Island films

Zeisel D, Deckert V, Zenobi R and Vo-Dinh T 1998 Near-field surface-enhanced Raman spectroscopy of dye molecules adsorbed on silver island films Chem. Phys. Lett. 283 381... 

The first SERS experiments were performed with electrochemically roughened electrodes and metal colloids, and many other types of suitable SERS substrates are known - e.g. metal island films, metal films over nanoparticles (see Fig. 4.58, below) or rough substrates, gratings, and sputter-deposited metal particles. 

Metal island films form spontaneously during slow evaporation of the metal on to supports with low adhesion. The metal islands can produce the surface-enhancement required for Raman characterization of the surface of the support. 

Figure 2.9 Spectra of a single adenine nanocrystal, (a) TERS spectrum, (b) ordinal SERS spectrum, and (c) ordinary near-infrared (NIR) Raman spectra. For the SERS measurement, a silver island film was used. For the NIR Raman measurement, i thick sample of adenine was used with a 1 h exposure.

The requirement for atomic-scale sites in the CT mechanism is thought to be due to the formation of adatom-adsorbate complexes. Such complexes require a coordination site on the adsorbate through which the strong interaction can occur, as was demonstrated by the controlled adsorption of isonicotinic acid and benzoic acid on thin island films of silver (see the work of Chen et ai, 1980). This clearly showed that SERS spectra could only be obtained from the molecules when coordinating sites were exposed to the Ag film. 

Figure 3. Various type of SERS active metallic nanostructures (a) metal-island films (b) metal-coated nanospheres (semi-nanoshells) (c) metal-coated random nanostructures and (d) polymer coatings embedded with metal nanoparticles. Inset An SEM image of silver-coated polystyrene spheres.

Vanduyne R.P., Hulteen J.C., Treichel D.A., Atomic-force microscopy and surface-enhanced Raman-spectroscopy. 1. Ag island films and Ag film over polymer nanosphere surfaces supported on glass, J. Chem. Phys. 1993 99 2101-211. 

A number of promising metal structures for fluorescence signal enhancement have been proposed silver island films (SIFs) that provide about 5-15-fold enhancement [89], fractal-like structures that resulted in stronger enhancements at specific hot spots [90-92], and SIFs deposited on silver or gold films with about 50-fold enhancement [93, 94], Recently, it was found that strong enhancement on a gold film based plasmonic platform may change even the shape of the emission spectrum [95],... 

Lakowicz JR, Shen Y, D Auria S, Malicka J, Fang J, Gryczynski Z, Gryczynski I (2002) Radiative decay engineering 2. Effects of silver island films on fluorescence intensity, lifetimes, and resonance energy transfer. Anal Biochem 301 261-277... 

TERS experiments were performed to study the bacterial cell surface. Biju et al. combined silver island films on glass coverslips with an AFM to investigate the effect of electron-acceptor limitation on the outer cell membrane of Shewanella one.ide.nsis [103]. 

Figure 16.20. Micro-SERS spectra of FA films cast from solutions at (a) pH 5, (b) pH 8, and (c) pH 11 on 9-nm gold island films. Laser excitation at 785 nm and spectra were collected from different spots as marked on the optical image. Reprinted from Alvarez-Puebla et al. (2004).

Organophosphorus -compounds Supported copper-cuprous oxide island film mg L 1 [350, 351]... 

In order to investigate molecules adsorbed at the solid-liquid interface roughened electrode surfaces or metal colloids in solution (sols) are prepared. For investigations of the solid-gas or solid-vapour interface several methods are available to produce metal island films on SERS-active substrates. 

Metal films. A third, also very popular, substrate for SERS are vacuum-deposited island films, which are more stable than sols, but they are more difficult to prepare and require a vacuum deposition apparatus (Wood and Klein, 1979 Chen et al., 1979). If the substrate in the vacuum is not cooled the temperature increases metal atom mobility, causing nuclei to grow into islands, i. e. small clusters of 3 nm up to a few ten nm in diameter. Metal vapour deposited on a cold substrate (usually below 120 K) forms a rough film as a result of the reduced mobility of the metal atoms on the cold substrate (Liao et al., 1981 Meier et al., 1985 Vo-Dinh et al., 1986 Pettenkofer et al., 1987 Otto, 1988). 

Other SERS-active substrate techniques include mechanical polishing polycristalline silver (Vo-Dinh et al., 1988) or ion bombardment in vacuo (Wood and Zwemer, 1981 Davies et al., 1986). A chemical procedure to prepare silver island films using Tollen s reagent was developed by Ni and Cotton (1986) which turned out to be simple, rapid and highly reproducible. In addition, the surface roughness and hence the enhancement... 

Furthermore, it is possible to increase the sensitivity of the IR technique, and thus the probability of detecting transient surface species characterized by (very) low absorption coefficients (such as the intermediate species present during the first steps of the polymerization reaction on the Phillips catalyst) by exploiting the surface-enhanced infrared absorption (SEIRA) effect. It is known that molecules adsorbed on metal island films or particles exhibit 10-1000 times more intense infrared absorption than would be expected from conventional measurements without the metal (253-256). The possibility of performing SEIRA spectroscopy should therefore be expected to provide an opportunity to better investigate the nature of the intermediate species, not only for ethene polymerization on Cr(II)/ Si02, but for other reactions on solid catalysts. 

Figure 1.3. (A) Photographs of silver island films (SIFs) deposited onto glass and plastic supports. (B) Normalized absorbance of zinc, copper, gold and silver nanostructured particles on a glass support. Atomic force microscope images of SIFs on (C) glass (D) plastic support.

K. Aslan, Z. Leonenko, J. R. Lakowicz, and C. D. Geddes. Annealed silver-island films for applications in metal-enhanced fluorescence Interpretation in terms of radiating plasmons yourna/ of fluorescence, 2005, 15, 643-654. 

K. Aslan, S. N. Malyn, and C. D. Geddes. Angular-Dependent Metal-Enhanced Fluorescence from Silver Island Films Chemical physics letters, 2008,453, 222-228. 

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