The optoelectric tunability effect of structurally patterned Fe3O4-Au assembly on Rhodamine 6G signals under Magneto-SERS measurements

The magneto-plasmonic tunability property of magnetite-gold complex (Fe₃O₄-Au) colloids has garnered significant interest in bio-sensory applications like surface-enhanced Raman spectroscopy (SERS). In many studies, this tunability does not only depend on the external magnetic field contribution but also on the concentration ratio between Fe₃O₄ and Au. This would require multiple preparation of Fe₃O₄-Au colloidal badges. In this study, a magnetically stimulated Fe₃O₄-Au colloidal suspension in polyvinyl alcohol was spin-coated, forming a micro-patterned thin film on a silicon wafer substrate for assessing the SERS vibrational signal response of Rhodamine 6G (R6G). The varying concentration ratio between Fe₃O₄ and Au across three regions of interest within the single cast resulted in differing optoelectronic behaviour. Such was observed from diffuse reflectance UV-Vis-NIR spectroscopy measurements, and its impact on different Raman signals of R6G. The introduction of an external magnetic field also led to approximately 133% higher peak intensity and improved spectral resolution of R6G under SERS measurements. This implies that the magnetic field polarization of Fe₃O₄ domain electrons influences plasmon electrons of Au nanoparticles leading to tuning of electronic-influenced vibrations of nearby analyte molecules. The variability of nanoparticle concentration ratios, configurations and the magneto-optoelectronic effect of this design template, provide flexibility and tunability in diagnosing biomolecule signals under SERS.