Oxide Research Articles

Reactivity and potential mobility of metals in human-impacted harbor sediments (port of Rotterdam, the Netherlands)

Abstract Purpose Vast amounts of harbor sediments are being dredged every year globally. These sediments are often enriched in potentially toxic elements (PTEs), the abundance and potential mobility of which are important for sustainable harbor management practices. In this study, we investigate metal (especially PTE) distribution, abundance, and reactivity in sediments along a salinity gradient in the waterways of Europe’s largest harbor, the Port of Rotterdam. Materials and methods Bulk surface sediments were analyzed for general physicochemical properties (e.g. grain size, total metal concentration). From selected locations covering the local salinity gradient, sediments were subjected to three independent chemical extractions to determine chemically reactive metal pools. Additionally, metal retention in two contrasting sediments (high versus low salinity) was further explored using pH-dependent leaching experiments in combination with a geochemical model. Results and discussion The majority of the investigated sediments consisted predominantly of silt and were rich in organic matter. Concentrations of Cd, Pb, Zn, Cu decreased with increasing salinity. Concentrations of Al, Fe, V correlated negatively with grain size, because these geogenic metals are enriched in fine-grained silicates. Results from the chemical metal extractions showed clear differences in the reactivity and mobility potential of metals, that could be grouped into four clusters. The combined chemical and modeling results indicate that sorption onto metal (oxyhydr)oxides and organic matter as well as precipitation of metal sulfides and carbonates control metal retention. High reactivity and mobility potential were observed for Pb, Cd, Zn, particularly at low pH. Limited spatial variability in metal chemistry along the salinity gradient indicates that the highly variable depositional conditions have little impact on metal behaviors. Conclusions Chemical extractions and pH-dependent leaching experiments revealed distinguishing metal reactivities from four clusters. Our results provide insight into metal distribution in the dynamic estuarine environment of the Port of Rotterdam and highlight the importance of understanding chemical speciation in addition to abundance for harbor sediment management.

Polyvinyl Alcohol Nanofibers with Embedded Two-Dimensional Nanomaterials and Metal Oxide Nanoparticles: Preparation, Structural Characterization, and Biological Activity

Eco-friendly iron and manganese oxide nanoparticles (Fe2O3 and Mn2O3) were synthesized and integrated into graphene sheets to form uniform composites. These composites were then embedded in polyvinyl alcohol (PVA) fibers using electrospinning. Comprehensive characterization of the composites and the final composite fibers was conducted using XRD, FE-SEM, and FTIR to analyze their structural complexity and morphological differences. The antibacterial efficacy of the resulting PVA nanofibers was evaluated against Escherichia coli, which is a common pathogen in hospital environments. The results show a significant bactericidal effect against these bacteria, which highlights their potential in medical applications, such as functional bandages and wound dressings. This study paves the way for potential commercial applications of these nanofibers in healthcare settings.

Mechanistic paradigms of immunotoxicity, triggered by nanoparticles - a review.

Nanoparticles (NPs) possess the ability to penetrate cells and elicit a rapid and targeted immune response, influenced by their distinct physicochemical properties. These particles can engage with both micro and macromolecules, thereby impacting various downstream signaling pathways that may lead to cell death. This review provides a comprehensive overview of the primary mechanisms contributing to the immunotoxicity of both organic and inorganic nanoparticles. The effects of carbon-based nanomaterials (CNMs), including single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, and metal oxide nanoparticles, on various immune cell types such as macrophages, neutrophils, monocytes, dendritic cells (DCs), antigen-presenting cells (APCs), and RAW 264.7 cells are examined. The immune responses discussed encompass inflammation, oxidative stress, autophagy, and apoptosis. Additionally, the roles of pro-inflammatory cytokines such as IL-1β, IL-6, TNF-α, and IFN-γ, along with JAK/STAT signaling pathways, are highlighted. The interaction of NPs with oxidative stress pathways, including MAPK signaling and Nrf2/ARE signaling, is also explored. Furthermore, the mechanisms by which nanoparticles induce damage to organelles such as lysosomes, the endoplasmic reticulum, exosomes, and Golgi bodies within the immune system are addressed. The review also emphasizes the genotoxic and epigenetic mechanisms associated with the immunotoxicity of NPs. Recent advancements regarding the immunotherapeutic potential of engineered NPs are reported. The roles of autophagy and apoptosis in the immunotoxicity of NPs merit further investigation. In conclusion, understanding how engineered nanoparticles modulate immune responses may facilitate the prevention and treatment of human diseases, including cancer and autoimmune disorders. The potential development of new vaccines utilizing engineered NPs could pave the way for innovative approaches in the field of immunotherapy.

Nanostructured Ceria‐Niobia Catalyst for Selective Synthesis of N‐benzylideneanilines

The shape and structure engineering of metal oxide nanomaterials are the potential strategies to optimize surface‐active sites with tunable selectivity for heterogeneous catalysis. This work reports the synthesis of two types of nanostructured CeO2‐Nb2O5 catalysts: (i) one‐pot hydrothermal synthesis of CeO2‐Nb2O5 (CeNb2O5‐HTS) and (ii) CeO2 impregnation on hydrothermally synthesized Nb2O5 nanorods (CeNb2O5‐WI) to elucidate the role of particle shape and CeO2 addition in the structure‐activity efficacy of Nb2O5 nanocatalyst for the selective oxidative C‐N coupling of benzyl alcohol with aniline to produce N‐benzylideneaniline (NBA). The characterization studies showed nanorod morphology of Nb2O5 and high dispersion of CeO2 on Nb2O5 nanorods in the CeNb2O5‐WI catalyst with strong acidic sites and more oxygen vacancies. Consequently, a significantly enhanced catalytic activity was achieved with CeNb2O5‐WI nanocatalyst in the coupling of benzyl alcohol and aniline with 96% yield to NBA, whereas 62% conversion of aniline with 92% selectivity to NBA was obtained with pure Nb2O5 nanorods. In contrast, the CeNb2O5‐HTS catalyst gave 37% conversion of aniline only. The versatile efficiency of the CeNb2O5‐WI nanocatalyst is showcased by synthesizing various functional NBA products. The CeNb2O5‐WI catalyst can be recycled 5 times without much variation in NBA selectivity by achieving reasonably good conversion of aniline.

Interplay Between Calcination Temperature and Alkaline Oxygen Evolution of Electrospun High-Entropy (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 Nanofibers.

Spinel-structured transition metal (TM) oxides have shown great potential as a sustainable alternative to platinum group metal-based electrocatalysts. Among them, high-entropy oxides (HEOs) with multiple TM-cation sites are suitable for engineering octahedral redox-active centers to enhance the catalyst reactivity. This paper reports on the preparation of electrospun (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 nanofibers (NFs) and their evaluation as electrocatalysts. Its main aim is to unveil the nanostructural features that play a key role in the alkaline oxygen evolution reaction. Differing calcination temperature (300-800°C) and duration (2 or 4h) leads to different morphology of the NFs, crystallinity of the oxide, density of defects, and cation distribution in the lattice, which reflect in different electrocatalytic behaviors. The best performance (overpotential and Tafel slope at 10mAcm-2: 325mV and 40mVdec-1, respectively) pertains to the NFs calcined at 400°C for 2h. To gain a deeper understanding of their electrocatalytic properties, the pristine NFs are investigated by a combination of analytical techniques. In particular, broadband electric spectroscopy reveals that the mobility of oxygen vacancies in the best electrocatalyst is associated to very fast local dielectric relaxations of metal coordination octahedral geometries and experimentally demonstrates the key role of O-deficient octahedra.

Stress‐Relieving Protective Elastomeric Interphase for Stable Ni‐rich Cathodes

AbstractAnisotropic volume changes in primary particles of layered Ni‐rich transition metal oxides generate mechanical stresses during electrochemical cycling. This results in structural degradation and side reactions that deteriorate battery performance. To address this issue, a cross‐linked epoxy natural rubber (CENR) is employed as the protective elastomeric interphase. The viscoelastic properties of CENR facilitated a strong adhesion to the surface of Ni‐rich cathodes, thereby helping alleviate mechanical stresses during cycling. This approach maintained the structural integrity of the Ni‐rich cathodes and suppressed detrimental interfacial reactions. Consequently, the fortified Ni‐rich cathode retained 95.9% of its capacity after 300 cycles at 0.5 C and 82.8% after 500 cycles at 1 C. This study highlights the essential role of elastomeric materials in stabilizing Ni‐rich cathodes and offers insights that can enable the development of additional protective elastomeric layers for battery electrode materials.

Bismuth sensitized iron oxide on exfoliated graphene oxide (Bi–Fe2O3@GO) for oxygen evaluation reaction

Electrochemical water splitting is a promising approach towards a sustainable and renewable energy source. However, the demand for high anodic potential and sluggish kinetics of oxygen evolution reaction (OER) restrict the efficiency and feasibility of the water-splitting process. In this quest, transition metal oxides and alloys are considered potential candidates owing to their natural occurrence and high redox potential for OER. However, many associated challenges in their use are still there to be addressed. Here, we designed a new class of bismuth-doped iron oxide on exfoliated graphene oxide by optimizing the metal loading on the conductive support to facilitate the flow of charge during catalysis. The catalytic ability of the synthesized Bi-doped nanocomposites was evaluated in activating the OER under extreme alkaline conditions (1 MKOH). On screening different combinations, 20Bi–Fe2O3@GO was identified as the most efficient and sustainable electrocatalyst even under harsh operating conditions, with an onset potential of 1.48 V and a Tafel slope of 65 mV/dec. The current study offers a new class of Bi-doped electrocatalysts, where the precise doping of Bi and the optimized loading of metal was found the key to achieving low onset potential and high current density to initiate OER.Graphical abstract

Surface restructuring and predictive design of heterogeneous catalysts.

Heterogeneous catalysts, which often consist of metal nanoparticles loaded on supports such as metal oxides, can undergo several types of restructuring under reaction and catalytic conditions. Advanced characterizations now allow the surface structure of a catalyst in a gas phase to be determined to some extent. Metal nanoparticles may experience changes in shape, surface structure and composition, and atomic packing in response to the pressure of a reactant or product gas, temperature, and reaction between the catalyst surface and gas. Metal oxide supports can partially or fully encapsulate metal nanoparticles, altering their electronic structure and reactivity. Restructuring is a main approach to creating active catalytic sites. The rational design of catalysts must anticipate that such restructurings can occur under reaction or catalytic conditions and gain knowledge of how they occur. It is expected that computational studies can predict such restructurings and that advanced synthesis may be used to prepare pristine catalysts with enhanced resistance to restructurings.

Similarity between oxygen evolution in photosystem II and oxygen reduction in cytochrome c oxidase via proton coupled electron transfers. A unified view of the oxygenic life from four electron oxidation-reduction reactions.

Basic concepts and theoretical foundations of broken symmetry (BS) and post BS methods for strongly correlated electron systems (SCES) such as electron-transfer (ET) diradical, multi-center polyradicals with spin frustration are described systematically to elucidate structures, bonding and reactivity of the high-valent transition metal oxo bonds in metalloenzymes: photosystem II (PSII) and cytochrome c oxidase (CcO). BS hybrid DFT (HDFT) and DLPNO coupled-cluster (CC) SD(T0) computations are performed to elucidate electronic and spin states of CaMn4Ox cluster in the key step for oxygen evolution, namely S4 [S3 with Mn(IV) = O + Tyr161-O radical] state of PSII and PM [Fe(IV) = O + HO-Cu(II) + Tyr161-O radical] step for oxygen reduction in CcO. The cycle of water oxidation catalyzed by the CaMn4Ox cluster in PSII and the cycle of oxygen reduction catalyzed by the CuA-Fea-Fea3-CuB cluster in CcO are examined on the theoretical grounds, elucidating similar concerted and/or stepwise proton transfer coupled electron transfer (PT-ET) processes for the four-electron oxidation in PSII and four-electron reduction in CcO. Interplay between theory and experiments have revealed that three electrons in the metal sites and one electron in tyrosine radical site are characteristic for PT-ET in these biological redox reaction systems, indicating no necessity of harmful Mn(V) = O and Fe(V) = O bonds with strong oxyl-radical character. Implications of the computational results are discussed in relation to design of artificial systems consisted of earth abundant transition metals for water oxidation.

Review of Voltage Balancing Techniques for Series-Connected SiC Metal–Oxide–Semiconductor Field-Effect Transistors

Review of Voltage Balancing Techniques for Series-Connected SiC Metal–Oxide–Semiconductor Field-Effect Transistors

Gold‐Assisted Exfoliation of Large‐Area Monolayer Transition Metal Dichalcogenides: From Interface Properties to Device Applications

AbstractSemiconductor transition metal dichalcogenides (TMDs), such as MoS2, are currently regarded as key‐enabling materials for sub‐1 nm channel transistors, beyond‐complementary metal–oxide–semiconductor electronic and optoelectronic devices and sensors. Owing to this wide application potential, several bottom‐up and top‐down synthesis approaches for these materials have been explored so far. Despite the huge progresses in scalable deposition methods (such as chemical vapor deposition, metal–organic chemical vapor deposition), exfoliated layers from bulk crystals still represent the benchmark for record electronic properties of TMDs. Among exfoliation approaches, metal‐assisted mechanical exfoliation emerges as the most effective method to separate large‐area (mm2 to cm2) single‐crystalline monolayer membranes of TMDs (and many other 2D materials) from the parent bulk crystals. This paper reviews the state‐of‐the‐art in this field, from current understanding of MoS2 exfoliation mechanisms on Au (considered as a model system), to the main device applications of as‐exfoliated and transferred large‐area MoS2 membranes (including Au/MoS2/Au memristors, MoS2 photodetectors, and field‐effect transistors). Perspectives of this method in the realization of arrays of 2D heterojunction devices, including Moirè superlattice devices, and open challenges for its widespread application are finally discussed.

Engineering the Coherent Phonon Transport in Polar Ferromagnetic Oxide Superlattices.

Artificial superlattices composed of perovskite oxides serves as an essential platform for engineering coherent phonon transport by redefining the lattice periodicity, which strongly influences the lattice-coupled phase transitions in charge and spin degrees of freedom. However, previous methods of manipulating phonons have been limited to controlling the periodicity of superlattice, rather than utilizing complex mutual interactions that are prominent in transition metal oxides. In this study onoxide superlattices composed of ferromagnetic metallic SrRuO3 and quantum paraelectric SrTiO3, phonon modulation by controlling the geometry of superlattice in atomic-scale precision is realized, demonstrating the coherent phonon engineering using structural and magnetic phase transitions. By modulating the interface density, coherent-incoherent crossover of the phonon transport at room temperature is observed, which is coupled with a change in interfacial structural continuity. Upon cooling, the close relation between phonon transport and multiple phase transitions is identified. In particular, the enhancement of the polar state in SrTiO3 layer at ≈200K leads to the weakening of phonon coherence and a further reduction of thermal conductivity in superlattices compared to the bulk limit. These findings provide a guide to developing future thermoelectric nanodevices by engineering the coherence of phonons via the design of complex oxide heterostructures.

Specific and high-affinity adsorption of volatile organic compounds on titanium dioxide surface.

The interaction between metal oxides and volatile organic compounds (VOCs) from the ambient atmosphere plays an important role in environmental and catalytic applications. Previous scanning probe microscopy and x-ray spectroscopy studies revealed surprisingly that the TiO2 [rutile (110)] surface selectively adsorbed atmospheric carboxylic acids, which typically exist in only parts-per-billion concentrations. In this work, we used in situ sum-frequency vibrational spectroscopy to study the interaction between rutile (110) and typical VOC molecules, including formic acid, acetic acid, and formaldehyde. Spectra from all three adsorbed molecules on rutile (110) were similar to the rutile surface spectrum in the ambient atmosphere, showing a broad resonance near 2950cm-1 that can be attributed to the bridging bidentate adsorption of corresponding compounds. In contrast, on a fused silica surface, a molecular monodentate adsorption configuration was observed for all the molecules, with aliphatic carbons appearing to be the dominant adventitious species.

A new compact potentiometric electrode for pH monitoring built upon a glass substrate with a Ce-doped SnO2 layer.

A novel compact potentiometric electrode specifically designed for pH monitoring, featuring a good construction on a glass substrate coated with a cerium-doped tin oxide (Ce-doped SnO2) layer. The Ce-doped SnO2 thin film was created by spray-pyrolysis it on a glass substrate. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) were used to characterize the deposited metal oxide coating. As a miniature potentiometric electrode, the synthesized Ce-doped SnO2/glass substrate was utilized to measure a broad pH range (pH 2-12) in aqueous solutions. The electrode had a perfect near-Nernstian response (slope of -58.6 ± 0.7 mV per decade), high potential stability, mechanical durability, and great selectivity towards some common interfering cations and anions. These characteristics made it ideal for quality control and assurance purposes. The electrode's performance parameters and validation measurements were assessed using established procedures. The Ce-doped SnO2-based electrode satisfactorily monitored the pH of several genuine water, drink, and fruit juice samples, and the data compared well with those obtained using a traditional pH glass electrode. The integration of Ce-doped SnO2 as the active material marks a significant advancement, providing enhanced electrochemical stability, improved sensitivity, and a wider pH detection range compared to conventional electrodes. The compact design not only reduces the sensor's footprint but also facilitates its application in miniaturized and portable pH monitoring devices, making it highly suitable for advanced analytical and environmental sensing applications.

Biogenic Nanoparticles as Safer Alternatives for Gastric Ulcers: An Update on Green Synthesis Methods, Toxicity, and Their Efficacy in Controlling Inflammation.

Peptic ulcers, affecting approximately 10% of the global population, can result from factors such as stress, alcohol use, smoking, NSAIDs, Helicobacter pylori infection, and genetic predisposition. Plant-based medicines are gaining recognition for their therapeutic potential, including in the treatment of peptic ulcers. Green chemistry methods for the biological synthesis of nanoparticles (NPs) provide a sustainable alternative to traditional chemical techniques. These nanoparticles, particularly metallic NPs and metal oxides synthesized from plant extracts, offer promising anti-ulcer properties. This review highlights research from 2000 to 2024 on the use of green-synthesized nanoparticles and their role in peptic ulcer treatment, focusing on their therapeutic mechanisms and potential benefits. For this purpose, an electronic search of published research and review articles was conducted in PubMed, Scopus, Science Direct, Cochrane databases, and Google Scholar.

Enhancement of Thermoelectric Properties of Zinc Oxide Composites via Doping with Active Metal Oxide

Enhancement of Thermoelectric Properties of Zinc Oxide Composites via Doping with Active Metal Oxide

Low-frequency noise analysis on asymmetric damage and self-recovery behaviors of ZnSnO thin-film transistors under hot carrier stress

The need for understanding the low-frequency noise (LFN) of metal oxide semiconductor thin-film transistors (TFTs) is increasing owing to the substantial effects of LFN in various circuit applications. A focal point of inquiry pertains to the examination of LFN amidst bias stress conditions, known to compromise TFT reliability. In this study, we investigate the effects of hot carrier stress (HCS) on zinc tin oxide (ZTO) TFTs by low-frequency noise (LFN) analysis. Asymmetric damage caused by HCS is analyzed by measuring the power spectral density at the source and drain sides. The excess noise generated by the HCS is analyzed with consideration of trap density of states (DOS). It is revealed that the needle defects are generated during the HCS, significantly affecting the LFN characteristics of the ZTO TFTs. Additionally, we observe a self-recovery behavior in the devices and demonstrate the relevant changes in the LFN characteristics following this phenomenon. This study provides valuable insights into the LFN characteristics of ZTO TFTs under HCS conditions and sheds light on the underlying mechanisms.

2D and 3D Nanostructured Metal Oxide Composites as Promising Materials for Electrochemical Energy Storage Techniques: Synthesis Methods and Properties

2D and 3D Nanostructured Metal Oxide Composites as Promising Materials for Electrochemical Energy Storage Techniques: Synthesis Methods and Properties

Recent advances in nanomaterial-enabled chemiresistive hydrogen sensors.

With the growing adoption of hydrogen energy and the rapid advancement of Internet of Things (IoT) technologies, there is an increasing demand for high-performance hydrogen gas (H2) sensors. Among various sensor types, chemiresistive H2 sensors have emerged as particularly promising due to their excellent sensitivity, fast response times, cost-effectiveness, and portability. This review comprehensively examines the recent progress in chemiresistive H2 sensors, focusing on developments over the past five years in nanostructured materials such as metals, metal oxide semiconductors, and emerging alternatives. This review delves into the underlying sensing mechanisms, highlighting the enhancement strategies that have been employed to improve sensing performance. Finally, current challenges are identified, and future research directions are proposed to address the limitations of existing chemiresistive H2 sensor technologies. This work provides a critical synthesis of the most recent advancements, offering valuable insights into both current challenges and future directions. Its emphasis on innovative material designs and sensing strategies will significantly contribute to the ongoing development of next-generation H2 sensors, fostering safer and more efficient energy applications.

Highly Selective Electroreduction of Carbon Dioxide Using Defect-Driven Catalysis.

The production of methanol from the electrochemical reduction of CO2 is a promising method of mitigating climate change while simultaneously producing a useful liquid fuel. In this study, we design self-assembled monolayers (SAMs) of thiols on metal and metal oxide electrodes that operate via cooperative catalysis between the thiolated surface sites and exposed electrode defect sites. This defect-driven mechanism enables the fabrication of SAM-modified ZnO electrodes that yield methanol with an extraordinarily high Faradaic efficiency of up to 92%. To understand the origin of this high selectivity, we study the effect of the chain length of the alkanethiols, different tail functional groups, and applied voltages on catalyst performance. These results combined with density functional theory calculations give a detailed atomic-level understanding of catalyst operation. Furthermore, the SAM linkage tolerates CO2 reduction conditions, and the catalyst's excellent selectivity for methanol remains high after 10 h of continuous conversion. Taken together, these findings with SAM-based electrodes convey a new and facile design strategy for the creation of highly selective CO2 reduction electrocatalysts.