Wilcoxon Jess P, Provencio P P
Nanostructures and Advanced Materials Chemistry, Department 1122, Sandia National Laboratories, Albuquerque, NM 87185-1421, USA.
J Phys Chem B. 2005 Jul 21;109(28):13461-71. doi: 10.1021/jp050062h.
We apply a variety of characterization tools, including dynamic light scattering (DLS), transmission electron microscopy (TEM), high-resolution size-exclusion chromatography (HRSEC), and X-ray fluorescence (XRF), to study CdSe and CdSe/ZnS semiconductor nanocrystals of various sizes. We compare the size monodispersity, composition, and optical properties such as absorbance, photoluminescence (PL), and photoluminescence excitation of samples synthesized by high-temperature organometallic decomposition methods to CdSe clusters synthesized in our laboratory using a room-temperature metathesis from ionic precursors in coordinating solvents. DLS revealed considerable aggregation in all the conventionally synthesized samples, while TEM showed significant size and shape polydispersity in the core/shell CdSe/ZnS nanoparticles. We demonstrate how HRSEC can be used to explore size and shape polydispersity in semiconductor nanocrystals by measurement of the spectral homogeneity of the PL and PLE of spectra obtained within cluster elution peaks observed by HRSEC. Using HRSEC, we show that size fractionation by solvent/nonsolvent precipitation is only partially effective in size selection and that discrete size populations are present in each fraction. HRSEC shows that our synthesis yields a single-size, blue-emitting, homogeneous population whose absorbance and PL correspond to those of the smallest-size fraction made by conventional synthesis. This suggests that especially stable discrete sizes are favored in both synthetic methods.
我们应用了多种表征工具，包括动态光散射（DLS）、透射电子显微镜（TEM）、高分辨率尺寸排阻色谱（HRSEC）和X射线荧光（XRF），来研究各种尺寸的CdSe和CdSe/ZnS半导体纳米晶体。我们将通过高温有机金属分解方法合成的样品的尺寸单分散性、组成和光学性质（如吸光度、光致发光（PL）和光致发光激发）与我们实验室使用室温复分解法从配位溶剂中的离子前体合成的CdSe簇进行比较。DLS显示所有传统合成样品中都存在大量聚集，而TEM显示核壳CdSe/ZnS纳米颗粒中存在显著的尺寸和形状多分散性。我们展示了如何通过测量HRSEC观察到的簇洗脱峰内获得的光谱的PL和PLE的光谱均匀性，利用HRSEC来探索半导体纳米晶体中的尺寸和形状多分散性。使用HRSEC，我们表明通过溶剂/非溶剂沉淀进行的尺寸分级在尺寸选择上仅部分有效，并且每个级分中都存在离散的尺寸群体。HRSEC表明我们的合成产生了单一尺寸、蓝色发光、均匀的群体，其吸光度和PL与传统合成方法制备的最小尺寸级分的吸光度和PL相对应。这表明在两种合成方法中，特别稳定的离散尺寸是有利的。
