Abstract
Surface plasmon field-enhanced fluorescence (SPF) has been one of the powerful tools for biosensors and bioimaging. A wavelength-scale periodic structure coated with a thin metal film is called a plasmonic chip, and it can provide SPF. SPF of Cy5-streptavidin (Cy5-SA) was measured on a biotinylated plasmonic chip with a grating of 480 nm-pitch. The optimal structure of a plasmonic sensor-chip was designed for improving detection sensitivity. The silver film thickness dependence of the SPF intensity was measured under the irradiation of the top panel of a sensor chip. Furthermore, the dependence of the SPF intensity on the distance from the metal surface was also investigated. The optimal structure for the largest fluorescence enhancement factor was 150 nm-thick silver and 10 nm-thick SiO2 layers due to the enhanced electric field (excitation field), the surface plasmon coupled emission (SPCE), and the interference effect with reflected light. The largest enhancement factor was found to be 170-fold. Furthermore, not only the largest fluorescence intensity but also stable lower background noise were found to be essential for higher-sensitive detection.
Highlights
Surface plasmon field-enhanced fluorescence (SPF) has been known as one of the powerful tools in immunosensors [1,2]. This is because fluorescence is a sensitive technique compared with methods measuring absorbance and reflectivity, and further, enhanced fluorescence can improve the detection sensitivity compared with the general fluorescence method
Plasmonic chips with various silver film thickness or various SiO2 film thickness were fabricated, and they were measured by atomic force microscopy (AFM) (Figure S2)
The optimal structure of a sensor-chip was found to be covered with 150 nm-thick silver film and
Summary
Surface plasmon field-enhanced fluorescence (SPF) has been known as one of the powerful tools in immunosensors [1,2]. This is because fluorescence is a sensitive technique compared with methods measuring absorbance and reflectivity, and further, enhanced fluorescence can improve the detection sensitivity compared with the general fluorescence method. In SPF, the surface plasmon resonance (SPR) field is utilized as an excited field for fluorescent molecules. Localized SPR has been mainly studied for surface-enhanced Raman scattering (SERS) spectroscopy [3,5], photochemical reaction [6,7], light harvesting [8], and photonics [9,10]
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