Mechanism of the electrophoretic assembly of CdSe nanocrystal films and their mechanical properties

by Jia, Shengguo, Ph.D., COLUMBIA UNIVERSITY, 2008, 210 pages; 3317564

Abstract:

This thesis consists of two closely related experimental studies of electrophoretically deposited CdSe nanocrystal films.

In the first part of this thesis, the charging of CdSe nanocrystal in non-aqueous solvent and the mechanism of electrophoretic deposition (EPD) are discussed from the point of view of the influence of the nanocrystal surface. Our experiments show that the charge of these nanocrystals originates from the surface defects of the nanocrystal. EPD leads to equally thick films of CdSe nanocrystals on both positive and negative electrodes due to the deposition of equal numbers of negatively and positively charged nanocrystals, even though their concentrations are not equal in solution. The deposition stops when the charged nanocrystals with lower concentration are depleted.

The second part of this thesis focuses on the mechanical and optical properties of these electrophoretically deposited CdSe nanocrystal films.

Approaches to measure and analyze the mechanical parameters and fracture properties of electrophoretically deposited CdSe nanocrystal films are described in this part. The values of the elastic modulus of electrophoretically deposited CdSe nanocrystal films composed of 3.2 nm diameter nanocrystals measured by Raman microprobe scattering (∼9.7 GPa) and nanoindentation (∼10 GPa) match each other. The mechanical response of nanocrystal films suggests polymeric features that are attributable to the organic ligand on the nanocrystal cores. After nanocrystal cross-linking and partial ligand removal, the nanocrystal films exhibit more features of granularity. The fracture, strain, and stress of electrophoretically deposited CdSe nanocrystal films are studied as a function of the film thickness, nanocrystal size, and drying method.

In addition to Raman microprobe scattering, optical methods such as photoluminescence, high-spatial resolution infrared spectroscopy, and ellipsometry are used to investigate the properties of these electrophoretically deposited CdSe nanocrystal films.

AdviserIrving P. Herman
SchoolCOLUMBIA UNIVERSITY
Source TypeDissertation
SubjectsCondensed matter physics; Materials science
Publication Number3317564

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