本研究探討含羅丹明發色團之染料分子YP39，在不同距離下與銀包金核殼金屬奈米粒子之間的交互作用以及其螢光增強效應。本實驗使用螢光生命期影像顯微術，可以準確的測量單顆銀包金奈米粒子表面鍵結的染料分子的螢光生命期。而對於染料分子與金奈米粒子間的介質，我們利用導體的銀殼層當作間隙物，以晶種成長法的方法包覆直徑40 nm的金奈米粒子，控制不同的合成循環次數，分別合成出4 nm、6 nm、7.5 nm、13 nm及16 nm五種厚度不同的銀殼層。隨著銀殼層厚度的增加，從靜態螢光光譜得到校正後的螢光強度和未接上銀包金奈米粒子之YP39比例分別為0.06、0.05、0.26、1.25及0.46，且隨著距離有先增後減的現象除了在厚度13 nm的樣品其倍率大於1外，其他厚度下因被銀殼層嚴重淬息的影響，螢光增強倍率均小於1。我們以所得到的兩個生命期推導出染料分子與銀包金奈米粒子交互作用之動力學模型，實驗測得短的及長的生命期分別為15、23、26、21、25 ps及210、240、251、246、255 ps。我們推導出一簡易的動力學模型，並計算出各能量轉移間的速率。我們認為當染料被激發時，激發態的染料可以放光的方式回至基態，或者染料也可能會將能量傳給金奈米粒子的明亮模式，而獲得能量的金奈米粒子可能會將能量回傳給染料，或是以光子的方式將光放至遠場，另外，激發態染料也可能透過奈米表面能量轉移(nanosurface energy transfer, NSET)的方式將能量傳至銀殼層，此能量轉移會使染料的螢光被嚴重的淬息。

In this work, we studied the metal enhanced-fluorescence of rhodamine B dye by Au@Ag core-shell nanoparticle. We measured emission of the dye molecule bonded on the Au@Ag nanoparticle using fluorescence lifetime imaging microscopy (FLIM). We used seed-growth method to synthesized different Ag shell thicknesses of 40 nm gold nanoparticles, and controlled different cycles of seed growth to obtain five shell thickness as spacer: 4 nm, 6 nm, 7.5nm, 13 nm, and 16 nm. The enhancement factors for fluorescence are 0.06, 0.05, 0.26, 1.25 and 0.46 for Ag shell thickness 4 nm to 16 nm respectively, which display a maximum at spacer separation 13 nm. Due to the fluorescence quenching by Ag shell, the enhancement factor of all the samples are smaller than 1, except 13 nm nanoparticles. We used the first and the second lifetime to derive the kinetic model of the interaction between dye molecule and Au@Ag nanoparticle. The first time constant τ1 and second time constant τ2 for Ag shell thickness from 4 nm to 16 nm are 15, 23, 26, 21, 25 ps and 210, 240, 251, 246, 255 ps, respectively. We derived a simple kinetic model, and calculated all rates of energy transfer between dye molecules and Au@Ag nanoparticle. As the dye molecule is excited, it can relax to ground state. The excited dye molecule either can transfer energy to bright mode of Au nanoparticle. The Au nanoparticle can transfer energy back to the dye molecule, or it can also dissipate energy radiatively. In addition, the excited dye molecule can transfer energy to Ag shell via nanosurface energy transfer (NSET), leading to dramatic fluorescence quenching.

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