Synthesis and application of semiconductor quantum dots in novel sensing applications

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] This thesis details the synthesis of CdSe/ZnS semiconductor nanocrystals (quantum dots). These quantum dots (QDs) show very interesting optical properties of broadband excitation with narrow emission and excellent resistance to photo-degradation. These unique optical properties make them suitable for a wide variety of applications, particularly biosensing applications. In this work, QDs were synthesized by two commonly used approaches with unique modifications. These QDs are of very high quality as shown by their spectral linewidth and fluorescent quantum yield. These QDs prove to be excellent energy donors for Förster Resonant Energy Transfer (FRET) applications. A variety of methods are explored to functionalize these QDs to make them water soluble and to enable the linking of these QDs to other molecules of interest. The most promising method is a new multi-step method in which the QDs are coated first with an acid layer and then with a silica layer. This coating scheme is shown to be very stable in a variety of aqueous solutions, implying that it may be more useful in long term studies. These water-soluble QDs are then used in a variety of bio-applications. These applications, while promising, are unfortunately hampered by the current lack of understanding of the surface chemistry of this novel functionalization scheme.