Assessment of heavy oil recovery mechanisms using in-situ synthesized CeO2 nanoparticles

This project investigated the impact of low-temperature, in-situ synthesis of cerium oxide (CeO2) nanoparticles on various aspects of oil recovery mechanisms, including changes in oil viscosity, alterations in reservoir rock wettability, and the resulting oil recovery factor. The nanoparticles were synthesized using a microemulsion procedure and subjected to various characterization analyses. Subsequently, these synthesized nanoparticles were prepared and injected into a glass micromodel, both in-situ and ex-situ, to evaluate their effectiveness. The study also examined the movement of the injected fluid within the porous media. The results revealed that the synthesized CeO2 nanoparticles exhibited a remarkable capability at low temperatures to reduce crude oil viscosity by 28% and to lighten the oil. Furthermore, the addition of CeO2 nanoparticles to the base fluid (water) led to a shift in the wettability of the porous medium, resulting in a significant reduction in the oil drop angle from 140° to 20°. Even a minimal presence of CeO2 nanoparticles (0.1 wt%) in water increased the oil production factor from 29 to 42%. This enhancement became even more pronounced at a concentration of 0.5 wt%, where the oil production factor reached 56%. Finally, it was found that the in-situ injection, involving the direct synthesis of CeO2 nanoparticles within the reservoir using precursor salts solution and reservoir energy, led to an 11% enhancement in oil production efficiency compared to the ex-situ injection scenario, where the nanofluid is prepared outside the reservoir and then injected into it.

Erythrocyte-Like Mesoporous PDA@CeO2 Nanozyme with Dual Drugs for Periodontitis Treatment

Periodontitis is a chronic oral inflammatory disease with the characteristic of excess oxidative stress in the inflammatory site, dramatically decreasing the quality of life. Studies show that nanozymes can be ideal candidates for ROS scavenging in periodontitis. Here, we design a multipath anti-inflammatory mesoporous polydopamine@cerium oxide nanobowl (mPDA@CeO2 NB) with multienzyme mimicking properties, which combines the advantages of both CeO2 NP and mPDA NB for synergistically eliminating reactive oxygen species (ROS), including hydroxyl radical (•OH), hydrogen peroxide (H2O2), and superoxide (O2•-). Besides, the erythrocyte-like structure of mNBs makes them a facility for cell uptake, and the mesopores can load both hydrophobic and hydrophilic drugs for combined anti-inflammatory therapy. In vitro and in vivo experiments prove that the combination of CeO2 and mPDA can synergistically achieve multiple complementary ROS eliminations and suppression of ROS-induced inflammation. Moreover, the ROS regulation plus anti-inflammatory drugs in one mPDA@CeO2 NB prevents the progression of periodontitis in a mouse model. Therefore, the design of mPDA@CeO2 NB with these excellent properties provides a therapeutic strategy for inflammatory diseases.

Differential genomic effects of four nano-sized and one micro-sized CeO2 particles on HepG2 cells

The objective of this research was to perform a genomics study of five cerium oxide particles, 4 nano and one micrometer-sized particles which have been studied previously by our group with respect to cytotoxicity, biochemistry and metabolomics. Human liver carcinoma HepG2 cells were exposed to between 0.3 to 300 ug/ml of CeO2 particles for 72 hours and then total RNA was harvested. Fatty acid accumulation was observed with W4, X5, Z7 and less with Q but not Y6. The gene expression changes in the fatty acid metabolism genes correlated the fatty acid accumulation we detected in the prior metabolomics study for the CeO2 particles named W4, Y6, Z7 and Q, but not for X5. In particular, the observed genomics effects on fatty acid uptake and fatty acid oxidation offer a possible explanation of why many CeO2 particles increase cellular free fatty acid concentrations in HepG2 cells. The major genomic changes observed in this study were sirtuin, ubiquitination signaling pathways, NRF2-mediated stress response and mitochondrial dysfunction. The sirtuin pathway was affected by many CeO2 particle treatments. Sirtuin signaling itself is sensitive to oxidative stress state of the cells and may be an important contributor in CeO2 particle induced fatty acid accumulation. Ubiquitination pathway regulates many protein functions in the cells, including sirtuin signaling, NRF2 mediated stress, and mitochondrial dysfunction pathways. NRF2-mediated stress response and mitochondrial were reported to be altered in many nanoparticles treated cells. All these pathways may contribute to the fatty acid accumulation in the CeO2 particle treated cells.

Interaction of Cerium Oxide Nanoparticles and Ionic Cerium with Duckweed (Lemna minor L.): Uptake, Distribution, and Phytotoxicity

As one of the most widely used nanomaterials, CeO2 nanoparticles (NPs) might be released into the aquatic environment. In this paper, the interaction of CeO2 NPs and Ce3+ ions (0~10 mg/L) with duckweed (Lemna minor L.) was investigated. CeO2 NPs significantly inhibited the root elongation of duckweed at concentrations higher than 0.1 mg/L, while the inhibition threshold of Ce3+ ions was 0.02 mg/L. At high doses, both reduced photosynthetic pigment contents led to cell death and induced stomatal deformation, but the toxicity of Ce3+ ions was greater than that of CeO2 NPs at the same concentration. According to the in situ distribution of Ce in plant tissues by μ-XRF, the intensity of Ce signal was in the order of root > old frond > new frond, suggesting that roots play a major role in the uptake of Ce. The result of XANES showed that 27.6% of Ce(IV) was reduced to Ce(III) in duckweed treated with CeO2 NPs. We speculated that the toxicity of CeO2 NPs to duckweed was mainly due to its high sensitivity to the released Ce3+ ions. To our knowledge, this is the first study on the toxicity of CeO2 NPs to an aquatic higher plant.

Instantaneous Free Radical Scavenging by CeO2 Nanoparticles Adjacent to the Fe-N4 Active Sites for Durable Fuel Cells

To achieve the Fe-N-C materials with both high activity and durability in proton exchange membrane fuel cells, the attack of free radicals on Fe-N4 sites must be overcome. Herein, we report a strategy to effectively eliminate radicals at the source to mitigate the degradation by anchoring CeO2 nanoparticles as radicals scavengers adjacent (Scaad-CeO2 ) to the Fe-N4 sites. Radicals such as ⋅OH and HO2 ⋅ that form at Fe-N4 sites can be instantaneously eliminated by adjacent CeO2 , which shortens the survival time of radicals and the regional space of their damage. As a result, the CeO2 scavengers in Fe-NC/Scaad-CeO2 achieved ∼80 % elimination of the radicals generated at the Fe-N4 sites. A fuel cell prepared with the Fe-NC/Scaad-CeO2 showed a smaller peak power density decay after 30,000 cycles determined with US DOE PGM-relevant AST, increasing the decay of Fe-NCPhen from 69 % to 28 % decay.

Nanoceria as Safe Contrast Agents for X-ray CT Imaging

Cerium oxide nanoparticles (CeO2NPs) have exceptional catalytic properties, rendering them highly effective in removing excessive reactive oxygen species (ROS) from biological environments, which is crucial in safeguarding these environments against radiation-induced damage. Additionally, the Ce atom's high Z number makes it an ideal candidate for utilisation as an X-ray imaging contrast agent. We herein show how the injection of albumin-stabilised 5 nm CeO2NPs into mice revealed substantial enhancement in X-ray contrast, reaching up to a tenfold increase at significantly lower concentrations than commercial or other proposed contrast agents. Remarkably, these NPs exhibited prolonged residence time within the target organs. Thus, upon injection into the tail vein, they exhibited efficient uptake by the liver and spleen, with 85% of the injected dose (%ID) recovered after 7 days. In the case of intratumoral administration, 99% ID of CeO2NPs remained within the tumour throughout the 7-day observation period, allowing for observation of disease dynamics. Mass spectrometry (ICP-MS) elemental analysis confirmed X-ray CT imaging observations.

Fabrication of polydopamine decorated carbon cloth as support material to anchor CeO2 nanoparticles for electrochemical detection of ethanol

A flexible CeO₂ nanostructured polydopamine-modified carbon cloth (CeO₂/PDA/CC) interface was fabricated via electrodeposition for ethanol detection. The fabrication method involved two consecutive electrochemical steps in which dopamine was firstly electrodeposited on carbon fibers, followed by the electrochemical growth of CeO₂ nanoparticles. The CeO₂/PDA-based electroactive interface exerts an impressive electrochemical performance on the flexible sensor due to strong synergistic effect of the PDA functionalization with more active sites. Moreover, catalytic activity of CeO₂ nanostructures anchored on highly conductive CC incorporate superior electrocatalytic performance of the fabricated interface. The designed electrochemical sensor showed a wide response to ethanol in the linear range 1 to 25 mM with a detection limit of 0.22 mM. The CeO₂/PDA/CC flexible sensor showed good anti-interference ability and excellent repeatability and reproducibility (RSD = 1.67%). The fabricated interface performed well in saliva samples with satisfactory recoveries, corroborating the viability of CeO₂/PDA/CC integrated interface for practical implementation.

Nanozyme-based dual-signal sensing system for colorimetric and photothermal detection of AChE activity in the blood of liver-injured mice

Acetylcholinesterase (AChE), a crucial enzyme related to liver function, is involved in numerous physiological processes such as neurotransmission and muscular contraction. The currently reported techniques for detecting AChE mainly rely on a single signal output, limiting their high-accuracy quantification. The few reported dual-signal assays are challenging to implement in dual-signal point-of-care testing (POCT) because of the need for large instruments, costly modifications, and trained operators. Herein, we report a colorimetric and photothermal dual-signal POCT sensing platform based on CeO₂-TMB (3,3',5,5'-tetramethylbenzidine) for the visualization of AChE activity in liver-injured mice. The method compensates for the false positives of a single signal and realizes the rapid, low-cost portable detection of AChE. More importantly, the CeO₂-TMB sensing platform enables the diagnosis of liver injury and provides an effective tool for studying liver disease in basic medicine and clinical applications. Rapid colorimetric and photothermal biosensor for sensitive detection of acetylcholinesterase (I) and acetylcholinesterase levels in mouse serum (II).

CeO2 Nanoparticles-Regulated Plasmid Uptake and Bioavailability for Reducing Transformation of Extracellular Antibiotic Resistance Genes

The direct uptake of extracellular DNA (eDNA) via transformation facilitates the dissemination of antibiotic resistance genes (ARGs) in the environment. CeO₂ nanoparticles (NPs) have potential in the regulation of conjugation-dominated ARGs propagation, whereas their effects on ARGs transformation remain largely unknown. Here, CeO₂ NPs at concentrations lower than 50 mg L^-1 have been applied to regulate the transformation of plasmid-borne ARGs to competent Escherichia coli (E. coli) cells. Three types of exposure systems were established to optimize the regulation efficiency. Pre-incubation of competent E. coli cells with CeO₂ NPs at 0.5 mg L^-1 inhibited the transformation (35.4%) by reducing the ROS content (0.9-fold) and cell membrane permeability (0.9-fold), thereby down-regulating the expression of genes related to DNA uptake and processing (bhsA, ybaV, and nfsB, 0.7-0.8 folds). Importantly, CeO₂ NPs exhibited an excellent binding capacity with the plasmids, decreasing the amounts of plasmids available for cellular uptake and down-regulating the gene expression of DNA uptake (bhsA, ybaV, and recJ, 0.6-0.7 folds). Altogether, pre-exposure of plasmids with CeO₂ NPs (10 and 25 mg L^-1) suppressed the transformation with an efficiency of 44.5-51.6%. This study provides a nano-strategy for controlling the transformation of ARGs, improving our understanding on the mechanisms of nanomaterial-mediated ARGs propagation.

Cerium oxide: synthesis, brief characterization, and optimization of the photocatalytic activity against phenazopyridine in an aqueous solution

Water pollution by antibiotics is a global crisis, and its risk is critically more severe due to the explosive use of these drug compounds. A critical effective removal method to diminish this risk is heterogeneous photocatalysis and optimizing the conditions to reach higher mineralization efficiency. CeO₂ anoparticles (NPs) were synthesized and characterized by X-ray diffraction (XRD), UV-Vis diffuse reflection spectroscopy (DRS), and Fourier transform infrared spectroscopy (FTIR) techniques. A cubic structural crystallite phase was detected that had crystallite sizes of 17.9 and 16.7 nm estimated by the Scherrer and Williamson-Hall models. A typical FTIR absorption band for the Ce-O stretching absorption has appeared at 554 cm^-1. Based on DRS data and the Kubelka-Munk and Tauc models, Eg values of 2.80, 3.06, 3.12, and 3.13 eV were obtained for n-values of 1/2, 2, 3/2, and 3, respectively. pHpzc of CeO₂ NPs was about 5.7. The direct photolysis and surface adsorption processes have no critical role in phenazopyridine (PP) removal by appearing with 2.7 and 6.7% removal efficiencies, respectively. Due to the highest photocatalytic activity of CeO₂ NPs toward PP, the effects of the critical operating variable on the activity were evaluated, and the optimal conditions were as catalyst dose, 0.7 g/L; pH, 6; irradiation time, 90 min; and C_PP, 20 ppm. The Hinshelwood kinetics equation plot was y =  - 6.6442 - 0.4677x (r² = 0.9296), in which its slope as the rate constant of the photodegradation process was 0.4677 min^-1 (corresponding to a t_1/2 value of 1.48 min).

Biosynthesis of phyto functionalized cerium oxide nanoparticles mediated from Scoparia dulsis L. for appraisal of anti-cancer potential against adenocarcinomic lung cancer cells and paracetamol sensing potentiality

This research work aims at the eco-friendly preparation of cerium oxide nanoparticles (CeSD NPs) utilizing the natural extract of Scoparia dulsis L. An attempt was made to analyze the influence of the fuel load on the size, shape, and optical properties of the nanoparticles. The p-XRD studies revealed the controlled formation of NPs with a size not more than 12.74 nm. The surface area studies appraise the mesoporous nature of the synthesized ceria particles, with the maximum specific surface area of 36.06 m²g^-1. The nano-regime CeO₂ nanoparticles had a definite impact on biomedical and electrochemical studies. The CeSD NPs with minuscule size (10.69 nm) manifested promising antioxidant and human RBC protection activity. The antioxidant properties were evaluated using % DPPH inhibition with of maximum of 83.38. The stabilization of RBC's by CeSD NPs was maximum at 94.97%. However, the CeSD NPs with apparent size (12.74 nm) that utilized greater volume fuel (25 mL) had noticeable results on adenocarcinomic lung (A549) cancer cell viability and antidiabetic study which was maximum of 70.16% at concentration 500 μg/mL. A satisfactory antibacterial application was proffered against chosen bacterial stains. The smallest size CeO₂ NPs exhibited the best proton diffusion coefficient (8.16 × 10^-6 cm²s^-1), and the capacitance values of the CeSD NPs are near in all samples (~ 1.17 to 2.00 F) manifest their compact nano-regime sizes. The paracetamol drug was chosen as analyte to appreciating the superlative efficiency for sensing paracetamol drug with the lowest detection limit.

CeO2 nanoparticles improve prooxidant/antioxidant balance, life quality and survival of old male rats

Due to its unique redox chemistry, nanoceria is considered as potent free radical scavenger and antioxidant. However, their protective capacity in aging organisms remains controversial. To detect the anti-aging effects associated with the redox activity of 2 and 10 nm nano-CeO2, different test systems were used, including in vitro analysis, in situ assay of mitochondria function and in vivo studies of suitable nano-CeO₂ on aging of male Wistar rats from 22 months-old to the end of life. The 2 nm nanoparticles exhibited not only antioxidant (^·OH scavenging; chemiluminescence assay; decomposition of H₂O₂, phosphatidylcholine autooxidation) but also prooxidant properties (reduced glutathione and reduced nicotinamide adenine dinucleotide phosphate oxidation) as well as affected mitochondria whereas in most test systems 10 nm nano-CeO₂ showed less activity or was inert. Prolonged use of the more redox active 2 nm nano-CeO₂ (0.25-0.3 mg/kg/day) in vivo with drinking water resulted in improvement in physiological parameters and normalization of the prooxidant/antioxidant balance in liver and blood of aging animals. Survival analysis using Kaplan-Meier curve and Gehan tests with Yates' correction showed that by the time the prooxidant-antioxidant balance was assessed (32 months), survival rates exceeded the control values most considerably. The apparent median survival for the control rats was 900 days, and for the experimental rats-960 days. In general, the data obtained indicate the ability of extra-small 2 nm nano-CeO2 to improve quality of life and increase the survival rate of an aging organism.

Fabrication of CeO2/GCE for Electrochemical Sensing of Hydroquinone

Hydroquinone is a widely used derivative of phenol which has a negative influence on human beings and the environment. The determination of the accurate amount of hydroquinone is of great importance. Recently, the fabrication of an electrochemical sensing device has received enormous attention. In this study, we reported on the facile synthesis of cerium dioxide (CeO₂) nanoparticles (NPs). The CeO₂ NPs were synthesized using cerium nitrate hexahydrate as a precursor. For determining the physicochemical properties of synthesized CeO₂ NPs, various advanced techniques, viz., powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), were studied. Further, these synthesized CeO₂ NPs were used for the modification of a glassy carbon electrode (CeO₂/GCE), which was utilized for the sensing of hydroquinone (HQ). A decent detection limit of 0.9 µM with a sensitivity of 0.41 µA/µM cm² was exhibited by the modified electrode (CeO₂/GCE). The CeO₂/GCE also exhibited good stability, selectivity, and repeatability towards the determination of HQ.

Exploring the Influence of Synthesis Parameters on the Optical Properties for Various CeO2 NPs

Cerium oxide (CeO₂) nanoparticles were synthesized with a chemical precipitation method in different experimental conditions using cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) as a precursor, modifying the solution pH, the reaction time, and Co atoms as dopants, in order to tune the band gap energy values of the prepared samples. The physical characteristics of the synthesized ceria nanoparticles were evaluated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis analyses and photoluminescence measurements. XRD data revealed a pure cubic fluorite structure of CeO₂ NPs, the estimation of crystallite sizes by Scherrer’s formula indicates the formation of crystals with dimensions between 11.24 and 21.65 nm. All samples contain nearly spherical CeO₂ nanoparticles, as well as cubic, rhomboidal, triangular, or polyhedral nanoparticles that can be identified by TEM images. The optical investigation of CeO₂ samples revealed that the band gap energy values are between 3.18 eV and 2.85 eV, and, after doping with Co atoms, the E_g of samples decreased to about 2.0 eV. In this study, we managed to obtain CeO₂ NPs with E_g under 3.0 eV by only modifying the synthesis parameters. In addition, by doping with Co ions, the band gap energy value was lowered to 2.0 eV. This aspect leads to promising results that provide an encouraging approach for future photocatalytic investigations.

Synthesis of rod-like CeO2 nanoparticles and their application to catalyze the luminal-O2 chemiluminescence reaction used in the determination of oxcarbazepine and ascorbic acid

Rod-like CeO₂ nanoparticles (NPs) were produced by the quick precipitation approach and employed as a catalyzer to increase the chemiluminescence (CL) intensity of the luminol-O₂ reaction. The transmission electron microscopy (TEM) images of the CeO₂ NPs showed that rod-like particles with the length and diameter about 15 nm and 5 nm, respectively, were produced. Furthermore, pharmaceuticals including oxcarbazepine (OXP) and ascorbic acid (AA) showed an inhibitory effect against the CL intensity such that the more concentration of the pharmaceuticals, the less was the CL intensity. Therefore, the new CeO₂ NPs-luminol-O₂ CL reaction was developed to determine OXP and AA in the pharmaceutical formulations. It is the first CL method established for the quantification of OXP. The linear dynamic range of this method for OXP was from 6.0 × 10^-7 to 6.0 × 10^-5 mol L^-1 and for AA from 1.0 × 10^-6 to 1.0 × 10^-4 mol L^-1.

Cerium oxide nanoparticles loaded nanofibrous membranes promote bone regeneration for periodontal tissue engineering

Bone regeneration is a crucial part in the treatment of periodontal tissue regeneration, in which new attempts come out along with the development of nanomaterials. Herein, the effect of cerium oxide nanoparticles (CeO2 NPs) on the cell behavior and function of human periodontal ligament stem cells (hPDLSCs) was investigated. Results of CCK-8 and cell cycle tests demonstrated that CeO2 NPs not only had good biocompatibility, but also promoted cell proliferation. Furthermore, the levels of alkaline phosphatase activity, mineralized nodule formation and expressions of osteogenic genes and proteins demonstrated CeO2 NPs could promote osteogenesis differentiation of hPDLSCs. Then we chose electrospinning to fabricate fibrous membranes containing CeO2 NPs. We showed that the composite membranes improved mechanical properties as well as realized release of CeO2 NPs. We then applied the composite membranes to in vivo study in rat cranial defect models. Micro-CT and histopathological evaluations revealed that nanofibrous membranes with CeO2 NPs further accelerated new bone formation. Those exciting results demonstrated that CeO2 NPs and porous membrane contributed to osteogenic ability, and CeO2 NPs contained electrospun membrane may be a promising candidate material for periodontal bone regeneration.

High-performance SOD mimetic enzyme Au@Ce for arresting cell cycle and proliferation of acute myeloid leukemia

SOD-like activity of CeO₂ nanoparticles (Ce NPs) is driven by Ce³⁺/Ce⁴⁺, high oxidative stress can oxidize Ce³⁺ to reduce the ratio of Ce³⁺/Ce⁴⁺, inactivating the SOD activity of Ce NPs. Herein, we found Au@Ce NPs, assembled by Au NPs and Ce NPs, exhibited high-performance of SOD mimetic enzyme activity even upon the oxidation of H₂O₂. Ce NPs supported by nano-Au can acquire the electrons from Au NPs through the enhanced localized surface plasmon resonance (LSPR), maintaining the stability of Ce³⁺/Ce⁴⁺ and SOD-like activity. Meanwhile, Au@Ce NPs retained the peroxidase function and catalase function. As a result, Au@Ce NPs effectively scavenged O₂•- and the derived ROS in AML cells, which are the important signaling source that drives AML cell proliferation and accelerates cell cycle progression. When HL-60 cells were treated by Au@Ce NPs, the removal of endogenous ROS signal significantly arrested cell cycle at G1 phase and suppressed the cell proliferation by blocking the mitogen-activated protein kinases (MAPKs) signaling and the Akt/Cyclin D1 cell cycle signaling. Importantly, this treatment strategy showed therapeutic effect for subcutaneous transplantation of AML model as well as a satisfactory result in diminishing the leukocyte infiltration of liver and spleen particularly. Thus, assembled Au@Ce NPs show the high-performance SOD-like activity, promising the potential in treating AML and regulating abnormal ROS in other diseases safely and efficiently.

•

Assembled Au@Ce NPs exhibited multi-enzyme activity and the high-performance SOD-like activity even upon the oxidation of H₂O₂.

•

In the assembled Au@Ce NPs, Ce NPs can acquire the electrons from Au NPs to maintain the stability of Ce³⁺/Ce⁴⁺ and SOD activity.

•

Au@Ce can scavenge O₂•- and the derived ROS in AML cells to arrest cell cycle signal and proliferation signal.

•

Au@Ce treatment suppressed the growth of HL-60 bearing tumors and prolonged the survival time in systemic AML mice.

Salivary Leucocytes as In Vitro Model to Evaluate Nanoparticle-Induced DNA Damage

Metal oxide nanoparticles (NPs) have a wide variety of applications in many consumer products and biomedical practices. As a result, human exposure to these nanomaterials is highly frequent, becoming an issue of concern to public health. Recently, human salivary leucocytes have been proposed as an adequate non-invasive alternative to peripheral blood leucocytes to evaluate genotoxicity in vitro. The present study focused on proving the suitability of salivary leucocytes as a biomatrix in the comet assay for in vitro nanogenotoxicity studies, by testing some of the metal oxide NPs most frequently present in consumer products, namely, titanium dioxide (TiO2), zinc oxide (ZnO), and cerium dioxide (CeO2) NPs. Primary and oxidative DNA damage were evaluated by alkaline and hOGG1-modified comet assay, respectively. Any possible interference of the NPs with the methodological procedure or the hOGG1 activity was addressed before performing genotoxicity evaluation. Results obtained showed an increase of both primary and oxidative damage after NPs treatments. These data support the use of salivary leucocytes as a proper and sensitive biological sample for in vitro nanogenotoxicity studies, and contribute to increase the knowledge on the impact of metal oxide NPs on human health, reinforcing the need for a specific regulation of the nanomaterials use.

Growing Rice (Oryza sativa) Aerobically Reduces Phytotoxicity, Uptake, and Transformation of CeO2 Nanoparticles

This study compared the impact and uptake of root-administered CeO₂ nanoparticles (NPs) in rice growing under flooded and aerobic soil conditions, which are two water regimes commonly used for rice cultivation. CeO₂ NPs at 100 mg/kg improved photosynthesis and plant growth by reducing the oxidative damage and enhancing plant tolerance to stress, while a higher concentration (500 mg/kg) of CeO₂ NPs negatively affected plant growth. More significant effects were observed under the flooded condition than under the aerobic condition. CeO₂ NPs of 100 and 500 mg/kg resulted in 78% and 70% higher accumulation of Ce in shoots under the flooded condition compared to the aerobic condition. CeO₂ NPs partially transformed to Ce(III) species in soils and plants under both conditions. A higher extent of transformation under the flooded condition, which was partly attributed to the lower soil pH and redox potential under the flooded condition, leads to higher plant uptake of Ce. A higher extent of transformation in rhizosphere soil was observed. A higher plant transpiration rate (TR) under flooded conditions resulted in a higher accumulation of CeO₂ species in shoots. This study, for the first time, reported that water regimes influenced the biotransformation of CeO₂ NPs and their uptake and impact in rice plants.

Synthesis, Optical, Chemical and Thermal Characterizations of PMMA-PS/CeO2 Nanoparticles Thin Film

We report the synthesis of hybrid thin films based on polymethyl methacrylate) (PMMA) and polystyrene (PS) doped with 1%, 3%, 5%, and 7% of cerium dioxide nanoparticles (CeO2 NPs). The As-prepared thin films of (PMMA-PS) incorporated with CeO2 NPs are deposited on a glass substrate. The transmittance T% (λ) and reflectance R% (λ) of PMMA-PS/CeO2 NPs thin films are measured at room temperature in the spectral range (250-700) nm. High transmittance of 87% is observed in the low-energy regions. However, transmittance decreases sharply to a vanishing value in the high-energy region. In addition, as the CeO2 NPs concentration is increased, a red shift of the absorption edge is clearly observed suggesting a considerable decrease in the band gap energy of PMMA-PS/CeO2 NPs thin film. The optical constants (n and k) and related key optical and optoelectronic parameters of PMMA-PS/Ce NPs thin films are reported and interpreted. Furthermore, Tauc and Urbach models are employed to elucidate optical behavior and calculate the band gaps of the as-synthesized nanocomposite thin films. The optical band gap energy of PMMA-PS thin film is found to be 4.03 eV. Optical band gap engineering is found to be possible upon introducing CeO2 NPs into PMMA-PS polymeric thin films as demonstrated clearly by the continuous decrease of optical band gap upon increasing CeO2 content. Fourier-transform infrared spectroscopy (FTIR) analysis is conducted to identify the major vibrational modes of the nanocomposite. The peak at 541.42 cm-1 is assigned to Ce-O and indicates the incorporation of CeO2 NPs into the copolymers matrices. There were drastic changes to the width and intensity of the vibrational bands of PMMA-PS upon addition of CeO2 NPs. To examine the chemical and thermal stability, thermogravimetric (TGA) thermograms are measured. We found that (PMMA-PVA)/CeO2 NPs nanocomposite thin films are thermally stable below 110 °C. Therefore, they could be key candidate materials for a wide range of scaled multifunctional smart optical and optoelectronic devices.

Assessing the Effect of CeO2 Nanoparticles as Corrosion Inhibitor in Hybrid Biobased Waterborne Acrylic Direct to Metal Coating Binders

CeO₂ nanoparticles were incorporated in waterborne binders containing high biobased content (up to 70%) in order to analyze the anticorrosion performance for direct to metal coatings. Biobased binders were synthesized by batch miniemulsion polymerization of 2-octyl acrylate and isobornyl methacrylate monomers using a phosphate polymerizable surfactant (Sipomer PAM200) that lead to the formation of phosphate functionalized latexes. Upon the direct application of such binders on steel, the functionalized polymer particles were able to interact with steel, creating a thin phosphatization layer between the metal and the polymer and avoiding flash rust. The in situ incorporation of the CeO₂ nanoparticles during the polymerization process led to their homogeneous distribution in the final polymer film, which produced outstanding anticorrosion performance according to the Electrochemical Impedance Spectroscopy measurements. In fact, steel substrates coated with the hybrid polymer film (30-40 µm thick) showed high barrier corrosion resistance after 41 days (~1000 h) of immersion in NaCl water solution and active inhibition capabilities thanks to the presence of the CeO₂ nanoparticles. This work opens the door to the fabrication of sustainable hybrid anticorrosion waterborne coatings.

Photocatalytic degradation of organic pollutants using Trianthema Portulastrum leaf extract based CeO2 nanoparticles

Comparison of bio CeO2-Nps prepared using Trianthema Portulastrum leaf extract with chemical CeO2-Nps is of interest. The ultraviolet - visible, x-ray diffraction, HR - TEM, FT - IR, and photoluminescence studies were conducted with CeO2-Nps. UV-Maximum absorptionat 292 nm was completed using UV-visible spectrum. The HR-TEM images showed 38 nm bio CeO2-Nps with spherical morphology. This showed the polycrystalline character of CeO2-Nps similar to XRD data. The presence of metal oxide is confirmed by FT - IR analyses. The CeO2-Nps showed the potential photocatalytic activity for Acid black 1 color degradation after exposure to sunlight. Chem and bio CeO2-Nps have a degradation rate of 86.66 and 94.33%, respectively for acid black 1 dye. The synthesized CeO2-Nps are also evaluated for antibacterial and antioxidant activity. The bio CeO2-Nps has antibacterial activity for Pseudomonas aeruginosa (17 ± 0.56 mm) and Staphylococcus aureus (16 ± 0.24 mm) at low concentrations of 100 µl. The CeO2-Nps bio showed high inhibition of radical DPPH IC50 µg/ml, at 95.17 ± 21. Thus, we show that CeO2-Nps have environmentally friendly properties that are useful for dye degradation with antimicrobial and antioxidant activities.

Electrochemical assays for determination of H2O2 and prostate-specific antigen based on a nanocomposite consisting of CeO2 nanoparticle-decorated MnO2 nanospheres

A nanocomposite consisting of CeO₂ nanoparticle-decorated MnO₂ nanospheres (CeO₂@MnO₂) was synthesized for the first time via a hydrothermal method. CeO₂@MnO₂ was exploited to construct an electrochemical assays for detecting H₂O₂ and prostate-specific antigen (PSA) with square wave voltammetry (SWV). The electrochemical results proved that CeO₂@MnO₂ owned a better electrocatalytic effect towards H₂O₂ reduction than pure MnO₂ NS and CeO₂ NP due to the synergistic effect between MnO₂ NS and CeO₂ NP. Under optimized conditions, CeO₂@MnO₂-based assay can be applied to detect H₂O₂ in the range 1 to 3.0 × 10³ μmol L^-1. The label-free electrochemical immunoassay based on CeO₂@MnO₂ displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL^-1. The electrochemical assays also possessed acceptable sensitivity, selectivity, and stability. The study showed that CeO₂@MnO₂ hold great potential as a biosensing platform and the clinical determination of tumor markers in human serum. Graphical abstract A nanocomposite consisting of CeO₂ nanoparticles decorated MnO₂ nanospheres (CeO₂ @MnO₂) was firstly synthesized via a hydrothermal method. CeO₂@MnO₂ was firstly exploited to construct electrochemical assays for detecting H2O₂ and prostate-specific antigen (PSA) with square wave voltammetry (SWV), respectively. The electrochemical results proved that CeO₂@MnO₂ owned better electrocatalysis towards H₂O₂ reduction than pure MnO₂ NS and CeO₂ NP due to the synergistic effect between MnO₂ NS and CeO₂ NP. Under optimized conditions, CeO₂@MnO₂ based assay relative to the H₂O₂ system can be applied to detect H₂O₂ with range from 1 to 3.0 × 10³ μmol L^-1. The label-free electrochemical immunoassay based on CeO₂@MnO₂ relative to the H₂O₂ system displayed linearly with concentrations of PSA from 0.005 to 50.0 ng mL^-1. The electrochemical assays also possessed acceptable sensitivity, selectivity and stability. The study showed that CeO₂@MnO₂ hold great potential for biosensing platform and the clinic determination of tumor markers in human serum.

Effects of CeO2 Nanoparticles on Microcystis aeruginosa Growth and Microcystin Production

The interaction between metal oxide nanoparticles and toxin-producing cyanobacteria is relatively unknown. The present work exposed Microcystis sp.7806 to different concentrations of cerium oxide nanoparticles (CeO₂ NPs) (1 mg/L, 10 mg/L and 50 mg/L), and evaluated the growth, photosynthetic activity, reactive oxygen species level, and the extra-(intra-) cellular microcystin-LR (MC-LR) contents. The particle size, zeta potential and cerium ions released into the medium were analyzed. Results showed 10 mg/L NP treatment promoted algae growth but slightly inhibited the photosynthetic yield of algae, and the 50 mg/L treatment reduced algae biomass. The algal cells remarkably responded to oxidative stress at higher concentrations (10 mg/L and 50 mg/L). CeO₂ NPs largely increased the intracellular MC-LR content at 50 mg/L, and significantly reduced the extracellular MC-LR content at any concentration. This demonstrates CeO₂ NPs may pose an ecological risk potential during harmful algal blooms by stimulating toxin production.

Effect of CeO2 Nanoparticles on Interface of Cu/Al2O3 Ceramic Clad Composites

Cu/Al₂O₃ ceramic clad composites are widely used in electronic packaging and electrical contacts. However, the conductivity and strength of the interfacial layer are not fit for the demands. So CeO₂ nanoparticles 24.3 nm in size, coated on Al₂O₃ ceramic, promote a novel CeO₂–Cu₂O–Cu system to improve the interfacial bonded strength. Results show that the atom content of O is increased to approximately 30% with the addition of CeO₂ nanoparticles compared with the atom content without CeO₂ in the interfacial layer of Cu/Al₂O₃ ceramic clad composites. CeO₂ nanoparticles coated on the surface of Al₂O₃ ceramics can easily diffuse into the metallic Cu layer. CeO₂ nanoparticles can accelerate to form the eutectic liquid of Cu₂O–Cu as they have strong functions of storing and releasing O at an Ar pressure of 0.12 MPa. The addition of CeO₂ nanoparticles is beneficial for promoting the bonded strength of the Cu/Al₂O₃ ceramic clad composites. The bonded strength of the interface coated with nanoparticles of CeO₂ is increased to 20.8% compared with that without CeO₂; moreover, the electric conductivity on the side of metallic Cu is 95% IACS. The study is of great significance for improving properties of Cu/Al₂O₃ ceramic clad composites.

Cerium Oxide Nanoparticles Inside Carbon Nanoreactors for Selective Allylic Oxidation of Cyclohexene

The confinement of cerium oxide (CeO₂) nanoparticles within hollow carbon nanostructures has been achieved and harnessed to control the oxidation of cyclohexene. Graphitized carbon nanofibers (GNF) have been used as the nanoscale tubular host and filled by sublimation of the Ce(tmhd)₄ complex (where tmhd = tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)) into the internal cavity, followed by a subsequent thermal decomposition to yield the hybrid nanostructure CeO₂@GNF, where nanoparticles are preferentially immobilized at the internal graphitic step-edges of the GNF. Control over the size of the CeO₂ nanoparticles has been demonstrated within the range of about 4-9 nm by varying the mass ratio of the Ce(tmhd)₄ precursor to GNF during the synthesis. CeO₂@GNF was effective in promoting the allylic oxidation of cyclohexene in high yield with time-dependent control of product selectivity at a comparatively low loading of CeO₂ of 0.13 mol %. Unlike many of the reports to date where ceria catalyzes such organic transformations, we found the encapsulated CeO₂ to play the key role of radical initiator due to the presence of Ce³⁺ included in the structure, with the nanotube acting as both a host, preserving the high performance of the CeO₂ nanoparticles anchored at the GNF step-edges over multiple uses, and an electron reservoir, maintaining the balance of Ce³⁺ and Ce⁴⁺ centers. Spatial confinement effects ensure excellent stability and recyclability of CeO₂@GNF nanoreactors.

Effect of Increased Influent COD on Relieving the Toxicity of CeO2 NPs on Aerobic Granular Sludge

Due to the increased use of cerium oxide nanoparticles (CeO₂ NPs), their potential environmental risks have caused concern. However, their effects on the aerobic granular sludge (AGS) process and the later recovery of AGS are still unclear. In this study, we comprehensively determined the changes in pollutant removal and the levels of extracellular polymeric substances (EPS) in AGS that were exposed to CeO₂ NP treatments (0 (the control, R0), 1 (R1), and 5 (R5) mg/L), following an increase in the influent chemical oxygen demand (COD). An increase in the CeO₂ NP concentration enhanced their inhibitory effect on the removal of total nitrogen (TN) and total phosphorus (TP), and promoted the production of polysaccharides (PS) and proteins (PN) in loosely bound EPS (LB-EPS) or tightly bound EPS (TB-EPS), as well as the dissolved organic carbon (DOC) components in EPS, but had no long-term effects on the removal of organic matter. When the addition of CeO₂ NPs was stopped and the concentration of influent COD increased, the TN and TP removal efficiencies in R1 and R5 slowly increased and recovered. In R1, they were only 4.55 ± 0.55% and 2.71 ± 0.58% lower than in R0, respectively, while the corresponding values for R5 were 5.06 ± 0.46% and 6.20 ± 0.63%. Despite the LB-EPS and TB-EPS concentrations in the R1 and R5 treatments recovering and being similar to the levels in the control when no CeO₂ NPs were added, they were still slightly higher than in the R0, which indicating that the negative effects of CeO₂ NPs could not be completely eliminated due to the residual CeO₂ NP levels in AGS.

Use of CeO₂ Nanoparticles to Enhance UV-Shielding of Transparent Regenerated Cellulose Films

The major challenge in preparing polymer nanocomposites is to prevent the agglomeration of inorganic nanoparticles (NPs). Here, with regenerated cellulose (RC) films as supporting medium, UV-shielding and transparent nanocomposite films with hydrophobicity were fabricated by in situ synthesis of CeO₂ NPs. Facilitated through the interaction between organic and inorganic components revealed by X-ray diffraction (XRD) and Fourier transformation infrared spectroscopy (FTIR) characterization, it was found that CeO₂ NPs were uniformly dispersed in and immobilized by a cellulose matrix. However some agglomeration of CeO₂ NPs occurred at higher precursor concentrations. These results suggest that the morphology and particle size of CeO₂ and the corresponding performance of the resulting films are affected by the porous RC films and the concentrations of Ce(NO₃)₃·6H₂O solutions. The optimized nanocomposite film containing 2.95 wt% CeO₂ NPs had more than 75% light transmittance (550 nm), high UV shielding properties, and a certain hydrophobicity.

Effects of cerium oxide nanoparticles on bacterial growth and behaviors: induction of biofilm formation and stress response

In this paper, the effects of cerium oxide nanoparticles (CeO₂ NPs) on the group bacterial behaviors were elaborated. After 36-h cultivation, the biofilm biomass was enhanced by the sub-lethal concentrations of 0.5 and 2 mg/L CeO₂ NP exposure. Meanwhile, the promoted production of total amino acids in microbes further resulted in the increased surface hydrophobicity and percentage aggregation. To resist the CeO₂ NPs stress, the biofilm exhibited a double-layer microstructure, with the protein (PRO) and living cells occupying the bottom, the polysaccharide (PS), and dead cells dominating the top. The bacterial diversity was highly suppressed and Citrobacter and Pseudomonas from the phylum of γ-Proteobacteria strongly dominated the biofilm, indicating the selective and enriched effects of CeO₂ NPs on resistant bacteria. The stimulated inherent resistance of biofilm was reflected by the reduced adenosine triphosphate (ATP) content after 4 h exposure. The increased levels of reactive oxygen species (ROS) in the treatments of 8 h CeO₂ NP exposure led to the upregulated quorum sensing signals of acylated homoserine lactone (AHL) and autoinducer 2 (AI-2), beneficial to mitigating the environmental disturbance of CeO₂ NPs. These results provide evidences for the accelerating effects of CeO₂ NPs on biofilm formation through oxidative stress, which expand the understanding of the ecological effects of CeO₂ NPs.

Mechanistic understanding of cerium oxide nanoparticle-mediated biofilm formation in Pseudomonas aeruginosa

In this study, the biofilm formation of Pseudomonas aeruginosa in the presence of cerium oxide nanoparticles (CeO₂ NPs) was investigated. With the addition of 0.1 mg/L and 1 mg/L CeO₂ NPs, the biofilm development was substantially enhanced. During the attachment process, the enhanced surface hydrophobicity and excess production of mannosan and rhamnolipids in CeO₂ NP treatments were detected, which were conductive to the colonization of bacterial cells. During the maturation period, the biofilm biomass was accelerated by the improved aggregation percentage as well as the secretion of extracellular DNA and pyocyanin. The reactive oxygen species (ROS) generated by CeO₂ NPs were found to activate the N-butyryl homoserine lactone (C₄-HSL) and quinolone signals secreted by Pseudomonas aeruginosa. Moreover, the quorum sensing (QS) systems of rhl and pqs were initiated, reflected by the stimulated expression levels of biofilm formation-related genes rhlI-rhlR, rhlAB, and pqsR-pqsA. The addition of a quorum quencher, furanone C-30, significantly declined the activities of QS-controlled catalase and superoxide dismutase. A dose of antioxidant, ascorbic acid, effectively relieved the accelerating effects of NPs on biofilm formation. These results indicated that CeO₂ NPs could accelerate biofilm formation through the interference of QS system by generating ROS, which provides possible targets for controlling biofilm growth in the NP exposure environments.

Investigation of the rheological behavior of activated sludge in response to CeO2 nanoparticles and potential mechanism

With the rapid development of CeO₂ nanoparticles (NPs), the released CeO₂ NPs entering into wastewater treatment plants might bring the challenges for sludge pumping and mixing. In this study, we firstly elucidated the rheological behavior of 4.0 wt% sludge at various concentrations of CeO₂ NPs. With the increase of CeO₂ NPs to 5 mg/L, the shear stress at any given shear rate was reduced and the limiting viscosity was also decreased, indicating the sludge became more flowability. The dynamic sweep tests further demonstrated the decreased elastic behavior and weakened internal structure in response to low concentrations of CeO₂ NPs (≤ 5 mg/L). However, 20 mg/L CeO₂ NPs had negative effects on the rheological evolution of sludge, namely, better solid-like property and higher elastic structure. These results were mainly attributed to the combination of the decreased β-D-glucopyranose polysaccharides which support the rigid structure of sludge and the dramatically increased protein content (especially in 20 mg/L CeO₂ NPs). These results can potentially provide novel information for the efficient design of sludge treatment when coped with CeO₂ NPs. Graphical abstract ᅟ.

MnO2 Nanowire-CeO2 Nanoparticle Composite Catalysts for the Selective Catalytic Reduction of NO x with NH3

MnO _x-based catalysts have been applied to the selective catalytic reduction of NO _x with ammonia (NH₃) owing to their high NO _x removal efficiency and catalytic stability. In general, the fabrication of a variety of nanomaterials in a complex structure requires complicated processes, including heat treatment and a series of cleaning steps. In addition, MnO₂ which has diverse polymorphs, exhibits different catalytic effects depending on its crystalline structure. Among them, synthesizing the ε-MnO₂ phase, which functions as a nanocatalyst, has been the most difficult and has hardly been reported. Here, we report the synthesis of heterostructured composite nanocatalysts consisting of ε-MnO₂ nanowires (NWs) and CeO₂ nanoparticles (NPs) by applying pulsed currents sequentially. This method drastically simplifies the overall process compared to the conventional techniques. Through X-ray diffraction and transmission electron microscopy, it was confirmed that 2-3 nm of CeO₂ NPs were formed on the surfaces of the ε-MnO₂ NWs. The de-NO _x efficiency of the nanocatalysts was analyzed in terms of content variation, specific surface area, and the elemental chemical state of the surface. A ceramic filter containing the nanocatalysts shows a high catalytic activity over the broad operating temperature range 100-400 °C. In the low-temperature region, ε-MnO₂ plays a major role in determining the catalytic property, which is consistent with the Brunauer-Emmett-Teller (BET), H₂ temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) results. On the other hand, in the high-temperature region, the efficiency increases gradually as the content of CeO₂ increases. The H₂ TPR, NH₃-temperature-programmed desorption, and XPS patterns reveal why the composite exhibits such superior characteristics in the temperature range mentioned above.

Spleen data: Cerium oxide nanoparticles attenuate polymicrobial sepsis induced spenic damage in male Sprague Dawley rats

Sepsis is a serious life threatening medical emergency which, if not treated properly, oftentimes results in organ failure and death. Current sepsis treatment protocols are largely centered on the use of antibiotics and supportive care. Recent studies have suggested that antibiotics fail to be effective for sepsis treatment when administered during hypo-dynamic phase of sepsis that is usually characterized by the presence of a cytokine storm. As such, there is an urgent need to develop novel therapeutic drugs that target the inflammatory cytokines that are secreted as a result of increased reactive oxygen species. Cerium oxide nanoparticles (CeO₂) have been shown to act as anti-inflammatory and anti-oxidant agent. More recently, they have been shown to attenuate polymicrobial insult-induced mortality in Sprague Dawley rats. Here, we investigated whether CeO₂ nanoparticles can attenuate splenic damage in this animal model of sepsis. A single intravenous dose (0.5 mg/kg) of CeO₂ nanoparticles attenuated the sepsis-induced loss in splenic cell structural integrity. These improvements in splenic structure were accompanied by a decrease in expression of late phase pro-inflammatory cytokine high mobility group box 1 (HMGB1) along with reduced bacterial load in the blood and peritoneal fluid of septic animals. Taken together these findings suggest that CeO₂ nanoparticles can be used to attenuate polymicrobial insult-induced splenic damage in Sprague dawley rats.

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays

In this paper, a facile method was proposed to load CeO₂ nanoparticles (NPs) on anodic TiO₂ nanotube (NT) arrays, which leads to a formation of CeO₂/TiO₂ heterojunctions. Highly ordered anatase phase TiO₂ NT arrays were fabricated by using anodic oxidation method, then these individual TiO₂ NTs were used as tiny "nano-containers" to load a small amount of Ce(NO₃)₃ solutions. The loaded anodic TiO₂ NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO₃)₃ would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO₃)₃, cubic crystal CeO₂ NPs were obtained and successfully loaded into the anodic TiO₂ NT arrays. The prepared CeO₂/TiO₂ heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO₂/TiO₂ films, which could be very useful for environmental and energy-related areas.

Cerium Oxide Nanoparticles Induce Oxidative Stress and Genotoxicity in Human Skin Melanoma Cells

Extensive applications of cerium oxide (CeO2) nanoparticles require a better understanding of their possible effects on human health. However, data demonstrating the effect of CeO2 nanoparticles on the human skin melanoma cell remain scanty. In the current study, we determined the mechanism through which CeO2 nanoparticles (APS <25 nm) induce toxicity in human skin melanoma cells (A375). The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and neutral red uptake assays showed concentration and time-dependent cytotoxicity of CeO2 nanoparticles in A375 cells. CeO2 nanoparticles significantly induced the generation reactive oxygen species (ROS) and malondialdehyde, superoxide dismutase, and decreased glutathione levels in A375 cells. It was also observed that the CeO2 nanoparticles induced chromosomal condensation and caspase-3 activity. CeO2 nanoparticles exposed cells revealed the formation of DNA double-strand breakage as measured by percent tail DNA and olive tail moment through comet assay. The decline of cell viability, production of ROS, and DNA damage in A375 cells specifies that CeO2 nanoparticles have less capable to induce cyto and genotoxicity.

Single particle ICP-MS method development for the determination of plant uptake and accumulation of CeO2 nanoparticles

Cerium dioxide nanoparticles (CeO2NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, and dissolved cerium in the shoots of four plant species including cucumber, tomato, soybean, and pumpkin. An enzymatic digestion method with Macerozyme R-10 enzyme previously used for gold nanoparticle extraction from the tomato plant was adapted successfully for CeO2NP extraction from all four plant species. This study is the first to report and demonstrate the presence of dissolved cerium in plant seedling shoots exposed to CeO2NPs hydroponically. The extent of plant uptake and accumulation appears to be dependent on the plant species, requiring further systematic investigation of the mechanisms.