Collapsed nanofingers by DNA functionalization as SERS platform for mercury ions sensing

Abstract

Surface-enhanced Raman spectroscopy (SERS) is known as a powerful technique to provide label-free analyses for chemical sensing. While the sensitivity of SERS is heavily dependent on the prepared SERS functional substrates, finding appropriate substrates is critical to achieve sufficient signal enhancement. Meanwhile, the capture of targets to such effective enhancing region becomes challenging especially for low concentration. Here, we report a coupled Au/D-NAs/Au gap plasmon platform that provides remarkable SERS enhancement and sensitivity for mercury ion sensing. Through nanoimprint lithography, large area of Au nanofingers can be fabricated with excellent uniformity and flexibility. These Au nanofingers can be further modified by DNA aptamers to construct Au/DNAs/Au gap plasmon nanostructures with well-defined gap sizes. Due to the subnanometer gap size, strong interaction between collapsed Au nanofingers can be induced to create extremely enhanced near-field with nanoscale mode volume. When Hg 2+ ions exist around the platform, they can specially bind to thymine (T) bases of DNA and form T-Hg 2+ -T pairs between adjacent single strand DNAs. As a result, DNAs that initially lie on the Au surface are forced to stand in rigid duplex-structures. This morphology change can be directly indicated by the ratio between adenine (A) and guanine (G) SERS signals to reveal the Hg 2+ concentration. Given the strong field enhancement as well as the close distance between DNA and hotspot, ultralow Hg 2+ concentration down to 10 À9 M is successfully detected. This work demonstrates a SERS platform with high selectivity and sensitivity, which exhibits significant potential for molecule sensing applications.

Plasmon-Enhanced Photocatalytic CO2 Reduction for Higher-Order Hydrocarbon Generation Using Plasmonic Nano-Finger Arrays

“…From our Lumerical FDTD simulation shown in Figure 2d, the hot spots of nano-fingers with light intensity are 10,000-fold larger than the incident light intensity are generated under 638 nm incident wavelength. Although the Au NPs seems to be squared-shaped nanostructures in the SEM images, we find that the shape of Au NPs is more like the hemisphere in our previous works [27,33] as mentioned in the material and method section and as shown in Figure S1a. In addition, the light intensity enhancement does not change significantly when using squared-shaped nanostructures in the modeling as shown in Figure S1b.…”

SERS-based microdevices for use as in vitro diagnostic biosensors

“…15 shows top-down photolithographic substrates that use different SERS platforms, such as plasmonic nanorods, nanocone, and nanoarray hybrid structures that have been introduced for signal enhancement. 198–230 3D bottom-up self-assembly nanostructures are described owing to facile preparation and cost-effectiveness. 231–251 Combinatory detection is used for synergetic enhancements.…”

Ultrafast Early Warning of Heart Attacks through Plasmon‐Enhanced Raman Spectroscopy using Collapsible Nanofingers and Machine Learning

“…[43][44][45][46] Using the standard methods, the antibody is connected to the surface of gold nanoparticle via covalent bond provided by thiols. [47][48][49][50][51][52] The receptors attached to the fingers could detect the target biomarker among thousands of complex components in the blood, as shown in Figure 3e,f. Moreover, the target biomarkers were fixed in the gap between fingers, which was the location with the maximum enhanced EM field due to gap-plasmon resonance created by closed nanofingers.…”