Preparation and characterization of dendrimer-encapsulated CdS semiconductor quantum dots
Preparation and characterization of dendrimer-encapsulated CdS semiconductor quantum dots
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DOI：
10.1021/ja0031321
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发表时间：
2000-12-27
影响因子：
15
通讯作者：
Crooks, RM
中科院分区：
文献类型：
--
作者：
Lemon, BI;Crooks, RM
我们报道了树突包封的CdS纳米颗粒（DE-CdS）的制备和表征。这些发光组件是用树状大分子作为纳米反应器和稳定剂制备的。也就是说，树突状分子首先充当隔离Cd2+离子的纳米反应器，然后在与s2反应后，通过防止团聚来稳定生成的CdS纳米颗粒。由于纳米粒子（或量子点，QD）的大小与用于制备它的树状分子模板的大小（或生成，G）有关，并且由于量子点的光学性质与尺寸相关，量子点的吸收和发射性质是用于制备它们的树状分子模板生成的函数。此外，树状大分子表面的众多反应基团可用于使复合材料在任何溶剂中溶解，包括水、有机溶剂、含氟相、2甚至超临界流体，3以及作为配体附着的合成手柄，将复合材料直接结合到表面、4生物配体、5 DNA、6、7和其他靶标上。最近描述了制备有用发光量子点的新方法。三个特别重要的发现与我们的工作有关。首先，发现了严密控制CdS和CdSe量子点大小的方法。例如，Bawendi报道的高温有机金属路线提供了对粒度和单分散性的高度控制。其次，研究发现，与未封顶的CdS或CdSe纳米晶体相比，“封顶”或核壳（例如（CdSe） ZnS）结构具有更高的稳定性和更高的量子效率。9-11最后，已经报道了将生物敏感结构附着到半导体表面的方法。12,13这些高度发光的纳米粒子具有优于有机染料的光物理特性（提高量子产率和光稳定性），但是合成它们所需的高温在某些应用中可能存在问题。研究还发现，生物活性基团的连接需要多个步骤，并且所得到的复合材料的量子产率低于未修饰的量子点。
We report the preparation and characterization of dendrimerencapsulated CdS nanoparticles (DE-CdS). These luminescent assemblies are prepared using dendrimers as both nanoreactor and stabilizer. That is, the dendrimer first acts as a nanoreactor that sequesters Cd2+ ions, and then after reaction with S2-it stabilizes the resulting CdS nanoparticles by preventing agglomeration. Because the size of the nanoparticle (or quantum dot, QD) is related to the size (or generation, G) of the dendrimer template used to prepare it, and because the optical properties of QDs are size-dependent, the absorptive and emissive properties of the QDs are a function of the generation of the dendrimer template used to prepare them. Additionally, the numerous reactive groups on the surface of the dendrimer can be used to render the composites soluble in essentially any solvent, including water, organic solvents, 1 fluorous phases, 2 and even supercritical fluids, 3 and as synthetic handles for attachment of ligands to direct binding of the composites to surfaces, 4 biological ligands, 5 DNA, 6, 7 and other targets.New methods for preparing useful luminescent QDs have recently been described. Three particularly significant findings are relevant to our work. First, means for closely controlling the size of CdS and CdSe QDs have been discovered. For example, the high-temperature organometallic route reported by Bawendi provides a high degree of control over both particle size and monodispersity. 8 Second, it was found that “capped” or coreshell (eg,(CdSe) ZnS) structures result in enhanced stability and much higher quantum efficiency compared to uncapped CdS or CdSe nanocrystals. 9-11 Finally, methods for attaching biologically sensitive structures to the semiconductor surface have been reported. 12, 13 These highly luminescent nanoparticles have photophysical properties superior to organic dyes (increased quantum yield and photostability), but the high temperature required to synthesize them can be problematic for some applications. It has also been found that attachment of biologically active groups requires multiple steps, and that the resulting composites have lower quantum yields than unmodified QDs.