I. Metal nanoparticles on high surface area latex supports: Preparation and applications, and, II. Modified semiconductor quantum dots as luminescent label for in situ hybridizations

In Chapter 1, catalytically important metallic nanoparticles (1–20 nm) have been synthesized using various facile methods. The nanoparticles were then supported on various functionalized polymeric latex spheres (400 nm–1 μm) using one step adsorption from the prefabricated colloidal solution. A number of surface functionalities (NH₂, COOH, OH) have been probed vis-à-vis their affinity to metallic nanoparticles and the resulting materials fully characterized using TEM, EDX, and UV-VIS. The rigid and highly stable poly (4-vinylpyridine) nanospheres with exposed pyridine nitrogen on the surface serve as an excellent support for Pd0 nanoparticles in the range of 1–4 nm. Four wt. percent palladium-coated nanospheres serve as good catalysts for Suzuki-, Heck-, and Stille-type coupling reactions for carbon-carbon bond formation. For the second application, aminated microspheres derivatized with palladium nanoparticles were used to grow multilayers of viologen with appropriate Zr4+ spacers and the resulting system tested for their activity in hydrogen peroxide formation from dissolved hydrogen and oxygen (Chapter 2).; In Chapter 3, high temperature synthesis of luminescent multicolor (500–650 nm) CdSe semiconductor quantum dots of different sizes (2–5 nm) is performed using modifications of a literature procedure. The core CdSe dots are then capped by ZnS (∼2 nm) shell to enhance their luminescence efficiency. The core and core shell dot (QDs) surface was then modified with different functional groups (NH₂, COOH, OH) using various bifunctional linkers to render it water soluble and the relative stability under the physiological pH range has been studied. To make functional dots, we covalently attach them to amine group at 5′ end of appropriate oligonucleotide sequence (typically, 21–24 base long, alphoid repeat sequence based probes) using either an amide or a carbamate linkage. The resulting QD-oligonucleotide conjugates were then studied for their stability against hydrolysis and binding efficiency. Highly luminescent, non-bleaching and photostable multicolor QD-oligonucleotide conjugates were then used as probes for chromosomal analysis using FISH (fluorescence in-situ hybridization) procedures (Chapter 4).