SERS and SE-FTIR platforms from plasmonic bismuth thin films for label-free multiplexed biomolecules detection

This work focuses on fabricating plasmonic Bismuth (Bi) thin films which serves as alternative Surface-Enhanced Raman Spectroscopy (SERS) and Surface-Enhanced Fourier Transform Infrared Spectroscopy (SE-FTIR) platforms for enabling the detection of a diverse range of biomolecules. The detection of these biomolecules can act as precursors in identifying imbalances in the overall mental and physical health of species. The presence of multiple surface plasmon resonances (Mult. SPRs) of interband plasmonics in Bi favored the detection of multiple analytes. The effective absorption of intense localized surface plasmon resonance (LSPR) is facilitated by achieving the optimum surface morphology. Moreover, ensuring an optimum rms roughness, coupled with a higher contact angle (CA), imparts better adherence and the analyte’s confinement to the film surface. The orthorhombic atomic orientations, as observed through GI-XRD and HRSTEM, align with the Raman spectrum. XPS etching confirms the presence of a prominent metallic phase. The detection of a wide array of life molecules, ranging from amino acids to nutrients to proteins, exhibits an enhanced scattering response, as indicated by values of the SERS Enhancement Factor (EF). A comparatively higher response of 4.77 × 10³ SERS EF was observed for L-tyrosine (Tyr) followed by L-phenylalanine (Phe), Hemoglobin (Hb), and Bovine Serum Albumin (BSA). The identification of individual building blocks to complex proteins showcases the potential of these platforms, offering multiplexed and alternative biosensing platforms from Bi thin film.