High-temperature annealing of thick silver films (TSFs) deposited onto a smooth dielectric substrate leads to high-order self-organization of metal clusters on the film surface. A comparative atomic force microscopic (AFM) analysis of “as-deposited” and annealed TSFs (aTSFs) shows that uniform ellipsoidal roughness ∼41 × 25 nm in lateral cross section and ∼45 nm in height results after annealing. These metal clusters are mutually oriented so that the main lateral axes of the ellipsoids are nearly parallel. UV−visible data demonstrate a ∼300 nm hypsocromic shift of the bands corresponding to the collective surface plasmon modes. Additionally, a new (∼350 nm) band related to the normal component of the plasmon oscillations appears after annealing. This band was found to be strongly angle-dependent for p-polarized light. The aTSFs appeared extremely time- and organic solvent-stable versus as-deposited films. The aTSFs were found to be nondisturbing surface-enhanced Raman scattering (SERS)-active substrates in the application to studies of complexation of crown ether styryl dyes with metal ions. A pronounced SERS signal of the analyte rhodamine 6G was observed with aTSFs, even when the analyte was separated from the silver surface with five Langmuir−Blodgett monolayers of stearic acid. At the same time, depositing only a monolayer of stearic acid on the as-deposited film completely suppressed the SERS signal of the analyte. Finally, the self-assembling of Ag clusters on the surface of the aTSF, stimulated by the high-temperature annealing, results in the creation of a time- and organic solvent-stable SERS substrate with nanometer-scale quasi-periodical roughness, and this substrate exhibits an increased contribution of the electromagnetic component to the overall Raman enhancement.

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The interactions of three bis‐netropsins (bis‐Nts), which are potent catalytic inhibitors of DNA‐binding enzymes, with three double‐stranded oligonucleotides (OLIGs), which contain sites of different specific affinities for each bis‐Nt, were analyzed. Raman spectroscopy was performed for selective monitoring of modifications of the bis‐Nt or the OLIG structure upon bis‐Nt–DNA binding, and surface‐enhanced Raman scattering spectroscopy (SERS) was an additional tool for topology studies of ligand–DNA complexes. The spectral data showed conformational changes of both partners (bis‐Nt and OLIG) upon complexation. Structural variations of bis‐Nts appeared to be dependent on a bis‐Nt–OLIG binding constant and were found to be small in the specific DNA binding and highest for nonspecific binding of bis‐Nt with the corresponding OLIG. The conformational changes of the OLIGs were varied with a bis‐Nt–OLIG binding constant in the same manner. The bis‐Nts seemed to induce a perturbation in the OLIG's structure, as well as in the positions of their direct binding. These DNA structural modification effects may explain the inhibition of DNA‐binding enzymes in the variety of very distinct DNA–enzyme binding sites by bis‐Nts reported previously. © 2000 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 57: 272–281, 2000

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