Investigation of Molecular Diffusion at Block Copolymer Thin Films Using Maximum Entropy Method-Based Fluorescence...

Area of Science:

• Physical Chemistry
• Materials Science
• Spectroscopy

Background:

• Fluorescence correlation spectroscopy (FCS) is a key technique for studying molecular diffusion.
• Analyzing complex diffusion behaviors often requires advanced analytical methods.
• Existing methods may struggle with systems exhibiting multiple, distinct diffusion coefficients.

Purpose of the Study:

• To evaluate the efficacy of the maximum entropy method (MEM) for FCS data analysis (MEM-FCS).
• To compare MEM-FCS with conventional methods and single molecule tracking (SMT) for diffusion analysis.
• To investigate molecular diffusion in nanostructured thin films using MEM-FCS.

Main Methods:

• Simulated FCS data with one and two diffusion modes were analyzed using MEM.
• MEM-FCS was applied to experimental FCS data from fluorescent probes in PS-b-PEO thin films.
• Results were validated against data obtained from single molecule tracking (SMT).

Main Results:

• MEM analysis accurately determined the number and magnitude of diffusion coefficients in simulated data.
• Conventional fitting models provided inaccurate diffusion coefficient estimates.
• MEM-FCS revealed distinct fast (surface) and slow (bulk) diffusion components in the thin films.
• SMT data corroborated the slow diffusion component identified by MEM-FCS.

Conclusions:

• MEM-FCS is a powerful tool for characterizing complex molecular diffusion without prior assumptions.
• MEM-FCS provides accurate quantification of multiple diffusion coefficients in heterogeneous systems.
• Combining MEM-FCS and SMT offers complementary insights into diffusion dynamics in materials.