National Institute of Physics, University of the Philippines Diliman, Quezon City 1101, Philippines.
Innovative Photon Manipulation Research Team, RIKEN Center for Advanced Photonics, Wako 351-0198, Japan.
Sensors (Basel). 2021 Jul 5;21(13):4593. doi: 10.3390/s21134593.
We demonstrate potential molecular monolayer detection using measurements of surface plasmon resonance (SPR) and angular Goos-Hänchen (GH) shift. Here, the molecular monolayer of interest is a benzenethiol self-assembled monolayer (BT-SAM) adsorbed on a gold (Au) substrate. Excitation of surface plasmons enhanced the GH shift which was dominated by angular GH shift because we focused the incident beam to a small beam waist making spatial GH shift negligible. For measurements in ambient, the presence of BT-SAM on a Au substrate induces hydrophobicity which decreases the likelihood of contamination on the surface allowing for molecular monolayer sensing. This is in contrast to the hydrophilic nature of a clean Au surface that is highly susceptible to contamination. Since our measurements were made in ambient, larger SPR angle than the expected value was measured due to the contamination in the Au substrate. In contrast, the SPR angle was smaller when BT-SAM coated the Au substrate due to the minimization of contaminants brought about by Au surface modification. Detection of the molecular monolayer acounts for the small change in the SPR angle from the expected value.
我们通过测量表面等离子体共振 (SPR) 和角度古斯-汉欣 (GH) 位移来演示潜在的分子单层检测。这里，感兴趣的分子单层是吸附在金 (Au) 基底上的苯硫醇自组装单层 (BT-SAM)。表面等离子体激元的激发增强了 GH 位移，这主要是由角度 GH 位移主导的，因为我们将入射光束聚焦到一个小的光束腰上，使得空间 GH 位移可以忽略不计。在环境测量中，BT-SAM 在 Au 基底上的存在诱导了疏水性，这降低了表面污染的可能性，从而实现了分子单层传感。这与清洁 Au 表面的亲水性形成对比，清洁 Au 表面极易受到污染。由于我们的测量是在环境中进行的，由于 Au 基底中的污染，测量到的 SPR 角度比预期的要大。相比之下，当 BT-SAM 覆盖 Au 基底时，SPR 角度较小，这是由于 Au 表面修饰带来的污染物最小化。分子单层的检测解释了 SPR 角度相对于预期值的微小变化。
