Design of S-Scheme CuInS2/CeO2 Heterojunction for Enhanced Photocatalytic Degradation of Pharmaceuticals in Wastewater

The release of common medications and illegal drugs into the environment could be potentially harmful to the ecosystem and hamper the behavior and growth of plants and animals. These pollutants gain access to water through sewage and factory discharges and have been found to exceed safety limits in water bodies. Therefore, there is an urgent need for improved wastewater purification systems. In this study, semiconductor-based heterojunction photocatalyst CuInS2/CeO2, synthesized through a facile solvothermal process, was explored for the photocatalytic degradation of ciprofloxacin, commonly used antibiotics. Studies on the electronic properties of the heterojunction revealed interfacial characteristics that were suitable for enhanced charge carrier separation and transport and a potential S-scheme charge transfer mechanism. The heterojunction achieved ∼90% efficiency for the degradation of CIP compared to 60% and 12% reported for CeO2 and CuInS2, respectively. This shows an improvement in the activity, which results from the improved charge carrier properties of the heterojunction. Further investigation of the charge transfer mechanism through radical scavenging experiments identified •OH, O2•-, and h+ as active species contributing to the catalyst's efficacy. Based on X-ray photoelectron spectroscopy analysis, a proposed S-scheme charge transfer mechanism was suggested for the CuInS2/CeO2 heterojunction. The findings indicate the potential of the CuInS2/CeO2 heterojunction as a promising photocatalyst for treating waste effluents from the pharmaceutical industry.

Impact of morphology and oxygen vacancy content in Ni, Fe co-doped ceria for efficient electrocatalyst based water splitting

Designing a highly efficient, low-cost, sustainable electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through water splitting is a current challenge for renewable energy technologies. This work presents a modified sol-gel route to prepare metal-ion(s) doped cerium oxide nanostructures as an efficient electrocatalyst for overall water splitting. Nickle (Ni) and iron (Fe) co-doping impacts the morphology in cerium oxide resulting in 5 nm nanoparticles with a mesoporous-like microstructure. The high level 20 mol% (1 : 1 ratio) of Ni + Fe bimetal-ion(s) doped CeO2 shows excellent HER and OER activities compared to the monodoped Fe/Ni and pristine CeO2. The co-doped catalysts required a low overpotential of 104 mV and 380 mV for HER and OER, respectively, in 1 M KOH, at a current density of 10 mA cm-2. The Tafel slopes of 95 mV dec-1 and 65 mV dec-1 were measured for HER and OER with the same representative samples which demonstrated excellent stability even after continuous operation for 20 hours in the alkaline medium. The unique morphology, enhanced oxygen vacancy (Ov) content and the synergistic effects of dopants in CeO2 play essential roles in enhancing the activities of Ni + Fe doped samples.

Two decades of ceria nanoparticle research: structure, properties and emerging applications

Cerium oxide nanoparticles (CeNPs) are versatile materials with unique and unusual properties that vary depending on their surface chemistry, size, shape, coating, oxidation states, crystallinity, dopant, and structural and surface defects. This review encompasses advances made over the past twenty years in the development of CeNPs and ceria-based nanostructures, the structural determinants affecting their activity, and translation of these distinct features into applications. The two oxidation states of nanosized CeNPs (Ce3+/Ce4+) coexisting at the nanoscale level facilitate the formation of oxygen vacancies and defect states, which confer extremely high reactivity and oxygen buffering capacity and the ability to act as catalysts for oxidation and reduction reactions. However, the method of synthesis, surface functionalization, surface coating and defects are important factors in determining their properties. This review highlights key properties of CeNPs, their synthesis, interactions, and reaction pathways and provides examples of emerging applications. Due to their unique properties, CeNPs have become quintessential candidates for catalysis, chemical mechanical planarization (CMP), sensing, biomedical applications, and environmental remediation, with tremendous potential to create novel products and translational innovations in a wide range of industries. This review highlights the timely relevance and the transformative potential of these materials in addressing societal challenges and driving technological advancements across these fields.

Ultra-fast photocatalytic degradation and seed germination of band gap tunable nickel doping ceria nanoparticles

Doping transition metal ions into cerium oxide (CeO₂) results in interesting modifications to the material, including an increase in surface area, a high isoelectric point, biocompatibility, greater ionic conductivity, and catalytic activity. Herein, various concentrations (1-5%, 10% and 20%) of nickel (Ni) doped CeO₂ nanoparticle have been made by a facile chemical process. Using a variety of cutting-edge analytical techniques, the structural, optical, and photocatalytic properties of undoped and varied concentrations (1-5%, 10%, and 20%) of Ni doped CeO₂ nanoparticles have been investigated. Pure cubic fluorite structure with average crystallite sizes in the region of 12-15 nm was determined by X-ray diffraction (XRD) investigation. High resolution electron microscopy (HR-TEM), which revealed highly homogeneous hexagonal shape of the particles with average size of 15 nm, was also used to determine microstructural information. According to the optical absorption, the band gaps of Ni doped and undoped CeO₂ nanoparticles were found to be 2.96 eV and 1.95 eV, respectively. When exposed to sunlight, the narrow band gap Ni doped CeO₂ nanoparticles worked as an active visible light catalyst to remove the dyes Rose Bengal (RB) and Direct Yellow (DY). The best photodegradation efficiencies for RB and DY dyes were found about 93% and 97%, respectively, using the 5% Ni-doped CeO₂ catalyst. The apparent rate constant values of 0.039 for RB and 0.040 min^-1 were attained for DY. As well, the treated, untreated dye solution and control solutions were utilized to assess the toxicity of commercially accessible Vigna Radiata seeds. In this study exhibits percentages of length and germination increased by 30-35% when compared to dye pollutant solution. The Ni doped CeO₂ can provide a substantial alternative for current industrial waste management because of its quick photocatalytic activity and remarkable seed germination results.

Self-propelled nanojets an interfacial Schottky junctions modulated oxygen vacancies enriched for enhanced photo-Fenton degradation of organic contaminant: Improving H2O2 generation, Fe3+/Fe2+ cycle and enhancing plant metabolism

The study reports an innovative approach on sunlit driven heterostructure photocatalytic generation of H₂O₂ and removal of cefixime. In the present work, we have fabricated Mn/Mg doped CoFe₂O₄ modified CaCr₂O₄ decorated by Ag₃PO₄ quantum dots (Ag₃PO₄ QDs), a p-n-p nano heterojunction. The study promotes the photocatalytic production of H₂O₂ and self-Fenton photocatalytic degradation of cefixime. Egg white-assisted synthesis of Mn-doped CoFe₂O₄ causes the lattice oxygen defect, which enhances the photocatalytic activity. Lattice oxygen defect enable the adsorption of O₂, which enable the conversion of •O² in the valence band of CoFe₂O₄ for the endogenous production of H₂O₂. The higher in the surface area enhance the photocatalytic activity under visible light irradiation. Mn-CoFe₂O₄-CaCr₂O₄-Ag₃PO₄ QDs enables the complete photocatalytic degradation of cefixime (99.9%) and the complete removal was determined by total organic carbon (TOC) removal and it was around 99.4%. Meanwhile the photocatalytic degradation pathway of cefixime was determined by LC-MS/MS. Reusability of the nano heterojunction was determined by six cycle test, and the reusability of the nano heterojunction was 99.8%. Further, the toxicity of the nanomaterial was studied in maize plant and the results shows that the nanoheterojunction enhances the maize growth. The study systematically reveals the robust activity of nano heterojunction for sustainable water treatment.

One-pot microwave-hydrothermally synthesized carbon nanotube-cerium oxide nanocomposites for enhanced visible photodegradation of acid orange 7

Carbon nanotubes (CNT)-cerium oxide (CeO2) nanocomposites were fabricated successfully by one-pot microwave hydrothermal growth of regular CeO2 nanoparticles with a size of 8 nm on hydroxyl-functionalized multi-walled CNTs. These nanocomposite photocatalysts demonstrated an acid orange (AO7) photocatalytic degradation efficiency of above 90% under solar-simulated light irradiation for 3 h, which was much higher than that of the pure CeO2 nanoparticles. The enhanced photocatalytic activity was observed to mainly originate from the ˙O2- and hole traps, while the hydroxyl radical ˙OH played a secondary role.

In-vitro interaction of cerium oxide nanoparticles with hemoglobin, insulin, and dsDNA at 310.15 K: Physicochemical, spectroscopic and in-silico study

Lanthanide nanoparticles and nanorods especially their biocompatible oxide forms like cerium oxide nanoparticles (CNPs) with therapeutic applications are used to cure neurological oxidative stresses. Thus it tempts to study their biocompatible aspects by interactions with several biologically significant molecules. In-Vitro interactions of 15-240 μM CNPs with water, Phosphate buffered saline (PBS), DMEM media, Insulin (Ins) hemoglobin (Hb) and ds-DNA at 37 °C were studied. Their physicochemical properties study by Borosil Mansingh Survismeter (BMS) showed the first order interaction with the protein-protein structure breaking behaviour of CNPs with Hb, Ins, and DNA. Zeta potential measurements of CNPs in different biological medium show a net increase in negative charge magnitude with good colloidal stability. K_b = 4 × 106 mM^-1 of CNPs-DNA infer noncovalent interactions. Circular dichroism and FTIR revealed a loss of secondary conformation with increasing CNPs concentration. In-silico molecular docking depicts CNP interaction via conventional hydrogen bonding, carbon hydrogen bonding and electrostatic interactions at the minor groove of DNA. The study reports in-dept unfolding functional mechanism investigated by physicochemical, spectroscopic, and In-Silico approaches of protein on interactions with CNPs for safer-by-design use in medicine and pharmaceutics. Fundamentally the CeO₂ in ~62% and Ce₂O₃ in ~38% with Ce⁴⁺ and Ce³⁺ oxidation potentials develop a unique case of electronic configurations with 4f⁰5d⁰6s⁰ and 4f¹5d⁰6s⁰ electrons respectively which these studies a novel one.

Efficient Removal of Heavy Metals from Aqueous Solutions Using a Bionanocomposite of Eggshell/Ag-Fe

Eggshell and an easily synthesized bionanocomposite of eggshell with Ag-Fe nanoparticles demonstrated to be efficient adsorbent materials for the removal of lead, arsenic, and mercury from water. The natural material and the bionanocomposite were characterized by TEM and XRD. Ag-Fe nanoparticles vary from 1 to 100 nm in size. Equilibrium times of the adsorption systems were achieved between 4 and 8 h. The experimental adsorption data fitted the pseudo-second and Elovich models; therefore, the adsorption of heavy metals ions took place mainly by a chemical process. The adsorption capacity of eggshell in mg/g was 7.01 for As5+, 3.90 for Pb2+, and 1.51 for Hg2+, while the nanocomposite adsorption capacity was 17.7 for As5+, 27.8 for Pb2+ and 15.88 for Hg2+.

ATP fosters the tuning of nanostructured CeO2 peroxidase-like activity for promising antibacterial performance

Recyclable nano CeO₂ POD mimic records a K_m reduction (∼30% and ∼19.72% for TMB and H₂O₂, respectively) in 900 seconds at pH 4.5. ATP boosts catalytic feasibility in nano CeO₂ at physiological pH.

Physicochemical interaction of cerium oxide nanoparticles with simulated biofluids, hemoglobin, insulin, and ds-DNA at 310.15 K

Interaction study in cerium oxide nanoparticles with biofluids and biomolecules via physicochemical, spectroscopic and in silico analytical approaches, showing conformational change.

Synthesis and Dissolution of Metal Oxides in Ionic liquids and Deep Eutectic Solvents

Ionic liquids (ILs) and deep eutectic solvents (DESs) have proven to be suitable solvents and reactants for low-temperature reactions. To date, several attempts were made to apply this promising class of materials to metal oxide chemistry, which, conventionally, is performed at high temperatures. This review gives an overview about the scientific approaches of the synthesis as well as the dissolution of metal oxides in ILs and DESs. A wide range of metal oxides along with numerous ILs and DESs are covered by this research. With ILs and DESs being involved, many metal oxide phases as well as different particle morphologies were obtained by means of relatively simple reactions paths. By the development of acidic task-specific ILs and DESs, even difficultly soluble metal oxides were dissolved and, hence, made accessible for downstream chemistry. Especially the role of ILs in these reactions is in the focus of discussion.

Rapid microwave-assisted hydrothermal synthesis of CeO2 octahedra with mixed valence states and their catalytic activity for thermal decomposition of ammonium perchlorate

CeO₂ octahedra are prepared rapidly and they exhibit improved catalytic activity due to high concentration of oxygen vacancies and exposed (111) facets.

Morphological investigations on the growth of defect-rich Bi2Te3 nanorods and their thermoelectric properties

Bi₂Te₃ nanorods (NRs) have been successfully synthesized at different reaction temperatures via a surfactant-assisted hydrothermal method.

The effect of Eu doping on the growth, structure and red-ox activity of ceria nanocubes

The ordering of oxygen vacancies (in high Eu-doped (x ≥ 0.1) ceria nanoparticles) facilitates the process of Ce⁴⁺ to Ce³⁺ reduction.

Microwave-assisted hydrothermal synthesis of cobalt phosphide nanostructures for advanced supercapacitor electrodes

Co₂P nanoshuttles which demonstrated remarkable electrochemical performance were synthesized for the first time by a microwave-assisted hydrothermal method. A combined oriented attachment and Ostwald ripening mechanism is proposed for the formation of Co₂P nanoshuttles.

Synthesis, design and sensing applications of nanostructured ceria-based materials

Cerium-based materials possess redox properties due to the presence of dual valence states of Ce³⁺ and Ce⁴⁺.

Size controlled ultrafine CeO2 nanoparticles produced by the microwave assisted route and their antimicrobial activity

Cerium oxide (CeO₂) nanoparticles (NPs) have a wide range of biological and biomedical applications. This work describes a new methodology for producing ultrafine, highly uniform NPs with controlled sizes using the chemical microwave assisted route. The size of CeO₂-NPs decreased from 10 to 5 nm by increasing the molar ratio of cerium nitrate Ce(NO₃)₃.(6H₂O) to that of hexamethylenetetramine (C₆H₁₂N) from 1:20 to 20:20. Detailed information about their structural characterization was obtained from the XRD, UV-visible, photoluminescence, Raman spectroscopy, SEM, TEM and AFM. These CeO₂-NPs were tested as antimicrobial agent against Gram-negative (Escherichia.coli), Gram-positive (Bacillus.subtilis) bacteria and yeast (Saccharomyces cerevisiae). The obtained results showed significant inhibition of these strain even at low concentration of CeO₂-NPs. The CeO₂-NPs with the molar ratio 5:20 had the most effective inhibition against E.coli (~70%) at a concentration of 20 µL. The CeO₂-NPs with the ratio 12:20 were found to be the most effective against B.subtilis (inhibition ~68%). On the other hand, CeO₂-NPs synthesized with the 20:20 molar ratio caused the highest inhibition for S. cerevisiae (~60%). It is observed that at higher NPs concentration (i.e., >20 µL) the inhibition of these strains decreased. The antimicrobial activity may be attributed to the penetrating power of CeO₂-NPs size beside the generated oxygen species radicals that caused inhibition of bacterial growth.

Predicting NOx Catalysis by Quantifying Ce3+ from Surface and Lattice Oxygen

Our work introduces a novel technique based on the magnetic response of Ce³⁺ and molecular oxygen adsorbed on the surface of nanoceria and ceria-based catalysts that quantifies the number and type of defects and demonstrates that this information is the missing link that finally enables predictive design of NO_x catalysis in ceria-based systems. The new insights into ceria catalysis are enabled by quantifying the above for different ceria nanoparticle shapes (i.e., surface terminations) and O₂ partial pressure. We used ceria nanorods, cubes, and spheres and evaluated them for catalytic reduction of NO by CO. We then demonstrated the quantitative prediction of the reactivity of nanomaterials via their magnetism in different atmospheric environments. We find that the observed enhancement of reactivity for ceria nanocubes and nanorods is not directly due to improved reactivity on those surface terminations but rather due to the increased ease of generating lattice defects in these materials. Finally, we demonstrate that the method is equally applicable to highly topical and industrially relevant ceria mixed oxides, using nanoscale alumina-supported ceria as a representative case-a most ill-defined catalyst. Because the total oxide surface is a mixture of active ceria and inactive support and ceria is not likely present as crystallographically well-defined phases, reactivity does not easily scale with surface area or a surface termination. The key parameter to design efficient NO reduction in ceria-based catalysts is knowing and controlling the surface localized excess Ce³⁺ ion areal density.

Growth mechanism of ceria nanorods by precipitation at room temperature and morphology-dependent photocatalytic performance

Ceria (CeO₂) nanorods have been prepared by simple short-term precipitation at room temperature for the first time.

Ni–CeO2 spherical nanostructures for magnetic and electrochemical supercapacitor applications

Ni–CeO₂ spherical nano structures prepared using microwave assisted method and a specific capacitance of 577 F g⁻¹ was achieved at 2 A g⁻¹ in 1 M KOH.

Synthesis of Ordered Mesoporous CuO/CeO₂ Composite Frameworks as Anode Catalysts for Water Oxidation

Cerium-rich metal oxide materials have recently emerged as promising candidates for the photocatalytic oxygen evolution reaction (OER). In this article, we report the synthesis of ordered mesoporous CuO/CeO₂ composite frameworks with different contents of copper(II) oxide and demonstrate their activity for photocatalytic O₂ production via UV-Vis light-driven oxidation of water. Mesoporous CuO/CeO₂ materials have been successfully prepared by a nanocasting route, using mesoporous silica as a rigid template. X-ray diffraction, electron transmission microscopy and N₂ porosimetry characterization of the as-prepared products reveal a mesoporous structure composed of parallel arranged nanorods, with a large surface area and a narrow pore size distribution. The molecular structure and optical properties of the composite materials were investigated with Raman and UV-Vis/NIR diffuse reflectance spectroscopy. Catalytic results indicated that incorporation of CuO clusters in the CeO₂ lattice improved the photochemical properties. As a result, the CuO/CeO₂ composite catalyst containing ~38 wt % CuO reaches a high O₂ evolution rate of ~19.6 µmol·h-1 (or 392 µmol·h-1·g-1) with an apparent quantum efficiency of 17.6% at λ = 365 ± 10 nm. This OER activity compares favorably with that obtained from the non-porous CuO/CeO₂ counterpart (~1.3 µmol·h-1) and pure mesoporous CeO₂ (~1 µmol·h-1).

Antioxidant Potential and Toxicity Study of the Cerium Oxide Nanoparticles Synthesized by Microwave-Mediated Synthesis

Monodispersed cerium oxide nanoparticle has been synthesized by microwave-mediated hydrothermal as well as microwave-mediated solvothermal synthesis. X-ray diffraction (XRD) data shows that the synthesized particles are single phase. SEM and TEM analysis suggest that particle synthesized by microwave-mediated solvothermal method are less agglomerated. In vitro toxicology study of the synthesized nanoceria particles has shown good free radical scavenging activity for NO and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assayed except superoxide radical within a concentration range of 25 to 75 ng ml(-1). Nanoceria particle also showed inhibition of Fe-ascorbate-induced lipid peroxidation (LPx) in chick liver mitochondrial fractions. Solvothermally synthesized nanoceria showed better protection against Fe-ascorbate-induced LPx than the hydrothermal one while the hydrothermally synthesized nanoceria showed better DPPH and NO scavenging activity. The ceria nanoparticles also prevented Fe-ascorbate-H2O2-induced carbonylation of bovine serum albumin in a dose-dependent manner. At higher concentration, i.e., 100 ng ml(-1), the synthesized nanoparticles showed a reverse trend in all the parameters measured indicating its toxicity at higher doses.

Dielectrical Properties of CeO2 Nanoparticles at Different Temperatures

A template-free precipitation method was used as a simple and low cost method for preparation of CeO₂ nanoparticles. The structure and morphology of the prepared nanoparticle samples were studied in detail using X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM) measurements. The whole powder pattern modelling (WPPM) method was applied on XRD data to accurately measure the crystalline domain size and their size distribution. The average crystalline domain diameter was found to be 5.2 nm, with a very narrow size distribution. UV-visible absorbance spectrum was used to calculate the optical energy band gap of the prepared CeO₂ nanoparticles. The FT-IR spectrum of prepared CeO₂ nanoparticles showed absorption bands at 400 cm^-1 to 450 cm^-1 regime, which correspond to CeO₂ stretching vibration. The dielectric constant (ε_r) and dielectric loss (tan δ) values of sintered CeO₂ compact consolidated from prepared nanoparticles were measured at different temperatures in the range from 298 K (room temperature) to 623 K, and at different frequencies from 1 kHz to 1 MHz.

The role of oxygen vacancies and their location in the magnetic properties of Ce1−xCuxO2−δ nanorods

Ceria (CeO₂) is a promising dilute magnetic semiconductor. The ferromagnetic order has proven to be an surface effect.

Unexpected production of singlet oxygen by sub-micron cerium oxide particles and enhanced photocatalytic activity against methyl orange

Photodegradation of methyl orange (MO) by hydrothermally grown cerium oxide (CeO₂) particles has been studied. Unexpected production of singlet oxygen is reported..