Surface-enhanced Raman spectroscopy (SERS) became in the last decades one of the most promising techniques for a large variety of applications due to the significant enhancement (10³- 10¹² order of magnitudes) of the Raman signal of the molecules adsorbed on noble metal nanostructured surfaces. The enormous Raman signal enhancement of a species adsorbed on a metallic surface is basically explained by considering the contribution of two enhancement mechansms: an electromagnetic (EM) mechanism associated with large local fields caused by electromagnetic resonances occurring near metal surface, and a charge transfer (CT) mechanism involving a scattering process associated with chemical interactions between molecules and the metal surface. Several research groups have exploited the benefit of the Raman enhancement and used even metal colloids (gold and silver), gold-metal island films or other substrate types based on silver-polydimethylsiloxane nanocomposites or ultrathin TiO₂ deposited on silver island films for the detection of pollutant molecules [1-3]. By taking into account the affinity of the sulphates, chlorates, amino and hydroxyl based pollutants to bind to the noble metals surface we propose in the present work to show the potential of some recently prepared nanocomposites based on titania aerogel and silver or gold colloidal particles to detect pollutant species adsorbed from an aqueous solution on the noble metal surfaces. Prior evidencing the detection efficiency of the composites for different pollutant molecules the existence of their porous-like structure was proved with the help of scanning electron microscopy (SEM) images.

References

1. H. Schmidt, N. B. Ha, J. Pfannkuche, H. Amann, H. D. Kronfeldt, G. Kowalewska, Marine Pollution Bulletin, 49, 229–234 (2004).

2. M. A. De Jesús, K. S. Giesfeldt, M. J. Sepaniak, J. Raman Spectrosc., 35, 895-904 (2004).

3. L. Bao, S. M. Mahurin, S. Dai, Anal. Chem., 76, 4531-4536 (2004).

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