Staniszewska Teresa, Szkulmowski Maciej, Morawiec Seweryn
Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziadzka 5, 87-100 Torun, Poland.
J Phys Chem C Nanomater Interfaces. 2021 Jul 15;125(27):14765-14777. doi: 10.1021/acs.jpcc.1c02510. Epub 2021 Jul 1.
We present a comprehensive computational study on the optimization of the size of gold nanorods for single-molecule plasmonic sensing in terms of optical refractive index sensitivity. We construct an experimentally relevant model of single-molecule-single-nanoparticle sensor based on spherically capped gold nanorods, tip-specific functionalization and passivation layers, and biotin-streptavidin affinity system. We introduce a universal figure of merit for the sensitivity, termed contrast-to-noise ratio (CNR), which relates the change of measurable signal caused by the discrete molecule binding events to the inherent measurement noise. We investigate three distinct sensing modalities relying on direct spectral measurements, monitoring of scattering intensity at fixed wavelength and photothermal effect. By considering a shot-noise-limited performance of an experimental setup, we demonstrate the existence of an optimum nanorod size providing the highest sensitivity for each sensing technique. The optimization at constant illumination intensity (i.e., low-power applications) yields similar values of approximately 20 × 80 nm for each considered sensing technique. Second, we investigate the impact of geometrical and material parameters of the molecule and the functionalization layer on the sensitivity. Finally, we discuss the variable illumination intensity for each nanorod size with the steady-state temperature increase as its limiting factor (i.e., high-power applications).
我们针对单分子等离子体传感中基于光学折射率灵敏度的金纳米棒尺寸优化展开了全面的计算研究。我们构建了一个基于球形帽金纳米棒、尖端特异性功能化和钝化层以及生物素 - 链霉亲和素亲和系统的单分子 - 单纳米颗粒传感器的实验相关模型。我们引入了一个用于灵敏度的通用品质因数，称为对比度噪声比（CNR），它将由离散分子结合事件引起的可测量信号变化与固有测量噪声联系起来。我们研究了三种不同的传感模式，分别依赖于直接光谱测量、固定波长下散射强度的监测以及光热效应。通过考虑实验装置的散粒噪声限制性能，我们证明了存在一个最佳纳米棒尺寸，为每种传感技术提供最高灵敏度。在恒定光照强度下（即低功率应用）的优化对于每种考虑的传感技术产生了类似的约20×80 nm的值。其次，我们研究了分子和功能化层的几何和材料参数对灵敏度的影响。最后，我们讨论了以稳态温度升高为限制因素（即高功率应用）时每种纳米棒尺寸的可变光照强度。
