Solution Combustion Synthesis of Nanoscale Materials

Carbon dots as versatile nanomaterials in sensing and imaging: Efficiency and beyond

Carbon dots (CDs) have emerged as a versatile and promising carbon-based nanomaterial with exceptional optical properties, including tunable emission wavelengths, high quantum yield, and photostability. CDs are appropriate for various applications with many benefits, such as biocompatibility, low toxicity, and simplicity of surface modification. Thanks to their tunable optical properties and great sensitivity, CDs have been used in sensing as fluorescent probes for detecting pH, heavy metal ions, and other analytes. In addition, CDs have demonstrated potential as luminescence converters for white organic light-emitting diodes and light emitters in optoelectronic devices due to their superior optical qualities and exciton-independent emission. CDs have been used for drug administration and bioimaging in the biomedical field due to their biocompatibility, low cytotoxicity, and ease of functionalization. Additionally, due to their stability, efficient charge separation, and low recombination rate, CDs have shown interesting uses in energy systems, such as photocatalysis and energy conversion. This article highlights the growing possibilities and potential of CDs as adaptable nanomaterials in a variety of interdisciplinary areas related to sensing and imaging, at the same time addressing the major challenges involved in the current research and proposing scientific solutions to apply CDs in the development of a super smart society.

Combustion Growth of NiFe Layered Double Hydroxide for Efficient and Durable Oxygen Evolution Reaction

NiFe layered double hydroxide (LDH) with abundant heterostructures represents a state-of-the-art electrocatalyst for the alkaline oxygen evolution reaction (OER). Herein, NiFe LDH/Fe2O3 nanosheet arrays have been fabricated by facile combustion of corrosion-engineered NiFe foam (NFF). The in situ grown, self-supported electrocatalyst exhibited a low overpotential of 248 mV for the OER at 50 mA cm-2, a small Tafel slope of 31 mV dec-1, and excellent durability over 100 h under the industrial benchmarking 500 mA cm-2 current density. A balanced Ni and Fe composition under optimal corrosion and combustion contributed to the desirable electrochemical properties. Comprehensive ex-situ analyses and operando characterizations including Fourier-transformed alternating current voltammetry (FTACV) and in situ Raman demonstrate the beneficial role of modulated interfacial electron transfer, dynamic atomic structural transformation to NiOOH, and the high-valence active metal sites. This study provides a low-cost and easy-to-expand way to synthesize efficient and durable electrocatalysts.

The impact of urban rain on the changes of bare and artificially patinated bronze during 9-year exposure

Atmospheric pollutants in the air form acid rain which interacts with bronze surfaces exposed in urban outdoor environment. In this study, different types of patinas on bronze were investigated during and after 9 years of exposure to urban environment in moderately polluted continental city. Natural bronze patina and artificial brown sulphide, green chloride, and green-blue nitrate patinas were investigated. Visual assessment was carried out at defined periods. After 9 years of exposure, an electrochemical study was performed to investigate the electrochemical activity of the patinas in artificial urban rain. Additionally, the patinas were characterised using a variety of techniques, including metallographic examination, scanning electron microscopy/energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray diffraction analysis, X-ray-photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry to analyse the surface morphology, chemical composition, and stratigraphic features of the patinas. Evolution of the patinas was shown to be a result of both, the composition of the acid rain and the hydrophobicity of the patinated surfaces.

Smallest unit of maximal entropy as novel experimental criterion for parametric characterization of middle- and high-entropy materials

Materials with multiple principal elements (middle- and high-entropy materials), are used in emerging applications in various fields due to their unique properties, driven by configuration entropy. Improved understanding and experimental investigations of the impact of the entropy of mixing on the properties of these materials are of large practical interest. Here we show a simplified limited area calculation approach for assessing the entropy of mixing using a CoCuFeNi model nanoalloy. Based on our calculations we propose a new parametric entropy-based criterion, which defines critical scale parameter transition from the maximal entropy state to the entropy-depleted state of the system. The criterion could be used for generalized mechanistic assessment of the effect of the entropy of mixing on the characteristics of the materials with multiple principal elements and for the development and characterization of existing and new middle- and high-entropy materials with both simple single-, and more complex, multiple-sublattice structures.

Synthesis of pure and doped nano-calcium phosphates using different conventional methods for biomedical applications: a review

The applications of calcium phosphates (hydroxyapatite, tetracalcium phosphate, tricalcium phosphate (alpha and beta), fluorapatite, di-calcium phosphate anhydrous, and amorphous calcium-phosphate) are increasing day by day. Calcium hydroxyapatite, commonly known as hydroxyapatite (HAp), represents a mineral form of calcium apatite. Owing to its close molecular resemblance to the mineral constituents of bones, teeth, and hard tissues, HAp is often employed in the biomedical domain. In addition, it is extensively employed in various sectors such as the remediation of water, air, and soil pollution. The key advantage of HAp lies in its potential to accommodate a wide variety of anionic and cationic substitutions. Nevertheless, HAp and tricalcium phosphate (TCP) syntheses typically involve the use of chemical precursors containing calcium and phosphorus sources and employ diverse techniques, such as solid-state, wet, and thermal methods or a combination of these processes. Researchers are increasingly favoring natural sources such as bio-waste (eggshells, oyster shells, animal bones, fish scales, etc.) as viable options for synthesizing HAp. Interestingly, the synthesis route significantly influences the morphology, size, and crystalline phase of calcium phosphates. In this review paper, we highlight both dry and wet methods, which include six commonly used synthesis methods (i.e. solid-state, mechano-chemical, wet-chemical precipitation, hydrolysis, sol-gel, and hydrothermal methods) coupled with the variation in source materials and their influence in modifying the structural morphology from a bulky state to nanoscale to explore the applications of multifunctional calcium phosphates in different formats.

Interband electronic transitions and optical phonon modes in size-dependent multiferroic BiFeO3 nanoparticles

Bismuth ferrite (BiFeO3) multiferroic nanoparticles are synthesized using a low-temperature sol-gel auto-combustion technique. The phase purity is confirmed from X-ray diffraction (XRD) measurements and microstructural, electronic, and optical studies are correlated with the particle size of the bismuth ferrite nanostructured material. We demonstrated bandgap tunability from 2.22 to 1.93 eV with an average crystallite size from 42 to 24.42 nm following the inverse quantum confinement effect dominated by the lattice strain. The degenerate d-d electronic transitions 6A1g → 4T1g and 6A1g → 4T2g from iron dominate in these nanoparticles. The decrease in the energy band gap and the corresponding red shift in the d-d charge transfer transition energies with reduced average crystallite size are attributed to the increased lattice strain and reduced unit cell volume.

Investigation of Interface Characteristics and Physisorption Mechanism in Quantum Dots/TiO2 Composite for Efficient and Sustainable Photoinduced Interfacial Electron Transfer

Owing to their superior stability compared to those of conventional molecular dyes, as well as their high UV-visible absorption capacity, which can be tuned to cover the majority of the solar spectrum through size adjustment, quantum dot (QD)/TiO2 composites are being actively investigated as photosensitizing components for diverse solar energy conversion systems. However, the conversion efficiencies and durabilities of QD/TiO2-based solar cells and photocatalytic systems are still inferior to those of conventional systems that employ organic/inorganic components as photosensitizers. This is because of the poor adsorption of QDs onto the TiO2 surface, resulting in insufficient interfacial interactions between the two. The mechanism underlying QD adsorption on the TiO2 surface and its relationship to the photosensitization process remain unclear. In this study, we established that the surface characteristics of the TiO2 semiconductor and the QDs (i.e., surface defects of the metal oxide and the surface structure of the QD core) directly affect the QD adsorption capacity by TiO2 and the interfacial interactions between the QDs and TiO2, which relates to the photosensitization process from the photoexcited QDs to TiO2 (QD* → TiO2). The interfacial interaction between the QDs and TiO2 is maximized when the shape/thickness-modulated triangular QDs are composited with defect-rich anatase TiO2. Comprehensive investigations through photodynamic analyses and surface evaluation using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and photocatalysis experiments collectively validate that tuning the surface properties of QDs and modulating the TiO2 defect concentration can synergistically amplify the interfacial interaction between the QDs and TiO2. This augmentation markedly improved the efficiency of photoinduced electron transfer from the photoexcited QDs to TiO2, resulting in significantly increased photocatalytic activity of the QD/TiO2 composite. This study provides the first in-depth characterization of the physical adhesion of QDs dispersed on a heterogeneous metal-oxide surface. Furthermore, the prepared QD/TiO2 composite exhibits exceptional adsorption stability, resisting QD detachment from the TiO2 surface over a wide pH range (pH = 2-12) in aqueous media as well as in nonaqueous solvents during two months of immersion. These findings can aid the development of practical QD-sensitized solar energy conversion systems that require the long-term stability of the photosensitizing unit.

Mechanistic Approach on the Pulmonary Oxido-Inflammatory Stress Induced by Cobalt Ferrite Nanoparticles in Rats

Cobalt ferrite nanoparticles (CFN) are employed in data storage, imaging, medication administration, and catalysis due to their superparamagnetic characteristics. The widespread use of CFN led to significantly increased exposure to people and the environment to these nanoparticles. Until now, there is not any published paper describing the adverse effect of repeated oral intake of this nanoformulation on rats' lungs. So, the current research aims to elucidate the pulmonary toxicity prompted by different concentrations of CFN in rats as well as to explore the mechanistic way of such toxicity. We used 28 rats that were divided equally into 4 groups. The control group received normal saline, and the experimental groups received CFN at dosage levels 0.05, 0.5, and 5 mg/kg bwt. Our findings revealed that CFN enhanced dose-dependent oxidative stress manifested by raising in the MDA levels and declining in the GSH content. The histopathological examination revealed interstitial pulmonary inflammation along with bronchial and alveolar damage in both 0.5 and 5 mg CFN given groups. All these lesions were confirmed by the immunohistochemical staining that demonstrated strong iNOS and Cox-2 protein expression. There was also a significant upregulation of TNFα, Cox-2, and IL-1β genes with downregulation of IL-10 and TGF-β genes. Additionally, the group receiving 0.05 mg CFN did not exhibit any considerable toxicity in all measurable parameters. We concluded that the daily oral intake of either 0.5 or 5 mg CFN, but not 0.05 mg, could induce pulmonary toxicity via NPs and/or its leached components (cobalt and iron)-mediated oxido-inflammatory stress. Our findings may help to clarify the mechanisms of pulmonary toxicity generated by these nanoparticles through outlining the standards for risk assessment in rats as a human model.

Spectroscopic studies of metastable tetragonal ZrO2 nanocrystals

This study delves into an examination of the structural and luminescent properties of zirconium dioxide (ZrO2) synthesized via the solid-state combustion method. Nitrates are harnessed as the oxidizing agent, while glycine serves as the fuel. Two distinct compositions are explored: a stoichiometric 1:1 ratio and a fuel-enriched 1:2 ratio. The structural analysis, employing X-ray diffraction and Raman spectroscopy, predominantly manifests a tetragonal structural phase in both samples; however, a minor monoclinic phase has also been observed in the former sample. The band gap was found to be 4.50 eV and 4.28 eV for ZrO2 synthesized in stoichiometric ratio and a fuel-enriched ratio respectively. The samples also show defects assisted photoluminescence in both the samples. The thermoluminescence of samples were investigated after irradiating the samples with UV and gamma rays for different doses. The TL curves manifest a shift towards lower temperatures at higher doses. . Significantly, the sample prepared with a 1:1 nitrate-fuel ratio exhibits a more pronounced overall TL intensity. In conclusion, our findings imply that the formation of the tetragonal phase may be influenced by strain energy, rather than being solely ascribed to size effects and oxygen vacancies within the lattice.

Electro-Oxidation Reaction of Methanol over La2-xSrxNi1-y(Mn/Fe/Co)yO4+δ Ruddlesden-Popper Oxides

Solution combustion-synthesized Ruddlesden-Popper oxides La1.4Sr0.6Ni0.9(Mn/Fe/Co)0.1O4+δ were explored for the methanol electro-oxidation reaction. With optimal doping of Sr2+ in the A site and Co2+ in the B site, Ni3+ with t2g6 d x 2 - y 2 1 configuration in La1.4Sr0.6Ni0.9Co0.1O4+δ exhibited a tetragonal distortion with compression in axial bonds and elongation in equatorial bonds. This structural modification fostered an augmented overlap of d z 2 orbitals with axial O 2p orbitals, leading to a heightened density of states at the Fermi level. Consequently, this facilitated not only elevated electrical conductivity but also a noteworthy reduction in the charge transfer resistance. These effects collectively contributed to the exceptional methanol oxidation activity of La1.4Sr0.6Ni0.9Co0.1O4+δ, as evidenced by an impressive current density of 21.4 mA cm-2 and retention of 95% of initial current density even after 10 h of prolonged reaction. The presence of Ni3+ further played a pivotal role in the creation of NiOOH, a crucial intermediate species, facilitated by the presence of surface oxygen vacancies. These factors synergistically enabled efficient methanol oxidation. In summary, our present study not only yields substantial insights but also paves the way for a novel avenue to fine-tune the activity of Ruddlesden-Popper oxides for the successful electro-oxidation of methanol.

Heteroatom-modulated NiCo2O4 apparent energy activation of PMS for tetracycline removal: Mechanism and toxicity analysis

Heteroatom doping to reconfigure the electronic structure of heterogeneous catalysts is expected to lead to the development of advanced oxidation water purification materials with superior performance and greater stability. Herein, a series of catalysts with different elemental doping was developed by a simple and environmentally friendly one-step self-propagating combustion method to remove Tetracycline (TC). After S-doping, the normalized kinetic constant of TC was significantly increased from 30.49 to 159.41 min-1M-1 within 30 min, which is even higher than most recent heterogeneous catalysts. The prepared S-doped NiCo2O4 (NCO-S) exhibits an extremely promising catalytic performance for oxidation (92.8 %) and mineralization (65.9 %) of TC in a wide pH range (3-11). The resistance to interference is excellent for inorganic ions and even in real water samples. Quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analyses demonstrated that the non-radical oxidation pathway, including electron transfer and 1O2, dominated the degradation process after S doping. It is speculated that possible intermediates and toxicological studies are discussed, finding that the overall degradation process is moving towards low toxicity to reveal prospects for large-scale applications. This work not only provides a way to remove TC, but may also inspire the design of more efficient and stable materials for water treatment and other applications.

Influence of Polycyclic Aromatic Compounds and Oxidation States of Soot Organics on the Metabolome of Human-Lung Cells (A549): Implications for Vehicle Fuel Selection

Decades of research have established the toxicity of soot particles resulting from incomplete combustion. However, the unique chemical compounds responsible for adverse health effects have remained uncertain. This study utilized mass spectrometry to analyze the chemical composition of extracted soot organics at three oxidation states, aiming to establish quantitative relationships between potentially toxic chemicals and their impact on human alveolar basal epithelial cells (A549) through metabolomics-based evaluations. Targeted analysis using MS/MS indicated that particles with a medium oxidation state contained the highest total abundance of compounds, particularly oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) composed of fused benzene rings and unsaturated carbonyls, which may cause oxidative stress, characterized by the upregulation of three specific metabolites. Further investigation focused on three specific OPAH standards: 1,4-naphthoquinone, 9-fluorenone, and anthranone. Pathway analysis indicated that exposure to these compounds affected transcriptional functions, the tricarboxylic acid cycle, cell proliferation, and the oxidative stress response. Biodiesel combustion emissions had higher concentrations of PAHs, OPAHs, and nitrogen-containing PAHs (NPAHs) compared with other fuels. Quinones and 9,10-anthraquinone were identified as the dominant compounds within the OPAH category. This knowledge enhances our understanding of the compounds contributing to adverse health effects observed in epidemiological studies and highlights the role of aerosol composition in toxicity.

Controlling Metal-Oxide Reducibility for Efficient C-H Bond Activation in Hydrocarbons

Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx -Al2 O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V-O-Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2 -ZrO2 -Al2 O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non-oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution.

Persistent luminescent nanophosphors for applications in cancer theranostics, biomedical, imaging and security

The extraordinary and unique properties of persistent luminescent (PerLum) nanostructures like storage of charge carriers, extended afterglow, and some other fascinating characteristics like no need for in-situ excitation, and rechargeable luminescence make such materials a primary candidate in the fields of bio-imaging and therapeutics. Apart from this, due to their extraordinary properties they have also found their place in the fields of anti-counterfeiting, latent fingerprinting (LPF), luminescent markings, photocatalysis, solid-state lighting devices, glow-in-dark toys, etc. Over the past few years, persistent luminescent nanoparticles (PLNPs) have been extensively used for targeted drug delivery, bio-imaging guided photodynamic and photo-thermal therapy, biosensing for cancer detection and subsequent treatment, latent fingerprinting, and anti-counterfeiting owing to their enhanced charge storage ability, in-vitro excitation, increased duration of time between excitation and emission, low tissue absorption, high signal-to-noise ratio, etc. In this review, we have focused on most of the key aspects related to PLNPs, including the different mechanisms leading to such phenomena, key fabrication techniques, properties of hosts and different activators, emission, and excitation characteristics, and important properties of trap states. This review article focuses on recent advances in cancer theranostics with the help of PLNPs. Recent advances in using PLNPs for anti-counterfeiting and latent fingerprinting are also discussed in this review.

Cerium oxide nanoparticles: Synthesis methods and applications in wound healing

Wound care and treatment can be critical from a clinical standpoint. While different strategies for the management and treatment of skin wounds have been developed, the limitations inherent in the current approaches necessitate the development of more effective alternative strategies. Advances in tissue engineering have resulted in the development of novel promising approaches for accelerating wound healing. The use of various biomaterials capable of accelerating the regeneration of damaged tissue is critical in tissue engineering. In this regard, cerium oxide nanoparticles (CeO2 NPs) have recently received much attention because of their excellent biological properties, such as antibacterial, anti-inflammatory, antioxidant, and angiogenic features. The incorporation of CeO2 NPs into various polymer-based scaffolds developed for wound healing applications has led to accelerated wound healing due to the presence of CeO2 NPs. This paper discusses the structure and functions of the skin, the wound healing process, different methods for the synthesis of CeO2 NPs, the biological properties of CeO2 NPs, the role of CeO2 NPs in wound healing, the use of scaffolds containing CeO2 NPs for wound healing applications, and the potential toxicity of CeO2 NPs.

Solution Combustion Synthesis of Ni-Based Nanocatalyst Using Ethylenediaminetetraacetic Acid and Nickel-Carbon Nanotube Growth Behavior

We studied the influence of the ethylenediaminetetraacetic acid (EDTA) content used as combustion fuel when fabricating nickel oxide (NiO) nanocatalysts via solution combustion synthesis, as well as the growth behavior of carbon nanotubes (CNTs) using this catalyst. Nickel nitrate hexahydrate (Ni(NO3)2∙6H2O) was used as the metal precursor (an oxidizer), and the catalysts were synthesized by adjusting the molar ratio of fuel (EDTA) to oxidizer in the range of 1:0.25 to 2.0. The results of the crystal structure analysis showed that as the EDTA content increased beyond the chemical stoichiometric balance with Ni(NO3)2∙6H2O (F/O = 0.25), the proportion of Ni metal within the catalyst particles decreased, and only single-phase NiO was observed. Among the synthesized catalysts, the smallest crystallite size was observed with a 1:1 ratio of Ni ions to EDTA. However, an increase in the amount of EDTA resulted in excessive fuel supply, leading to an increase in crystallite size. Microstructure analysis revealed porous NiO agglomerates due to the use of EDTA, and differences in particle growth based on the fuel ratio were observed. We analyzed the growth behavior of CNTs grown using NiO nanocatalysts through catalytic chemical vapor deposition (CCVD). As the F/O ratio increased, it was observed that the catalyst particles grew excessively beyond hundreds of nanometers, preventing further CNT growth and leading to a rapid termination of CNT growth. Raman spectroscopy was used to analyze the structural characteristics of CNTs, and it was found that the ID/IG ratio indicated the highest CNT crystallinity near an F/O ratio of 1:1.

Solution Combustion Synthesis of High-Performance Nano-LiFePO4/C Cathode Material from Cost-Effective Mixed Fuels

Solution combustion synthesis (SCS) is considered as an efficient and energy-saving method for preparing LiFePO4/C composite material with the nanostructure (Nano-LiFePO4/C). In this study, Nano-LiFePO4/C cathode material was prepared using SCS using a cost-effective combination of urea and sorbitol as mixed fuels. The effect of mixed fuels on combustion behavior and microstructure as well as on electrochemical performance was studied using XRD, BET, SEM, TEM, and electrochemical characterization methods. Multiple characterization results indicated that the maximum temperature (Tm) and particle size were influenced by the usage of urea and sorbitol. The sample derived under optimum conditions exhibits a mesoporous nanostructure with a large surface specific area and attractive electrochemical performance with a discharge capacity of 153.5 mAh/g at 0.1 C, which shows strong potential for commercial applications in the future.

High-entropy oxides: an emerging anode material for lithium-ion batteries

High entropy oxides (HEOs) have gained significant attention in multiple research fields, particularly in reversible energy storage. HEOs with rock-salt and spinel structures have shown excellent reversible capacity and longer cycle spans compared to traditional conversion-type anodes. However, research on HEOs and their electrochemical performance remains at an early stage. In this highlight, we review recent progress on HEO materials in the field of lithium-ion batteries (LIBs). Firstly, we introduce the synthesis methods of HEOs and some factors that affect the morphology and electrochemical properties of the synthesized materials. We then elaborate on the structural evolution of HEOs with rock-salt and spinel structures in lithium energy storage and summarize the relationship between morphology, pseudocapacitance effect, oxygen vacancy, and electrochemical performance. In the end, we give the challenges of HEO anodes for LIBs and present our opinions on how to guide the further development of HEOs for advanced anodes.

Synthesis and feasibility studies of doping U at Ti site of Y2Ti2O7 as a radioactive waste immobilization matrix

In pursuit of clean and green nuclear energy one of the major challenges is to effectively immobilize the nuclear waste. In this context A2B2O7 type pyrochlore owing to its structural flexibility, ability to accommodate ions at both A/B-sites and high radiation tolerance has demonstrated excellent capability to store highly radioactive actinide ions. To fill the major gap area of actinide doping at the B site we have taken up the challenge of doping uranium ions at the Ti site of Y2Ti2O7 type pyrochlore. An yttria titanate (Y2Ti2-xUxO7; x = 0.05, 0.075, 0.1, 0.2, and 0.3) based matrix with uranium doped at the Ti site was synthesized using a simple gel combustion route under an air atmosphere. Rietveld refined X-ray diffraction (XRD) demonstrated that Y2Ti2O7 can accommodate U up to 5 mol% in the Ti site without any phase separation, which was further confirmed using Raman spectroscopy. Y2Ti2O7 based matrices are found to be radiation stable up to 1000 kGy and at the same time they are moderately thermally stable and on a par with the values reported for pyrochlores. Uranium in Y2Ti2O7 stabilizes in +6 oxidation state in the form of uranyl ion distributed near and far off from titanium vacancies with distinct excited state lifetime. This work could provide a smart and strategic way for selecting a suitable advanced ceramic matrix for immobilization of high level waste with additional and important information on solubility limit, actinide speciation, radiation/thermal stability, actinide concentration, etc.

Structural, morphological, and optical characteristics of Gd2 Si2 O7 :Dy3+ nanophosphors for WLEDs

Yellowish-white light-emitting Gd2-x Si2 O7 :xDy3+ (x = 1-5 mol%) nanophosphors were prepared using a solution combustion synthesis method. Fluorescence spectrophotometry and X-ray diffraction measurements were performed to scrutinize the optical performances and phase recognition of the designated nanophosphors. The outcomes specified that the prepared phosphors were crystallized into a triclinic phase with a P-1 space group. As the concentration of Dy3+ ions was increased, the unit-cell volume decrease proportionally due to the replacement of large-sized Gd3+ by small-sized Dy3+ ions. Under ultraviolet excitation at 349 nm, emission spectra consisted of two pronounced emission lines at ~482 nm (blue line), ~578 nm (yellow line), and a relatively weaker emission at ~670 nm (red line) due to 4 F9/2 →6 H15/2 , 4 F9/2 →6 H13/2 , and 4 F9/2 →6 H11/2 intraconfigurational transitions of Dy3+ ions, respectively. The evidence about the site symmetry around Dy3+ ions was examined by considering the ratio of yellow-to-blue emission intensity. The observed critical distance (Rc ) value was ~20.56 Å (≫5 Å), which signified that energy transfer primarily occurred due to multipolar interaction. The obtained coordinates were close to the white region of the Commission Internationale de l'Éclairage chromaticity diagram, which marked a significant milestone in the development of white light-emitting diodes.

Optically amended biosynthesized crystalline copper-doped ZnO for enhanced antibacterial activity

The emergence and re-emergence of antibiotic-resistant bacteria is a potential threat to treating infectious diseases. This study employed a nanometer-scale green synthesis using an extract of Solanum incanum leaves to obtain nanoparticles (NPs) and nanocomposites (NCs) possessing antibacterial properties. The FESEM-EDS elemental mapping analysis proved the novelty of the green synthesis approach in synthesizing a copper-doped ZnO NCs with good dopant distribution. The crystallinity and ZnO bandgap were adjusted by extrinsic copper doping in the ZnO lattice. The optical property adjustments from 3.04 to 2.97 eV for indirect Kubelka-Munk functions were confirmed from DRS-UV-vis analysis. The dopant inclusion in the host lattice was also confirmed by the angle shift on the XRD pattern analysis relative to single ZnO. In addition to doping, the XRD pattern analysis also showed the development of CuO crystals. The lattice fringe values from HRTEM analysis confirmed the existence of both CuO and ZnO crystals with local heterojunctions. Doping and heterojunctions have crucial values in charge transfer and visible light harvesting behaviour, as proved by the PL analysis. The synergistic effects of the doped NCs showed greater antibacterial activity against both Gram-positive and Gram-negative bacteria as a result of more ROS generation through the bacteria-cell-catalyst interaction and release of metal ions. The antioxidant potential of the doped NCs was found to be higher than that of single NPs, using the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging assay and is expected to impart protective effects to the host cells by scavenging destructive free radicals. Thus, the overall analysis leads to the conclusion that the potentiality of synthesized materials has a future outlook for biological applications, especially in the development of antimicrobials to combat antibiotic-resistant bacteria and microbes.

Beneficial effect of cerium excess on in situ grown Sr0.86Ce0.14FeO3-CeO2 thermocatalysts for the degradation of bisphenol A

Ce-doped SrFeO₃ perovskite-type compounds are known as good thermocatalysts for the abatement of wastewater contaminants of emerging concern. In this work, Sr_0.86Ce_0.14FeO₃-CeO₂ perovskite-oxide systems with increasing amounts of cerium excess (0, 5, 10 and 15 mol% Ce), with respect to its maximum solubility in the perovskite, were prepared in one-pot by solution combustion synthesis and the effects of cerium excess on the chemical physical properties and thermocatalytic activity in the bisphenol A degradation were evaluated. The powders were characterized by powder X-ray diffraction combined with Rietveld refinement, X-ray photoelectron spectroscopy, thermal gravimetry, temperature programmed reduction, nitrogen adsorption, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques. Results highlight that the perovskite structural, redox, surface, and morphological properties are affected by the in situ co-growth of the main perovskite phase and ceria and that a larger cerium excess has a beneficial effect on the thermocatalytic performance of the perovskite oxide-ceria biphasic system, although ceria is not active as a thermocatalyst itself. Perovskite properties and performance are enhanced by the tetragonal distortion induced by the introduction of cerium excess in the synthesis. It is supposed that a larger oxygen mobility and an easier reducibility are among the most relevant features that contribute to superior thermocatalytic properties of these perovskite oxide-based systems. These results also suggest new perspectives in the nanocomposite preparation and their catalytic applications.

Nanoparticle Synthesis and Their Integration into Polymer-Based Fibers for Biomedical Applications

The potential of nanoparticles as effective drug delivery systems combined with the versatility of fibers has led to the development of new and improved strategies to help in the diagnosis and treatment of diseases. Nanoparticles have extraordinary characteristics that are helpful in several applications, including wound dressings, microbial balance approaches, tissue regeneration, and cancer treatment. Owing to their large surface area, tailor-ability, and persistent diameter, fibers are also used for wound dressings, tissue engineering, controlled drug delivery, and protective clothing. The combination of nanoparticles with fibers has the power to generate delivery systems that have enhanced performance over the individual architectures. This review aims at illustrating the main possibilities and trends of fibers functionalized with nanoparticles, focusing on inorganic and organic nanoparticles and polymer-based fibers. Emphasis on the recent progress in the fabrication procedures of several types of nanoparticles and in the description of the most used polymers to produce fibers has been undertaken, along with the bioactivity of such alliances in several biomedical applications. To finish, future perspectives of nanoparticles incorporated within polymer-based fibers for clinical use are presented and discussed, thus showcasing relevant paths to follow for enhanced success in the field.

Facile synthesis of spongy NiCo2O4 powders for lithium-ion storage

Spongy NiCo₂O₄ powders were prepared by solution combustion synthesis (SCS) method for lithium ions storage. The effects of combustion parameters including fuel type (L-lysine, glycine, and urea) and fuel amount on the lithium storage performance of NiCo₂O₄ powders were analyzed by various characterization techniques. Single-phase NiCo₂O₄ powders with extremely porous microstructure showed a strong drop of initial specific capacity up to 350 mAhg^-1 which was recovered up to 666 mAhg^-1 following 100 charge/discharge cycles. However, the NiCo₂O₄ powders prepared by the urea and L-lysine fuels with the compacted microstructure showed the capacity loss without any recovery. The spongy NiCo₂O₄ powders showed an acceptable capability rate performance (404 mAhg^-1 @ 400 mAg^-1).

Combustion Synthesis of Magnetic Nanomaterials for Biomedical Applications

Combustion synthesis is a green, energy-saving approach that permits an easy scale-up and continuous technologies. This process allows for synthesizing various nanoscale materials, including oxides, nitrides, sulfides, metals, and alloys. In this work, we critically review the reported results on the combustion synthesis of magnetic nanoparticles, focusing on their properties related to different bio-applications. We also analyze challenges and suggest specific directions of research, which lead to the improvement of the properties and stability of fabricated materials.

Introducing Materials Science: Experimenting with Magnetic Nanomaterials in the Undergraduate Chemistry Laboratory

Materials science research has expanded significantly in recent years; a multidisciplinary field, home to an ever-growing number of chemists. However, our general chemistry degree courses have not changed to reflect the rise in interest in this topic. In this paper, we propose a laboratory experiment for the undergraduate chemistry practical course, which may serve as a hands-on introduction to this field. The experiment involves the synthesis and characterization of magnetic materials via commonly employed techniques in materials science. Students begin by producing three metal ferrite spinels using a sol-gel combustion synthesis. They must then characterize the differing magnetic properties across their three samples using a magnetic susceptibility balance. In the second part of the experiment, students must create a ferrofluid via coprecipitation, from which they may observe the phenomenon of "spiking" in response to an external magnet. Additional data such as X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images corresponding to these materials are also provided, and students are tasked with the interpretation of these data in their writeup report. Upon completion, students should gain a new-found understanding of materials science and its fundamental overlap with chemistry.

Review on magnetic spinel ferrite (MFe2O4) nanoparticles: From synthesis to application

Magnetic spinel ferrite materials offer various applications in biomedical, water treatment, and industrial electronic devices, which has sparked a lot of attention. This review focuses on the synthesis, characterization, and applications of spinel ferrites in a variety of fields, particularly spinel ferrites with doping. Spinel ferrites nanoparticles doped with the elements have remarkable electrical and magnetic properties, allowing them to be used in a wide range of applications such as magnetic fields, microwave absorbers, and biomedicine. Furthermore, the physical properties of spinel ferrites can be modified by substituting metallic atoms, resulting in improved performance. The most recent and noteworthy applications of magnetic ferrite nanoparticles are reviewed and discussed in this review. This review goes over the synthesis, doping and applications of different types of metal ferrite nanoparticles, as well as views on how to choose the appropriate magnetic ferrites based on the intended application.

Investigation into the crystal structure-dielectric property correlation in barium titanate nanocrystals of different sizes

For high capacitance multilayer ceramic capacitors, high dielectric constant and lead-free ceramic nanoparticles are highly desired. However, as the particle size decreases to a few tens of nanometers, their dielectric constant significantly decreases, and the underlying mechanism has yet to be fully elucidated. Herein, we report a systematic investigation into the crystal structure-dielectric property relationship of combustion-made BaTiO₃ (BTO) nanocrystals. When the nanocrystal size was 100 nm and below, a metastable paraelectric cubic phase was found in the as-received BTO (denoted as arBTO) nanocrystals based on an X-ray diffraction (XRD) study. A stable ferroelectric tetragonal phase was present when the nanocrystal size was above 200 nm. Notably, the cubic arBTO (particle size ≤100 nm) exhibited tetragonal fluctuations as revealed by Raman spectroscopy, whereas the tetragonal arBTO (particle size ≥200 nm) contained ∼10% cubic fraction according to the Rietveld fitting of the XRD profiles. Thermal annealing of the multi-grain tetragonal arBTO at 950 °C yielded single crystals of annealed BTO (denoted as anBTO), whose dielectric constants were higher than those of arBTO. However, the single crystalline anBTO prevented the formation of 90° domains; therefore, they exhibited a low dielectric constant of ∼300. Although X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy could not identify the exact structural defects, our study revealed that surface and bulk defects formed during synthesis affect the final crystal structures and thus the dielectric properties of BTO nanocrystals with different sizes. The understanding obtained from this study will help us design high dielectric constant perovskite nanocrystals for next-generation multilayer ceramic capacitor applications.

Life Cycle Impact Assessment of Solution Combustion Synthesis of Titanium Dioxide Nanoparticles and Its Comparison with More Conventional Strategies

This paper represents the first attempt to quantitatively and reliably assess the environmental sustainability of solution combustion synthesis (SCS) with respect to other soft chemistry strategies, which are more conventionally employed in the preparation of engineered oxide nanomaterials, namely hydrolytic and non-hydrolytic sol-gel syntheses (i. e., HSGS and NHSGS). Indeed, although SCS is well known to rely on significant reduction in the energy as well as time required for the obtainment of the desired nanocrystals, its quantitative environmental assessment and a detailed comparison with other existing synthetic pathways represents an absolute novelty of high scientific desirability in order to pursue a more sustainable development in the inorganic chemistry as well as materials science research fields. TiO₂ nanoparticles were selected as the material of choice, for the production of which three slightly modified literature procedures were experimentally reproduced and environmentally evaluated by the application of the comprehensive life cycle assessment (LCA) methodology. Particularly, SCS was compared from an environmental perspective with sol-gel approaches performed both in water and in benzyl alcohol. The results of the present study were also framed among those recently obtained in a systematic study assessing seven further chemical, physical, and biological routes for the synthesis of TiO₂ nanoparticles, comprising also flame spray pyrolysis (typically used in industrial productions), highlighting and quantifying the excellent environmental performances of SCS.

Effects of interactions between natural organic matter and aquatic organism degradation products on the transformation and dissolution of cobalt and nickel-based nanoparticles in synthetic freshwater

Expanding applications and production of engineered nanoparticles lead to an increased risk for their environmental dispersion. Systematic knowledge of surface transformation and dissolution of nanoparticles is essential for risk assessment and regulation establishment. Such aspects of Co- and Ni-based nanoparticles including metals, oxides, and solution combustion synthesized metal nanoparticles (metal cores with carbon shells) were investigated upon environmental interaction with organic matter, simulated by natural organic matter (NOM) and degradation products from zooplankton and algae (eco-corona biomolecules, EC) in freshwater (FW). The presence of NOM and EC in FW results in negative surface charges of the nanoparticles reduces the extent of nanoparticles agglomeration, and increases concentration, mainly due to the surface adsorption of carboxylate groups of the organic matter. The dissolution of the Co-based nanoparticles was for all conditions (FW, FW with NOM or EC) higher than the Ni-based, except for Co₃O₄ being nearly non-soluble. The surface transformation and dissolution of nanoparticles are highly exposure and time-dependent, and surface- and environment specific. Therefore, no general correlation was observed between dissolution and, particle types, surface conditions, or EC/NOM adsorption. This underlines the importance of thorough investigations of nanoparticles adsorption/desorption, degradation, and exposure scenarios for developing regulatory relevant protocols and guidelines.

Gadolinium-based Sm3+ activated GdSr2AlO5 nanophosphor: synthesis, crystallographic and opto-electronic analysis for warm wLEDs

A material's luminosity characteristics, which in turn dictate its applicability, are critically influenced by its structure. Therefore, it is essential for design and fabrication of optical nanocrystalline materials to comprehend the relationship between structural and luminescence properties. The gel-combustion approach was used to produce a sequence of orange-red light emanating GdSr₂AlO₅:Sm³⁺ (GSA:Sm³⁺) nanophosphors which are used for warm white-light-emitting diodes (w-LEDs). Comprehensive investigation of the structural and optical characteristics of GdSr₂AlO₅:Sm³⁺ nanophosphors has been done in a detailed manner. The synthesized powdered nanophosphors are crystallized in a tetragonal phase with I4/mcm (140) space group, affirmed through Rietveld refining method. The nano size with an aggregated, spherical form of the particles in the powdered nanocrystalline material was revealed by TEM analysis. These orange-red emitting phosphors Gd_1-x Sr₂AlO₅:xSm³⁺ (x = 1-7 mol%) were shown to possess photoluminosity (PL) properties that demonstrated the presence of most intense emission peaks at 603 nm that were caused by ⁴G_5/2 → ⁶H_7/2 transitions of the Sm³⁺ ion under 273 nm excitation. Considering its long decay lifespan and PL emission, it can be concluded that the GdSr₂AlO₅:Sm³⁺ phosphor is a potential single element for the fabrication of warm white light-emitting devices.

Mesostructured γ-Al2O3-Based Bifunctional Catalysts for Direct Synthesis of Dimethyl Ether from CO2

In this work, we propose two bifunctional nanocomposite catalysts based on acidic mesostructured γ-Al2O3 and a Cu/ZnO/ZrO2 redox phase. γ-Al2O3 was synthesized by an Evaporation-Induced Self-Assembly (EISA) method using two different templating agents (block copolymers Pluronic P123 and F127) and subsequently functionalized with the redox phase using an impregnation method modified with a self-combustion reaction. These nanocomposite catalysts and their corresponding mesostructured supports were characterized in terms of structural, textural, and morphological features as well as their acidic properties. The bifunctional catalysts were tested for the CO2-to-DME process, and their performances were compared with a physical mixture consisting of the most promising support as a dehydration catalyst together with the most common Cu-based commercial redox catalyst (CZA). The results highlight that the most appropriate Pluronic for the synthesis of γ-Al2O3 is P123; the use of this templating agent allows us to obtain a mesostructure with a smaller pore size and a higher number of acid sites. Furthermore, the corresponding composite catalyst shows a better dispersion of the redox phase and, consequently, a higher CO2 conversion. However, the incorporation of the redox phase into the porous structure of the acidic support (chemical mixing), favoring an intimate contact between the two phases, has detrimental effects on the dehydration performances due to the coverage of the acid sites with the redox nanophase. On the other hand, the strategy involving the physical mixing of the two phases, distinctly preserving the two catalytic functions, assures better performances.

Structural studies and selected physical investigations of LiCoO2 obtained by combustion synthesis

Nanocrystalline powders of LiCoO₂ were synthesized using a modified solution combustion method, and the effects of the annealing temperature (450-900 °C) on structure and composition were investigated using various methods, including XRD, SEM, EPR, and electrical studies. It was found that, as the process temperature increases, the value of the specific surface area decreases, and, hence, the size of the crystallites increases. XRD analysis showed that phase-pure LiCoO₂ material was maintained without additional phases. EPR studies revealed the presence of two Ni³⁺ complexes resulting from Ni impurities. The electrical properties of the studied LiCoO₂ samples were investigated by using impedance spectroscopy. Comparison of the effect of annealing temperature on electrical conductivity shows a very interesting behavior. As the annealing temperature increases, the DC conductivity value increases, reaching a maximum at a temperature of 500 °C. However, further increase in the annealing temperature causes a steady decrease in the DC conductivity.

Two-body wear resistance and fatigue survival of new Y-TZP and ATZ ceramics made with a new slip-casting method

BACKGROUND

Dental zirconium oxide restorations are milled from pre-sintered blocks or disks which are produced either with high isostatic pressure (HIP) or, simpler, a slurry technique. The objective was to perform a fatigue test and an in vitro wear simulation of two ceramics, yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramic and a hybrid zirconium oxide-aluminum oxide ceramic, (ATZ) both produced either the classical way using high isostatic pressure (HIP, control) or with a slurry technique.

MATERIALS AND METHODS

Ten discs/group were subjected to a cyclic biaxial fatigue test using a staircase approach under water at 37 °C in a dynamic universal testing machine. The 2-body wear test was performed on eight lapped 12 mm thick cylindrical samples subjected to spherical (ø 6 mm) leucite ceramic antagonists in a CS-4 chewing simulator at 49 N force and 0.7 mm lateral movement for 600 k cycles and 4167 thermal cycles (5-55 °C). Volumetric wear was calculated based on laser-scanned surfaces. Selected samples of both tests were viewed in SEM.

RESULTS

All the ceramic specimens produced using the HIP method survived up to 1.2 M cycles with the maximum load of the equipment (1000 N) loading the specimens up to 1527 MPa. The fatigue limit stress at 1.2 M cycles for the Slurry ATZ samples was 946 MPa. For the Slurry Y-TZP samples the fatigue limit stress at 1.2 M cycles was 658 MPa. At 600 k cycles, all zirconium oxide ceramics showed no measurable wear and had a highly polished appearance. The leucite ceramic antagonists wear developed in a linear way. There was no difference between the materials produced with the slurry and the HIP process. ATZ ceramic produced significantly more wear than 3Y- TZP ceramic.

CONCLUSIONS

The HIP method provided higher fatigue strength than the Slurry manufacturing method. All HIP ceramics surpassed the limit threshold (1527 MPa) of the testing machine. The tested ceramics did not show any measurable wear but had worn the leucite reinforced glass ceramic antagonists for a considerable amount.

Facile Preparation of Macro-Microporous Thorium Oxide via a Colloidal Sol-Gel Route toward Safe MOX Fuel Fabrication

The identification of new colloidal sol-gel routes for the preparation of actinide oxides, which have a homogeneous and accessible porosity that can easily be impregnated by any concentrated actinide solution, opens new perspectives for the preparation of homogeneous nuclear fuel for minor actinide transmutation. This homogeneity allows us to avoid "hot spot" formation due to the local accumulation of more fissile elements. Here, we report the preparation of macro-microporous ThO₂ materials by a colloidal sol-gel route. Using a thorium salt with 6-aminocaproic acid as a complexing agent at a controlled pH, we were able to pilot the condensation of thorium hydroxo species forming colloids of tuned nanometric size and thus the sol stability. After a freeze-drying process to concentrate colloids and a thermal treatment allowing complexing agent removal and macroporosity formation by a brutal gas release during combustion, a loose packing of ThO₂ nanoparticles with an ordered distribution of interparticular porosity and a fraction of nanometric crystallites, whose size depends on the initial colloidal size, were obtained. The sols, pastes, and final materials were characterized by small- and wide-angle X-ray scattering to determine the colloidal size and the final structure of the materials, which was also confirmed by transmission electron microscopy. The most promising material was finally successfully impregnated by a simulating minor actinide solution and thermally treated to prepare a mixed actinide oxide material. This safe technology, relying on the colloidal sol-gel process and the formulation of complex fluids forming tunable precursors, opens new perspectives for the reuse of nuclear waste solutions as new fuel.

CeFeO3-CeO2-Fe2O3 Systems: Synthesis by Solution Combustion Method and Catalytic Performance in CO2 Hydrogenation

Rare-earth orthoferrites have found wide application in thermocatalytic reduction-oxidation processes. Much less attention has been paid, however, to the production of CeFeO₃, as well as to the study of its physicochemical and catalytic properties, in particular, in the promising process of CO₂ utilization by hydrogenation to CO and hydrocarbons. This study presents the results of a study on the synthesis of CeFeO₃ by solution combustion synthesis (SCS) using various fuels, fuel-to-oxidizer ratios, and additives. The SCS products were characterized by XRD, FTIR, N₂-physisorption, SEM, DTA-TGA, and H₂-TPR. It has been established that glycine provides the best yield of CeFeO₃, while the addition of NH₄NO₃ promotes an increase in the amount of CeFeO₃ by 7-12 wt%. In addition, the synthesis of CeFeO₃ with the participation of NH₄NO₃ makes it possible to surpass the activity of the CeO₂-Fe₂O₃ system at low temperatures (300-400 °C), as well as to increase selectivity to hydrocarbons. The observed effects are due to the increased gas evolution and ejection of reactive FeO_x nanoparticles on the surface of crystallites, and an increase in the surface defects. CeFeO₃ obtained in this study allows for achieving higher CO₂ conversion compared to LaFeO₃ at 600 °C.