Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, P. R. China.
Center for Photovoltaic Solar Energy, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, P. R. China.
Nanoscale. 2018 Aug 7;10(29):14182-14189. doi: 10.1039/c8nr03011a. Epub 2018 Jul 16.
A novel method of detecting single nanoparticles (NPs) in a microfluidic channel directly using a photonic nanojet (PNJ) was investigated. The theoretical model comprised a plane wave-illuminated, liquid-filled hollow-microcylinder (LFHM) and a single Au NP. Relevant studies were implemented and demonstrated with a finite element method (FEM)-based numerical simulation and explained physically through a ray-optics theoretical analysis with the assistance of energy flow line shifts. When depicting the optical-field distribution by gradually altered contour lines for LFHMs with or without a single Au NP, the outward distances of the specific points on the right end of each contour line, for a LFHM with a single Au NP relative to a LFHM without a NP, increased exponentially with decreasing contour levels. By dividing the contour levels into ten levels, the detectable NP of size of a few nanometers can be reflected through the outward distance of the contour points. The key parameters of the PNJ (the maximum light intensity, decay length and lateral beam waist), combined with the electric field distribution and focal point offset, can provide information on NP location. This work showed the PNJ itself to be a powerful and promising tool for the detection and identification of single NPs.
本研究提出了一种在微流道中直接利用光子纳米射流（PNJ）检测单个纳米颗粒（NPs）的新方法。理论模型由平面波照射的充液中空微圆柱（LFHM）和单个 Au NP 组成。通过基于有限元方法（FEM）的数值模拟进行了相关研究，并通过光线光学理论分析辅以能量流线移动进行了物理解释。通过逐渐改变具有或不具有单个 Au NP 的 LFHMs 的轮廓线来描绘光场分布时，对于具有单个 Au NP 的 LFHMs，每条轮廓线右侧特定点的外移距离相对于没有 NP 的 LFHMs 呈指数增长，随着轮廓线级别降低。通过将轮廓线分为十个级别，可以通过轮廓点的外移距离来反映出几个纳米大小的可检测 NP。PNJ 的关键参数（最大光强、衰减长度和横向束腰），结合电场分布和焦点偏移，可以提供 NP 位置的信息。这项工作表明，PNJ 本身是一种强大而有前途的工具，可用于检测和识别单个 NPs。
