結合奈米金粒子與共振波導光柵結構提升折射率變化感測度

The combination of gold nanoparticles and resonance waveguide grating structure for the enhancement of index refractive sensing sensivity

葉諭昇(Yu-Sheng Ye)

指導教授 ： 許佳振

國立中正大學/理學院/物理學系/碩士(2015年)

摘要

本論文藉由一維導模共振光柵結構，結合奈米金粒子增加感測器對於環境折射率變化的靈敏度，導模共振光柵結構的製作方式是利用奈米壓印法，壓印出一維的SU8光柵層，接著分別濺鍍上高折射率材料TiO2波導層以及SiO2緩衝層，最後在SiO2緩衝層表面修飾上奈米金粒子。實驗中利用光譜儀進行量測，藉著改變環境折射率去分析其共振模態的光強度以及波長位移變化量，實驗主要分成兩個部分，第一部分，由蔗糖溶液來改變整體環境折射率，並觀察共振模態的變化，第二部分將樣品浸泡至離子溶液中，在表面修飾單層且帶電荷的聚合物，平均一層聚合物的厚度為4奈米。分成兩部份的原因是為了分析出奈米金粒子在不同範圍的折射率變化下之貢獻，在實驗第二部分，我們發現在特定角度下觀察到直徑13奈米金粒子的侷域性表面電漿共振(localized surface plasmon resonance，LSPR)在光波長550奈米的吸收波段與導模共振效應(guiding mode resonance，GMR)的共振模態兩者對於環境折射率(n=1.33~1.40)改變下，其吸收波段與共振模態的位移趨勢是相反的，並且於入射角15度的條件下找到結合GMR與奈米金粒子之感測器具有較高的折射率感測度，結合奈米金粒子與GMR之感測器在光強度變化上分別比較純奈米金粒子修飾於玻璃基材與純GMR之感測器分別提升了1.9倍與2.7倍；在模態波長位移變化上與純GMR感測器比較則提升1.48倍。

關鍵字

共振波導光柵結構 ； 折射率感測器 ； 奈米金粒子

並列摘要

In this work, we demonstrate that the combination of the localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) and strong local electric field effect of guided-mode resonance (GMR) can be used for refractive index sensing sensitivity enhancement. The integrated device structure was designed by deposition of gold nanoparticle on the top of resonant waveguide grating (RWG). The sensitivity performance of LSPR and GMR was observed and analyzed by wavelength and intensity shifting. Concretely, sucrose and polyelectrolyte molecules (PAH/PSS) were chosen for changes in the local environmental refractive index. We obtained the sensing sensitivity enhancement of GMR in the range 0 to 25nm by decoration of AuNPs on RWG. Regard to the intensity sensitivity, the combination of LSPR and GMR produced the total considerable enhancement factor of 1.9 and 2.7 times compared to use of only LSPR and GMR, respectively. Turning to the wavelength shifting, 1.48 times enhancement can be yielded in comparison with GMR.

並列關鍵字

resonance waveguide grating structure ； refractive index sensor ； gold nanoparticles

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