Investigation of transient transport processes using single gold nanopores as modelsystems

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In the project single polymer track-etched nanochannels with tailored geometry, diameter, length, and surface charge will be fabricated and applied as model systems to systematically study how transient transport processes are influenced by each of these parameters. Asymmetric charged polymer nanochannels exhibit several remarkable properties, such as e.g., ion current rectification, ion selectivity, and ion current gating via external triggers such as pH value, temperature, light, or ion concentration. Among these, applying an external voltage to a well-defined conductive “gate” enables the local modification of the critical lengths (Debye layer thickness and Dukhin length), and constitutes the most suitable and promising solution for technological applications. In this project, polymer single nanochannels will be modified with conductive gold layers and porous gold to enable "voltage charging" of the gold surface. This will allow us to investigate how ion and mass transport are influenced by the external modulation of the Debye layer thickness and Dukhin length. In particular, the planned experiments will enable us to apply time-dependent voltage signals using different nanochannel configurations (e.g., Au-coated nanochannels and porous Au inside the nanochannel), varying the experimental parameters systematically (channel geometry and size, electrolyte composition and concentration, amplitude, and frequency of the voltage signal). The choice of the electrolyte will be based on the presence of ions with different charges and/or diffusivities. These experiments are particularly relevant for the realization of the theoretically predicted transient nanopores and future applications in more efficient membrane separation processes. Thus, in phase 1, the project will focus on studying and understanding the time-dependent transport properties using single Au-based nanochannels. In phase 2, this know-how will be applied to multi-channel membranes and specific separation processes.