奈米矽片銀/界面活性劑複合物於表面增強拉曼散射偵測之應用

Abstract

本研究以具可撓性之奈米矽片 (NSP) 當作基材，使奈米銀粒子 (AgNP) 穩定地在其表面上被還原，製備成新穎之奈米矽片銀 (AgNP/NSP) 複合材料。其具有浮動性及三維熱點效應，可改善奈米粒子之穩定性、傳統陽極氧化鋁銀 (Ag/AAO) 陣列玻璃基板之空間限制和增加與微生物之接觸面積，並將其應用於表面增強拉曼散射 (SERS) 檢測技術。NSP是由層狀天然蒙脫土 (MMT) 脫層而得，其面積為100 × 100 nm2，厚度約1-5 nm。由於AgNP可吸附在幾奈米厚之NSP的上下側，相較於原始多層之AgNP/MMT (厚度約10-20 nm)，此AgNP/NSP之幾何空間排列可誘發強烈的熱點效應 (z-方向)，因此可廣泛地用於偵測小分子腺嘌呤 (adenine) 至微生物金黃色葡萄球菌 (S. aureus) 之SERS訊號。另外，此AgNP/NSP SERS基板具自由浮動的移動性和光學穿透性，可增加對於微生物的接觸面積及增強SERS偵測之靈敏度。 更進一步，將AgNP/NSP利用非離子型界面活性劑進行表面修飾，合成奈米銀-奈米矽片-界面活性劑 (AgNP/NSS) 複合物。先製備奈米矽片-界面活性劑 (NSS) 複合物後，在水溶液中原位 ( in-situ) 還原硝酸銀成奈米銀粒子。此界面活性劑可增強SERS基板與待測物之表面親和力，用於選擇性偵測疏水性細菌如大腸桿菌 (E. coli) 及分枝桿菌 (mycobacteria)、不規則形狀之微生物 (Fungi) 和較大型生物細胞。藉由調控界面活性劑組成比例，發現SERS偵測強度明顯提升且有一最佳化強度。 綜合疏水性、浮動基板的靈活性和三維熱點效應等特性，AgNP/NSS複合物量身定制地應用於選擇性偵測不規則形狀及疏水性微生物和較大型生物細胞，提供了一種新穎且快速無標籤的方式於特定的生物檢測。

Novel nanohybrids of silver nanoparticle (AgNP) on nano silicate platelet (NSP) with floating and three-dimensional (3D) hot-junctions (particularly in z-direction) properties were discovered for improving the stability of free nanoparticles and the mobility of conventional Ag depositing porous anodic aluminum oxide (Ag/AAO) rigid glass-based substrate in surface-enhanced Raman scattering (SERS) detection technology. The NSP in the dimension of 100 x 100 nm2 with 1-5 nm thickness was previously synthesized from the exfoliation of natural clays such as montmorillonite (MMT). Since the AgNPs are adsorbed on both sides of few nanometer-thick NSP, the geometric arrangement of AgNP/NSP may induce strong hot-junctions (z-direction) in reference to the pristine multi-layers Ag/MMT at the thickness of ~20 nm, which can be widely used in SERS detection of small molecules (adenine from DNA) and microorganism (S. aureus). Further, AgNP/NSP SERS substrate displays free floating mobility and optical transparency (less background interference), which inherently increase the contacted surface-area between the substrate and microorganisms, thus the enhancement of SERS sensitivity. On the other hand, the surface modulation of AgNP/NSP with a nonionic surfactant could be applied toward a variety of microorganisms including hydrophobic microbes, irregular-shaped microorganisms and larger biological cells due to their mutual specific surface interactions. The tri-component nanohybrids, Ag-NSP-surfactant (AgNP/NSS) were synthesized by in-situ reduction of AgNO3 into AgNP in the presence of NSP-surfactant hybrids (NSS) in aqueous. Owing to the presence of surfactant, the surface tension of AgNP/NSS had been adjusted and the affinity between AgNP/NSS and microorganisms had significantly increased for selectively detecting hydrophobic bacteria such as E. coli and mycobacteria, irregular-shaped microorganisms such as fungi and larger cells. With the surfactant fraction of AgNP/NSS increased, the SERS intensity of hydrophobic bacteria had dramatically enhanced comparing to the pristine AgNP/NSP and had an optimal value. Combination of hydrophobicity, substrate floating flexibility and 3D hot-junctions, the AgNP/NSS nanohybrids were tailored for selectively detecting irregular-shaped, hydrophobic microorganisms and larger biological cells, which provided a novel rapid label-free way for specific bio-detection.