Electrochemically and catalytically active layer-by-layer films of myoglobin with zirconia formed by vapor-surface sol–gel deposition

A myoglobin (Mb) film was successfully assembled layer-by-layer with zirconia formed by vapor-surface sol–gel deposition on solid surfaces. The method involved vaporization of zirconium butoxide (Zr(OBu)4) into thin layers of water, forming ZrO2 sol–gel layers after hydrolysis of Zr(OBu)4. Mb was assembled by adsorption alternated with the ZrO2 layers. The {ZrO2/Mb}n layer-by-layer films at pyrolytic graphite electrodes demonstrated a pair of well-defined and nearly reversible CV peaks at about −0.34 V vs SCE, characteristic of Mb Fe(III)/Fe(II) redox couple, and used to catalyze reduction of oxygen and hydrogen peroxide. FTIR spectroscopy and comparison studies with {ZrO2/catalase}n films suggest that Mb in the zirconia sol–gel films essentially retains its native structure. Compared with Mb layer-by-layer films assembled with ZrO2 nanoparticles, {ZrO2/Mb}n films showed larger numbers of electroactive bilayers and higher maximum surface concentration of electroactive Mb, which may be related to the unique structure of ZrO2 sol–gel with higher porosity.