Strong enhancement of migrational contribution to the transport by charged gel microlayers anchored on electrode surface

The influence of the presence of positively charged gel layers deposited on the electrode surface on reduction and oxidation of ionic substances in the absence of deliberately added supporting electrolyte was examined. The gel layers based on crosslinked copolymer of N-isopropylacrylamide (NIPA) and N-(3-aminopropyl)methacrylamide hydrochloride were used. The polymer net was positively charged in a wide pH range. Differently charged ferrocene derivatives, ferrocenyltrimethylammonium cation (FcN+), sodium salt of ferrocenylmethyl-3-mercapto-1-propanesulfonic acid (FcS−) and 1,1’-ferrocenedimethanol (Fc(MeOH)2), were used as the electroactive probes. It appeared that the depression of the oxidation current of cations was much stronger compared to bare electrodes; the depression factor equaled circa 2. The increase in oxidation current of anions was also strongly enhanced compared to bare electrodes; it amounted to 1.7 times. Addition of excess supporting electrolyte to the solution led to cancelling of major current changes. It meant that sufficiently concentrated supporting electrolyte eliminated not only regular migrational contribution but also strongly influenced the electrostatic-interactions between charged probes and charged polymer network.