Highly Stable Polymer Coating on Silver Nanoparticles for Efficient Plasmonic Enhancement of Fluorescence

Abstract

Surface coating of plasmonic nanoparticles is of huge importance to suppress fluorescence quenching in plasmon-enhanced fluorescence sensing. Herein, a one-pot method for synthesizing polymer-coated silver nanoparticles was developed using a functional polymer conjugated with disulfide-containing anchoring groups. The disulfides played a crucial role in covalently bonding polymers to the surface of the silver nanoparticles. The covalent bond enabled the polymer layer to form a long-term stable coating on the silver nanoparticles. The polymer layer coated was adequately thin to efficiently achieve plasmonic enhancement of fluorescence and also thick enough to effectively suppress quenching of fluorescence, achieving a huge net enhancement of fluorescence. The polymer-coated plasmonic nanoparticles are a promising platform for demonstrating highly sensitive biosensing for medical diagnostics.

Ultrastable tip-enhanced hyperspectral optical nanoimaging for defect analysis of large-sized WS 2 layers

“…We believe that this could have also added to the lifetime of the stable enhancement in our experiments. One of the possible ways to protect plasmonic enhancement of silver-coated tips is the use of dielectric protective layers for silver tips as demonstrated in previous studies ( 22 , 52 ).…”

Tip-enhanced Raman spectroscopy with amplitude-controlled tapping-mode AFM

“…The effect of signal quenching is strong when a metallic tip is in physical contact to samples. Although there have been several successful reports on tip-enhanced photoluminescence/fluorescence measurements using the contact-mode AFM 34 – 36 , some researchers have also reported that it is better to have a few nanometers of the tip-sample separation for strong signal enhancement in photoluminescence or fluorescence 37 – 40 . Therefore, we expect that the small-amplitude tapping-mode AFM that we proposed would be an effective way not only for Raman measurements but also for photoluminescence or fluorescence measurements.…”

Ultrahigh Raman‐Fluorescence Dual‐Enhancement in Nanogaps of Silver‐Coated Gold Nanopetals

“…Consequently, fluorescence enhancements up to three orders of magnitude have been realized in solid assays created by the atomic-layer deposition, by which a thickness-tailorable spacer can be formed at the atomic level to achieve an optimal metalreporter distance for both modes (≈4 nm, slightly varying in spacers of different refractive indices [24,25] ). Approaches using colloidal NPs have proved much more challenging due to the fabrication challenges of wet chemistry (i.e., coating thickness, [24] random adsorption site of the reporter, [26] etc.).…”

“…Consequently, fluorescence enhancements up to three orders of magnitude have been realized in solid assays created by the atomic-layer deposition, by which a thickness-tailorable spacer can be formed at the atomic level to achieve an optimal metalreporter distance for both modes (≈4 nm, slightly varying in spacers of different refractive indices [24,25] ). Approaches using colloidal NPs have proved much more challenging due to the fabrication challenges of wet chemistry (i.e., coating thickness, [24] random adsorption site of the reporter, [26] etc.). [25] Typical methods for forming the spacer on colloidal NPs include polymer, [24] DNA, [13] SiO 2 , [27][28][29] CTAB, [30,31] and pluronic, [3] among others, most of which only result in single to double-digit fluorescence enhancement factors (EFs) and severe loss of SERS intensity due to the weakened EM field.…”