Husna Ajrina, Harlina Ardiyanti, Pinaka Elda Swastika, Nurul Imani Istiqomah, Deska Lismawenning Puspitarum, Zurnansyah, Edi Suharyadi
Extensive research into giant magnetoresistance (GMR) biosensing technology highlights the significance of carefully analyzing suitable magnetic nanotags and their impact on signal detection. This study developed the commercial chip-based GMR sensor as a transducer, integrated with a basic differential amplifier and Arduino-based microcontroller system and evaluates the effectiveness of a biosensor in detecting green-synthesized magnetic ferrofluids monitored in real-time as potential magnetic nanotags. Three types of ferrofluids —MnFe₂O₄, CoFe₂O₄, and Fe₃O₄— were synthesized with varying concentrations using a green coprecipitation technique with extracts of Moringa oleifera. An inverse spinel crystalline structure with a face-centered cubic arrangement (Fd-3m) was observed in all samples, with average particle size distributions of 6.8 nm, 8.5 nm, and 9.3 nm for MnFe₂O₄, CoFe₂O₄, and Fe₃O₄, respectively. The saturation magnetizations of 18.9, 38.3, and 54.4 emu/g for MnFe₂O₄, CoFe₂O₄, and Fe₃O₄, respectively. The sensor demonstrated strong detection capabilities for magnetic ferrofluids, exhibiting a linear sensitivity to the concentration of each ferrofluid. The bias magnetic field for sensing, confirmed by the shift in the first derivative order, was determined to be 4.3 Oe. Among the ferrofluids, Fe₃O₄ showed the highest sensitivity, as reflected by the steepest slope, followed by CoFe₂O₄ and MnFe₂O₄ with the sensitivity of 8.2, 7.7, and 6.8 mV/(mg/mL), respectively. These findings highlight the considerable promise of integrating commercial GMR chip sensors (AAL024) with green-synthesized magnetic ferrofluids for enhanced biomolecule detection. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2026.
Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia; Department of Physics, Institut Teknologi Sumatera, Lampung, Indonesia; Department of Physics Education, Universitas Negeri Yogyakarta, Yogyakarta, Indonesia
