Search Results (34)

Herein, we present a comprehensive study on the dissolution behaviour of two sodium–cerium(IV) phosphate phases synthesised hydrothermally from CeO₂ nanoparticles: crystalline Na₂Ce(PO₄)₂ and nanocrystalline NaCe₂(PO₄)₃. For the first time, experimental dissolution data were obtained for both compounds over a wide pH range (1.5–10) under long-term equilibration. The crystalline phase undergoes pH-dependent transformation, including recrystallisation at a near-neutral pH and the formation of secondary CeO₂ nanoparticles above pH 7. In contrast, the nanophase NaCe₂(PO₄)₃ exhibits exceptional structural and chemical stability, showing no signs of recrystallisation, phase transformation, or CeO₂ formation, even after extended ageing. The experimental results help refine the thermodynamic stability conditions for cerium phosphate and oxide phases, providing insights into the reversible transformation pathways between CeO₂ and Ce(IV) phosphates as governed by pH. Full article

The elimination of absorbance of excess dye by selective oxidation was first proposed for analytical methods using the formation of ion-association complexes (IAs). On this basis, a new sensitive and selective spectrophotometric method for the determination of phosphate in the form of the IA of 11-molybdovanadophosphate with diindodicarbocyanine (DIDC) was developed. Symmetric diindodicarbocyanine and diindotricarbocyanine dyes can be completely oxidized by sufficiently strong oxidizing agents such as permanganate, dichromate, cerium (IV), and vanadate. Of the three dyes investigated (DIDC, N,N’-dipropyldiindodicarbocyanine, and diindotricarbocyanine), the best results were obtained with DIDC. A mixture of molybdate, vanadate, and nitric acid was preferably used as an oxidizing agent. Selective decolorization of only free dye ions, as well as changes in the IA spectrum compared to the dye spectrum, were explained by the isolation of the dye due to the formation of poorly soluble IA nanoparticles and changes in the redox potential of the dye due to its aggregation. The following optimal conditions for phosphate determination were found: 0.3 M nitric acid, 0.43 mM sodium molybdate, 0.041 mM sodium vanadate, 0.015 mM DIDC, and 18 min for the reaction time. The molar absorptivity of the IA was 1.86 × 10⁵ mol⁻¹·L·cm⁻¹ at 600 nm, and the detection limit for phosphate was 0.013 µM. The developed method was applied to the determination of phosphate in natural water samples. Full article

Magnesium-based alloys are considered to be promising materials for the fabrication of temporary bone repair medical implants. The AZ31 magnesium-based (AZ31-Mg) alloy contains 3% aluminum and 1% zinc in its microstructure, which gives it mechanical strength and corrosion resistance. Nonetheless, the corrosion rate is high, which can lead to implant failure due to rapid degradation, which triggers the release of harmful metal ions. In the present work, a passive layer was obtained on the AZ31-Mg alloy, and subsequently, a cerium oxide (CeO₂) coating was deposited through a chemical conversion treatment using 0.01 M CeO₂ as a precursor. Based on X-ray photoelectron spectroscopy, the calculated amount of Ce(IV) and Ce(III) present in AZ31-Mg(OH)₂/CeO₂ was 93.6% and 6.4%, respectively. AZ31-Mg(OH)₂/CeO₂ showed improved corrosion resistance compared with the bare sample. The in vitro assessment of MC3T3-E1 pre-osteoblast cell viability showed that AZ31-Mg(OH)₂/CeO₂ was biocompatible after incubation for 24 and 72 h. The results revealed that the CeO₂ coating confers greater electrochemical stability and biocompatibility properties, mostly due to the presence of Ce⁴⁺ ions. Full article

Redox flow batteries (RFBs), with distinct characteristics that are suited for grid-scale applications, stand at the forefront of potential energy solutions. However, progress in RFB technology is often impeded by their prohibitive cost and the limited availability of essential research and development test cells. Addressing this bottleneck, we present herein an open-source device tailored for RFB laboratory research. Our proposed device significantly lowers the financial barriers to research and enhances the accessibility of vital equipment for RFB studies. Employing innovative fabrication methods such as laser cutting, 3D printing, and CNC machining, a versatile and efficient flow cell has been designed and fabricated. Furthermore, our open laboratory research equipment comprises the Opensens potentiostat, charge/discharge testing devices, peristaltic pumps, and inexpensive rotating electrodes. Every individual element contributes significantly to the establishment of an all-encompassing experimental configuration that is both economical and efficient, thereby facilitating expedited progress in RFB research and development. Full article

Engineering plastics, such as polyoxymethylene (POM), are high-performance thermoplastics designed to withstand high temperature or mechanical stress and are used in electronic equipment, the automotive industry, construction, or specific household utensils. POM is immiscible with other plastics but due to a low volume of production, no methods were developed to separate it from the residual plastic waste stream. Therefore, POM recycling is minimal despite its high market value. This paper provides a proof of concept for tracer-based sorting (TBS) as a potential solution for increasing the separation efficiency of low-volume, high-quality polymers. For this purpose, yttrium oxide (Y₂O₃) and cerium (IV) oxide (CeO₂) have been embedded into the POM matrix. Mechanical tests of samples at varying concentrations (0.1 to 1000 ppm) of both tracers were conducted, followed by an analysis of detectability and dispersibility using a portable X-ray fluorescence spectrometer (p-XRF), subsequently optimizing detection time and tracer concentration. Finally, an experimental scenario was developed to test the fate and potential recovery of the tracer material after the thermal treatment of plastics. A low detectable concentration, short measurement time, low influence on mechanical parameters of the compound, and low loss ratio after simulated recycling prove Y₂O₃ to be a suitable tracer for the industrial implementation of TBS. Full article

Thin films of transition metal oxides and oxynitrides have proven highly effective in protecting stainless steels against corrosion in both chemically aggressive environments and biological fluids. In the present work, cerium zirconium oxynitride thin films were deposited to enhance the corrosion resistance of surgical-grade stainless steel to be used in osteosynthesis processes. Two techniques were employed: co-sputtering and radiofrequency (RF) sputtering, and the morphology and corrosion efficiency of the coatings deposited by each technique were evaluated. X-ray diffraction, X-ray photoelectron spectroscopy and field emission transmission electron microscopy were used to characterize the morphological and chemical structure, respectively. Additionally, the corrosion resistance of the oxynitride-coated surgical grade stainless steel system (ZrCeO_xN_y-AISI 316L) was assessed using Hank’s solution as the corrosive electrolyte, to determine its resistance to corrosion in biological media. The results show that ZrCeO_xN_y coatings increase the corrosion resistance of surgical grade stainless steel by two orders of magnitude and that the Ce(III)/Ce(IV) equilibrium decreases the corrosion rate, thereby increasing the durability of the steel in a biological environment. The results show that Ce coatings increase the corrosion resistance of surgical grade stainless steel by two orders of magnitude and that the Ce(III)/Ce(IV) equilibrium decreases the corrosion rate, thereby increasing the durability of the steel in a biological environment. Full article

Solifenacin (SFC) is a potent muscarinic antagonist that effectively reduces bladder muscle contraction, thereby alleviating symptoms such as frequency of micturition and urgency. Oxidation of SFC leads to the formation of impurities like Impurity K. Effective analysis and control of this impurity is crucial for ensuring compliance with regulatory standards and safeguarding patient health. To address these challenges, we propose a novel one-step synthesis of Impurity K from SFC. Impurity K was synthesized using cerium(IV) ammonium nitrate (CAN) in water/acetonitrile as the solvent. Additionally, we describe a new HPLC-MS method for the detection of Impurity K in solifenacin succinate tablets. Full article

This study introduces a novel approach to synthesising a three-dimensional (3D) micro-nanostructured amorphous biosilica. The biosilica is coated with cerium oxide nanoparticles obtained from laboratory-grown unicellular photosynthetic algae (diatoms) doped metabolically with cerium. This unique method utilises the ability of diatom cells to absorb cerium metabolically and deposit it on their silica exoskeleton as cerium oxide nanoparticles. The resulting composite (Ce-DBioSiO₂) combines the unique structural and photonic properties of diatom biosilica (DBioSiO₂) with the functionality of immobilised CeO₂ nanoparticles. The kinetics of the cerium metabolic insertion by diatom cells and the physicochemical properties of the obtained composites were thoroughly investigated. The resulting Ce-DBioSiO₂ composite exhibits intense Stokes fluorescence in the violet–blue region under ultraviolet (UV) irradiation and anti-Stokes intense violet and faint green emissions under the 800 nm near-infrared excitation with a xenon lamp at room temperature in an ambient atmosphere. Full article

In the ongoing search for practical uses of rare-earth metal nanoparticles, cerium dioxide nanoparticles (nanoceria) have received special attention. The purpose of this research was to study the biomedical effects of nanocrystalline forms of cerium oxide obtained by different synthesis schemes and to evaluate the effect of different concentrations of nanoceria (from 10⁻² to 10⁻⁶ M) on cells involved in the regeneration of skin cell structures such as fibroblasts, mesenchymal stem cells, and keratinocytes. Two different methods of nanoceria preparation were investigated: (1) CeO-NPs-1 by precipitation from aqueous solutions of cerium (III) nitrate hexahydrate and citric acid and (2) CeO-NPs-2 by hydrolysis of ammonium hexanitratocerate (IV) under conditions of thermal autoclaving. According to the X-ray diffraction, transmission electron microscopy, and dynamic light scattering data, CeO₂-1 consists of individual particles of cerium dioxide (3–5 nm) and their aggregates with diameters of 60–130 nm. CeO₂-2 comprises small aggregates of 8–20 nm in diameter, which consist of particles of 2–3 nm in size. Cell cultures of human fibroblasts, human mesenchymal stem cells, and human keratinocytes were cocultured with different concentrations of nanoceria sols (10⁻², 10⁻³, 10⁻⁴, 10⁻⁵, and 10⁻⁶ mol/L). The metabolic activity of all cell types was investigated by MTT test after 48 and 72 h, whereas proliferative activity and cytotoxicity were determined by quantitative cell culture counting and live/dead test. A dependence of biological effects on the method of nanoceria preparation and concentration was revealed. Data were obtained with respect to the optimal concentration of sol to achieve the highest metabolic effect in the used cell cultures. Hypotheses about the mechanisms of the obtained effects and the structure of a fundamentally new medical device for accelerated healing of skin wounds were formulated. The method of nanoceria synthesis and concentration fundamentally and significantly change the biological activity of cell cultures of different types—from suppression to pronounced stimulation. The best biological activity of cell cultures was determined through cocultivation with sols of citrate nanoceria (CeO-NPs-1) at a concentration of 10⁻³–10⁻⁴ M. Full article

This study aims to investigate the impact of CeO₂ content and particle size on the radiation shielding abilities of polydimethylsiloxane, also known as silicon rubber (SR). We prepared different SR samples with 10, 30, and 50% of micro and nano CeO₂ and we measured the linear attenuation coefficient (LAC) for these samples. We found that the LAC of the SR increases by increasing the CeO₂ and all prepared SR samples had higher LACs than the pure SR. We examined the effect of the size of the particles on the LAC and the results demonstrated that the LAC for nano CeO₂ is higher than that of micro CeO₂. We investigated the half value layer (HVL) for the prepared SR samples and the results revealed that the SR with 10% micro CeO₂ had a greater HVL than the SR with 10% nano CeO₂. The HVL results demonstrated that the SR containing nanoparticles had higher attenuation effectiveness than the SR with micro CeO₂. We also prepared SR samples containing CeO₂ in both sizes (i.e., micro and nano) and we found that the HVL of the SR containing both sizes was lower than the HVL of the SR with nano CeO₂. The radiation protection efficiency (RPE) at 0.059 MeV for the SR with 10% micro and nano CeO₂ was 94.2 and 95.6%, respectively, while the RPE of SR containing both sizes (5% micro CeO₂ + 5% micro CeO₂) was 96.1% at the same energy. The RPE results also indicated that the attenuation ability was improved when utilizing the micro and nano CeO₂ as opposed to the micro CeO₂ or nano CeO₂ at 0.662, 1.173, and 1.333 MeV. Full article

Biomass lignin can be used to produce vanillin through an oxidation process. Although its purity is high, the processing time and separation efficiency are not ideal. This research aims to produce vanillin directly from Kenaf stalks without separating the lignin first from the lignocellulosic biomass. This method is greener because it does not require the separation of cellulose and hemicellulose from the biomass, thus minimizing the use of acid and alkaline solutions and saving time. A high oxygen storage capacity and release capacity of ceria as an oxidation catalyst contribute to the reversable redox properties between Ce⁴⁺ and Ce³⁺ in ceria lattice. Cerium oxide nanostructures were synthesized using a hydrothermal method treated under alkaline NaOH, followed by drying at 120 °C for 16 h and calcining at different temperatures between 400 and 600 °C for the direct oxidation of Kenaf stalks to vanillin under microwave irradiation. The catalysts were characterized for their physicochemical properties using XRD, N₂ adsorption–desorption isotherms and TEM. All synthesized CeO₂ nanostructures showed the presence of diffraction peaks assigned to the presence of cubic fluorite. The N₂ adsorption–desorption isotherms showed that all catalysts possess a Type IV isotherm, indicating a mesoporous structure. The TEM image shows the uniform shape of the CeO₂ nanostructures, while HRTEM images show that the CeO₂ nanostructures are single-crystalline in nature. All catalysts were tested for the direct oxidation of Kenaf stalks using H₂O₂ as the oxidizing agent in temperatures ranging from 160 to 180 °C for 10–30 min with 0.1–0.3 g catalyst loading under 100–500 W of microwave irradiation. The CeO₂-Nps-400 catalyst produced the highest vanillin yields of 3.84% and 4.32% for the direct oxidation of Kenaf stalks and extraction of lignin from Kenaf stalks, respectively. Compared to our earlier study, the highest vanillin yields of 2.90% and 3.70% for direct biomass and extracted lignin were achieved using a Ce/MgO catalyst. Full article

Hydrogels have been proposed as potential candidates for many different applications. However, many hydrogels exhibit poor mechanical properties, which limit their applications. Recently, various cellulose-derived nanomaterials have emerged as attractive candidates for nanocomposite-reinforcing agents due to their biocompatibility, abundance, and ease of chemical modification. Due to abundant hydroxyl groups throughout the cellulose chain, the grafting of acryl monomers onto the cellulose backbone by employing oxidizers such as cerium(IV) ammonium nitrate ([NH₄]₂[Ce(NO₃)₆], CAN) has proven a versatile and effective method. Moreover, acrylic monomers such as acrylamide (AM) may also polymerize by radical methods. In this work, cerium-initiated graft polymerization was applied to cellulose-derived nanomaterials, namely cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF), in a polyacrylamide (PAAM) matrix to fabricate hydrogels that display high resilience (~92%), high tensile strength (~0.5 MPa), and toughness (~1.9 MJ/m³). We propose that by introducing mixtures of differing ratios of CNC and CNF, the composite’s physical behavior can be fine-tuned across a wide range of mechanical and rheological properties. Moreover, the samples proved to be biocompatible when seeded with green fluorescent protein (GFP)-transfected mouse fibroblasts (3T3s), showing a significant increase in cell viability and proliferation compared to samples comprised of acrylamide alone. Full article

Mixed-valence cerium oxide nanoparticles (nanoceria) have been investigated with pronounced interest due to a wide range of biomedical and industrial applications that arises from its remarkable redox catalytic properties. However, there is no understanding of how to control the formation of these two types of nanoceria to obtain Ce³⁺/Ce⁴⁺ ratios required in various applications. In this work, using a soluble borate glass, nanoceria with specific ratios of Ce³⁺/Ce⁴⁺ are created and extracted via controlled glass-melting parameters. Glass embedded with nanoceria as well as nanoceria extracted from the glass were studied via XANES and fitted with the Multivariate Curve Resolution (MCR) technique to calculate the ratio of Ce³⁺/Ce⁴⁺. Results show that mixed-valence nanoceria with specific ratios are hermetically sealed within the glass for long durations. When the glass dissolves, the mixed-valence nanoceria are released, and the extracted nanoceria have unchanged Ce³⁺/Ce⁴⁺ ratios. Furthermore, TEM investigation on released nanoceria show that the nanoceria consist of several different structures. Although nanocrystal structures of Ce₇O₁₂, Ce₁₁O₂₀, and Ce₂O₃ contribute to the reduced state, a new quasi-stable phase of CeO1.66 has been observed as well. Full article

In this study, the poisoning effects of cerium oxide (${\mathrm{CeO}}_2$) as the contaminant on the performance of proton exchange membrane fuel cells (PEMFCs) are evaluated. An experimental setup was developed to analyze the performance characteristic (I-V) curves in contaminated and non-contaminated conditions. Focused ion-beam scanning electron microscopy (FIB-SEM) cross-section images were obtained as an input for the energy dispersive X-ray (EDX) analysis. The results of the EDX analysis verified the presence of ${\mathrm{CeO}}_2$ in the contaminated membrane electrode assembly (MEA), in addition to fluorine and sulfur. EDX analysis also revealed that as a result of ${\mathrm{CeO}}_2$ contamination, sulfur and fluorine would be distributed all around the MEA, instead of being only in the membrane. The results illustrate that hydrofluoric acid (HF), sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$), and fluorinated polymer fragments are released, which enhance the crossover of the reactant gases through the membrane, hence reducing the cell’s performance. The I-V characteristic curves proved that the non-contaminated PEMFC setup had double the performance of the contaminated PEMFC. Full article

Recently, manganese oxides (MnO_x)/cerium(IV) oxide (CeO₂) composites have attracted widespread attention for the selective catalytic reduction (SCR) of nitrogen oxides (NO_x) with ammonia (NH₃), which exhibit outstanding catalytic performance owing to unique features, such as a large oxygen storage capacity, excellent low-temperature activity, and strong mechanical strength. The intimate contact between the components can effectively accelerate the charge transfer to enhance the electron–hole separation efficiency. Nevertheless, MnO_x/CeO₂ still reveals some deficiencies in the practical application process because of poor thermal stability, and a low reduction efficiency. Constructing MnO_x/CeO₂ with other semiconductors is the most effective strategy to further improve catalytic performance. In this article, we discuss progress in the field of MnO_x/CeO₂-based ternary composites with an emphasis on the SCR of NO_x by NH₃. Recent progress in their fabrication and application, including suitable examples from the relevant literature, are analyzed and summarized. In addition, the interaction mechanisms between MnO_x/CeO₂ catalysts and NO_x pollutants are comprehensively dissected. Finally, the review provides basic insights into prospects and challenges for the advancement of MnO_x/CeO₂-based ternary catalysts. Full article