Probing single polymeric nanoparticles via impact voltammetry

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Due to their diversity of applications in research and industry, nanomaterials have had a great technological importance in the last two decades. The global nanomaterials market is valued at $3.4 billion in 2014, and is expected to reach $11.8 billion by 2020, showing a compound annual growth rate of 23.1%. Furthermore, the global nanotechnology industry will grow to reach $75.8 Billion by 2020. Among them, polymer nanoparticles (NPs) attract a special interest due to their wide use in drug delivery, solar cells, biosensors and corrosion coatings. Although the electrochemistry of dissolved molecules and ions has been intensively studied, the electrochemistry of single nanoparticles remains largely unexplored. Reliable detection of NPs is a significant challenge due to their low concentration, large range of molecular structures of organic ones, agglomeration, heterogeneous character and presence in complex matrices. However, there is an urgent need from environmental and human health concerns for NPs characterization. Polymeric-NPs have typically been studied via the ensemble method. However, monitoring charge/discharge processes in such ensemble is complex since charge transfer and mass transport processes are overlapping and thus can only be estimated. In addition, this method can be misleading since particles agglomerate on the electrode so that only a fraction of them is active. Here, I will show how the recently developed nanoimpact method will be used to study the charging and doping of single polymer-NPs.Nanoimpacts is an efficient method which has been shown to be very promising for the study of kinetics and thermodynamics of NPs. This method enables precise and fast determination of size, concentration and composition of NPs. This project aims to characterize individual NPs of conducting polymers (e.g. PANI, PPy). Important information such as doping yield, dopant effect and reversibility of doping will be provided by these measurements, which are difficult to obtain by other spectroscopic methods. By linking the nanoimpact with independent sizing data, one can explore if the entire particle is doped or a sort of core-shell structure is made. Screening of different particle sizes allows us to identify the largest particle size which can be fully doped. We also aim at a better understanding of the electrochemical reactions at interface, as well as the study of kinetics and growth mechanism of these single NPs. Variation of the doping parameters and its influence on the behavior of the polymer shall be investigated. Comparison of the nanoimpact data with other techniques like DLS shall be carried out. This understanding is expected to have a significant impact on emerging applications.