Enhanced optical properties and localized surface plasmon resonance of magnetite/silver nanocomposites under electric field and wavelength variation

The study of optical properties and localized surface plasmon resonance (LSPR) of magnetite/silver nanocomposites (NCs) has been successfully investigated. The NCs were synthesized using the co-precipitation method and coated on the Au film surface with a four-layer Kretschmann configuration system. Light source wavelengths of 405 and 450 nm were used to investigate the influence of the varied wavelength on t the optical properties and LSPR curve characteristics. Electric fields of 1.6, 2.4, and 3.2 V/cm were applied to the substrate/Au film/magnetite/silver NCs/air sample structure for ellipsometer and SPR testing. The findings indicate that the use of an electric field improves the optical properties, a real part of optical conductivity, complex dielectric constant (real part, and imaginary part, ), complex refractive index (real part, and imaginary part, ), and optical absorption (), resulting in a rise in the LSPR angle and a decrease in minimum reflectance. Furthermore, the variation in the incident light wavelength at 405, 450, and 632.8 nm causes an increase in the LSPR angle by 1.21o, 0.97o, and 0.66o, respectively. At a wavelength of 405 nm, the application of electric fields of 1.6, 2.4, and 3.2 V/cm induced shifts in the LSPR angle from 65.87º to 65.99º, 66.23º, and 66.49º, respectively. At 450 nm, the LSPR angle shifted from 63.41º to 63.62º, 63.77º, and 63.94º, respectively. The significant change in the LSPR angle and minimum reflectance due to the applied electric field and wavelength indicates that applying an electric field to the LSPR sensor surface with varied wavelengths provides the scenario to improve the performance of the SPR biosensor for future applications. © Qatar University and Springer Nature Switzerland AG 2025.