Showing papers on "Surface plasmon resonance published in 1986"

Surface‐enhanced Raman scattering (SERS) of nucleic acid components in silver sol: Adenine series

Abstract: Surface-enhanced Raman scattering (SERS) of adenine, adenosine, 2′-deoxyadenosine, 5′-dAMP, 5′-rAMP, 5′-rADP and 5′-rATP adsorbed on aqueous Ag sol has been investigated. A shift of the adenine ring breathing mode from 746 to 735 cm−1 with increasing adenine concentration is interpreted as reflecting the reorientation of adenine on the Ag surface. Such a shift is not observed for adenosine, 2′-deoxyadenosine and 5′-dAMP. SERS spectra of 5′-rAMP, 5′-rADP and 5′-rATP can be obtained either at neutral pH in the presence of pyridine or by lowering the pH of the Ag sol. The pH effect is discussed in terms of surface plasmon resonance theory.

Linear Pockels response of a monolayer Langmuir-Blodgett film

Abstract: Modulation of the output of a 0.633 ?m laser demonstrates the linear Pockels response of a monolayer Langmuir-Blodgett film. DC-induced shifts in the surface plasmon resonance in an attenuated total reflection configuration are observed. The nonlinear susceptibility ?(2) (-? ?, 0) of the monolayer is estimated.

Langmuir-Blodgett Films for Nonlinear Optics

Abstract: In recent years there has been considerable interest in media which display significant non-linear optical properties; the telecommunications industry may exploit chin films of such materials for signal processing applications. The Langmuir-Blodgett (LB) technique provides a means of depositing organic layers of a precisely defined thickness. Moreover, by alternating layers of different materials, supermolecular arrays may be fabricated in which there is no centrosymmetry, and therefore the second-order non-linearity of the constituent molecules may be exploited. An investigation of the properties of water-surface monolayers of a number of novel materials with potentially large non-linearities is described. Several of these compounds are shown to form high quality homogeneous or heterogeneous LB films. The optical and electrical properties of the layers are characterized by optical absorption spectroscopy, surface plasmon resonance, and measurements of capacitance, whilst their structure is examined by electron diffraction. Monolayers of a nitrostilbene dye are shown to exhibit: on exceptionally high degree of crystalline order. Data are also given for theoretical calculations of non-linear coefficients and for the relative efficiency of second harmonic generation from bulk samples of various materials. Studies of second harmonic generation from monolayer and alternate multilayer films are reported. Optical non-linearity in an alternating donor-acceptor: inverted donor-acceptor dye system is demonstrated for the first time; the results are analysed in terms of second harmonic surface susceptibilities, and the value of the second-order hyperpolarizability determined for the first bilayer is found to be much superior to that expected by the simple addition of the hyperpolarizabilities of the separate layers. Monolayers containing a mixture of hemicyanine and cadmium arachldate are found to give rise to second harmonic generation which is enhanced relative to that obtained from a pure monolayer of the dye. Corresponding changes in the absorption spectra of the layers can be observed. These findings may have important implications for improving the efficiencies of any non-linear optical device which utilises IB films.

Studies Of The Solid-Liquid Interface Via Laser Excited Surface Plasmon Spectroscopy

Abstract: The chemistry of the solid-liquid interface is of intense practical and theoretical interest, since a vast majority of heterogeneous reaction, adsorption, and epitaxy processes occur there. It is also among the most difficult of systems to study. One must have a probe which is extraordinarily sensitive, in order to observe the first few atomic layers, and very selective, in order to separate the effects of the surface associated species from those of the solvent or neat liquid in close proximity. To fulfill these requirements and to retain the advantages of optical spectroscopic techniques requires that the electric fields employed for excitation of interfacial molecules be spatially localized. When the solid component of the interface is one of the non-lossy metals, the above constraints can be satisfied by exciting a surface plasma resonance of a thin metallic film. Both theoretical and experimental work has shown that enhancement of Raman signals at Ag-liquid interfaces can be as high as 4 x 104. In addition the excitation of surface plasma resonances at metallic interfaces in the Kretschmann configuration has been shown to be extremely sensitive to adsorption of components from the ambient.4-7 In general the position of the plasmon resonance along the wavevector axis shifts and broadens upon adsorption or overcoating. Thus the exci-tation of surface plasma resonances at metal-liquid interfaces offers the possibility of simultaneously studying both adsorption-desorption kinetics, via observation of the reflectivity, and interfacial geometries, via enhanced signal vibrational spectroscopy of the adsorbates themselves.

Surface Plasmon — Surface Acoustic Wave Interactions on Thin Silver Films

Abstract: The high surface fields associated with surface plasmons (SP’s) are responsible for contributing to the strong enhancement observed for a number of non-linear optical phenomena such as Raman scattering by chemical adsorbates and second harmonic generation. We have demonstrated experimentally [1] that such an enhancement can also be observed when SP’s are used as an intermediate agent for Brillouin scattering from thermal equilibrium surface acoustic waves (SAW’s) of thin (450 A) silver films.