Application of nanostructured Ca doped CeO2 for ultraviolet filtration

doi:10.1016/j.materresbull.2010.02.008

Materials Research Bulletin

Volume 45, Issue 5, May 2010, Pages 527-535

https://doi.org/10.1016/j.materresbull.2010.02.008 Get rights and content

Abstract

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 was found to be 3.20 eV for the undoped, and between 3.36 and 3.51 eV for the doped samples. The blue shifts are attributed to the quantum confinement 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.

Introduction

Recently, CeO₂ has been the subject of many studies regarding its use as a catalyst [1], polishing agent [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 has increased 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 photocatalytic 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(O²⁻), of a 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], [9], [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], [13], [14], the pyrrolidone solution route [15], [16], the sol–gel method [17], [18], the soft solution method [8], [9], [10], and the co-precipitation technique [7], [19] can all be 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 concentrations in the range of 0–50 mol%. We have studied systematically the effects of doping on the structural and optical properties of CeO₂.

Section snippets

Synthesis of pure and Ca-doped CeO₂

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⁻¹ cerium nitrate solution (Ce(NO₃)₃·6H₂O, Alfa Aesar, 99.5%) was mixed with 5 mol L⁻¹ 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 °C. The oxidised precipitate was

Results and discussion

Fig. 1 shows the TGA/DTA curves of the pure sample before calcination. The total mass loss was 18.1%. According to the following thermal decomposition formula: $Ce O_{2} \cdot 2 H_{2} O \to Ce O_{2} + 2 H_{2} O (vapor)$ , the mass loss associated with the structural water loss was 17.3%. The additional loss of mass of 0.8% obtained from the TGA curve can be attributed to a loss of moisture. The presence of a large endothermic peak whose maximum is located at 118 °C confirms the dehydration reaction. From a temperature of 650 °C,

Conclusions

Pure and calcium doped CeO₂ nanoparticles with a calcium doping concentration between 0 and 50 mol% have been successfully 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,

References (28)

J. Kaspar et al.
Catal. Today
(1999)
V.D. Kosynkin et al.
J. Alloys Compd.
(2000)
A. Stary et al.
Mutat. Res., DNA Repair
(1997)
F. Chevire et al.
J. Solid State Chem.
(2006)
S. Yabe et al.
Int. J. Inorg. Mater.
(2001)
R. Li et al.
Solid State Ionics
(2002)
T. Wang et al.
Mater. Res. Bull.
(2008)
X. Lu et al.
J. Alloys Compd.
(2009)
F. Zhou et al.
J. Colloid Interface Sci.
(2007)
S. Phoka et al.
Mater. Chem. Phys.
(2009)

Z.L. Liu et al.

Solid State Commun.

(2002)

M.J. Godinho et al.

Mater. Lett.

(2007)

H. Ohno et al.

Nucl. Instr. Meth. B

(2008)

J.P. Holgado et al.

Appl. Surf. Sci.

(2000)

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Application of nanostructured Ca doped CeO2 for ultraviolet filtration

Abstract

Introduction

Section snippets

Synthesis of pure and Ca-doped CeO2

Results and discussion

Conclusions

Catal. Today

J. Alloys Compd.

Mutat. Res., DNA Repair

J. Solid State Chem.

Int. J. Inorg. Mater.

Solid State Ionics

Mater. Res. Bull.

J. Alloys Compd.

J. Colloid Interface Sci.

Mater. Chem. Phys.

Solid State Commun.

Mater. Lett.

Nucl. Instr. Meth. B

Appl. Surf. Sci.

Application of nanostructured Ca doped CeO₂ for ultraviolet filtration

Synthesis of pure and Ca-doped CeO₂