Enhancement of photoluminescence of ZnS:Mn nanocrystals modified by surfactants with phosphate or carboxyl groups via a reverse micelle method

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• 作者：Kubo ; T. ; Isobe ; T. ; Senna ; M.
• 关键词：78.55.&ndash ; m ; 78.55.Et ; 81.05.Dz ; 81.20.Ka ; 82.70. &ndash ; y ; 82.70.Dd ; ZnS ; Mn ; Nanocrystals ; Reverse micelle ; Photoluminescence ; Energy transfer
• 刊名：Journal of Luminescence
• 出版年：2002
• 出版时间：August, 2002
• 年：2002
• 卷：99
• 期：1
• 页码：39-45
• 全文大小：163 K

文摘

A colloidal suspension of ZnS:Mn nanocrystals was prepared in sodium bis(2-ethylhexyl)suflosuccinate reverse micelles, and then modified by surfactants with phosphate or carboxyl groups. The photoluminescent intensity at 580nm due to d–d transition of Mn²⁺ ions increases up to a factor of 6.3 and its quantum efficiency increases from 1.7 % to 8.1 % after modification. According to ³¹P nuclear magnetic resonance spectra, surfactants with phosphate groups adsorb on the surface of ZnS nanocrystal and ³¹P nucleus spins are relaxed rapidly by interaction with five unpaired 3d electrons of Mn²⁺, showing that phosphate groups are located in the vicinity of Mn²⁺. The excitation spectra for the emission due to phosphate or carboxyl groups are similar to those for the emission at 580nm corresponding to the excitation of ZnS. Both excitation spectra shift in parallel with increasing the amount of surfactant to show the linear relationship. We, therefore, attribute the increase in quantum efficiency at 580nm to additional energy transfer of ZnS→functional groups→Mn²⁺ as well as to the reduction of energy loss due to non-radiative transition by surface modification.