Toward Bioelectronic Nanomaterials: Photoconductivity in Protein-Porphyrin Hybrids Wrapped around SWCNT

The development of sophisticated ordered functional materials is one of the important challenges in current science. One of the keys to enhance the properties of these materials is the control of the organization and morphology at different scales. This work presents a novel bioinspired methodology to achieve highly ordered donor/acceptor bio-nanohybrids using a designed repeat protein as scaffold, endowed with photoactive and electron donating porphyrin (P) units, to efficiently wrap around electron accepting single wall carbon nano-tubes (SWCNT). A systematic experimental and theoretical study to evaluate the effect of the length of the protein reveals that longer proteins wrap around the SWCNT in a more efficient manner due to the stronger supramolecular interaction existing between the inner concave surface of the protein (namely Trp and His residues) and the convex surface of the (7,6)-SWCNT. Interestingly, spectroscopy and X-ray diffraction data further confirm that the so-called protein-P-SWCNT donor-acceptor bio-nanohybrids retain the original protein structure. Finally, the new bio-nanohybrids show a remarkable enhancement on the photoconductivity values by flash-photolysis microwave conductivity (FP-TRMC technique) demonstrating that the major charge carriers of electrons are injected into the SWCNTs and move along the 1D-structures.