Montalti Marco, Prodi Luca, Zaccheroni Nelsi, Falini Giuseppe
Dipartimento di Chimica G. Ciamician, Via Selmi 2, 40126 Bologna, Italy.
J Am Chem Soc. 2002 Nov 13;124(45):13540-6. doi: 10.1021/ja027270x.
In this paper we show how it is possible to control the nature and the efficiency of collective photophysical processes in a network composed of two different fluorescent units organized on the surface of silica nanoparticles. Such a structure is obtained by covering nanoparticles with a layer of dansyl moieties (Dns) and by partially protonating them in solution. The two fluorophores Dns and Dns.H(+) have very different photophysical properties and can be selectively excited and detected. The interaction between the two units Dns and Dns.H(+) has been first investigated in a reference compound obtained by derivatizing 1,6-hexanediamine with two dansyl units. The photophysical characterization of this compound (absorption spectra, fluorescence spectra, quantum yield, and lifetime) showed that the two moieties can be involved both in energy and electron-transfer processes. Dansylated nanoparticles were prepared by modifying preformed silica nanoparticles with dansylated (3-aminopropyl)trimethoxysilane. Photophysical studies indicated that protonation has a dramatic effect on the fluorescence of the nanoparticles, leading to the quenching of both the protonated units and the surrounding nonprotonated ones. This amplified response to protonation, due to charge-transfer interactions, is solvent-dependent and is less efficient in pure chloroform with respect to acetonitrile/chloroform (5/1 v/v) mixtures. The reduced efficiency of the electron-transfer processes responsible for the quenching makes energy transfer competitive to such an extent that in pure chloroform excitation energy migration takes place from Dns.H(+) to Dns with great efficiency.
在本文中，我们展示了如何在由组织在二氧化硅纳米颗粒表面的两种不同荧光单元组成的网络中控制集体光物理过程的性质和效率。这种结构是通过用一层丹磺酰基部分（Dns）覆盖纳米颗粒并在溶液中使其部分质子化而获得的。两种荧光团Dns和Dns.H(+)具有非常不同的光物理性质，并且可以被选择性地激发和检测。首先在通过用两个丹磺酰基单元衍生化1,6 - 己二胺得到的参考化合物中研究了两个单元Dns和Dns.H(+)之间的相互作用。该化合物的光物理表征（吸收光谱、荧光光谱、量子产率和寿命）表明，这两个部分都可以参与能量和电子转移过程。通过用丹磺酰化的（3 - 氨丙基）三甲氧基硅烷修饰预先形成的二氧化硅纳米颗粒来制备丹磺酰化的纳米颗粒。光物理研究表明，质子化对纳米颗粒的荧光有显著影响，导致质子化单元和周围未质子化单元的猝灭。由于电荷转移相互作用，这种对质子化的放大响应是溶剂依赖性的，并且相对于乙腈/氯仿（5/1 v/v）混合物，在纯氯仿中效率较低。负责猝灭的电子转移过程效率的降低使得能量转移具有竞争力，以至于在纯氯仿中激发能量从Dns.H(+)高效地迁移到Dns。
