We propose and fabricate a chip containing optical antennas for single molecule Surface-Enhanced Raman Spectroscopy (SMSERS). We verify that SMSERS is achieved using experiments with Rhodamine 6G (R6G) isotopologues.
We report on the experimental observation of strong coupling between localized and propagating surface plasmons when a gold nanoparticle array is in the vicinity of a gold film. The resonances exhibit an anticrossing behavior.
The 39K2 2 3Pi(g) state has been observed by perturbation facilitated infrared-infrared double resonance and two-photon excitations. The vibrational numbering of the 2 3Pi(g) levels was determined by resolved fluorescence into the bound levels as well as to the continuum of the a 3Sigma(u)+ state. The rotational assignment of the 2 3Pi(g) levels excited by two-photon transitions was determined from excitation frequencies and resolved fluorescence into the bound levels of the a 3Sigma(u) + and b 3Pi(u) states. Molecular constants obtained from these observed levels agree with theoretical constants.
We study a structure consisting of a gold disk array, an SiO2 spacer, and a gold film. We study the effect of spacer thickness on the anti-crossing between localized plasmons and surface plasmon polaritons.
Raman signals from molecules adsorbed on a noble metal surface are enhanced by many orders of magnitude due to the plasmon resonances of the substrate. Additionally, the enhanced spectra are modified compared to the spectra of neat molecules: many vibrational frequencies are shifted and relative intensities undergo significant changes upon attachment to the metal. With the goal of devising an effective scheme for separating the electromagnetic and chemical effects, we explore the origin of the Raman spectra modification of benzenethiol adsorbed on nanostructured gold surfaces. The spectral modifications are attributed to the frequency dependence of the electromagnetic enhancement and to the effect of chemical binding. The latter contribution can be reproduced computationally using molecule-metal cluster models. We present evidence that the effect of chemical binding is mostly due to changes in the electronic structure of the molecule rather than to the fixed orientation of molecules relative to the substrate.
Raman signals from molecules adsorbed on a noble metal surface are enhanced by many orders of magnitude due to the plasmon resonances of the substrate. Additionally, the enhanced spectra are modified compared to the spectra of neat molecules; many vibrational frequencies are shifted, and relative intensities undergo significant changes upon attachment to the metal. With the goal of devising an effective scheme for separating the electromagnetic and chemical effects, we explore the origin of the Raman spectra modification of benzenethiol adsorbed on nanostructured gold surfaces. The spectral modifications are attributed to the frequency dependence of the electromagnetic enhancement and to the effect of chemical binding. The latter contribution can be reproduced computationally using molecule−metal cluster models. We present evidence that the effect of chemical binding is mostly due to changes in the electronic structure of the molecule rather than to the fixed orientation of molecules relative to the substrate.
Enhancement factors (EFs) and angular emission profiles of SERS from molecules on nanoparticles can be modified and optimized by engineering their surrounding environments, namely other nanoparticles, and dielectric and metal films. This chapter discusses structures that are termed "double resonance" SERS substrates. It is known that when SERS is performed with nanoparticles having a single plasmon resonance, maximum signals will be obtained when the resonance is situated between the laser and Stokes frequencies. Next, the chapter presents results from studies that demonstrate SERS substrates with double resonances, to enable strong intensity enhancements to be achieved at both the laser and Stokes frequencies. The chapter discusses a technique for forming nanogaps. Nanoparticle dimers with nanoscale gaps present the opportunity for very high EFs, due to the substantial electromagnetic field enhancement occurring in these gaps. Finally, the chapter describes the observation of beamed Raman scattering using Yagi-Uda (YU) optical antennas.
We demonstrate that coupling between grating diffraction and localized surface plasmons in two-dimensional gold nanoparticle arrays in water leads to narrow near-infrared resonance peaks in measured far field extinction spectra. Good agreement is obtained between finite difference time domain (FDTD) calculations and experimental extinction spectra. The FDTD calculations predict that the gold nanoparticle arrays exhibit near-field electric field intensity (E2) enhancements approximately one order of magnitude greater than those of single isolated gold nanoparticles.
A two-dimensional array of gold optical antennas integrated with a one-dimensional array of gold strips and mirrors is introduced and fabricated. The experimental results show that this design achieves average surface-enhanced Raman scattering (SERS) enhancement factors as high as 1.2 × 1010, which is more than two orders of magnitude larger than optical antennas without the gold strips and gold mirror. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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