Journal of Physics and Chemistry of Solids 72 (2011) 869–874

Contents lists available at ScienceDirect

Journal of Physics and Chemistry of Solids

0022-36

doi:10.1

n Corr

Science

Tel./fax:nn Cor

E-m

journal homepage: www.elsevier.com/locate/jpcs

Preparation and characterization of SrSnO3 nanorods

Li Chaoa,b,n, Zhu Youqia, Fang Shaominga, Wang Huanxina, Gui Yanghaia, Bi Leia, Chen Rongfengb,nn

a Henan Province Key Laboratory of Surface & Interface Science, Zhengzhou University of Light Industry, Zhengzhou 450002, Chinab Henan Academy of Science, Zhengzhou 450002, China

a r t i c l e i n f o

Article history:

Received 31 October 2007

Received in revised form

14 December 2010

Accepted 3 April 2011Available online 29 April 2011

Keywords:

A. Oxides

A. Nanostructures

B. Chemical synthesis

D. Electrochemical properties

97/$ - see front matter & 2011 Elsevier Ltd. A

016/j.jpcs.2011.04.001

esponding author at: Henan Province Key Lab

, Zhengzhou University of Light Industry, Zhe

þ86 371 63556510.

responding author.

ail address: zzulilc@zzuli.edu.cn (C. Li), zzulil

a b s t r a c t

Perovskite strontium stannate (SrSnO3) nanorods were prepared by annealing the precursor SnSr(OH)6

nanorods at 600 1C for 3 h. The precursor nanorods were hydrothermally synthesized at 160 1C for 16 h

using Sr(NO3)2 and SnCl4 �5H2O as starting materials in the presence of surfactant cetyltrimethyl

ammonium bromide (CTAB). As-prepared samples were characterized by X-ray diffraction (XRD),

thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM),

transmission electron microscopy (TEM) and infrared ray spectroscopy (IR). The results show that

the as-synthesized powders are made of SrSnO3 one-dimensional nanorods of about 0.2–1 mm length

and 100–150 nm diameter. Possible formation mechanism of SrSnO3 with nanorod structure under

certain conditions was preliminarily analyzed, in which it was thought that CTAB played an important

role in the formation process of the nanorod structure. Electrochemical performance of the samples

versus Li metal was also evaluated for possible use in lithium-ion batteries.

& 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Perovskite strontium stannate (SrSnO3) is of technologicalinterest because of its potential applications in single flux quan-tum (SFQ) circuits, lithium-ion batteries, high-temperaturehumidity sensors, capacitor components with a small tempera-ture coefficient of capacitance, etc. [1–12]. Many works have beencarried out to synthesize SrSnO3 materials by means of a varietyof techniques such as solid-state reaction (SSR) [5–8], self-heat-sustained reaction (SHS), sol–gel, coprecipitation and hydrother-mal route [9–12]. Among all these methods, hydrothermal synth-esis, which leads to high purity and narrow size distribution ofthe products, is an efficient method to avoid the impurity andstructure detection going with the solid-state reaction [12].

Recently, 1D nanorod structural materials have attracted greatattention and intensive research. Materials that were made tohave a nanorod-like structure could display more excellent orsurprising performance than film or bulk materials [13–16].Cetyltrimethyl ammonium bromide (CTAB), an important qua-ternary ammonium salt surfactant, could serve as a versatile ‘soft’template or inductor of the directional grow for 1D nano-structural materials, such as ZnO [14], Ca5(PO4)3OH [15] and

ll rights reserved.

oratory of Surface & Interface

ngzhou 450002, China.

c@zzuli.edu.cn (R. Chen).

a-Mn2O3 [16] nanorods. However, little work has been reportedon preparation of SrSnO3 nanorods by CTAB-assisted hydrother-mal route to our knowledge.

In this work, a surfactant CTAB-assisted hydrothermal methodis successfully used to synthesize precursor SnSr(OH)6 nanorods,which converted into SrSnO3 nanorods with perovskite structureby low-temperature calcinations. Possible formation mechanismof SrSnO3 with nanorod structure under certain conditions waspreliminarily analyzed, in which it was thought that CTAB playedan important role in the formation process of the nanorodstructure. Electrochemical performance of the samples versus Limetal was also evaluated for possible use in lithium-ion batteries.

2. Experimental procedure

2.1. Preparation

All the analytical grade chemicals were used without furtherpurification. In a typical procedure, the quantificational chemicalsSr(NO3)2 (10 mmol), SnCl4 �5H2O (10 mmol), CTAB (1.5 mmol)and H2O (30 mL) were added to a glass vessel, stirred and formeda solution. When the pH of the formed solution was adjusted to13.0 with 1 mol/L�1 NaOH, a white suspension was obtained.Afterwards, the suspension was transferred into a Teflon-linedstainless autoclave with about 80% degree of fill. The autoclavewas sealed and maintained at 160 1C for 16 h, and then naturallycooled down to room temperature. The obtained precipitatewas filtered and washed for several times with distilled water.

C. Li et al. / Journal of Physics and Chemistry of Solids 72 (2011) 869–874870

After dried in air, the precursor SrSn(OH)6 powders were obtainedand then thermally treated at 600 1C for 3 h to get converted intothe final SrSnO3 powders. The precursor and final powders werecollected for characterization.

2.2. Characterization

The crystal structure of synthesized samples was characterizedby X-ray powder diffraction (XRD, Bruke D8 diffractometer, withCuKa radiation, l¼1.5418 A). The morphology and microstruc-ture were observed by scanning electron microscopy (SEM, JEM-5600, with an accelerating voltage of 20 kV) and transmissionelectron microscopy (TEM, FEI TECNAI G20, with an acceleratingvoltage of 200 kV). Thermogravimetric-differential thermal ana-lysis (TG-DTA) data were collected on a thermogravimetric-differential thermal analysis instrument (TG-DTA, ZRY-1) withthe heating and cooling rates of 10 1C/min. Infrared ray (IR)spectra were recorded on a Bruker TENSOR 27 infrared spectro-photometer in KBr medium.

Electrochemical performance of the samples versus Li metalwas also evaluated for possible use in lithium-ion batteries.SrSnO3 electrode fabrication is the same, as reported in literature[10]. The working electrode consists of 80 wt% as-preparedpowders as the active material, 10 wt% super-P carbon as theconducting agent, 10 wt% polyvinylidene fluoride (PVDF) as thebinder and a Cu foil as the substrate (current collector). The cellwas assembled in an Ar-filled glove box using a polypropylene(PP) micro-porous film as the separator, a solution of 1 M LiPF6 inethylene carbonate (EC)/dimethyl carbonate (DMC) (1:1, v/v) asthe electrolyte and a metallic lithium foil as the counter electrode.The electrochemical tests were performed on a CT2001A Landbattery testing systems (Hannuo Electronics Co. Ltd., China). Thecells were charged and discharged at a current of 80 mA g�1.

)

3. Results and discussion

3.1. TG-DTA curve of the precursor SrSn(OH)6

Fig. 1 shows the TG-DTA curves of the precursor SrSn(OH)6.There are strong endothermal effects at 331.2 1C in the DTA curve,which correspond to the dehydration and dehydroxylation pro-cess of the precursor powder. In accordance with the DTA curve, amain weight loss stage from 250 to 400 1C can be found in the TGcurve with a weight loss of 12%. SrSn(OH)6 is easy to dehydrate.

0

-12

-10

-8

-6

-4

-2

0

-14

-12

-10

-8

-6

-4

-2

0

2

TG

DTA

Temperature / °C

100 200 300 400 500 600 700 800 900

Fig. 1. TGA/DTA patterns of the precursor SrSn(OH)6.

When the molecular framework Sr–Sn–O–H was broken, H2Omolecules were released from the grain inside and outside, andthen Sr–Sn–O–H was converted into SrSnO3. From 400 to 800 1C,no weight loss can be observed in the TG curve and no peak wasobviously appeared in the DTA curve correspondingly, whichindicates that the precursor SrSn(OH)6 had been converted intoSrSnO3. Along with the rise in temperature and time of heattreatment, the crystallinity of samples increased step by step. Inorder to get the high purity and well crystalline materials, thetemperature of 600 1C was chosen as the calcination temperature.According to the above results, the forming process of SrSnO3 maybe described by equations as follows:

Sr2þþSn4þ

þ6OH�-SrSn(OH)6k (1)

SrSnðOHÞ6��!D

SrSnO3þ3H2Om ð2Þ

That is to say, the precursor SnSr(OH)6 should be synthesizedby the hydrothermal reaction (Eq. (1)) and perovskite strontiumstannate (SrSnO3) can be prepared by annealing the precursorSnSr(OH)6 (Eq. (2)).

3.2. Crystal structure and morphology of the samples

The XRD patterns confirmed that the precursor prepared bythe hydrothermal reaction was SnSr(OH)6 with hexagonal struc-ture. Fig. 2 shows XRD patterns of the precursor SnSr(OH)6 andfinal product SrSnO3. From XRD, it is confirmed that the X-raydiffraction pattern of precursor (in Fig. 2a) corresponds with thehexagonal SnSr(OH)6 phase (JCPDS-ICDD card no.090086 and thelattice parameters, a¼1.638 nm and c¼1.236 nm). The XRD resultof the precursor SnSr(OH)6 indicates that the precursor wassuccessfully prepared by surfactant CTAB-assisted hydrothermalmethod. Reflections of the final product (in Fig. 2b) can be readilyindexed to phase-pure cubic SrSnO3 (JCPDS-ICDD card no.22–1442 and the lattice parameters, a¼b¼c¼0.804 nm). It isclear that the hydrate SnSr(OH)6 could be completely transformedinto SrSnO3 in later calcination at 600 1C for 3 h.

Fig. 3 shows the IR spectrum of the final product SrSnO3. Forcomparison, the spectrum of precursor SnSr(OH)6 is also given.The peak at 3429 cm�1 is believed to be caused by O–H stretchingvibration and bending vibration of water molecules adsorbed bythe precursor SnSr(OH)6 [17–19], which has a sharp decrease in

20

a

Lin

(co

unts

)

2-Theta-Scale

b

(200

)

(220

)

(400

)

(422

)

(440

)

(620

)

(110

)

(301

(004

)

(712

)

(441

)(4

32)

(512

)(4

13)

(330

)

40 60 80

Fig. 2. X-ray diffraction patterns of samples: (a) precursor SnSr(OH)6 and (b) final

product SrSnO3.

C. Li et al. / Journal of Physics and Chemistry of Solids 72 (2011) 869–874 871

intensity after the precursor SnSr(OH)6 is completely transformedinto the final product SrSnO3. Because of the easy-water-sorptionproperties of alkaline stannates, there is still a little waterremained in the final product SrSnO3. Peaks at 2911 and2844 cm�1 in the spectrum can be attributed to C–H symmetricand asymmetric vibration of –CH2– in CTAB [17,19], and theydisappeared after the calcination in which the precursor comple-tely transformed into the final product. The band centered at1481 cm�1 is also assigned to water [18,20], with a sharpdecrease in intensity for the final product SrSnO3. The bandsobserved in the range of 850–1350 cm�1 are assigned to thebending mode of different types of surface hydroxyl groups, andthey also disappeared after the precursor transformed into thefinal product. Finally, the signals observed in the 400–850 cm�1

region can be associated to Sn–O molecular vibrations [17,21].Special attention should be addressed to the peaks appearing at576 and 666 cm�1 since these signals are due to vibrations of theO–Sn–O bridging and Sn–OH terminal bonds [17,18]. In accor-dance with the TG-DTA analysis, the transformation of SnSr(OH)6

to SrSnO3 ends before 600 1C. During the calcination process, thestructure is rearranged and the octahedron structure [SnO6]began to form. After calcined at 600 1C for 3 h, Sn–OH peakdisappeared completely and the intensity of the [SnO6] increased.The result of IR supports the indexing result of XRD patterns thatthe precursor SnSr(OH)6 was completely transformed into thefinal product SrSnO3 in later calcination.

Fig. 4 shows the typical TEM images of the final productSrSnO3. The TEM images reveal that the as-synthesized powders

4000

Tra

nsm

ittan

ce

Wavenumber /cm-1

a

b

3600 3200 2800 2400 2000 1600 1200 800 400

Fig. 3. Infrared absorption spectra of samples: (a) precursor SnSr(OH)6 and

(b) final product SrSnO3.

Fig. 4. TEM images of final product SrSnO3: (a) high magnification, (b)

are made of SrSnO3 nanorods. It is estimated that the nanorodsare about 0.2–1 mm in length and 100–150 nm in diameter.Aspect ratios (length/width) may be related to the solutionconcentration of CTAB and reaction time [16]. The averagediameter and morphology of the final SrSnO3 products are similarto their precursors.

3.3. Possible formation mechanism of nanorod structure

It is well accepted that the existence of an appropriate amountof capping reagents can alter the surface energies of variouscrystal surfaces to promote selective anisotropic growth ofnanocrystals [22]. In this work, CTAB is the key parameter toaffect the morphology of the resulting SrSnO3. Fig. 5 illustratedschematically the proposed formation mechanism of the rod-likematerial in the presence of CTAB. As we know, CTAB is a cationicsurfactant and its critical micelle concentration (CMC) is9.2�10�4 mol/L. Above the CMC, a transition from sphericalmicelles to rod-like or other polygonal structure occurred[22,23]. In the absence of CTAB, irregular shape particles wouldbe obtained (Fig. 5a). In this work, SnCl4 and NaOH reacteddirectly and changed into amphoteric Sn(OH)4, which could easilydissolve in the excessive solution of NaOH to form Sn(OH)6

2�

group. It is assumed that the CTAB head groups are preferentiallyadsorbed on surface planes in the form of CTAþ–Sn(OH)6

2�

coordination compound after nucleation process of SrSn(OH)6

because the surface contains many Sn(OH)62� groups. The surface

planes on which CTAB head groups adsorb became the growthpoints and the crystal grows along the orientation. MeanwhileCTAB could also inhibit the excess aggregation of nanomaterialsbecause the surfactant could absorb on the surface of thenanomaterials and lower the interface energy. When the hydro-thermal reaction temperature was up to 160 1C or higher, theformation of the micelles was destroyed based on the previousreport [24] and only single CTAB head group adsorbs on thenucleus, which make the only anisotropic growth unit (Fig. 5b). Inthis way, the crystal grows along the growth unit orientation, theSrSn(OH)6 nanorod was formed. When the hydrothermal reactiontemperature was 150 1C or lower, the SrSn(OH)6 nanorod was notobserved under the same other conditions. Fig. 6 shows SEMimages of the precursor SrSn(OH)6 at the hydrothermal tempera-ture 160 1C in the absence and presence of CTAB. It is clear thatirregular shape particles would be obtained in the absence ofCTAB (Fig. 6a) while a transition from spherical micelles to rod-like occurred in the presence of CTAB (Fig. 6b) at the samehydrothermal temperature. The SrSn(OH)6 nanorod was also notobserved in the presence of CTAB at the hydrothermal tempera-ture 140 1C (Fig. 6c). The growth of SrSn(OH)6 nanorods is

low magnification and (c) a nanorod end with branchlets (inset).

no CTAB assisted

Sr2++Sn4++OH-

hydrothermalprocess

CTAB assisted

micelle

up to 160°C

under 160°C

active sitethe broken micelles

new active

a

c

b

Fig. 5. Schematic illustration of the process: (a) in the absence of CTAB at the hydrothermal temperature 160 1C, (b) in the presence of CTAB at the hydrothermal

temperature up to 160 1C and (c) in the presence of CTAB at the hydrothermal temperature below 160 1C.

Fig. 6. SEM images of the precursor SrSn(OH)6: (a) in the absence of CTAB at the hydrothermal temperature 160 1C, (b) in the presence of CTAB at the hydrothermal

temperature 160 1C and (c) in the presence of CTAB at the hydrothermal temperature 140 1C.

Fig. 7. (a) TEM image of the precursor SnSr(OH)6 in the presence of CTAB at the hydrothermal temperature 160 1C, (b) HR-TEM image taken at the precursor SnSr(OH)6

nanorod tip highlighted with a white box in (a), and (c) the inset in (b) shows corresponding fast Fourier transform pattern (FFT).

C. Li et al. / Journal of Physics and Chemistry of Solids 72 (2011) 869–874872

analogous to orientation growth of a-Mn2O3 nanorods by CTAB-assisted hydrothermal method in literature [16]. Because of thisgrowth restriction of CTAB in the solution, it could be applied inthe preparation of other ID structural materials. Fig. 7 shows theTEM images of the precursor SnSr(OH)6 nanorod in the presenceof CTAB at the hydrothermal temperature of 160 1C. The highresolution TEM (HR-TEM) image (Fig. 7b) observed at the tip ofone nanorod and the corresponding fast Fourier transform pattern(FFT) (Fig. 7c inset) confirm the single-crystal nature of thenanorod. The lattice spacing of 0.387 nm corresponds to thed-spacing of the SnSr(OH)6 (2 2 1) crystal planes. The resultindicates that the nanorod prefers to grow along their (1 1 1)direction. SrSn(OH)6 is easy to dehydrate. In the late process ofheat treatment, molecular framework Sr–Sn–O–H was broken,H2O molecules were released from the grain inside and outside,and then Sr–Sn–O–H was converted into SrSnO3. Finally, surfac-tants are eliminated and the precursor nanorods are converted toSrSnO3 nanorods by calcination.

In addition, we observe an interesting phenomenon that thereare some branchlets that grow vertically on the end of fewnanorods (as shown in Fig. 4c). This may be possibly attributedto the out-of-order growth of the crystals in local growth

surroundings. The abruptly increased concentration of Sn(OH)62�

could combine with CTAþ again and the new growth processbecame disordered [25].

3.4. Electrochemical properties

Fig. 8 shows the discharge–charge curves of SrSnO3 electrodesmeasured between 0 and 2.0 V (vs. Liþ/Li) at the rate of 80 mA/g.The first discharge–charge curve is different from the subsequentcurves, which is similar to other tin-based anode materials[26,27]. The first charge capacity for the SrSnO3 nanorods is1400 mA hg�1 and the discharge capacity is 316 mA hg�1. TheCoulombic efficiencies are over 90% except for the first cycle.Nanostructures are also highly beneficial for metal oxide elec-trode materials, e.g. for the tin oxide electrodes [28]. Considerableimprovements of tin oxide electrodes can be obtained by passingthem to nanostructures. For SrSnO3, the theoretical capacity offirst charge is 885 mA hg�1 [10]. The first charge capacity for theSrSnO3 nanorods in this work is clearly higher than the theoreticalcharge capacity of SrSnO3, which may be related to the nanorodstructure.

0.0

0.5

1.0

1.5

2.0

0

Valta

ge /

V

2345678910

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

1

200 400 600 800 1000 1200 1400

Specific capacity / mAhg-150 100 150 200 250 300 350

Fig. 8. Charge–discharge curves of different cycle numbers (in voltage window 0–

2 V vs. Li): (a) first cycle and (b) 2–10 cycle.

10

50

100

150

200

250

300

350

Spe

cific

cap

acity

(mA

h/g)

Cycle numbers2 3 4 5 6 7 8 9 10 11

Fig. 9. Specific capacities of different cycle numbers for the samples annealed at

different temperatures.

C. Li et al. / Journal of Physics and Chemistry of Solids 72 (2011) 869–874 873

It is known that tin oxides can electrochemically react withlithium with a first process involving the irreversible formation oflithium oxide and tin, and a followed one relating to reversiblealloying–dealloying of lithium and tin [29]. It is assumed that the‘‘in situ’’ formed lithium oxide can act as a ‘‘buffer’’ for accom-modating the volume changes, which accompany the secondalloying process. The reaction mechanism of SrSnO3 for thedischarge/charge process can be assumed to be similar to thatof tin oxide [10,27]:

SrSnO3þ4Liþþ4e-SrOþ2Li2OþSn (3)

xLiþþSnþxe-LixSn(xr4.4) (4)

Amorphous SrO compounds are thus formed (Eq. (3)), whichcannot be reduced to the Sr metal due to the high Sr–O bondstrength (425.5 kJ/mol), and these are electrochemically inactivewith Li. The pristine nanoparticles of Sn thus formed underwentalloy formation with Li (Eq. (4)). Although Sr could play a role of

dissepiment, it still made the material suffer from a great deal ofcapacity attenuation, and so these would be a challenge forfurther application.

Fig. 9 shows specific capacities of different cycle numbers forthe SrSnO3 products obtained by the heat treatment of precursorsat different temperatures. It is obvious that the discharge andcharge capacities of the SrSnO3 samples decrease with theincrease in cycling number. However, the cycle performance ofthe sample obtained by calcining at 600 1C is better than that ofthe sample obtained by calcining at 800 1C. This result wasthought to be related to the differences in their crystallinity andmicrostructure. It was confirmed that the crystallinity of thesample obtained by calcining at 600 1C was lower than that ofthe sample obtained by calcining at 800 1C. The lower crystallinitymay be a favor for that Sr to play a role of dissepiment.

4. Conclusion

Perovskite strontium stannate (SrSnO3) nanorods were suc-cessfully prepared by a two-step method. The precursorSnSr(OH)6 powders were hydrothermally synthesized at 160 1Cfor 16 h in the presence of surfactant cetyltrimethyl ammoniumbromide (CTAB) and then converted into SrSnO3 nanorods withperovskite structures by low-temperature calcinations. TG-DTA,XRD, IR, SEM and TEM were used to determine the structure andcomposition of the precursors and converted SrSnO3 products.The precursor is proved to be made of pure-phase hexagonalSnSr(OH)6 nanorods, which converted to perovskite-type cubicSrSnO3 nanorods by heat treatment in air at 600 1C for 3 h. Thefinal SrSnO3 nanorods are about 0.2–1 mm in length and100–150 nm in diameter. The surfactant CTAB played an impor-tant role in the formation of SrSnO3 nanorods and it might be ageneral capping reagent for the growth of one-dimensionalstructures of other compounds. Electrochemical performance ofthe SrSnO3 nanorod products versus Li metal was also evaluatedfor possible use in lithium-ion batteries.

Acknowledgments

The financial support from the National Natural Science Founda-tion of China (No. 20871107) and He’nan Outstanding Youth ScienceFund (No. 0612002700) is gratefully acknowledged.

References

[1] V. Thangadurai, Robert A. Huggin, W. Weppner, Use of simple ac technique todetermine the ionic and electronic conductivities in pure and Fe-substitutedSrSnO3 perovskites, J. Power Sour. 108 (2002) 64.

[2] Elizabeth H. Mountstevens, Simon A.T. Redfern, J. Paul Attfield, Order–disorder octahedral tilting transitions in SrSnO3 perovskite, Phys. Rev. B 71(2005) 220102(R).

[3] Shumei Wang, Mengkai Lu, Guangju Zhou, et al., Systematic investigationsinto SrSnO3 nanocrystals (I) synthesised by using combustion and copreci-pitation methods, J. Alloys Compd. 432 (2007) 265.

[4] Tatsumi Ishihara, Hiroki Fujita, Yusaku Takita, Effects of Pt addition forSrSnO3–WO3 cpacitive type sensor on NO detection at high temperature,Sensors Actuat. B 52 (1998) 100.

[5] Abdul-Majeed Azad, Lucia Liew Woan Shyan, Pang Toh Yen, Synthesis,processing and microstructural characterization of CaSnO3 and SrSnO3

ceramics, J. Alloys Compd. 282 (1999) 109.[6] V. Thangadurai, P. Schmid Beurmann, W. Weppner, Mixed oxide ion and

electronic conductivity in perovskite-type SrSnO3 by Fe substitution, Mater.Sci. Eng. B100 (2003) 18.

[7] B. Hadjarab, A. Bouguelia, M. Trari, Synthesis, physical and photo electro-chemical characterization of La-doped SrSnO3, J. Phys. Chem. Solids 68 (2007)1491.

[8] W.F. Zhang, Junwang Tang, Jinhua Ye, Photoluminescence and photocatalyticproperties of SrSnO3 perovskite, Chem. Phys. Lett. 418 (2006) 174.

C. Li et al. / Journal of Physics and Chemistry of Solids 72 (2011) 869–874874

[9] Abdul-Majeed Azad, Lucia Liew Woan Shyan, Toh Yen Pang, Chen Hon Nee,Microstructural evolution in MSnO3 ceramics derived via self-heat-sustained(SHS) reaction technique, Ceram. Int. 26 (2000) 685.

[10] N. Sharma, K.M. Shaju, G.V. Subba Rao, B.V.R. Chowdari, Anodic behaviourand X-ray photoelectron spectroscopy of ternary tinoxides, J. Power Sour. 139(2005) 250.

[11] S. Wang, et al., Systematic investigations into SrSnO3 nanocrystals (II)photoluminescent properties of the as-synthesized nanocrystals, J. AlloysCompd (2006). doi:10.1016/j.jallcom.2006.11.099.

[12] Zhouguang Lu, Limiao Chen, Yougen Tang, Yadong Li, Preparation andluminescence propertiesof Eu3þ-doped MSnO3 (M¼Ca, Sr and Ba) perovskitematerials, J. Alloys Compd. 387 (2005) L1.

[13] Park Won Il, Kim Jin Suk, Yi Gyu-Chul, Lee Hu-Jong, ZnO nanorod logiccircuits, Adv. Mater. 17 (11) (2005) 1393.

[14] Y.-L. Wei, P.-C. Chang, Characteristics of nano zinc oxide synthesized underultrasonic condition, J. Phys. Chem. Solids (2007). doi:10.1016/j.jpcs.2007.07.094.

[15] Yuxiu Sun, Guangsheng Guo, Dongliang Tao, Zhihua Wang, Reverse micro-emulsion-directed synthesis of hydroxyapatite nanoparticles under hydro-thermal conditions, J. Phys. Chem. Solids 68 (2007) 373.

[16] Youcun Chen, Yuanguang Zhang, Qi-Zhi Yao, et al., Formation of a-Mn2O3

nanorods via a hydrothermal-assisted cleavage-decomposition mechanism, J.Solid State Chem. 180 (2007) 1218.

[17] C. Velasquez, F. Rojas, M. LOjeda, AOrtiz, A. Campero, Structure and texture ofself-assembled nanoporous SnO2, Nanotechnology 16 (2005) 1278.

[18] D.N. Srivastava, S. Chappel, O. Palchik, A. Zaban, A. Gedanken, Sonochemicalsynthesis of mesoporous tin oxide, Langmuir 18 (2002) 4160.

[19] Yude Wang, Xinghui Wu, Yanfeng Li, Zhenlai Zhou, Mesostructured SnO2 assensing material for gas sensors, Solid-State Electron. 48 (2004) 627.

[20] Celso Velasquez, Marıa Luisa Ojeda, Antonio Campero, Juan Marcos Esparza1,Fernando Rojas, Surfactantless synthesis and textural properties of self-assembled mesoporous SnO2, Nanotechnology 17 (2006) 3347.

[21] Xavier Mathew, J.P. Enriquez, C. Mejıa-Garcıa, G. Contreras-Puente,M.A. Cortes-Jacome, J.A. Toledo Antonio, J. Hays, A. Punnoose, Structuralmodifications of SnO2 due to the incorporation of Fe into the lattice, J. Appl.Phys. 100 (2006) 073907.

[22] Jimin Du, Zhimin Liu, Ying Huang, et al., Control of ZnO morphologies viasurfactants assisted route ithe subcritical water, J. Cryst. Growth 280 (2005)126.

[23] L. Yingkai, H. Dedong, W. Guanghou, Synthesis and characterization of SnSnanowires in cetyltrimethyl ammonium bromide (CTAB) aqueous solution,Chem. Phys. Lett. 397 (2003) 67.

[24] Jianbo Wu, Hui Zhang, Xiangyang Ma, Jun Li, et al., Synthesis and character-ization of single crystalline MnOOH and MnO2 nanorods by means of thehydrothermal process assisted with CTAB, Mater. Lett. 60 (2006) 3895.

[25] X.M. Sun, X. Chen, Z.X. Deng, et al., A CTAB-assisted hydrothermal orientationgrowth of ZnO nanorods, Mater. Chem. Phys. 78 (2002) 99.

[26] Hyung-Wook Ha, Keon Kima, Mervyn de Borniol, et al., Fluorine-dopednanocrystalline SnO2 powders prepared via a single molecular precursormethod as anode materials for Li-ion batteries, J. Solid State Chem. 179(2006) 689.

[27] J. Besenhard, J. Yang, Winter M. Will, Will advanced lithium alloy anodeshave a chance in lithiumion batteries, J. Power Sour. 68 (1) (1997) 87.

[28] Stefania Panero, Bruno Scrosati, Mario Wachtler, Fausto Croce, Nanotechnol-ogy for the progress of lithium batteries, J. Power Sour. 129 (2004) 90.

[29] Y. Idota, T. Kubota, A. Matsufuji, Y. Maekawa, T. Miyasaka, Tin-basedamorphous oxide: a high-capacity lithium-ion-storage material, Science276 (1997) 1395.