Graduate School of Pharmaceutical Sciences, Nagoya City University.
Fuji Chemical Co., Ltd.
Chem Pharm Bull (Tokyo). 2022;70(2):130-137. doi: 10.1248/cpb.c21-00873.
The free electrons inside precious metals such as Au vibrate when the surface of the metal is irradiated with an electromagnetic wave of an appropriate frequency. This oscillation is referred to as surface plasmon resonance (SPR), and the resonance frequency varies with permittivity of the medium around the metal. SPR sensors are widely applied in the fields of bioscience and pharmaceutical sciences, including biosensing for drug discovery, biomarker screening, virus detection, and testing for food safety. Here, we fabricated a metal-insulator-metal (MIM) SPR sensor by constructing two-dimensional (2D) regular array of Au colloidal particles (2D colloidal crystals) on an insulator layer over a thin Au film coated on a glass substrate surface. The 2D crystals were fabricated by electrostatically adsorbing negatively charged three-dimensional crystals onto a positively charged thin insulator formed on Au film. The plasmon peaks/dips from the MIM structure were measured in aqueous solutions of ethylene glycol (EG) at various concentrations. Multiple plasmon peaks/dips were observed due to the localized SPR (LSPR) of the Au particles and the Fano resonance between the Au particles and thin film. The plasmon peaks/dips shifted to higher wavelengths on increasing EG concentrations due to an increase in the refractive index of the media. The observed peak/dip shift was approximately twice that of LSPR from an isolated Au particle. We expect the present MIM substrate will be useful as a highly sensitive sensor in the pharmaceutical field.
当金属表面被适当频率的电磁波照射时，贵金属（如 Au）内部的自由电子会发生振动。这种振动被称为表面等离激元共振（SPR），共振频率随金属周围介质的介电常数而变化。SPR 传感器广泛应用于生物科学和药物科学领域，包括药物发现的生物传感、生物标志物筛选、病毒检测和食品安全检测。在这里，我们通过在涂有薄金膜的玻璃基底表面上的绝缘体层上构建二维（2D）Au 胶体粒子（2D 胶体晶体）的规则阵列，制造了金属-绝缘体-金属（MIM）SPR 传感器。二维晶体是通过将带负电荷的三维晶体静电吸附到在 Au 膜上形成的带正电荷的薄绝缘体上而制造的。在不同浓度的乙二醇（EG）水溶液中测量了 MIM 结构的等离子体峰/陷。由于 Au 粒子的局域表面等离激元共振（LSPR）和 Au 粒子与薄膜之间的 Fano 共振，观察到多个等离子体峰/陷。由于介质折射率的增加，等离子体峰/陷向更高的波长移动。观察到的峰/陷位移约为孤立 Au 粒子的 LSPR 的两倍。我们预计，这种 MIM 衬底将在药物领域作为一种高灵敏度传感器很有用。
