Metasurface-Enhanced Raman Spectroscopy (mSERS) for Oriented Molecular Sensing

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a widely used sensing technique for ultrasensitivity chemical sensing, biomedical detection, and environmental analysis. Because SERS signal is proportional to the fourth power of the local electric field, several SERS applications have focused on the design of plasmonic nanogaps to take advantage of the extremely strong near-field enhancement that results from plasmonic coupling, but few designs have focused on how SERS detection is affected by molecular orientation within these nanogaps. Here, we demonstrate a nanoparticle-on-metal metasurface designed for near-perfect optical absorption as a platform for Raman detection of highly oriented molecular analytes, including two-dimensional materials and aromatic molecules. This metasurface platform overcomes challenges in nanoparticle aggregation, which commonly leads to low or fluctuating Raman signals in other colloidal nanoparticle platforms. Our metasurface-enhanced Raman spectroscopy (mSERS) platform is based on a colloidal Langmuir–Schaefer deposition, with up to 32% surface coverage density of nanogaps across an entire sensor chip. In this work, we perform both simulations of the local electric field and experimental characterization of the mSERS signal obtained for oriented molecular layers. We then demonstrate this mSERS platform for the quantitative detection of the drinking-water toxin polybrominated diphenyl ether (BDE-15), with a limit of detection of 0.25 μM under 530 μW excitation. This detection limit is comparable to other SERS-based sensors operating at laser powers over 3 orders of magnitude higher, indicating the promise of our mSERS platform for nondestructive and low-level analyte detection.

Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

“…These results vigorously validate that the plasmonic nanogap mode enhances the absorption of InSe and the 800 nm excitation wavelength can achieve the effective exciton–photon interaction required for optimal excitation of OP excitons. For a system with a specific resonance wavelength, resonant excitation can yield the best optical performance, − demonstrated in plasmonic Raman enhancement , and second-harmonic emission. − The increased local density of states in the plasmonic nanocavity results in the suppression of the nonradiative recombination and the shortening of the spontaneous radiative lifetime of the dielectric layer via the Purcell effect, − which has also been applied to upconversion emission , and quantum dot lasing . The time-resolved photoluminescence (TRPL) is measured to obtain the lifetimes of InSe in and off cavity and analyzed through biexponential fitting (Supplementary Figure 7).…”

Combinatorial Approach to Find Nanoparticle Assemblies with Maximum Surface-Enhanced Raman Scattering

“…Thus, we believe that the corners of the top AuNC play a significant role in creating these intense electric fields. 60 Moreover, the hot spot area, where strong electric fields are concentrated, is much larger for AuNC@AuNC than for other CS nanoassemblies (Figure S13). The electric fields are not uniform, even at the flat interface between the core and side satellite AuNCs in AuNC 90 @AuNC 60 .…”

Stacking‐order Reversed Multilayers of ZIF‐8 and Silver Nanoparticles for the SERS Detection of Organic Dye Species

“…Surface-enhanced Raman scattering techniques have been developed as a highly powerful spectro-analytical approach for inherent fingerprinting identification, trace-level sensitivity, and nondestructive detection. [1][2][3] The SERS is a valuable approach for analyzing trace compounds that have been widely used to detect chemical substances, biomolecules, and environmental contaminants, [4][5][6][7] due to its great sensitivity and excellent specificity for target analytes. [8][9][10] Generally, Raman scattering signals can be greatly amplified via the SERS techniques by several orders of magnitude, even allowing single-molecule detection.…”