Yamada Hirotaka, Kawasaki Daiki, Sueyoshi Kenji, Hisamoto Hideaki, Endo Tatsuro
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan.
Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 5-3 Yonban-cho, Chiyoda, Tokyo 102-8666, Japan.
Micromachines (Basel). 2022 Feb 3;13(2):257. doi: 10.3390/mi13020257.
In this paper, metal-insulator-metal (MIM) nanostructures, which were designed to exhibit two absorption peaks within 500-1100 nm wavelength range, were fabricated using magnesium difluoride (MgF) as the insulator layer. Since the MIM nanostructures have two plasmon modes corresponding to the absorption peaks, they independently responded to the changes in two phases: the surrounding medium and the inside insulator layer, the structure is expected to obtain multiple information from sample solution: refractive index (RI) and molecular interaction between solution components and the insulator layer. The fabricated MIM nanostructure had a diameter of 139.6 ± 2.8 nm and a slope of 70°, and exhibited absorption peaks derived from individual plasmon modes at the 719 and 907 nm wavelengths. The evaluation of the response to surrounding solution component of the MIM nanostructures revealed a linear response of one plasmon mode toward the RI of the surrounding medium and a large blue shift of the other plasmon mode under conditions where glycerol was present at high concentration. From optical simulation and the evaluation of the MgF fabricated by deposition, the blue shift was expected to be due to the swelling of MgF interacting with the hydroxyl groups abundantly included in the glycerol molecules. The results indicated the individual responses of two plasmon modes in MIM nanostructures toward medium components, and brought the prospect for the simultaneous measurement of multiple elements using two or more plasmon modes.
在本文中，以二氟化镁（MgF₂）作为绝缘层，制备了旨在在500 - 1100 nm波长范围内呈现两个吸收峰的金属 - 绝缘体 - 金属（MIM）纳米结构。由于MIM纳米结构具有与吸收峰相对应的两种等离子体模式，它们分别对两个相的变化做出响应：周围介质和内部绝缘层，预计该结构能够从样品溶液中获取多种信息：折射率（RI）以及溶液成分与绝缘层之间的分子相互作用。制备的MIM纳米结构直径为139.6 ± 2.8 nm，斜率为70°，并在719和907 nm波长处呈现出源自各个等离子体模式的吸收峰。对MIM纳米结构对周围溶液成分的响应评估表明，一种等离子体模式对周围介质的折射率呈线性响应，而在甘油高浓度存在的条件下，另一种等离子体模式发生了较大的蓝移。通过光学模拟和对沉积制备的MgF₂的评估，预计蓝移是由于MgF₂与甘油分子中大量包含的羟基相互作用而膨胀所致。结果表明了MIM纳米结构中两种等离子体模式对介质成分的各自响应，并为使用两种或更多种等离子体模式同时测量多种元素带来了前景。
