Application Research Of Fe₃O₄ Nanoparticles In Magnetic Biological Detection And Flexible Magnetoelectric Materials

Magnetic nanomaterials(MNPs)have unique physical properties,and have become one of the rapidly developing materials with great research value.MNPs have great application prospects in magnetic sensors,data storage,biomedicine,and environmental engineering.Among nanomaterials,Fe3O4 nanoparticles(NPs)have the advantages of high magnetization,better magnetostrictive properties,easy surface modification and non-toxic biocompatibility,etc.,and are widely used in the above fields.Many researchers focus on the development of magnetic particle applications,among them,the application of giant magnetoresistance(GMR)biological detection and flexible magnetoelectric composite materials is of great concern.Compared with other biosensors,GMR biosensors have the advantages of high sensitivity,low noise,stable magnetic labeling,repeatability and quantification,and are widely used in the field of biomedicine.The principle of the GMR biosensor is actually to detect the dispersion field generated by the magnetic tag.Therefore,the magnetic properties of the magnetic tag will directly determine the detection result.In actual detection,people hope that the sensor can have high detection accuracy,which requires the magnetic label material to have high saturation magnetization,good dispersion and uniform particle size distribution.At present,scientists have adopted many methods to improve the performance of magnetic tags,but there are still deficiencies,and it is necessary to develop new magnetic tags to meet the needs of ultra-low concentration detection.Fe3O4 NPs except to used in magnetic biological detection,it can also be applied in flexibility flexible magnetoelectric composite materials.This material has the advantages of good processing performance and flexibility,and has great application potential in the preparation of wearable devices.It is a new hot spot in the application research of Fe3O4 particles in recent years.In the actual application of the device,people often expect it to have a higher sensitivity and a wider range of application,which puts new requirements on the performance of the material.As an important phase in magnetoelectric composite materials,magnetostrictive materials have a direct impact on the performance of magnetoelectric conversion.Therefore,it is necessary to explore magnetostrictive materials.In this paper,we focus on the application which including biological detection and flexible ME composite material of magnetic nanoparticles,design and preparation Fe3O4 particles with suitable size and morphology,and applied in the above two fields,the specific work is as follows:(1)Design and preparation of rod-shaped Fe3O4 nanoparticles for biological detection and explored the best preparation process.Fe3v4 NPs had morphology,magnetic anisotropy and high axial magnetization,applying it to biological detection is expected to improve detection accuracy.Five rod-shaped ?-Fe2O3 precursors with different sizes were prepared by hydrothermal method,and reduction ?-Fe2O3 with length of 310 nm and a diameter of 62 nm to Fe3O4.During this period,the effect of reaction temperature and reaction time on the reduction process was discussed by using the control variable method,it was found that?-Fe2O3was fully reacted to Fe3O4 with no impurities when the reaction temperature was 520? and the reaction time was 1 h.(2)Superparamagnetic Fe3O4 NPs were prepared for flexible magnetoelectric composite materials,and the suitable preparation process was discussed.Superparamagnetic Fe3O4 NPs have the advantages of low coercive force and low remanence.Using this as a magnetostrictive phase will greatly improve the hysteresis of the material and provide conditions for the development of low noise and high sensitivity magnetoelectric sensors.Four kinds of spherical Fe3O4 NPs with different particle sizes were synthesized by hydrothermal method.The particles have uniform size,good dispersion,and exhibit superparamagnetic properties.(3)Build a biological detection platform,apply rod-shaped particles to GMR detection,and study the effects of particles on the output signal,sensitivity,detection limit,and repeatability.It was found that the particles had an ultra-low detection limit(LOD)of 0.05 ng/mL,which was attributed to the shape anisotropy of the rod-shaped Fe3O4 that can produce a large dispersion field.In the detection process,a wide linear range of 0.05 ng/mL-1000 ng/mL was obtained.In addition,in multiple tests,the magnetic label showed excellent repeatability,which is attributed to the stable and effective dispersion field of the rod-shaped Fe3O4.(4)Select the appropriate size of superparamagnetic Fe3O4 particles to prepare flexible magnetoelectric composite film,and build a magnetoelectric detection platform to test the effect of particle doping amount on piezoelectric performance and magnetoelectric conversion performance.As a result,it was found that as the content of the particles increased,the piezoelectric performance continued to weaken.This was because the addition of particles hindered the movement of the domain walls,thereby reducing the piezoelectric effect.As the content of particles increases,the magnetoelectric properties show a tendency to increase first and then decrease.The optimal particle content is 5 wt%and the magnetoelectric coupling coefficient ?33 is 1.16 mV·cm-1·Oe-1.Moreover,due to the extremely low coercive force and remanence of the superparamagnetic particles,the film has almost no hysteresis in the magnetoelectric test.This high-sensitivity flexible magnetoelectric composite film laid the foundation for the future development of high-sensitivity,low-noise magnetic sensors.