title: Highly Sensitive Aluminum-Based Biosensors using Tailorable Fano Resonances in Capped Nanostructures.
abstract: Metallic nanostructure-based surface plasmon sensors are capable of real-time, label-free, and multiplexed detections for chemical and biomedical applications. Recently, the studies of aluminum-based biosensors have attracted a large attention because aluminum is a more cost-effective metal and relatively stable. However, the intrinsic properties of aluminum, having a large imaginary part of the dielectric function and a longer evanescent length, limit its sensing capability. Here we show that capped aluminum nanoslits fabricated on plastic films using hot embossing lithography can provide tailorable Fano resonances. Changing height of nanostructures and deposited metal film thickness modulated the transmission spectrum, which varied from Wood's anomaly-dominant resonance, asymmetric Fano profile to surface plasmon-dominant resonance. For biolayer detections, the maximum surface sensitivity occurred at the dip of asymmetric Fano profile. The optimal Fano factor was close to -1.3. The wavelength and intensity sensitivities for surface thickness were up to 2.58 nm/nm and 90%/nm, respectively. The limit of detection (LOD) of thickness reached 0.018 nm. We attributed the enhanced surface sensitivity for capped aluminum nanoslits to a reduced evanescent length and sharp slope of the asymmetric Fano profile. The protein-protein interaction experiments verified the high sensitivity of capped nanostructures. The LOD was down to 236 fg/mL.
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, 128, section 2, Academia Road, Nangkang, Taipei 11529, Taiwan.
authors.forename: Kuang-Li
authors.initials: KL
authors.lastname: Lee
authors.affiliation: Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan.
authors.forename: Hsuan-Yeh
authors.initials: HY
authors.lastname: Hsu
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, 128, section 2, Academia Road, Nangkang, Taipei 11529, Taiwan.
authors.forename: Meng-Lin
authors.initials: ML
authors.lastname: You
authors.affiliation: Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan.
authors.forename: Chia-Chun
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, 128, section 2, Academia Road, Nangkang, Taipei 11529, Taiwan.|Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: Ming-Yang
authors.initials: MY
authors.lastname: Pan
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, Hokkaido 060-0808, Japan.
authors.forename: Xu
authors.initials: X
authors.lastname: Shi
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, Hokkaido 060-0808, Japan.
authors.forename: Kosei
authors.initials: K
authors.lastname: Ueno
authors.affiliation: Research Institute for Electronic Science, Hokkaido University, Hokkaido 060-0808, Japan.|Department of Applied Chemistry &Institute of Molecular Science, National Chiao Tung University, Hsinechu 20010, Taiwan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Misawa
authors.affiliation: Research Center for Applied Sciences, Academia Sinica, 128, section 2, Academia Road, Nangkang, Taipei 11529, Taiwan.|Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan.|Institute of Biophotonics, National Yang-Ming University, Taipei 11221, Taiwan.
authors.forename: Pei-Kuen
authors.initials: PK
authors.lastname: Wei