A Study On Fabrication And Property Of Superparamagnetic Cilia System Made By Anodized Aluminum Oxide Templates

The static bionic cilia system can be widely used in th e preparation of super hydrophobic surface, super adhesion surface and sensitivity of biosensor. In this work, The electronegative nanopatices and electropositive polymers were co-assembled superparamagnetism ?-Fe₂O₃ nanowire arrays in the pores of anodic aluminum oxide?AAO? templates throu gh a bottom-up assembly process. This regular superparamagnetism ?-Fe₂O₃ nanowire arrays can be quickly magnetized in applied magnetic field, and be demagnetized when remove the magnetic field. If wrapped a layer of specific functional groups in the surface of the nanowire arrays, the non-contact and magnetic field controllable feature is expected to greatly improve the sensitivity of biosensor.We have fabricated highly ordered anodized aluminum oxide?AAO? templates with different diameter through traditional two-step anodization and improved hard anodization?HA?. AAO templates with pore diameter?Dp? 90 nm and interpore distance?Di nt? 125 nm were obtained by traditional two-step anodization at 50 V. In the process of fabrication by improve HA, the Dp of AAO templates can be changed by adjusting the voltage rise rate and target voltage. The Dp of AAO templates is 60–110 nm when the voltage rise rate is 10 V/min. While the the voltage rise rate is 2.5 V/min, the Dp of the AAO is enlarged to 160–190 nm.The ?-Fe₂O₃ nanoparticles made by co-precipitation were characterized by using XRD, VSM, TEM and DLS, indicating that the ?-Fe₂O₃ nanoparticles have a typical superparamagnetic properties, relatively uniform particle size, and a small polydisperity. The bare nanoparticles were coated by an anionic polymer in order to improve its colloidal stability and further functionality. DLS study shows that the organic coating thickness is about 7 nm. T he coated nanoparticles was found to have remarkable colloid stability in alkalescent aqueous and high concentration of salt environment.?-Fe₂O₃ nanoparticles and cationic polyelectrolyte infused into the hole of alumina template by soaking method, then assembled by a dialysis process in applied magnetic field. In the process of preparation, we study the assembled situation by adjusting the concentration of the nanoparticles and cationic polyelectrolyte, pore diameter of the AAO templates and charges ratio Z. The results show that the higher concentration of the nanoparticles, the greater pores of AAO templates, the lower charge ratio Z, the easier polymer particles and cationic polyelectrolyte completed assembly in the pores of AAO templates. In the process of the corrosion, found that 0.05 wt% Na OH solution can cause serious damage to the structure of nanowires; while 0.3 M H3PO4 solution which its destructive far less than the Na OH solution, can obtained completely dissociated nanowires. The remanence and coercivity of the nanowire arrays are nearly zero evidenced by VSM, which shows that the ?-Fe₂O₃ nanowire arrays inherit the superparamagnetism behavior of single nanoparticles.