Abstract
We investigated the coupling phenomenon between plasmonic resonance and waveguide modes through theoretical and experimental parametric analyses on the bimetallic waveguide-coupled long-range surface plasmon resonance (Bi-WCLRSPR) structure. The calculation results indicated that the multi-plasmonic coupling gives rise to the enhanced depth-to-width ratio of the reflection dip compared to that of LRSPR excited using a single set of Ag and Teflon. The optimized thickness of Ag(40 nm)/Teflon(700 nm)/Ag(5 nm)/Au(5 nm) was obtained and generated the highest plasmon intensity enhancement, which was 2.38 folds in comparison to the conventional bimetallic surface plasmon resonance (SPR) configuration (Ag/Au). 17β-Estradiol was used in the fluorescence enhancement experiment by the reflection geometry-based system, wherein the excitation light source was on the side of a WC-LRSPR chip opposite to that of the light detection unit. The phenomenon of surface plasmon-couple emission (SPCE) depends on the number of 17β-estradiol molecule promoters from female sex steroid hormones, which demonstrated a limit of detection (LOD) of 2 pg mL−1 and 1.47-fold fluorescence improvement as compared to the non-coated material on the surface of pristine glass. This enhanced WC-LRSPR can readily find application in fluorescence escalation needed in cases where a weak fluorescence signal is predicted, such as the small volume of liquid containing fluorescent dyes in biological diagnosis.
Highlights
The phenomenon of surface plasmon resonance (SPR) sensors has been exploited for a long time and has been used for food quality tests,[1,2,3] drug 22450 | RSC Adv., 2021, 11, 22450–22460Paper eld) enhancement factor at the metal–analyte interface of a bimetallic nano lm is greater than that for Au.[19]
The optimized thickness of Ag(40 nm)/Teflon(700 nm)/Ag(5 nm)/Au(5 nm) was obtained and generated the highest plasmon intensity enhancement, which was 2.38 folds in comparison to the conventional bimetallic surface plasmon resonance (SPR) configuration (Ag/Au). 17b-Estradiol was used in the fluorescence enhancement experiment by the reflection geometry-based system, wherein the excitation light source was on the side of a WC-LRSPR chip opposite to that of the light detection unit
The LRSPR structure, comprising a thin metal layer sandwiched between two insulators, was rst proposed by Sarid in 1981.29 Quail et al observed the LRSPR phenomenon experimentally on Ag and aluminium (Al) lms, proving that the LRSPR can reduce the resonance-angle width by an order of magnitude compared with conventional SPR sensors.[21]
Summary
The phenomenon of SPR sensors has been exploited for a long time and has been used for food quality tests,[1,2,3] drug 22450 | RSC Adv., 2021, 11, 22450–22460Paper eld) enhancement factor at the metal–analyte interface of a bimetallic nano lm is greater than that for Au.[19].
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