Abstract
The synthesis and optical properties of Mg-Al layered double hydroxide (LDH) precursor powders were investigated using X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution TEM (HRTEM), UV-transmission spectrometer, and fluorescence spectrophotometer. The FT-IR results show that the intense absorption at around 1363–1377 cm-1 can be assigned to the antisymmetric ν3 mode of interlayer carbonate anions because the LDH phase contains some CO32-. The XRD results show that all of the Mg-Al LDH precursor powders contain only a single phase of [Mg0.833Al0.167(OH)2](CO3)0.083·(H2O)0.75 but have broad and weak intensities of peaks. All of Mg-Al LDHs precursor powders before calcination have the same photoluminescence (PL) spectra. Moreover, these spectra were excited at λex = 235 nm, and the broad emission band was in the range 325-650 nm. In the range, there were relatively strong intensity at around 360, 407 and 510 nm, respectively.
Highlights
The general formula of layered double hydroxide (LDH) can be represented as follows (Khan and O’Hare 2002; Costa et al.2005; Goh et al 2008):[M21+-xP3x+ (OH)2]ξ+(Anξ-/n) mH2O (1)where M2+ is a divalent metal ion such as Mg2+, Zn2+, and so on, while P3+ is a trivalent ion such as Al3+, Cr3+, and so on
The Mg-Al LDH precursors were synthesized by a coprecipitation route with various processes
The following analytical grade preliminary materials were used as reagents for the synthesis of the MgAl LDH precursors: Mg(NO3)2·6H2O, Al(NO3)3·9H2O, NaOH, and Na2CO3
Summary
The general formula of LDHs can be represented as follows (Khan and O’Hare 2002; Costa et al.2005; Goh et al 2008):[M21+-xP3x+ (OH)2]ξ+(Anξ-/n) mH2O (1)where M2+ is a divalent metal ion such as Mg2+, Zn2+, and so on, while P3+ is a trivalent ion such as Al3+, Cr3+, and so on. LDHs have applications as ion-exchangers (Dimotakis and Pinnavaia 1990; You et al 2002), absorbents (Hermosin et al 1996; Huston et al 2004), pharmaceutics (Hwang et al 2001; Wang et al 2005), catalysts or catalyst supports (Choudary et al 2002; Motokura et al 2004), and sunscreens for cosmetic use (Cursino et al 2013)
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