Electrochemical properties of interface formed by interlaced layers of DNA- and lysozyme-coated single-walled carbon nanotubes

Multifunctional coatings were produced by the layer by layer assembly of single-walled carbon nanotubes (SWNT) dispersed in DNA and lysozyme (LSZ) on an insulating glass substrate. The electrochemical properties of these mechanically robust biocoatings were characterized for the first time using scanning electrochemical microscopy (SECM) and impedance spectroscopy (IS). SECM surface analysis demonstrated an increase in tip current with a corresponding increase in the number of oppositely polarized interlaced layers, indicating that subsequent layers were not electrically insulated from each other and a direct correlation exists between SECM feedback response and the number of layers. The rate of charge transport was also dependent on the chemical composition/polarity of the outermost surface layer. Coatings terminating in SWNT-DNA resulted in more positive feedback than those terminating in SWNT-LSZ. IS analysis demonstrated that the SWNT-DNA had a low charge transfer resistance in comparison with SWNT-LSZ, which is consistent with the results obtained by SECM. These results enable enhanced fundamental understanding and prediction of the electrical properties of SWNT-biopolymer layers with controlled interlaced polarities and orientation. Furthermore, these finding highlight the potential for SWNT-biopolymers in electronic and sensing applications.