Unsaturated Ligands Seed an Order to Disorder Transition in Mixed Ligand Shells of CdSe/CdS Quantum Dots
| Autor: | Erin A. O’Brien, A. Paul Alivisatos, Jacob H. Olshansky, Hui-Ling Han, Gabor A. Somorjai, Arunima D. Balan, Yonatan Horowitz, Lucio Tang |
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| Rok vydání: | 2019 |
| Předmět: |
Phase transition
Materials science Photoluminescence Infrared Shell (structure) interligand interactions General Physics and Astronomy Quantum yield 02 engineering and technology QD surface chemistry 010402 general chemistry 01 natural sciences Quantitative Biology::Subcellular Processes General Materials Science Nanoscience & Nanotechnology ligand phase transition Spectroscopy temperature-dependent photoluminescence Ligand digestive oral and skin physiology General Engineering 021001 nanoscience & nanotechnology 0104 chemical sciences Crystallography Quantum dot CdSe/CdS quantum dots 0210 nano-technology |
| Zdroj: | ACS nano, vol 13, iss 12 |
| ISSN: | 1936-086X 1936-0851 |
| DOI: | 10.1021/acsnano.9b03054 |
| Popis: | A phase transition within the ligand shell of core/shell quantum dots is studied in the prototypical system of colloidal CdSe/CdS quantum dots with a ligand shell composed of bound oleate (OA) and octadecylphosphonate (ODPA). The ligand shell composition is tuned using a ligand exchange procedure and quantified through proton NMR spectroscopy. Temperature-dependent photoluminescence spectroscopy reveals a signature of a phase transition within the organic ligand shell. Surprisingly, the ligand order to disorder phase transition triggers an abrupt increase in the photoluminescence quantum yield (PLQY) and full-width at half-maximum (FWHM) with increasing temperature. The temperature and width of the phase transition show a clear dependence on ligand shell composition, such that QDs with higher ODPA fractions have sharper phase transitions that occur at higher temperatures. In order to gain a molecular understanding of the changes in ligand ordering, Fourier transform infrared and vibrational sum frequency generation spectroscopies are performed. These measurements confirm that an order/disorder transition in the ligand shell tracks with the photoluminescence changes that accompany theligand phase transition. The phase transition is simulated through a lattice model that suggests that the ligand shell is well-mixed and does not have completely segregated domains of OA and ODPA. Furthermore, we show that the unsaturated chains of OA seed disorder within the ligand shell. |
| Databáze: | OpenAIRE |
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