Direct Detection of Green-Synthesized Fe3O4 Magnetic Nanotag Using Double-Chip Configuration of Commercial Giant Magnetoresistance Sensor

The performance of a commercial GMR with a double-chip configuration has been investigated for detecting nanotag. Fe3O4 magnetic nanoparticles (MNPs) as tags were synthesized by co-precipitation method based on green synthesis using Moringa oleifera (MO) extract. Fe3O4 showed a soft ferromagnetic material and a magnetic saturation of 55.0 emu/g. MNPs-ethanol solution are dropped onto the surface of each chip of the sensing element. As a comparison, the performance of a single-chip configuration is also investigated. Obtained bias magnetic field used as a magnetic field sensing double-chip sensor is 3.8 Oe smaller than the single-chip sensor, which is 4.3 Oe, confirmed by the shift in the value of the first derivative order. Configuration of double-chip sensor in detecting Fe3O4 has a smaller LoD of 2.4 mg/mL compared to the single-chip configuration of 3.8 mg/mL. Therefore, Green-synthesized Fe3O4 as biocompatible magnetic tags in combination with commercial GMR sensors using double-chip configuration is promising for magnetic-based biosensor applications in driving more responsive detection and enabling portability by using a smaller energy source.