Characterization of Microstructure and Composition of Fe-B Nanobars as Biosensor Platform
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0962-P09-14
Characterization of Microstructure and Composition of Fe-B Nanobars as Biosensor Platform Suiqiong Li1, Liling Fu1, Chongmin Wang2, Scott Lea2, Bruce Arey2, Mark Engelhard2, and Z.-Y. Cheng1 1 Materials Research and Education Center, Auburn University, Auburn, AL, 36849 2 Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA, 99352 ABSTRACT Individual magnetostrictive nanobars and magnetostrictive nanobar arrays were recently introduced as a high performance biosensor platform. In this paper, we report the fabrication and characterization of magnetostrictive nanobars based on Fe-B alloy. The nanobars were synthesized using a template-based electrochemical deposition method. The composition and microstructure of the Fe-B nanobars are directly related to their performance as a biosensor platform. The Fe-B nanobar arrays and individual nanobar were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as Auger electron spectroscopy (AES). Morphologically, nanobars have a very flat top and a smooth cylindrical surface, which are critical factors for obtaining high performance as sensor platforms. Structurally, electron diffraction reveals that the Fe-B nanobars are amorphous. AES analysis indicates that Fe-B nanobars show no significant compositional variation along the length direction. It is found that the nanobars were covered by an oxidation layer of a typical thickness of ~ 10 nm. It is believed that this oxidation layer is related to the passivation of nanobars in air. High temperature annealing and subsequent structural analysis indicate that the Fe-B nanobars possess a good thermal stability. INTRODUCTION Acoustic Wave (AW)-based biosensors have attracted considerable attentions in the development of revolutionary biodetection technologies because of their high sensitivity and real-time detection capability [1-4]. Research indicates that MEMS-based AW sensor platforms, such as microcantilevers, exhibit extremely high sensitivity. It was demonstrated that Si-based microcantilevers have the capability of detecting one signal bacterium cell [4]. AW-based biosensors are mass sensors. To build a biosensor, a biological receptor layer, such as the antibody or the phage, is immobilized on the AW device to capture target antigens [5]. The binding of the target antigens causes a mass or mechanical property change on the sensor surface, which results in a shift of the resonance frequency of the device. Mass sensitivity (Sm) and merit quality factor (Q value), are two critical parameters that need to be optimized for the development of high performance AW-based biosensors. Sm is defined as the shift in the resonance frequency caused by unit mass load, while the Q value represents the sharpness of the resonance frequency peak and hence determines the resolution of the AW-based biosensor. It is highly desirable to have a sensor platform with high mass sensitivity and high Q value. At present, most AW devices are based on silicon or piezoelec
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