A nanostructure-based plasmonic biochip with the same size as standard 96-well plates for backside reflection-type biosensing was proposed and validated through analyses of biological interactions. The capped gold nanoslit arrays were fabricated on a polycarbonate plastic film using a rapid hot embossing nanoimprint lithography process. The optical properties of capped gold nanoslits with different structure parameters in backside reflection geometry were studied; their refractive index (bulk) and surface (thickness) sensitivities were verified. By changing the cavity length, the coupling between a broadband cavity resonance and a narrowband surface plasmon resonance mode results in an asymmetric Fano resonance in the reflection spectra. The coupling mode is able to enhance the thickness sensitivity by a factor of 2.4 with wavelength interrogation. The bulk and thickness sensitivities were 454 nm/RIU and 1.14 nm/nm, respectively. The protein-protein interaction experiments verified the sensing capabilities and high sensitivity of the capped nanostructures; a limit of detection (LOD) of 2 ng/mL IgA was achieved. Such a multi-well plate with backside reflection-type geometry, decoupling the optical paths, allows for sensing with opaque, bubbly or highly scattering liquids and benefits multiple sensing applications in the biotechnology and agricultural products.
Nanostructure-based surface plasmon resonance (SPR) sensors are capable of sensitive, real-time, label-free, and multiplexed detection for chemical and biomedical applications. Recently, the studies of nanostructure-based aluminum sensors have attracted a large attention. However, the intrinsic properties of aluminum metal, having a large imaginary part of the dielectric function and a longer electromagnetic field decay length, limit nanostructure’s surface sensing capability. To improve the surface sensitivity, a nearly guided wave SPR sensor has been proposed, which enables the surface plasmons to spread along the dielectric layer and increases the interaction volume. Here we proposed the combination between Fano resonances in capped nanoslits and a thin nanodielectric top layer to develop highly sensitive nanostructure-based aluminum sensors. We studied the effects of an Al2O3 protection layer on the optical properties, bulk and surface (wavelength and intensity) sensitivities of capped aluminum nanoslits. We found the top layer can enhance the sensitivities of the Wood’s anomaly-dominant resonance or asymmetric Fano resonance in capped aluminum nanoslits. The maximum improvement can be reached by a factor of 16. The maximum wavelength and intensity sensitivities are 6.8 nm/nm and 150 %/nm, respectively. With 1.71 % intensity change (3 times of noise level), the limit of detection of Al2O3 film thickness was 0.018 nm. We attributed the enhanced surface sensitivity for capped aluminum nanoslits to a reduced evanescent length and sharp slope of the asymmetric profile caused by the capped oxide layer and Fano coupling. The protein-protein interaction experiments verified the high sensitivity of the Al2O3-aliminum capped nanoslits.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.