Application of Nano Structured CA Doped CeO2 for Ultraviolet Filtration

8/6/2019 Application of Nano Structured CA Doped CeO2 for Ultraviolet Filtration

http://slidepdf.com/reader/full/application-of-nano-structured-ca-doped-ceo2-for-ultraviolet-filtration 1/9

Application of nanostructured Ca doped CeO2 for ultraviolet filtration

Laurianne Truf fault a,*, Minh-Tri Ta a, Thierry Devers a, Konstantin Konstantinov b,Valerie Harel a, Cyriaque Simmonard a, Caroline Andreazza c, Ivan P. Nevirkovets b,Alain Pineau c, Olivier Veron a, Jean-Philippe Blondeau a

a Institute PRISME, site de Chartres, EA 4229 Universite d’Orle ans, 21 rue de Loigny la Bataille, 28000 Chartres, Franceb Institute for Superconducting & Electronic Materials, University of Wollongong, NSW 2522, AustraliacCentre de Recherche sur la Matie re Divise e, UMR 6619-CNRS, 1b rue de la Fe rollerie, 45071 Orle ans Cedex 2, France

1. Introduction

Recently, CeO2 has been the subject of many studies regarding

its use as a catalyst [1], polishingagent [2], or potential material for

ultraviolet (UV) filtration [3,4]. In the UV radiation range reaching

the Earth’s atmosphere, the ultraviolet type B sub-range (UVB,

290–320 nm) is already well filtered by nanostructured TiO2 in

sunscreen cosmetic products. The ultraviolet type A (UVA)

radiation is divided into two domains. The first one, called ‘‘short

UVA’’, comprises the most energetic and thus the most harmful

type of UVA radiation, whose wavelengths are between 320 and

340 nm. These wavelengths are implicated in skin cancers [5]. The

second domain, called ‘‘long UVA’’, comprises the less energetic

radiation, whose wavelengths are between 340 and 400 nm. This

domain of UVA radiation is responsible for early skin aging. The

need for new materials able to filter the ‘‘short UVA’’ radiation hasincreased in the field of cosmetic products. With a band-gap of

3.2 eV, good transparency in the visible range, and no known

toxicity, nanostructured CeO2 appears to be a promising inorganic

material for use as a UV filter in sunscreen cosmetic products. In

several previous studies [6,7], the doping of CeO2 with different

elements such as Zn and Mg has been successfully used to shift the

material’s band-gap value because of their effects on electronic

transitions.

Another significant problem for the pure CeO2 is its photo-

catalytic activity. As a result, it could oxidise under light and

degrade the other compounds present in the cream. This

characteristic makes the pure material incompatible with use in

cosmetic products. In fact, the CeO2 fluorite type structure is not

stable, because the Ce4+ ionic radius is not large enough to reach

the ideal value of 0.732 for the ionic radius ratio, r (Mn+)/r (O2À) , ofa

metallic element (M) in an MO8 coordination oxide. Thus, Ce4+ has

the tendency to be easily transformed into Ce3+, which has a larger

ionic radius. This reaction is accompanied by release of oxygen to

equilibrate the charges, which leads to the above-mentioned

negative effect.

A number of papers [8–10] have reported that doping with

divalent elements can reduce the photocatalytic activity of CeO2,and that the most efficient of these is Ca. The replacement of Ce4+

by a cation with a lower valence and a larger ionic radius, such as

Ca2+, stabilises the fluorite structure [10]. Although several results

have been already published regarding the effects of Ca doping,

there are few studies that are devoted to the effects of doping over

a large concentration range.

Different chemical methods can be used for the synthesis of

pure or doped CeO2. Among them, the electrochemical deposition

method [11], hydrothermal synthesis [12–14], the pyrrolidone

solution route [15,16], thesol–gel method[17,18], the soft solution

method [8–10], and the co-precipitation technique [7,19] can all be

Materials Research Bulletin 45 (2010) 527–535

A R T I C L E I N F O

Article history:

Received 11 September 2009

Received in revised form 20 January 2010

Accepted 4 February 2010

Available online 12 February 2010

Keywords:

A. Nanostructures

B. Chemical synthesis

C. X-ray diffraction

C. Electron microscopy

D. Optical properties

A B S T R A C T

Calcium doped CeO2 nanoparticles with doping concentrations between 0 and 50 mol% were

synthesized by a co-precipitation method for ultraviolet filtration application. Below 20 mol% doping

concentration, the samples were single-phase. From 30 mol%, CaCO3 appears as a secondary phase. The

calculated CeO2 mean crystallite size was 9.3 nm for the pure and 5.7 nm for the 50 mol% Ca-doped

sample. Between 250 and 330 nm, the absorbance increased for the 10, 30, and 40 mol% Ca-doped

samples compared to the pure one. The band-gap wasfound to be 3.20 eV for the undoped, and between

3.36 and3.51 eV forthe doped samples.The blue shiftsare attributedto thequantumconfinement effect.

X-ray photoelectron spectroscopy showed that the Ce3+ atomic concentration in the pure sample was

higher than that of the 20 mol% Ca-doped sample.

ß 2010 Elsevier Ltd. All rights reserved.

* Corresponding author.

E-mail address: [email protected] (L. Truffault).

Contents lists available at ScienceDirect

Materials Research Bulletin

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m a t r e s b u

0025-5408/$ – see front matterß 2010 Elsevier Ltd. All rights reserved.

doi:10.1016/j.materresbull.2010.02.008

mailto:[email protected]

http://www.sciencedirect.com/science/journal/00255408

http://dx.doi.org/10.1016/j.materresbull.2010.02.008

http://dx.doi.org/10.1016/j.materresbull.2010.02.008

http://www.sciencedirect.com/science/journal/00255408

mailto:[email protected]



listed. The co-precipitation method has several advantages: it is

simple, cost-efficient, and gives reproducible results.

In this study, we have used the co-precipitation method to

synthesise calcium-doped CeO2 powders with doping concentra-

tions in the range of 0–50 mol%. We have studied systematically

the effects of doping on the structural and optical properties of

CeO2.

2. Experimental procedures

2.1. Synthesis of pure and Ca-doped CeO 2

Pure and calcium-doped CeO2 powders were synthesized by the

co-precipitation method. For the synthesis of the pure material, a

1.15 mol L À1 cerium nitrate solution (Ce(NO3)3Á6H2O, Alfa Aesar,

99.5%) was mixed with 5 mol L À1 sodium hydroxide (NaOH, Alfa

Aesar, 98%) at ambient temperature. The resulting precipitate was

recovered by centrifugation and washed three times with

deionised water. A 27% (w/w) hydrogen peroxide solution was

then added at a temperature of 50 8C. The oxidised precipitate was

centrifuged and washed with deionised water before filtration

with a folded filter and calcination at 500 8C for 6 h in a porcelain

crucible (VWR) under air. The calcium doped CeO2 powders weresynthesized by adding a calcium chloride solution (CaCl2, Alfa

Aesar, 97%) to the initial solution with a varying concentration,

depending on the expected calcium doping molar concentration.

Beige powders were obtained at the end of the experimental

procedure.

2.2. Analyses used

2.2.1. TGA–DTA

Before calcination, the pure sample was characterized by

thermogravimetric analysis (TGA) and differential thermal analy-

sis (DTA) with a TG–DTA 92-18 Setaram instrument. The sample

was heated from 20 to 1000 8C at a rate of 10 8C/min under argon.

2.2.2. FTIR

Fourier transform infrared (FTIR) spectra of the pure sample

before and after calcination (mid-infrared source) were collected

using a Vertex 70 Fourier transform infrared spectrometer from

Bruker in attenuated total reflection (ATR) mode in the range of

400–4000 cmÀ1 with a resolution of 4 cmÀ1.

2.2.3. XRD

The crystalline structure of the pure and doped samples was

identified by X-ray diffraction (XRD) using the Cu Ka wavelength

(l = 1.5418740 A) of an X’Pert Pro X-ray diffractometer from

PANalitycal in the Bragg-Brentano configuration. The samples

were analysed in the range of 20–1008 with a step of 0.0048 and a

time per step of 90 s. X’Pert HighScore + software was used toanalyse the data. The Scherrer formula presented below was used

for the most intense peak, which was fitted by a pseudo-Voigt

function, to determine the mean crystallite size:

Tc ¼kl

B cosu ; with B ¼ Bobs À Bstd; (1)

where Tc is the mean crystallite size, k is a constant shape factor

(set at 0.9 in our experiments;a value suitable fora cubiccrystal),l

is the wavelength of the incident X-rays, Bobs is the observed full-

widthat half-maximum (FWHM) of the considered peak, Bstd is the

instrumental contribution to the FWHM, and u is the value of the

diffracted angle. Rietveld type refinement was used to determine

the lattice constants.

2.2.4. TEM

The morphology and the particle sizes were characterizedusing

a CM 20 transmission electron microscope (TEM) from Philips. The

samples were dispersed in methanol by ultrasonication. A drop of

the suspension was then laid on a carbon-coated grid and dried

under a lamp to let the methanol evaporate. The accelerating

voltage used in TEM was 200 kV. A statistical grain size analysis

was realised from the TEM images by measuring the diameter, or

the biggest dimension for non-spherical particles, of at least 200

particles per sample. Selected area electron diffraction (SAED) was

performed to determine the crystallinity of the structure. The

interplanar spacings were evaluated from the SAED patterns using

the following formula:

lL ¼ Rd; (2)

where lL is a constant of the microscope, R is the ringradius, and d

is the interplanar spacing. The constant of the microscope was

calculated by measuring the radius of a gold standard pattern

whose interplanar spacings are well known.

2.2.5. UV–vis absorption spectroscopy

The absorption spectra of the samples were recorded with a V

530 ultraviolet–visible spectrophotometer from Jasco in the rangeof 200–1000 nm using quartz cells 1 cm in length. The samples

were dispersed in ethanol at a concentration of 7 Â 10À4 mol L À1

(3 mg in 25 mL) by ultrasonication for 30 min. Some pure ethanol

was taken as a reference. The absorption coefficient, a, was

calculated from the absorption spectra using the following

equation:

a ¼2303Â 103 Á A Á r

l Á c ; (3)

where A is the absorbance, r is the real density of CeO2 (set at

7.28 g cmÀ3 for our calculations), l is the length of the curve, and c

is the concentration of the CeO2 suspension. The band-gap values

were calculated by plotting (ahn)2 as a function of hn, where hn is

the photon energy. The intersection of the extrapolated linearportions with the abscissa axis gives the band-gap value.

2.2.6. XPS

X-ray photoelectron spectra (XPS) of the pure and 20 mol%

calcium-doped samples were collected using a SPECS system

installed in a high-vacuum chamber with the base pressure below

10À8 mbar; the X-ray excitation was provided by Al Ka radiation

with the photon energy hn = 1486.6 eV at a high voltage of 12 kV

and a power of 120 W. The spectra were collected at the pass

energy of 20 eV in the fixed analyser transmission mode.

Thepowder underanalysis was dusted onto an adhesive carbon

tape. An identical carbontape with a reference Cu sample on it was

used to determine the charge shift. The peak positions for Ce3+ and

Ce4+

obtained in this way are in good agreement with thosereported in the literature [20].

It is known that the XPS spectrumof pure CeO2 has six peaks for

the 3d line due to strong hybridization of the oxygen 2p valence

band with the Ce 4f orbital, which makes quantitative analysis of

the reduction of Ce atoms from the 4+ to the 3+ state extremely

complicated [21,22]. We have chosen the following method to

determine relative concentrations of the Ce3+ and Ce4+ cations

from the Ce 3d5/2 line. First, the background was subtracted using

the Shirley approximation, and then the 3d5/2 peak structure was

fitted by five components (i.e., three peaks originating from the 4+

state, and two peaks originating from the 3+ state) using the

commercial CasaXPS2.3.15 software package. The relative atomic

concentrations of the cations under question were determined as

the ratio of the respective peak areas (i.e., the total area of thethree

L. Truffault et al./ Materials Research Bulletin 45 (2010) 527–535528



calcium-doped sample. The dependence of the CeO2 mean

crystallite size as measured by XRD on the calcium doping

concentration is presented in Fig. 5. The graph shows that the CeO2

mean crystallite size decreases with increasing doping concentra-

tion. Nevertheless, the decrease seems to reach a threshold from a

doping concentration of 30 mol%. Basically, the addition of a

dopant into a crystalline structure affects the crystallite growth

kinetics. Before inserting itself into the CeO2 structure, the calcium

is first located between the CeO2 grain boundaries and thus

disturbs the normal growth of the CeO2 crystallites. We can

distinguish two domains in Fig. 5, corresponding to two modes of

the CeO2 crystal size change. The first domain corresponds to a

calcium doping concentration between 0 and 30 mol%. In this

domain, the CeO2 mean crystallite size decreases sharply with the

calcium doping concentration. Above 30 mol%,the beginning of the

second domain, the decreasing of the CeO2 crystallite size becomes

less pronounced because of the secondary phase formation.

In Fig. 6, we present TEM images of the pure CeO2 and the

50 mol% calcium-doped CeO2 nanoparticles. Despite the ultra-

sonication, both images show that the crystallites tend toagglomerate and form aggregates. This tendency has already been

reported by Phoka et al. [16]. Basically, nanoparticles have a

natural tendency to agglomerate for two main reasons. First, the

agglomeration is a more stable configuration from an energetic

point of view. Then, nanoparticles tend to agglomerate to allow for

crystallite growth. The results presented in Table 1 indicate that

the mean crystallite sizes measured from the TEM images differ at

most by 1 nm from those obtained by XRD. This means that the

TEM results are consistent with those obtained by XRD. The

crystallite size histograms of pure CeO2, 20 mol% calcium-doped,

and 50 mol% calcium-doped nanoparticles are shown in Fig. 7. For

the three samples, the crystallite size is between 2 and 20 nm. The

calcium doping causes a reduction in the number of crystallites

belonging to the size range from 10 to 20 nm. It is noteworthy thatthe mean crystallite size for the 50 mol% Ca-doped sample

obtained from the TEM images is bigger than that for the

20 mol% Ca-doped sample. This result seems at first to be

inconsistent with the XRD results. However, the 50 mol% Ca-

doped sample contains the CaCO3 phase, whose crystallite size is

on average bigger than that of CeO2. Since it is hardly possible to

distinguish the CeO2 crystallites from the CaCO3 crystallites on a

TEM image, we suggest that our measurements involve CaCO3

crystallites, which thus explains the bigger mean crystallite size

Fig. 4. Dependence of the CeO2 lattice parameter on the calcium doping

concentration.

Fig. 5. Dependence of the CeO2 mean crystallite size as measured by XRD on the

calcium doping concentration.

Fig. 6. TEM images of pure CeO2 (a) and 50 mol% Ca-doped CeO2 (b) nanoparticles.

Table 1

Comparison of mean crystallite size measured by XRD to mean particle size

measured by TEM for pure CeO2, 20mol% Ca-doped CeO2, and 50mol% Ca-doped

CeO2.

Sample Mean crystallite

size measured

by XRD (nm)

Mean particle

size measured

by TEM (nm)

Standard deviation

for TEM results

CeO2–0 mol% Ca 9.3 8.3 2.3

CeO2–20 mol% Ca 6.8 5.9 1.6

CeO2–50 mol% Ca 5.7 6.3 1.7




obtained for the 50 mol% Ca-doped sample. The SAED pattern of

pure CeO2 nanoparticles is presented in Fig. 8. The interplanarspacings measured from this pattern correspond to the CeO2

structure, and confirm the purity of the CeO2 pure sample.

Next, we consider the absorbance curves of the pure and

calcium-doped samples (see Fig. 9). The absorbance curve of theCeO2 pure sample is composed of one large band, whose maximum

is located at around 315 nm. For CeO2, the fundamental absorption

is due to a charge transfer between the full 2p (O) orbital and the

empty 4f (Ce) orbital [3,6,15], which corresponds to an experi-

mental band-gap value of 3.19 eV for the bulk [6]. For nanomater-

ials with particle sizes down to a few nanometers, the band-gap

value is modified because of the quantum confinement effect. For

spherical nanoparticles with an infinitely high potential energy

Fig. 7. Crystallite size histograms of (a) pure CeO2, (b) 20 mol% Ca-doped, and (c) 50 mol% Ca-doped nanoparticles.

Fig. 8. SAED pattern of pure CeO2

nanoparticles.

Fig. 9. Absorbance curves of 20 mol% (a), 50 mol% (b), 0 mol% (c), 30 mol% (d),

40 mol% (e) and 10 mol% (f) calcium doped CeO2

nanoparticles.

L. Truffault et al./ Materials Research Bulletin 45 (2010) 527–535 531



outside the sphere, the band-gap value is dependent on theparticle

radius R, and can be determined from the following formula [27]:

E ¼ E g þh2

8R2

1

meþ

1

mh

À

1:8e2

4pee0R(4)

where E g is thebulk band-gap, R is theradiusof thenanoparticles, me

andmharethe effective massesof theelectronand hole,respectively,

ande

is the relative dielectric constant of CeO2. The above equationindicates that the band-gap value increases with decreasingparticle

radius R. This phenomenon can be observed on the absorbance

curves of the calcium-dopedsamples. These curves are composed of

one large band, but the maximum absorption is located at a lower

wavelength (around 300 nm) than for the pure sample. This means

that the doping causes a blue shift of the maximum absorption. This

blue shift canbe quantifiedby calculatingboththe theoretical band-

gap values fromthe above equation and the experimental band-gap

values from the absorbance curves. Fig. 10(a)–(e) shows the band-

gap value extraction for the 0, 10, 20, 30, 40, and 50 mol% calcium-

doped samples, respectively. We have calculated the theoretical

band-gap values for each sample by taking E g = 3.15 eV,

me = mh = 0.4 m, where m is the mass of a free electron, and

e = 24.5 [28], andby replacingR by themean crystallitesize obtained

from the XRD results. Fig. 11 presents the calculated band-gap as a

function of the calcium doping concentration, and Fig. 12 presents

the experimental band-gap as a function of the calcium doping

concentration.

The calculated band-gap value of pure CeO2 with a mean

crystallite size of 9.3 nm is 3.160 eV. From Fig. 13 one can see that

this value increases with decreasing mean crystallite size, as

expected according to Eq. (4). The experimental band-gap values

are always higher than the theoretical ones, indicating that the

mean crystallite size may have been over-valued for all the

samples. The observed difference between the theoretical and the

Fig. 10. Plot of (ahn)2 as a function of energy for the 0 mol% (a), 10 mol% (b), 20 mol% (c), 30 mol% (d), 40 mol% (e), and 50 mol% (f) Ca-doped CeO2

samples.




experimental values can thus be explained by the fact that the

crystallite size chosen for the calculations is an average. As shown

by the crystallite size histograms obtained from the TEM images,

the crystallite size is in reality between 2 and 20 nm.

The experimental band-gap value of the pure CeO2 is 3.20 eV(369 nm), andis higher than the bulk experimentalvalue. This blue

shift of the band-gap value for CeO2 nanoparticles (which has

already been reported [3,15,16]) results in a change in the

electronic band structure due to the quantum confinement effect

[16]. For the calcium-doped CeO2 nanoparticles, all the values are

higher than 3.20 eV. This means that the calcium doping has

increased the blue shift that already exists for pure CeO2

nanoparticles compared to CeO2 bulk.

As one can infer from Fig. 9, there is no indication of any

dependence of the absorbance intensity on the calcium doping

concentration. Indeed, between 250 and 330 nm, the 10, 30, and

40 mol% Ca-doped samples absorb more UV radiation than the

pure sample. The most harmful UVA radiation, i.e., the short-

wavelength UVA radiation, is thus better filtered below 330 nmwith these doping concentrations. Among the three samples cited

above, the 10 mol% one is the most efficient between 265 and

325 nm. In fact, several factors affect the absorption properties of

the doped sample in opposite directions. First, the doping with

calcium should make the ceria unit cell more stable by tending to

the value of 0.732 for ideal ionic radius ratio, r (Mn+)/r (O2À), of a

MO8 coordination oxide. We could thus expect that the absorption

properties of the calcium-doped samples are decreased. As a result,

the calcium-doped samples should be less sensitive to the UV

radiation. Thus, the more calcium the sample contains, the more

the absorbance should decrease. The crystallite size should affect

the absorption capacities of the samples as well.The XPS spectra of the pure and the 20 mol% calcium-doped

samples were measured before ion bombardment [cf. Fig. 14(a)

and (c)], and after ion bombardment [cf. Fig. 14(b) and (d)]. The

peaks in the energy interval between approximately 877 and

903 eV belong to the Ce 3d5/2 level. There are three peaks (situated

at 882–883, 889–890, and 898–899 eV) that may be attributed to

the cerium (IV) oxidation state, whereas the other two peaks

(situated at 881–882 and 885–886 eV) may be attributed to the

cerium (III) state [20]. The peaks from the different oxidationstates

overlap, making analysis of the structure extremely complicated.

As is mentioned above, we performed deconvolution of the peak

structure using the CasaXPS2.3.15 software package. In Fig. 14, the

experimental spectra are shown as ‘‘noisy’’ curves, whereas the

‘‘smooth’’ dashed and solid peaks, obtained by fitting theexperimental peak structure, characterize the Ce3+ and Ce4+ ions,

respectively. The white line that fits the experimental curve

corresponds to the sum of all the components.

Using the components that belong to a definite oxidation state,

one can quantify the relative concentrations of the Ce3+ and Ce4+

ions according to the relations:

%Ce3þ ¼ACe3þ

ACe3þ þ ACe4þ

Â 100; %Ce4þ ¼ACe4þ

ACe3þ þ ACe4þ

Â 100; (5)

where ACe3þ and ACe4þ denotethe total areaof the Ce3d5/2 peaks for

the (III) and (IV) oxidation states, respectively.

The calculation shows that the concentration of Ce3+ ions in the

pure sample (37%) is higher than that in the doped sample (21%)before ion bombardment. This means that the Ce4+ relative

concentration in the calcium-doped sample (79%) is higher than

that in the pure one (63%). The oxygen concentration is higher in

the calcium-doped sample than in the pure one, too. We can

conclude that the doped sample better approaches the CeO2 ideal

stoichiometrybecause it contains moreCe4+ ions and moreoxygen,

and that the calcium doping has successfully made the CeO2

structure more stable. Also, since thepuresample is not as stableas

the doped sample due to its higher Ce3+ relative atomic

concentration, we can suppose that this material will be more

easily excited by the UV radiation and react more strongly to this

excitation.

After the ion bombardment, the relative concentration of Ce3+

has increased in both the pure (up to 51%) and in the doped (up to

Fig. 11. Plot of the calculated band-gap as a function of the calcium doping

concentration.

Fig. 12. Plot of the experimental band-gap as a function of the calcium doping

concentration.

Fig. 13. Plot of the calculated band-gap as a function of mean crystallite size.




39%) samples. Nevertheless, the Ce3+ relative ionic concentration

remains higher after the bombardment in the pure sample than in

the doped one. Possibly, the ion bombardment caused the

observed reduction by changing Ce4+ ions into Ce3+ ions. In this

case, the energy provided by the Ar beam could have broken the

Ce-O bonds, leading to the formation of Ce3+ ions.

4. Conclusions

Pure and calcium doped CeO2 nanoparticles with a calcium

doping concentration between 0 and 50 mol% have been success-

fully synthesized by the co-precipitation method. The calcium

doping modifies the structural and optical properties of pure CeO2.Above a 30 mol% calcium doping concentration, the samples

contain a CaCO3 secondary phase and are not suitable for a use as a

cosmetic product. The calcium doping causes a decrease in the

mean crystallite size and increases the absorbance for the 10, 30,

and 40 mol% Ca-doped samples between 250 and 335 nm. The

10 mol% Ca-doped sample is the most efficient between 265 and

325 nm. A blue shift of the absorption is observed first for the pure

CeO2 nanoparticle sample compared to the bulk CeO2, and thenfor

the doped samples compared to the pure sample. This blue shift

allows for better screening of short UVA, the most harmful UVA

wavelengths which are involved in skin cancers. Since the Ce3+

relative atomic concentration has been found to be higher in the

pure sample than in the doped samples, we can also conclude that

the calcium doping successfully made the structure more stable.

Another advantage of the calcium doping is the cost. Indeed,

since cerium (III) nitrate hexahydrate is around five times more

expensive than calcium chloride, doping CeO2 with calcium allows

one to decrease the final cost of the nanoparticle product.

References

[1] J. Kaspar, P. Fornasiero, M. Graziani, Catal. Today 50 (1999) 285–298.[2] V.D. Kosynkin, A.A. Arzgatkina, E.N. Ivanov, M.G. Chtousta, A.I. Grabko, A.V.

Kardapolov, N.A. Sysina, J. Alloys Compd. 303–304 (2000) 421–425.[3] S. Tnunekawa, T. Fukuda, A. Kasuya, J. Appl. Phys. 87 (2000) 1318–1321.[4] S. Tnunekawa, J.-T. Wang, Y. Kawazoe, A. Kasuya, J. Appl. Phys. 94 (2003) 3654–

3656.[5] A. Stary, C. Robert, A. Sarasin, Mutat. Res., DNA Repair 383 (1997) 1–8.

[6] F. Chevire,F. Munoz, C.F.Baker, F. Tessier, O. Larcher, S. Boujday,C. Colbeau-Justin,R. Marchand, J. Solid State Chem. 179 (2006) 3184–3190.

[7] L. Yue, X.-M. Zhang, J. Alloys Compd. 475 (2008) 702–705.[8] S. Yabe, M. Yamashita, S. Momose, K. Tahira, S. Yoshida, R. Li, S. Yin, T. Sato, Int. J.

Inorg. Mater. 3 (2001) 1003–1008.[9] R. Li,S. Yabe, M.Yamashita, S.Momose, S.Yoshida,S. Yin, T.Sato,SolidStateIonics

151 (2002) 235–241.[10] S. Yabe, S. Tsugio, J. Solid State Chem. 171 (2002) 7–11.[11] T. Wang, D.-C. Sun, Mater. Res. Bull. 43 (2008) 1754–1760.[12] A.I.Y. Tock, F.Y.C. Boey, Z. Dong, X.L. Sun, J. Mater. Process. Technol. 190 (2007)

217–222.[13] X. Lu, X. Li, F. Chen, C. Ni, Z. Chen, J. Alloys Compd. 476 (2009) 958–962.[14] F. Zhou, X. Ni, Y. Zhang, H. Zheng, J. Colloid Interface Sci. 307 (2007) 135–138.[15] C. Ho, J.C. Yu, T. Kwong, A.C. Mak, S. Lai, Chem. Mater. 17 (2005) 4514–4522.[16] S. Phoka, P. Laokul, E. Swatsitang, V. Promarack, Mater. Chem. Phys. 115 (2009)

423–428.[17] I. Skofic, S. Sturm, M. Ceh, N. Bukovec, Thin Solid Films 422 (2002) 170–175.[18] Z.L. Liu, H.M. Yue, Y. Wang, K.L. Yao, Q. Liu, Solid State Commun. 124 (2002) 171–

176.

Fig. 14. XPS spectra of pure powder [panels (a), (b)], and 20 mol% calcium-doped powder [panels (c), (d)]. Spectra (a) and (c) are taken for the samples before ion

bombardment;spectra (b)and (d)are takenafterthe bombardment.The black dashedand solid linesrepresent fitted peaksfor theoxidation states(III) and(IV), respectively;

the white line represents the sum of all the components. Dotted lines are for the Ce 3d 3/2 components (not considered here).




[19] M.J. Godinho, R.F. Goncalvez, L.P.S. Santos, J.A. Varela, E. Longo, E.R. Leite, Mater.Lett. 61 (2007) 1904–1907.

[20] E.G. Heckert, A.S. Karakoti, S. Seal, W.T. Self, Biomaterials 29 (2009) 2705–2709.[21] H. Ohno, A. Iwase, D. Matsumura, Y. Nishihata, J. Mizuki, N. Ishikawa, Y. Baba, N.

Hirao, T. Sonoda, M. Kinoshita, Nucl. Instr. Meth. B 266 (2008) 3013–3017.[22] J.P. Holgado, R. Alvarez, G. Munuera, Appl. Surf. Sci. 161 (2000) 301–315.[23] D. Andreescu, E. Matijevic, D.V. Goia, Colloids Surf. A 291 (2006) 93–100.

[24] J. Liu, Z. Zhao, J. Wang, C. Xu, A. Duan, G. Jiang, Q. Yang, Appl. Catal. B 84 (2008)185–195.

[25] S. Wang, F. Gu, C. Li, H. Cao, J. Cryst. Growth 307 (2007) 386–394.[26] V. Thangadurai, P. Kopp, J. Power Sources 168 (2007) 178–183.[27] J. Schoonman, Solid State Ionics 157 (2003) 319–326.[28] F. Zhang, Q. Jin, S.-W. Chan, J. Appl. Phys. 95 (2004) 4319–4326.


Application of Nano Structured CA Doped CeO2 for Ultraviolet Filtration

Documents

Transcript of Application of Nano Structured CA Doped CeO2 for Ultraviolet Filtration