Ji Xin, Wang Wentao, Mattoussi Hedi
Department of Chemistry and Biochemistry, Florida State University, 95 Chieftan Way, Tallahassee, Florida 32306, USA.
Phys Chem Chem Phys. 2015 Apr 21;17(15):10108-17. doi: 10.1039/c5cp00462d.
We explored the effects of changing the separation distance on the charge transfer interactions between luminescent QD and proximal dopamine (in QD-dopamine assemblies), and the ensuing photoluminescence (PL) quenching. The separation distance was controlled using a tunable size bridge between the QD and dopamine via a poly(ethylene glycol) (PEG) chain where the average number of monomers was discretely varied. Using steady-state and time-resolved fluorescence measurements, we found that the photoluminescence losses were substantially more pronounced for QD-dopamine complexes prepared with the shortest PEG bridge, but progressively decreased with increasing PEG size. We also found that the charge transfer interactions can be affected by the nature of the capping ligand used. In particular, we found that interactions and PL quenching in these assemblies tracked the effects of separation distance, conjugate valence and the energy mismatch between the dopamine redox levels and QD energy levels, when a compact zwitterion was used to control the conjugate configuration. However, additional effects of shielding the access of reactive dopamine to amine groups on the QD surface, when a longer inert PEG ligand was used, were found to produce heterogeneous conjugates, alter the interactions and produce weaker PL quenching.
我们探究了改变分离距离对发光量子点（QD）与近端多巴胺（在量子点 - 多巴胺组装体中）之间电荷转移相互作用以及随之产生的光致发光（PL）猝灭的影响。通过聚乙二醇（PEG）链在量子点和多巴胺之间使用可调尺寸的桥来控制分离距离，其中单体的平均数量离散变化。使用稳态和时间分辨荧光测量，我们发现对于用最短PEG桥制备的量子点 - 多巴胺复合物，光致发光损失明显更显著，但随着PEG尺寸增加而逐渐降低。我们还发现电荷转移相互作用会受到所用封端配体性质的影响。特别是，当使用紧密两性离子来控制共轭构型时，我们发现这些组装体中的相互作用和PL猝灭跟踪了分离距离、共轭价以及多巴胺氧化还原水平与量子点能级之间的能量失配的影响。然而，当使用更长的惰性PEG配体时，发现屏蔽反应性多巴胺接近量子点表面胺基的额外效应会产生异质缀合物，改变相互作用并产生较弱的PL猝灭。
