Glassy carbon electrode modified with gold nanoparticles and hemoglobin in a chitosan matrix for improved pH-switchable sensing of hydrogen peroxide

Abstract

Hemoglobin (Hb) has been demonstrated to endow electrochemical sensors with pH-switchable response because of the presence of carboxyl and amino groups. Hb was deposited in a chitosan matrix on a glassy carbon electrode (GCE) that was previously coated with clustered gold nanoparticles (Au-NPs) by electrodeposition. The switching behavior is active ("on") to the negatively charged probe [Fe(CN) 63− ] at pH 4.0, but inactive ("off") to the probe at pH 8.0. This switch is fully reversible by simply changing the pH value of the solution and can be applied for pH-controlled reversible electrochemical reduction of H 2 O 2 catalyzed by Hb. The modified electrode was tested for its response to the different electroactive probes. The response to these species strongly depends on pH which was cycled between 4 and 8. The effect is also attributed to the presence of pH dependent charges on the surface of the electrode which resulted in either electrostatic attraction or repulsion of the electroactive probes. The presence of Hb, in turn, enhances the pH-controllable response, and the electrodeposited Au-NPs improve the capability of switching. This study reveals the potential of protein based pH-switchable materials and also provides a simple and effective strategy for fabrication of switchable chemical sensors as exemplified in a pH-controllable electrode for hydrogen peroxide.

pH-Switchable Electrochemical Interfaces-a Brief Review

“…Recently, Gu and co-workers reported that Hb, as an important redox respiratory protein in red cells, was coupled with metal NPs such as AuNPs [43] and AgNPs [44] to modify electrodes with remarkable response to different pH solution. For instance, the pH sensitive LBL films were fabricated by alternately adsorbing Hb and conductive AgNPs on the surface of chitosan modified GC electrode.…”