Heafey Eve, Laferrière Marie, Scaiano J C
Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Photochem Photobiol Sci. 2007 May;6(5):580-4. doi: 10.1039/b616616d. Epub 2007 Feb 13.
The quenching of core and core-shell CdSe quantum dots by TEMPO and 4-amino-TEMPO has been examined using steady state fluorescence spectroscopy. The efficiency of quenching is strongly dependent on the nanoparticle size, the binding properties of the nitroxide, and the presence or not of a protective shell, ZnS in our systems. The shell reduces the quenching efficiency significantly only in the case of binding nitroxides, such as 4-amino-TEMPO. Downward quenching plots revealing bimodal quenching characterize the Stern-Volmer plots obtained for 4-amino-TEMPO. The slope characteristic of the low concentrations regime depends strongly on the presence of a shell. For example, for particles with a 2.4 nm core, emitting at 525 nm the concentrations of 4-amino-TEMPO required to reduce the emission to one half are 0.65 microM and 0.08 mM for core and core-shell nanoparticles, respectively. Surprisingly, in the high concentration regime, a single Stern-Volmer slope of about 4000 M-1 seems to accommodate all systems. We speculate that this value is characteristic of the exchange of TOPO ligands by 4-amino-TEMPO.
利用稳态荧光光谱研究了TEMPO和4-氨基-TEMPO对核及核壳型CdSe量子点的猝灭作用。猝灭效率强烈依赖于纳米颗粒尺寸、氮氧化物的结合特性以及我们体系中保护壳（ZnS）的有无。仅在结合氮氧化物（如4-氨基-TEMPO）的情况下，壳才会显著降低猝灭效率。揭示双峰猝灭的向下猝灭图表征了4-氨基-TEMPO得到的Stern-Volmer图。低浓度区域的斜率特性强烈依赖于壳的存在。例如，对于核直径为2.4 nm、在525 nm处发射的颗粒，将核及核壳型纳米颗粒的发射降低一半所需的4-氨基-TEMPO浓度分别为0.65 μM和0.08 mM。令人惊讶的是，在高浓度区域，约4000 M-1的单一Stern-Volmer斜率似乎适用于所有体系。我们推测该值是4-氨基-TEMPO取代TOPO配体的特征值。
