Surface enhanced Raman spectroscopy using a single mode nanophotonic-plasmonic platform

Surface Enhanced Raman Spectroscopy (SERS) is a well-established technique for enhancing Raman signals. Recently photonic integrated circuits have been used, as an alternative to microscopy based excitation and collection, to probe SERS signals from external metallic nanoparticles. However, in order to develop quantitative on-chip SERS sensors, integration of dedicated nanoplasmonic antennas and waveguides is desirable. Here we bridge this gap by demonstrating for the first time the generation of SERS signals from integrated bowtie nanoantennas, excited and collected by a single mode waveguide, and rigorously quantify the enhancement process. The guided Raman power generated by a 4-Nitrothiophenol coated bowtie antenna shows an 8 x 10^6 enhancement compared to the free-space Raman scattering. An excellent correspondence is obtained between the theoretically predicted and observed absolute Raman power. This work paves the way towards fully integrated lab-on-a-chip systems where the single mode SERS-probe can be combined with other photonic, fluidic or biological functionalities.Comment: Submitted to Nature Photonic

Gold on graphene as a substrate for surface enhanced Raman scattering study

In this paper, we report our study on gold (Au) films with different thicknesses deposited on single layer graphene (SLG) as surface enhanced Raman scattering (SERS) substrates for the characterization of rhodamine (R6G) molecules. We find that an Au film with a thickness of ~7 nm deposited on SLG is an ideal substrate for SERS, giving the strongest Raman signals for the molecules and the weakest photoluminescence (PL) background. While Au films effectively enhance both the Raman and PL signals of molecules, SLG effectively quenches the PL signals from the Au film and molecules. The former is due to the electromagnetic mechanism involved while the latter is due to the strong resonance energy transfer from Au to SLG. Hence, the combination of Au films and SLG can be widely used in the characterization of low concentration molecules with relatively weak Raman signals.Comment: 11 pages, 4 figure

Enhancement factor distribution around a single SERS Hot-spot and its relation to Single Molecule detection

We provide the theoretical framework to understand the phenomenology and statistics of single-molecule (SM) signals arising in Surface-Enhanced Raman Scattering (SERS) under the presence of so-called electromagnetic hot-spots (HS's). We show that most characteristics of the SM-SERS phenomenon can be tracked down to the presence of tail-like (power law) distribution of enhancements and we propose a specific model for it. We analyze, in the light of this, the phenomenology of SM-SERS and show how the different experimental manifestations of the effect reported in the literature can be analyzed and understood under a unified ``universal'' framework with a minimum set of parameters.Comment: 13 pages, 4 figures, submitted to J. Chem. Phy

Applications of Surface-Enhanced Raman Scattering (SERS) for Biomolecules

Surface-enhanced Raman Scattering (SERS) is a new technique for studying the biomolecules. The SERS signals are found to be enhanced enormously over the normal Raman signals. A very lower concentration of the sample is required. Some experimental techniques of SERS have been discussed in the present communication

Surface Enhanced Raman Scattering of p-(Dimethylamino) Cinnamic Acid on Silver and Silver-Gold Alloids

Through this experimental work we describe assignments for the Raman and surface-enhanced Raman scattering (SERS) spectra (on Ag and Ag(x)-Au(1-x) colloids) of 4-(dimethylamino) cinnamic acid (DMACA). DMACA is a push-pull charge transfer molecule that exhibits strong SERS signals and can potentially be used as an anti-counterfeiting taggant. Evidence in the spectra indicates that the molecule adsorbs to the surface through the dimethyl amino group with the benzene ring tilted or standing up with respect to surface. The SERS spectra of DMACA and 4-(dimethylamino) cinnamaldehyde (DMAC) on Ag nanoparticles are identical. We conclude that DMAC is oxidized on the surface to form DMACA on the basis of observed carboxyl vibrations in the surface

Surface-enhanced Raman spectroscopy in 3D electrospun nanofiber mats coated with gold nanorods

Nanofibers functionalized by metal nanostructures and particles are exploited as effective flexible substrates for SERS analysis. Their complex three-dimensional structure may provide Raman signals enhanced by orders of magnitude compared to untextured surfaces. Understanding the origin of such improved performances is therefore very important for pushing nanofiber-based analytical technologies to their upper limit. Here we report on polymer nanofiber mats which can be exploited as substrates for enhancing the Raman spectra of adsorbed probe molecules. The increased surface area and the scattering of light in the nanofibrous system are individually analyzed as mechanisms to enhance Raman scattering. The deposition of gold nanorods on the fibers further amplifies Raman signals due to SERS. This study suggests that Raman signals can be finely tuned in intensity and effectively enhanced in nanofiber mats and arrays by properly tailoring the architecture, composition, and light-scattering properties of the complex networks of filaments.Comment: 29 pages, 9 figures, 1 Tabl

The effect of concentration on the Surface-Enhanced Raman Scattering of p-Aminothiophenol

The organic compound p-aminothiophenol (pATP, HS-Ph-NH2) has become very popular because it is often used for checking the enhancement capability of each new SERS substrate due to its very intense SERS spectra. SERS of pATP on silver electrode is significantly different from its ordinary Raman spectra and it is very dependent on the particular conditions of the SERS experiment. In this work the effect of adsorbate concentration on the potential dependent SERS spectra of pATP recorded on a silver electrode has been studied using NaClO4 as electrolyte. On the other hand, MS-CASPT2 have been performed in order to help the analysis of the experimental results by computing resonance Raman spectra of selected structural models of the metal−adsorbate surface complex. It is found that the spectra are dependent on adsorbate concentration and dominated by a resonant charge transfer (CT) mechanism, where the charge is always transferred from the adsorbate to the metal. The relative SERS enhancements are due to Franck−Condon factors related to the CT process, and there are not intensified bands through Herzberg−Teller contributions. Furthermore, the Raman signals of the SERS recorded at low concentration arise from at least three different molecular species: (i) pATP bonded to silver electrode through sulfur atom (Agn-S−-Ph-NH2); (ii) pATP bonded to silver electrode through both sulfur and nitrogen atoms (Agn-S−-PhNH2-Agm); (iii) The azo derivative p,p′-dimercaptoazobenzene (or its nitrene precursor).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech