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.

Photocatalytic Co-Reduction of N2 and CO2 with CeO2 Catalyst for Urea Synthesis.

The effective conversion of carbon dioxide (CO2 ) and nitrogen (N2 ) into urea by photocatalytic reaction under mild conditions is considered to be a more environmentally friendly and promising alternative strategies. However, the weak adsorption and activation ability of inert gas on photocatalysts has become the main challenge that hinder the advancement of this technique. Herein, we have successfully established mesoporous CeO2-x nanorods with adjustable oxygen vacancy concentration by heat treatment in Ar/H2 (90 % : 10 %) atmosphere, enhancing the targeted adsorption and activation of N2 and CO2 by introducing oxygen vacancies. Particularly, CeO2 -500 (CeO2 nanorods heated treatment at 500 °C) revealed high photocatalytic activity toward the C-N coupling reaction for urea synthesis with a remarkable urea yield rate of 15.5 µg/h. Besides, both aberration corrected transmission electron microscopy (AC-TEM) and Fourier transform infrared (FT-IR) spectroscopy were used to research the atomic surface structure of CeO2 -500 at high resolution and to monitor the key intermediate precursors generated. The reaction mechanism of photocatalytic C-N coupling was studied in detail by combining Density Functional Theory (DFT) with specific experiments. We hope this work provides important inspiration and guiding significance towards highly efficient photocatalytic synthesis of urea.

Ultrasensitive Electrochemical Detection of Clostridium perfringens DNA Based Morphology-Dependent DNA Adsorption Properties of CeO2 Nanorods in Dairy Products.

Foodborne pathogens such as Clostridium perfringens can cause diverse illnesses and seriously threaten to human health, yet far less attention has been given to detecting these pathogenic bacteria. Herein, two morphologies of nanoceria were synthesized via adjusting the concentration of NaOH, and CeO2 nanorod has been utilized as sensing material to achieve sensitive and selective detection of C. perfringens DNA sequence due to its strong adsorption ability towards DNA compared to nanoparticle. The DNA probe was tightly immobilized on CeO2/chitosan modified electrode surface via metal coordination, and the DNA surface density was 2.51 × 10−10 mol/cm². Under optimal experimental conditions, the electrochemical impedance biosensor displays favorable selectivity toward target DNA in comparison with base-mismatched and non-complementary DNA. The dynamic linear range of the proposed biosensor for detecting oligonucleotide sequence of Clostridium perfringens was from 1.0 × 10−14 to 1.0 × 10−7 mol/L. The detection limit was 7.06 × 10−15 mol/L. In comparison, differential pulse voltammetry (DPV) method quantified the target DNA with a detection limit of 1.95 × 10−15 mol/L. Moreover, the DNA biosensor could detect C. perfringens extracted DNA in dairy products and provided a potential application in food quality control.

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 efficaciously absorb 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.

Low-Temperature Plasma-Assisted Catalytic Dry Reforming of Methane over CeO2 Nanorod-Supported NiO Catalysts in a Dielectric Barrier Discharge Reactor.

Nonthermal plasma (NTP)-assisted catalytic dry reforming of methane (DRM) is considered a powerful single-stage reaction mechanism because of its ability to activate normally stable CO2 and CH4 at a low temperature under ambient conditions. The thermodynamic barrier of DRM requires a high operating temperature (>700 °C), which can be reduced by nonequilibrium plasma. Herein, we present a method for the wet-impregnation synthesis of CeO2 nanorod (NR)-supported 5 and 15 wt % NiO catalysts for efficient NTP-promoted DRM with an applied power in the range of 24.9-25.8 W (frequency: 20 kHz), a CH4:CO2 feed gas ratio of 100:250 sccm, and a total flow rate of 350 sccm. The presence of NTP dramatically increased the reaction activity, even at 150 °C, which is usually inaccessible for thermally catalyzed DRM. The CH4 and CO2 conversion reaches a maximum of 66 and 48%, respectively, at 500 °C with the 15 wt % NiO/CeO2 NR catalyst, which are much higher than the values obtained for the 5 wt % NiO/CeO2 NR catalyst under the same conditions. According to the X-ray photoelectron spectroscopy profile for 15 wt % NiO/CeO2 NR, a higher concentration of NiO on CeO2 increases the proportion of Ce3+ in the catalyst, suggesting enhanced oxygen vacancy concentration with an increased amount of NiO loading. Additionally, a higher NiO loading promotes a higher rate of replacement of Ce4+ with Ni2+, which generates more oxygen vacancies due to the induced charge imbalance and lattice distortion within the CeO2 lattice. As a result, it can be inferred that the incorporation of Ni ions into the CeO2 structure resulted in inhibited growth of CeO2 crystals due to the creation of a NixCe1-xO2-α solid solution and the production of oxygen vacancies.

Highly efficient catalytic reduction of 4-nitrophenol and organic dyes by ultrafine palladium nanoparticles anchored on CeO2 nanorods.

Uniformly dispersed Pd nanoparticles on certain supports exhibit exceptional catalytic performance toward various environmental applications. In this work, ultrafine Pd nanoparticles anchored on CeO2 nanorods were synthesized via an absorption-in situ reduction method. The activity of the CeO2/Pd nanocomposites was systematically investigated toward reduction of 4-nitrophenol (4-NP) and organic dyes including methyl blue, rhodamine B, methyl orange, and Congo red. The results indicated that the CeO2/Pd nanocomposites with different weight ratios of Pd nanoparticles (10.23 wt%, 11.01 wt%, and 14.27 wt%) can almost completely reduce 4-NP with a rate constant of 3.31×10-1, 3.22×10-1, and 2.23×10-1 min-1. Besides, the 10.23 wt% CeO2/Pd nanocomposites exhibit remarkable enhanced catalytic activity toward reduction of organic dyes. The catalysts display ideal stability after being used for three times for the reduction of 4-NP. We believe that our strategy demonstrated here offers insights into the design and fabrication of novel Pd-based nanocomposites for various heterogeneous catalysis applications.

CeO2 nanoparticles induce pulmonary fibrosis via activating S1P pathway as revealed by metabolomics.

CeO2 nanoparticles (NPs) have been shown to cause lung fibrosis, however, the exact underlying molecular mechanisms are poorly understood. In this study, we have conducted a mass spectrometry-based global metabolomic analysis of human bronchial epithelial BEAS-2B cells treated by CeO2 NPs with different aspect ratios and assessed their toxicity on the bronchial epithelial cells by various cell-based functional assays. Although CeO2 NPs at doses ranging from 12.5 µg/mL to 25 µg/mL displayed low cytotoxicity on the bronchial epithelial cells, the metabolomic analysis revealed a number of metabolites in the cellular metabolic pathways of sphingosine-1-phosphate, fatty acid oxidation, inflammation, etc. were significantly altered by CeO2 NPs, especially those with high aspect ratios. More importantly, the robustness of metabolomics findings was further successfully validated in mouse models upon acute and chronic exposures to CeO2 NPs. Mechanistically, CeO2 NPs upregulated transforming growth factor beta-1 (TGF-ß1) levels in BEAS-2B cells in an aspect ratio-dependent manner through enhancing the expression of early growth response protein 1 (EGR-1). In addition, both in vitro and in vivo studies demonstrated that CeO2 NPs significantly induced the expression of sphingosine kinase 1 (SHPK1), phosphorylated Smad2/3 and lung fibrosis markers. Moreover, targeting SPHK1, TGFß receptor or Smad3 phosphorylation significantly attenuated the fibrosis-promoting effects of CeO2 NPs, and SPHK1-S1P pathway exerted a greater effect on the TGF-ß1-mediated lung fibrosis compared to the conventional Smad2/3 pathway. Collectively, our studies have identified the metabolomic changes in BEAS-2B cells exposed to CeO2 NPs with different aspect ratios and revealed the subtle changes in metabolic activities that traditional approaches might have missed. More importantly, we have discovered a previously unknown molecular mechanism underlying CeO2 NP-induced lung fibrosis with different aspect ratios, shedding new insights on the environmental hazard potential of CeO2 NPs.

Ultrasensitive SARS-CoV-2 diagnosis by CRISPR-based screen-printed carbon electrode.

Early and accurate diagnosis of SARS-CoV-2 was crucial for COVID-19 control and urgently required ultra-sensitive and rapid detection methods. CRISPR-based detection systems have great potential for rapid SARS-CoV-2 detection, but detecting ultra-low viral loads remains technically challenging. Here, we report an ultrasensitive CRISPR/Cas12a-based electrochemical detection system with an electrochemical biosensor, dubbed CRISPR-SPCE, in which the CRISPR ssDNA reporter was immobilized onto a screen-printed carbon electrode. Electrochemical signals are detected due to CRISPR cleavage, giving enhanced detection sensitivity. CRISPR-SPCE enables ultrasensitive SARS-CoV-2 detection, reaching as few as 0.27 copies µL-1. Moreover, CRISPR-SPCE is also highly specific and inexpensive, providing a fast and simple SARS-CoV-2 assay.

Chemically etched CeO2-x nanorods with abundant surface defects as effective cathode additive for trapping lithium polysulfides in Li-S batteries.

The commercialization of Li-S batteries has been seriously hindered by the notorious polysulfides shuttling and sluggish redox kinetics. To effectively address these technical issues, in this work, oxygen-deficient CeO2-x nanorods (NR) decorated on free-standing carbon cloth (CeO2-x NR@CC) were used as a promising dual-functional cathode host material to enhance the electrochemical and cycling performance of Li-S batteries. The oxygen-deficient CeO2-x NR were prepared in a facile processing route by tuning the surface structures of pristine CeO2 NR in strong reducing NaBH4 solution. In contrast to the pristine CeO2NR@CC control sample, chemically etched CeO2-x NR@CC with abundant implanted oxygen vacancies effectively trapped the polysulfides and dramatically accelerated electron charge transfer, leading to faster redox kinetics. The main working mechanism of CeO2-x NR@CC on the improved electrochemical performance was attributed to chemical binding effect on trapping lithium polysulfides and even promoting the conversion of polysulfides, thanks to reversible Ce3+/Ce4+ transformation, oxygen vacancies, and other surface defects. Hence, the CeO2-x NR@CC electrode delivered an outstanding initial capacity of 1358 mAh g-1 at 0.2C for the 1st cycle and a superb sulfur utilization of 81%, compared to an initial capacity of 1176 mAh g-1 at 0.2C and a sulfur utilization of 70% for the CeO2 NR@CC electrode. The improved electrochemical performances of the CeO2-x NR@CC electrode can be mainly attributed to the successful adsorption of more dissolvable polysulfides by the dual-functional cathode host materials that combine the physical confinement of conductive CC and the chemical binding of CeO2-x NR with ample surface defects.

Effects of chemical etching and reduction activation of CeO2 nanorods supported ruthenium catalysts on CO oxidation.

In this work, pristine and NaBH4 etched CeO2 nanorods supported ruthenium (Ru) catalysts were synthesized and employed to investigate the effects of chemical etching and reduction activation treatment on CO oxidation. With 1 wt% Ru loading, the CeO2 nanorods supported catalyst samples, after 6 wt% NaBH4 etching treatment, showed significantly promoted H2 consumption under 100 °C and low apparent activation energy (i.e., Ea âˆ¼ 31.2 kJ/mol) for CO oxidation. In-situ CO-DRIFTS profiles revealed that, for the reduced sample, the observed CO adsorption at âˆ¼ 2020 cm-1 at 40 °C may be related to a strong RuOx-CeO2 interaction induced by the NaBH4 etching treatment, which was supported by the oxygen vacancy analysis results of X-ray photoelectron spectroscopy and CO-temperature programmed desorption. The enriched surface defects on CeO2 support due to the chemical etching and reduction treatments are believed to promote the interaction between RuOx species and CeO2, which is responsible for the enhanced activity of CO oxidation.

Nanosized ZnIn2S4 supported on facet-engineered CeO2 nanorods for efficient gaseous elemental mercury immobilization.

Nanosized ZnIn2S4 supported on facet-engineered CeO2 nanorods were prepared by solvothermal method to effectively capture gaseous elemental mercury from flue gas. The CeO2/ZnIn2S4 sorbent exhibited excellent mercury removal performance (>90%) in a wide temperature range from 60 to 240 â„ƒ and showed much higher mercury adsorption capacity than pure CeO2 due to the enlarged specific surface area and abundant active oxygen and sulfur sites on the surface. It was found that CeO2/ZnIn2S4 has good resistance to SO2, NO and H2O. At the optimal 120 â„ƒ, the equilibrium Hg0 adsorption capacity of CeO2/ZnIn2S4 can reach 19.172 mg/g, which is superior to the reported series of benchmark materials. X-ray photoelectron spectroscopy and temperature programmed desorption of mercury confirmed that the adsorbed mercury existed on the surface as HgO and HgS, indicating that catalytic oxidation and chemisorption occurred on the surface of the adsorbent. The adsorption energy of Hg0 on the CeO2 (110) and ZnIn2S4 (110) surfaces calculated with density functional theory (DFT), further confirms that the surface activated oxygen and sulfur sites are the most stable adsorption sites. Furthermore, the good regeneration capability of CeO2/ZnIn2S4 makes it more promising for Hg0 capture in practical applications.

Multiwalled Carbon Nanotubes-CeO2 Nanorods: A "Nanonetwork" Modified Electrode for Detecting Trace Rifampicin.

Herein, a "nanonetwork" modified electrode was fabricated based on multiwalled carbon nanotubes and CeO2 nanorods. Scanning electron microscopy, X-ray powder diffraction and zeta potential were employed to characterize this electrode. Multiwalled carbon nanotubes negatively charged and CeO2 nanorods positively charged form "nanonetwork" via electrostatic interaction. The performance of the CeO2 nanorods-based electrode remarkably improved due to the introduction of multiwalled carbon nanotubes. The detection of rifampicin (RIF) was used as a model system to probe this novel electrode. The results showed a significant electrocatalytic activity for the redox reaction of RIF. Differential pulse voltammetry was used to detect rifampicin, the reduction peak current of rifampicin linear with the logarithm of their concentrations in the range of 1.0 × 10-13-1.0 × 10-6 mol/L, The linear equation is ip = 6.72 + 0. 46lgc, the detect limit is 3.4 × 10-14 mol/L (S/N = 3). Additionally, the modified electrode exhibits enduring stability, excellent reproducibility, and high selectivity. This strategy can be successfully used to detect trace rifampicin in samples with satisfactory results.

Hot Electrons, Hot Holes, or Both? Tandem Synthesis of Imines Driven by the Plasmonic Excitation in Au/CeO2 Nanorods.

Solar-to-chemical conversion via photocatalysis is of paramount importance for a sustainable future. Thus, investigating the synergistic effects promoted by light in photocatalytic reactions is crucial. The tandem oxidative coupling of alcohols and amines is an attractive route to synthesize imines. Here, we unravel the performance and underlying reaction pathway in the visible-light-driven tandem oxidative coupling of benzyl alcohol and aniline employing Au/CeO2 nanorods as catalysts. We propose an alternative reaction pathway for this transformation that leads to improved efficiencies relative to individual CeO2 nanorods, in which the localized surface plasmon resonance (LSPR) excitation in Au nanoparticles (NPs) plays an important role. Our data suggests a synergism between the hot electrons and holes generated from the LSPR excitation in Au NPs. While the oxygen vacancies in CeO2 nanorods trap the hot electrons and facilitate their transfer to adsorbed O2 at surface vacancy sites, the hot holes in the Au NPs facilitate the α-H abstraction from the adsorbed benzyl alcohol, evolving into benzaldehyde, which then couples with aniline in the next step to yield the corresponding imine. Finally, cerium-coordinated superoxide species abstract hydrogen from the Au surface, regenerating the catalyst surface.

Pressure Regulations on the Surface Properties of CeO2 Nanorods and Their Catalytic Activity for CO Oxidation and Nitrile Hydrolysis Reactions.

Surface properties of nanoscale CeO2 catalysts in terms of the surface Ce(3+) fraction and concentration of oxygen vacancy can affect their catalytic performance significantly. Continual adjustment on surface properties of CeO2 with the morphological preservation has not been realized by synthetic methods. The revisited studies show that surface properties of CeO2 nanorods can be effectively regulated by synthetic pressures while the rodlike morphology is well-preserved. Such phenomena are ascribed to the contact possibility between Ce(3+) species and dissolved O2, which is balanced by the rapidly increased and gradually saturated dissolution/recrystallization rate of Ce(OH)3 and linearly increased concentration of dissolved O2 with the increase of total air pressure or partial pressure of O2. Surface-property-dependent catalytic activity of CeO2 nanorods synthesized under various pressures was also demonstrated in two benchmark reactions-catalytic oxidation of CO and hydrolysis of nitrile. Such a finding of the pressure regulation on the reducible metal oxides provides an effective approach to rationally design novel catalysts for specific reactions, where ceria are supports, promoters, or actives.

Enhanced peroxidase-like activity of porphyrin functionalized ceria nanorods for sensitive and selective colorimetric detection of glucose.

Ceria nanorods modified with 5,10,15,20-tetrakis(4-carboxyl phenyl)-porphyrin (H2TCPP) were prepared. These nanocomposites (H2TCPP-CeO2) exhibited the intrinsic peroxidase-like activity and could catalyze the oxidation of classical peroxidase substrate 3,3',5,5'-tetramethylbiphenyl dihydrochloride (TMB·2HCl) in the presence of H2O2 to produce a typical color reaction from colorless to blue. Our results demonstrated that both the H2TCPP-CeO2 nanocomposites and CeO2 nanorods exhibited higher thermal durance than that of HRP. The affinity of The H2TCPP-CeO2 nanocomposites toward H2O2 and TMB is similar to that of HRP. Fluorescent results indicated that the catalytic mechanism of the H2TCPP-CeO2 nanocomposites were from the decomposition of H2O2 into hydroxyl radicals. Based on these studies, a simple, sensitive, and selective visual and colorimetric method using TMB as the substrate was designed to detect glucose when combined with glucose oxidase. The proposed colorimetric method can detect H2O2 at a low detection limit of 6.1×10(-6)M and a dynamic range of 10(-5)-10(-4)mol·L(-1). This method can also detect glucose at a low detection limit of 3.3×10(-5)mol·L(-1) and a dynamic range of 5.0×10(-5)-1.0×10(-4)mol·L(-1).