Raman Enhancement Factor of a Single Tunable Nanoplasmonic Resonator

Abstract

We have developed a novel technique to precisely determine the Raman enhancement factor in single nanoplasmonic resonators (TNPRs). TNPRs are lithographically defined metallodielectric nanoparticles composed of two silver disks stacked vertically, separated by a silica layer. At resonance, the local electromagnetic fields are enhanced at the TNPR surface, making it an ideal surface-enhanced Raman scattering (SERS) active substrate. The ability to control the dimensions of the metallic and dielectric layers offers the unique advantage of fine-tuning the plasmon resonance frequency to maximize the enhancement of the Raman signal. Furthermore, by selective shielding of the outer surface of the metallic structure, the efficiency can be further enhanced by guiding the molecular assembly to the locations that exhibit strong electromagnetic fields. We experimentally demonstrate SERS enhancement factors of (6.1+/-0.3)x10(10), with the highest enhancement factor being achieved by using an individual nanoparticle. By using nanofabrication techniques, we eliminate the issues such as large size variations, cluster aggregation, and interparticle effects common in preparing SERS substrates using conventional chemical synthesis or batch fabrication methods. TNPRs produce very controllable and repeatable SERS signals at the desired locations and, thus, make an ideal candidate for device integration.

Numerical Study of Optical Properties of Ag/SiO<SUB>2</SUB>/Ag Sandwich Nanobowties

“…[1][2][3][4][5][6][7][8][9][10] These nanoplasmonic resonators exhibit localfield enhancement and have been proven to be very unique for biomolecular labeling and detection, subwavelength lithography and nonlinear optical devices. [11][12][13][14][15] Especially the bowtie structure which is configured with two opposing tip-to-tip nanotriangles and separated by a nanogap, once exhibits remarkably large local E-field enhancement and strong scattering and has been widely studied in many fields such as optical antenna, optical waveguide, and SERS.…”

Individual nanostructured materials: fabrication and surface-enhanced Raman scattering

“…Nanoscale junctions, which can be as simple as nanoparticle dimers, have attracted much attention. There are a large number of reports on SERS studies of individual nanojunctions prepared with a variety of methods, such as drop casting, [58][59][60] molecular bonded dimerization, [61][62][63][64][65][66][67][68] solid phase synthesis, 69 polymer or ligand bridging, 70,71 lithography, 72,73 polymer encapsulation, 39,65,74,75 angle evaporation, 76 layer-bylayer (LBL) assembly, [77][78][79] galvanic reaction, 80 and vaporliquid-solid growth. Here, we will classify the nano-junctions into four categories based on the shapes of the joining nanomaterials: nanoparticle-nanoparticle junction, nanoparticle-nanowire junction, nanowire-nanowire junction, and junctions with metal thin films.…”

“…[81][82][83] For example, Zhang and co-workers reported a novel technique to prepare SERS substrates via vertically stacking silver nanodisks, which were separated by a silica layer using the layer-by-layer assembly. 79 Besides the fabrications of nanoparticle dimers, there are also considerable efforts in studying the polarization-dependent SERS enhancements on these nanoparticle dimers. Chen's group reported an investigation on the relationship between light polarization and SERS activity of silver nanoparticle dimers.…”

Highly‐Ordered, 3D Petal‐Like Array for Surface‐Enhanced Raman Scattering

“…Since this phenomenon was discovered about thirty years ago, a variety of SERS substrates have been extensively reported, such as rough metallic surfaces,20 metal colloidal solutions,21–23 fractal metal films,24, 25 and spherical or nonspherical nanoparticles 26–28. Benefiting from the advancement of nanotechnology and fabrication techniques, many other unconventional nanostructures like nanotips,29, 30 nanobowls,31, 33 nanowires,34, 35 nanorings,36 and nanocresent moons37, 38 have also been demonstrated for SERS applications recently.…”