  We report optically as well as electronically controlled, bio-electronic
field-effect transistor (FET) based on the hybrid film of a photo-active purple
membrane and electronically conducting single-walled carbon nanotubes (SWNTs).
Two dimensional (2D) crystal of bacteriorhodopsin forms the photoactive center
of the bio-nano complex, whereas one dimensional (1D) pure SWNTs provides the
required electronic support. The hybrid structure shows a conductivity of 19
microS/m and semiconducting characteristics due to preferential binding with
selective diameters of semiconducting SWNTs only. The bio-electronic transistor
fabricated using direct laser lithography shows photoconductivity of 13.15
microS/m and well-controlled optical and electronic gating with a significant
On/Off switch ratio of 8.5. The device demonstrates well-synchronized
electronic and optical gating wherein, n-type FET shows complementary p-type
characteristics due to optically controlled proton-pumping by
bacteriorhodopsin. Fabricated bio-electronic transistor displays both
electronically and optically well-controlled, bi-functionality.
