Abstract
Surface-enhanced Raman spectroscopy (SERS) is advantageous over fluorescence for bioimaging due to ultra-narrow linewidth of the fingerprint spectrum and weak photo-bleaching effect. However, the existing SERS imaging speed lags far behind practical needs, mainly limited by Raman signals of SERS nanoprobes. In this work, we report ultrabright gap-enhanced Raman tags (GERTs) with strong electromagnetic hot spots from interior sub-nanometer gaps and external petal-like shell structures, larger immobilization surface area, and Raman cross section of reporter molecules. These GERTs reach a Raman enhancement factor beyond 5 × 109 and a detection sensitivity down to a single-nanoparticle level. We use a 370 μW laser to realize high-resolution cell imaging within 6 s and high-contrast (a signal-to-background ratio of 80) wide-area (3.2 × 2.8 cm2) sentinel lymph node imaging within 52 s. These nanoprobes offer a potential solution to overcome the current bottleneck in the field of SERS-based bioimaging.
Highlights
Surface-enhanced Raman spectroscopy (SERS) is advantageous over fluorescence for bioimaging due to ultra-narrow linewidth of the fingerprint spectrum and weak photo-bleaching effect
In a typical experiment of preparing P-gapenhanced Raman tags (GERTs), 22 nm uniform-sized Au cores were modified with 4-NBT molecules via Au−S bonds and were centrifuged to remove the excess amount of molecules, and the obtained 4-NBT modified Au cores were utilized as seeds for further growth of the Au shell
Transmission electron microscopy (TEM) images confirm that P-GERTs consist of a Au core-rough shell structure spaced by a uniform interior gap with a typical size of ~0.7 nm, which is determined by the thickness of the monolayer of embedded 4-NBT molecules[15,29]
Summary
Surface-enhanced Raman spectroscopy (SERS) is advantageous over fluorescence for bioimaging due to ultra-narrow linewidth of the fingerprint spectrum and weak photo-bleaching effect. We report ultrabright gapenhanced Raman tags (GERTs) with strong electromagnetic hot spots from interior subnanometer gaps and external petal-like shell structures, larger immobilization surface area, and Raman cross section of reporter molecules These GERTs reach a Raman enhancement factor beyond 5 × 109 and a detection sensitivity down to a single-nanoparticle level. By utilization of strong electromagnetic hot spots from interior sub-nanometer gaps and external petal-like shell structures, a larger surface area for molecular immobilization, and a larger Raman cross section of reporter molecules, these sub-100 nm sized P-GERTs show two orders of magnitude stronger Raman signals than S-GERTs. P-GERTs can reach a Raman enhancement factor (EF) beyond 5 × 109 and a detection sensitivity down to a single-NP level. These P-GERTs offer a potential solution to overcome the current bottleneck in the field of SERS-based bioimaging
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