The pH-sensitive switchable behavior based on the layer-by-layer films of hemoglobin and Ag nanoparticles

Abstract

A switchable layer-by-layer assembly film was constructed by alternate adsorption of negatively charged Ag nanoparticles (AgNPs) and positively charged hemoglobin (Hb) with appropriate pH value. The {Hb/AgNPs} n films showed strong pH-sensitive on–off responses toward the electroactive probe Fe(CN) 6 3 − . The {Hb/AgNPs} 4 film is active (“on”) to the negatively charged probe, Fe(CN) 6 3 − , at pH 3.0, but inactive (“off”) to the probe at pH 9.0. The switching behavior is fully reversible by simply changing the pH value of the solution and can be applied for pH-controlled reversible electrochemical reduction of H 2O 2 catalyzed by Hb. The pH-sensitive behavior may be due to the electrostatic interaction between the films and the probe. The modified electrode with the pH-controlled switchable redox activity would possibly become a “smart” interface for the construction of specific electrochemical biosensors with a signal-controlled activity.