title: The effects of post-processing on the surface and the optical properties of copper indium sulfide quantum dots.
abstract: In the current contribution we report on investigations regarding the surface of CuInS2 quantum dots and on different strategies to control the amount of surface ligands in a post-processing step. In particular, the reactivity of the organic components, that is, 1-dodecanthiol and 1-octadecene as ligand and solvent, respectively, during nanocrystal formation was studied. A new method to remove residuals from the reaction mixture and to detach excess organics from the surface of the nanocrystals is reported. Our new method, which is based on the utilization of acids, is compared with standard purification procedures by means of thermogravimetric analysis (TGA) with particular focus on its efficiency to remove organics. As a complement, the surface chemistry is analyzed by nuclear magnetic resonance spectroscopy (NMR) to shed light on the nature of the organic components still present after purification. Further analysis of the product by inductively coupled plasma optical emission spectroscopy (ICP-OES) is performed to verify the influence of the new purification method on surface composition and properties. Moreover, steady state and time resolved spectroscopies give insights into excitonic behavior as well as recombination processes. Finally, the new method is optimized for the purification of CuInS2-ZnS nanocrystals, which show enhanced optical properties.
authors: Institute of Particle Technology (LFG), Friedrich-Alexander-University Erlangen-Nuremberg, Cauerstr. 4, 91058 Erlangen, Germany; Center for Functional Particle Systems, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Tugce
authors: T
authors: Akdas
authors: Institute of Particle Technology (LFG), Friedrich-Alexander-University Erlangen-Nuremberg, Cauerstr. 4, 91058 Erlangen, Germany; Center for Functional Particle Systems, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Monica
authors: M
authors: Distaso
authors: Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Susanne
authors: S
authors: Kuhri
authors: Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science and Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Benjamin
authors: B
authors: Winter
authors: Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science and Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Balaji
authors: B
authors: Birajdar
authors: Center for Nanoanalysis and Electron Microscopy (CENEM), Department of Materials Science and Engineering, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Erdmann
authors: E
authors: Spiecker
authors: Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany.
authors: Dirk M
authors: DM
authors: Guldi
authors: Institute of Particle Technology (LFG), Friedrich-Alexander-University Erlangen-Nuremberg, Cauerstr. 4, 91058 Erlangen, Germany; Center for Functional Particle Systems, Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany. Electronic address: wolfgang.peukert@fau.de.
authors: Wolfgang
authors: W
authors: Peukert
keywords: Optical properties; Post-processing; Purification; Quantum dots; Surface analysis