摘要
Optical modeling coupled to experiments show that a microscope operating in reflection mode allows imaging,through solutions or even a microfluidic cover,various kinds of nanoparticles,NPs,over a(reflecting)sensing surface,here a gold(Au)surface.Optical modeling suggests that this configuration enables the interferometric imaging of single NPs which can be characterized individually from local change in the surface reflectivity.The interferometric detection improves the optical limit of detection compared to classical configurations exploiting only the light scattered by the NPs.The method is then tested experimentally,to monitor in situ and in real time,the collision of single Brownian NPs,or optical nanoimpacts,with an Au-sensing surface.First,mimicking a microfluidic biosensor platform,the capture of 300 nm FeOx maghemite NPs from a convective flow by a surface-functionalized Au surface is dynamically monitored.Then,the adsorption or bouncing of individual dielectric(100 nm polystyrene)or metallic(40 and 60 nm silver)NPs is observed directly through the solution.The influence of the electrolyte on the ability of NPs to repetitively bounce or irreversibly adsorb onto the Au surface is evidenced.Exploiting such visualization mode of single-NP optical nanoimpacts is insightful for comprehending single-NP electrochemical studies relying on NP collision on an electrode(electrochemical nanoimpacts).
基金
We are grateful for financial support by the Agence Nationale pour la Recherche(NEOCASTIP ANR-15-CE09-0015-02 project)
Direction Générale de l’Armement(AMMIB ANR-13-ASTR-0021-01),by Universities Paris Diderot and Paris Sud and by CNRS.
