Study of Biosensors Based on Fe Nanowires
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Study of Biosensors Based on Fe Nanowires YANG Hao and CHEN Yu-quan State Specialized Laboratory of Biomedical Sensors, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China ABSTRACT Anodic aluminum oxide (AAO) template was prepared by using anodizing voltage stepdecreasing method after two-step oxide method. Based on AAO template, Fe nanowires arrays were electrochemically deposited. Fe nanowires were coated by chitosan. Fe nanowires/chitosan was synthesized by glutaraldehyde as cross-linking reagent. By crosslinking α-human chorionic gonadotropin (α-HCG), biological probes with Fe nanowires/chitosan/antibody were prepared. An easy operating, easy taking and rapid reacting magnetic detecting system was developed after optimizing the geometry parameters of detect coil. Different concentration samples with 1, 2 and 5 g(Fe)/L were detected. The results show that the sensitivity of system is 0.2 g(Fe)/L and can be improve better. INTRODUCTION In the last decade, nanowires and other 1D nanostructures have emerged as potential components suitable to be integrated in devices specially designed for sensing applications such as chemical sensing, biosensing or photodetection. Their use in solid-state sensing technologies has been demonstrated to be very promising due to the novel properties and functionalities derived from their high surface-to-volume ratio, controlled surface interactions, efficient nanoscale transduction mechanisms, and quantum confinement effects[1-3]. EXPERIMENT Materials and instruments Aluminum foil (purity, 99.999%, thickness, 0.5 mm) was obtained from Beijing Mengtai Technology and Development Center, China. Chitosan (deacetylation degree >90%) was obtained from Sinopharm Chemical Reagent Co, Ltd., China. Mouse anti-human α-HCG (9.6 g l–1) was obtained from Shanghai Genering Biotech Co, Ltd., China. The other reagents used were analytical reagents and were not purified before use. Deionized water was used in all experiments. Testing instruments: ultraviolet spectrophotometer, CARY 100, was purchased from Varian, USA. Dispensing system, XYZ3000, was purchased from BioDot, USA. Superconducting quantum interference device (SQUID), MPMS XL-5, was purchased from Quantum Design, USA. Field-emission scanning electron microscope (FSEM), SIRION-100, was purchased from FEI, USA. Transmission electron microscope (TEM), JEM-1200EX, was purchased from JEOL, Japan.
Preparation of Fe nanowires After suitable cutting, electrochemical polishing, and washing, aluminum foil was dipped in 0.3 M oxalic acid solution with ice bathing, and anode oxidized at 40 V DC for 1 h. It was then soaked in a mixture of phosphoric acid and chromic acid for 1 h, and the same anode oxidation was repeated. After decreasing the anodic oxidation voltage step by step, the AAO template was obtained. The electrochemical deposition solution was made of FeSO4·7H2O (l00 g l–1), (NH4)2SO4 –1 (15 g l ), MgSO4 (30 g l–1), ascorbic acid (1 g l–1), and glycerin (2 ml l–1). AAO template was dipped in it and
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