"Two dimensional CdSe Quantum Well Nanoplatelets: Living Polymerization and Doping" by Dr. Santanu Jana, Marie Curie Research Fellow, Laboratoire de Chimie, ENS de Lyon, France and Laboratoire de Physique des Solides, Universite Paris-Sud, France.
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| Colloidal nanoplatelets (NPLs), which are also known as colloidal quantum wells, have recently received much attention due to their outstanding optical properties such as tunable, very sharp (full-width at half-maximum ~8 nm) emission, faster carrier recombination than that of quantum dots and rods, and low-threshold lasing properties. One of the current challenges is to self-assemble these colloidal quantum wells into large ordered structures to control their collective optical properties. This aspect is important in the perspective of exploiting the optical properties of NPL such as ultra-fast FRET, where accurate relative nanoparticle positioning is required. Here we demonstrate a simple strategy to induce the selfassembly of CdSe NPL into micron-long threads by adding small amounts of oleic acid (OA) to a NPL dispersion, followed by slow drying which behave like a polymer. The gap between NPLs’ is consisting and repeated along the longitudinal direction. Fine-tuning of the length of these nanoparticle polymers is achieved by varying the experimental conditions. These structures are flexible since they are composed of a single platelet in their lateral dimension and continuously break and reform in solution similar to living polymers formed by some surfactants. Optical fluorescence microscopy, transmission electron microscopy provide detailed structural characterization and show that threads can be composed by highly organized 100 to 1000 NPLs. Changing the size of the platelet we 1st time produce helical like assembly of NPLs by using excess capping agent and different drying process. We also extended our study of NPL assembly by using doping with Cu2+ in NPLs. Surprisingly after doping it gives emission in NIR region where the Stoke’s shift is very high ~150 nm and above. Due to higher emission efficiency and larger stock’s shift we use them for luminescent solar concentrator where this NP concentrator gave the solar output efficiency more than 7%. |
