| The prosperities of nanoscience and nanotechnology have promoted the development of science in all fields. Light scattering technology in analytical chemistry supply much more opportunities and challenges in this evolution for analysts. Combining nanoscience in light scattering detection and establishing light scattering analytical methods based on nanotechnology would have new ways in analytical chemistry. In this thesis, silver nanoparticles (Ag-Nps), which have unique localized surface plasmon resonance scattering properties, have been investigated by interacting with drugs and biomolecules. Thus, new analytical methods based on the scattering of Ag-Nps have been established. The mainly points are as follows:1. Citrate-capped silver nanopartilces with small size were synthesized, and a visual colorimetric method for the detection of berberine hydrochloride was proposed based on the color change caused by the aggregation of Ag-Nps. It was found that citrate-capped AgNps dispersed in water owing to the electrostatic repulsion from each other by the negative charged surface, presenting a bright yellow color. However, the presence of positively charged berberine could induce the aggregation of citrate-capped AgNps, resulting in color change from yellow to green, and even to blue depending on the concentration of berberine. The mechanism of color change and the effect of experiment condition were studied with UV-Vis absorption and light scattering spectrometry. Under the optimum condition, we can detect the berberine hydrochloride from 0.05μM to 0.4μM visually based on the color changes of the solution. It was identified that this colorimetric analytical method without use of expensive machines is very convenient, economy and speedy. 2. We synthesized larger Ag-Nps, which have strong scattering properties considering that Ag-Nps have strong localized surface plasmon resonance scattering signals. A novel, label-free visual immunoassay method, based on the PRS signals of the Ag-NP electrostatic adsorbed on glass slides, on which antibody is bound, has been established to distinguish the immunoreactions on glass slides with a common LED torch. We discussed the mechanism of this method and investigated the effect of experimental conditions with the scattering signals of Ag- NPs measured on a common spectrofluorometer. Under optimal conditions, antibody over the range between 10 and 160 ng/mL with LOD of 5.6 ng/mL could be detected quantitatively with spectrofluorometer. If a white light-emitting diode (LED) torch is employed to illuminate the glass slides, we can make visual detection of the antibody by the naked eye, owing to the strong localized surface plasmon resonance signals scattered from the Ag-Nps.3. We propose a localized surface plasmon resonance scattering immunoassay with common glass slides as a solid substrate by introducing Ag-Nps as scattering labels. The light scatting signals of silver nanoparticles could be measured with a common spectrofluorometer for clinical purposes. The quantitative study using human IgG as an antigen showed that the present immunoassay could have comparable high sensitivity with the new reported chemiluminescence immunoassays. On the other hand, the dark-field light scattering microscopic images showed that single silver nanoparticles can be clearly seen on the basis of its strong scattering light, indicating that silver nanoparticles as a light scattering probe may become a novel model in bioassay. Moreover, the scattering light from the AgNPs has different colors depending on the sizes and shapes, which has potential application in multiplexed assay using nanoparticles with different scattering colors. The localized surface plasmon resonance scattering features of a single AgNP, on the other hand, deserve further investigation and perhaps have potential applications in analytical chemistry. In addition, the visual immunoassay system could be constructed and easily observed by naked eyes with a common LED touch, supplying a new way for visual detection of immunoreactions on the basis of the light scattering signals.4. The further investigation is on the localized surface plasmon resonance scattering features of Ag-Nps etched by iodine. We found that iodine ions can be adsorbed on the Ag-Nps surface in the presence of iodine ions in colloidal Ag-Nps suspension, and induce the localized surface plasmon resonance absorption and scattering quenching of Ag-NPs. However, if both iodine ions and copper ions were presented, iodine ions can be oxidized to iodine which can etch Ag-Nps causing the disappearance of localized surface plasmon resonance scattering. The features of Ag-Nps immobilized on glass slides before and after the interaction of iodine were further investigated with scanning electron microscopy and dark-field light scattering microscope. It was found that, the size of Ag-Nps gets enlarged and the surface of Ag-Nps gets roughness after the etching of iodine. The light scattered from the Ag-Nps after etching changed from blue light to white light. An analytical method for iodine thus can be established using a common spectrofluorometer based on the light scattering change of Ag-Nps etched by iodine. The strong scattering light induced from the etching of Ag-Nps by iodine will have potential application in biochemical analysis.In conclusion, localized surface plasmon resonance absorption and scattering features of Ag-Nps with different sizes were investigated in this thesis. The interactions between Ag-NPs and drugs/biomolecule were studied using light scattering spectral and microscopy methods. A series novel analytical methods based on the localized surface plasmon resonance scattering of Ag-Nps were established to detect drugs and biomolecules, and it is obviously that light scattering method on silver nanoparticles shows high promise in analytical chemistry.
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