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Nanoscale anti-ferromagnetic (AFM) NiO exhibits intriguing magnetic anomalies influenced by factors such as size, stoichiometry, surface chemistry, and lattice strain. In the present work, black-coloured NiO nanoparticles were synthesized by combustion method, incorporating cationic Ni2+ vacancies and Ni3+ species on their surface. Annealing NiO at high temperatures (400–800 °C) led to a colour change from black to green, indicating the transition from a non-stoichiometric to a stoichiometric state. The formation of Ni2+ vacancies disrupted AFM ordering between Ni2+ and O2− ions, while the presence of Ni3+ promoted double exchange interactions between Ni3+ and neighbouring Ni2+ ions, contributing to ferromagnetism (FM) in AFM NiO. The spin exchange interaction at AFM-FM core–shell interface in NiO resulted in an exchange bias effect. Notably, the NiO nanoparticles with smaller average crystallite size (~ 5 nm) and higher cationic Ni2+ vacancies on the surface exhibited strong ferromagnetism and higher coercivity values. In particular, the as-prepared NiO (N) and N-4 samples showed remarkable improvement in exchange bias field, measuring 2.5 kOe and 2.1 kOe, respectively, due to the reinforced spin-exchange interaction within the FM-AFM core–shell structure of NiO. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is a lethal and the most common type of primary brain tumor. Extensive hypoxic regions in GBMs turn these tumors highly malignant and worsen the prognosis and clinical outcomes of the patients. Tumor cells residing in hypoxic regions exhibit high ROS levels and resistance to chemo- and radiation therapies. This facilitates the cancer stem cell niche to expand and contribute to cell proliferation and further tumor growth. Therapeutic approaches targeting hypoxia-induced factors, such as the anti-VEGF monoclonal antibody, bevacizumab have shown promising results in stabilizing the disease. Glioblastomas are predominantly glycolytic and hypoxia-induced factors are useful in the metabolic reprogramming of these tumors. Hence, developing therapeutic approaches that counter hypoxia may hold the key to improving the prognosis and clinical outcome of GBMs. In this work, we report that cerium oxide nanoparticles (CNPs) hold therapeutic potential for the treatment of GBM. CNPs of size 6 nm (CNP-6) and 12 nm (CNP-12) were used for this study. Our results show that CNP-6 exhibits short-term mitigation of ROS levels (up to 24 h) and are able to modulate the TMZ IC50 in tumor microenvironment-like conditions. CNP-12, on the other hand, mitigated ROS levels for up to 72 h, but the mitigation proved to be too lethal for the cells to survive given the important role played by basal-level ROS inside cells. Also, CNP-6 was better at altering metabolic gene expression profile compared to CNP-12 under tumor microenvironment-like conditions. These results indicate that CNPs of size < 10 nm may hold potential for development as nano-therapeutic modalities for tumor treatment. Cerium oxide nanoparticles modulate the metabolic gene expression in GBM derived cell lines [ABSTRACT FROM AUTHOR]

Elemental diffusion in ceramics can modulate the conductivity as well as fuel cell performance. Here, we report the effect of diffusion on NiO coated samarium doped ceria (SDC) with temperature and correlated with conductivity. NiO thin film was deposited using electron beam physical vapor deposition over the pre-sintered SDC substrate and subsequently treated at 800 °C, 1000 °C, and 1200 °C. Depth profiling analysis across NiO-SDC hetero-interface using FESEM-EDAX revealed that the width of the diffusion zone increased with temperature. All the constituent ions like Ni, Sm and Ce diffuse mutually without forming any impurity phases at the NiO-SDC interface. The estimated diffusivity values demonstrated that the nickel predominantly diffuses through the grain boundary of SDC. The constituent cations were found to diffuse several hundred nanometers through grain boundaries at a temperature of 1200 °C. An increase in the electrical conductivity was observed in proportion to the width of the diffusion layer. The diffusion of nickel predominantly along the grain boundary reduced the grain boundary resistance by altering the space charge potential at the NiO-SDC interface. Our study demonstrates that the modification of grain boundary through the controlled diffusion of metal ions reduce the resistance for oxygen ion transport in NiO-SDC electrolyte. Unlabelled Image • The effect of diffusion with temperature across NiO-SDC was investigated. • Diffusion length across NiO-SDC interface increased with temperature. • The conductivity of NiO-SDC increased in proportion to the diffusion length. • Diffusion along the grain boundary lowered the resistance. [ABSTRACT FROM AUTHOR]

Abstract The current study focus on the exchange bias properties of Ni/NiO ferromagnetic-antiferromagnetic nanocomposite by fabricating Ni (FM) using a one-step solution combustion method. The prepared Ni nanoparticles were oxidized at 400 °C for different time durations (τ = 3, 6, 12, 24, 48, 72, 96, 120, 144 and 168 h) in the ambient atmosphere to grow NiO (AFM). The X-ray diffraction pattern of the Ni/NiO nanocomposite indicate good crystallinity of the samples. Raman spectroscopy exhibited a short-range magnon excitation around 1400 cm−1 that indicate the contribution of AFM exchange energy between the Ni2+-O2--Ni2+ chain in the composites. The presence of Ni and NiO phases were confirmed by room temperature magnetization measurement. For the better understanding of the exchange bias of the Ni/NiO nanocomposite subjected to heat treatment for several hours (0–168 h), zero-field cooled and field cooled M-H and M-T measurements were made. The hysteresis loop shift along the field axis and enhanced coercivity values shows the exchange bias effect in the Ni/NiO structure in the controlled oxidation process. The Ni and NiO interfacial effect and phase fraction have significant effect on the observed exchange bias. Moreover, finite size effects contribution on the antiferromagnetic exchange and spin glass features observed at a temperature of 24 K of the Ni/NiO system contribute to the large exchange bias and enhanced coercivity. Graphical abstract Image 1 Highlights • Combustion synthesized Ni nanoparticles were oxidized to form Ni/NiO composite. • The exchange interaction between Ni and NiO varies with Ni content. • Large exchange bias and coercivity values were observed at a lower Ni content. • A spin glass feature observed at 24 K in the Ni/NiO arise from exchange anisotropy. • Dual exchange bias (positive and negative) were also observed. [ABSTRACT FROM AUTHOR]

Excess production of reactive oxygen species (ROS) such as hydroxyl (HOṖ) and superoxide (O2Ṗ−) radicals affects the metabolic processes and plays a major role in diseases like cancer. Defect-structured nanoceria is a potential material for mimicking various natural antioxidant enzymes. However, tuning the oxygen vacancy defects through a simple synthetic strategy still remains a challenge. Due to its multi-enzymatic nature, ceria exhibits both pro-oxidant and anti-oxidant properties simultaneously which is vaguely understood and seriously limits its scope in therapeutics. Herein, we report the preparation of nanoceria using a combustion method under various fuel (lean, stoichiometric and excess) conditions and its influence on size and oxygen defect concentration is correlated with the structural, toxic and antioxidant properties. The smaller size and higher number of oxygen vacancy (Ce3+ sites) defects achieved under fuel lean conditions significantly improved the antioxidant and radical scavenging properties as evidenced by enzyme kinetics. At low concentration, ceria exhibits protective effects (eliminates HOṖ radicals and H2O2) but at a higher concentration, it exhibits oxidase activity by generating O2Ṗ− radicals irrespective of the pH conditions. Our results clearly demonstrate the activation of selective enzyme mimetic properties by controlling the ceria concentration which is of the utmost importance in antioxidant therapeutic and diagnostic applications. [ABSTRACT FROM AUTHOR]

The low oxygen tension characterizing the core glioblastomas (GBMs) and other solid tumors is known to cause a metabolic shift within tumors. This lowers the pH and simultaneously increases the ROS (O2Ṗ−, HOṖ, H2O2etc.,) accumulation which eventually facilitates the tumor resistance to chemo/radiotherapy. Herein, we report the biomimetic antioxidant properties of cerium oxide nanoparticles (CNPs) under physiological and tumor microenvironment-like conditions in vitro using a GBM cell line. CNPs were synthesized in a single step combustion method and exhibited selective cytotoxicity under tumor microenvironment-like conditions. Furthermore, the peroxidase-like activity of the CNP nanoparticles was modulated by tumor microenvironment-like conditions (pH 6.5 and 1.5% O2) due to the redox transformation between the Ce3+↑ Ce4+ states of the cerium oxide nanoparticles under different conditions. When incubated with CNPs, a remarkable variation in the oxidative stress was observed from the measured MDA levels. Combined results from a peroxidase assay, MDA assay and TBARS assay revealed size and pH dependent activity which could have significant implications towards the tumor specific activity. The results are promising for the use of CNPs for tumor therapy and warrant further studies using both in vivo and in vitro models on their possible therapeutic potential. [ABSTRACT FROM AUTHOR]

The structural, electrical and optical property of nickel oxide thin films deposited by electron beam physical vapour deposition were investigated with respect to substrate temperature ( T s = 100, 300, and 450 °C). In spite of the amorphous nature of the substrate (quartz), depending on the substrate temperature either a preferred or polycrystalline NiO growth was observed. A (200) preferential orientation resulted at 100 °C while at 300 and 450 °C the NiO films were oriented along (111) and (220) planes. The NiO films obtained at T s = 100 °C was highly transparent compared to the polycrystalline films due to the low light scattering of (200) film. The conductivity of NiO films measured at 100 °C was found to be three orders higher than the films obtained at T s = 450 °C. Thus, the orientation was found to be influencing optical and electrical properties of NiO films. [ABSTRACT FROM AUTHOR]

Recently, the conversion of 4-nitrophenol to 4-aminophenol via metal-supported oxide catalysts has attracted significant attention because of its potential applications. The main objective of this study was to demonstrate the crucial role of support materials in heterogeneous catalysts with inherent redox cycling features. The metals supported on these redox active materials can significantly alter the catalytic performance in a synergistic manner. For this, the catalytic hydrogenation of Au–ceria, prepared by altering the annealing–impregnation procedures, was investigated in terms of the size of gold and support material and their redox chemistry. The study clearly shows the variation in the catalytic activity of gold supported on the as-prepared and annealed ceria surface. This variation was due to the fact that the mutual interactions at the interface between absorbed Au and cerium oxide were certainly different in the as-prepared and annealed ceria surfaces with respect to surface chemistry and size of the particles. The redox nature of ceria and partial oxidation of gold on the surface of CeO2 were involved in the catalytic reduction process. [ABSTRACT FROM AUTHOR]

Influential role of fuel to oxidizer ratio (F/O) as the controlling parameter in combustion synthesis of europium doped cerium oxide was studied in terms of defect chemistry, optical property and antioxidant capacity. Europium (5 mol%) doped cerium oxide nanoparticles synthesized by solution combustion in fuel deficient (F/O=0.6, 1.1) and stoichiometric (F/O=1.6) conditions resulted in size ranging from 6 to 25 nm while excess fuel (F/O=2.1) lead to the lower size of 17 nm. Raman spectroscopic analysis showed the formation of intrinsic and europium ion induced extrinsic oxygen vacancies and the defect concentration was found to be decreasing with F/O ratio. Photoluminescence emission was dominated by magnetic dipole transition in F/O=0.6, 1.1 and electrical dipole in F/O=1.6, 2.1 which resulted in a persistent luminescence. Fenton reaction generated hydroxyl radical scavenging activity was influenced by the surface oxygen vacancy concentration and crystallites size. In addition to size and defect, morphology of the nanoparticle plays a significant role in determining the antioxidant efficacy. [ABSTRACT FROM AUTHOR]

Purpose: Environmental pollutant Bisphenol A (BPA) strongly interacts with insulin resistance, which leads to type 2 diabetes mellitus (T2DM). Uncontrolled glucose levels in both blood and urine develops vascular complications in T2DM patients. However, glucose-controlled diabetic patients are also affected by vascular complications due to vascular calcification, and there is a lack of clinically relevant data on BPA levels available in patients with T2DM-associated vascular complications due to vascular calcification. Therefore, we measured BPA levels in T2DM-associated vascular complications and correlated systemic BPA levels with vascular calcification-related gene expression. Methods: This study included 120 participants with T2DM and its associated vascular complications. Serum and urinary BPA were estimated using an ELISA kit, and gene expression of the study participants in peripheral blood mononuclear cells (PBMCs) was studied with quantitative real-time PCR. Results: Serum and urinary BPA levels were higher in T2DM and its associated vascular complications with CVD and DN patients compared to control. Both Serum and urinary BPA had higher significance with Sirt1 (p < 0.001, p < 0.001), Runx2 (p < 0.01, p < 0.001) and IL-1beta (p < 0.001, p < 0.02) gene expression in the study groups, but, TNF-alpha significant with Serum BPA (p < 0.04), not urinary BPA (p < 0.31). Conclusion: BPA levels were positively correlated with lower Sirt1 and increased Runx2 in T2DM-associated vascular complications patients. Also, higher expression of IL-1beta and TNF-alpha was observed in T2DM-associated vascular complications patients. Our study is the first to associate BPA levels with vascular calcification in patients with T2DM and its associated vascular complications. [ABSTRACT FROM AUTHOR]

Mimicking photosynthesis using NADH is a sustainable method to convert CO 2 and mitigate global warming. Here, Cu nanorods with twin crystal structure on glassy carbon (GC) were prepared by a cyclic electrodeposition method with voltage from −0.2 V to −1.0. The prepared CuGC electrodes were used for the electrochemical NADH regeneration and electroenzymatic CO 2 reduction at −1.0 V using formate dehydrogenase from Candida boidinii . The selective activation of NADH (1,4-NADH) approached 67% as the deposition cycle number increased. The electron mediator [Cp*Rh(bpy)Cl]Cl complex (Rh(III)) was used to obtain nearly 100% active NADH on the CuGC electrode. The electron transfer rate to Rh(III) is crucial for optimal NADH regeneration: Rh(III) should be reduced to RhH quickly as it has the capability to decompose NADH catalytically. This allows sufficiently high NAD + conversion and NADH regeneration reaction rates for the electroenzymatic CO 2 reduction to formate. The optimum concentrations of Rh(III) and NAD + were estimated to be 0.25 and 1.00 mM, respectively. For the CuGC electrode prepared with 300 deposition cycles, the formate formation rate was estimated to be (6.28 ± 0.02) × 10 −3 μmol/mg Cbs FDH /min, a three-fold increase compared to previously reported results on Cu foil electrode. [ABSTRACT FROM AUTHOR]