Electropolymerization of Polydopamine at Electrode-Supported Insulating Mesoporous Films

Abstract

Bioinspired, stimuli-responsive, polymer-functionalized mesoporous films are promising platforms for precisely regulating nanopore transport toward applications in water management, iontronics, catalysis, sensing, drug delivery, or energy conversion. Nanopore technologies still require new, facile, and effective nanopore functionalization with multi- and stimuli-responsive polymers to reach these complicated application targets. In recent years, zwitterionic and multifunctional polydopamine (PDA) films deposited on planar surfaces by electropolymerization have helped surfaces respond to various external stimuli such as light, temperature, moisture, and pH. However, PDA has not been used to functionalize nanoporous films, where the PDA-coating could locally regulate the ionic nanopore transport. This study investigates the electropolymerization of homogeneous thin PDA films to functionalize nanopores of mesoporous silica films. We investigate the effect of different mesoporous film structures and the number of electropolymerization cycles on the presence of PDA at mesopores and mesoporous film surfaces. Our spectroscopic, microscopic, and electrochemical analysis reveals that the amount and location (pores and surface) of deposited PDA at mesoporous films is related to the combination of the number of electropolymerization cycles and the mesoporous film thickness and pore size. In view of the application of the proposed PDA-functionalized mesoporous films in areas requiring ion transport control, we studied the ion nanopore transport of the films by cyclic voltammetry. We realized that the amount of PDA in the nanopores helps to limit the overall ionic transport, while the pH-dependent transport mechanism of pristine silica films remains unchanged. It was found that (i) the pH-dependent deprotonation of PDA and silica walls and (ii) the insulation of the indium-tin oxide (ITO) surface by increasing the amount of PDA within the mesoporous silica film affect the ionic nanopore transport.

Simultaneous Electrochemical Detection of Dopamine and Tryptophan Using 3D Goethite–Spongin Composites

“…A prevalent challenge associated with electrochemical DA sensors is the formation of an insulating polydopamine film on the electrode surface during the application of positive potentials. It is crucial to note that the electropolymerization of DA on the electrode surface occurs under specific conditions, such as low scan rates (typically around 20 mV·s −1 ), extensive cycling (more than 15 cycles) and higher pH levels [ 63 , 64 ]. To ensure that DA electropolymerization exerts a negligible impact on sensor performance, CVs of 3DGS/CPE were recorded in a 0.1 M phosphate buffer at pH 6, containing 300 μM DA and TRP over 5 cycles ( Figure S2 ).…”

Recent Progress of the Application of Electropolymerization in Batteries and Supercapacitors: Specific Design of Functions in Electrodes

“…[69] Additionally, there are some methods with specific requirements, such as cryo-transmission electron microscopy [78] (Cryo-EM) and Time of flight secondary ion mass spectrometry (ToF-SIMS). [79,80] Some electropolymerization products, such as solid electrolyte interface (SEI) membranes, undergo significant morphological changes when subjected to high-voltage electron bombardment in conventional electron microscopy, making it difficult to observe the true morphology of organic thin films. The development of cryo-electron microscopy has effectively addressed this issue.…”

“…Varol et al in situ electropolymerized polydopamine (PDA) film on the surface of a porous substrate (Figure 2e) and used ToF-SIMS to monitor the variation trend of CN À content with the number of electropolymerization cycles (Figure 2f-h). [79] Gu et al used ToF-SIMS to characterize the composition and element distribution of the solid electrolyte interface formed by in situ electropolymerization on the graphite anode. [80] In this section, we have introduced the main components of electropolymerization, including monomers, solvents, substrates, and applied voltage and current.…”