Precise Control of Polydopamine Film Formation by Electropolymerization

Abstract

Summary Dopamine offers the possibility to build polymer films on any substrates via an oxidative process. This redox process cannot only be used for self‐oxidation in air, but also in an electrochemical deposition process using cyclic voltammetry. Electropolymerization provides the opportunity to customize film thicknesses on surfaces detectable by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The topography and nanomechanical properties of the films have been characterized in liquid via AFM. Electrochemical quartz crystal microbalance (EQCM) allows the determination of the deposited polymer quantities during the polymerization process and the ultra‐thin films have been detected by attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR).

Polydopamine deposition at fluid interfaces

“…The most common ways to control the film growth of PDA are changing the dopamine concentration using O 2 as the oxidant, changing the nature of the oxidant, modifying dopamine with electron‐withdrawing groups like nitro or chloro groups, performing the deposition in the presence of UV light and performing electrodeposition on conducting substrates in the absence of an exogeneous oxidant . The nature of the buffer used also plays an important role in the deposition kinetics of PDA films.…”

Ultrathin Polydopamine Films with Phospholipid Nanodiscs Containing a Glycophorin A Domain

“…Ultrathin PDA films were prepared on a gold substrate by cyclic voltammetry (CV) (Figure 1B) immersing the gold substrate in dopamine solution and sweeping the potential between −0.5 and +0.5 V for several cycles. [ 28,33 ] In Figure 1A, a simplified representation of one of the possible mechanisms of polydopamine formation and structure is depicted. The first step is the oxidation of catechol to quinone followed by cyclization and another oxidation step from leucodopaminechrome to dopaminechrome.…”

“…[ 20–27 ] Ultrathin and homogeneous PDA films attached to gold surfaces with thicknesses of 5–20 nm have been prepared by electropolymerization. [ 28 ] Electropolymerization is considerably faster than the often applied dip coating procedure, allowing precise control of the film thickness and homogeneity. [ 20,28–30 ] Although this mild polymerization technique is restricted to conductive materials, it provides the opportunity to embed non‐conductive materials, for example, biomolecules into the PDA film.…”

“…[ 28 ] Electropolymerization is considerably faster than the often applied dip coating procedure, allowing precise control of the film thickness and homogeneity. [ 20,28–30 ] Although this mild polymerization technique is restricted to conductive materials, it provides the opportunity to embed non‐conductive materials, for example, biomolecules into the PDA film. Until now, applying positive potentials for film removal after electropolymerization only resulted in delamination and destruction of the PDA films.…”

Tailored Assembly of Molecular Water Oxidation Catalysts on Photoelectrodes for Artificial Photosynthesis

“…The performance of WO 3 photoanodes can be remarkably improved only when co‐depositing PPy and RuPOM due to the desired energy level alignment for efficient charge transfer. In addition to well‐known conducting polymers, it was recently reported that synthetic melanin can be electropolymerized, and in situ incorporate CoPOM on various photoelectrodes such as Fe 2 O 3 , BiVO 4 , and TiO 2 with a significantly improved photoanode performance . This can be explained by the following reasons: (1) they provide improvement in electrocatalytic activity through the immobilization of molecular OER catalysts, (2) they allow for increased light‐harvesting due to an exceptionally high extinction coefficient of organic semiconductors rather than inorganic counterparts, (3) they demonstrate an efficient separation of charge carriers due to the formation of a p‐n heterojunction structure between a p‐type semiconducting polymer and an n‐type semiconductor, and (4) they show increased stability of an underlying photoanodes by deposition of polymeric overlayers.…”