Effects Of Hydroxyl Group Numbers In Compounds On The Morphology Of Fe₃O₄ And Composites

Fe₃O₄ has widely been used in biomedical,sensors and microwave absorption due to its semi-metallic properties,strong spin polarization,low toxicity and good biocompatibility.The characterization of Fe₃O₄ nanoparticles was different from that of conventional materials due to quantum size effect,surface effect,small size effect and macroscopic quantum tunneling effect.However,Fe₃O₄ nanoparticles were liable to agglomerate because of the larger surface energy,resulting in the modification of Fe₃O₄nanoparticles by various materials.Compounds with different hydroxyl groups were used to modify Fe₃O₄ nanoparticles,which was characterized and analyzed by means of XRD,SEM,FTIR,TGA and VSM.The effect of the hydroxyl group number in these compounds on the formation mechanism and morphology of Fe₃O₄ were systematically studied.In order to enhance the T₂ relaxation signal of Fe₃O₄ nanoparticles,Fe₃O₄/GO composites were prepared by various methods.The effect of Fe₃O₄ shape on the properties of the composites was studied,and the application of the composites in?Magnetic resonance imaging,MRI?was also discussed.The magnetic nanoparticles were prepared by co-precipitation method and hydrothermal method,using polyols molecules containing different hydroxyl groups?Ethanol,Ethylene glycol,Glycerine,Erythritol,Xylitol,Mannitol and Inositol?as modifiers.With the increase of hydroxyl group number,the floret-like,nanosheet,cubic and rod-shaped Fe₃O₄ particles were obtained,indicating that the growth of Fe₃O₄grains in the presence of hydroxyl groups was a non-classical process,and different hydrated iron oxide compounds were generated in the reaction process.Based on previous research results,Fe₃O₄ was synthesized by coprecipitating with linear PEG?20000?containing two hydroxyl groups and dispersed in solutions with different pH values.The morphologic changes and self-assembly mechanism of Fe₃O₄in aqueous solutions with different pH values were investigated.The cage-structural Octa TMA-POSS containing eight hydroxyl groups and hyperbranched macromolecule PPTS containing a number of hydroxyl groups were used to modify Fe₃O₄ and Fe₃O₄nanometer tablets were obtained.The effect of increasing hydroxyl group number on the morphology and properties of the products was investigated.With the increase of hydroxyl group number the dispersion of Fe₃O₄ nanoparticles was improved and smaller Fe₃O₄ grains were obtained.Finally,Fe₃O₄ nanoparticles with different morphology were composite with GO to obtain Fe₃O₄/GO composites.The formation principle of composite materials and the influence of Fe₃O₄ morphology on the morphology and properties of composite materials were investigated.Fe₃O₄/GO was applied in MRI.The composie of Fe₃O₄with GO processed disolution and recrystallization,and superparamagnetic property was maintained.The saturation magnetic intensity was 18.58 emu g^-1.MRI results showed that the transverse relative coefficient?r₂?of Fe₃O₄@Xylitol/GO was 128.083mM^-1·s^-1,which was equal to or slightly exceeded the r₂ relaxation effect of other particles,showing a good relaxation effect.In summary,the modification of magnetic nanoparticles with different polyols and the pH values of dispersion media can regulate the morphology of Fe₃O₄ so that the properties of the products can be controlled.The as-prepared Fe₃O₄/GO composites can enhance image contrast and provide an new option for the preparation of MRI contrast agents.