Characterization of ZnMoO4 nanofibers synthesized by electrospinning–calcination combinations

doi:10.1016/j.matlet.2011.10.097

Materials Letters

Volume 68, 1 February 2012, Pages 265-268

https://doi.org/10.1016/j.matlet.2011.10.097 Get rights and content

Abstract

ZnMoO₄ nanofibers were synthesized by electrospinning–calcination combinations. In the present research, anorthic structured ZnMoO₄ was detected by X-ray diffraction (XRD) and confirmed by simulation and selected area electron diffraction (SAED). Morphology was confirmed by scanning and transmission electron microscopy (SEM, TEM) and atomic force microscopy (AFM). Vibrations were detected by Fourier transform infrared (FTIR) and Raman spectroscopy. By using photoluminescence (PL) and UV–visible spectroscopy, the PL emission was found to be in the same range as the indirect energy gap (E_g). A formation mechanism was proposed according to the experimental results.

Highlights

► ZnMoO₄ nanofibers as a semiconducting material. ► A lab-made electrospinning equipment enables us to form as-spun fibrous precursors. ► Upon calcination the precursors at 519 °C, ZnMoO₄ nanofibers were synthesized. ► A promising nanofibrous semiconductor for multiple potential applications.

Introduction

ZnMoO₄, a semiconducting material, exists as anorthic and monoclinic structures [1]. It contains non-heavy elements and Mo as high as 42.58 wt.%. It is nontoxic, and also is very attractive for its properties of luminescence, scintillation and photocatalysis, and for its use in battery electrodes and drug delivery systems [2], [3], [4], [5], [6]. Previously, ZnMoO₄ with rhombus sheet or flower-like structure, α-ZnMoO₄, and needle-like ZnMoO₄·0.8H₂O were successfully synthesized by simple hydrothermal crystallization reactions of (NH₄)₆Mo₇O₂₄·4H₂O and Zn(NO₃)₂·6H₂O solutions containing citric acid [4]. AMoO₄ with scheelite (A = Ca, Sr, Ba) and wolframite (A = Mg, Mn, Zn) structures were synthesized by conventional mixed oxide calcination method [2]; nanocrystalline wolframite-structured MMoO₄ (M = Ni, Zn) phosphors by a modified citrate complex route assisted by microwave irradiation [3]; ZnMoO₄ hollow microspheres by yeast-directed hydrothermal synthesis of Zn(AC)₂ and Na₂MoO₄ in aqueous solution [5]; and ZnBO₄ (B = W, Mo) single crystals by the Czochralski method [6]. In the present research, anorthic ZnMoO₄ nanofibers were successfully synthesized by electrospinning–calcination combinations. To the best of our knowledge, no ZnMoO₄ nanofibers have ever been synthesized by the present processes. This success may lead to large-scale production in the near future.

Section snippets

Experiment

To synthesize ZnMoO₄ nanofibers, 0.003 mol Zn(CH₃COO)₂·2H₂O, 0.003 mol (NH₄)₆Mo₇O₂₄·4H₂O, and 1.5 g poly (vinyl alcohol) (PVA) with the molar mass of 72,000 g/mol were dissolved in 30 ml deionized water, and vigorously stirred at 80 °C for 30 min. The mixture was electrospun through a horizontal hollow needle, biased with + 15 kV direct voltage to synthesize a fibrous web on a grounded aluminum foil. These fibers were subsequently calcined at 300, 400, 519, and 600 °C for 3, 6, and 9 h, for further

Phase analysis

A comparison of XRD patterns (Fig. 1a) to those of JCPDS No. 35–0765 [1] revealed that they corresponded to anorthic (triclinic [7]) structured ZnMoO₄ with P-1 space group. Some PVA seemed to remain in the P4003 product. The PVA peak at 2θ of 22.5° [8] could be covered by the peaks of ZnMoO₄; but for the P5193, P5196 and P5199, no PVA was in existence on the products [8]. The nanofibers were the best crystal quality, with their atoms residing in a perfect crystal lattice. The lengths of

Conclusions

ZnMoO₄-PVA fibers were successfully synthesized by electrospinning of Zn(CH₃COO)₂·2H₂O, (NH₄)₆Mo₇O₂₄·4H₂O, and PVA mixture. To form ZnMoO₄ nanofibers, the as-spun fibers were subsequently calcined at 519 °C for 3, 6 and 9 h. The PL emission of the P5193 was in the same range as the 3.3 eV indirect E_g — a promising value for scintillation and luminescence.

Acknowledgements

We wish to thank the National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency, for providing financial support through the project code: P-10-11345, and the Thailand Research Fund (TRF) through the RGJ-Ph.D. Program, and the TRF Basic Research Grant, including Graduate School of Chiang Mai University through the general support.

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View full text

Characterization of ZnMoO4 nanofibers synthesized by electrospinning–calcination combinations

Abstract

Highlights

Introduction

Section snippets

Experiment

Phase analysis

Conclusions

Acknowledgements

J Eur Ceram Soc

Mater Lett

J Cryst Growth

Nucl Instrum Methods Phys Res A

J Alloys Compd

J Non-Cryst Solids

Opt Mater

Opt Mater

Characterization of ZnMoO₄ nanofibers synthesized by electrospinning–calcination combinations