Tunable blue-green-emitting wurtzite ZnS:Mg nanosheet-assembled hierarchical spheres for near-UV white LEDs

Abstract

Mg-doped ZnS hierarchical spheres have been synthesized via hydrothermal method using mixed solvents of ethylenediamine and DI water without any surface-active agent. The surface morphology and microstructure studies revealed that the hierarchical spheres were consisted of many well-aligned nanosheets with width 10 nm and length about 50 ~ 100 nm. X-Ray diffraction results show that the ZnS:Mg hierarchical spheres have wurtzite structure with high crystallinity. The absorption edge in the diffuse reflection spectra shifts towards lower wavelength with increasing Mg concentration, indicating an expansion in the bandgap energy that is estimated to be in the range of 3.28 to 3.47 eV. Blue-green photoluminescence with tunable intensity and peak position was observed depending on the Mg content. The Mg2+-activated ZnS phosphor can be good candidates for blue-green components in near-UV white light-emitting diodes.

White light tunable emissions from ZnS: Eu3+nanophosphors over 330–465 nm excitation range for white LED applications

“…Also, Eu 3+ is the most stable isotope of europium at higher temperatures (Sharma et al 2006) and so was not expected to be reduced to the Eu 2+ in a sulfurizing atmosphere. Moreover, as earlier noted, point defects and surface states are found to be the major contributors to the broad band emission in ZnS (Fang et al 2011, Reddy et al 2014, Zeng et al 2015.…”

Luminescent properties of fine-dispersed self-propagating high-temperature synthesized ZnS:Cu,Mg

“…The volume of the unit cell, in which Mg is inserted, decreases due to shorter ion radius of Mg. Consequently, mechanical stress and deformation of ZnS lattice occur. Furthermore, introduction of magnesium can change the phase ratio in ZnS [19]. It is well known [11,20] that introduction of copper usually stabilizes the cubic phase, but introduction of magnesium stabilizes the hexagonal phase, according to [21].…”

“…Probably, it is caused by increasing in the degree of ZnS lattice deformation in processes of magnesium introduction, because the ionic radius of Mg is much less than that of Zn and Cu. According to [19], Mg ions can partially fill tetrahedral interstitial sites or replace Zn in ZnS lattice. The volume of the unit cell, in which Mg is inserted, decreases due to shorter ion radius of Mg. Consequently, mechanical stress and deformation of ZnS lattice occur.…”

Reduced graphene oxide wrapped ZnS–Ag2S ternary composites synthesized via hydrothermal method: Applications in photocatalyst degradation of organic pollutants

“…The emission band located at 449 nm was an internal sulfur vacancy (V S ) -assisted band that was caused by a transition from the sulfur vacancy state to the valence band edge state of ZnS [39]. The green emission band at 524 nm was attributed to zinc vacancies located on the surfaces of the nanoparticles [45]. The orange emission band located at 620 nm was attributed to the transition from sulfur vacancies to interstitial sulfur states and recombination of interstitial zinc states and zinc vacancies [46].…”