Characterization of ZnMoO4 nanofibers synthesized by electrospinning–calcination combinations
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 Eg — 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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