Morphology Controlling of the Ultrafine Cerium Dioxide (CeO_2) Precursor

The synthesis of ultrafine cerium dioxide precursor via homogeneous precipitation was studied. Mixed aqueous solution of anhydrous cerium nitrate and urea was first heated to 85℃ for 2 h, and the prepared suspension was then aged at room temperature for various periods of time. White precipitate was finally collected by centrifuging and washed with distilled water and anhydrous ethanol. The obtained cerium dioxide (CeO2) precursor was observed with SEM. It was found that the morphology and size of the precursor were strongly affected by aging time and stirring conditions (with or without stirring). The precipitated fine spherical particles of the precursor changed their shape from ellipse to slice or directly to slice. Fine spherical monodispersed (300 nm) precursor powders could be obtained by controlling the aging time. Stirring the solution also could change the reaction process and thus the morphology and size of the precursor were changed.

Principle and Process Window of Cerium Dioxide Thin Film Fabrication with Dual Plasma Deposition

Cerium dioxide, CeO2, is a potentially superior material in a myriad of areas, and many methods have been proposed to deposit single crystal CeO2 thin films. A novel fabrication technique utilizing dual plasma generated by metal vacuum arc (MEVVA) and radio frequency (RF) is discussed in this paper. We have recently conducted a systematic investigation to determine the optimal process window to deposit CeO2 thin films'on Si(100) substrates. The X-ray diffraction results show the existence of CeO2(100) in the as-deposited sample.

Towards wafer-scale growth of two-dimensional cerium dioxide single crystal with high dielectric performance

Owing to the atomically thin nature,two-dimensional(2D)oxide materials have been widely reported to exhibit exciting transport and dielectric properties,such as fine gate controllability and ultrahigh carrier mobility,that outperform their bulk counterpart.However,unlike the successful synthesis of bulk oxide single crystals,reliable methods for synthesizing large-area single crystal of 2D oxide,that would suppress the negative influence from defective grain boundaries,remain unavailable,especially for nonlayered oxide.Herein,we report that the lattice symmetry between the substrate and cerium dioxide(CeO_(2))would allow for the aligned nucleation and epitaxial growth of CeO_(2)on sapphire substrates,enabling the wafer-sized growth of CeO_(2)single crystal.The careful tuning of the growth temperature and oxygen flow rate contributed to the harvesting of CeO_(2)wafer with reduced thickness and enhanced growth rates.The removal of grain boundaries improved the dielectric performance in terms of high dielectric strength(E_(bd)≈8.8 MV·cm^(-1)),suppressed leakage current,along with high dielectric constants(ε_(r)≈24).Our work demonstrates that with fine dielectric performance and ease of synthesizing wafer-sized single crystals,CeO_(2)can function as potential candidate as gate insulator for 2D-materials based nanoelectronics,and we believe the reported protocol of aligned nucleation can be extended to other 2D oxides.

Preparation of Cerium Dioxide Functionalized Magnetic Layered Double Hydroxides for High-efficiency Phosphopeptide Enrichment

In this work,we prepared a material with magnetic nanoparticles(Fe_(3)O_(4))as core,layered double hydroxides(LDHs)as affinity shell,and cerium dioxide(CeO_(2))as functional molecules(denoted as Fe_(3)O_(4)@LDH-CeO_(2)).On the basis of combined immobilized metal ion affinity chromatography(IMAC)and metal oxide affinity chromatography(MOAC),Fe_(3)O_(4)@LDH-CeO_(2) was used to enrich phosphopeptides with high efficiency.The material exhibited high selectivity(α-casein:β-casein:BSA=1:1:5000,mass ratio),high recovery(95.87%),and good reusability of 10 times adsorption-desorption experiments.The feasibility of Fe_(3)O_(4)@LDH-CeO_(2) was further investigated by extracting phosphopeptides from biological samples(nonfat milk,serum,saliva,and A549 cell lysate).

Cerium dioxide as a new reactive sorbent for fast degradation of parathion methyl and some other organophosphates

Cerium dioxide was used for the first time as reactive sorbent for the degradation of the organophosphate pesticides para-thion methyl, chlorpyrifos, dichlofenthion, fenchlorphos, and prothiofos, as well as of some chemical warfare agents-nerve gases soman and O-ethyl S-[2-（diisopropylamino） ethyl] methylphosphonothioate （VX）. CeO2 specimens were prepared by calcination of basic cerous carbonate obtained by precipitation from an aqueous solution. The CeO2 samples containing certain amounts （1 wt.%-5 wt.%） of the neighboring lanthanides （La, Pr, Nd） were prepared in a similar way from pure lanthanide salts. It was shown that ceria accelerated markedly the decomposition of parathion methyl causing the cleavage of the P-O-aryl bond in the pesticide molecule. A similar reaction mechanism was proposed for the degradation of other organophosphate pesticides and nerve agents. The degradation times （reaction half-times） were in an order of minutes in the presence of CeO2, compared to hours or days under common environ-mental conditions. The reaction in suitable organic solvents allowed conversions of about 90%for parathion methyl loading of 20 mg pesticide/g CeO2 within 2 h with a reactant half-life in the order of 0.1 min. The key parameter governing the degradation efficiency of CeO2 was the temperature during calcination. At optimum calcination temperature （about 773.15 K）, the produced ceria retained a sufficiently high surface area, and attained an optimum degree of crystallinity （related to a number of crystal defects, and thus poten-tial reactive sites）. The presence of other lanthanides somewhat decreased the reaction rate, but this effect was not detrimental and permitted the possible use of chemically impure ceria as a reactive sorbent. A fast organophosphate degradation was demonstrated not only in non-polar solvents （such as heptane）, but also in polar aprotic solvents （acetonitrile, acetone） that are miscible with water. This opens new possibilities for designing more versatile decontamination strategies. The cleavage of phosphate ester bonds is of a great importance not only for the degradation of dangerous chemicals （chemical weapons, pesticides）, but also for interactions of ceria （es-pecially the nano-sized one） in biologically relevant systems.

Inhibition of bromate formation by reduced graphene oxide supported cerium dioxide during ozonation of bromidecontaining water

Ozone(O3)is widely used in drinking water disinfection and wastewater treatment.However,when applied to bromide-containing water,ozone induces the formation of bromate,which is carcinogenic.Our previous study found±at graphene oxide(GO)can enhance the degradation efficiency of micropollutants during ozonation.However,in this study,GO was found to promote bromate formation during ozonation of bromide-containing waters,with bromate yields from the O3/GO process more than twice those obtained using ozone alone.The promoted bromate formation was attributed to increased hydroxyl radical production,as confirmed by the significant reduction(almost 75%)in bromate yield after adding t-butanol(TBA).Cerium oxide(less tfian 5 mg/L)supported on reduced GO(xCeO2/RGO)significantly inhibited bromate formation during ozonation compared with reduced GO alone,and the optimal Ce atomic percentage(x)was determined to be 0.36%,achieving an inhibition rate of approximately 73%.Fourier transform infrared(FT-IR)spectra indicated the transformation of GO into RGO after hydrothermal treatment,and transmission electron microscope(TEM)results showed that CeO2 nanoparticles were well dispersed on the RGO surface.The X-ray photoelectron spectroscopy(XPS)spectra results demonstrated that the Ce^3+/Ce^4+ratio in xCeO2/RGO was almost 3-4 times higher than that in pure CeO2,which might be attributed to the charge transfer effect from GO to CeO2.Furthermore,Ce+on thexCeO2/RGO surface could quench Br-and BrO-to further inhibit bromate formation.Meanwhile,0.36CeO2/RGO could also enhance the degradation efficiency of N,N-diethyl-zn-toluamide(DEET)in synthetic and reclaimed water during ozonation.

ROS Balance Autoregulating Core-Shell CeO_(2)@ZIF-8/Au Nanoplatform for Wound Repair

Reactive oxygen species(ROS)plays important roles in living organisms.While ROS is a double-edged sword,which can eliminate drug-resistant bacteria,but excessive levels can cause oxidative damage to cells.A core–shell nanozyme,Ce O_(2)@ZIF-8/Au,has been crafted,spontaneously activating both ROS generating and scavenging functions,achieving the multifaceted functions of eliminating bacteria,reducing inflammation,and promoting wound healing.The Au Nanoparticles(NPs)on the shell exhibit high-efficiency peroxidase-like activity,producing ROS to kill bacteria.Meanwhile,the encapsulation of Ce O_(2) core within ZIF-8 provides a seal for temporarily limiting the superoxide dismutase and catalase-like activities of Ce O_(2) nanoparticles.Subsequently,as the ZIF-8 structure decomposes in the acidic microenvironment,the Ce O_(2) core is gradually released,exerting its ROS scavenging activity to eliminate excess ROS produced by the Au NPs.These two functions automatically and continuously regulate the balance of ROS levels,ultimately achieving the function of killing bacteria,reducing inflammation,and promoting wound healing.Such innovative ROS spontaneous regulators hold immense potential for revolutionizing the field of antibacterial agents and therapies.

Enhanced corrosion resistance of epoxy resin coating via addition of CeO_(2) and benzotriazole

The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied.In this work,cerium dioxide(CeO_(2))and benzotriazole(BTA)were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel.Scanning electron microscopy results indicated that the CeO_(2) grains were rod-like and ellipsoidal in shape,and the distribution pattern of BTA was analyzed by energy dispersive spectroscope.The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO_(2) and BTA co-addition,and electrochemical impedance spectroscopy test analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating.And the optimal protective performance was provided by the coating containing 0.3%(mass)CeO_(2) and 20%(mass)BTA,which was attributed to the barrier performance of CeO_(2) particles and the chemical barrier effect of BTA.The formation of corrosion products was analyzed using X-ray diffraction.In addition,the corrosion resistance mechanism of the coating was also discussed in detail.

Optimal Conditions for Preparing Ultra-Fine CeO_2 Powders in A Submerged Circulative Impinging Stream Reactor

Cerium carbonate powders were produced in a submerged circulation impinging stream reactor （SCISR） from Ce（NO3）3· 6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide （CeO2） powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce（NO3）3 and NH4HCO3 solutions were 02,5 and 0.3 mol · L^-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g · L^-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r · min^- 1,80 ℃, 20 min, 5 - 6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8 -2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point 5 group was OH^5-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor （STR）.

A DFT+U study of the structures and reactivities of polar CeO_2(100) surfaces

Density functional theory calculations corrected by on-site Coulomb interactions were carried out o study the structures of polar CeO2 （100） surfaces as well as activities during catalytic CO oxidation. The stabilities of various CeO2 （100） termination structures are discussed, and calculated energetics are presented. The most stable Ce〇2 （100） surface was obtained by removing half the outermost full layer of oxygen and the surface stability was found to decrease as the exposed oxygen concentration was increased. Assessing the reaction pathways leading to different final products during CO oxidation over the most stable CeO2 （100） surface, we determined that the formation of carbonate species competed with CO2 desorption. However, during CO oxidation on the less stable CeO2 （100） surfaces having more exposed oxygen, the CO is evidently able to react with surface oxygen, leading to CO2 formation and desorption. The calculation results and electronic analyses reported herein also indicate that the characteristic Ce 4/ orbitals are directly involved in deter-mining the surface stabilities and reactivities.

MORPHOLOGY CONTROL OF ULTRAFINE CeO_2 AND ITS POLISHING EFFICACY

Homogenous precipitation and subsequent calcination has been used tosynthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from theprecursor inherit the size and morphology of it. The size and morphology of the precursor areclosely related to the preparation process. The morphology, size and distribution of the precursorcould be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sizedspherical particles is prepared by this method. The powder is used in the chemical-mechanicalpolishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measuredby AFM.

Fabrication of mono-dispersed cerium oxide nanopowders via mixed solvothermal route

Monodisperse and single-phase cerium oxide nanopowders were synthesized by mixed solvothermal route,Ce(NO3) 3·6H2O as raw materials,poly(vinylpyrrolidone) (PVP) as stable agent. The cerium oxide nanopowders could be controlled from 50 to 60 nm by adjusting the ratio between ethanol absolute and water at 160 °C. With methanol instead of ethanol absolute,the reaction temperature could be lowered to 130 °C.

Photothermal effective CeO_(2)NPs combined in thermosensitive hydrogels with enhanced antibacterial,antioxidant and vascularization performance to accelerate infected diabetic wound healing

Chronic diabetic wound healing remains a formidable challenge due to susceptibility to bacterial infection,excessive oxidative stress,and poor angiogenesis.To address these issues,a sodium alginate(SA)based photothermal hydrogel dressing with multifunction was fabricated to facilitate wound treatment.Ceria nanoparticles(CeO_(2)NPs)was synthesized,and their antibacterial performance by near-infrared light triggered photothermal effects was first studied and verified in this work.In addition,to release CeO_(2)NPs to achieve antioxidation and pro-vascularization,thermosensitive gelatin(Gel)was utilized to embed the nanoparticles in advance and then composited in SA hydrogel networks.SA network was finally strengthened by acid soaking to form partially crystalline regions to act as natural crosslinkers.Results showed that the Gel/SA/CeO_(2)hydrogel displayed temperature-responsive release of CeO_(2)NPs,significant antibacterial and antioxidative activity,as well as the ability to remove without injury and promote infected diabetic wound healing with low cytotoxicity,according to antibacterial investigations,cell studies,and in vivo animal studies.This research offers not only a successful method for quickening the healing of diabetic wounds but also a fresh approach to the general use of CeO_(2)NPs.

CeO_(2)-clay composites for ultra-long cycle life electrochemical capacitive energy storage application

The lattice expansion caused by the reduction of Ce(Ⅳ)to Ce(Ⅲ)impeded the development of the CeO_(2)as an effective electrode material for electrochemical supercapacitors.Herein,we prepared CeO_(2)-clay composites through a one-step hydrothermal method.The interlayer structures of clays efficiently accommodate volume changes induced by crystal lattice expansion to achieve ultra-long cycle stability.After 60000 charge-discharge cycles,the capacitance retention rate of the assembled asymmetric supercapacitors is as high as~-100%.The key findings of this work reveal the potential application of clays in achieving ultralong cycle stability of the CeO_(2)electrode material,paving the way for further application of the CeO_(2)in electrochemical energy storage.

Integrating ceria with cobalt sulfide as high-performance electrocatalysts for overall water splitting

The development of bifunctional electrocatalysts for overall water splitting is highly desired for converting electricity into chemical energy.However,the synthesis of high-performance bifunctional electrocatalysts remains a pressing challenge.Here,we found that both the oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)performance of the Co_(3)S_(4) electrode can be significantly improved by integration with CeO_(2).Specifically,as-prepared 5%Ce-Co_(3)S_(4) and 1%Ce-Co_(3)S_(4) delivered low overpotentials of 290 and 257 mV to achieve 10 mA cm^(-2) for the OER and HER in 1.0 M KOH,respectively.The crucial role of CeO_(2) originated from its unique surface with abundant oxygen vacancies,which were beneficial for the stabilization of Co^(2+)sites with high OER activity and both the adsorption and dissociation of water molecules in the HER process.This work is expected to provide a general approach to prepare a wide range of high-performance electrode materials for energy-related applications.

Enhancing low-temperature NH_(3)-SCR performance of Fe-Mn/CeO_(2)catalyst by Al_(2)O_(3)modification

In the work,supported catalysts of FeO_(x) and MnO_(x) co-supported on aluminum-modified CeO_(2)was synthesized for low-temperature NH_(3)-selective catalytic reduction(NH_(3)-SCR)of NO.Impressively,the SCR activity of the obtained catalyst is markedly influenced by the adding amount of Al and the appropriate Ce/Al molar ratio is 1/2.The activity tests demonstrate that Fe-Mn/Ce1 Al2 catalyst shows over 90%NO conversion at 75-250℃and exhibits better SO_(2)resistance compared to Fe-Mn/CeO_(2).Fe-Mn/Ce1 Al2 shows the expected physicochemical characters of the ideal catalyst including the larger surface and increased active reaction active sites by controlling the amount of Al doping.Also,the better catalytic activity is well correlated with the present advantaged surface adsorption oxygen species,Mn^(4+)species,Ce^(3+)species and the enhanced reducibility of Fe-Mn/Ce1 Al2,which is superior to the Fe-Mn/CeO_(2)catalyst.More importantly,we further demonstrate that the amount and strength of surface acid sites are improved by Al-doping and more active intermediates(monodentate nitrate)is generated during NH_(3)-SCR reaction.This work provides certain insight into the rational creation of simple and practical denitration catalyst environmental purification.

Preparation,characterization and catalytic oxidation property of CeO_2/Cu^(2+)-attapulgite (ATP) nanocomposites

Cerium oxide(CeO2) coated on copper modified attapulgite clay nanocomoposite(CeO2/Cu2+-ATP) was prepared by homogeneous deposition method.The microstructures of the as-prepared CeO2/Cu2+-ATP nanocomposites were characterized by X-ray diffraction(XRD),energy-dispersive spectrometer(EDS) and transmission electron microscopy(TEM).The results indicated that CeO2 particles with average size of about 5 nm were loaded onto the Cu2+-ATP and were widely dispersed.Comparing the catalytic activity of ATP/CeO2 and CeO2/Cu2+-ATP,the catalytic activity was improved when a small quantity of Cu2+ was introduced.The loading amount of CeO2 and reaction temperature had important effects on decolorization ratio of methyl orange(MO).When the loading amount and reaction temperature were 70% and 338 K,respectively,the decolorization ratio of MO reached over 99%,which showed excellent catalytic activity.

Influence of Cl substitution on the electronic structure and catalytic activity of ceria

Cl-containing cerium dioxide(Ce O2) catalysts have been found to exhibit unique catalytic activities. In the present work, using density functional theory calculations with the inclusion of on-site Coulomb correction, we systematically studied the effect of Cl on the physicochemical properties of Ce O2 surfaces by substituting one subsurface O with Cl. The calculated results show that substituting an O atom with a Cl atom results in structural distortion and the reduction of one surface Ce4+ cation to Ce3+. The protruding Ce3+ cation greatly improves the adsorption energy of O2 to produce an active O2- species, and maintains the catalytic oxidation cycle of CO on Ce O2(110). These results may help us obtain a better understanding of Cl-ceria interacting systems and provide some guidance for the design of effective Ce O2-based catalysts.

In-situ TEM study on the evolution of dislocation loops and bubbles in CeO_(2)during Kr^(+)single-beam and Kr^(+)-H_(2)^(+)dual-beam synergetic irradiation

CeO_(2)is widely used as the nonradioactive surrogate fuel of UO_(2)when studying the irradiation performance of UO_(2).The evolution and characteristics of dislocation loops and bubbles in CeO_(2)foils were studied by in-situ transmission electron microscopy(TEM)observation during 400 ke V Kr^(+)&30 ke V H_(2)^(+)dual-beam synergetic irradiation and 400 ke V Kr^(+)single-beam irradiation at 1073 K.The rotation of the habit plane of dislocation loops induced by above ion irradiation was found in the CeO_(2)for the first time,such as from[211]to[311]and then to[100].The rafted loops were first observed under Kr^(+)&H_(2)^(+)dual-beam synergetic irradiation,which not only had similar[111]direction,but also belonged to perfect dislocation loops(PDLs).The rafted loops were formed not only by the growth of loops that absorbed irradiation defects,but also by the combination of loops.But,this phenomenon of loop rafting was not obvious during Kr single-beam irradiation.It was first found that Kr^(+)irradiation induced the change of Burgers vectors of PDLs.The absorption of large PDLs to small PDLs was also observed.The average size and areal number density of dislocation loops and gas bubbles as a function of irradiation dose were constructed,which showed that the addition of H_(2)^(+)obviously affected the characteristics of dislocation loops and gas bubbles and the swelling of CeO_(2).

Generation of Methyl Vinyl Ketone from Oxidation of Levulinic Acid Oxidized by Cupric Oxide Complex

Methyl vinyl ketone （MVK） is a kind of high-value chemical which has been widely used in many fields. In this paper, it is formed from oxidation of levulinic acid--a hydrolysis product of biomass. Copper oxide supported on cerium dioxide （CuO/CeO2） and alumina （CuO/AI203） were prepared and used for the oxidation of levulinic acid （LA）. The oxidants were characterized by means of X-ray diffraction （XRD）, H2-temperature programmed reduction （H2-TPR） and atomic force microscope （AFM） techniques. CuO/CeO2 and CuO/A1203 show a different behav- ior with respect to pure CuO. The experiments revealed that CuO/CeO2 and CuO/AI203 can oxidize LA and get methyl vinyl ketone [yield of 15.5% detected by head space-gas chromatograph-mass spectrometer （HS-GC-MS）] under mild reactive conditions, while pure CuO oxidizes LA to produce butanone （MEK）.