Gold nano islands and gold nano-networks were synthesized using biofilm as template. Percolation of gold (conductor) through biofilm template (dielectric) was studied using electron microscopy and EDAX. Formed nano-composites showed transition in metal percolation state (i.e. non-percolating to percolating state), as evident from electrical properties.
Plasmonic properties of such gold-biofilm composites were studied using a method that was previously used to study photonic coherence induction by biofilms . This novel method provides a non-coherent, monochromatic, input through biocomposite grown on transparent substrate. Elastically scattered output from the biocomposite was studied using synchronous scan mode. For each case, measured light output from biofilm was enhanced due to coherence induction, as we previously reported . However, peaks were obtained in enhancement spectra that were found to correspond with plasmonic peaks, which in turn depended on Au precursor concentration that had been added. Hence we concluded that plasmon resonance phenomenon can alter the enhancement profile of light passing through gold-biocomposites. Further, the extent of enhancement showed a sharp transition that corresponded with metal atom percolation through the material. Hence we conclude a relation between plasmon delocalization (due to metal atom percolation) and elastic scattering within biofilm. This novel bio-plasmonic material may have applications in plasmon based sensing and improving the efficiency of solar cells.
 Ray, Sanhita, and Anjan Kr Dasgupta. "Light Amplification by Biofilm and Its Polarization Dependence." bioRxiv (2017): 139741.