Luminescence spectroscopy of nanocrystalline MgO

Abstract

MgO nano‐powder was synthesized using the combustion method and was studied by low temperature VUV spectroscopy under synchrotron radiation excitation. A considerable blue shift (by ∼0.6 eV, see the figure) of UV luminescence excited in intrinsic absorption was revealed in nanocrystalline MgO ceramics. This dense ceramics consists of large (10‐20 µm size) blocks and can be formed already at 1600 °C, i.e. far below the melting point of MgO. According to XRD studies, thermal treatment increased the size of nanocrystallites from 24 to 80 nm. In bulk MgO single crystals the UV luminescence (≥5 eV) is due to the recombination of electrons and holes near V‐centres, whereas nanocrystalline MgO ceramics with high surface to volume ratio facilitate the formation of the surface self‐trapped excitons, which decay radiatively. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

12.4: Surface Exciton Properties of MgO in ZnO‐MgO Core‐Shell Quantum‐Dots

“…The excitation spectrum ( figure 3), for the 215 nm emission from MgO:Si (300 ppm) at 16 K shows two sharp peaks at 7.678 eV (161.5 nm) and 7.779 eV (159.4 nm) respectively, which we assign to the n=1 and n=2 exciton energy values, in accordance with the experimental results found by Feldbach [25].…”

Biocompatible and Biodegradable Magnesium Oxide Nanoparticles with In Vitro Photostable Near-Infrared Emission: Short-Term Fluorescent Markers

“…However the PL spectrum of commercial MgO NPs revealed lines above 800 nm while ball-milled MgO revealed lines at 688 nm and 700 nm. The zero phonon line (ZPL) assigned as the magnetic—dipole no-phonon 2E-4A2 transition with the lines at 688 nm and 700 nm have been attributed to Cr 3+ substitutional defects in cubic (R-line) and non-cubic (N-line), respectively; observed only during the 532 nm excitation [23]. These lines are followed by broad fluorescence with a maximum around 800 nm that is reported to be independent of the excitation wavelength [23].…”

“…The zero phonon line (ZPL) assigned as the magnetic—dipole no-phonon 2E-4A2 transition with the lines at 688 nm and 700 nm have been attributed to Cr 3+ substitutional defects in cubic (R-line) and non-cubic (N-line), respectively; observed only during the 532 nm excitation [23]. These lines are followed by broad fluorescence with a maximum around 800 nm that is reported to be independent of the excitation wavelength [23]. The MgO (100) crystal, grown by arc melting, is known to contain chromium impurities [22].…”

“…Extensive defect photoluminescence studies on different forms of MgO have been performed since the late 1960s. These include studies on single crystal [22], nanocrystalline [23] and thin film [23]. MgO synthesised by a multitude of methods.…”