Probing the Oxidative Doping of Single Polymer Nanoparticles
Authors: Amin Hatem M.A. , Attia Mina , Tschulik Kristina 
Published: July 2021

Due to their diversity of applications in research and industry, nanomaterials have gained a great technological importance in the last two decades. Among others, polymeric nanoparticles (NPs) attract a special interest in polymer batteries and solar cells.[1,2] Charge transfer is the main process underlying the charging/doping of polymer NPs.[2] This process involves uptake and release of ions from the polymer and has typically been studied using the ensemble method, that is by immobilizing a large number of these particles on an electrode and measuring the resulting charge/discharge response. Understanding the underlying process steps using ensemble studies is difficult, since charge transfer and mass transport processes are overlapping and thus can only be estimated. In addition, the ensemble method can be misleading since particles often agglomerate on the electrode so that only a fraction of their surface is accessible. Thus, probing the intrinsic response at the single particle level is necessary to understand, for instance, the charging process and ion intercalation capacity in rechargeable polymer batteries. This can be achieved, by single nanoparticle impact electrochemistry.[3-5]

Herein we demonstrate how quantifying the charging/doping of single particles of industrially important polymers can be achieved using this “nano impact” method. The polymeric NPs were successfully synthesized and characterized using UV-Vis, FTIR, DLS and SEM. For comparison, the doping behavior of ensembles of the NPs was investigated using cyclic voltammetry. Furthermore, the effect of dopant on the doping kinetics was studied. By linking the nano impact results with independent sizing data, it can be revealed whether the entire particle is doped, or a sort of core-shell structure is made. Importantly, the intrinsic kinetics of the doping of single NPs are investigated and the rate determining step in the doping process is determined. This work adds new insights into the charging of conducting polymers at the single particle scale which is expected to have a significant impact on emerging applications such as polymer batteries and supercapacitors.

Literature:

[1] Electrically Conducting Polymers: An Emerging Technology, Bakhshi, A. K.; Pooja Rattan. Current Science, 1997, 73, 648–651.

[2] Electrochemically Active Polymers for Rechargeable Batteries, Novák, P; Müller, K; Santhanam, K.S.V.; Haas, O. Chem. Rev. 1997, 97, 207-281

[3] Electrode-particle impacts: a users guide, Sokolov, S. V.; Eloul, S.; Kätelhön, E.; Batchelor-McAuley, C.; Compton, R. G. Physical chemistry chemical physics: PCCP 2016, 19, 28–43.

[4] Electrochemistry at single bimetallic nanoparticles - using nano impacts for sizing and compositional analysis of individual AgAu alloy nanoparticles, Saw, E. N.; Grasmik, V.; Rurainsky, C.; Epple, M.; Tschulik, K. Faraday discussions 2016, 193, 327–338.

[5] Doping of single polymeric nanoparticles, Zhou, X.-F.; Cheng, W.; Compton, R. G. Angewandte Chemie (International ed. in English) 2014, 53, 12587–12589.