Enhancement of Photoluminescence from Organic and Inorganic Surface Passivated ZnS Quantum Dots

Abstract

ZnS quantum dots (QDs) chemically synthesized in PVP stabilizing medium have been coated with Zn(OH)2, SiO2and polystyrene (PS) shells as inorganic and organic passivation agents. to synthesize ZnS/Zn(OH)2, ZnS/SiO2and ZnS/PS QDs. PL properties of inorganically passivated ZnS/Zn(OH)2 and ZnS/SiO2 had reported band edge enhancement of 8-10 times, while organically passivated ZnS/PS QDs exhibit tremendous enhancement of band edge emission as much as 10-15 times,. Therefore inorganic and organic coating can passivate trap states of different energies on the surface of ZnS QDs.

Synthesis of Nano-ZnS Modified Porous Si with White Light Photoluminescence Properties

“…This broad green-blue photoluminescence band has often been attributed to the surface states or crystal lattice vacancies in nano-ZnS and its intensity increased with the amount of nano-ZnS. [7][8][9] From time-resolved PL, decay times of the unmodified and modified samples were obtained. For the sake of simplicity, we assume that only one component is involved in the recombination process.…”

“…As soon as nano-ZnS was deposited into PS, the decay time dropped from s to ns with increasing deposition coverage. The decay time of nano-ZnS is 30-80 ns at 1.9 eV and thus the decreased decay time of nano-ZnS/PS is assumed to be related to recombination arising from traps in nano-ZnS 8) in the PS host. This means that after deposition, the light comes from the recombination of carriers confined in nano-ZnS rather than in the PS host.…”

White light luminescence from nano-ZnS doped porous silicon

“…PS samples were immersed in a solution of ZnSO 4 /deionized water for 12 h, and the samples were then dried in air for 0.5-1 h. This allowed a layer of ZnSO 4 to be deposited into the PS. Then, ZnS nano-particles inside the pores were formed by exposing the samples to a vapour flow of H 2 S for 12 h, followed by thermal annealing (350 • C for 5 min) [10,11]. Similar wet chemical methods were used to produce nano-ZnS particles [12,13].…”

“…The Zn 2+ inside the PS hosts reacted with the H 2 S gas to form nano-ZnS according to the following equation Zn 2+ + H 2 S → ZnS. The size of the nano-particles is estimated to be about 2 nm [11], and the density of the nano-ZnS is a function of the deposited ZnSO 4 concentration.…”

Luminescent properties of ZnS:Mn2+ nanocrystals/SiO2 hybrid phosphor synthesized by in situ surface modification co-precipitation

“…Therefore, if silica coating is applied on doped nanocrystals, we can expect luminescent enhancement as well as an improved resistance to electron bombardment. Recently, ZnS nanocrystals coated with SiO 2 were prepared using tetraethyl orthosilicate (TEOS) [13,14] or SiO 2 nanoparticles [15]. ZnS:Mn 2+ nanocrystals embedded in SiO 2 are also synthesized by sol-gel method, using TEOS [16,17].…”