Application of quantum dots for developing multicolor hybrid nanoprobes towards stable and specific analysis of nanoscale materials

As one of sensitive signal that has highest cross section area (10 -16cm2/molecule), fluorescence is widely used in analytical chemistry. For analysis of target materials, fluorophores are incorporated with target materials directly or with probes, which have specificity to the target materials. After following procedures such as separation, target materials are identified by analyzing intensity and color of obtained emission from the fluorophore. Mostly, organic fluorophores have been used. However, they have some intrinsic limitations such as instability against photobleaching, cross-talk to neighboring colors and specific excitation wavelengths, which lead to sophisticated instrumentation for multiple excitations. During recent decades, nanomaterials with novel optical, electromagnetic and biological properties have been synthesized to overcome conventional drawbacks in biological, electrical or medical applications. Among them, inorganic fluorescent nanocrystals called quantum dots have been applied successfully to analytical chemistry because of the novel optical properties such as broad energy range for multi-excitation and stable and narrow symmetric emission with high extinction and quantum efficiency. The large surface area to volume ratio enables the integration of these fluorescent dots with functional molecules for specific and sensitive communication with other complementary substrates. Hence, this dissertation investigates the use of quantum dots towards developing hybrid nanoprobes for analysis of nanoscale materials such as DNA and carbon nanotubes, which have significant impact on modern science or engineering.; For developing multicolor hybrid nanoprobes for target DNA detection, molecular beacons were conjugated with multicolor QDs. The hybrid nanoprobes showed long term stability and specificity to the target DNA. Multicolor gel electrophoresis was developed by using the hybrid nanoprobes. The developed multicolor gel electrophoresis could detect up to 8ng of target DNA with single base mismatched discrimination.; For an analysis of single wall carbon nanotubes (SWNT), a visualization technology was developed. Sodium-dodecyl-sulfonate (SDS) dissolved only SWNT selectively from contaminations and multiwall carbon nanotubes in an aqueous buffer. The hybrid probe made of QDs and SDS layer, which made stable suspension of SWNT, was applied to characterize quality of different SWNT samples by using fluorescent microscopy.