Observation of coupling modes of surface plasmon resonance and local plasmon resonence and their applications to sensors

金胶体悬浮液呈红色是由于金纳米粒子中自由电子在520 nm波长处入射电场的共振振荡引起的，这种共振称为表面等离子体共振，有时称为局域等离子体共振。当金纳米粒子接近金属衬底时，由于衬底中诱导出的像偶极子，在粒子中除了偶极外，还会激发多极，如四极。这会导致共振波长向更长的波长移动。在研究中，我们研究了局域等离子体共振中的底物效应。在实验中，用载玻片作为金属衬底，在载玻片上沉积了25 nm的金膜。通过沉积在镀金玻璃衬底上的氨基乙硫醇(AET)自组装单分子膜将金纳米颗粒固定在衬底上。沉积的金纳米粒子的直径小于100 nm。从测量的吸收…获得的共振波长更多的金纳米粒子的离子光谱与其理论值进行了比较。通过比较发现，AET单分子膜的厚度为0.3-0.4 nm。还观察到了粒子-粒子系统中的耦合模式。为了观察到这一点，提出了一种使用逐层沉积方法来制备金纳米粒子多层膜的新技术。以聚乙烯亚胺和聚硫酸乙烯为阳离子聚合物，阴离子聚合物和金纳米粒子夹在这两种薄膜之间。用这种技术制备的金纳米粒子多层膜的厚度等于两个聚合物层的厚度之和。随着颗粒尺寸的增大，共振峰向长波方向移动。当该纳米粒子多层膜浸泡在乙醇-水混合物中时，共振波长随着水浓度的增加而向更短的波长移动。这是由于金颗粒之间的聚合物膜膨胀造成的。通过这些工作，证实了可以在亚纳米分辨率下测量颗粒与基质之间的间隙以及颗粒之间的间隙。较少

The red color of gold colloid suspension is caused by the resonant oscillation of the free electrons in the gold nanoparticles with the incident electric field at 〜520 nm wavelength, The resonance is called surface plasmon resonance or sometimes local plasmon resonance. When the gold nanoparticle approach to a metal substrate, multipoles, such as a quadruple, are excited in the particle besides a dipole, due to the image dipole induced in the substrate. This causes a shift of the resonance wavelength toward longer wavelength. In research this substrate effect in the local plasmon resonance was investigated. In experiments slide glass on which a 25-nm gold film was deposited was used for a metal substrate. Gold nanoparticles were immobilized onto the substrate by a self-assembled monolayer of aminoethanethiol (AET) deposited onto a gold coated glass substrate. The diameter of the gold nanoparticles deposited were less than 100 nm. Resonance wavelengths obtained from the measured absorpt … More ion spectra of the gold nanoparticles were compared with its theoretical values. From these comparison it was found that the thickness of the AET monolayer is 0.3-0.4 nm. The coupling modes in particle-particle systems were also observed. For this observation a new technique for fabricating gold nanoparticle multilayers using a layer-by-layer deposition method. Poly (ethyleneimine) and poly (vinylsulfate) were used as a cationic polymer and an anionic polymer and gold nanoparticles were sandwiched between these films. In the gold nanoparticle multilayers fabricated with this technique is equal to the thickness of the sum of both polymer layers. The resonance wavelength shifted toward longer wavelength were observed as the particle size increased. When this nanoparticle multilayers were immersed into ethanol-water mixtures, the resonance wavelength shifted toward shorter wavelength as the water concentration increased. This is caused by the swelling of the polymer films between the gold particles. Through these works, it was confirmed that the gap between particle and substrate of particle and particle can be measured with subnanometer resolution. Less