Deposition of CTAB-terminated nanorods on bacteria to form highly conducting hybrid systems

Gold nanorods and nanospheres capped with positively charged CTAB are deposited on the surface of gram-positive bacterium having negatively charged teichoic acid brushes. The deposition rate is more than an order of magnitude faster than that for peptide and nucleic acid capped nanoparticles. For the nanorods, never been reported before, the strong electrostatic attraction causes the rods to bend conformally over the curved bacterium surface in random orientations. This leads to formation of an efficient percolating cluster (i.e., low contact resistance and high radius of gyration) with 10⁴-fold higher current at 3-fold lower coverage compared to a monolayer from nanospheres. The high monolayer conductivity at only ∼10% coverage for nanorods has potential for fabricating a novel class of bioelectronic devices by coupling electronic "nanocircuitry" at the surface to the biological function of microorganisms.