Abstract
We use wet treatment to integrate red-luminescent Si nanoparticles with Mg-based wide-bandgap insulators Mg(OH) and MgO (5.7 and 7.3 eV respectively). In the process, Mg2+ is reduced on Si nanoparticle clusters, while suffering combustion in water, producing a spatially inhomogeneous Mg(OH)2/MgO-Si nanoparticle composite with an inner material predominantly made of Si, and a coating consisting predominantly of magnesium and oxygen (“core-shell” geometry). The nanocomposite exhibit luminescence covering nearly entire visible range. Results are consistent with formation of Mg(OH)2/MgO phase with direct 3.43-eV bandgap matching that of Si, with in-gap blue-green emitting states of charged Mg and O vacancies. Bandgap match with nanocomposite architecture affords strong enough coupling for the materials to nearly act as a single hybrid material with novel luminescence for photonic and photovoltaic applications.
Highlights
Magnesium[1,2,3] and its compounds, such as wide-band gap insulators magnesium oxide and magnesium hydroxide (7.8 and 5.7 eV respectively) have received wide scientific interest in the last decade as they have applications in catalysis,[4] toxic waste remediation,[5] additives in refractory, paint, superconductor products,[6,7,8] and in steel manufacturing because of its high corrosion-resistant behavior.[9]
055324-3 Kocyigit et al FIG. 1. (a) Luminescent photos of colloids after interaction of silicon nanoparticles with Mg2+ ions Si nanoparticles in isopropanol alcohol and Mg2+ in water after seven hours of mixing the components. It clearly shows clustering and precipitation and a change in color observed by naked eye from the red towards the yellow control solution in the absence of water where the magnesium salt is dissolved in isopropyl alcohol (IPA) instead of water
055324-7 Kocyigit et al We studied the photoluminescence from a thin film, which was formed by drop drying of a certain volume of the reaction solution on a glass substrate kept at a temperature of 40 ◦C
Summary
The synthesis of MgO nanostructures, on the other hand, may be carried out from Mg(OH)[2] by simple thermal treatment (at 350 ◦C) which releases water molecules. The nanocomposite exhibit luminescence covering the entire visible: red, green and blue (RGB). Those optical features are consistent with formation of an intermediate Mg(OH)2/MgO phase of a low direct bandgap (3.43 eV) with enhanced formation of charged states of Mg and O vacancies that allow strong electronic coupling and integration with the 3.4-eV direct bandgap Si-based material, making the two material act nearly as a single hybrid material. Composite architecture affords novel luminescence for photonic and photovoltaic applications
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