Cerium ions crosslinked sodium alginate-carboxymethyl chitosan spheres with antibacterial activity for wound healing

For wound healing,wound infection caused by bacteria is one of the important reasons that delay wound healing process.Therefore,it is very meaningful to develop a multifunctional wound dressing with antibacterial capability to accelerate wound healing.Sodium alginate(SA)and carboxymethyl chitosan(CMCS)are the most commonly used compositions in wound dressing,but their poor stability inhibits the further applications.Introducing CMCS and using cerium ions(Ce^(3+))to crosslink CMCS and SA to form SA-CMCS hybrid spheres by electrostatic spray method,can not only improve the stability of SA hydrogels,but also endow the spheres with excelle nt antibacterial properties due to the characteristics of Ce^(3+).The gradual release of Ce^(3+)from the SA-CMCS spheres can effectively inhibit the growth of Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli).Combining the wound healing promotion ability of SA and CMCS,this kind of wound dressing can not only avoid wound infection caused by bacteria effectively,but also accelerate wound healing,thus it is an easily prepared material with potential applications in skin defect repair.

Mechanism of Cerium Ions Scavenging Superoxide Radical

The mechanism of cerium ions scavenging superoxide radical(O÷2) has been studied. The results show that (1) Ce^3+ can reduce O÷2 to H_2O_2 while it is oxidized to Ce^4+; (2) Ce^4+ can oxidize O÷2 to O_2 while it is reduced to Ce^3+.

EFFECT OF CERIUM ION IMPLANTATION ON THE AQUEOUS CORROSION BEHAVIOR OF ZIRCONIUM

In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted by cerium ions with a dosage range from 1×1016 to 1×1017 ions/cm2 at about 150℃, using MEVVA source at an acceler ative voltage of 40kV. The valence of the surface layer was analyzed by X-ray photo- electron spectroscopy (XPS); Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zirconium in a 0.5mol/L H2SO4 solution. It was found that a remarkable decline in the aqueous corrosion behavior of zirconium implanted with cerium ions compared with that of the as-received zirconium. Finally, the mechanism of the corrosion resistance decline of the cerium-implanted zirconium is discussed.

Effect of cerium ion on the proliferation,differentiation and mineralization function of primary mouse osteoblasts in vitro

The effects of cerium ion(Ce3+) on the proliferation,differentiation,adipocytic transdifferentiation and mineralization function of primary mouse osteoblasts(OBs) were investigated.The results indicated that Ce3+ at all concentrations(1×10-9,1×10-8,1×10-7,1×10-6,1×10-5,and 1×10-4 mol/L) promoted the proliferation of osteoblasts(OBs).On day 1 and 3,Ce3+ promoted the differentiation of OBs at concentrations of 1×10-9,1×10-7,and 1×10-6 mol/L,but inhibited the differentiation of OBs at higher concentrations.On ...

Kinetics and Mechanism of Iridium(Ⅲ)-Catalyzed Oxidation of Ethanol Amine by Cerium(Ⅳ) in Sulfuric Acid Media

In this study, the kinetics and mechanism of the iridium（ Ⅲ ） -catalyzed oxidation of ethanol amine（EAN） by cerium（Ⅳ） in a sulfuric acid medium was investigated using titrimetric technique of redox in a temperature range of 298--313 K. It was found that the reaction is of first order with respect to Ce（ Ⅳ ） and It（ Ⅲ ）, and a positive fractional order with respect to EAN. It was also found that the pseudo-first-order （ [EAN ] 〉〉 [ Ce （ Ⅳ） ] ） rate constant koba decreases with the increase of [ H^＋ ] and [ HSO^-4 ]. Under the protection of nitrogen gas, the reaction system can initiate the polymerization of acrylonitrile, indicating the generation of free radicals. On the basis of the experimental results, a suitable mechanism was proposed. From the dependence of koba on the concentration of hydrogen sulfate, Ce（SO4）2 was found to be the kinetically active species. The rate constants of the rote-determining step together with the activation parameters were evaluated.

Spectral Characteristics and Its Regularity of Rare Earth Ions in Inorganic Microporous Material Ⅲ．Spectral Characteristics of Ce^（3＋） in Zeolite Hosts

In hydrated NaY、NaX and NaA zeolites,the covalent nature of Ce-O bond is weakened progressively,and this causes the centroid of 5 d band raising.Further,the emission peak of Ce3+ ion shifts to a shorter wavelength.There are two Ce3+ emission centers in calcined NaX and NaA zeolites.The strength of the crystal field at the two kinds of Ce3+ centers are much different,so the positions of their transition emission peaks vary quite considerably.There is only one kind of Ce3+ center in calcined NaY zeolite.

Radiation induced color centers in cerium-doped and cerium-free multicomponent silicate glasses

The effect of doped cerium on the radiation-resistance behavior of silicate glass was investigated in our work. The ultraviolet-visible absorption spectra and electron paramagnetic resonance（EPR） spectra were obtained after the cerium-rich and cerium-free multicomponent silicate glasses（K509 and K9） were irradiated by gamma rays with a dose range from 10 to 1000 kGy. The results showed that E’ center, oxygen deficient center（ODC） and non-bridging oxygen hole center（HC1 and HC2） were induced in K9 and K509 glasses after radiation. The concentrations of all color centers presented an exponential growth with the increase of the gamma dose. Moreover, the concentration of HC1 and HC2 in cerium-doped K509 glass was much lower than that in cerium-free K9 glass at the same dose of radiation, which could be attributed to the following mechanism： Ce3＋ ions capturing holes then forming Ce3＋＋ centers inhibited the formation of hole trapped color centers（HC1 and HC2） and Ce4＋ ions capturing electrons to form Ce3＋ centers suppressed the formation of electron trapped color centers like E’ center.

Nature of cerium on improving low-temperature hydrothermal stability of SAPO-34

To probe the function of Ce on enhancing low-temperature stability of SAPO-34,Ce/SAPO-34 with different Ce contents was prepared via one-pot method and further treated at 70℃in 80%relative humidity for 24 h.The structural results prove that the one-pot synthesis is an effective way to introduce Ce(Ce<0.325 wt%)without influencing micro-structural and chemical composition.The lowtemperature hydrothermal stability of Ce/SAPO-34 is enhanced by Ce loading.More than 92%CHA structure and total acidity are maintained over 0.188 wt%Ce/SAPO-34,while only about 20%of that left on pure H/SAPO-34.As Ce exists as Ce^(3+)at exchange sites on the surface of SAPO-34,the results of the linear relationship between protected surface acidity and structure/acidity conservation manifest that Ce^(3+))effectively hinders the structural collapse.This study provides new insight into surface acidity protection for solving the problem of low-temperature hydrothermal stability of SAPO-34.

A comparison between Ce(Ⅲ) and Ce(Ⅳ) ions in photocatalytic degradation of organic pollutants

Nano cerium oxides are efficient photocatalysts for pollutants degradation with highly dispersed Ce（III） ions as the suggested active species to promote the reaction, while Ce（IV） species do not behave as a catalyst. In this paper, to understand the mechanism of Ce-based photocatalysts, we studied the comparison of simple cerium ions, Ce（III） and Ce（IV） in aqueous solution for organic pollutants degradation under UV irradiation. Orange II（AOII）, methyl orange, and p-nitrophenol were selected as the target pollutants. The formation and contribution of reactive oxygen species, the kinetics of Ce（IV） photoreduction and Ce（III） photooxidation, and the influence of solution p H were investigated in detail. It was found that at low p H Ce（IV） ions showed a higher activity for hydroxyl radicals production and AOII degradation than Ce（III） ions, which could be attributed to its fast reduction rate to Ce（III）. However, its activity dramatically decreased when solution p H increased, and was also strongly influenced by the type of pollutants; while Ce（III） exhibited high degradation efficiency of all the tested pollutants over a wide pH range.

Synthesis, characterization and antimicrobial activity of zinc and cerium co-doped α-zirconium phosphate

A series of zinc ions or/and cerium ions co-doped a-zirconium phosphate （Zn-Ce@ZrPs） were prepared. The novel Zn-Ce@ZrPs were characterized and the antibacterial activity on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were tested. The results showed that zinc ions （Zn2＋） or/and cerium ions （Ce3＋） were combined with ZrP, and the Ce3＋ was adsorbed on the surface of ZrP through hydrogen bonds, while Zn2＋ intercalated into the interlayer of ZrP. Zn-Ce@ZrPs showed excellent synergistic antibacterial activity. When Zn2＋/Ce3＋ atomic ratio was 0.6, the Zn-Ce@ZrP3 showed the highest synergistic antibacterial efficiency, suggesting great potential ap- plication as antibacterial agents in microbial control.

Structure and synergetic antibacterial effect of zinc and cerium carried sodium zirconium phosphates

Zinc and cerium carried zirconium phosphates （Zn-Ce/ZrPs） were prepared by exchanging zinc and cerium cations into sodium zirconium phosphate （NaZrP） through the ion-exchange method and characterized by X-ray diffraction（XRD）, energy dispersive X-ray spectroscopy （EDX） and scanning electron microscopy （SEM）. Furthermore, the specific surface area, zeta potential and antibacterial activity were tested. The results showed that Zn-Ce/ZrPs were with hexagonal crystal system, and the surface area of Zn-Ce/ZrPs increased much more than that of NaZrP. Zn-Ce/ZrPs showed obvious synergetic antibacterial effect, and have the potential to be used as antibacterial agents in environmental control.

Effect of Ce^(3+) on membrane permeability of Escherichia coli cell

This study aimed to delineate the antibacterial mechanism of rare-earth ion Ce3＋ to the target organism Escherichia coil cell, and the most important purpose was to identify its biological effect of increasing the E. coli cell membrane permeability. The antibacterial activi- ties of Ce3＋ to E. coli cells were tested, and then the permeability of outer membrane （OM） and inner membrane （IM） were studied by N-phenyl-l-naphthylamine （NPN） and o-nitrophenyl-β-D-galactopyranoside （ONPG） methods separately. Through these experiments we concluded that the E. coli cells grown to log phage were more sensitive to Ce3＋ than the ones not at this stage; the structure of membrane was destroyed and the permeability of both OM and IM was obviously increased by Ce3＋; there should be certain interactions between Ce3＋ and some proteins inside the cell, which impeded the physiological activities of bacteria.

A fluorescent probe based on a spiropyran for sensitive detection of Ce^3+ ion

A spiropyran-based probe was developed.It serves as a fluorescence turn-on probe for selective detection of Ce^3+in both ethanol and aqueous(water/ethanol,1:9 or 9:1,v/v)media.Ce3+can induce photochromism of the probe though the probe exhibits negligible photochromic property by itself.The probe is sensitive to Ce3+and the detection limit reaches 1.7μmol/L.It exhibits a high selectivity for Ce^3+ion over other common metal cations including Li^+,Na^+,Ag^+,Sr^2+,Ni^2+,Co^2+,Hg^2+,Zn^2+,Cr^3+,Al^3+,Fe^3+and Bi^3+and lanthanide ions Nd^3+,Yb^3+and La^3+.The probe may be used for quantitative determination of the concentration of Ce3+ion in a range of 1-10μmol/L and for application to environmental water samples.Sensing mechanism of the probe towards Ce3+ion is proposed.