Semiconducting bacterial biofilm based on graphene-MoS2 template and component dependent gating behavior

In this paper, we report for the first time, the synthesis of a semiconducting biofilm. Photosynthetic bacterial biofilm has been used to weave together MoS2 nanosheets into an adherent film grown on interdigitated electrodes. Liquid-phase exfoliation of bulk MoS2 powder was used to obtain MoS2 nanosheets. A synchronous-fluorescence scan revealed the presence of two emission maxima at 682nm and 715nm for the MoS2 suspension. Such maxima with bandgap energy 1.82 and 1.73 eV corresponded to the single and double layer of MoS2. The presence of such single and multi-layered structures was confirmed by Raman spectroscopy, FTIR studies, and electron microscopy. The current-voltage (I-V) studies of such a bio-nano hybrid revealed the emergence of the gated nature of the current flow. This Schottky diode like behavior, reported earlier for Graphene-biofilm junctions, is also observed in this case. Gating voltage depended on the composition of the biofilm. The semiconductor biofilms, when studied using electrochemical impedance spectroscopy, revealed characteristic Nyquist and Bode plots, suggesting special circuit-equivalence for each film. While Mos2 was marked with stability with respect to variations in RMS voltage and bias voltage, the graphene biofilm was unique by the absence of any Warburg element.