Detection of Green-Synthesized Fe3O4/Chitosan Using Spin Valve GMR Sensor with Wheatstone Bridge Circuit

Detection of magnetic nanoparticles (MNPS) label is essential to determine the performance of giant magnetoresistance (GMR) sensors in biosensing technology. This research identifies the potency of green-synthesized Fe3O4/Chitosan on GMR sensors, which has never been explored. MNPS label was synthesized by the coprecipitation method based on the green synthesis route because cost-effective, non-toxic, and reduces waste production. Chitosan is considered the best polymer candidate as a stabilizer of Fe3O4 because they are biodegradable, biocompatible, and hydrophilic. The characteristics of Fe3O4/Chitosan with several concentrations and the effect on sensor signals were investigated. Measurement of Fe3O4/Chitosan using a spin-valve based sensor with a Ta(2nm)/Ir20Mn80(10nm)/Co90Fe10(3nm)/Co84Fe10B4(10nm)/Ta(5nm) structure on Si/SiO2 substrate. Fe3O4/Chitosan has a spherical shape with an inverse spinel cubic structure. The crystallite sizes of Fe3O4/Chitosan (1:1) and Fe3O4/Chitosan (2:1) are 7.9 and 7.5 nm, respectively. Fourier transforms infrared spectra of Fe3O4/Chitosan showed the NH2 bending at 1560 cm−1, C-O-C stretching at 1386 cm−1, and Fe-O stretching at 580 cm−1. The results indicate that chitosan effectively coated the surface of Fe3O4. The sensitivity of the GMR sensor increased to 0.04 mV/mg/mL and 0.05 mV/mg/mL, in the case of Fe3O4/Chitosan (1:1) and Fe3O4/Chitosan (2:1). The increase in the sensitivity was caused by the decrease in diamagnetic material composition, crystallite size and the increase in the saturation magnetization of Fe3O4/Chitosan. Green-synthesized Fe3O4/Chitosan can be detected by GMR sensor by providing a low external magnetic field within the 60s and reach ruthless performance as a magnetic label to be applied to biosensors application in the future.