- 學位論文
利用金屬表面電漿共振量測Au/CeO2奈米金顆粒大小
Determination of Gold Particle Sizes on CeO2 by Surface Plasma Resonance
摘要
本研究的目標在於利用低能量儀器，建立一套再現性高的測量奈米金顆粒大小與顆粒大小分布之技術，紫外光可見光光譜為本研究中最符合此一條件之測量手段。根據米氏散射理論中的金屬表面光電效應，光接近金顆粒表面會引發金屬表面自由電子共振，因此，利用共振吸收之能量可推斷金顆粒的大小。此外，環境折射率的修正為本研究的重要關鍵，以紫外光可見光光譜儀的數據為基礎，藉由環境折射率的修正數學式，建立一測量Au/CeO2觸媒之金顆粒大小的計算方式，並以Maxwell-Boltzmann分布方程式為數學模型，推估金顆粒大小的分布情形。 在本研究中發現，若要將模型假設於水溶液中的米氏散射理論，引進到Au/CeO2觸媒中，環境折射率應定為顆粒大小之函數，利用實驗數據來推算兩者之間的修正方程式，才能準確地描述載負在二氧化鈰上的金顆粒，對於不同入射光的吸收強度。另外，本研究中發現，Maxwell-Boltzmann分布方程式能夠準確地描述，奈米金顆粒載負在二氧化鈰表面上的分布狀況。當同時利用Maxwell-Boltzmann分布方程與環境折射率的修正式，能夠藉由完整的吸收曲線做為模擬的依據，進而推算出較TEM與HRTEM更為準確的顆粒大小分布狀況與平均顆粒大小。
並列摘要
The main objective of this research is to develop a new technique to determine the particle size and size distributions of nanogold supported on CeO2. UV-Vis spectroscopy, which is a low energy equipment, is easier and more economical than the traditional ways (such as by using TEM, HRTEM or XRD of high energy equipments) for the measurement. It is believed that the low energy would prevent the damage of the nano-sized samples during the measurement; in contrast, the high energy of HRTEM can easily cause the particle size growing. Mie scattering theory was applied in this research for predicting the gold particle sizes. It has been found that the position and the intensity of gold plasma band are function of particle sizes and the refractive indexes of gold and surrounding materials. In addition, the refractive index of surrounding material should change with the particle size of gold; therefore, a quantitative relation between refractive index and diameter of particle size has been obtained in this research. Moreover, the relation between the average gold particle size and the maximum absorption wavelength measured by UV-Vis Spectra has been established. Another way for predicting nanogold particle size has been established besides using the relation of maximum absorption wavelength in this research. By introducing Maxwell-Boltzmann distribution into the simulation, the particle size distribution can be obtained through fitting the simulation absorption curve with the experimental absorption spectra. This new method provides better results for predicting the average particle size.