Super-resolution fluorescence imaging of PEDOT:PSS films.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a popular conduction polymer and widely used in organic electronics, bioelectronics and printed electronics. It is believed that PEDOT:PSS has a core-shell colloidal structure dispersed in the formulation. However, the size and surface functional groups of the PEDOT:PSS dispersion and films remain to be visualized. Here, we have introduced the concept of aggregation-induced emission (AIE) to super-resolution imaging for designing the cationic probe TPE-4N+ and accomplished the nanoscale optical visualization of PEDOT:PSS films through reversible electrostatic interactions. Information on the PEDOT:PSS size and surface charge has been successfully collected via super-resolution imaging. The full-width at half-maximum (FWHM) of PSS nanoparticles was observed to be approximately 30-40 nm. The super-resolution fluorescence imaging method can also be used to monitor the PEDOT:PSS film after acid treatment. It was observed that PSS chains were washed away when exposed to concentrated sulfuric acid, which explains why concentrated sulfuric acid treatment greatly improves the conductivity of the PEDOT:PSS film. Super-resolution imaging is promising as an effective method for characterizing PEDOT:PSS films.