Highly confined, enhanced surface fluorescence imaging with two-dimensional silver nanoparticle sheets

Abstract

A method of obtaining highly confined, enhanced surface fluorescence imaging is proposed using two-dimensional (2D) silver nanoparticle (AgMy) sheets. This technique is based on the localized surface plasmon resonance excited homogeneously on a 2D silver nanoparticle sheet. The AgMy sheets are fabricated at the air–water interface by self-assembly and transferred onto hydrophobic glass substrates. These sheets can enhance the fluorescence only when the excitation wavelength overlaps with the plasmon resonance wavelength. To confirm the validity of this technique, two separate test experiments are performed. One is the epifluorescence microscope imaging of a quantum dot 2D sheet on the AgMy 2D sheet with a SiO2 spacer layer, where the fluorescence is maximized with the 20 nm SiO2 layer, determined by the Förster resonance energy transfer distances. The second experiment is the imaging of a single fluorescence bead with a total internal reflection fluorescent microscope. We confirmed that the AgMy sheet provides a 4-fold increase in fluorescence with a 160-nm spatial resolution at 30 ms/frame snapshot. The AgMy sheet will be a powerful tool for high sensitivity and high-resolution real time bioimaging at nanointerfaces.

Recent Progress on Plasmon-Enhanced Fluorescence

“…As a result, many researches have been performed to study the fluorescence enhancement on such NP substrate, particularly the relationship between the orientation and distance of the fluorescent molecules, as well as the environment effect, with respect to the substrate [49][50][51]. Due to the coupling effect between the emission of the fluorophore and the SPR band of the SNP array nanostructure, the intensity of PEF influenced by adjusting the distributed characteristics of the nanopartices arrays was also observed experimentally [52].…”

Characteristics of localized surface plasmons excited on mixed monolayers composed of self-assembled Ag and Au nanoparticles

“…24,25 The LSPR field excitation on metal particles, which contributes to fluorescence enhancement (radiative process), rapidly decays as the distance from the surface increases (i.e., the decay length changes according to the size of the metal particles). 27 In this study, we constructed a system suitable for fluorescence quenching with a 5-nm-thick SiO 2 spacer layer and investigated the quenching efficiency of 5-nm AgNPs and 10-nm AuNPs in the mixed monolayers. 26 Because these phenomena exhibit a trade-off relationship with a similar decay length, a separation distance that differs by a few nanometres could result in both enhancement and quenching.…”

Electromagnetically induced transparency of a plasmonic metamaterial light absorber based on multilayered metallic nanoparticle sheets

“…The diameter of the silver core was approximately 5 nm. Stable, close-packed two-dimensional sheet structures of AgMy were fabricated at an air–water interface via hydrophobic interactions in a Langmuir Blodgett (LB) trough (KSV NIMA small trough, Biolin Scientific, Sweden) at room temperature111213141534. The AgMy nanosheet was transferred via the Langmuir–Schaefer (LS) technique onto hexamethyldisilazane (HMDS)-treated quartz substrates or dodecane thiol-functionalized thermally evaporated gold or silver thin films (200-nm thick) on quartz.…”

“…The intensity, wavelength, and linewidth of the absorption peak were changed by the number of layers and resulted in a colour change of the sample if they were placed on a metal substrate. We previously reported the unique optical properties of multilayered metallic nanoparticle sheets up to 5 layers12 and proposed several new applications, such as imaging13, colorimetric sensing14, and fluorescence controlling using Ag-Au nanosheets15. However, we had not noticed the peak splitting due to the EIT effect for multilayered metallic nanoparticle sheets until we have tried the layer deposition more than 5 layers.…”