Novel type-II nanocrystal quantum dots and versatile oligomeric phosphine ligands

This thesis describes the syntheses, characterizations, and applications of novel type-II quantum dots and versatile oligomeric phosphine ligands. Type-II band engineered quantum dots (CdTe/CdSe(core/shell) and CdSe/ZnTe(core/shell) heterostructures) are synthesized by chemical means. The optical properties of these type-II quantum dots are studied in parallel with their type-I counterparts. The spatial distributions of carriers are controlled within the type-II quantum dots, which make their properties strongly governed by the band offset of the comprising materials. This allows access to optical transition energies that are not restricted to bandgap energies. The type-II quantum dots can emit at lower energies than the bandgaps of comprising materials. The type-II emission can be tailored by the shell thickness as well as the core size. The enhanced control over the carrier distributions afforded by these type-II materials is useful for many applications such as photovoltaics, and photoconduction devices. A new family of oligomeric alkyl phosphine ligands is synthesized for quantum dots. These oligomeric phosphines show effective binding affinity to quantum dot surfaces. They form thin and secure organic shells that stabilize quantum dots in diverse environments. They maintain high photoluminescence quantum yield of the quantum dots, and enable homogeneous incorporation into various matrices. They present a chemically flexible structure that can be used for further chemistry, such as crosslinking, co-polymerization, and conjugation to biomolecules. Selection of optimal quantum dot wavelengths for biomedical assays and imaging is studied by simple mathematical modeling.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Kim, Sungjee, 1972-

Advisor dc:contributor.advisor

• Moungi G. Bawendi.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/30017

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/30017