Laboratory of Microsystems, École Polytechnique Fédérale de Lausanne , 1015 Lausanne, Switzerland.
Nano Lett. 2015 Mar 11;15(3):1730-5. doi: 10.1021/nl5044067. Epub 2015 Feb 18.
We detect by optical microscopy Au and fluorescent nanoparticles (NPs) during their motion in water-based medium, using an array of dielectric microspheres that are patterned in a microwell array template. The microspheres act as lenses focusing the light originating from a microscope objective into so-called photonic nanojets that expose the medium within a microfluidic channel. When a NP is randomly transported through a nanojet, its backscattered light (for a bare Au NP) or its fluorescent emission is instantaneously detected by video microscopy. Au NPs down to 50 nm in size, as well as fluorescent NPs down to 20 nm in size, are observed by using a low magnification/low numerical aperture microscope objective in bright-field or fluorescence mode, respectively. Compared to the NPs present outside of the photonic nanojets, the light scattering or fluorescence intensity of the NPs in the nanojets is typically enhanced by up to a factor of ∼40. The experimental intensity is found to be proportional to the area occupied by the NP in the nanojet. The technique is also used for immunodetection of biomolecules immobilized on Au NPs in buffer and, in future, it may develop into a versatile tool to detect nanometric objects of environmental or biological importance, such as NPs, viruses, or other biological agents.
我们通过光学显微镜在水基介质中检测 Au 和荧光纳米粒子（NPs）的运动，使用的是排列在微井阵列模板中的介电微球。微球充当透镜，将来自显微镜物镜的光聚焦成所谓的光子纳米射流，从而暴露微流道内的介质。当 NP 随机穿过纳米射流时，其背散射光（对于裸 Au NP）或荧光发射会被视频显微镜即时检测到。使用低放大率/低数值孔径显微镜物镜在明场或荧光模式下，可以分别观察到 50nm 以下的 Au NPs 和 20nm 以下的荧光 NPs。与光子纳米射流外部的 NPs 相比，纳米射流中的 NPs 的光散射或荧光强度通常增强了高达约 40 倍。实验强度被发现与 NP 在纳米射流中占据的面积成正比。该技术还可用于缓冲液中固定化在 Au NPs 上的生物分子的免疫检测，并且将来可能会发展成为一种用于检测环境或生物重要性的纳米级物体的通用工具，例如 NPs、病毒或其他生物制剂。
