Hybrid Mushroom Nanoantenna for Fluorescence Enhancement by Matching the Stokes Shift of the Emitter

Abstract

Nanoantenna-enhanced fluorescence is a promising method in many emergent applications, such as single molecule detection. The excitation and emission wavelengths of emitters can be well separated depending on the corresponding Stokes shifts, preventing optimal fluorescence enhancement by a rudimentary nanoantenna. We illustrate a hybrid mushroom nanoantenna that can achieve overall enhancements (e.g., excitation rate, quantum yield, fluorescence enhancement) in fluorescence emission. The nanoantenna is made of a plasmonic metal stipe and a dielectric cap, and the resonances can be flexibly and independently controlled to match the Stokes shift of the emitter. By fully leveraging the advantages of the large field enhancement from the metal and the low loss feature from the dielectric, a fluorescence enhancement factor (far field intensity) twice (20 times) as high as that from a pure metallic antenna can be attained, accompanied by improved directivity. Approximately 70% of the overall radiation was directed toward the mushroom cap via coupling to the dielectric resonance, which could benefit the collection efficiency. This hybrid concept introduces a way to build high-performance nanoantennas for fluorescence enhancement applications.

Applications of Hybrid Metal‐Dielectric Nanostructures: State of the Art

“…[292] In ref. [293], a hybrid mushroom-shaped nanoantenna was designed to achieve high excitation rates, quantum yields, and fluorescence enhancements. The nanostructure consisted of a plasmonic metal stripe and a dielectric cap.…”

Nanoantenna‐Enhanced Light‐Emitting Diodes: Fundamental and Recent Progress

“…c) Reproduced with permission. [ 51,104 ] Copyright 2018, 2019, American Chemical Society. d) Reproduced under the terms of Creative Commons Attribution 4.0 Public License.…”

“…[ 103 ] The silicon nanorod is mainly responsible for redirecting the emission from the plasmonic‐enhanced dipole radiation to the forward direction. Other novel structures, like hybrid mushroom and metal nanodisk–dielectric nanoring proposed by Sun et al., [ 51,104 ] are shown in Figure 6c. They found that when the plasmon mode of the metal constituent resonates strongly with the magnetic dipole mode of the dielectric constituent, the excitation field was greatly improved and the outgoing light is directed in the vertical direction.…”

Gold Ion Beam Milled Gold Zero-Mode Waveguides

“…Non-radiative relaxation from the excited state reduces the fluorescence quantum yields of molecular probes used in fluorescence experiments, which affects the maximum rate at which information is obtained by detected photons. Amelioration comes from advances being made with techniques such as near-field scanning optical microscopes [ 6 , 7 ], the use of nanostructures such as nano-antennas [ 8 , 9 , 10 , 11 , 12 , 13 ], and zero-mode waveguides (ZMW) [ 14 ]. Nano-antennas and zero-mode waveguides enhance fluoresence by creating a surface plasmon resonance that is confined to an active region within the nanostructure.…”