Observing Brownian motion of nanoscale objects through a traditional optical microscope is still a challenge. Here, we present a method to overcome this challenge by using a traditional optical microscope assisted with a removable microsphere-embedded thin film. The diffusion coefficient of individual unconstrained polystyrene (PS) nanoparticles with a diameter of 300 nm in water is calculated from their respective mean-square displacement versus time curves, and the measured diffusion coefficient shows good agreement with the theoretical Stokes–Einstein one, proving the feasibility of our method. In addition, the experimental results show that the movement of the PS nanoparticles is slowed down near a plane wall, and the diffusion coefficient is consistent with the theoretical constrained diffusion coefficient, which shows that our method can also study the constrained Brownian motion of nanoparticles constrained near a plane wall. Our research results are helpful for the application of microsphere-assisted microscopy in new fields and also provide a new method for nanoparticle tracking.
© 2021 Optical Society of AmericaFull Article | PDF Article
More Like This
Yurong Cao, Xiaoqing Wang, Songlin Yang, Yong Pei, Jiaojiao Zang, Jianguo Wang, and Yong-Hong Ye
Appl. Opt. 61(8) E8-E13 (2022)
Hao Luo, Haibo Yu, Yangdong Wen, Tianyao Zhang, Pan Li, Feifei Wang, and Lianqing Liu
Opt. Lett. 45(11) 2981-2984 (2020)
Opt. Lett. 42(4) 735-738 (2017)