On the basis of different types of experiments, the authors develop implicitly the model of surface-enhanced Raman scattering (SERS) of adsorbates on metal surfaces. The long-range enhancement by resonances of the macroscopic laser and Stokes field is separated quantitatively from the metal electron-mediated resonance Raman effect. The latter mechanism proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to orbitals of the adsorbates. This model can account for the chemical specificity and vibrational selectivity of SERS and (partly) for the SERS specificity of the various metals.

https://iopscience.iop.org/article/10.1088/0953-8984/4/5/001/pdf

Surface-enhanced Raman scattering

Using surface plasmon resonance (SPR) spectroscopy in the Kretschmann configuration, we followed the self-assembly of organic ultrathin films which resulted from exposure of gold surfaces to solutions of CH3(CH2)n-1SH (n = 8, 12, 16, and 18) in ethanol and heptane We monitored film growth in situ and continuously for up to 72 h with an overall thickness resolution of <1 A Film dielectric constants, necessary for accurately calculating average film thicknesses from SPR spectra, were determined unambiguously for fully formed films by comparing spectra from organic films in different solvents In addition, we introduce a novel two-color SPR experiment with which we can obtain both film thickness and film dielectric constant without changing solvents We studied the chain length dependent and concentration dependent kinetics of film formation in ethanol and found that there are at least three distinct kinetics steps The kinetics of the first, most rapid, step and the third, slowest, step can be described w

In situ kinetics of self-assembly by surface plasmon resonance spectroscopy

The influence of colloid diameter on the surface plasmon resonance (SPR) response of a colloidal Au modified Au film is described. Adsorption of 30−59 nm diameter colloidal Au on the surface of a 4...

Surface plasmon resonance of au colloid-modified au films : particle size dependence

The simultaneous measurement of surface plasmon resonance (SPR) spectroscopy and surface-enhanced Raman scattering (SERS) on flat metallic surfaces is demonstrated on a relatively simple experimental setup based on the Kretschmann configuration. This setup requires only minor modifications to standard Raman microscopes, and we show that it can be applied successfully to the most common conditions of SPR spectroscopy, i.e., water-based solutions on gold films. Our results emphasize the peculiar properties of the Kretschmann configuration for spectroscopy in general and SERS measurements in particular, especially in terms of the asymmetry between excitation and collection requirements. The combination of simultaneous SPR-SERS spectroscopy opens up interesting prospects in analytical science to study, for example, reaction kinetics at surfaces under conditions which are already available in commercial SPR instruments.

Combining Surface Plasmon Resonance (SPR) Spectroscopy with Surface-Enhanced Raman Scattering (SERS)

This invention provides fundamental science and novel device architectures for surface plasmon (SP)-based, complementary metal oxide semiconductor (CMOS)-compatible, optical elements such as modulators, couplers, and switches. The primary focus of the work is on waveguides based on an ultra-long-range surface plasmon (ULRSP) waveguide mode recently discovered by our team. This mode exists at the metal-dielectric interfaces in a silicon-oxide-metal-silicon layer structure. While initial work focuses on noble metals to support the ULRSP, our analysis shows Si processing-compatible metals such as Cu and Al can also be used. Our modeling has also shown that variation in the thickness of the oxide layer can be used to give unprecedented propagation lengths in such structures. Electrically-induced free carrier modulation of the dielectric constant in the Si adjacent to the oxide can modulate the waveguide properties allowing novel Si-compatible electro-optic devices to be created. These waveguides function as the “wiring” in new classes of optical chips. This invention also provides integration of ULRSP waveguides and switches with other optical elements to create entirely new classes of hybrid optoelectronic technologies for defense applications. These range from chip-based chemical agent detection to extremely high performance processors and even all-optical computations.

Silicon-compatible surface plasmon optical elements

We describe the theory, design, and performance of a new surface‐plasmon‐polariton‐(SPP) assisted Raman scattering instrument that exploits the Kretschmann geometry. In contrast to previous methods, our device allows the entire SPP emission cone to be collected, thus optimizing the detected Raman intensity. This advantage makes surface Raman scattering from adsorbates on relatively smooth or single‐crystal silver films possible with routine optics and electronics in the rest of the system. We demonstrate the concept with data acquired from a monolayer of paranitrosodimethylanaline (pNDMA) on nearly smooth polycrystalline Ag and single‐crystal Ag(111) with air or liquid as the ambient medium.

T. E. Furtak

Papers

A device for performing surface‐plasmon‐polariton‐assisted Raman scattering from adsorbates on single‐crystal silver surfaces