Dealloyed Intra-Nanogap Particles with Highly Robust, Quantifiable Surface-Enhanced Raman Scattering Signals for Biosensing and Bioimaging Applications

Abstract

Uniformly controlling a large number of metal nanostructures with a plasmonically enhanced signal to generate quantitative optical signals and the widespread use of these structures for surface-enhanced Raman scattering (SERS)-based biosensing and bioimaging applications are of paramount importance but are extremely challenging. Here, we report a highly controllable, facile selective-interdiffusive dealloying chemistry for synthesizing the dealloyed intra-nanogap particles (DIPs) with a ∼2 nm intragap in a high yield (∼95%) without the need for an interlayer. The SERS signals from DIPs are highly quantitative and polarization-independent with polarized laser sources. Remarkably, all the analyzed particles displayed the SERS enhancement factors (EFs) of ≥1.1 × 108 with a very narrow distribution of EFs. Finally, we show that DIPs can be used as ultrasensitive SERS-based DNA detection probes for detecting 10 aM to 1 pM target concentrations and highly robust, quantitative real-time cell imaging probes for long-term imaging with low laser power and short exposure time.

Plasmonic Nanogaps: From Fabrications to Optical Applications

“…One of the promising applications is using nanogap structures as the substrate for the SERS, and SERS has been used from single‐molecule detection to multiplexed target detection applications . SERS is the amplified Raman scattering by molecules adsorbed on metal surfaces, and it is widely believed that EM and chemical enhancement mechanisms that are based on the excitation of localized surface plasmons and the formation of charge‐transfer complexes, respectively, are responsible for the SERS .…”

“…Moreover, the enhanced EM field strength in the gap between the two metal nanostructures is a powerful candidate for a plasmonic sensor . For example, Kubo and Fujikawa prepared a Au double nanopillar (DNP) array for LSPR‐based refractive index (RI) sensing .…”

“…These observed results with the nanogap substrate show great potential for the development of a sensitive SERS biosensing platform. More recently, Nam and co‐workers reported that synthesizing the dealloyed intra‐nanogap particles (DIPs) with an ≈2 nm intragap in a high yield (≈95%) without the need for an interlayer . Owing to the strong EM field generated in the interior nanogap by strong plasmonic coupling between the core and the shell, an ultrasensitive DNA detection assay with DIPs for 10 × 10 −18 –1 × 10 −12 m target concentrations were clearly discernible with the SERS signals from DNA‐modified DIPs.…”

“…The subwavelength “hot spots” with highly confined energy are easily generated in the gaps, resulting in the enhancement of EM fields by orders of magnitude. This intriguing capability was essential to enable applications in surface enhanced spectroscopy, sensing, imaging, nonlinear optics, optical trapping, and metamaterials . In view of the remarkable advantages and broad application prospects, tremendous efforts have been devoted to fabricate various nanogaps.…”

Particle‐in‐a‐Frame Nanostructures with Interior Nanogaps

“…[11] Furthermore,u nlike solid nanostructures,a ggregating Au NFs was ineffective for the enhancement of their plasmonic function owing to the trade-off between the interior EM field and interparticle plasmon field coupling. [4,[18][19][20] However,a lmost reported nanostructures with interior nanogaps are enclosed hollow nanostructures.A ccordingly,t ofully harness the structural benefits of NFs in plasmonic applications,itishighly desirable to devise Au NFs with small interior nanogaps. [4,[18][19][20] However,a lmost reported nanostructures with interior nanogaps are enclosed hollow nanostructures.A ccordingly,t ofully harness the structural benefits of NFs in plasmonic applications,itishighly desirable to devise Au NFs with small interior nanogaps.…”