Battistini Gionata, Cozzi Pier Giorgio, Jalkanen Jukka-Pekka, Montalti Marco, Prodi Luca, Zaccheroni Nelsi, Zerbetto Francesco
Dipartimento di Chimica G. Ciamician, Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy.
ACS Nano. 2008 Jan;2(1):77-84. doi: 10.1021/nn700241w.
Gold nanoparticles functionalized with chromophores are known to present unpredictable fluorescence as a function of their structure. Odd-even effects, based on the number of methylene units of the chain to which the fluorophore is attached, and the nature of the anchoring group on the gold surface have, in the past, been suggested to be responsible for the behavior. Here we investigate the fluorescence processes of two newly synthesized pyrene derivatives bound to gold nanoparticles. Two structurally identical ligands, differing only in the nature of the anchoring group (a thiolate in one case and an amine in the other), were newly synthetized and attached to the gold nanoparticles. The same changes in the fluorescence properties, namely, a red spectral shift with a moderate increase of the quantum yield and a shortening of the excited-state lifetime, are observed in the two cases and ascribed to the proximity of the gold core. By comparison with the results reported for other pyrene derivatives, it has been possible to draw the conclusions that (i) the nature of the binding group does not affect the fluorescence properties of the fluorophores attached to the nanoparticle surface and (ii) much stronger fluorescence is observed in the case of pyrene separated from the gold by short alkyl chain. The unusual behavior is explained in simple terms of competing chain-chain and chromophore-chromophore interactions and by means of proper energy diagrams.
已知用发色团功能化的金纳米颗粒会根据其结构呈现出不可预测的荧光。过去有人认为，基于连接荧光团的链中亚甲基单元的数量以及金表面锚定基团的性质所产生的奇偶效应是导致这种行为的原因。在此，我们研究了两种新合成的与金纳米颗粒结合的芘衍生物的荧光过程。新合成了两种结构相同的配体，它们仅在锚定基团的性质上有所不同（一种情况下是硫醇盐，另一种情况下是胺），并将它们连接到金纳米颗粒上。在这两种情况下都观察到了荧光性质的相同变化，即光谱红移，量子产率适度增加，激发态寿命缩短，这归因于金核的接近。通过与其他芘衍生物报道的结果进行比较，得出了以下结论：（i）结合基团的性质不会影响附着在纳米颗粒表面的荧光团的荧光性质；（ii）在芘通过短烷基链与金分离的情况下观察到更强的荧光。这种不寻常的行为可以用链 - 链和发色团 - 发色团相互作用的竞争以及适当的能量图简单解释。
