Studies On Analytical Applications Of Silver Triangle Nanoplates And Their Anisotropic Assembly

With the rapid development of nanoscience and nanotechnology, noble metal nanomaterials have been widely applied in various fields. Silver triangle nanoplates (STNPs) as a new type of nanomaterial, has attracted much attention and become a hot topic in the field of analytical chemistry, due to its special shape and unique adjustable surface plasmon resonance (SPR) properties. In this thesis, a light radiation method was introduced to synthesize STNPs with uniform shape and good monodispersity. Small biological molecules were used for inducing shape transformation and anisotropic assembly of the as-prepared STNPs. By using UV-Vis absorption spectroscopy, the SPR spectral features of STNPs and their assembly have been studied and a series of analytical methods based on the STNPs have been established. The main content of the thesis is as follows:1. We studied the influence of light radiation on the shape and absorption spectral properties of STNPs synthesized by common chemical reduce method. By exploring the effects of light source wavelength, irradiation time and initial status of STNPs on the absorption spectrum of STNPs, we found that the shape and absorption spectrum of STNPs would change after different wavelength of light irradiation. The absorption peak of STNPs would shift near to the wavelength of radiation light and the peak shift is independent to the initial state of the STNPs. With the increasing of illumination time, the absorbance of STNPs is increasing and the full width at half maxima (FWHM) of absorption peak is narrowing. The results indicated that the light radiation synthesized STNPs have uniform shape and good monodispersity.2. Light radiation synthesized STNPs were used for establishing a highly sensitive detection method for cysteine. As cysteine could etch the corners of STNPs and resulting in a blue shift of STNPs absorption peak, the light radiation synthesized STNPs, which has a narrow spectral peak, high absorbance and uniform particle size, would be etched by cysteine more easily and sensitively. The sensitivity of the method by using light radiation synthesized STNPs for cysteine detection is greatly improved up to10nM, which is16times sensitive than reported literature which used STNPs synthesized by chemical reduction method.3. We studied face-to-face assembly of STNP and their temperature-controlled disassembly. Experimental results indicated that STNPs face-to-face assembled together in a certain concentration of sodium citrate, resulting in blue-shifts of absorption peak and decrease of absorbance of STNPs. However, the face-to-face assembly of STNPs would be disassembled at high temperature. After a heating process, the absorption spectrum of STNPs assembly gradually red-shifted to the initial state, and the STNPs assembly disassembled to STNPs dispersion. We found a good linear relationship between heating temperature and the red-shift wavelength of STNPs assembly, and established a temperature sensor based on the STNPs disassembly process.4. We explored dopamine induced edge-by-edge assembly of silver triangle nanoplates. It was found that dopamine could interact with STNPs and forming a layer of polymer to pack STNPs under certain conditions. The packed STNPs connected together and formed edge-by-edge assembly of STNPs in solution. With the increasing of dopamine, the spectrum peaks of STNPs red-shifted and the absorbance reduced gradually. The color of STNPs changed from purple gradually to violet, blue, sky blue and light blue in the assembly process. Temperature is an important factor for assembly of STNPs, the higher reaction temperature, the shorter assembly time. Spectral studies of dopamine-induced edge-by-edge assembly of STNPs would provide more valuable information on anisotropic assembled of STNPs.5. Silver and gold alloy nanoparticles were synthesized by a simple, rapid, green photocatalysis method. The method introduced papain as a template to package silver and gold metal ions, and then the metal ions were reduced to atoms by photocatalysis of440nm LED light source. The produced metal atoms formed different proportions of gold and silver alloy nanoparticles in the synthesis process. The color of the alloy nanoparticles appears from yellow to red and their maximum absorption wavelength ranges from405nm and543nm with different proportion of the two metals. The gold and silver alloy nanoparticles synthesized by a new photocatalysis method would have potential applications in colorimetric analysis.In conclusion, we studied the using of light radiation to control the shape of STNPs, and synthesized uniform STNPs to improve the sensitivity of cysteine detection. Small biological molecules were used for study anisotropic assembly of the as-prepared STNPs and established a series of analytical methods based on the STNPs assembly. Furthermore, we synthesized silver and gold alloy nanoparticles by a simple, rapid, green photocatalysis method which would have potential applications in colorimetric analysis. Therefore, the thesis on the research of metal nanoparticle plasmon resonance coupling optical properties as well as establishing a nanometer spectral analysis method is of great importance.