novel precursor-assisted synthesis and characterization of zinc oxide nanoparticles/nanofibers

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Materials Letters ] (]]]]) ]]]–]]]

Contents lists available at SciVerse ScienceDirect

Materials Letters

0167-57

http://d

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Univers

Tel.: þ9

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Pleasnano

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

Novel precursor-assisted synthesis and characterization of zinc oxidenanoparticles/nanofibers

Faezeh Soofivand a, Masoud Salavati-Niasari a,b,n, Fatemeh Mohandes b

a Institute of Nano Science and Nano Technology, University of Kashan, Kashan, P.O. Box 87317-51167, Islamic Republic of Iranb Department of Inorganic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, P.O. Box 87317-51167, Islamic Republic of Iran

a r t i c l e i n f o

Article history:

Received 29 December 2012

Accepted 31 January 2013

Keywords:

Nanoparticles

Sensors

Semiconductors

7X/$ - see front matter & 2013 Published by

x.doi.org/10.1016/j.matlet.2013.01.129

esponding author at: Institute of Nano Sci

ity of Kashan, Kashan, P.O. Box 87317-5116

8 361 5912383; fax: þ98 361 5552935.

ail address: [email protected] (M. Salava

e cite this article as: Soofivand F, efibers. Mater Lett (2013), http://dx.d

a b s t r a c t

In this investigation, different morphologies of ZnO nanostructures including nanoparticles have been

produced by solid-state thermal decomposition of bis(acetylacetonato)zinc(II) nanostructures obtained

by the sublimation of bis(acetylacetonato)zinc(II) powder. The sublimation process of the Zn(acac)2

powder was carried out in the range of 110–140 1C. The as-synthesized products were analyzed

by SEM, TEM, XRD, and EDS. The SEM images showed that the sublimation process in the range of

110–120 1C and 130–140 1C led to the production of Zn(acac)2 nanofibers and nanorods, respectively.

On the other hand, nanofibers and nanoparticles of ZnO were obtained by solid-state thermal

decomposition of the as-synthesized Zn(acac)2 nanostructures.

& 2013 Published by Elsevier B.V.

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1. Introduction

ZnO nanostructures have attracted much attention due to theirpotential applications in solar cells as semiconductor [1], UVlasers [2], field emitters [3], sensors [4], catalysts [5], hydrogen-storage devices [6], and field-effect transistors [7]. Up to now,different morphologies of ZnO nanostructures including nano-wires, nanotubes, and hollow spheres synthesized by sol–geltemplate process [8], hydrothermal route [9], and thermal eva-poration method [10] have been developed. Although zinc acetatehydrate, zinc chloride, metallic zinc powder, and zinc nitratehydrate were applied as common zinc sources, various coordina-tion compounds were applied for the synthesis of ZnO nanoa-tructures [11,12].

In this work, one-dimensional (1-D) nanostructures of zincacetylacetonate were synthesized by the sublimation process ofZn(acac)2 powder, and then 1-D (nanofibers) and 0-D (nanopar-ticles) nanostructures of ZnO were prepared by solid-state ther-mal decomposition of the as-produced Zn(acac)2 nanostructures.Besides, the effect of reaction temperature on the morphology ofthe products was investigated. The present strategy involvesmany advantages as it is a controllable, free solvent, template-less, and economical method. The produced nanostructures werecharacterized by SEM, TEM, SAED, XRD, and EDS.

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Elsevier B.V.

ence and Nano Technology,

7, Islamic Republic of Iran.

ti-Niasari).

t al. Novel precursor-assisoi.org/10.1016/j.matlet.201

2. Experimental

Preparation of Zn(acac)2 nanostructures: in this work, zincacetylacetonate powder (100 mesh, 99.998%) purchased fromSigma-Aldrich Company was used as the starting reagent. Pre-paration of 1-D Zn(acac)2 nanostructures as precursor was per-formed in a vertical quartz pipe set under vacuum condition. Eachexperiment was carried out by loading 0.5 g of zinc acetylaceto-nate powder, which would be transferred in the external pipe ofthe set. Then, the system was vacuumed by pump and waterentered the inner pipe from one side, and exited from anotherside. Circulation of water was applied for the solidification ofproduct vapors. The abovementioned set was heated to desirabletemperature from 110 to 140 1C. After the heating process, nail-like thin depositions shown at the external part of inner pipewere collected. The as-obtained products were characterized bySEM, and XRD.

Preparation of ZnO nanostructures: in a typical experiment,0.1 g of the as-obtained Zn(acac)2 nanostructures was loaded intoa platinum boat. The platinum boat was placed in the center of ahigh-temperature tube furnace. The sample was heated in air at400 1C for 120 min. The as-synthesized white powders werecharacterized by SEM, TEM, XRD, and EDS.

Materials characterization: the powder X-ray diffraction (XRD)patterns were collected by a diffractometer of Philips Companywith X’PertPro monochromatized Cu Ka radiation (l¼1.54 A).Microscopic morphology of the products was visualized by SEM(LEO 1455VP). TEM images were obtained on a JEM-2100 with anaccelerating voltage of 60–200 kV equipped with a high resolu-tion CCD camera. The energy dispersive spectrometry (EDS)analyses were studied by an XL30, Philips microscope.

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http://dx.doi.org/10.1016/j.matlet.2013.01.129



mailto:[email protected]





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3. Results and discussion

Recently, there has been major interest in the development ofcoordination compounds for the preparation of nanomaterials[13–15]. Using of the novel compounds can be useful and open anew way for preparing nanomaterials to control shape and sizedistribution of nanocrystals. In this work, Zn(acac)2 was appliedas zinc precursor due to its high thermal stability, less reactivitytoward nucleophilic agents and easy evaporation compared toother organometallic precursors. Besides, thermal decompositionof zinc acetylacetonate produces CO2, H2O, acetone, and ZnO.Thus they have less risk for operator safety and environmentalcontamination [12].

Fig. 1. SEM images of the Zn(acac)2 sublimated at 110 (a), 120 (b), 130 (c), and 140 1

120 (f), 130 (g), and 140 1C (h).

Please cite this article as: Soofivand F, et al. Novel precursor-assisnanofibers. Mater Lett (2013), http://dx.doi.org/10.1016/j.matlet.201

The Zn(acac)2 powder was sublimated at 110, 120, 130 and140 1C, and denoted as samples A, B, C, and D, respectively.Fig. 1a–d illustrate SEM images of the Zn(acac)2 sublimated inthe range of 110–140 1C, correspondingly. Fig. 1a and b showsthat the Zn(acac)2 nanofibers obtained at 110 (sample A) and120 1C (sample B) are intertwined. The diameter of the nanofibersof the sample B is more than that of the sample A. The length ofthe nanofibers obtained from the samples A and B is inexpressibledue to the high rugosity of the nanofibers. Therefore, it is difficultto estimate the length of the nanofibers. When the Zn(acac)2

powder was sublimated at 130 1C (sample C), the morphology ofthe products was nanorods with a diameter of 80–90 nm andlength of 2–3 mm (Fig. 1c). Fig. 1d shows the SEM image of the

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C (d), and ZnO nanostructures synthesized from Zn(acac)2 sublimated at 110 (e),





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Fig. 2. (a,b) TEM images, and (c) EDS spectrum of the ZnO nanoparticles synthesized from the Zn(acac)2 sublimated at 120 1C as precursor.

Fig. 3. XRD patterns of the Zn(acac)2 sublimated at 110 1C (a), and ZnO

nanoparticles (b).

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Zn(acac)2 sublimated at 140 1C (sample D). The formation ofmicro-sized rods with high agglomeration is seen in Fig. 1d.According to Fig. 1a–d, it was found that by increasing thesublimation temperature, the diameter of the Zn(acac)2 nanofi-bers increased. To produce ZnO nanostructures, the as-producedZn(acac)2 nanostructures (samples A–D) were used as precursor.SEM images of the ZnO nanostructures generated through solid-state thermal decomposition process of the samples A–D areshown in Fig. 1e–h. As shown in Fig. 1e, ZnO nanobundles wereformed by thermal decomposition of the precursor provided at110 1C. The morphology of the ZnO obtained from the precursorprovided at 120 1C is composed of nanoparticles and nanorods(Fig. 1f). Thermal decomposition of the Zn(acac)2 powder sub-limated at 130 and 140 1C led to the formation of ZnO nanopar-ticles (Fig. 1g and h). In fact, the 1-D nanostructures disappearedcompletely, and uniform ZnO nanoparticles were obtained.

TEM images of the ZnO nanoparticles obtained from the sampleB are shown in Fig. 2a and b. The particle size of the product isbetween 10 and 12 nm. SAED pattern of the ZnO nanoparticles isshown in the inset. The rings are characteristic of well-crystallizedpolycrystals. EDS spectrum of the ZnO nanoparticles presented inFig. 2c shows only the presence of Zn element in the product.

XRD patterns of the Zn(acac)2 sublimated at 110 1C (sample A)and ZnO nanoparticles are presented in Fig. 3a and b, respectively.The diffraction peaks observed in Fig. 3a and b can be indexed topure monoclinic phase zinc bis(acetylacetonate) hydrate (JCPDScard no. 41-1634) and hexagonal phase zinc oxide (JCPDS card no.70-0207), respectively.

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4. Conclusions

In this work, a free solvent and template-less method isintroduced for the preparation of ZnO nanofibers and nanoparticles.


The sublimated Zn(acac)2 powders at different temperatures wereapplied as zinc precursor. Solid-state thermal decomposition of theZn(acac)2 nanostructures at 400 1C has led to the fabrication of ZnOnanostructures. This method can be developed to prepare variousmorphologies of metal oxides.

Acknowledgment

Authors are grateful to the council of University of Kashan forsupporting this work by Grant no. (159271/58).





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novel precursor-assisted synthesis and characterization of zinc oxide nanoparticles/nanofibers

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