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The knowledge about a potential in vivo uptake and subsequent toxicological effects of aluminum (Al), especially in the nanoparticulate form, is still limited. This paper focuses on a three day oral gavage study with three different Al species in Sprague Dawley rats. The Al amount was investigated in major organs in order to determine the oral bioavailability and distribution. Al-containing nanoparticles (NMs composed of Al 0 and aluminum oxide (Al 2 O 3 )) were administered at three different concentrations and soluble aluminum chloride (AlCl 3 ·6H 2 O) was used as a reference control at one concentration. A microwave assisted acid digestion approach followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis was developed to analyse the Al burden of individual organs. Special attention was paid on how the sample matrix affected the calibration procedure. After 3 days exposure, AlCl 3 ·6H 2 O treated animals showed high Al levels in liver and intestine, while upon treatment with Al 0 NMs significant amounts of Al were detected only in the latter. In contrast, following Al 2 O 3 NMs treatment, Al was detected in all investigated organs with particular high concentrations in the spleen. A rapid absorption and systemic distribution of all three Al forms tested were found after 3-day oral exposure. The identified differences between Al 0 and Al 2 O 3 NMs point out that both, particle shape and surface composition could be key factors for Al biodistribution and accumulation.

Two-dimensional (2D) structures composed of atomically thin materials with high carrier mobility have been studied as candidates for future transistors 1 – 4 . However, owing to the unavailability of suitable high-quality dielectrics, 2D field-effect transistors (FETs) cannot attain the full theoretical potential and advantages despite their superior physical and electrical properties 3 , 5 , 6 . Here we demonstrate the fabrication of atomically thin single-crystalline Al 2 O 3 (c-Al 2 O 3 ) as a high-quality top-gate dielectric in 2D FETs. By using intercalative oxidation techniques, a stable, stoichiometric and atomically thin c-Al 2 O 3 layer with a thickness of 1.25 nm is formed on the single-crystalline Al surface at room temperature. Owing to the favourable crystalline structure and well-defined interfaces, the gate leakage current, interface state density and dielectric strength of c-Al 2 O 3 meet the International Roadmap for Devices and Systems requirements 3 , 5 , 7 . Through a one-step transfer process consisting of the source, drain, dielectric materials and gate, we achieve top-gate MoS 2 FETs characterized by a steep subthreshold swing of 61 mV dec −1 , high on/off current ratio of 10 8 and very small hysteresis of 10 mV. This technique and material demonstrate the possibility of producing high-quality single-crystalline oxides suitable for integration into fully scalable advanced 2D FETs, including negative capacitance transistors and spin transistors. By using intercalative oxidation techniques, stable, stoichiometric and atomically thin single-crystalline Al 2 O 3 films can be produced, which can be effectively used as a dielectric in top-gated field-effect transistors based on two-dimensional materials.

Bauxite residue (Red mud) is produced in alumina plants by the Bayer process in which Al-containing minerals are dissolved in hot NaOH. The global residue inventory reached an estimated 3.5 billion tons in 2014, increasing by approximately 120 million tons per annum. The appropriate management of bauxite residue is becoming a global environmental concern following increased awareness of the need for environmental protection. Establishment of a vegetation cover is the most promising way forward for the management of bauxite residue, although its physical and chemical properties can limit plant growth due to high alkalinity and salinity, low hydraulic conductivity, trace element toxicity (Al and Fe), and deficiencies in organic matter and nutrition concentrations. This paper discusses the various revegetation and rehabilitation strategies. Studies of the rehabilitation of bauxite residues have mainly focused on two approaches, amelioration of the surface layer and screening of tolerant plants and soil microorganisms. Amendment with gypsum can reduce the high alkalinity and salinity, promote soil aggregation, and increase the hydraulic conductivity of bauxite residues. Organic matter can provide a source of plant nutrients, form stable complexes with metal cations, promote hydraulic conductivity, stabilize soil structure, and provide an energy source for soil organisms. Tolerant plants and microorganisms such as halophytes and alkaliphilic microbes show the greatest potential to ameliorate bauxite residues. However, during restoration or as a result of natural vegetation establishment, soil formation becomes a critical issue and an improved understanding of the various pedogenic processes are required, and future direction should focus on this area.

The present study was designed to evaluate the probable ameliorative role of quercetin (QCN) against oxidative hepatotoxicity induced by aluminum oxide nanoparticles (Al 2 O 3 NPs) with a diameter < 30 nm and lead acetate (Pb) co-exposure in adult male Sprague–Dawley rats. Rats were weighed and allocated to seven groups ( n  = 10 each) and were treated orally via orogastric gavage for 60 successive days: rats of the 1st group were kept as control given distilled water (1 ml/kg), rats of the 2nd group received 2 ml/kg BW/day corn oil; rats of the 3rd group were administered 20 mg/kg BW QCN/day; rats of the 4th group received 100 mg/kg BW Al 2 O 3 NPs; rats of the 5th group received 50 mg/kg BW Pb; rats of the 6th group co-received Al 2 O 3 NPs and Pb at the same previous doses; and rats of the 7th group were co-administered Al 2 O 3 NPs, Pb, and QCN at the same previous doses. At the end of the experiment, serum levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), total, direct, indirect bilirubin, triglycerides, total cholesterol, HDL, VLDL, and LDL were estimated. The hepatic oxidative stress biomarkers as superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GPx), were also evaluated. Finally, the histopathological and histomorphometric evaluations and the residues of Al and Pb in hepatic tissues were assessed. Al 2 O 3 NPs and/or Pb exposure significantly elevated lipid peroxidation levels and considerably altered the hepatic biochemical parameters; nevertheless, QCN significantly reduced hepatic enzymes compared to toxicant exposed groups. Additionally, QCN significantly improved Al 2 O 3 NPs-afforded liver tissue damage, as established in microscopic findings on the liver in the group treated with Al 2 O 3 NPs + Pb. Conclusively, QCN could be a candidate natural agent to safeguard the liver versus the co-harmful impacts of Al 2 O 3 NPs and Pb toxicity.

The commercial usage of Al 2 O 3 nanoparticles (Al 2 O 3 NPs) has gone up significantly in the recent times, enhancing the risk of environmental contamination with these agents and their consequent adverse effects on living systems. The current study has been designed to evaluate the cytogenetic potential of Al 2 O 3 NPs in Allium cepa (root tip cells) at a range of exposure concentrations (0.01, 0.1, 1, 10, and 100 μg/mL), their uptake/internalization profile, and the oxidative stress generated. We noted a dose-dependent decrease in the mitotic index (42 to 28 %) and an increase in the number of chromosomal aberrations. Various chromosomal aberrations, e.g. sticky, multipolar and laggard chromosomes, chromosomal breaks, and the formation of binucleate cells, were observed by optical, fluorescence, and confocal laser scanning microscopy. FT-IR analysis demonstrated the surface chemical interaction between the nanoparticles and root tip cells. The biouptake of Al 2 O 3 in particulate form led to reactive oxygen species generation, which in turn probably contributed to the induction of chromosomal aberrations.

This book provides a description of the generalized two layer surface complexation model, data treatment procedures, and thermodynamic constants for sorption of metal cations and anions on gibbsite, the most common form of aluminum oxide found in nature and one of the most abundant minerals in soils, sediments, and natural waters.

Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal–air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M x Mn 3– x O 4 (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M x Mn 3– x O 4 from the reduction of amorphous MnO 2 in aqueous M 2+ solution. The prepared Co x Mn 3– x O 4 nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co–Mn–O spinels are also interpreted by experiment and first-principle theoretical studies. Ceramic preparation of spinels — materials useful for a wide range of applications — requires complicated procedures and heat treatment over long periods. Now, it is shown that rapid synthesis of nanocrystalline Co–Mn–O spinels can be achieved under ambient conditions, and the resulting nanoparticles exhibit considerable catalytic activity towards the electrochemical oxygen reduction/evolution reactions.

Ceramic materials have gained prominence as advanced alternatives to metals and polymers in total hip prosthesis, owing to their superior wear resistance, chemical inertness, and minimal ion release. Among ceramic biomaterials, aluminum oxide (Al 2 O 2 ) is particularly favored for its exceptional hardness, high compressive strength, and excellent tribological performance, outperforming other candidates such as zirconium dioxide (ZrO₂) and silicon nitride (Si 2 N 4 ). However, the inherently brittle nature of ceramics necessitates careful stress analysis to mitigate fracture risks in ceramic-on-ceramic bearing systems. This study investigates the influence of radial clearance as a key geometric parameter on the mechanical safety of Al 2 O 2 -on-Al 2 O 3 bearings by analyzing Tresca stress distributions under physiologically representative loading conditions. A 2D axisymmetric finite element model was developed to simulate the internal stress behavior of the bearing components during a full gait cycle. Six radial clearance values, ranging from 0.03 to 0.3 mm, were systematically evaluated to determine their effect on internal shear stress patterns. The simulation results demonstrate that a radial clearance of 0.03 mm yields the lowest Tresca stress, indicating a more favorable stress distribution and reduced risk of shear-induced fracture. Conversely, larger clearances were associated with elevated shear stresses, which could compromise the mechanical integrity of the ceramic components over time. These findings highlight the importance of precise control over radial clearance during the design and manufacturing of ceramic-on-ceramic hip implants. The study provides foundational insights for optimizing implant geometry to enhance the structural reliability and clinical longevity of ceramic-bearing total hip prostheses.

The notion of mimicking natural structures in the synthesis of new structural materials has generated enormous interest but has yielded few practical advances. Natural composites achieve strength and toughness through complex hierarchical designs that are extremely difficult to replicate synthetically. We emulate nature's toughening mechanisms by combining two ordinary compounds, aluminum oxide and polymethyl methacrylate, into ice-templated structures whose toughness can be more than 300 times (in energy terms) that of their constituents. The final product is a bulk hybrid ceramic-based material whose high yield strength and fracture toughness [~200 megapascals (MPa) and ~30 MPa·m¹/²] represent specific properties comparable to those of aluminum alloys. These model materials can be used to identify the key microstructural features that should guide the synthesis of bio-inspired ceramic-based composites with unique strength and toughness.

The increasing use of nanoparticles (NPs) worldwide has raised some concerns about their impact on the environment. The aim of the study was to assess the toxicity of metal oxide nanoparticles, singly or combined, in a freshwater fish ( Carassius auratus ). The fish were exposed for 7, 14, and 21 days to different concentrations of NPs (10 μg Al 2 O 3 .L −1 , 10 μg ZnO.L −1 , 10 μg Al 2 O 3 .L −1 plus 10 μg ZnO.L −1 , 100 μg Al 2 O 3 .L −1 , 100 μg ZnO.L −1 , and 100 μg Al 2 O 3 .L −1 plus 100 μg ZnO.L −1 ). At the end of each exposure period, antioxidant enzyme activity (catalase, glutathione-S-transferase, and superoxide dismutase), lipid peroxidation, and histopathology were assessed in the gills and livers of C. auratus . The results show an increase in catalase (CAT) and superoxide dismutase (SOD) activity in the gills and livers of fish, especially after 14 days of exposure to single and combined NPs, followed by a reduction at 21 days. An increase in glutathione S-transferase (GST) was observed in gills after 7 days for all tested NP concentrations (single and combined); while in livers, a significant increase was determined after 14 days of exposure to 100 μg.L −1 of both single ZnO and Al 2 O 3 NPs. Lipid peroxidation (LPO) significantly increased in gills after 7 days of exposure to 100 μg.L −1 Al 2 O 3 NPs (single or combined). In livers, LPO increased significantly after 7 days of exposure to all tested concentrations of both single ZnO and Al 2 O 3 (except for 10 μg Al 2 O 3 .L −1 ), and after 14 days of exposure to ZnO (10 and 100 μg.L −1 ) and Al 2 O 3 (100 μg.L −1 ) . The results from histological observations suggest that exposure to metal oxide NPs affected both livers and gills, presenting alterations such as gill hyperplasia and liver degeneration. However, the most pronounced effects were found in gills. In general, this study shows that the tested NPs, single or combined, are capable of causing sub-lethal effects on C. auratus , but when combined, NPs seem to be slightly more toxic than when added alone.