CeO2 Nanoparticles Research Articles

Green Synthesis, Spectroscopic, Electrochemical and Antifungal Characteristics of Ni-doped CeO2 Nanoparticles

This study intended to synthesize Nickel-doped Cerium oxide (Ni-CeO2 NPs) nanoparticles using Pedalium Murex leaf extract. X-ray diffraction (XRD) was used to investigate the structure of the Ni-CeO2 NPs. The XRD measurements showed that the Ni-CeO2 NPs crystallized into the face-centered cubic system. The Ni(1%)-CeO2 and Ni(3%)-CeO2 NP’s crystallite sizes were between 47[Formula: see text]nm and 59[Formula: see text]nm. FTIR and Raman spectral studies were conducted to investigate the sample’s atomic vibrations and chemical bonding. Energy-dispersive X-ray study and field-emission scanning electron microscopy were performed to examine the surface texture and chemical assembly of the Ni-CeO2 NPs. UV–Vis DRS spectrum study was performed to ascertain the reflectance characteristics and bandgap of Ni-CeO2 NPs. The Ni(1%)-CeO2 and Ni(3%)-CeO2 NPs were found to have bandgaps of 2.73[Formula: see text]eV and 2.82[Formula: see text]eV, respectively. Electrochemical impedance spectroscopy and cyclic voltammetry were employed to explore the electrochemical nature of Ni-CeO2 NPs and their capacitive properties at various scanning rates. Using the agar well-diffusion technique, the antifungal activities of Ni-CeO2 NPs were assessed. The experimental findings illustrate the utility of Ni-CeO2 NPs for supercapacitor electrode material and healthcare applications.

A p-n heterojunction PdO/CeO2 photocatalysts with enhanced photocatalytic ability for reduction of Hg(II) ions from aqueous solution

Heterostructured photocatalysts represent an essential role in the catalytic redox reactions in wastewater during illumination. In this contribution, p-n heterojunction PdO/CeO2 photocatalysts were constructed with enhanced photocatalytic ability for the reduction of Hg(II) utilizing HCOOH as hole scavengers under visible light. PdO NPs were uniformly spread on the mesoporous CeO2 surface, to act as potential separation centers of electrons and holes. The synthesized PdO/CeO2 nanocomposites exhibited an excellent photocatalytic ability, contrasted to the bare CeO2 NPs. The photocatalytic ability of PdO/CeO2 nanocomposites for reduction of Hg(II) has existed in the trends of 2%PdO ≥1.5%PdO >1%PdO >0.5 % PdO/CeO2 nanocomposites > bare CeO2 NPs. A photocatalytic ability of 100 % for Hg(II) reduction was achieved within 40 min utilizing 1.5 % PdO/CeO2 nanocomposites, which was 2.2 folds greater than that of bare CeO2 NPs. The rate constant of 1.5 % PdO/CeO2 nanocomposite (0.106 min−1) is more 9.9 times than that CeO2 NPs (0.0107 min−1). The enhancement photocatalytic ability of PdO/CeO2 can be interpreted to the wide surface area, narrow bandgap, numerous active sites, fast mobility, efficient diffusion of Hg(II), and the high separation rate of photocarriers. Considering the promotion photocatalytic ability of heterojunction PdO/CeO2 nanocomposites, the heterostructure photocatalyst is of magnificent importance to the photocatalytic redox reactions and exhibits a significant effect on our human health and ecological environment.

Advancing Chlorophyll Photostability: Dual Physicochemical Protection via Ce-Doped Hydrotalcite Organic-Inorganic Hybrid Pigments.

In pursuit of enhancing the photostability of chlorophyll, a novel organic-inorganic hybrid pigment has been synthesized via a supramolecular intercalation assembly method, incorporating cerium-ion-doped hydrotalcite as the host matrix and chlorophyll as the intercalated guest molecule. This innovative pigment amalgamates the vivid coloration properties of organic dyes with the robust stability characteristic of inorganic substances. Determined from the detailed investigation of the structural evolution of chlorophyll during photodegradation, the dual physicochemical protection mechanism is critical to the advancement of chlorophyll photostability. It leverages the oxygen barrier attributes of the hydrotalcite's laminate structure and the ultraviolet light absorption and scattering capabilities of CeO2 nanoparticles formed in situ. Furthermore, Ce-doping introduces a redox cycle between Ce4+ and Ce3+ ions, which serves as a chemical defense by neutralizing reactive oxygen species that emerge during chlorophyll degradation. This multifaceted approach results in a substantial enhancement of photostability, with the hybrid pigment containing 0.3 Ce doped content, demonstrating a mere 5.90% alteration in reflectance at the 635 nm peak after 250 h of UV-accelerated aging. This breakthrough provides a dual physicochemical protective strategy that not only significantly prolongs the lifespan of chlorophyll pigments but also holds potential for broadening their application scope in various industries, including plastics and coatings, where color fastness and durability are paramount.

Synergistic effect of Prussian Blue, Ceria, and reduced graphene oxide in ternary nanocomposite PBNCs-CeO2-rGO for electrochemical detection of hydrogen peroxide

Graphene-based ternary composites incorporating rare earth metals have garnered significant attention for their potential in low-detection applications of hydrogen peroxide (H2O2), owing to their cost-effectiveness and facile synthesis methods. In this study, we have reported the synergistic effect of Prussian blue nanocubes (PBNCs), reduced graphene oxide (rGO), and ceria nanoparticles (CeO2) in the ternary nanocomposite, i.e., PBNCs-CeO2-rGO for a low detection of H2O2. The enhanced electrocatalytic activity of ternary composite as compared to bare PBNCs and CeO2 nanoparticles was evidenced in different electrochemical methods such as Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Amperometry. The synthesized material was comprehensively characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. Remarkably, the synthesized material exhibited a low detection limit of up to 2.08 nM and a high sensitivity of 8671.6 μA mM−1 cm−2. Furthermore, the synthesized material demonstrated excellent selectivity, good reproducibility, and high stability, highlighting its potential for various sensing applications.

Oral enzyme-responsive nanoprobes for targeted theranostics of inflammatory bowel disease

BackgroundInflammatory bowel disease (IBD) is a progressive and debilitating inflammatory disease of the gastrointestinal tract (GIT). Despite recent advances, precise treatment and noninvasive monitoring remain challenging.MethodsHerein, we developed orally-administered, colitis-targeting and hyaluronic acid (HA)-modified, core-shell curcumin (Cur)- and cerium oxide (CeO2)-loaded nanoprobes (Cur@PC-HA/CeO2 NPs) for computed tomography (CT) imaging-guided treatment and monitoring of IBD in living mice.ResultsFollowing oral administration, high-molecular-weight HA maintains integrity with little absorption in the upper GIT, and then actively accumulates at local colitis sites owing to its colitis-targeting ability, leading to specific CT enhancement lasting for 24 h. The retained NPs are further degraded by hyaluronidase in the colon to release Cur and CeO2, thereby exerting anti-inflammatory and antioxidant effects. Combined with the ability of NPs to regulate intestinal flora, the oral NPs result in substantial relief in symptoms. Following multiple treatments, the gradually decreasing range of the colon with high CT attenuation correlates with the change in the clinical biomarkers, indicating the feasibility of treatment response and remission.ConclusionThis study provides a proof-of-concept for the design of a novel theranostic integration strategy for concomitant IBD treatment and the real-time monitoring of treatment responses.

Modulation of the Intrinsic Radical Scavenging Properties of CeO2 Nanoparticles

Cerium dioxide (CeO2) has been extensively investigated as a scavenger of reactive oxygen radicals, particularly in the context of polymer electrolyte membrane fuel cells. This study focuses on elucidating the impact of exposed crystal facets of CeO2 nanoparticles on their radical scavenging activities. The manipulation of crystal shapes, including rod, cube, and octahedral forms, allows for controlled variation of the exposed crystal facets of CeO2 NPs. Characterization of the resulting CeO2 NPs is conducted using XRD, Raman spectroscopy, XPS, BET, and Fenton’s reaction. The research reveals that the intrinsic radical scavenging activity of CeO2 NPs can be effectively modulated by controlling their exposed crystal facets.

(Dielectric Science and Technology Poster Award, 2nd Place) Activation of Amine Chemistries for the Enhanced Particle Removal Efficiency of CeO2 Nanoparticles Via Megasonic Processing Conditions

With the persistent advancement of semiconductor technology, the demand for high-efficiency device manufacturing processes has surged. Chemical Mechanical Planarization (CMP) is a cornerstone for achieving angstrom-scale surface uniformity crucial for integrated circuits (IC) and logic devices. Shallow Trench Isolation (STI) CMP involves the selective removal of bulk oxide to electrically isolate active components on wafer surfaces. The modulation of the Ce3+ to Ce4+ surface state is essential for improved performance in both CMP and post-CMP (p-CMP) applications. Ce3+ is ideal for oxide material polishing due to its strong adherence to oxide surfaces, while Ce4+ is optimal for p-CMP cleaning, given its weak bond to oxide surfaces. Current p-CMP industry-standard methods utilize mechanical approaches, such as polyvinyl alcohol (PVA) brush scrubbing. However, this process induces high levels of shear force (SF), leading to secondary defects on the wafer surface (i.e. scratches, corrosion, increased surface roughness). To address these limitations, non-contact cleaning methods utilizing megasonic energy have emerged, which rely on generating reactive oxygen species (ROS) to induce particle removal. Thus, this study focuses on enhancing ceria particle removal during post-CMP cleaning by employing amine-based chemistries coupled with megasonic energy. While preliminary results imply that the mechanical cavitations induced by megasonic waves improve cleaning efficiency, this method will be optimized via the introduction of amine-based chemistries. Specifically, this work aims to leverage the unique properties of amines coupled with megasonic energy to facilitate enhanced ceria removal through electron donation, inducing a reduction in the oxidation state of ceria from Ce³⁺ to Ce⁴⁺. This approach improves particle removal while limiting secondary defects, enhancing redox activity induced by megasonic waves and chemical interactions. The mechanisms behind this method will be validated with CeO2 oxidation state kinetics, interfacial frictional changes, wafer surface roughness analysis, and SEM validation of particle removal efficiency.

Edge-enriched CeO2/MoS2 heterostructure with coupled interface for enabling selective room-temperature NO2 detection

Endowed with abundant oxygen vacancy and excellent redox properties, CeO2 has attracted extensive attention for potential application in gas sensing, while it suffers from high working temperature and low sensing response. Herein, the MoS2 nanoflowers with abundant edges are coupled with CeO2 nanoparticles and the edge-enriched heterostructure is formed at interface. Owing to the synergistic effects of strong adsorption, abundant adsorption sites, and coupled interface, the CeO2/MoS2 compounds behave excellent room-temperature NO2 sensing performance. The 5 ppm NO2-sensing response of compounds is enhanced by 1033 % and 450 % in company with pure CeO2 and MoS2, respectively and the low detection limit of 1 ppm, high recovery rate, excellent long-term stability and selectivity are also obtained at room temperature. According to first-principles calculation, the binding energy of CeO2 for NO2 is much more negative than that of MoS2. Functionalization of MoS2 with CeO2 substantially improves NO2 adsorption. The Fermi level of MoS2 is nearer to the vacuum level than that of CeO2. The electrons are transferred from MoS2 to CeO2 at interface to create an electric field and an electron accumulation layer is formed on CeO2 to promote electron exchange between NO2 and the sensor and the NO2-sensing response. The results promote the application of two-dimensional materials to gas sensing boding well for the wireless sensing systems development in environmental and safety monitoring.

Biogenic synthesis of CeO2 nanoparticles via moringa oleifera seed extract: Photocatalytic and biological activity for textile dye degradation

This article presents a study on synthesizing cerium oxide nanoparticles utilizing cerium nitrate and Moringa oleifera seed extract as stabilizing and reducing agents. The XRD pattern of cerium oxide was a cubic structure with an average crystalline size of 11.92 nm. The surface feature of ceria nanoparticles has a foam-like nanostructure, type IV isotherms-mesoporous, with a 56.845 m2/g specific surface area. The UV–Vis absorbance and Tauc plot showed that the direct and indirect energy bandgap was 2.51 and 2.79 eV, respectively. TGA/DTA has established structural phase stability with corresponding mass changes by influencing bioactive molecules of seed extract in cerium nanoparticles. These nanoparticles exhibited effective antibacterial properties against S. aureus and E. coli pathogens, and the turbidimetry antioxidant properties were evaluated. Dye degradation through the photocatalyst was investigated, with the optimum degradation efficiency of 99.71 and 99.83 %, pseudo-first-order kinetics 4.62 × 10−2 and 5.07 × 10−2, respectively, for anionic-Congo red and cationic-Malachite green dye. The observed results concluded that green-mediated nanostructured ceria particles might effectively be used for antibacterial and photocatalytic purposes.

Rod-Shaped Au@Ce Nano-Platforms for Enhancing Photodynamic Tumor Collaborative Therapy.

Tumor photodynamic therapy (PDT) relies on intratumoral free radicals, while the limited oxygen source and the depletion of tissue oxygen may exacerbate the hypoxia. As the treatment progresses, there will eventually be a problem of insufficient free radicals. Here, it is found that Au@CeO2 nano-rods (Au@Ce NRs), assembled by gold nano-rods (Au NRs) and ceria nanoparticles (CeO2 NPs), can efficaciouslyabsorb near-infrared light (NIR) to promote the release of oxygen and free radicals. Au@Ce NRs exhibit a higher proportion of Ce3+ (Ce2O3) after oxygen release, while Ce3+ is subsequently oxidized to Ce4+ (CeO2) by trace H2O2. Interestingly, Au@Ce NRs re-oxidized by trace H2O2 can re-releasing oxygen and free radicals again upon NIR treatment, achieving oxygenation/oxygen evolution, similar to charging/discharging. This loop maximizes the conversion of limited oxygen source into highly cytotoxic free radicals. As a result, when B16-F10 cells are treated by NIR/Au@Ce NRs, more tumor cells undergo apoptosis, consistent with the higher level of free radicals. Importantly, NIR/Au@Ce NRs successfully suppresses tumor growth and promotes the generation of epidermal collagen fibers in the transplanted tumor model. Therefore, the rod-shaped Au@Ce NRs provide an ideal platform for maximizing the utilization of intratumoral oxygen sources and improving the treatment of melanoma.

Phosphatase-mimicking Zr@PDA nanozyme with excellent dispersion stability for the detection of fructose 1,6-diphosphate

Zr4+-doped polydopamine (Zr@PDA) nanozyme with phosphatase-like activity was synthesized by a one-pot hydrothermal method for the first time. Compared with previous representative phosphatase-mimicking nanozymes (i.e., CeO2 NPs, ZrO2 NPs and UiO-66), Zr@PDA not only exhibited higher dispersion stability in water, but also higher catalytical efficiency. Kcat/Km of Zr@PDA is 35 and 12 times that of UiO-66 and ZrO2 NPs, respectively, which would endow the Zr@PDA-based analytical methods with high sensitivity. As a demonstration, a novel colorimetric method based on Zr@PDA nanozyme was developed for sensitive detection of the drug fructose 1,6-diphosphate. The linear range is 1–15 μM with a detection limit as low as 0.38 μM.

Cerium dioxide nanozyme doped hybrid hydrogel with antioxidant and antibacterial abilities for promoting diabetic wound healing

Diabetic wounds are among the most severe chronic complications in patients with diabetes. Owing to the detrimental effects of high glucose and high levels of reactive oxygen species (ROS) in the wound microenvironment, diabetic wound healing is significantly challenging. To address the issues of elevated ROS levels and infection susceptibility in diabetic wounds, we designed a composite hydrogel system loaded with cerium dioxide nanoparticles (CeO2 NPs) and vancomycin. This hydrogel aimed to reshape the wound microenvironment by continuously consuming ROS and inhibiting infection. Experimental results demonstrated that the CeO2 NPs-loaded hydrogel demonstrated an 85.40% clearance rate of hydroxyl radicals (·OH) and achieved over 90% inhibition against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa), and effectively promoted the healing of diabetic mouse wounds. This cerium dioxide nanozyme hybrid hydrogel system can exert antioxidative and antibacterial effects and serve as a wound dressing to promote the healing of infected diabetic wounds.

Preparation and investigation of Ni-W/CeO2 composite coating and its structure and anti-corrosion properties with different ceria content and deposition time

In the current work, CeO2 nanoparticles were embedded in Ni-W alloy matrix by pulse electrochemical deposition on copper substrate to optimize their microstructure and corrosion resistance. The effects of CeO2 concentration and deposition time on Ni-W/CeO2 composite coating were investigated for optimized structure and improved corrosion resistance. The composite coatings present nodular-like surfaces with dense and compact growth profiles, containing 63.03–67.88 wt% Ni, 28.73–31.87 wt% W and 0.25–8.24 wt% Ce. The content of incorporated CeO2 in coatings increased with the increase of CeO2 concentration in electrolyte. The addition of CeO2 particles has refined the grains of the prepared coating. The surface became rougher with the extension of electrodeposition time. Ni-W/CeO2 composite coating electrodeposited at 10 g L−1 CeO2 for 60 min possessed the highest corrosion resistance, indicating enhanced corrosion protection and long-term stability. This premium coating can be applied in harsh environments to prolong the lifespan of machinery, equipment, and parts in marine, vehicle, aerospace, and chemical industries.

Synthesis and Characterization of Cr doped CeO2 nanoparticles for Rhodamine B dye degradation

The main aim of this work is to synthesis and study Cr doped CeO2 nanoparticles for Rhodamine B dye degradation. In this regard, 2 wt% and 4 wt% Cr doped CeO2 nanoparticles were successfully synthesized through a simple chemical precipitation method. The structural characteristics and elemental composition of the synthesized samples were analyzed using XRD and XPS techniques. The cubic fluorite structure with space group Fm 3m was confirmed through XRD and the presence of Ce, O and Cr atoms in the samples were identified through XPS. Spindle shaped structures were observed from FESEM analysis for 2 % Cr doped sample. Confocal Raman Spectroscopy was used to confirm the CeO2 stretching vibrational mode at 469 cm−1. The metal oxygen band was obtained at 447.49 cm−1 from FTIR spectroscopy. The band gap values were calculated from the Tauc plot and the values were found to be 2.0 eV, 2.85 eV and 2.88 eV for CeO2, 2 % Cr and 4 % Cr doped samples. The prepared nanoparticles were subjected to photocatalytic degradation of Rhodamine B dye at 5 ppm concentration and highest efficiency of 98.3 % was observed by the 4 % Cr doped CeO2 sample.

Nano-catalytic behavior of CeO2 nanoparticles in dye adsorption: Synthesis through bio-combustion and assessment of UV-light-driven photo-adsorption of indigo carmine dye

This study explores the adsorption of indigo carmine dye using bio-combusted cerium oxide nanoparticles (CeO2 NPs). CeO2 NPs were synthesized using a bio-combustion method, and then subjected to structural, morphological, and optical characterization for thorough investigation. Structural investigation was carried out using X-ray diffraction (XRD), which revealed a cubic structure with evaluated average crystallite size of 11.55 nm. Later, the same was verified by employing W–H plot (13.57 nm). UV–Vis spectroscopy revealed an effective band gap of 3 eV suited for photocatalytic applications. The metal-oxygen phonon band at 986.32 cm−1 and 871.96 cm−1 is confirmed using Infrared Spectroscopy (FTIR). The morphological analysis was done using Transmission and Scanning Electron Microscopy (TEM and SEM), which revealed well-dispersed, aggregated structure enclosing spherical nanoparticles with an average size of ∼14 nm. The early precursors were validated using EDAX analysis and SEM. Optical characteristics were investigated using photoluminescence (PL), which revealed a large charge transfer band between 360 nm and 435 nm. The dye removal efficiency of CeO2 NPs was evaluated against Indigo Carmine dye using UV light. The results showed that the significantly adsorption, with more than 70 % removed after 150 min. Kinetic experiments revealed that the depreciation occurred via a pseudo-first-order reaction process. Furthermore, the impacts of certain factors such as dye dosage, pH, reusability, and scavenger on adsorption rate were explored and shown to be effective values for the adsorption process. This study emphasizes the potential of CeO2 NPs as excellent photocatalysts for environmental remediation, especially in dye removal applications.

Designing a Robust Ni-P/CeO2 Superhydrophobic Composite Coating for Synergistically Enhanced Corrosion Protection and Friction Reduction Performance.

Superhydrophobic surfaces have received widespread attention for their unique hydrophobicity in metal corrosion protection. However, the shortcomings of mechanical stability and long-term corrosion resistance limit their practical application. In this work, we designed and fabricated an anticorrosive and friction reducing Ni-P/CeO2 superhydrophobic composite (SC) coating on a copper surface. The fabricated coating shows good superhydrophobicity with a water contact angle of up to 154°. The Ni-P support structure and CeO2 nanoparticles form a multilayer micro/nanostructure by electrodeposition, ensuring excellent mechanical stability of the Ni-P/CeO2 SC coating. Electrochemical tests indicate that the coating has excellent corrosion resistance due to the superhydrophobic air film, Ni-P barrier layer, and CeO2 inhibition. Moreover, the friction coefficient of the coating is only 0.11 under dry friction conditions, showing excellent friction-reducing performance, which is attributed to the cooperation of the low adhesion coefficient of superhydrophobic surfaces, the ball-rolling effect of CeO2 nanoparticles, and the self-healing effect of the Ni-P micro/nanostructure. This work provides a novel strategy for designing a robust superhydrophobic coating with mechanical stability, corrosion protection, and friction reduction abilities to inspire new applications of superhydrophobic surfaces.

Controlled Release of Ceria and Ferric Oxide Nanoparticles via Collagen Hydrogel for Enhanced Osteoarthritis Therapy.

Osteoarthritis (OA), characterized by chronic inflammation and cartilage degeneration, significantly affects over 500 million people globally. Nanoparticles have emerged as promising treatments for OA; however, current strategies often employ a single type of nanoparticle targeting specific disease stages, limiting sustained therapeutic efficacy. In this study, a novel collagen hydrogel is introduced, thiol crosslinked collagen-cerium oxide-poly(D,L-lactic-co-glycolic acid) microspheres encapsulating nanoparticles (CSH-CeO2-pFe2O3), designed for the controlled release of cerium oxide (CeO2) and ferric oxide (Fe2O3) nanoparticles for comprehensive OA management. The sulfhydryl cross-linked collagen matrix embeds CeO2 nanoparticles and poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres encapsulating Fe2O3 nanoparticles. The CSH-CeO2-pFe2O3 hydrogel exhibits enhanced mechanical strength and remarkable injectability, along with a significant promotion of cell adhesion, proliferation, and chondrogenic differentiation. Notably, the hydrogel demonstrates intelligent responsiveness to high levels of reactive oxygen species, initiating the rapid release of CeO2 nanoparticles to address the intense inflammatory responses of early-stage OA, followed by the sustained release of Fe2O3 nanoparticles to facilitate cartilage regeneration during the proliferative phase. In a rat model with cartilage defects, the hydrogel significantly alleviates inflammation and enhances cartilage regeneration, holding substantial potential for effectively managing the pathologically complex OA.

Size dependent dual functionality of CeO2 quantum dots: A correlation among parameters for hydrogen gas sensor and pollutant remediation

The metal oxide-based nanostructures of variable size and shape are found effective in optimizing the gas sensing ability and pollutant degradation. The size induced lattice strain and large band gap in 3nm CeO2 quantum dots evolved the ability towards hydrogen gas sensing and dye degradation compared to nanopebbles and nanoparticles of sizes 15 ± 3, and 30 ± 12 nm. The smaller CeO2 quantum dots than Debye length was found underlying reason for nearly four times sensor response and selectivity towards reducing hydrogen gases than the oxidizing gases at 1–10 ppm level. The lattice strain calculated by Rietveld refinement and W–H analysis was found in-line with the size of CeO2 nanostructures. The enhancement in lattice strain and optical band gap (2.66, 2.78, and 2.89 eV) with decrease in size are found critical for determining the overall efficiency of CeO2 nanostructures for photocatalytic activity, attributed to the strong quantum confinement effect. The higher catalytic activity of 98 % was achieved CeO2 quantum dots in comparison to the 95 % and 94 % obtained for CeO2 nanopebbles and nanoparticles. The impact of change in degradation efficacy and gas sensing ability of different CeO2 nanomaterials is discussed in detail. This work offers a novel and simplistic method to produce CeO2 quantum dots as an efficient sensor for selective detection of H2 gas and photocatalyst. The correlation between size, Debye length, band gap, and lattice strain gives an insight for understanding the underlying detection mechanism for selective detection of reducing gas molecules and efficient pollutant remediation.

Alleviation of arsenic stress in pakchoi by foliar spraying of engineered nanomaterials.

Addressing heavy metal contamination in leafy vegetables is critically important due to its adverse effects on human health. In this study, we investigated the inhibitory effects of foliar spraying with four nanoparticles (CeO2, ZnO, SiO2, and S NPs) on arsenic (As) stress in pakchoi (Brassica rapa var. Chinensis). The findings reveal that foliar application of ZnO NPs at 1 ~ 2.5 mg plant-1 and CeO2 NPs at 5 mg plant-1 significantly reduces As in shoots by 40.9 ~ 47.3% and 39.4%, respectively. Moreover, 5 mg plant-1 CeO2 NPs increased plant height by 6.06% and chlorophyll a (Chla) content by 30.2% under As stress. Foliar spraying of CeO2 NPs at 0.2-5 mg plant-1 also significantly enhanced superoxide dismutase (SOD) activity in shoots by 9.4 ~ 13.9%, lowered H2O2 content by 42.4 ~ 53.25%, and increased root protein contents by 79 ~ 109.2%. CeO2 NPs regulate the As(III)/As(V) ratio, aiding in As efflux from roots and thereby reducing As toxicity to plants. In vitro digestion experiments reveal that the consumption of CeO2 NPs carries the lowest health risk of As. In addition, foliar spraying of ZnO NPs at 1 ~ 2.5 mg plant-1 can suppress plant As uptake by modulating enzyme activity, reducing leaf damage, and enhancing chlorophyll content. The study demonstrates that high CeO2 NP concentrations and suitable ZnO NP concentrations can alleviate As toxicity in pakchoi, consequently reducing human health risks.

Surfactant-Free Synthesis of Melon Seed-Like CeO2 and Ho@CeO2 Nanostructures with Enriched Oxygen Vacancies: Characterization and Their Enhanced Antibacterial Properties.

To overcome the poor antibacterial performance of cerium oxide (CeO2) nanoparticles at low concentrations, melon seed-shaped CeO2 (MS-CeO2) and holmium (Ho)-doped CeO2 (Ho@MS-CeO2) nanoparticles were synthesized using a simple precipitation method without the addition of any surfactants. The surface morphology, phase structure, crystallinity, Ce3+ and Ce4+ valence, lattice defects, and reactive oxygen species (ROS) production of both synthesized nanostructures were examined using different techniques, i.e., scanning electron microscopy (SEM), energydispersive X-ray (EDX), resolution transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), Raman spectroscopy, ultraviolet (UV) spectra, fluorescence spectra, and zeta potential (ζ). The results show that under certain stirring and aging temperatures, CeO2 and Ho-doped CeO2 nanoparticles with a melon seed-like morphology can be prepared in a short period. Both nanoparticles were tested as antiseptic agents against G+ and G - bacteria (E. coli and S. aureus), and the results confirmed that the Ho@MS-CeO2 nanostructures exhibited remarkable antimicrobial activity at a low concentration (0.5 mg/L) compared with the control group, which is attributed to the reversible conversion of Ce3+ and Ce4+ in the ceria crystal lattice, enriched oxygen vacancy, ROS species production, and positive surface charge.