The development and application of fluorenscent nanomaterials for trace determination of analytes

Rapid development in nanoscience and nanotechnology has led to the dawn of a wide variety of nanomaterials. The properties and applications of these materials have not yet been fully explored. Likewise, the development of new types of nanomaterials is still needed. In particular, there is high demand for new photosensitive nanomaterials for detection of trace amount of analytes. Therefore, this dissertation focuses on the development of new photosensitive nanomaterials, the study of their properties and the application of these nanomaterials in trace analysis. Two types of these nanomaterials were studied, zinc-induced fluorescent silica nanoparticles and gold nanorods. The synthesis and stability of the gold nanorods were studied in detail. The application of zinc-induced fluorescent nanoparticles was for in situ determinations of intracellular zinc, and the gold nanorods were used to enhance the fluorescence of near-infrared dye molecules for detection of DNA target.;In order to develop a zinc-induced fluorescent silica nanoparticle, silica nanoparticles were synthesized through the reverse micro-emulsion method. This was followed by immobilizing a zinc-sensing ligand, CDAPAP, on the surface of amine modified silica nanoparticles. In the presence of zinc, this nanoparticle produced a fluorescence emission. The presence of intracellular zinc was monitored in situ by observing cell samples under the fluorescence microscope.;After a comprehensive literature review of gold nanorod synthesis and applications, a number of parameters for synthesis and stability of gold nanorods were explored. Gold nanorods have unique absorption spectra with two peaks corresponding to the transverse and longitudinal plasmon resonances. The position of the longitudinal plasmon band is related to the aspect ratio of the gold nanorods. This aspect ratio was adjusted by slight changes of reagent concentrations or reaction conditions.;Synthesis parameters studied were the amount of L-ascorbic acid, preparation method of gold seeds, age of gold seeds, and reaction temperature. It was found that the size and absorbance of the resulting gold nanorods increased as the molar ratio of L-ascorbic acid : Au(III) increased from 1.1:1 to 1.5:1. Furthermore, as the size increased the aspect ratio decreased. However, a ratio >1.5:1 was found to increase the aspect ratio and transmission electron microscopy showed that the morphology of the resulting nanorods changed from rod shaped to dog-bone shaped.;Gold nanorods were synthesized and stabilized by surfactant, CTAB. The optimum concentration was found to be 0.01 M CTAB. The gold nanorod samples have displayed remarkable stability with no significant change in absorbance or wavelength position over a period of eight months. Stability in acidic and neutral conditions was observed, however in basic conditions there was a dramatic loss of absorbance.;In the final portion of this dissertation, gold nanorods were employed as substrates for metal enhanced fluorescence. A near-infrared dye was selected as a modifier for thiolated DNA. The CTAB was replaced on the gold nanorod surface by a phase transfer ligand exchange process which allowed the gold surface to be accessible for the thiolated DNA. Various lengths of DNA were studied to find the appropriate length of the spacer between the metal and dye to observe metal enhanced fluorescence. It was found that longest chain provided enhanced fluorescence.