Anisotropic silica coating on gold nanorods boosts their potential as SERS sensors
Anisotropic silica coating on gold nanorods boosts their potential as SERS sensors
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DOI：
10.1039/d1nr07918b
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发表时间：
2022-03-22
期刊：
影响因子：
6.7
通讯作者：
Murphy, Catherine J.
中科院分区：
文献类型：
--
作者：
Meyer, Sean M.;Murphy, Catherine J.
金纳米棒是众所周知的表面增强拉曼散射基底。在纵向等离子体激元激发下，纳米棒的末端与棒的侧面相比经历更大的局部电场，这表明如果分子可以优先结合到纳米棒的末端，则拉曼活性分子将被最好地检测到。用阴离子介孔二氧化硅帽涂覆金纳米棒的尖端使得能够在比整个棒的相应二氧化硅涂层所观察到的浓度更低的浓度下对阳离子染料亚甲基蓝进行表面增强拉曼散射（Sers）检测。通过分析亚甲基蓝两个拉曼活性模式的强度比和金纳米棒复合物的表面等离子体共振峰位移，可以推断在低浓度的亚甲基蓝下，分子吸附到尖端涂覆的二氧化硅金纳米棒的尖端。用阳离子基团官能化的阴离子二氧化硅封端消除了阳离子亚甲基蓝的Sers增强，证明了在这种情况下吸附过程的静电性质。这些结果表明，各向异性二氧化硅涂层可以将分析物集中在金纳米棒的尖端，以改善化学传感和诊断。
Gold nanorods are well-known surface-enhanced Raman scattering substrates. Under longitudinal plasmonic excitation, the ends of the nanorods experience larger local electric fields compared to the sides of the rods, suggesting that Raman-active molecules would be best detected if the molecules could preferentially bind to the ends of the nanorods. Coating the tips of gold nanorods with anionic mesoporous silica caps enabled surface-enhanced Raman scattering (SERS) detection of the cationic dye methylene blue at lower concentrations than observed for the corresponding silica coating of the entire rod. By analyzing the intensity ratio of two Raman active modes of methylene blue and the surface plasmon resonance peak shift of the gold nanorod composites, it can be inferred that at a low concentration of methylene blue, molecules adsorb to the tips of the tip coated silica gold nanorods. Functionalization of the anionic silica endcaps with cationic groups eliminates the SERS enhancement for the cationic methylene blue, demonstrating the electrostatic nature of the adsorption process in this case. These results show that anisotropic silica coatings can concentrate analytes at the tips of gold nanorods for improvements in chemical sensing and diagnostics.