| This dissertation discusses the creation of functional nanomaterials for ultrasensitive chemical analysis and biological detection. Because of their unique optical, magnetic, and electrical properties, nanomaterials could potentially impact several research areas. In particular, semiconductor and metal nanoparticles are of considerable interest not only because of their unique optical properties, but also because of their size similarities with biomolecules. By coupling macromolecules with nanoparticles we have created functional nanomaterials that can act as spectroscopic enhancers, fluorescence quenchers, and biological labels.; A small percentage of these metal nanoparticles can be used a spectroscopic enhancers. Molecules adsorbed on the metallic nanoparticles are amplified by surface-enhance Raman scattering (SERS) to give a molecular fingerprint. This enhancement overcomes the inefficiencies of Raman scattering and leads to the detection of single molecules at room temperature. However, only 1 out of 100 particles is SERS-active. By using nanopore membranes, we have developed nanoparticle thin films by separating SERS-active nanoparticles from inactive ones. These thin films are highly efficient for optical enhancement. In addition, the size-dependent properties of metal nanoparticles were investigated with a near-infrared laser source. The results indicate that a majority of these SERS-active particles are large nanoaggregates.; Metal nanoparticles can also be used as quenchers in fluorescence based detection assays. An important insight came from previous surface-enhanced Raman scattering (SERS), which showed that fluorescent dyes could reversibly adsorb on the surface of metal nanoparticles. When adsorbed on the surface, the fluorescence emission from the dye remains quenched. However, as the dye desorbs and distances itself from the surface fluorescence is restored. Here, conformational changes in the DNA structure are monitored by a change in the fluorescence as the fluorophores and nanoparticle separate. Compared to conventional oligonucleotide probes, these nanoparticle quenchers display similar signals and provide new opportunities to investigate the quenching abilities of metal nanoparticles.; Finally, semiconductor nanoparticles (quantum dots) can be used to target receptors on cancer cells. Folic acid molecules conjugated to quantum dots can bind to the folate receptor, a known tumor marker, and enter the cancer cells by endocytosis. Clusters of quantum dots are clearly visible inside living cells. These initial studies indicate that quantum dots should find use as contrast agents in the emerging area of molecular imaging. |
