Effects of metal ion–ligand interactions on the synthesis of metal nanostructures with controlled morphology

Nanoparticle;Metal ion;Ligand;Precusor;Molecular design;Growth kinetics;Formation kinetics;Palladium (Pd);Platinum (Pt);Nanosheets;Nanoplates;Nanocubes

Yin, Xi

关键词: Nanoparticle;    Metal ion;    Ligand;    Precusor;    Molecular design;    Growth kinetics;    Formation kinetics;    Palladium (Pd);    Platinum (Pt);    Nanosheets;    Nanoplates;    Nanocubes;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/89171/YIN-DISSERTATION-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Nanoparticles with well-defined morphology and composition have been studied extensively for their applications in catalysis, energy conversion, and beyond. The unique properties of nanocrystals often highly depend on their shape, size, and composition. Therefore, control of morphology is essential in the development of nanocrystal-based materials.Design of nanocrystals, however, is still difficult in solution-phase synthesis, largely due to insufficient knowledge of the controlling parameters for the synthesis. For metal nanoparticles, the interactions between metal ions and commonly used ligands in solution-phase synthesis are still not clear, nor are the effects of these interactions on the formation of metal nanocrystals. It is crucial to improve our understanding of the formation mechanisms of metal nanocrystals in order to produce nanocrystals with controlled morphology.This dissertation focuses on the metal ion–ligand interactions and the effects of these interactions on the formation of metal nanocrystals during solution-phase synthesis. Formation of metal ion–ligand complexes were investigated for the synthesis of Pd and Pt nanocrystals. Structures of metal–ligand intermediates that formed were identified using single-crystal X-ray diffraction, mass spectrometry, and UV–vis spectroscopy. Two-dimensional multilayered Pd nanosheets, Pt nanocubes, and Pd nanoplates with controlled morphology were synthesized. The adsorption of metal intermediates and ligands on Pd surfaces was studied using density-functional theory (DFT) calculations. The effects of metal ion–ligand interactions on the formation kinetics of Pt and Pd nanocrystals were analyzed quantitatively. The experimental data show that the metal ion–ligand interaction affected the synthesis of metal nanocrystals through the formation of metal–ligand intermediates, which controlled the anisotropic growth and formation kinetics of metal nanocrystals. These results provide molecular level understanding of the formation mechanism of metal nanocrystals, indicating that design of molecular precursors is an important factor in controlling the morphology of metal nanostructures.