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

Detection of magnetic nanoparticles (MNP S ) label is essential to determine the performance of giant magnetoresistance (GMR) sensors in biosensing technology. This research identifies the potency of green-synthesized Fe 3 O 4 /Chitosan on GMR sensors, which has never been explored. MNP S 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 Fe 3 O 4 because they are biodegradable, biocompatible, and hydrophilic. The characteristics of Fe 3 O 4 /Chitosan with several concentrations and the effect on sensor signals were investigated. Measurement of Fe 3 O 4 /Chitosan using a spin-valve based sensor with a Ta (2nm)/Ir 20 Mn 80 (10nm)/Co 90 Fe 10 (3nm)/Co 84 Fe 10 B 4 (10nm)/Ta (5nm) structure on Si/SiO 2 substrate. Fe 3 O 4 /Chitosan has a spherical shape with an inverse spinel cubic structure. The crystallite sizes of Fe 3 O 4 /Chitosan (1:1) and Fe 3 O 4 /Chitosan (2:1) are 7.9 and 7.5 nm, respectively. Fourier transforms infrared spectra of Fe 3 O 4 /Chitosan showed the NH 2 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 Fe 3 O 4 . The sensitivity of the GMR sensor increased to 0.04 mV/mg/mL and 0.05 mV/mg/mL, in the case of Fe 3 O 4 /Chitosan (1:1) and Fe 3 O 4 /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 Fe 3 O 4 /Chitosan. Green-synthesized Fe 3 O 4 /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.