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

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)63 −. The {Hb/AgNPs}4 film is active (“on”) to the negatively charged probe, Fe(CN)63 −, 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 H2O2 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.

► The LBL films of AgNPs and Hb showed strong pH-sensitive on-off responses.
► The switching behavior is reversible and reproducible by changing the solution pH.
► The film could be used for pH-controlled electrochemical determination of H2O2.
► It provides another approach to prepare tunable electrochemical biosensors.