Design, preparation and characterization of mixed semiconductor nanocrystal-salt crystals as extremely photostable and highly efficient light emitting materials for optical applications

极高的光致发光量子产率（PL QY）和在应用相关条件下尽可能高的光稳定性是将半导体（SC）纳米晶体（NC）用作光学器件中的荧光标记物和活性组分的先决条件。实现和维持高PL QY的典型方法是将SCNC封装到稳健且透明的基质中。为此，我们建议使用无机盐（例如NaCl、KCl、KJ、NH 4J等）。晶格和折射率变化的晶体作为基质，用于包埋具有不同材料组成和表面化学的胶体SCNC，在可见光和红外光谱区发射，并将这些盐晶体整合到聚合物中。无机盐晶体对SCNC的PL QY和光稳定性的保护和增强作用在我们的第一个初步研究中显示。该项目的目的是系统研究我们新开发的结晶方法与不同类型SCNC的兼容性。这些将在水溶液和有机溶液中制备，然后进行表面化学表征。我们将应用复杂的光学表征方法，从而比较分散体中SCNC的光学性质和光化学稳定性，在盐基质中，对于选定的系统，也作为盐作为盐基质-聚合物复合材料。待研究的NC将包括含Cd材料，如CdTe、CdSe、CdHgTe或PbS，以及潜在毒性较小的材料，如InP和CuInS（Se）。特别强调的是，将致力于获得高发射和光稳定SCNC盐晶体复合结构的设计可能适用于固态照明，发光太阳能聚光器以及强大的近红外和红外发射源的结构-性能关系。为此，我们还将开发这些不同散射SCNC盐晶体系统的PL QY的绝对测量方法。

Extremely high photoluminescence quantum yields (PL QY) and as high as possible photostability under application-relevant conditions are prerequisites for the use of semiconductor (SC) nanocrystals (NCs) as fluorescent labels and active components in optical devices. A typical approach to achieve and maintain a high PL QY is the encapsulation of SCNCs into robust and transparent matrices. For this purpose, we propose to use inorganic salt (e.g. NaCl, KCl, KJ, NH4J, etc.) crystals varying in crystal lattice and refractive index as matrices for embedding colloidal SCNCs of varying material composition and surface chemistry with emission in the visible and the infrared spectral region and the integration of these salt crystals into polymers. The protective and enhancing influence of inorganic salt crystals on the PL QY of SCNCs and their photostability was shown in first preliminary studies by us. The aim of the proposed project is the systematic study of the compatibility of our newly developed crystallization approaches with different types of SCNCs. Those will be prepared in aqueous and in organic solutions followed by characterization of the surface chemistries. We will apply sophisticated optical characterization methods, thereby comparing the optical properties and photochemical stability of the SCNCs in dispersion, in the salt matrix and, for selected systems, also as salt matrix-polymer composite materials. The NCs to be studied will include Cd-containing materials like CdTe; CdSe, CdHgTe or PbS and potentially less toxic materials like InP and CuInS(Se). Special emphasis will be dedicated to derive structure-property relations for the design of highly emissive and photostable SCNC-salt crystal composite structures potentially applicable for solid state lighting, luminescent solar concentrators as well as robust NIR and IR emission sources. For this purpose, we will also develop methods for the absolute measurement of PL QY of these differently scattering SCNC-salt crystal systems.