Ultrathin polypyrrole films on self‐assembled monolayers as an efficient ultramicroelectrode assay

Abstract

In this work, we investigated the effect of electrodeposition of polypyrrole (PPy) films on two different self‐assembled monolayers (SAMs) modified gold electrode for the electrochemical construction of ultramicroelectrode (UME). In order to obtain SAM modified surfaces, 4‐mercapto‐1‐butanol and 11‐mercaptoundecanoic acid were used. The effect of these two chains on pyrrole electropolymerization was compared. Electropolymerization of pyrrole on SAM modified Au electrode was carried out by using cyclic voltammetry (CV) and constant potential electrolysis. To investigate the UME formation, the obtained surfaces were tested in Fe(CN)63−/4− redox system. UMEs were characterized using scanning electron microscopy energy‐dispersive X‐ray spectroscopy, attenuated total reflectance fourier transform infrared spectroscopy and electrochemical impedance spectroscopy. The designed UME was applied as an immobilization matrix to entrap a redox protein, Hemoglobin (Hb), as a model. Direct electron transfer between this protein and the fabricated thiol modified PPy based UME was achieved, which is very challenging on bare electrode surfaces. With this study, a simple, low‐cost and reproducible UME production way has been successfully accomplished and Hb modified UME is promising for different bioanalytical applications, for instance; cellular hydrogen peroxide or nitrite sensing.

The development of an electropolymerized, molecularly imprinted polymer (MIP) sensor for insulin determination using single-drop analysis

“…On the contrary, pure Ppy can be deposited on the surface of an SPCE as a completely covered homogeneous and adherent film. 71 This observation supports the assumption that the insulin molecules were entrapped in the Ppy backbone, which was reflected in the reduced current response of the [Fe(CN) 6 ] 3−/4− redox probe. Finally, the overoxidation of Ppy, used as a strategy to remove insulin, affected the conductivity of the composite MIP on the surface of the SPCE, as evidenced by the overall decrease in current.…”

“…This cauliflower-like structure consists of microspherical grains formed on the defect sites of the SPCE surface after nucleation. 47,71 However, the Ppy film grown in the presence of insulin shows a more granular morphology with no observed clusters. This could support the idea that insulin entrapped in the polymer leads to the swelling of the Ppy film, which is associated with a lower conductivity than in pure Ppy film.…”

“…The properties of conducting polymers depend strongly on their morphology and structure. 71 The insulin molecule can be seen as a protrusion in the monolayer. The area around the molecule can immediately be filled with the growing polymer, leading to the formation of an uneven coating.…”

“…Compared to a bare SPCE, all Ppy-coated SPCEs ( pure Ppy-SPCE, Ppyinsulin-SPCE, and MIP-SPCE) showed enhanced electrochemical activity due to the favourable electrochemical properties of the electropolymerized Ppy film. 47,71 The higher current of the [Fe(CN) 6 ] 3−/4− redox probe measured on Ppy-SPCE, Ppy-insulin-SPCE, and MIP-SPCE compared to bare SPCE can arise due to the increase in double layer capacitance (Fig. 5).…”