Cadmium stannate films for immobilization of phospholipid bilayers

Abstract

Cadmium tin oxide (CTO) films on glass substrates were synthesized and functionalized by octadecyltrichlorosilane (OTS). CTO films were transparent with the bandgap of 2.92 eV. They exhibited n-type conductivity and carrier concentration of (3.31 ± 0.38) · 1019 cm−3. Weak temperature dependence points out to a nearly degenerative state of the carriers in the CTO films. Silanization by OTS yielded hydrophobic surface with the contact angle values reaching 103 ± 12 degrees. Silanization of films was followed by a significant reduction of the interfacial capacitance, which upon completion of the functionalization reached levels below 3 μF cm−2. The value of the electric capacitance as well as data of ATIR absorption, hints at sparse and disordered coverage of the CTO surface by octadecylalkylsilane molecules. Such organic layer, however, was able to trigger phospholipid (60% dioleoylphosphocholine and 40% cholesterol) vesicle rupture and the formation of a secondary layer of phospholipid, thus rendering hybrid bilayer surface construct. Such hybrid constructs may be useful in applications where electrode coupling to a model biological membranes and membrane bound proteins is required, such as biosensing and photovoltaics.