Transfer of mixed protein–fatty acid LB films onto Si/SiO2 substrates. Influence of the surface free energy

In order to use mixed enzyme–fatty acid Langmuir–Blodgett (LB) films for the preparation of glucose biosensors based on silicon transducers, the transfer of such mixed LB layers on Si/SiO2 substrates is studied in this paper. The kinetics of the adsorption of the glucose oxidase (GOx) at the air–water interface is studied as a function of the behenic acid surface concentration. The pressure–area isotherms of pure behenic acid film and of mixed enzyme–behenic acid film at the air–water interface are compared, showing an insertion of the enzyme in the behenic acid film and a smooth phase transition for this mixed film. fluence of the surface free energy of the Si/SiO2 substrate is studied in detail. Three surface states are compared: untreated thermal silica, hydroxylated silica and silanized silica. The higher transfer coefficients of the mixed LB film are obtained with silanized silica which presents the lower values of the electron donor component of the surface free energy. The transferred mixed LB films are characterized by AFM and FTIR techniques.