Ceria Nanorods Research Articles

An electrochemiluminescence sensor for ultrasensitive determination of tyrosine based on ceria nanomaterial as a novel luminophor

BackgroudRecently, optical nanomaterials have attracted much attention in the field of electrochemiluminescence (ECL). Nanostructured ceria possessed unique optical properties, and it's always used for constructing ECL sensor as catalyst for improving sensing performance, while the ECL property of ceria is rarely studied. In fact, it could be the potential candidate for applying in ECL sensors based on size and shape dependency optical property caused by the quantum scale effects. Therefore, new simple and efficient ceria nanomaterial used as luminophor for constructing the ECL sensor have aroused more research interest and motivation. (91 words). ResultsIn the work, three kinds of nanostructured ceria, ceria nano-cube (CeO2-NC), ceria nano-rods (CeO2-NR) and ceria nano-particle (CeO2-NP), have been prepared by hydrothermal method, and CeO2-NC with the less oxygen vacancy has the highest ECL signal. Moreover, how the shape affects the ECL property was investigated in detail, especially the oxygen vacancy on the surface of the ceria. The less of oxygen vacancy content of CeO2 nanomaterials is more favorable the ECL reaction. Furthermore, a novel ECL sensor was constructed based on reduced graphene oxide (rGO), Au nano-particle (AuNPs) and CeO2-NC for Tyrosine (Tyr) determination owing to the electron transform between the luminous of ceria and Tyr resulting in the cathodic ECL intensity quenched correspondingly, and it has possessed excellent sensing performance with a linear range of 0.005–20 nmol/L and the limit of detection (LOD) value of 1.7 fmol/L (141 words) Significance and noveltyThe proposed method demonstrated excellent selectivity and ultra-sensitivity toward Tyr, which had been used for the determination of Tyr in human serum successfully, possessing outstanding analytical performance. Therefore, nanostructured ceria is a new category of efficient and promising luminophore, which would open new avenues for the potential application in the field of ECL sensing for clinical diagnosis. (57 words).

Platelet Ceria Catalysts from Solution Combustion and Effect of Iron Doping for Synthesis of Dimethyl Carbonate from CO2.

Solution combustion (SC) remains among the most promising synthetic strategies for the production of crystalline nanopowders from an aqueous medium, due to its easiness, time and cost-effectiveness, scalability and eco-friendliness. In this work, this method was selected to obtain anisometric ceria-based nanoparticles applied as catalysts for the direct synthesis of dimethyl carbonate. The catalytic performances were studied for the ceria and Fe-doped ceria from SC (CeO2-SC, Ce0.9Fe0.1O2-SC) in comparison with the ceria nanorods (CeO2-HT, Ce0.9Fe0.1O2-HT) obtained by hydrothermal (HT) method, one of the most studied systems in the literature. Indeed, the ceria nanoparticles obtained by SC were found to be highly crystalline, platelet-shaped, arranged in a mosaic-like assembly and with smaller crystallite size (≈6 nm vs. ≈17 nm) and higher surface area (80 m2 g-1 vs. 26 m2 g-1) for the undoped sample with respect to the Fe-doped counterpart. Although all samples exhibit an anisometric morphology that should favor the exposition of specific crystalline planes, HT-samples showed better performances due to higher oxygen vacancies concentration and lower amount of strong basic and acid sites.

Shape tailored nano-ceria as high performance supercapacitor electrode material

Electrochemical energy storage devices herald a brighter future, offering efficient and sustainable solutions to meet the escalating global energy demands. The current work investigates the development and characterization of different ceria nanostructures (nanorod, nanocube, and nanopolyhedra) as effective electrode materials for supercapacitor applications. The electrode materials are systematically characterized using various spectroscopic and non-spectroscopic techniques. Galvanostatic charge-discharge, electrochemical impedance spectroscopy, and cyclic voltammetry techniques are used to evaluate the electrochemical performance of the electrode materials. The optimum material for the said application is cerium nanorod which has the maximum specific capacitance of 437.27 F/g in acid electrolytes. The current-voltage (I-V) characteristics of the ceria nanostructures exhibit hysteresis behavior; ceria nanorod showing coexistence of memristive and memcapacitive nature. The loop area of the hysteresis curve, derived from the ratio of OFF resistance to ON resistance (ROFF/RON) at 4 V, yields approximate values of 1.08, 1.33, and 1.57 for ceria nanocubes, ceria nanopolyhedra, and ceria nanorods, respectively. Impedance vs. frequency analysis of the samples was also carried out to study their electrical and transport properties. The results obtained from electrochemical analyses are complimented by electrical studies.

Evolution of Ce4+ Lewis acidity during dehydroxylation of ceria nanoparticles with different morphology: An integrated FTIR, DFT and HRTEM study

Ceria is an important redox catalyst and its activity depends on the open Ce4+/Ce3+ sites, anion vacancies, surface OH groups and the ratio between them. We investigated the effect of dehydroxylation on the evolution of Ce4+ Lewis acidity of oxidized ceria nanocubes, nanopolyhedra, and nanorods. The {111} face is not hydroxylated and the exposed Ce4+ sites, after dehydration, adsorb CO weakly, forming linear carbonyls. The hydroxyl coverage of the {110} face consists of terminal and bridging hydroxyls, and dehydroxylation occurs between 423 and to 573 K by interaction between these groups. The produced Ce4+ sites form stronger linear carbonyls. The {100} face is covered by bridging OH groups, which are progressively removed even at 773 K. The created Ce4+ sites coordinate CO in a bridging mode and, at higher coverage, connect two bridging CO molecules. Ce4+ sites on edges and defects appear at high evacuation temperature and form mono- and dicarbonyls.

Rational design of complex quantum dots decorated ceria nanorods for efficient visible-light driven nitrogen fixation

Ceria-based materials, as very active photocatalysts for redox reactions, have been widely investigated, but there are few reports on nitrogen photofixation. Herein, complex dots of Cu2O/Cu-C decorated CeO2 nanorods with an overall photocatalytic nitrogen fixation process are considered. Remarkable photocatalytic performances are obtained by adjusting the band gap structures and surface activity site status. The as-prepared sample has excellent visible light absorption capacity, more photoinduced oxygen defects and excellent nitrogen absorption ability. The ammonia yield is approximately 1124 µmol·gcal−1·h−1 under light irradiation with no sacrificial agents, increasing approximately 8.5 times compared with the Cu-decorated sample. The apparent quantum efficiency at 420 nm is also more than 1.1%. This work may provide a new avenue for the efficient design of photocatalytic materials without any precious metals.

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods.

CeO2 nanorod based catalysts for the base-free synthesis of azoxy-aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (Ov ) and base sites are critical for their excellent catalytic properties. The Ov , i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α-Csp3 -H in ethanol to the nitro group coupling it to the redox reactions between Ce3+ and Ce4+ . At the same time, the base sites catalyze the condensation step to selectively produce azoxy-aromatics. The catalytic route opens a much improved way to use non-noble metal oxides without additives for the selective functional group reduction and coupling reactions.

Synergy of Oxygen Vacancies and Base Sites for Transfer Hydrogenation of Nitroarenes on Ceria Nanorods

AbstractCeO2 nanorod based catalysts for the base‐free synthesis of azoxy‐aromatics via transfer hydrogenation of nitroarenes with ethanol as hydrogen donor have been synthesized and investigated. The oxygen vacancies (Ov) and base sites are critical for their excellent catalytic properties. The Ov, i.e., undercoordinated Ce cations, serve as the sites to activate ethanol and nitroarenes by lowering the energy barrier to transfer hydrogen from α−Csp3−H in ethanol to the nitro group coupling it to the redox reactions between Ce3+ and Ce4+. At the same time, the base sites catalyze the condensation step to selectively produce azoxy‐aromatics. The catalytic route opens a much improved way to use non‐noble metal oxides without additives for the selective functional group reduction and coupling reactions.

Non-oxidative calcination enhances the methane dry reforming performance of Ni/CeO2−x catalysts under thermal and photo-thermal conditions

Calcination in hydrogen or argon improved nickel dispersion and increased the abundance of oxygen vacancies in ceria nanorods. Visible light both accelerated the methane reforming rate and improved H2 selectivity by retarding the RWGS reaction.

Non-thermal plasma enabled catalytic dry reforming of methane over a ceria nanorod supported NiO catalyst: the role of Ru as a coke resistant active site

This study reports that a 14 wt% Ni–1 wt% Ru bimetallic catalyst supported on CeO2 nanorods can offer superior conversion and stability against coking during non-thermal plasma-assisted dry reforming of methane.

Bi-doped CuCeO2−x nanorod catalysts for photothermal CO-PROX in H2-rich streams: Enhanced oxygen vacancy and light absorption capacity

The wide band gap of ceria limited the light absorption and photothermal conversion of copper-ceria catalyst for photothermal preferential oxidation of CO (CO-PROX). In the present work, doping Bi element was adopted to regulate the energy band and catalytic performance of CuCeO2−x nanorod catalysts for photothermal CO-PROX. Bi/CuCeO2−x nanorods were synthesized by co-precipitation hydrothermal and deposition precipitation method. The Bi/CuCeO2−x catalyst with the molar ratio of Bi/Ce 2.5% exhibited the best catalytic performance and the CO conversion reached 90% under 2.5 suns with a surface temperature of 120 °C. The doped Bi species were incorporated into the CeO2 lattice and promoted the formation of oxygen vacancy sites and the strong Cu-Ce interaction, as revealed by XRD, XPS, Raman and H2-TPR results. In addition, doping Bi reduced the band gap of ceria nanorod from 2.77 to 2.47 eV and remarkably enhanced the UV–vis light response and photogenerated carrier separation of Bi/CuCeO2−x-2.5.

ROS-mediated anticancer effects of EGFR-targeted nanoceria.

The therapeutic effectiveness of anticancer drugs, including nanomedicines, can be enhanced with active receptor-targeting strategies. Epidermal growth factor receptor (EGFR) is an important cancer biomarker, constitutively expressed in sarcoma patients of different histological types. The present work reports materials and in vitro biomedical analyses of silanized (passive delivery) and/or EGF-functionalized (active delivery) ceria nanorods exhibiting highly defective catalytically active surfaces. The EGFR-targeting efficiency of nanoceria was confirmed by receptor-binding studies. Increased cytotoxicity and reactive oxygen species (ROS) production were observed for EGF-functionalized nanoceria owing to enhanced cellular uptake by HT-1080 fibrosarcoma cells. The uptake was confirmed by TEM and confocal microscopy. Silanized nanoceria demonstrated negligible/minimal cytotoxicity toward healthy MRC-5 cells at 24 and 48 h, whereas this was significant at 72 h owing to a nanoceria accumulation effect. In contrast, considerable cytotoxicity toward the cancer cells was exhibited at all three times points. The ROS generation and associated cytotoxicity were moderated by the equilibrium between catalysis by ceria, generation of cell debris, and blockage of active sites. EGFR-targeting is shown to enhance the uptake levels of nanoceria by cancer cells, subsequently enhancing the overall anticancer activity and therapeutic performance of ceria.

Gold supported on Gd-doped CeO2 nanorods applied as water-gas shift catalyst under H2 rich stream

In this work, we report the synthesis of catalysts based on ceria nanorods (CeO2NRs) doped with 3% and 5% mol gadolinium. The supports were obtained from cation co-precipitation hydrothermal synthesis over which gold nanoparticles (AuNPs) were deposited by the deposition-precipitation (DP) methodology, allowing the Au nanoparticles size control at around 3 nm. The catalysts were evaluated in water gas shift reaction and showed high activity under a H2 rich stream (7%CO/7%CO2/14%N2/42%H2/30%H2O) with steam/process gas molar ratio (S/G) of 0.3 at 300 and 250 °C. The results revealed that Gd-doping increased the oxygen vacancies concentration due to the insertion of a trivalent cation in ceria lattice. In addition, the synergistic effect between AuNPs and Gd-doped CeO2 provided the increase of reducibility and oxygen storage capacity (OSC). These properties were associated with the catalytic activity in water gas shift reaction. The nanostructured materials decreased the CO concentration under conditions of H2 rich stream, indicating the catalysts potential for industrial applications after further studies. The catalyst doped with 5% mol Gd was the most active and achieved 24% of CO conversion at 300 °C.

Green Synthesis of Nanosilver Decorated on Ceria Nanorod for the Catalytic Reduction of Methyl Orange

Green Synthesis of Nanosilver Decorated on Ceria Nanorod for the Catalytic Reduction of Methyl Orange

CoOx-CoP/Nitrogen-Doped Tubular-Carbon Nanostructures Supported over Ceria Nanorods as an Efficient Scavenger in the Electrocatalytic Oxygen Reduction Reaction

CoOx-CoP/Nitrogen-Doped Tubular-Carbon Nanostructures Supported over Ceria Nanorods as an Efficient Scavenger in the Electrocatalytic Oxygen Reduction Reaction

Enhancement effects of surface and bulk oxygen vacancies on the photocatalytic properties of ceria

Ceria is a widely known photocatalyst, to clearly understand the effects of oxygen vacancies (OVs) distribution on photocatalytic performance of ceria, surface and bulk OVs have been introduced in ceria nanorods and nanopolyhedrons. According to H2-TPR, XPS, Raman, and EPR results, P-800 (ceria nanopolyhedrons calcined at 800 °C) and R-800 (ceria nanorods calcined at 800 °C) had surface and bulk OVs and a larger OV concentration than P-500 (ceria nanopolyhedrons calcined at 500 °C) and R-500 (ceria nanorods calcined at 500 °C) which just had surface OVs, respectively. The former showed a clearly enhanced photocatalytic activity toward methylene blue (MB) and tetracycline (TC) degradation compared with the latter. After introducing surface and bulk OVs, the generated defect states in Ce 4f, metallization of ceria, and lower energy shifted density of states (DOS) co-promoted the separation of photo-excited e−/h+, which may mainly contribute to the enhancement of photocatalytic performance of P-800 and R-800. R-800 had the major active species of ·O2−/h+ to photodegrade TC, which was different from R-500 of e−/h+, due to the more negative ECB and more absorbed O2 for R-800. The synergistic effects of surface and bulk OVs were more significant for ceria nanorods than nanopolyhedrons, which may be due to the exposed facet of (110).

Simultaneous Generation of Ammonia during Nitrile Waste Gas Purification over a Silver Single-Atom-Doped Ceria Catalyst.

Catalytic elimination of toxic nitrile waste gas is of great significance for preserving the atmospheric environment, but achieving resource utilization during its destruction has been less explored. Herein, this study proposed a universal strategy for nitrile waste gas purification and NH3 generation simultaneously. The developed silver single-atom-doped ceria nanorod (Ag1/R-CeO2) was endowed with near complete mineralization and around 90% NH3 yield at 300-350 °C for the catalytic oxidation of both acetonitrile and acrylonitrile. The introduction of the Ag single atom created more surface oxygen vacancies, thereby promoting water activation to form abundant surface hydroxyl groups. As a benefit from this, the hydrolysis reaction of nitrile to generate NH3 was accelerated. Meanwhile, the electron transfer effect from the Ag atom to Ce and hydroxyl species facilitated NH3 desorption, which inhibited the oxidation of NH3. Moreover, the increased surface oxygen vacancies also promoted the mineralization of hydrolysis carbonaceous intermediates to CO2. In contrast, the Ag nanoparticle-modified sample possessed stronger reducibility and NH3 adsorption, leading to the excessive oxidation of NH3 to N2 and NOx. This work provided a useful guidance for resourceful purification of nitrile waste gas.

Polydopamine Modified Ceria Nanorods Alleviate Inflammation in Colitis by Scavenging ROS and Regulating Macrophage M2 Polarization.

Inflammatory bowel disease (IBD) is closely related to higher intracellular oxidative stress. Therefore, developing a novel method to scavenge the harmful reactive oxygen species (ROS) and alleviate colon inflammation to treat IBD is a promising strategy. CeO2@PDA-PEG (CeO2@PP) were synthesized by modifying ceria (CeO2) nanorods with polydopamine (PDA) and polyethylene glycol (PEG). The ROS scavenging ability of CeO2@PP was detected by using flow cytometry and confocal laser scanning microscope (CLSM). The anti-inflammatory ability of CeO2@PP was determined in vitro by treating lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. The biocompatibility of CeO2@PP was evaluated in vivo and in vitro. Moreover, the therapeutic effects of CeO2@PP in vivo were estimated in a dextran sulfate sodium salt (DSS)-induced colitis mouse model. Physicochemical property results demonstrated that PDA and PEG modification endowed CeO2 nanorods with excellent dispersibility and colloidal stability. CeO2@PP maintained superior enzyme-like activity, including superoxide dismutase (SOD) and catalase (CAT), indicating antioxidant ability. Moreover, in vitro results showed that CeO2@PP with PDA promotes LPS-induced RAW 264.7 macrophages into M2-type polarization. In addition, in vitro and in vivo results showed that CeO2@PP have great biocompatibility and biosafety. Animal experiments have shown that CeO2@PP have excellent anti-inflammatory effects against DSS-induced colitis and effectively alleviated intestinal mucosal injury. The nanoplatform CeO2@PP possessed excellent antioxidant and anti-inflammatory properties for scavenging ROS and modulating macrophage polarization, which is beneficial for efficient colitis therapy.

Sodium niobate microcubes decorated with ceria nanorods for hydrogen peroxide electrogeneration: An experimental and theoretical study

The present work investigates the catalytic activity of NaNbO3 microcubes decorated with CeO2 nanorods on carbon (1 %, 3 %, 5 %, and 10 % w/w) for H2O2 electrogeneration. The crystalline phases and the morphology of the materials were identified with scanning electron microscopy, transmission electron microscopy, X‐ray diffraction and X-ray Photoelectronic spectroscopy. Contact angle measurements were performed to characterize the hydrophilicity of each material. The H2O2 electrogeneration was assessed by oxygen reduction reaction using the rotating ring-disk electrode technique. Electrochemical characterization results shown an enhancement on the H2O2 electrogeneration by NaNbO3 @CeO2/C-based materials compared to what was obtained with pure Vulcan XC72. The 1 % NaNbO3 @CeO2/C electrocatalyst presented the lower starting potential for the ORR and a 2.3 electron transfer, favoring the 2-electron mechanism and providing a higher H2O2 electrogeneration rate. Also, the enhancement of oxygen-containing functional groups showed the potential to comprehensively tune properties and optimize active sites and, consequently, increases the H2O2 electrogeneration. Density functional theory calculations indicated that NaNbO3 and CeO2 surfaces have a similar low theoretical overpotential for this reaction and that CeO2 improves the catalyst facilitating the electron transfer. These results indicate that NaNbO3 @CeO2/C-based electrocatalysts are promising materials for in situ H2O2 electrogeneration.

Aging mechanisms of nanoceria and pathways for preserving optimum morphology

Thermal aging can modify the unique properties of a nanomaterial via structural change. Mechanistic understanding of the aging process, including accelerated aging under high-temperature operating conditions, is a first step towards property preservation via controlling, limiting, or suppressing aging-related processes. Here, we use molecular dynamics to simulate thermal aging of ceria nanocubes and nanorods, which transform into nanopolyhedra; comparisons with experimental TEM images are presented alongside. We find that morphology changes proceed via the turbulent mobility of CexOy surface clusters from one part of the nanoceria to another. For nanorods and nanocubes, catalytically important {100} and {110} surfaces are eroded, whereas the relative area of {111} surfaces increase. Detailed analysis of the simulations reveals that atoms in the CexOy clusters do not all move simultaneously. Rather, (-O-Ce-O-Ce-O-)n ‘chains’ (subsets of the larger CexOy clusters) move with collective motion, while the atoms inside the chains move in a ‘worm-like’ fashion. This reduces the activation energy barrier associated with all the atoms in the chain simultaneously moving into an activated (saddle point) configuration. We predict gadolinium-doped ceria nanocubes, charge-compensated by oxygen vacancies, age faster than undoped and fully oxidised ceria nanocubes. In particular, dopants that increase catalytic activity, may also accelerate aging by introducing oxygen vacancies that break the (-O-Ce-O-Ce-O-)n chains into smaller chains with reduced activation energies. Accordingly, we advocate that when doping is used to confer catalytic activity, experiment should also target the collective motion of surface (-O-Ce-O-Ce-O-)n chains to maximise thermal stability.

Synergistic effect of acid-base and redox properties of nano Au/CeO2-cube on selective hydrogenation of nitrobenzene to aniline

Catalysts with 1 wt% gold doped on various morphologies of ceria (nano-cubes, nano-rods and nano-polyhedra), were prepared by the deposition precipitation method. The samples are characterized and used to catalyze the hydrogenation of nitrobenzene in ethanol. The highest nitrobenzene conversion (92%) and aniline selectivity (90%) are achieved from the catalyst supported by nano-cube CeO2 (1 wt% Au/CeO2-cube). The calcination temperatures of both the support and catalyst can influence the acid-base properties, the morphology and the valance of Au and Ce, which are key factors in the adsorption of nitrobenzene, the desorption of aniline and the formation of active H− species, respectively. We find that small-size Au nanoparticles (2.1 nm) with appropriate ratio of Au0 to Auδ+, acid/base sites with sufficient density and appropriate strength, and oxygen vacancy of ceria on the interface of Au and ceria are favorable to the formation of aniline on 1 wt% Au/CeO2-cube.