Semiconductor nanocrystals with adjustable hole acceptors: tuning the fluorescence intensity by metal-ion binding.
Semiconductor nanocrystals with adjustable hole acceptors: tuning the fluorescence intensity by metal-ion binding.
复制标题
DOI：
10.1002/anie.201001441
复制
发表时间：
2010-09
影响因子：
--
通讯作者：
Jessica Völker;Xiaoyin Zhou;Xuedan Ma;Sandra Flessau;Hengwei Lin;M. Schmittel;A. Mews
中科院分区：
文献类型：
--
作者：
Jessica Völker;Xiaoyin Zhou;Xuedan Ma;Sandra Flessau;Hengwei Lin;M. Schmittel;A. Mews
半导体纳米晶体（NC）是一种稳健的无机发色团，其联合收割机结合了有效的宽带吸收和窄带荧光光谱。因此，它们在生物标记、[1]太阳能电池、[2，3]发光二极管[4]甚至传感器系统等有吸引力的应用中具有作为光敏系统的巨大潜力。[5-7]尽管这些应用中的大多数依赖于荧光波长的可调谐性，从而依赖于颗粒的尺寸，但传感器设备需要改变荧光强度，这在很大程度上取决于NC中的表面效应。由于荧光是由无机NC核内的光激发电子-空穴对（激子）的复合引起的，如果电荷载流子转移到表面结合的配体，则其强度降低。这个过程，涉及光诱导电子转移（PET），强烈依赖于能量的位置的NC的电子水平相对于那些的配体的分子轨道（MO）。多年来已经知道配体可以增加或降低NC的荧光强度。例如，对于众所周知的CdSe NCs，通过三辛基氧化膦（TOPO）的标准方法制备，[8]用胺取代TOPO配体会增加荧光强度，[9]而硫醇会导致完全的荧光淬灭。[10]对于碲化镉NC，通过类似的方法制备，情况是相反的：配体交换的TOPO硫醇导致荧光强度的增加。[10]荧光猝灭被认为是由于光激发的空穴从NC价带（VB）的顶部转移到所连接的配体的最高占据分子轨道（HOMO）。[10个国家]
Semiconductor nanocrystals (NCs) are robust inorganic chromophores that combine an efficient broadband absorption with a narrow-band fluorescence spectrum. Hence, they have a great potential as photoactive systems in attractive applications such as biolabeling,[1] solar cells,[2, 3] light-emitting diodes,[4] and even in sensor systems.[5–7] Whereas most of these applications rely on the tunability of the fluorescence wavelength and thus on the size of the particles, sensor devices require a change of the fluorescence intensity, which strongly depends on surface effects in NCs. As the fluorescence arises from the recombination of photoexcited electron–hole pairs (excitons) within the inorganic NC core, its intensity is lowered if charge carriers are transferred to surface-bound ligands. This process, involving a photoinduced electron transfer (PET), strongly depends on the energetic position of the electronic levels of the NC with respect to those of the molecular orbitals (MOs) of the ligands. It has been known for many years that ligands may either increase or decrease the fluorescence intensity of NCs. For example, for the well-known CdSe NCs, prepared by standard methods in trioctylphosphine oxide (TOPO),[8] the replacement of TOPO ligands by amines increases the fluorescence intensity,[9] whilst that by thiols leads to a complete fluorescence quenching.[10] For CdTe NCs, prepared by similar methods, the situation is reversed: ligand exchange of TOPO by thiols leads to an increase of the fluorescence intensity.[10] The fluorescence quenching is assumed to be due to a transfer of the photoexcited hole from the top of the NC valence band (VB) to the highest occupied molecular orbital (HOMO) of the attached ligand.[10]