20Fe15 Melt-Spun Alloy by X-ray, Neutron Diffraction, High-Resolution Electron Microscopy and Mössbauer Spectroscopy

The aim of the work was to characterize the structure of Al₆₅Cu₂₀Fe₁₅ alloy obtained with the use of conventional casting and rapid solidification-melt-spinning technology. Based on the literature data, the possibility of an icosahedral quasicrystalline phase forming in the Al-Cu-Fe was verified. Structure analysis was performed based on the results of X-ray diffraction, neutron diffraction, ⁵⁷Fe Mössbauer and transmission electron microscopy. Studies using differential scanning calorimetry were carried out to describe the crystallization mechanism. Additionally, electrochemical tests were performed in order to characterize the influence of the structure and cooling rate on the corrosion resistance. On the basis of the structural studies, the formation of a metastable icosahedral phase and partial amorphous state of ribbon structure were demonstrated. The possibility of the formation of icosahedral quasicrystalline phase I-AlCuFe together with the crystalline phases was indicated by X-ray diffraction (XRD), neutron diffraction (ND) patterns, Mössbauer spectroscopy, high-resolution transmission electron microscopy (HRTEM) observations and differential scanning calorimetry (DSC) curves. The beneficial effect of the application of rapid solidification on the corrosive properties was also confirmed.

Evaluation of anticancer activity of urotropine surface modified iron oxide nanoparticles using a panel of forty breast cancer cell lines

Urotropine, an antibacterial agent to treat urinary tract bacterial infections, can be also considered as a repurposed drug with formaldehyde-mediated anticancer activity. Recently, we have synthesized urotropine surface modified iron oxide nanoparticles (URO@Fe3O4 NPs) with improved colloidal stability and limited cytotoxicity against human fibroblasts. In the present study, we have investigated URO@Fe3O4 NP-mediated responses in a panel of forty phenotypically different breast cancer cell lines along with three non-cancerous corresponding cell lines. URO@Fe3O4 NPs promoted oxidative stress and FOXO3a-based antioxidant response in breast cancer cells. Elevated levels of GPX4 and decreased levels of ACSL4 in URO@Fe3O4 NP-treated breast cancer cells protected against ferroptotic cell death. On the contrary, URO@Fe3O4 NPs impaired the activity of PERK, a part of unfolded protein response (UPR), especially when the glucose supply was limited, that was accompanied by genetic instability, and apoptotic and/or necrotic cell death in breast cancer cells. In conclusion, this is the first comprehensive analysis of anticancer effects of URO@Fe3O4 NPs against a panel of forty breast cancer cell lines with different receptor status and in glucose replete and deplete conditions. We suggest that presented results might be helpful for designing new nano-based anti-breast cancer strategies.

Study of the Impact of Coals and Claystones on Wear-Resistant Steels

This paper discusses the impact of coal abrasive materials of varied petrographic composition and claystones containing admixtures of coal matter on the surface wear of wear-resistant martensitic steels. Wear tests were conducted at a test stand for three petrographic varieties of hard coal: vitrinite, clarinite, and durinite, and five samples of claystone. These tests revealed no significant effect of the type of coal abrasive used on the value of mass loss from the surface of the wear-resistant steel samples. The reason behind the foregoing is the observed tendency of coal abrasives, irrespective of their petrographic variety, to penetrate surface irregularities, especially those attributable to previous surface treatment of the samples and the impact of wear products. The dominant forms of surface damage were surface fatigue chipping and scratches caused by the particles which detached themselves from the surface of the steel samples, as observed for all the analysed coal variants. On the surfaces of the samples seasoned in the presence of claystones, highly varied forms of damage were observed: microcutting, scaly surface cracks, delamination, and deep cracks. In these cases, it was possible that the abrasive grains had been pressed into the steel surface irregularities, but no layered forms of the pressed-in abrasive material were observed to have developed. The paper also presents a model for the formation of coal films and discusses their possible effect on wear minimisation.

Carbon-Coated Iron Oxide Nanoparticles Promote Reductive Stress-Mediated Cytotoxic Autophagy in Drug-Induced Senescent Breast Cancer Cells

The surface modification of magnetite nanoparticles (Fe3O4 NPs) is a promising approach to obtaining biocompatible and multifunctional nanoplatforms with numerous applications in biomedicine, for example, to fight cancer. However, little is known about the effects of Fe3O4 NP-associated reductive stress against cancer cells, especially against chemotherapy-induced drug-resistant senescent cancer cells. In the present study, Fe3O4 NPs in situ coated by dextran (Fe3O4@Dex) and glucosamine-based amorphous carbon coating (Fe3O4@aC) with potent reductive activity were characterized and tested against drug-induced senescent breast cancer cells (Hs 578T, BT-20, MDA-MB-468, and MDA-MB-175-VII cells). Fe3O4@aC caused a decrease in reactive oxygen species (ROS) production and an increase in the levels of antioxidant proteins FOXO3a, SOD1, and GPX4 that was accompanied by elevated levels of cell cycle inhibitors (p21, p27, and p57), proinflammatory (NFκB, IL-6, and IL-8) and autophagic (BECN1, LC3B) markers, nucleolar stress, and subsequent apoptotic cell death in etoposide-stimulated senescent breast cancer cells. Fe3O4@aC also promoted reductive stress-mediated cytotoxicity in nonsenescent breast cancer cells. We postulate that Fe3O4 NPs, in addition to their well-established hyperthermia and oxidative stress-mediated anticancer effects, can also be considered, if modified using amorphous carbon coating with reductive activity, as stimulators of reductive stress and cytotoxic effects in both senescent and nonsenescent breast cancer cells with different gene mutation statuses.