Rezvani Azita, Wang Zhuang, Wegner K David, Soltanmoradi Hadi, Kichigin Alexander, Zhou Xin, Gantenberg Tobias, Schram Juergen, Apeleo Zubiri Benjamin, Spiecker Erdmann, Walter Johannes, Resch-Genger Ute, Segets Doris
Chair for Particle Science and Technology, Institute for Energy and Materials Processes (EMPI-PST), University of Duisburg-Essen (UDE), Duisburg 47057, Germany.
Division Biophotonics, Federal Institute of Materials Research and Testing (BAM), Berlin 12489, Germany.
ACS Nano. 2025 May 27;19(20):19080-19094. doi: 10.1021/acsnano.4c18530. Epub 2025 May 12.
Semiconductor quantum dots (QDs) possess unique electronic and optical properties, making them promising candidates for applications in light-emitting diodes, solar cells, bioimaging, and photocatalysis. Precise control over their size, shape, and chemical and electronic structure is crucial to ensure the desired functional properties and optimize device performance. However, challenges in QD synthesis and post-synthesis modification persist, especially in large-scale production. This study addresses the classification of QDs synthesized in a tubular flow reactor consisting of a mixture of the desired InP/ZnS core-shell QDs and QDs made from the shell material, i.e., here ZnS QDs formed as a byproduct during the formation step of the ZnS shell. The homogeneous nucleation of ZnS nanoparticles from the shelling material introduces a heterogeneity in size and composition and affects the optical properties of the resulting QDs. To address this issue, we developed a size-selective agglomeration (SSA) technique by incrementally introducing ethanol as a poor solvent and classified the synthesized QDs into 13 distinct fractions. These 13 fractions are sorted into three distinct groups: (i) larger InP/ZnS QDs, (ii) a combination of smaller InP/ZnS QDs and larger ZnS QDs, and (iii) predominant ZnS QDs with some very tiny InP/ZnS QDs. The comprehensive characterization of the fractions was conducted using UV-visible absorption spectroscopy, photoluminescence spectroscopy, high-resolution scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, total reflection X-ray fluorescence, and analytical ultracentrifugation. We could demonstrate that our method effectively separated unwanted ZnS QDs from the target InP/ZnS QDs. In addition, the fractions enriched in smaller InP/ZnS QDs exhibited a higher photoluminescence quantum yield compared to the fractions with larger QDs. This demonstrates the efficacy of SSA in fine-tuning the composition of QD mixtures produced on a larger scale to improve their functional properties. This approach provides fundamental understanding toward the development of a scalable two-dimensional classification process for such ultrasmall nanoparticles by particle size and composition.
半导体量子点（QDs）具有独特的电子和光学特性，使其成为发光二极管、太阳能电池、生物成像和光催化等应用的有前途的候选材料。精确控制其尺寸、形状以及化学和电子结构对于确保所需的功能特性和优化器件性能至关重要。然而，量子点合成和合成后修饰方面的挑战仍然存在，特别是在大规模生产中。本研究解决了在管式流动反应器中合成的量子点的分类问题，该反应器中包含所需的InP/ZnS核壳量子点与由壳材料制成的量子点的混合物，即此处ZnS量子点是在ZnS壳层形成步骤中作为副产物形成的。来自壳层材料的ZnS纳米颗粒的均匀成核引入了尺寸和组成的不均匀性，并影响了所得量子点的光学特性。为了解决这个问题，我们通过逐步引入作为不良溶剂的乙醇开发了一种尺寸选择性团聚（SSA）技术，并将合成的量子点分类为13个不同的级分。这13个级分被分为三个不同的组：（i）较大的InP/ZnS量子点，（ii）较小的InP/ZnS量子点和较大的ZnS量子点的组合，以及（iii）主要是ZnS量子点和一些非常小的InP/ZnS量子点。使用紫外可见吸收光谱、光致发光光谱、高分辨率扫描透射电子显微镜、能量色散X射线光谱、全反射X射线荧光和分析超速离心对这些级分进行了全面表征。我们可以证明我们的方法有效地将不需要的ZnS量子点与目标InP/ZnS量子点分离。此外，与较大量子点的级分相比，富含较小InP/ZnS量子点的级分表现出更高的光致发光量子产率。这证明了SSA在微调大规模生产的量子点混合物组成以改善其功能特性方面的有效性。这种方法为通过粒径和组成开发这种超小纳米颗粒的可扩展二维分类过程提供了基本的理解。
