title: Probing Non-Gaussianity in Confined Diffusion of Nanoparticles.
abstract: Confined diffusion is ubiquitous in nature. Ever since the "anomalous yet Brownian" motion was observed, the non-Gaussianity in confined diffusion has been unveiled as an important issue. In this Letter, we experimentally investigate the characteristics and source of non-Gaussian behavior in confined diffusion of nanoparticles suspended in polymer solutions. A time-varied and size-dependent non-Gaussianity is reported based on the non-Gaussian parameter and displacement probability distribution, especially when the nanoparticle's size is smaller than the typical polymer mesh size. This non-Gaussianity does not vanish even at the long-time Brownian stage. By inspecting the displacement autocorrelation, we observe that the nanoparticle-structure interaction, indicated by the anticorrelation, is limited in the short-time stage and makes little contribution to the non-Gaussianity in the long-time stage. The main source of the non-Gaussianity can therefore be attributed to hopping diffusion that results in an exponential probability distribution with the large displacements, which may also explain certain processes dominated by rare events in the biological environment.
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Chundong
authors.initials: C
authors.lastname: Xue
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
authors.forename: Kaikai
authors.initials: K
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Tian
authors.affiliation: State Key Laboratory of Nonlinear Mechanics, Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Guoqing
authors.initials: G
authors.lastname: Hu
mesh_terms: D015335:Molecular Probes; D053758:Nanoparticles
chemical_list: D015335:Molecular Probes