Transition Metal Oxide Nanoparticles Research Articles

Structurally ordered FeCo@FeCoOx@NC dual-shell nanoparticles synthesized under micro-oxygen conditions: An efficient cocatalyst for BiVO4 photoelectrochemical water oxidation

Electrocatalysts are usually integrated onto light-absorbing semiconductors to form efficient photoelectrochemical water-splitting systems. Transition metal oxide nanoparticles serve as excellent electrocatalysts, but exhibit poor performance as cocatalysts for photoelectrodes. To address this issue, a FeCo@FeCoOx@NC dual-shell nanoparticle (consisting of a FeCo alloy core, an intermediate FeCoOx shell, and an outermost graphitic carbon shell) was prepared under micro-oxygen conditions. The FeCo alloy has the dual functions of rapid hole storage and efficient charge transport, while the FeCoOx layer acts as active sites to accelerate the kinetics of the water oxidation reaction and the graphitic carbon protects the internal structure of the nanoparticles. Under the synergistic effect of FeCo@FeCoOx@NC and NiFeOx cocatalysts, the injection efficiency and separation efficiency of BiVO4 photoanode almost reach 100 %, and the photocurrent density reaches 6.85 mA cm−2 (1.23 VRHE, AM 1.5 G), marking the highest reported value to date.

Unveiling the Structural and Chemical Evolution of Layered Oxide Cathode for Na‐Ion Batteries Induced by Water Vapor

AbstractNa‐ion batteries (NIBs) have received considerable attention as promising alternatives to lithium‐ion batteries, particularly for low‐speed electric vehicles and large‐scale energy storage applications. Currently, layered oxide compounds are considered the most important cathode materials for NIBs. However, they suffer from reduced capacity and a shortened lifespan when exposed to water vapor during storage or battery assembly. This article elaborates on the structural and chemical evolution of NaNi1/3Fe1/3Mn1/3O2 (NFM) cathode at the atomic scale in a pure water vapor environment. The Na+/H+ exchange induces the formation of a spinel‐like phase via a multi‐site nucleation mechanism. This transition preferentially occurs either at the cathode surface or along planar defects such as twin boundaries and grain boundaries. Additionally, numerous microcracks perpendicular to <003> direction appear inside NFM grains, further exacerbating the structural deterioration. Upon prolonged exposure to water vapor, NFM grains decompose into a mixture of Na2O and transition metal oxide nanoparticles (FeO, NiO, and MnO), accompanied by the generation of oxygen gas. This research provides a comprehensive atomic‐scale insight into the water vapor instability mechanism of layered oxide cathodes, offering guidance for the design and manufacture of the next generation of water vapor‐tolerant layered oxide cathodes in NIBs.

Integrated in silico analysis of transcriptomic alterations in nanoparticle toxicity across human and mouse models

Nanoparticles, due to their exceptional physicochemical properties are used in our day-to-day environment. They are currently not regulated which might lead to increased levels in the biological systems causing adverse effects. However, the overall mechanism behind nanotoxicity remains elusive. Previously, we analysed the transcriptome datasets of copper oxide nanoparticles using in silico tools and identified IL-17, chemokine signaling pathway, and cytokine-cytokine receptor interaction as the key pathways altered. Based on the findings, we hypothesized a common pathway could be involved in transition metal oxide nanoparticles toxicity irrespective of the variables. Further, there could be unique transcriptome changes between metal oxide nanoparticles and other nanoparticles. To accomplish this, the overall transcriptome datasets of nanoparticles consisting of microarray and RNA-Seq were obtained. >90 studies for 17 different nanoparticles, performed in humans, rats, and mice were assessed. After initial screening, 24 mouse studies (with 196 datasets) and 34 human studies (with 200 datasets) were used for further analyses. The common genes that are dysregulated upon NPs exposure were identified for human and mouse datasets separately. Further, an overrepresentation functional enrichment analysis was performed. The common genes, their gene ontology, gene-gene, and protein-protein interactions were assessed. The overall results suggest that IL-17 and its related pathways might be commonly altered in nanoparticle exposure with lung as one of the major organs affected.

Applications of Titanium Dioxide (TiO2) Nanoparticles in Photocatalysis

Titanium dioxide nanoparticles (TiO2 NPs) are conspicuously preferred as photocatalyst among the transition metal oxide nanoparticles. It exhibited in three polymorphisms of steady state rutile phase while brookite and anatase sustaining in metastable phase. The mixed phases of anatase phase and rarely found brookite phase mostly preferred for the photodegradation applications. The economically affordable along with nontoxic nature on top of excellent opto-electronics and catalytic properties of TiO2 NPs are eminently favorable for the photocatalytic degradation of chemically complex structured numerous organic and inorganic dyes, phenol and phenol-based derivatives, passive microplastics as well as suspended matters, non-biodegradable cytostatic drugs, acetaminophen, pharmaceutical organic waste compounds in addition to water pollutants. The photocatalytic capability of these NPs enhanced by upgrading the structural and morphological nature by opting different synthesis techniques as well preparing the nanocomposites of TiO2 incorporation with other metals. The hydrothermally prepared polymeric membranes of polyvinylidene with TiO2 NPs effectively (more than 90%) removed 17 α–ethinylestradiol from the contaminated water compared to Diclofenac under Uv irradiation. As it fronting the issue of electrostatic repulsion to all other membranes surface. The grafted membrane recorded highest degradation efficiency of 95.4% and best reusability of 90% saturated at fifth recycle for Methylene Blue azo dye compared with blending and dip coating membranes. The TiO2 modified ultrafiltration membranes of Polyvinylidene Fluoride with Dopamine illustrated the 92.6% photocatalytic degradation of Sulfadiazine which is most hazardous and highly resistant to biodegradation. 100% degradation of phenol derivative by TiO2 NPs hybrid polymeric films in visible light irradiation. The degradation efficiency of heterogenous photocatalyst Carbon–TiO2 contained anatase and brookite phased for Methylene Blue dye was 100% while for Rhodamine–B higher than 99% in solar and more than 78% in LED light irradiation. The recent trends for improvisation of photocatalytic ability of TiO2 NPs to enhance the quality of water and hence the mankind are elaborated.

A Review of EPR and Magnetization Investigations of Doped Nanoparticles of Transition Metal Oxides and SiCN: Functional Materials and Spintronic Devices

A Review of EPR and Magnetization Investigations of Doped Nanoparticles of Transition Metal Oxides and SiCN: Functional Materials and Spintronic Devices

Solid state conversion of novel coordinated precursors to visible light active photocatalysts with enhanced photocatalytic activity

The new polydentate N'1,N'3‐bis((E)‐3‐oxopentan‐2‐ylidene)malonohidrazide chelating agent (H2L) and its coordinated complexes of Co2+, Cu2+, and Ni2+ were prepared and characterized by elemental analysis, molar conductance, and spectra (Fourier transform infrared [FT‐IR], ultraviolet–visible spectroscopy [UV–vis], and Fast‐Atom Bombardment Mass Spectrometry (FAB‐MS). Also, thermal and magnetic investigations were conducted. X‐ray single crystal of the H2L ligand revealed a triclinic structure with space group P‐1. In this study, we provide a one‐pot preparation approach for transition metal oxide nanoparticles (NPs) such as CuO, Co3O4, and NiO NPs. The methodology entails the thermal decomposition of coordinated metal precursors in a solid‐state environment, obviating the necessity for agitation and rinsing. The remarkable significance of this method lies in its ability to produce highly pure NPs without the requirement of washing, and it allows for systematic and efficient production. Herein, we propose a large‐scale, environmentally benign and renewable, transition metals oxide NPs such as CuO, Co3O4, and NiO using solid‐state thermal degradation of their coordinated precursors. The NPs are subjected to analysis employing a range of techniques, such as X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), N2 sorpometry (BET), and UV–vis). The photocatalytic activities of the synthesized NPs were assessed using photodegradation of organic contaminants in wastewater.

Metal oxide nanocrystals embedded polypyrrole nanohybrid: Exploring role of interface in photocatalytic hydrogen generation

Photocatalytic water splitting is considered as a sustainable way to produce hydrogen in the water−based energy cycle. Inorganic semiconductors, specifically metal oxides are extensively used as efficient photocatalysts, however, intrinsically poor charge-transfer and wide band gap with lower negative conduction band potential than the hydrogen evolution potential affect the water-splitting efficiency. In view of superior charge-transfer, and tunable energy levels, polymer-based nanohybrids (NHs) have been fabricated using polypyrrole (PPy) nanofibers with a series of transition metal oxides (MO) nanoparticles, namely TiO2, ZnO, CeO2, Fe2O3, NiO, and SnO2. A series of photoanodes have been tested for photoelectrochemical water splitting to elucidate the effect of interfacial charge transfer at the interfaces of NHs. The high photocurrent response of 44 μA cm−2 at 0.9 V vs. Ag/AgCl has been achieved for Fe2O3/PPy. While, ZnO/PPy NHs demonstrated a superior photocatalytic H2 generation rate of ∼162 mmol/g/h, which is ∼27 times higher than pure PPy. Based on energy level calculation, the charge transfer mechanism occurs through p−n junction in TiO2/PPy and SnO2/PPy NHs while the other NHs structures follow a Z−Scheme of charge transfer pathway. This finding opens an avenue for designing highly efficient polymer-metal oxide heterojunctions for water splitting and solar fuel applications.

Trace Ru-tuned NiO/CNT electrocatalysts outperform benchmark Pt for alkaline hydrogen evolution with superior mass activity

The exploitation of highly active and durable electrocatalysts that can replace high-cost Pt/C for hydrogen evolution reaction (HER) is urgently required. The challenge lies in diminishing the usage of noble metals without sacrificing HER activity. In this work, trace Ru-doped transition metal oxides (TMOs) nanoparticles (∼7 nm) with high dispersion loaded by the carbon nanotubes (CNTs) were developed. Specifically, Ru-NiO/CNTs with a low Ru content of 0.94 wt% exhibits excellent alkaline HER activity with the low overpotential of 19 mV and 98 mV to achieve the current density of 10 mA·cm−2 and 100 mA·cm−2, respectively, outperforming Ru/CNTs counterpart and most previously Ru-based nanocatalysts. Notably, the mass activity (1.83 A·mgRu-1) and price activity (301.51 A·dollar-1) of Ru-NiO/CNTs are separately more than 7 times and 18 times higher than that of the commercial 20% Pt/C benchmark. Moreover, the catalyst can operate without activity decay after 100 h long-term stability test. DFT calculation reveals that the synergy effects are originated from (i) the accelerated adsorption and dissociation of H2O by Ru, and (ii) the optimized electronic structure of Ni that tunes the H* adsorption/desorption. Furthermore, we discover that Ru-promoted HER activity shows a metal-dependent relationship (Ni ≈ Cu > Mn > Co > Fe), which can use binding energy shift (ΔE) as a highly correlated descriptor. This work may provide an insightful understanding of Ru dopant for enhanced HER activity.

Electrochemical Sensing of Zinc Oxide and Peroxide Nanoparticles: Modification with Meso-tetrakis(4-carboxyphenyl) Porphyrin

An electrochemical method was developed to investigate the redox properties of zinc oxide (ZnO), zinc peroxide (ZnO2), and sodium-doped zinc peroxide (Na-ZnO2) nanoparticles. The intention was to distinguish the identity of these nanoparticles among themselves, and from other transition metal oxide nanoparticles (TMONPs). Analysis of 3 mM sodium metabisulfite by cyclic voltammetry (CV) produced anodic/cathodic peak currents that are linearly related to the mass of deposited nanoparticles. A graphite working electrode was essential to the oxidation of metabisulfite. ZnO nanoparticles were crucial to the enhancement of metabisulfite oxidation current, and PPy coating could suppress the current enhancement by covering all nanoparticle surfaces. Furthermore, meso-tetrakis(4-carboxyphenyl) porphyrin was demonstrated to be a good chemical reagent that facilitates the differentiation of ZnO from ZnO2 and nanoparticles by CV analysis.

Rapid Crystal Structural, Optical and Morphological Studies of Transition Metal Oxide Nanoparticles and their Photocatalytic Activity

In the present work, we report a green synthesis of cobalt oxide (Co3O4), bismuth oxide (Bi2O3) and cobalt-doped bismuth oxide (Co-doped BiO) nanoparticles using Bambusa seed extract. The green synthesized nanoparticles are characterized using various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy and field emission scanning electron microscopy (FESEM). The phase purity of the synthesized nanoparticles is confirmed with the aid of XRD analysis, and the crystallite sizes are found to be 10.42 nm, 18.85 nm and 61.23 nm for Co3O4, Bi2O3 and Co-doped BiO nanoparticles, respectively. Bond length calculations and functional group analysis are done by FTIR technique. The UV–visible analysis depicts higher optical absorption and band gaps varying from 1.81, 2.65 and 1.87 eV for Co3O4, Bi2O3 and Co-doped BiO nanoparticles, respectively. Changes in the surface morphology are observed from FESEM analysis. In addition, the samples' catalytic efficiency in the breakdown of methylene blue (MB) dye was studied and the effects of various process parameters on the extent of dye removals such as photocatalyst amount, irradiation period, the concentration of dye and pH of the solution were also studied. The pseudo-first-order MB photocatalytic decomposition kinetic model has a high correlation coefficient value (R2 > 0.95). The findings support the use of a Co-doped BiO in the field of photocatalytic applications under natural sunlight.

The Metal-Oxide Nanoparticle-Aqueous Solution Interface Studied by Liquid-Microjet Photoemission.

ConspectusThe liquid-microjet technique combined with soft X-ray photoelectron spectroscopy (PES) has become an exceptionally powerful experimental tool to investigate the electronic structure of liquid water and nonaqueous solvents and solutes, including nanoparticle (NP) suspensions, since its first implementation at the BESSY II synchrotron radiation facility 20 years ago. This Account focuses on NPs dispersed in water, offering a unique opportunity to access the solid-electrolyte interface for identifying interfacial species by their characteristic photoelectron spectral fingerprints. Generally, the applicability of PES to a solid-water interface is hampered due to the small mean free path of the photoelectrons in solution. Several approaches have been developed for the electrode-water system and will be reviewed briefly. The situation is different for the NP-water system. Our experiments imply that the transition-metal oxide (TMO) NPs used in our studies reside close enough to the solution-vacuum interface that electrons emitted from the NP-solution interface (and from the NP interior) can be detected.We were specifically exploring aqueous-phase TMO NPs that have a high potential for (photo)electrocatalytic applications, e.g., for solar fuel generation. The central question we address here is how H2O molecules interact with the respective TMO NP surface. Liquid-microjet PES experiments, performed from hematite (α-Fe2O3, iron(III) oxide) and anatase (TiO2, titanium(IV) oxide) NPs dispersed in aqueous solutions, exhibit sufficient sensitity to distinguish between free bulk-solution water molecules and those adsorbed at the NP surface. Moreover, hydroxyl species resulting from dissociative water adsorption can be identified in the photoemission spectra. An important aspect is that in the NP(aq) system the TMO surface is in contact with a true extended bulk electrolyte solution rather than with a few monolayers of water, as is the case in experiments using single-crystal samples. This has a decisive effect on the interfacial processes that can occur since NP-water interactions can be uniquely investigated as a function of pH and provides an environment allowing for unhindered proton migration. Our studies confirm that water is dissociatively adsorbed at the hematite surface and molecularly adsorbed at the TiO2 NP surface at low pH. In contrast, at near-basic pH the water interaction is dissociative at the TiO2 NP surface.The liquid-microjet measurements presented here also highlight the multiple aspects of photoemission necessary for a full characterization of TMO nanoparticle surfaces in aqueous environments. For instance, we exploit the ability to increase species-specific electron signals via resonant photoemission, so-called partial electron yield X-ray absorption (PEY-XA) spectra, and from valence photoelectron and resonant Auger-electron spectra. We also address the potential of these resonance processes and the associated ultrafast electronic relaxations for determining charge transfer or electron delocalization times, e.g., from Fe3+ located at the hematite nanoparticle interface into the aqueous-solution environment.

Comparative study of photocatalytic degradation of methyl orange using chemically synthesized transition metal oxide nanoparticles

This paper focuses on simple synthesis method of some transition metal oxide nanoparticles and their uses in the photocatalytic degradation of Methyl Orange synthetic dye. MnO2, Fe3O4, Co2O3, CuO, and ZnO nanoparticles are prepared with wet chemical method. Synthesized samples are characterized with an ultraviolet–visible spectrometer (UV–Vis), Fourier transform infrared spectrometer and scanning electron microscope . Photocatalytic degradation of methyl orange with the prepared nanoparticles are studied using UV–Vis spectrometer. All the nanoparticles show different photocatalytic activities towards the methyl orange dye. CuO and ZnO nanoparticles show significantly better results in photocatalysis process amongst all TMO NPs.

ДИЗАЙН НАНОЧАСТИЦ ОКСИДОВ ПЕРЕХОДНЫХ МЕТАЛЛОВ С КОНТРОЛИРУЕМОЙ РАЗМЕРНОСТЬЮ

The paper presents generalized experimental data on the influence of synthesis conditions on the structural features of MeO transition metal oxide nanoparticles in a polymer matrix synthesized by chemical condensation. The synthesis process includes the interaction of aqueous solutions of metal salts of varying concentrations with alkalis in the presence of an aqueous solution of the natural polysaccharide arabinogalactan. Controlled growth of oxide nanoparticles was achieved by encapsulation of emerging NPs in a polysaccharide matrix. The structural properties of the obtained samples were analyzed using X-ray diffraction, IR and UV spectroscopy, and TEM and SEM electron microscopy.

Histidine-Mediated Synthesis of Chiral Cobalt Oxide Nanoparticles for Enantiomeric Discrimination and Quantification.

Chiral transition metal oxide nanoparticles (CTMOs) are attracting a lot of attention due to their fascinating properties. Nevertheless, elucidatingthe chirality induction mechanism often remains a major challenge. Herein, the synthesis of chiral cobalt oxide nanoparticles mediated by histidine (Co3 O4 @L-His and Co3 O4 @D-His for nanoparticles synthesized in the presence of L- and D-histidine, respectively) is investigated. Interestingly, these CTMOs exhibit remarkable and tunable chiroptical properties. Their analysis by x-ray photoelectron, Fourier transform infrared, and ultraviolet-visibleabsorption spectroscopy indicates that the ratio of Co2+ /Co3+ and their interactions with the imidazole groups of histidine are behind their chiral properties. In addition, the use of chiral Co3 O4 nanoparticles for the development of sensitive, rapid, and enantioselective circular dichroism-based sensors is demonstrated, allowing direct molecular detection and discrimination between cysteine or penicillamine enantiomers. The circular dichroism response of the chiral Co3 O4 exhibits a limit of detection and discrimination of cysteine and penicillamine enantiomers as low as 10µm. Theoretical calculations suggest that the ligand exchange and the coexistence of both species adsorbed on the oxide surface are responsible for the enantiomeric discrimination. This research will enrich the synthetic approaches to obtain CTMOs and enable the extension of the applications and the discovery of new chiroptical properties.

Core-shell N-doped carbon embedded Co3O4 nanoparticles with interconnected and hierarchical porous structure as superior anode materials for lithium-ion batteries

Confining Transition metal oxides (TMOs) nanoparticles in porous carbon is an effective strategy to improve its electrochemical performance. Herein, the large grain size Co-based metal-organic framework (Co-MOF) was used as precursor to synthesize core-shell structure of Co3O4 encapsulated in nitrogen-doped carbon (denoted as L-Co3O4@NC). The in-situ synthesized L-Co3O4@NC exhibits a unique interconnected and hierarchical porous structure. Owing to the unique structu Line14ral merits including fast charge transmission and Li+ diffusion, effectively accommodate the volume change, and promote the access of Li+, the L-Co3O4@NC exhibits excellent lithium storage performance in terms of high specific capacity (1389 mAh g−1 at 0.1A g−1 after 50 cycles), enhanced rate capability (1373, 1182 and 945 mAh g−1 at 0.5, 1 and 2 A g−1, respectively), and cycling stability at large current density (1183 mAh g−1 at 1 A g−1 and 960 mAh g−1 at 2 A g−1 after 200 cycles), which outperforms most of recently reported Co3O4 based electrodes. This work provides a new avenue for developing Co-based anode materials with high performance in energy storage field.

The Application of Transition Metal Sulfide Nanomaterials and Their Composite Nanomaterials in the Electrocatalytic Reduction of CO2: A Review

Electrocatalysis has become an important topic in various areas of research, including chemical catalysis, environmental research, and chemical engineering. There have been a multitude of different catalysts used in the electrocatalytic reduction of CO2, which include large classes of materials such as transition metal oxide nanoparticles (TMO), transition metal nanoparticles (TMNp), carbon-based nanomaterials, and transition metal sulfides (TMS), as well as porphyrins and phthalocyanine molecules. This review is focused on the CO2 reduction reaction (CO2RR) and the main products produced using TMS nanomaterials. The main reaction products of the CO2RR include carbon monoxide (CO), formate/formic acid (HCOO−/HCOOH), methanol (CH3OH), ethanol (CH3CH2OH), methane (CH4), and ethene (C2H4). The products of the CO2RR have been linked to the type of transition metal–sulfide catalyst used in the reaction. The TMS has been shown to control the intermediate products and thus the reaction pathway. Both experimental and computational methods have been utilized to determine the CO2 binding and chemically reduced intermediates, which drive the reaction pathways for the CO2RR and are discussed in this review.

Engineering amorphous SnO2 nanoparticles integrated into porous N-doped carbon matrix as high-performance anode for lithium-ion batteries

A facile in-situ preparation strategy is proposed to anchor amorphous SnO2 nanoparticles into the porous N-doped carbon (NC) matrix to fabricate amorphous composite powders (am-SnO2@p-NC), which feature the hierarchically interconnected and well interlaced porous configurations by employing polyvinylpyrrolidone as the soft template. The morphology regulation of the porous structure is precisely realized by adjusting the content of the template and the relationship between structural evolution and electrochemical performance of composite powders is accurately described to explore the optimal template dosage. The results indicate that the am-SnO2@p-NC-50 % composite electrode can deliver the improved lithium storage capacity and cycling performance when the content of the template is controlled at 0.500 g, in which the initial discharge specific capacity is about 1557.6 mAh/g and the reversible value retains at 841.5 mAh/g after 100 cycles at 100 mA/g. Meanwhile, the discharge specific capacity of 869.8 mAh/g is exhibited for the am-SnO2@p-NC-50 % composite electrode after 60 cycles when the current density is recovered from 2000 to 100 mA/g. Moreover, the Li+ ions diffusion coefficient up to about 5.5 × 10−12 cm2/s is calculated from galvanostatic intermittent titration technique tests, which can be partly ascribed to the conductive NC substrate that provides the high electronic conductivity, and partly to the highly porous structure that shortens Li+ ions transfer pathways and guarantees the fast reaction kinetics. Therefore, the hierarchically porous engineering of carbon networks to confine amorphous transition metal oxide nanoparticles is of great significance in the development of high-performance anode materials for lithium-ion batteries.

Overcoming the Trade-Off between Optical Transmittance and Areal Capacitance of Transparent Supercapacitors for Practical Application.

It is substantially challenging for transition metal oxide nanoparticle (NP)-based electrodes for supercapacitors to achieve high transparency and large capacity simultaneously due to the inherent trade-off between optical transmittance (T) and areal capacitance (CA ). This study demonstrates how this trade-off limitation can be overcome by replacing some electrode NPs with transparent tin oxide (SnO2 ) NPs. Although SnO2 NPs are non-capacitive, they provide effective paths for charge transport, which simultaneously increase the CA and T550nm of the manganese oxide (Mn3 O4 ) NP electrode from 11.7 to 13.4 mF cm-2 and 82.1% to 87.4%, respectively, when 25 wt% of Mn3 O4 are replaced by SnO2 . The obtained CA values at a given T are higher than those of the transparent electrodes previously reported. An energy storage window fabricated using the mixed-NP electrodes exhibits the highest energy density among transparent supercapacitors previously reported. The improved energy density enables the window to operate various electronic devices for a considerable amount of time, demonstrating its applicability in constructing a reliable and space-efficient building-integrated power supply system.

Nanoscale chemical and structural investigation of solid solution polyelemental transition metal oxide nanoparticles

Although it has been shown that configurational entropy can improve the structural stability in transition metal oxides (TMOs), little is known about the oxidation state of transition metals under random mixing of alloys. Such information is essential in understanding the chemical reactivity and properties of TMOs stabilized by configurational entropy. Herein, utilizing electron energy loss spectroscopy (EELS) technique in an aberration-corrected scanning transmission electron microscope (STEM), we systematically studied the oxidation state of binary (Mn,Fe)3O4, ternary (Mn, Fe, Ni)3O4, and quinary (Mn, Fe, Ni, Cu, Zn)3O4 solid solution polyelemental transition metal oxides (SSP-TMOs) nanoparticles. Our findings show that the random mixing of multiple elements in the form of solid solution phase not only promotes the entropy stabilization but also results in stable oxidation state in transition metals spanning from binary to quinary transition metal oxide nanoparticles.

Environmental applications of flame synthesized CuO nanoparticles through removal of Congo Red dye

The Copper oxide (CuO) transition metal oxide nanoparticles (NPs) synthesized by simple, fast and commercially viable comfortably slight modified flame pyrolysis method. The CuO NPs were synthesized by direct burning of ethanolic copper chloride solution. The prepared CuO NPs were characterized for phase and crystallinity by X–ray Diffraction [XRD] and Fourier Transform Infrared [FT–IR] Spectroscopy, estimation of morphology was done by Field Emission Transmission Electron Microscopy [FE–SEM], average particles size of prepared CuO NPs estimated by High Resolution Transmission Electron Microscopy [HR - TEM] as well purity ensured by Energy Dispersive X–Ray Spectroscopy [EDS]. UV–vis absorption spectroscopy done for adsorption of aqueous Congo Red (CR) dye of flame synthesized CuO NPs. The structural, elemental and morphological characterization emphasised the synthesized CuO NPs are crystalline, pure and exhibited monoclinic structure with spherical morphology. The environmental applications of these flame synthesized CuO NPs were also evaluated by using adsorption of Congo Red (CR) dye and temperature effect on dye adsorption were also verified. HR-TEM revealed the average particles size of around 30 nm with fringe spacing of 2.788 Å and 2.377 Å, which corresponds to (110) and (200) planes of monoclinic phase of CuO NPs. The synthesized CuO NPs exhibited optical bandgap of 2.93 eV. The synthesized NPs showed high dye removal capacity up to 99.90% for the aqueous solution of Congo Red azo dye. These CuO NPs may emerge as the best catalytic adsorption alternative for the removal of industrial dyes, heavy metals and waste water treatment.