Femtosecond ligand/core dynamics of microwave-assisted synthesized silicon quantum dots in aqueous solution.
Femtosecond ligand/core dynamics of microwave-assisted synthesized silicon quantum dots in aqueous solution.
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DOI：
10.1021/ja207344u
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发表时间：
2011-12-28
影响因子：
15
通讯作者：
Kauzlarich, Susan M.
中科院分区：
文献类型：
--
作者：
Atkins, Tonya M.;Thibert, Arthur;Larsen, Delmar S.;Dey, Sanchita;Browning, Nigel D.;Kauzlarich, Susan M.
利用微波辅助反应制备了氢封端的硅量子点。通过两种不同的方法钝化的硅量子点的水溶性：氢化硅烷化产生的3-氨基丙烯基封端和一个修改的Stöber过程中产生的二氧化硅封装的硅量子点。每种方法产生在414 nm处具有最大发射的水溶性QD，并且在纯化后分别表现出15%和23%的固有荧光量子产率效率。尽管量子点具有不同的表面，但它们表现出几乎相同的吸收和荧光光谱。飞秒瞬态吸收光谱被用来在时间上解决量子点和配体之间的光激发载流子动力学。3-氨基丙烯基封端的Si量子点的瞬态动力学被解释为碳连接体的离域π电子与Si核心激子之间的激发态电荷转移（CT）态的形成和衰减。这种CT状态在恢复到更稳定的长寿命物质之前稳定约4 ns。二氧化硅封装的Si量子点显示出更简单的光谱，没有CT动力学。
A microwave-assisted reaction has been developed to produce hydrogen-terminated silicon (Si) quantum dots (QDs). The Si QDs were passivated for water solubility via two different methods: hydrosilylation produced 3-aminopropenyl-terminated and a modified Stöber process produced silica-encapsulated Si QDs. Each method produces water soluble QDs with maximum emission at 414 nm and after purification exhibit intrinsic fluorescence quantum yield efficiencies of 15 % and 23 %, respectively. Even though the QDs have different surfaces, they exhibit near identical absorption and fluorescent spectra. Femtosecond transient absorption spectroscopy was used to temporally resolve the photoexcited carrier dynamics between the QDs and ligand. The transient dynamics of the 3-aminopropenyl-terminated Si QDs is interpreted as a formation and decay of an excited-state charge transfer (CT) state between the delocalized π electrons of the carbon linker with the Si core excitons. This CT state is stable for ~4 ns before reverting back to a more stable long-living species. The silica-encapsulated Si QDs show a simpler spectrum without CT dynamics.
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