An Investigation of Freezing of Supercooled Water on Anti-Freeze Protein Modified Surfaces

This work investigates how functionalization of aluminium surfaces with natural type III Anti-Freeze Protein （AFP） affects the mechanism of heterogeneous ice nucleation. First the bulk ice nucleation properties of distilled water and aqueous solution of AFP were evaluated by differential scanning calorimetry. Then the modified surface was characterized by Secondary Ions Mass Spectroscopy （SIMS）, Fourier Transform InfraRed （FTIR） spectroscopy and contact angle measurement. Freezing experiments were then conducted in which water droplets underwent a slow controlled cooling. This study shows that compared to uncoated aluminium, the anti-freeze proteins functionalized surfaces exhibit a higher and narrower range of freezing temperature. It was found that these proteins that keep living organisms from freezing in cold environment act in the opposite way once immobilized on surfaces by promoting ice nucleation. Some suggestions regarding the mechanism of action of the observed phenomena were proposed based on the Classical Nucleation Theory （CNT）.