2D photonic quasi-crystals for nanobiosensing

The last decade has been characterized by artificial electromagnetic (EM) materials, including photonic crystals (PCs) and photonic quasi-crystals (PQCs), making these very attractive given that there are new possibilities to control the EM field in innovative way. Quasiperiodic crystals (QCs) are a new class of materials that have fascinating optical properties lying somewhere between those of disordered and period structures. With the use of PCs and PQCs, it is possible to synthesize novel artificial structures characterized by selective EM responses, which, in turn, undergo significant frequency shifts, in presence of biological material. In the present work we studied artificial EM nanomaterials1 to develop innovative plasmonic nanobiosensors based on Surface Enhanced Raman Scattering (SERS) substrates and working in the visible frequency band. Fabricated gold PQCs in a Thue Morse arrangement are proposed for the engineering of reproducible SERS substrates. Scanning electron microscopy, UV/Vis absorption spectroscopy, dark field microscopy and atomic force microscopy (AFM) are used to characterize the experimental structure. Using a molecular monolayer of pMA (p-mercaptoaniline) as a Raman reporter, we show that high values of SERS enhancement factors can be achieved in photonic structures.