{HECE/AA}n-Mb薄膜的电化学性质：测试底液pH的影响

{HECE/AA}n-Mb films were prepared by immersing {HECE/AA}n layer-by-layer films in myoglobin (Mb) solution to load Mb spontaneously, where HECE is strong polybase quaternized hydroxyethyl cellulose ethoxylate and AA is weak polyacid sodium alginate. The pH of testing solution where {HECE/AA}n-Mb films were tested by cyclic voltammetry (CV) influences the electrochemical activity of Mb in the films, showing that the fraction of electroactive Mb among the total Mb loaded into the films decreases remarkably as the pH of testing solution increases. CV and electrochemical impedance spectroscopy experiments with small electroactive probe demonstrates that the permeability of {HECE/AA}n-Mb films toward small counterions in solution decreases remarkably as the pH of testing solution increases. The transportation of counterions from external solution phase into film phase and/or from film phase to solution phase may become a limiting factor for Mb exchanging electrons with the underlying electrodes since the Mb molecules in the films take electron-hopping or electron self-exchange mechanism in electron transfer. The pH of testing solution would influence the porosity or permeability of the films, and the mobility of counterions with the film phase depends on the porosity or permeability of the films, so the pH of testing solution would greatly influence the electrochemical activity of Mb in the films.