Federal Institute for Materials Research and Testing (BAM), Division Biophotonics, Richard-Willstaetter-Str. 11, 12489 Berlin, Germany.
Nanoscale. 2018 Apr 19;10(15):7147-7154. doi: 10.1039/c7nr09332b.
Comparing the photoluminescence (PL) properties of ensembles of nanocrystals like semiconductor quantum dots (QDs) with single particle studies is of increasing interest for many applications of these materials as reporters in bioimaging studies performed under very dilute conditions or even at the single particle level. Particularly relevant is here the PL quantum yield (ΦF), which determines the signal size together with the reporter's molar extinction coefficient and is a direct measure for nanocrystal quality, especially for the inorganic surface passivation shell and its tightness, which can be correlated also with nanocrystal stability and the possible release of heavy metal ions. Exemplarily for red and green emitting CdTe nanocrystals, we present a method for the determination of ΦF of nanoparticle dispersions at ultralow concentration compared to cuvette measurements using fluorescence correlation spectroscopy (FCS), a single molecule method, and compared to molecular dyes with closely matching spectral properties and known ΦF. Our results underline the potential of this approach, provided that material-inherent limitations like ligand- and QD-specific aggregation affecting particle diffusion and QD drawbacks such as their complex and power-dependent blinking behavior are properly considered as shown here.
将纳米晶体（如半导体量子点 (QD)）的聚集体的光致发光 (PL) 特性与单粒子研究进行比较，对于这些材料在非常稀释的条件下甚至在单粒子水平下作为生物成像研究中的报告器的许多应用来说，越来越具有吸引力。在这里，特别相关的是 PL 量子产率 (ΦF)，它与报告器的摩尔消光系数一起决定信号大小，是纳米晶体质量的直接衡量标准，特别是对于无机表面钝化壳及其紧密性，这也可以与纳米晶体稳定性和重金属离子的可能释放相关联。我们以红色和绿色发射的 CdTe 纳米晶体为例，提出了一种在超低浓度下使用荧光相关光谱 (FCS) 与比色皿测量相比测定纳米颗粒分散体的 ΦF 的方法，该方法是一种单分子方法，并与具有紧密匹配光谱特性和已知 ΦF 的分子染料进行了比较。我们的结果强调了这种方法的潜力，前提是要适当考虑材料内在的限制，例如配体和 QD 特异性聚集会影响颗粒扩散，以及 QD 的缺点，例如其复杂且与功率相关的闪烁行为，如这里所示。
