Rafiqa Wulandani, Vincent Milano, Muhammad Riswan, Rafli Fandu Ramadhani, Karina Anggraeni, Putri Dwi Jayanti, Nurul Imani Istiqomah, Nugraheni Pupita Rini, Larrisa Jestha Mahardhika, Mahardika Yoga Darmawan, Julia Angel, Edi Suharyadi
In this study, the development of a green-synthesized surface plasmon resonance (SPR) biosensor based on Fe3O4/Ag nanocomposites (NCs) for bovine serum albumin (BSA) detection through an externally applied magnetic field has been explored. The Fe3O4 nanoparticles (NPs) were synthesized using Moringa oleifera extract and incorporated with Ag NPs. Analysis of structural, optical, and magnetic characterizations confirmed crystalline Fe3O4/Ag NCs with homogeneous Ag distribution, band-gap narrowing, and near-superparamagnetic behavior. For the SPR measurements, resonance angles of 46.41°, 46.52°, and 46.64° for the integrated Fe3O4/Ag NCs in prism/Au configuration were observed depending on 1, 3, and 5 mg/mL BSA concentrations, with a detection limit of 0.40 mg/mL and a R-squared value of 0.99. For the magneto-optic SPR (MOSPR) measurements, an increase in resonance angles of 46.61°, 46.60°, and 46.70° was detected with a magnetic field strength of 40, 50, and 60 Oe, respectively, resulting in full width at half maximum broadening and an increase in detection accuracy in MOSPR compared with conventional SPR, while preserving the same detection limit. The transverse magneto-optical Kerr effect response exhibited a higher sensitivity than conventional SPR, resulting in an approximately twofold enhancement in the MOSPR configuration. The quantitative analysis reveals how the response of green-synthesized Fe3O4/Ag magneto-plasmonic NCs evolves under an applied magnetic field, enabling a magnetically modulated SPR biosensing response for BSA. © 2026 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license. http://creativecommons.org/licenses/by-nc-nd/4.0/
Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia; Research Center for Food Technology and Processing, National Research and Innovation Agency, Yogyakarta, Indonesia; Department of Physics, Institut Teknologi Sumatera, Lampung, Indonesia; Research Center for Nanotechnology System, National Research and Innovation Agency, Tangerang Selatan, Indonesia