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.

Spectrometer-Free Graphene Plasmonics Based Refractive Index Sensor

“…After setting up the basic definitions, we can start by analyzing the sensitivity under different graphene chemical potentials by analytical means [solving Equations (3) and 5] and finite-elements based simulations (using COMSOL Multiphysics ® ) with designed β and p. The sensitivities from both equations and simulations are obtained when the relative permittivity of the analyte medium is varied around the central value 3.5. Practically, in Equations (3) and (5) both g and s cannot be solutions expressed in a direct analytical formula.…”

“…Optical refractive index (RI) sensors are widely used due to their high sensitivity. Different structures for optical RI sensors have been developed over the past years, such as sensors based on optical fibers [1] and optical resonators [2][3][4][5]. Among these sensing devices, a group is based on the physical phenomenon of surface plasmon resonance (SPR).…”

“…For the case of µ c = 1500 meV and no reflector, the corresponding peak is 2 . After including the reflector, the peak 2 increases dramatically and transforms into peak 3 , which almost reaches perfect-absorption [33]. Generally, by adding the gold reflector and simultaneously by increasing µ c , we can realize stronger absorption.…”

Optimization of heating-temperature on carbothermal reduction of alumina for production of aluminum

“…As mentioned the phase diagram of Al-O-C in Figure 1, is divided to three zones, Zone (I) where the raw materials including the mixture of Al 2 O 3 and C start to react at a temperature of 1500ºC (1773.5K) to produce Al 2 O and CO gasses through reaction in equation (1). Moving from Zone (I) to Zone (II), Al 2 O generation from the zone (I) will increase by an increase of reaction temperature and will react with C in its solid form from Zone (I) to generate Al 4 C 3 in its solidliquid form and CO gas at 1700ºC (1973K) via reaction in equation (2).…”

“…Real-time sensing for many application such as safety of food, medical diagnostic and monitoring of environment represents nowadays a requirement to maintain our daily life tasks. [1][2][3] Surface plasmon resonance (SPR) sensing is label-free capable sensors to fulfill such tasks due to their simplicity and easy to use, their small detection volume and assurance of multiple detections. [4][5] However, commercially, the majority of produced SPR sensors are made of noble metals such as Au and Ag due to their low optical losses in visible-infrared range and chemical stability.…”