Inexpensive and Flexible SERS Substrates on Adhesive Tape Based on Biosilica Plasmonic Nanocomposites

We demonstrate a simple method to prepare porous biosilica plasmonic composites on an inexpensive flexible substrate. The method does not require any chemical modification of the materials, and it allows the deposition of the nanocomposite on regular office-grade adhesive tape. This material was further characterized via scanning electron microscopy and optical microscopy, revealing unique properties such as pore size, plasmon resonance, and Raman enhancement factors suitable for biosensing applications. To demonstrate the usability of these strips in SERS-based sensing applications, we performed measurements on several proteins and bacteria of interest. Because of the porous nature of the nanocomposite, smaller proteins and nanostructures disperse within the material and present a reduced particle density for optical detection, which limits the ability to measure low concentrations of the analyte. On the other hand, particles that are larger than ∼100 nm concentrate at the top surface of the material and will be easier to detect via focused optical beams. We demonstrate that SERS can help detect and identify bacteria on this nanocomposite and believe that other applications are possible as well, in particular for the chemical characterization of biological particles of nano- to micrometer sizes.