Sustainable Synthesis of Semiconductor Nanoparticles in a Continuous Flow Reactor
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Sustainable Synthesis of Semiconductor Nanoparticles in a Continuous Flow Reactor Daniel Ness1, Jan Niehaus1, Van-Huong Tran2 and Horst Weller1,2 1 CAN (Center for Applied Nanotechnology) GmbH 2 Institute of Physical Chemistry, University of Hamburg Grindelallee 117, 20146 Hamburg, Germany ABSTRACT Fulfilling the need for reproducible Quantum Dots (QDs) with certain spectroscopic features, high stability and luminescence we have established synthetic routes for the production of CdSe core as well as CdSe/shell particles in a continuous flow (cf) system. Our method features the deviation between nucleation and growth in two different parts of the system to mimic the well-known and often-used hot injection method for the synthesis of nanoparticles in organic solvents. INTRODUCTION Materials in the nanoscale range have gained tremendous interest not only in research areas but also in industry over the past twenty years. Their special properties arising from sizedependent attributes and a great variety in material composition have shown to be valuable in a range of different applications.[1] CdSe-based fluorescent NPs in particular found a great acceptance in a broad range of different research topics, e.g. in light emitting devices or lasers[2,3], for the use as light-harvesting particles in photovoltaic development[4] and as marker for biological systems like proteins or DNA.[5] Depending on the application customized material systems are needed to increase the stability, quantum yield or to allow a phase transfer into the desired media. For this reason methods for protective coating of the more or less instable core have been developed leading to structures with CdS, ZnS or CdS/ZnS as shell components among others.[6] The common strategy for the synthesis of QDs is based on a batch process called hotinjection method.[7] This procedure requires a high nucleation temperature, a fast cooling step to the growth temperature as well as immediate and complete mixing after the injection – altogether in one flask. Due to upcoming variations in mixing, temperature and material inhomogeneities together with injection speed up-scaling the synthesis is difficult and can lead to slightly different properties each time the reaction has been done. This issue can be addressed by performing the synthesis in a continuous flow reactor.[8] Many examples for the use of a continuous flow system show the benefits of this technique for small scale synthesis and research purposes.[9-12] Combining the utilization needs with the features of such a technical system for the production of NPs gives some crucial advantages over the common batch synthesis: • reaction conditions can simply be modified and adjusted • easy optimization of particle systems by rapid screening of parameters • avoiding wastage of expensive materials and time • high reproducibility of NP properties • online quality control by integrated spectroscopic units • enhancement of production even to the kg-scale possible
EXPERIMENT All steps were taken out under inertgas atmosphe
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