Nanostructured Cerium Oxide Research Articles

Continuous flow production of bioactive ceria quantum dots: New paradigms to the effect of process parameters on surface oxygen vacancy tuning

Precisely monitored nucleation-growth kinetics for governing the size, surface chemistry, and sought-after attributes of quantum dots (QDs) for large-scale manufacturing remains a formidable challenge. This study evinces the importance of ultrafast mixing and high heating rates for rapid nucleation, particularly in synthesizing monodispersed QDs with enriched surface defects. Recently, cerium oxide (CeO2) nanostructures have gained prominence in antioxidant therapy owing to the co-existence of Ce3+ and Ce4+. However, current batch processes lack scalability, reproducibility, and control over the reaction kinetics, key for fine-tuning the surface defect-driven properties of CeO2 nanostructures. Addressing this knowledge gap, we demonstrate a unique, sustainable, continuous flow platform that allows simultaneous engineering of surface oxygen vacancies (VO●) and regulates the size of L arginine functionalized CeO2 QDs (VO●-rich l-arg-CeO2 QDs). Introduction of the helical coil reactor regulated by dean vortices yields monodispersed QDs with enhanced Ce3+/Ce4+ratio and VO● at the surface. Through various experimental methodologies, we showed how adjusting temperature, flowrate, and pH enables achieving the desirable size (3 nm), thereby bestowing an optimal surface Ce3+ and VO● fractions, pivotal for size-dictated photo-response, physiochemical properties, and biofunctionality of the QDs. The abundant surface VO● (72 %) entails narrowing of the band gap (∼ 2.5 eV), resulting in unprecedented photothermal response (ΔT = 19.7 ± 0.6 °C) and photoluminescence, features not typically found in defect-free conventional CeO2 nanostructures. With a strategic combination of process parameters, the defect-rich material system displayed excellent biocompatibility (95.6 %), and antioxidant efficacy on human keratinocyte (HaCaT) cells, and long-term stability (ζ = -29±1.5 mV) in suspensions, even after 120 days. This economical, high throughput continuous flow platform for fabricating biofunctionalized VO●-rich l-arg-CeO2 QDs outperforms conventional batch processes, opening numerous possibilities for lab-to-clinic translation in the fight against oxidative stress-related disorders.

Facile fabrication of single-walled carbon nanotubes@cerium oxide composite sensing platform for ultrasensitive electrochemical analysis of methyl parathion

We proposed a simple and feasible strategy to fabricate the nano-structured cerium oxide (CeO2) nanoparticles decorated single-walled carbon nanotubes networks (SWCNT@CeO2), which was utilized to fabricate the SWCNT@CeO2/GCE sensor for detecting methyl parathion (MP) with high sensitivity. SWCNT possessed the unique one-dimensional hollow nanostructure with excellent conductivity performance, which boosted the charge diffusion rate. CeO2 with good biocompatibility and high catalytic capacity could achieve the adsorption of MP molecules on the surface of sensing electrode due to the affinity of CeO2 nanoparticles towards the phosphate groups of MP. Furthermore, SWCNT could effectively make up for the inherent disadvantage of CeO2 nanoparticles in the term of electrical conductivity. The fabricated SWCNT@CeO2/GCE sensor achieved the ultrasensitive MP electrochemical analysis property (LOD: 9.12 nM). The satisfactory repeatability, reproducibility, anti-interference abilities were obtained at the fabricated sensor. Regarding the electrochemical detection of MP in real food samples, both satisfactory recovery rates of 87.68–107.31% and low RSD of 1.09–2.65% suggested the favorable application prospect of SWCNT@CeO2/GCE sensor in the field of pesticide residue analysis.

Magnetic field-enhanced oxygen reduction reaction for electrochemical hydrogen peroxide production with different cerium oxide nanostructures

We investigated cerium oxide nanoparticles of various morphologies (nanosheets, nanocubes, and nanoparticles) supported on carbon Vulcan XC-72 for the two-electron oxygen reduction reaction (ORR). A continuous magnetic field (2000 Oe) was used for the first time in the literature. The best results were for 5 % (w/w) CeO2 for all three different morphologies, more than doubling the ring current, enhancing the hydrogen peroxide selectivity from 51 % (Vulcan XC-72) to 84–89 %, and modifying the onset potential to lesser negative values. The presence of the magnetic field led to even higher ring currents with 5 % (w/w) CeO2, H2O2 selectivity from 54 % (Vulcan XC-72) to 88–96 % and changing even more the onset potential. Those results were correlated with the Zeeman effect, the Lorentz force, generating magnetohydrodynamic effects, the Kelvin force, and the formation of Bound Magnetic Polarons. This pioneering research introduces an innovative approach, highlighting the potential of an external continuous magnetic field.

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.

Cytotoxicity against human cancer cells and lymphocytes based on cerium oxide nanostructures

Nanomedicine has emerged as a promising avenue for targeted cancer therapy, aiming to develop innovative approaches with improved efficacy and reduced side effects. CeO2 Nanostructures (CeO2 NSs) have attracted considerable attention in biomedical research due to their unique physicochemical properties and potential applications in cancer therapy. In the present article, we studied various methods of synthesis of biocompatible cerium oxide nanoparticles through phyto synthesis (CeO2-P) using Heritiera fomes plant extract and the chemical reducing method (CeO2-C). As obtained, CeO2-P and CeO2-C were characterized using XRD (X-ray diffraction), FTIR(Fourier Transformation Infrared spectroscopy), UV-Visible spectroscopy, and field emission scanning electron microscopy. Further, cytotoxic activity was studied on human cancer cell lines – MDA-MB-231-human breast cancer cell line; HeLa -human cervical cancer cell line; HCT-116- human colon cancer cell line, and human blood mononuclear cells (lymphocytes). A comparative study evaluating the induction of apoptosis by CeO2-P and CeO2-C was performed using propidium iodide staining on the mentioned human cancer cell lines. Toxicity assessment results showed the better performance of CeO2-P nanoparticles against HCT-116 at an IC50 concentration of 6.37 μg/mL compared to CeO2-C nanoparticles (HCT-116 - 8.08μg/mL). Similarly, the CeO2 nanoparticles showed significant cytotoxicity against Hela and MDA-MB-231 cells after 24 h treatments. Interestingly, CeO2-P nanoparticles are less toxic to human blood lymphocytes than CeO2-C nanoparticles. Furthermore, propidium iodide staining revealed the signs of apoptosis in all three human cancer cell lines treated with CeO2-P compared to CeO2-C nanoparticles. In conclusion, these findings provide valuable insights into the potential use of CeO2 nanostructures as a promising therapeutic agent in cancer treatment while exhibiting minimal toxicity towards lymphocytes. Further investigations are warranted to explore the underlying mechanisms and optimize the therapeutic efficacy of CeO2 Nanostructures for targeted cancer therapy.

Direct Oxidation of Hibiscus cannabinus Stalks to Vanillin Using CeO2 Nanostructure Catalysts.

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.

Quantum-Chemical Modeling of Ag/CeO2 Nanoscale Catalysts

The authors summarize results from calculations using the density functional theory for atoms and small silver clusters on surfaces of nanostructured cerium(IV) oxide, along with the adsorption and transformations of O2 and CO molecules on these systems. Stoichiometric Ce21O42, which has {100} and {111} nanofacets with adsorption centers containing four and three oxygen atoms, is used to model surfaces of cerium oxide. It is shown the O4-center is a center of the selective adsorption of metal atoms. A silver atom on an O3‑center is less stable but it shows a greater ability to activate an O2 molecule. Results from calculations on the {100} and {111} faces of Ce21O42 nanoparticles are compared to data for infinite CeO2(100) and CeO2(111) surfaces. The efficiency of Ag/Ce21O42 atomic complexes is shown in the oxidation of carbon monoxide.

Ultrasensitive functionalized CeO2/ZnO nanocomposite sensor for determination of a prohibited narcotic in sports pethidine hydrochloride

The extraordinary features of cerium oxide (CeO2) and zinc oxide (ZnO) nanostructures have encouraged substantial attention to those nanocomposites as probable electroactive complexes for sensing and biosensing purposes. In this study, an advanced novel factionalized CeO2/ZnO nanocomposite-aluminum wire membrane sensor was designed to assess pethidine hydrochloride (PTD) in commercial injection samples. Pethidine-reineckate (PTD-RK) was formed by mixing pethidine hydrochloride and ammonium reineckate (ARK) in the presence of polymeric matrix (polyvinyl chloride) and o-nitrophenyl octyl ether as a fluidizing agent. The functionalized nanocomposite sensor displayed a fast dynamic response and wide linearity for the detection of PTD. It also revealed excellent selectivity and sensitivity, high accuracy, and precision for the determination and quantification of PTD when compared with the unmodified sensor PTD-RK. The guidelines of analytical methodology requirements were obeyed to improve the suitability and validity of the suggested potentiometric system according to several criteria. The developed potentiometric system was suitable for the determination of PTD in bulk powder and commercial products.

Promoted photocatalytic mineralization of atrazine over visible-light active Ag2O/CeO2 nanocomposites with sustainable reusability

Rare earth-based oxide heterojunction photocatalysts have recently demonstrated a significant role in environmental remediation for several pollutants under light irradiation. Particularly, the widespread use of hurtful weed killers such as atrazine (AtZ) in cultivation will induce several impacts on human health and the environment very soon. Thus, this work shows the application of a metal oxide nanocomposite photocatalyst composed of n-type nanostructured cerium oxide (CeO2) supported with p-type silver oxide (Ag2O) for the oxidative mineralization of AtZ in water. The Ag2O/CeO2 nanocomposites with the range of 1.0∼7.0 wt.% of Ag2O were synthesized by the surfactant-assisted sol-gel technique. The physicochemical characterizations of obtained materials indicated the formation of tiny Ag2O nanoparticles anchored to the cubic CeO2 nanocrystals by X-ray diffraction and transmission electron microscope. Also, the visible-light harvesting of Ag2O-loaded samples was better than pure CeO2 as a result of the narrowing of bandgap energy from 2.98 to 2.43 eV with the conservation of the mesostructured surface structure. The 7% Ag2O/CeO2 revealed the best-performed photocatalyst for the complete photooxidation of AtZ within 40 min at an amount of 2.0 g L–1 with a superb reaction rate of 79.23 × 10–3 min–1 and maintainable reusability of 96%. This novel p-n metal oxide heterojunction construction has endorsed the charge separation to the complete remediation of AtZ under visible light.

Influence of Morphology Change on Photoelectrochemical Activity of Cerium Oxide Nanostructures

Aims: Photocatalysis has become a crucial area in the field of energy generation Background: The conversion of solar energy into chemical or thermal energy for various energy related applications has taken precedence over many traditional research areas. Objective: The urgency to become independent of non-renewable energy resources is paramount due to issues of global warming. Objective: The urgency to become independent of non-renewable energy resources is paramount due to issues of global warming. Method: To that end, researchers are exploring various material systems, geometries and material combinations to obtain ideal photocatalysts for efficient solar conversion. Here, the nanostructures were fabricated via electrodeposition. Results and Discussion: The morphology was controlled by varying the concentration of chemical additive, namely dimethyl sulfoxide, during the deposition process. The morphology controlled cerium oxide nanostructures were thoroughly characterized and tested for their photoelectrochemical performances. Conclusion: Our present investigation contributes to this area of research by studying the influence of morphology on the photoelectrochemical activity of cerium oxide nanostructures.

Prospective of Agro-Waste Husks for Biogenic Synthesis of Polymeric-Based CeO2/NiO Nanocomposite Sensor for Determination of Mebeverine Hydrochloride.

The remarkable properties of nickel oxide (NiO) and cerium oxide (CeO2) nanostructures have attracted considerable interest in these nanocomposites as potential electroactive materials for sensor construction. The mebeverine hydrochloride (MBHCl) content of commercial formulations was determined in this study using a unique factionalized CeO2/NiO-nanocomposite-coated membrane sensor. Mebeverine-phosphotungstate (MB-PT) was prepared by adding phosphotungstic acid to mebeverine hydrochloride and mixing with a polymeric matrix (polyvinyl chloride, PVC) and plasticizing agent o-nitrophenyl octyl ether. The new suggested sensor showed an excellent linear detection range of the selected analyte at 1.0 × 10-8-1.0 × 10-2 mol L-1 with regression equation EmV = (-29.429 ± 0.2) log [MB] + 347.86. However, the unfunctionalized sensor MB-PT displayed less linearity at 1.0 × 10-5-1.0 × 10-2 mol L-1 drug solution with regression equation EmV = (-26.603 ± 0.5) log [MB] + 256.81. By considering a number of factors, the applicability and validity of the suggested potentiometric system were improved following the rules of analytical methodological requirements. The created potentiometric technique worked well for determining MB in bulk substance and in medical commercial samples.

Crystallinity-modulated hollow CeO2−x nanorods as free radical scavengers for long-term photostability in organic photovoltaics

Single-crystalline CeO2−x hollow nanorods possess more Ce3+ states and wider surface area than other types of cerium oxide nanostructures and those enable the resultant organic photovoltaic cells to have improved photostability.

The pyrolysis behavior and biochar characteristics of Jerusalem artichoke straw with cerium nitrate

The pyrolysis behavior of Jerusalem artichoke straw with cerium nitrate was analyzed by thermogravimetric analyzer coupled with Fourier-transform infrared spectroscopy. Then the cerium oxide doped biochar was obtained from the pyrolysis of Jerusalem artichoke straw impregnated with cerium nitrate. And the electrochemical characteristics and physical structures of the cerium oxide doped biochar from different pyrolysis temperatures were analyzed. TG results showed that the addition of cerium nitrate reduced the reaction energy and pyrolysis temperature, facilitating the pyrolysis reaction. FTIR results revealed that H2O, CO2, CO, CH4, C-O, CO, and aromatic CC were released during the pyrolysis. The cyclic voltammetry curves, galvanostatic charge-discharge curves, and electrochemical impedance spectroscopy curves of the electrode modified with cerium oxide doped biochar indicated that the biochar derived from higher pyrolysis temperature showed a better enhancing effect for electrochemical properties. Nanostructured cerium oxide was observed on the surface rather than in the pores of biochar. The existence of a crystalline structure with a mixture of Ce3+/Ce4+ oxidation states further confirmed the formation of nanostructured cerium oxide. The finding revealed that cerium oxide doped biochar composites showed the potential for a wide application in electrochemistry.

High-performance oxygen evolution reaction activity at low and higher current densities using nanostructured CeO2 and Plasma-assisted Bi@CeO2 electrocatalysts

Herein, pristine nanostructured cerium oxide (CeO2) electrode (HC) was fabricated via an alkali-free hydrothermal, exhibiting high OER behaviors at low current density. The HC electrode displayed a low overpotential of 0.32 V, low Tafel slope of 61.6 mV dec-1, and high stability of 99.6 % for 15 h at a current density of 10 mA cm−2. To accelerate the kinetic of OER at high current density, a binary Bi@CeO2 plasma-activated electrode (PBC) was prepared as an effective electrocatalyst to evolve larger oxygen gas. The PBC electrode exhibited a low overpotential (0.42 V and 0.46 V) at higher current densities of 50 mA cm−2 and 250 mA cm−2, a small Tafel slope of 47.4 mV dec-1, and excellent stability of 99 % for 15 h at a current density of 100 mA cm−2. The results suggested that CeO2 and its composite Bi@CeO2 are promising potential active OER electrocatalysts.

Synthesis and Characterization of Cerium Oxide Nanoparticles and Cerium oxide/silica Nanocomposites by using Adsorption of Dyes from Aqueous Solution

Nanostructured cerium oxide (CeO2) usually identified by way of Nano ceria is an erratic earth metal oxide which plays a technologically significant role owing to its adaptable solicitations by way of automobile finish substances, oxide ion conductors in solid oxide cells, ultraviolet absorbents and glass-polishing materials. Metal oxides are excellent innovative adsorbents aimed at the elimination of dye ingredients. In this study, we describe a nanostructured cerium oxide nanocomposite adsorbent, which displays remarkable efficiency toward the removal of widely used Congo red (CR) from aqueous systems. The CeO2 nanoparticles and CeO2 nanocomposite were prepared by using a simple co-precipitation method. Amongst the numerous approaches, adsorption is a discerning expertise for dye elimination. The cerium oxide nanoparticles solution was presented as a strong activity against E. Coli, a weak activity against Pseudomonas. The cerium oxide nanocomposites (NC) solution was presented as a strong activity against Enterobacter, a weak activity against Staphylococcus. The nanocomposites coating was successfully prepared by the effective dispersing of nanoparticles in cerium and were characterized by X-ray diffraction, Scanning electron microscopy, UV - visible spectroscopy and Fluorescence spectroscopy.

Enhancement of Activity Low-Pt-Content O2-Reduction Catalysts through Formation of Hybrid Systems with Sub-Stoichiometric Cerium Oxide Nanostructures

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, under such condition, O2-reduction reaction (ORR) often proceeds at a less positive potential, and produces higher amounts of undesirable H2O2-intermediate. Recent studies have demonstrated that the rational design of a catalytic system is based on nanostructures of platinum, or carbon-supported platinum (Pt/C), and metal oxide (MOx). By combining the catalytic properties of both components, such hybrid Pt-MOx catalysts are capable of tuning of the activity and durability of Pt. Due to strong interactions of MOx with Pt catalytic nanoparticles leading to the improved activity and durability during ORR, certain nanostructured metal oxides are considered as co-catalysts or active components of supports. The existence of specific interactions between MOx and noble metal (Pt) nanoparticles should improve the stability and activity of the metal catalytic sites due to modification of the Pt electronic structure and diminishing of the oxo (OH) species adsorption on Pt surface, thus promoting centers for the adsorption of oxygen and the cleavage of O=O bonds. The interactions mentioned above would also facilitate dispersion of Pt, inhibit their detachment and further aggregation, and, consequently, prevent or decrease their degradation during the fuel cell operation [1].The catalytic activity of substoichiometric ceria, CeOx (where x < 2) additive results from its unique structure, presence of oxygen vacancies, and other features resulting from the 4f-electronic configuration of cerium. While the oxygen defects are likely to serve as active oxygen adsorption sites, the mixed-valent CeIII/CeIV redox sites should permit the electron shuffling within the lattice of oxygen vacancies and enhancing the ORR activity. The formation of oxygen-defects is accompanied by the localization of electrons left behind in Ce 4f states, thus leading to the formation of CeIII species capable of elongating and reducing the O–O bond strength of the adsorbed O2 molecule; consequently, by increasing the relative ratio of CeIII-to-CeIV, the ORR electrocatalytic activity can be improved [1]. Therefore, in the present study, we consider the intentionally reduced CeOx nanostructured components through subjecting them to high-temperature pretreatment in the presence of argon gas admixed with hydrogen. It is reasonable to expect that, the increased population of CeIII sites on the surfaces of the pretreated ceria particles would stabilize the neighboring active Pt-metal centers, exhibit reductive interactions toward Pt-oxo species, and to improve durability of the catalytic materials. Thus the boundary formed between the Pt-metal and CeOx-metal oxide should facilitate inhibition of the Pt oxide formation by the CeOx layer. Furthermore, our recent studies clearly show that, in the presence of ceria, the oxidative degradation of carbon carriers is also largely decreased. Finally, cerium oxide is known to act as the oxidative scavenger for free radicals such as hydroxyl (HO•) and hydroperoxyl (HOO•), which, once generated, would otherwise lead to the formation of undesirable hydrogen peroxide. Sub-stoichiometric CeOx is capable of rapidly switching between CeIII and CeIV oxidation states, thus inducing the decomposition of both radicals and peroxides. The above observation seems to be very helpful when it comes to designing highly active and durable ORR catalysts containing low platinum loadings.[1] A.Kostuch, I.A. Rutkowska, B. Dembinska, A. Wadas, E. Negro, K. Vezzù, V. Di Noto, P.J. Kulesza, Molecules 26 (2021) 5147. Acknowledgements: This work was supported by the National Science Center (Poland) under Opus Project (2018/29/B/ST5/02627) and under auspices of the European Union EIT Raw Materials ALPE 19247 Project (Specific Grant Agreement No. EIT/RAW MATERIALS/SGA2020/1).

Transdermal permeation of inorganic cerium salts in intact human skin

The stratum corneum protects the body against external agents, such as metals, chemicals, and toxics. Although it is considered poorly permeable to them, comprising the major barrier to the permeation of such substances, it may become a relevant gate of entry for such molecules. Cerium (Ce) is a lanthanide that is widely used in catalytic, energy, biological and medicinal applications, owing to its intrinsic structural and unique redox properties. Cerium salts used to produce cerium oxide (CeO2) nanostructures can potentially come into contact with the skin and be absorbed following dermal exposure. The objective of this study was to investigate the percutaneous absorption of three inorganic Ce salts: cerium (III) chloride (CeCl3); cerium (III) nitrate (Ce(NO3)3) and ammonium cerium (IV) nitrate (Ce(NH4)2(NO3)6), which are commonly adopted for the synthesis of CeO2 using in vitro - ex vivo technique in Franz diffusion cells. The present work shows that Ce salts cannot permeate intact human skin, but they can penetrate significantly in the epidermis (up to 0.29 μg/cm2) and, to a lesser extent in dermis (up to 0.11 μg/cm2). Further studies are required to evaluate the potential effects of long-term exposure to Ce.

Cerium oxide nanostructures: properties, biomedical applications and surface coatings.

Cerium oxide nanoparticles have significantly improved catalytic properties and are of increasing interest in the nanoparticle research field hence the current trends in cerium oxide nanoparticles are reviewed here. Unlike previous reviews which have focused primarily on the biosynthesis of cerium oxide nanoparticles, their properties, and applications, this review will focus on the unique physical, chemical, and biological properties of cerium oxide nanoparticles, the role of oxygen vacancies or defects in the lattice structure, the ratio of oxidation states in determining their catalytic properties and applications in biosensing, drug or gene delivery, etc. have been discussed. Furthermore, the limitations of the bare form of cerium oxide nanoparticles and the advances in the field of surface coating by different ligands to overcome the issues of bare nanoparticles have been discussed. The review concludes with a discussion on the environmental aspects and toxicity of cerium oxide nanoparticles and their potential future in practical applications.

Sunlight-assisted synthesis of cerium (IV) oxide nanostructure with enhanced photocatalytic activity

In this work, cerium oxide (CeO2) nanostructures have been synthesized using a sunlight-assisted combustion method from cerium nitrate hexahydrate and glycine as precursors. The synthesized sunlight-assisted cerium oxide (CeO2-SA) nanopowder has been characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscope, UV–Visible spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and Nitrogen adsorption–desorption isotherm. In this method of synthesis, natural sunlight is used as energy source to ignite the reaction and the product is obtained immediately. The synthesized CeO2-SA has a fluorite-like cubic crystal structure and spongy morphology with irregular pores. It is also found that CeO2-SA possesses a smaller particle size, narrower band gap and lower recombination rate than bulk CeO2. The crystalline size of CeO2-SA nanoparticles was obtained to be 4.9 nm. The optical band gap for CeO2-SA was found to be 2.98 eV. The BET Surface area for CeO2-SA was found to be 19.7 m2/g which is 5.3 times greater than the surface area of bulk CeO2 (3.7 m2/g). Around 91% degradation of methylene blue dye (MB) is observed. Therefore, CeO2-SA exhibits higher photocatalytic efficiency towards the degradation of MB than bulk CeO2.

Evaluation of size, shape, and charge effect on the biological interaction and cellular uptake of cerium oxide nanostructures

Cerium oxide (CeO2) at the nanoscale has prolifically attracted the immense interest of researchers due to its switchable oxidation states (Ce3+/Ce4+) that play a crucial role in many biological activities. The present work reports the evaluation of size, shape, and charge effect on the biological interaction with RAW 264.7 cells for three nanostructures of CeO2 (CeO2 NS) namely nanocubes (NCs), nanorods (NRs), and nanoparticles (NPs). These NS exhibits similar composition and have average diameter values in the order of NCs < NRs ≅ NPs. The values of zeta potential revealed the anionic nature of NS with surface charge in order of NCs < NPs < NRs. The cellular interaction of CeO2 NS was analyzed for cytotoxicity, cellular uptake, and morphological studies. Quantitative determination of the uptake of CeO2 NS exhibited concentration-dependent uptake in the order as NCs > NPs > NRs. The proposed possible mechanisms of cellular uptake revealed that different structures tended to use the various endocytosis pathways in different proportions.